A low temperature aluminum electrolytic capacitor is a capacitor specifically designed to maintain stable capacitance, acceptable ESR (Equivalent Series Resistance), and reliable startup performance in extreme cold environments, typically from -40°C to -65°C. Unlike standard aluminum electrolytic capacitors, low-temperature versions use specially formulated electrolytes that remain conductive at low temperatures, preventing severe capacitance loss and excessive ESR increase. These capacitors are commonly used in military electronics, railway auxiliary power systems, radar equipment, outdoor EV charging stations, and industrial power supplies operating in harsh climates.

Why this matters:
In extreme cold, capacitor performance often determines whether a power system can start successfully.

Why Do Standard Aluminum Electrolytic Capacitors Fail in Low Temperature Environments?

The performance degradation at low temperature is mainly caused by changes in the electrolyte.

1. Increased Electrolyte Viscosity

At low temperatures, the electrolyte becomes thicker, slowing down ion movement.

2. Reduced Ionic Conductivity

Ion transfer efficiency drops, directly affecting capacitance performance.

3. ESR Increase

Equivalent Series Resistance rises sharply, causing:

• Higher heat generation
• Lower efficiency
• Startup instability

4. Capacitance Drop

In extreme cases (-55°C or below), usable capacitance may drop to 30–40% of rated value.

👉 Conclusion:

The real limitation is not the capacitor structure, but electrolyte behavior under extreme cold.

What happens to capacitor ESR at low temperatures?

At low temperatures, the ESR (Equivalent Series Resistance) of aluminum electrolytic capacitors rises significantly because ion transfer inside the electrolyte slows down. Higher ESR causes increased power loss, more internal heating, poorer ripple current handling, and reduced startup efficiency. In power supplies, this can lead to unstable voltage during cold startup conditions.

👉In practical engineering, ESR increase is often a bigger problem than capacitance reduction, especially in high-voltage startup circuits.

Technical Approach to Improve Low Temperature Performance

Advanced low temperature aluminum electrolytic capacitors improve performance through two key innovations:

1. Low Temperature Electrolyte Formula

A specially designed electrolyte maintains higher ionic conductivity even at extremely low temperatures, preventing freezing and reducing capacitance loss.

2. Optimized Internal Electrode Structure

Improved contact stability between electrode foil and electrolyte ensures consistent performance under thermal stress.

Why Low Temperature Aluminum Electrolytic Capacitors Are Critical in Modern Power Systems

Modern power systems must operate in increasingly harsh environments, such as:

• Military communication systems in cold regions
• Radar systems in Arctic environments
• Railway auxiliary power systems in high-latitude areas
• Outdoor EV charging stations in winter
• Export power supplies for Russia, Canada, and Northern Europe

In all these cases, cold start reliability is a key requirement.

👉 A failure in capacitor performance can directly lead to:

• Startup delay
• System reset
• Complete power failure

Can aluminum electrolytic capacitors work at -55°C or -65°C?

Standard aluminum electrolytic capacitors are usually rated for -25°C to -40°C, and many experience severe performance degradation below those temperatures. However, specially designed low temperature aluminum electrolytic capacitors can operate reliably at -55°C or even -65°C by using optimized electrolyte formulations and internal structures.

At these temperatures, performance is mainly evaluated by:

• Capacitance retention
• ESR stability
• Cold startup reliability

A capacitor that maintains stable energy storage at -65°C is considered suitable for ultra-low-temperature power applications.

Why -65°C Capability Matters for Low Temperature Aluminum Electrolytic Capacitors

Although many power systems are designed for -40°C or -55°C operation, real-world environmental conditions are often far more demanding than laboratory specifications suggest. In military equipment, railway auxiliary power systems, outdoor EV charging stations, and exported power supplies for cold regions, components are frequently exposed to temperatures lower than expected.

Several real-world factors can push operating conditions beyond nominal design limits:

• Wind chill and airflow exposure can accelerate temperature drop around electronic enclosures.
• Overnight outdoor exposure may result in equipment experiencing temperatures well below daytime averages.
• High-latitude winter environments such as Russia, Canada, and Northern Europe often see prolonged periods below -40°C.
• Rapid thermal cycling between operating and standby conditions can place additional stress on capacitor performance.

For a low temperature aluminum electrolytic capacitor, operating close to its temperature limit may result in significant capacitance loss and a sharp ESR increase, reducing cold startup reliability.

👉This is why -65°C  capability matters.

A -65°C rated low temperature aluminum electrolytic capacitor provides additional engineering margin, allowing the system to maintain stable performance even when actual temperatures temporarily exceed design expectations.

Key benefits include:

Stable Cold Start Performance

Reliable capacitance retention and controlled ESR help ensure the power supply can deliver sufficient startup energy under extreme cold conditions.

Reduced System Failure Risk

Additional temperature margin minimizes unexpected failures caused by capacitance collapse or excessive internal resistance.

Longer Service Life in Harsh Environments

Operating below the capacitor’s maximum temperature limit helps reduce long-term stress, improving reliability and lifecycle performance.

Better Reliability for Critical Applications

In mission-critical systems such as military communication equipment, radar systems, railway power supplies, and outdoor charging infrastructure, additional low-temperature margin can significantly improve operational stability.

Engineering takeaway:
👉For systems expected to operate around -40°C to -55°C, selecting a -65°C low temperature aluminum electrolytic capacitor is not overengineering—it is a practical strategy for improving reliability and ensuring successful cold startup.

Can low temperature aluminum electrolytic capacitors replace film capacitors?

In some ultra-low-temperature applications, low temperature aluminum electrolytic capacitors can replace film capacitors, especially when engineers need higher capacitance density and smaller size.

Compared with film capacitors, aluminum electrolytic capacitors offer:

• Higher capacitance per volume
• Smaller footprint
• Lower system cost

The main challenge is maintaining stable performance at extremely low temperatures. Advanced low-temperature designs with optimized electrolytes can overcome this limitation and become viable alternatives for certain power systems.

What industries need low temperature aluminum electrolytic capacitors?

Low temperature aluminum electrolytic capacitors are commonly used in industries where reliable cold startup is critical.

Typical applications include:

• Military communication systems
• Radar equipment
• Railway auxiliary power supplies
• Outdoor EV charging stations
• Industrial power systems in cold regions
• Exported power electronics for Russia, Canada, and Northern Europe

These environments often require reliable operation between -40°C and -65°C.

FAQ

Q1: What happens to aluminum electrolytic capacitors at low temperature?

At low temperature, electrolyte viscosity increases, reducing ionic conductivity and causing ESR rise and capacitance loss.

Q2: What is the main limitation of capacitors in cold environments?

The main limitation is electrolyte performance degradation, not the capacitor structure itself.

Q3: Can aluminum electrolytic capacitors work at -55°C or lower?

Standard products struggle below -40°C, but optimized low temperature designs can operate reliably at -55°C and even -65°C.

Q4: Why choose a -65°C rated capacitor for -40°C applications?

Because it provides design margin, improving reliability and reducing failure risk in real-world conditions.

Conclusion

In extreme cold environments, capacitor reliability directly affects whether a power system can start and operate normally. As temperatures drop below -40°C, conventional capacitors often experience severe capacitance loss and rising ESR, increasing the risk of cold-start failure.

A low temperature aluminum electrolytic capacitor rated for -65°C provides greater engineering margin, helping ensure stable startup performance, improved reliability, and longer service life in harsh environments.

👉In extreme cold, real low-temperature performance matters more than room-temperature specifications.

The post Low Temperature Aluminum Electrolytic Capacitor for Extreme Cold Power Systems appeared first on Dongguan Xuanxuan Electrolytic Technology Co,.ltd.

The positive and negative lead-out electrodes and shells of aluminum electrolytic capacitors are made of high-purity aluminum. The medium of aluminum electrolytic capacitors is an aluminum oxide film formed on the surface of the positive electrode. The real negative electrode is the electrolyte, which is equivalent to an electrolytic cell when working, except that The anodized layer on the surface of the positive electrode has been formed, no electrochemical reaction occurs, and the current is theoretically zero. Due to the presence of impurities in the electrode and electrolyte, a small leakage current will be caused. From the perspective of phenomena, the common failure phenomena and failure modes of aluminum electrolytic capacitors include electrolyte drying up, pressure release device action, short circuit, open circuit (no capacitance), excessive leakage current, etc. Therefore, the factors that cause the failure of aluminum electrolytic capacitors can be divided into two parts: the characteristics of aluminum electrolytic capacitors and the application environment of aluminum electrolytic capacitors.

2 Characteristics of aluminum electrolytic capacitors

These include the selection and formula of manufacturing materials (electrode, electrolyte, sealing, etc.), manufacturing process, and technology (sealing method, heat dissipation technology, etc.).

2.1 Manufacturing materials

In a pure capacitor, no electrochemical reaction should occur, which is the essential difference between a capacitor and a battery. The electrochemical reaction in the battery can output or store electrical energy, while the electrochemical reaction not in the capacitor will store out electrical energy, but will also damage or even damage the capacitor.

Due to the presence of electrolytes in the aluminum electrolyte capacitor, once there are impurities in the electrode material, the primary battery effect will be formed, causing excessive leakage current and corrosion of the aluminum electrode. be high-purity aluminum, and it cannot be doped with any other impurities during the manufacturing process of aluminum electrolyte capacitors.

Since the medium of aluminum electrolyte capacitors is aluminum, once chloride ions exist in the electrolyte, the chloride ions will replace the oxygen ions in the aluminum and become aluminum chloride and dissolve in the electrolyte, thereby destroying the aluminum medium and causing an increase in leakage current to the extent that it cannot be used, it may even cause a short circuit.

In addition to electrode materials and electrolytes, sealing materials are also one of the keys to eliminating premature failure of aluminum electrolyte capacitors. If the sealing materials do not match, liquid leakage will occur, causing a period to aluminum electrolyte fail capacitors.
Strict material quality control can prevent early failure problems caused by manufacturing materials.

2.2 Manufacturing Process and technical aspects

In terms of the manufacturing process, the cutting of the electrode sheet, the riveting of the lead wire, the winding of the core package, the immersion or filling of the electrolyte, and the sealing process are not done well, which may cause the performance of the aluminum electrolytic capacitor to decline or fail.

In the process of cutting the electrode sheet and riveting the lead wire, it will cause certain damage to the aluminum oxide dielectric film. If the damage is too large, it cannot be repaired even through aging in time, resulting in early failure of excessive leakage current or breakdown short circuit; electrolysis Insufficient liquid entry or insufficient filling may cause the failure of aluminum electrolytic capacitors with insufficient capacitance or insufficient life; poor sealing of the aluminum electrolytic capacitor will cause the electrolyte to dry up prematurely and cause failure with insufficient life.

If the aluminum electrolytic capacitor is placed for some time and white salt stains or oil-like electrolytes appear near the lead wire or the seal, it means that the electrolyte has leaked due to poor sealing, and this type of electrolytic capacitor cannot be used.

Only when the above-mentioned manufacturing problems are all solved, the aluminum electrolytic capacitors shipped are qualified, and the early failure problems caused by manufacturing problems can be avoided.

3 Influence of application environment on the failure of aluminum electrolytic capacitors

If there is no problem with the quality of the electrolytic capacitor, the failure problem is in the application environment. The design and application environment of aluminum electrolytic capacitors mainly includes ambient temperature, heat dissipation method, voltage, and current parameters. For capacitor users, short circuits and open circuits are “catastrophic failures”, or “fatal failures”, which completely lose the function of capacitors. The other types of failure modes (that is, the failure caused by the second type of factors) are generally classified as “deterioration failure” or “depletion failure”.

The analysis of the influence of the application environment on the failure of aluminum electrolytic capacitors is as follows: the failure of aluminum electrolytic capacitors can be divided into overvoltage failure, exhaustion failure, open circuit, short circuit, pressure release device action, etc.

3.1 Overvoltage failure

In the application of aluminum electrolytic capacitors, various overvoltages may lead to failure modes such as performance degradation and breakdown.
The main cause of overvoltage is instantaneous overvoltage or surge voltage. If the rated voltage of the aluminum electrolytic capacitor is improperly selected (for example, the possible overvoltage is not considered) or the power supply environment is harsh, the overvoltage failure of aluminum electrolytic capacitors may occur.

3.2 Depletion failure

The so-called depletion failure is when the performance of aluminum electrolytic capacitors deteriorates due to the gradual drying of the electrolyte during use. Usually, the deterioration failure of aluminum electrolytic capacitors is generally defined as the end of life caused by the decline of one of the four key parameters of capacitance C, leakage current (IL), loss tangent (tan δ), and ESR increase beyond a certain range.

(1) The capacity decreases and the loss increases. Usually, the end of life of an electrolytic capacitor is judged based on the capacitance falling below 80% of the rated (initial value),lead to the failure of aluminum electrolytic capacitors. Due to the filling of electrolyte electrolytes in early aluminum electrolytic capacitors, the capacitance of aluminum electrolytic capacitors decreases slowly in the early stage of operation. The electrolyte gradually decreases as the working electrolyte continuously repairs the anodic oxide film damaged by impurities during the load process. In the later stage of use, due to the decrease of the electrolyte volatilization, it is difficult for the electrolyte with increased viscosity to fully contact the oxide film layer on the surface of the corroded rough aluminum foil, so that the effective area of the plate of the aluminum electrolytic capacitor begins to decrease rapidly. Small, that is, the capacity of the anode and cathode foils decreases rapidly, causing a sharp drop in capacitance. Therefore, it can be considered that the capacity reduction of the aluminum electrolytic capacitor is caused by the volatilization of the electrolyte,then lead to the failure of aluminum electrolytic capacitors. The most important reason for the volatilization of the electrolyte is the high-temperature environment or heat. The usually high-temperature environment is better understood.

The reason why the aluminum electrolytic capacitor heats up due to the application conditions is that the ripple (or pulsation) current flows through the aluminum electrolytic capacitor when it is working in rectification and filtering (including high-frequency rectification and filtering of switching power supply output) and power supply bypass of the power circuit. For electrolytic capacitors, the ESR of aluminum electrolytic capacitors generates losses and converts them into heat to generate heat.

When the electrolyte of an aluminum electrolytic capacitor evaporates more and the solution becomes thicker, the resistivity increases due to the increase of viscosity, which increases the equivalent series resistance of the working electrolyte, resulting in a significant increase in capacitor loss and loss angle,lead to the failure of aluminum electrolytic capacitors. For example, for an electrolytic capacitor with a working temperature of 105C, when the maximum core package temperature is higher than 125C, the viscosity of the electrolyte will increase sharply, and the ESR of the electrolyte will increase by nearly ten times. The increased equivalent series resistance will generate more heat, resulting in Faster volatilization of electrolyte. Such a cycle goes on and on, and the capacity of the aluminum electrolytic capacitor drops sharply, and may even cause an explosion.

In addition, if the viscosity of the working electrolyte increases too much at low temperatures, it will also cause increased loss and a sharp drop in capacitance. The low-temperature performance of the boric acid-ethylene glycol system working electrolyte is not good, and the viscosity is too high, resulting in a sharp increase in equivalent series resistance, increased loss, and reduced effective capacitance, which will cause aluminum electrolytic capacitors to fail when used in severe cold environments.

(2) Leakage current rises. Increased leakage current often causes aluminum electrolytic capacitors to fail.
The main reasons for excessive leakage current are: low level of empowerment process, insufficient density and firmness of the formed oxide film, backward chip opening process, serious damage and contamination of the oxide film, poor working electrolyte formula, low purity of raw materials, The chemical and electrochemical properties of the electrolyte are difficult to stabilize for a long time, the purity of the aluminum foil is not high, and the content of impurities is high.

Among them, the oxide film damage and serious contamination are the main reasons for the increased increasing leakage current. The flaws and defects of the oxide film itself, as well as the impurities such as chloride ions and sulfate ions in the electrolyte, damage the characteristics of the oxide film. Under the rated conditions, the oxygen generated by the electrolysis inside the aluminum electrolytic capacitor will repair the oxide film, that is, aluminum electrolysis The self-healing function of electrical appliances.

However, when the external positive voltage is increased to exceed the rated voltage (this situation is common in the circuit), the negative polar acid ions such as chloride ions and sulfate ions will accelerate the movement under the action of a strong electric field and dioxide Aluminum reacts, causing oxide film damage and serious contamination. At this time, the oxygen generated by the electrolyte in the aluminum electrolytic capacitor is not enough to completely repair the oxide film, increasing leakage current. The leakage current causes the oxide film on the contaminated part to decompose, resulting in a perforation. causing the current to increase further.

The impurity content of the aluminum foil is relatively high, and the size of the iron impurity particles is generally larger than the thickness of the anodized film, which makes the current easy to conduct. The existence of copper and silicon impurities affects the transformation of aluminum oxide to the crystalline structure, and copper and aluminum can also form micro-batteries in the electrolyte, which causes the aluminum foil to be corroded and damaged. In short, the presence of metal impurities in aluminum foil will increase the leakage current of aluminum electrolytic capacitors.

With the increase in use and storage time, the solution in the electrolyte is gradually consumed and volatilized, which increases the acid value of the solution and corrodes the oxide layer during storage. At the same time, due to the aging and dryness of the electrolyte, oxygen ions cannot be provided to repair the oxide film under the action of the electric field, thus losing the self-healing effect, the oxide film is damaged, and the leakage current increases.

If the anodic oxide film formed during the energization process is not dense and firm enough, the oxide film will be severely damaged in the subsequent cutting and riveting process. This kind of anodic oxide film is difficult to repair and perfect in the final aging process so during the use of the capacitor, local self-healing cannot repair the oxidation barrier, resulting in a large leakage current.

If the leakage current is too large, it will cause fatal failures such as the action and breakdown of the pressure release device (explosion-proof valve) of the aluminum electrolytic capacitor:
① When the leakage current is large, the rate of gas generated by electrolysis is faster, and the consumed electrolyte is used to repair the anodic oxide film, and the generated gas is stored in the capacitor shell. The longer the working time, the greater the leakage current, the more gas in the shell, and the higher the temperature. The air pressure difference inside and outside the metal shell of the capacitor will increase with the increase of the working voltage and working time. If the product is not well sealed, it will cause liquid leakage; if the seal is good, and there are no explosion-proof measures, the capacitor will explode when the air pressure increases to a certain extent. High-voltage large-capacity capacitors have a large leakage current and are more likely to explode.

② If the leakage current is too large, the insulation effect of the oxide film will be damaged, and the direct contact between the cathode and the anode will cause a short circuit breakdown. For example, when the riveting process is not good, the burrs on the lead-out chaff will seriously puncture the oxide film, the leakage current at the punctured part will be large, and the local overheating will cause thermal breakdown of the capacitor.

3.3 Causes of open circuits

Aluminum electrolytic capacitors may fail in an open circuit when they work in a high temperature or hot flash environment for a long time. The reason is that the anode lead-out foil is broken due to electrochemical corrosion. For high-voltage large-capacity capacitors, this failure mode is more common. In addition, if the anode lead-out foil and the anode foil are riveted, if they are not fully leveled, it will cause poor contact and intermittent open circuit of the capacitor.
When the working electrolyte with DMF (dimethylamine) as the solvent is used in the aluminum electrolytic capacitor, the DMF solution is an oxidizing agent, and its oxidation ability is stronger at high temperatures. After working for some time, the capacitor may be opened due to the oxide film formed on the riveting part of the anode lead-out foil and the welding piece. If an ultrasonic welding machine is used to connect the lead-out foil and the solder joint, this type of failure can be reduced.

4 Action of the pressure relief device

The electrolyte in the aluminum electrolytic capacitor is caused by the gas generated by internal high-temperature boiling or the gas generated by the electrochemical process, which causes the internal high pressure to cause the explosion of the electrolytic capacitor. To eliminate the explosion of aluminum electrolytic capacitors, aluminum electrolytic capacitors with a diameter of more than 8mm are equipped with pressure-release devices. These pressure-release devices operate before the air pressure inside the electrolytic capacitor reaches the dangerous pressure that has not yet caused the aluminum electrolytic capacitor to explode, and release the gas. With the action of the pressure relief device, the aluminum electrolytic capacitor is declared invalid. (1) The electrochemical process causes the pressure relief device to operate. The leakage current of aluminum electrolytic capacitors is a violent electrochemical process, which has been discussed in detail before and will not be repeated. The electrochemical process will generate gas, and the accumulation of these gases will cause the internal pressure of the aluminum electrolytic capacitor to rise, and finally reach the pressure release device to release the pressure,lead to the failure of aluminum electrolytic capacitors.

(2) Excessive temperature causes the pressure release device to operate. If the temperature of the aluminum electrolytic capacitor is too high, it may be that the ambient temperature is too high. For example, there are heating elements near the aluminum electrolytic capacitor or the entire electronic device is in a high-temperature environment.

The second reason why the aluminum electrolytic capacitor temperature is too high is that the core package temperature is too high. The root cause of excessive core package temperature is excessive ripple current flowing through aluminum electrolytic capacitors. Excessive ripple current produces an excessive loss in the ESR of the aluminum electrolytic capacitor and generates excessive heat, causing the electrolyte to boil to generate a large amount of gas, causing the internal pressure of the aluminum electrolytic capacitor and the pressure release device to operate when it rises sharply,lead to the failure of aluminum electrolytic capacitors.

(3) Action of the pressure release device caused by low ambient air pressure. If the aluminum electrolytic capacitor works in an application environment where the air pressure is too low such as high altitude or high altitude, the pressure release device will act prematurely, causing the aluminum electrolytic capacitor to fail prematurely. This is the limitation of the aluminum electrolytic capacitor to the application environment

5 Special failure modes

In high-voltage aluminum electrolytic capacitors, a special failure mode often occurs: burning. Aluminum electrolytic capacitors can cause both primary combustion and secondary combustion.

5.1 Combustion of Aluminum Electrolytic Capacitors

(1) Primary combustion mode. Primary combustion means that the electrolytic capacitor burns itself under certain conditions, which is the so-called “active combustion”.

In the formation of the fire source, the electrostatic energy accumulated in the capacitor can be connected to the spark discharge through the arc between the electrodes under certain conditions, and this spark is the “fire source”. The electrostatic energy gain is W=1/2CV2, where C is the electrostatic capacity and V is the charging voltage, which is proportional to the square of the charging voltage, so high voltage will greatly increase the amount of static electricity accumulated on the capacitor electrodes. Generally speaking, aluminum electrolytic capacitors for power input are more likely to cause internal spark discharge due to their high operating voltage, which will directly cause the overflowing electrolyte to burn. The working voltage of the aluminum electrolytic capacitor used for power output is relatively low, and it usually does not reach the electrostatic energy required for internal spark discharge, so primary combustion rarely occurs.

Combustible substances that can be burned: due to the presence of combustible substances such as electrolyte, isolation liner and hydrogen gas around the fire source, it is easy to catch fire and burn.

Oxygen supply: Due to the impact of heat generation and arcing between electrodes, the internal pressure of the capacitor will rise sharply until the safety valve opens. At this time, the combustibles will be ignited and continue to burn when they come into contact with the outside air. The larger the opening area of the safety valve, the more oxygen will be supplied and the more intense the combustion will be. Conversely, the opening area is so small that the combustibles cannot fly out to contact with the outside air, and the combustion will not continue at this time, and at most there will be a little burnt trace in the arcing part.

(2) Mode of secondary combustion. Secondary combustion means that the aluminum electrolytic capacitor is ignited by an external fire source, or the electrolyte is sprayed to a nearby high-energy area, causing a short circuit, arcing, and then a fire, lead to the failure of aluminum electrolytic capacitors,which is the so-called passive flammability.

Leakage or overflow of electrolyte: When the airtightness of the seal is poor or the safety valve is opened, the electrolyte will leak or overflow from the inside of the capacitor and circulate to the high-energy area (such as the high-energy part on the circuit board) , cause short circuit, flashover, cause the electrolyte to catch fire and then trigger the combustion of combustibles other than the electrolyte,lead to the failure of aluminum electrolytic capacitors.

External fire source: The combustible material around the capacitor burns to become a fire source. When the capacitor sealing material catches fire or the capacitor is heated by an external heat source and the safety valve opens, the electrolyte leaks and is ignited,lead to the failure of aluminum electrolytic capacitors.

(3) Instantaneous overheating. As mentioned earlier, usually the core temperature of aluminum electrolytic capacitors is reduced by 10C, and its life will be doubled. This core is located roughly in the center of the capacitor and is the hottest point inside the capacitor. However, when the capacitor heats up close to its maximum allowable temperature, for most types of capacitors, at 125C, the electrolyte will be squeezed out by the capacitor core package, causing the ESR of the capacitor to increase to 10 times the original. Under this effect, instantaneous over-temperature or over-current can permanently increase ESR, lead to the failure of aluminum electrolytic capacitors. In the application of high temperature and large ripple current, special attention should be paid to the possibility of instantaneous overtemperature, and special attention should be paid to the cooling of electrolytic capacitors.

6 Prevention of Failure of Aluminum Electrolytic Capacitors

6.1 Prevention of overvoltage failure of Aluminum Electrolytic Capacitors

Capacitors are easily broken down under overvoltage conditions,cause failure of aluminum electrolytic capacitors and instantaneous high voltages often appear in practical applications.

Figure 5.16 Schematic diagram of aluminum electrolytic capacitors suffering from surge voltage and transient overvoltage in rectification and filtering

In the figure, VR, VS, and .VT are rated voltage and surge voltage respectively. The transient high voltage test condition is 1000 cycles, 330s without load, 30s with load; VS is generally 110%~115% times VR.

It can be seen in the figure that due to the frequent transient overvoltage or surge voltage in the AC power grid, this transient overvoltage or surge voltage is transmitted to the electrolytic capacitor that completes the filtering function through the rectifier, resulting in overvoltage or transient overvoltage of the filter electrolytic capacitor ，cause failure of aluminum electrolytic capacitors.

The rectifier filter capacitor will cause instantaneous overvoltage or surge voltage of the filter capacitor due to the instantaneous overvoltage or surge voltage of the AC grid. Similar transient overvoltages or surge voltages also occur during power-up of circuits, especially in LC filters. For example, during the power-on process, because the filter inductor releases the stored energy into the filter capacitor, the filter capacitor will experience an instantaneous overvoltage,lead to the failure of aluminum electrolytic capacitors,as shown in Figure 5.17.

Figure 517 Transient overvoltage generated during switching action in LC filter
Figure 5.18 Figure 5.17 Overvoltage surge generated by the circuit
Figure 5.19 Using a negative source coefficient thermistor to prevent overvoltage in the circuit shown in Figure 5.17

This instantaneous overvoltage will produce “overshock” on the capacitor (Figure 5.18)，cause failure of aluminum electrolytic capacitors. Soft switching techniques, which can employ NTC thermistors, are effective against transient overvoltages (Figure 5.19).
The filter before the rectifier can filter out some high-speed transient high voltage, but not all.

6.2 Prevention of reverse polarity

If the positive and negative terminals of the aluminum electrolytic capacitor are connected incorrectly, it will only take a short time to cause damage to the capacitor,lead to the failure of aluminum electrolytic capacitors. Therefore, in order to avoid similar connection errors, the direction of the positive terminal of the capacitor will be rotated 90°, that is, the direction perpendicular to the axis of the two bolt terminals is the positive pole, and the direction along the axis of the two bolt terminals is the negative pole.

6.3 Protection against overheating

The current exceeding the rated value will cause the internal temperature of the capacitor to rise too high, and shorten its working life,lead to the failure of aluminum electrolytic capacitors.However, if the duration of the ripple current is short compared to the heat conduction time constant, it will generally not cause damage to the capacitor.

(1) Infer whether it is overheated by measuring the temperature of the aluminum electrolytic capacitor shell. The temperature of the core package inside the capacitor determines the working life of the aluminum electrolytic capacitor. A temperature sensor can be used to measure the internal temperature rise of the aluminum electrolytic capacitor during operation (the temperature sensor must directly contact the aluminum shell of the aluminum electrolytic capacitor).

Figure 5.20 Rules for preventing wrong polarity connection when aluminum electrolytic capacitors are placed horizontally

(2) Place the temperature sensor inside the core package of the aluminum electrolytic capacitor to detect whether it is overheated. For aluminum electrolytic capacitors connected by bolt ends, it can be measured by inserting a thermocouple inside the capacitor. In engineering practice, Figure 5.21 is relatively easy to implement, while Figure 5.22 can only be used in aluminum electrolytic capacitor product testing. The reason is that it is impossible for aluminum electrolytic capacitors connected by bolts to reserve a cavity for inserting a thermocouple in the sealed end cover or shell for measuring the temperature of the core package.

Figure 5.21 Temperature test points for aluminum electrolytic capacitors with various shapes
Figure 5.22 Test the temperature of the core package of an aluminum electrolytic capacitor with a bolted end connection by inserting a thermocouple inside the capacitor

(3) Estimation of core pack temperature under intermittent load. Aluminum electrolytic capacitors do not always work under continuous load conditions. For intermittent load conditions, the equivalent circuit of heat conduction shown in Figure 5.23 can be used for calculation.

In the figure, Rthhc is the thermal resistance from the aluminum electrolytic capacitor core package to the shell, Rthca is the thermal resistance from the aluminum electrolytic capacitor shell to the surrounding environment, Ch is the heat capacity of the aluminum electrolytic capacitor, and Cc is the heat capacity of the aluminum electrolytic capacitor shell.
The heat transfer parameters and ESR data for this example are available on the RIFA website.

Figure 5.23 Equivalent circuit of core package temperature heat conduction at intermittent load

For example, if PEG126KL427BM type aluminum electrolytic capacitor (40V/2700uF) is selected, the thermal resistance from the core package to the shell is 7.7°C/W, and the thermal resistance from the shell to the environment is 18°C/W. Natural cooling does not use forced air cooling) , The heat capacity of the core package is 21J/℃, and the heat capacity of the shell is 2.5J/℃.
Find the ripple current.
Working state: 20A, 5kHz within 5min.
Closed state: no current within 15min.
Cycle: 20min.
Ambient temperature: 93°C., without forced air cooling.
ESR=8.7mΩ.
Power loss: I2rmsResr = 3.5W (“working” state).
Based on the given heat conduction parameters and the calculated power loss, the core package temperature (Th and case temperature (Tc) can be calculated by computer simulation, as shown in Figure 5.24

Figure 5.24 Computer simulation results

From the above analysis, we can see that the limit of intermittent work is as follows
(1) The intermittent operation mode with a duty cycle of 25% can increase the ripple current by 95% compared to the value during continuous operation.
(2) When the core package temperature Th reaches 135°C, the maximum ripple current can still be applied
(3) Within 100h, the core package temperature Th≦45℃, can work at the maximum ripple current

The post Analysis and Prevention of Failure of Aluminum Electrolytic Capacitors appeared first on Dongguan Xuanxuan Electrolytic Technology Co,.ltd.

If the aluminum component does not reach the purity of 99.9%, based on cost considerations, it can still be used for cathode aluminum foil, because the purity of the cathode aluminum foil only needs to reach the level that it will not be corroded by the working electrolyte.

  According to the standard of aluminum foil for electrolytic capacitors GB/T 3615-2016, the recommended brand numbers of cathode aluminum foil are 1A90 (aluminum content﹥99.90%), 1070A (aluminum content﹥99.70%), 3003 (aluminum content﹥97%), for general products In other words, price and tensile strength are the key considerations. Aluminum foil with a purity of 97%-98.4% can be selected. As for products with higher requirements for life and charge and discharge frequency, it is necessary to have good corrosion effect and electrolyte stability. Consider the important point, you can choose aluminum foil with a purity of 99.9%.

  High specific capacitance cathode aluminum foil often uses alloy foil to improve the specific capacitance effect. For example, the aluminum foil of brand 3003 adds Mn (content 1%~1.5%) and Cu (content 0.05%~0.2%) to the aluminum material. Improve the strength of aluminum foil and improve the effect of corrosion specific capacitance.

🎇Specifications of electronic aluminum foil.

According to the standard GB/T 3615-2016 for aluminum foil for electrolytic capacitors, China specifies the brand, state and thickness specifications of electronic aluminum foil, as shown in Table 2-4.

Note: Ο represents the soft foil after annealing, H18, H22 represents the hard foil with different tensile strength.

The thickness of electronic aluminum foil for electrolytic capacitors is constantly changing with the miniaturization of capacitors, the demand for high specific capacitance and the improvement of corrosion technology. The thickness of anode aluminum foil is getting larger and the thickness of cathode aluminum foil is getting smaller and smaller. In the 1980s, the thickness of the anode aluminum foil was mostly 65 μm, 75 μm, 85 μm, 95 μm and 104 μm, and the thickness of the cathode aluminum foil was mostly 30 μm, 40 μm, 50 μm. After entering the 21st century, the thickness of anode aluminum foil has increased to 108μm, 112μm, 118μm, 120μm, or even 130μm, of which 120μm is the most used. The thickness of the cathode aluminum foil is reduced to 15μm and 20μm, of which 20μm and 50μm are used the most.

According to the adaptability, compatibility and versatility of corrosion and energizing equipment, the current width of electronic aluminum foil for electrolytic capacitors in the world is mostly 500±1mm.

The medium and high voltage anode aluminum foil adopts the DC tunnel corrosion method. The cubic texture degree is required to be greater than 90% for the anode foil with a thickness of 0.085～0.100mm, and the cubic texture degree is required to be greater than or equal to 95% for the anode foil with a thickness of 0.100～0.150mm. Therefore, the high and medium voltage anode foil must be a soft aluminum foil that has been annealed in a high temperature vacuum or inert atmosphere at about 600°C.

Low-voltage anode aluminum foil has both the corrosion method developed by DC-hole AC and the pure AC corrosion method. Therefore, the low-voltage anode aluminum foil can use either soft aluminum foil or hard aluminum foil.

 Most of the cathode aluminum foil is chemically corroded. Because the hard aluminum foil has a large number of rolled and broken grains and the grain boundary energy is large, it is very helpful to increase the corrosion rate and increase the specific capacitance of the corroded aluminum foil. Therefore, most of the cathode aluminum foil uses hard State aluminum foil.

🎇Mechanical indicators of aluminum foil.

The standard of aluminum foil for electrolytic capacitors only has indicators for the tensile properties of the cathode aluminum foil at room temperature, and there is no specification for the anode aluminum foil, which shall be determined by both parties through consultation. The Chinese aluminum standard for electrolytic capacitors GB/T 3615-2016 has two indicators for the tensile mechanical properties of cathode aluminum foil at room temperature, tensile strength and elongation. Specific indicators are shown in Table 2-5.

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🌟In addition to purity, high-purity aluminum foil with the same aluminum purity will also cause differences in capacitor performance due to different trace impurities. At the same time, it will also have a great impact on the corrosion of the aluminum foil and the energizing performance of the oxide film.

🌟The impurity in the aluminum foil of the electrolytic capacitor electrode focuses on iron, silicon, and copper.

⚫️The impurity copper element and aluminum element also belong to the face-centered cubic lattice configuration. Because of the similar compatibility principle, the degree of solid dissolution of copper as an impurity in aluminum is quite high.

At 548°C, the solubility of copper in aluminum can reach 6.65%; when the temperature drops to 302°C, the solubility of copper is still 0.45%, so there are almost no isolated copper grains in high-purity aluminum.

⚫️The solubility of impurity silicon in aluminum solid solution is 1.65% at the eutectic temperature of Al-Si (11.7% silicon) at 577°C. Although the solubility of silicon drops sharply as the temperature drops, silicon and aluminum can form alloys.

⚫️The amount of impurity iron in the solid solution of aluminum is extremely low, but if there is an appropriate amount of impurity silicon at the same time, the impurity iron that cannot be dissolved can combine with silicon and aluminum to form a ternary compound, which exists between the grain boundaries and is The grain boundary corrosion process is ruled out. When the silicon content is greater than iron, β-FeSiAl3 (or Fe2Si2Al9) phase is formed, and when the iron content is greater than silicon, α-Fe2SiAl8 (or Fe3Si2Al12) is formed.

Excessive iron impurities can also form dispersed iron aluminide binary compounds with aluminum. Typical representatives such as Fe3Al, FeAl, etc., appear in granular form, which adversely affects the performance of the energized aluminum oxide film.

If the particle size of the aluminum-iron intermetallic compound is larger than the thickness of the dielectric film, it is equivalent to setting up a conductive bridge that is easy to conduct leakage current in the highly insulating oxide layer, so the impact of impurity iron is the most serious.

🌟On the contrary, there is a trace amount of impurity magnesium in aluminum, which is easy to form the nucleation center MgAl2O4, which belongs to the spinel structure, which can promote the accelerated transformation of aluminum oxide to the crystalline state. The more nucleation centers in the aluminum material, the greater the number of tiny crystals. Obviously, this is beneficial to the manufacture of low-voltage aluminum foil, so sometimes there is the behavior of active doping of Mg.

The trace impurities in the aluminum foil and aluminum form a ZrAl3 compound, which can prevent the recrystallization process and help refine the recrystallized grains. Similarly, rare earth elements can also play a role in refining crystal grains.

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🤚🏾 Generally, the cathode foil manufacturing process is relatively simple, as long as the continuous casting and rolling paperboard is used, and then the foil rolling can be carried out. The anode foil manufacturing process is much more complicated, mainly to ensure that the aluminum foil can form a high cubic texture in the subsequent annealing process. The anode foil manufacturing process is shown in Figure 1-1.

⌛️ Each process is introduced as follows:

💡1. Casting and rolling ingot: The secondary refined aluminum ingot is melted in a heating furnace, and then mixed with the leftover material from the front roll or the trace metal elements that need special addition (such as copper, indium, lead, cerium, etc.). The molten liquid is generally Semi-continuous casting method (or stage casting method) is cast into ingots suitable for rolling. The size of the ingots varies with the scale of the factory and the ingot equipment used. Typical dimensions are 600~1000mm in width, 270~390mm in thickness, and 6000~ in length. 8000mm, mass 3~8t. Generally, water-cooled metal molds are similar to rectangular parallelepiped. Due to the large volume of cast ingots, slow heat dissipation, and low crystal nucleation rate, a relatively coarse-grained cast structure will be formed during the cooling process of the molten liquid.

💡2. Planing the surface of the ingot: the surface of the ingot is uneven, with casting coolant and oxide layer, and high melting point residual impurities are also segregated and concentrated on the surface 5-10mm before continuing to the next process. According to different requirements, this process can also be omitted.

💡3. Homogenization treatment: Heat the ingot to near the melting point temperature and keep it for 20~30h, so that the trace metal impurities are uniformly distributed in the ingot and the internal stress of the casting is eliminated.

💡4. High-temperature rolling processing: the homogenized ingot is directly hot-rolled on a rolling mill, using a large rolling rate, after more than ten times of repeated rolling, the thickness reaches 3~5mm and can be wound into The tube is called a rolled sheet. During the high-temperature rolling process of aluminum sheet, the temperature gradually drops to form a recrystallized structure, which destroys the cast structure and transforms it into a rolled structure. The size of the structure is 0.5mm.

💡5. Normal temperature rolling processing: the hot rolled coil is cooled to about 80℃ and then cold rolled at normal temperature. With a small rolling rate, after about 3 times of repeated rolling, its thickness is reduced to 0.5~0.6mm, and then it is wound. Become aluminum foil material. In order to facilitate the final annealing to obtain a high cubic texture degree, sometimes an intermediate annealing is required after normal temperature rolling. The annealing temperature is generally about 300 ℃. Its function is to eliminate the residual stress in the aluminum foil material on the one hand, and on the other hand to repair the part by the normal temperature roll High temperature rolling structure destroyed by rolling.

💡6. Finish rolling of aluminum foil: It can be achieved after several times of finishing rolling according to various thickness requirements, and the minimum thickness can reach 5μm.

💡7. Washing and winding: After the rolling is finished, the rolling grease should be cleaned to ensure that no impurities are left on the surface of the aluminum foil and winding.

💡8. Annealing treatment: The hardness of cold-rolled aluminum foil is increased, and it is generally inconvenient to use. It is often necessary to perform annealing treatment under inert gas or vacuum to make the finished foil in a low-hardness or soft-quality state. For high-pressure foils, a cubic texture degree of more than 95% is formed after annealing.

💡9. Cutting: In addition to cutting the uneven edges at both ends of the roll foil, it is generally necessary to cut the width into several finished foils of different specifications according to the product specifications, and then package them at the end. Its width mainly depends on the ability of corroding equipment and energizing equipment. At present, the width of electronic aluminum foil is generally 500mm.

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✨1. High specific capacitance：

Since the anode of the electrolytic capacitor is manufactured by electrochemical corrosion technology or powder sintered porous block technology, it has a very high effective specific surface area. Secondly, the electrochemical anodic oxidation method is used to form a high-dielectric constant metal oxide dielectric film, so its capacitance per unit volume (that is, specific capacitance) is very high.

For example, low-voltage large-capacity aluminum electrolytic capacitors and solid sintered tantalum electrolytic capacitors have specific capacitances of 1200μF/cm3 and 2400μF/cm3, respectively. Other types of capacitors, such as metallized film capacitors and low-voltage multilayer ceramic capacitors, generally do not exceed 2μF/cm3 and 200μF/cm3 in specific capacitance, which is very different from electrolytic capacitors.

The lower the working voltage of the electrolytic capacitor, the lower the oxide film forming voltage and the thinner the thickness of the oxide film dielectric, the higher the specific capacitance of the capacitor. In order to compare the specific capacitance of electrolytic capacitors under different working voltages more scientifically, the product of capacitance and voltage in a unit volume is generally used to express it, called the specific CV product, and the unit is μF·V/cm3. The specific CV products of low-voltage and large-capacity aluminum electrolytic capacitors and solid sintered tantalum electrolytic capacitors exceed 12000μF·V/cm3 and 24000μF·V/cm3, respectively. In contrast, the specific CV product of metallized film capacitors and low-voltage multilayer ceramic capacitors is close to 1000μF·V/cm3 and 4000μF·V/cm3, which is still far behind electrolytic capacitors.

✨2. Self-healing：

During the working process of the liquid electrolytic capacitor, since the anode of the capacitor is connected to the positive electrode of the power supply, the anions in the electrolyte will concentrate on the defects of the oxide film, so that the defects in the oxide film can be automatically repaired, so that the oxide film medium can be obtained at any time Reinforce and restore its proper insulation capacity without encountering continuous cumulative damage. Because of this characteristic of electrolytic capacitors, even if a local breakdown occurs during the operation of the capacitor, it can return to normal by itself. This performance is called the self-healing characteristics of electrolytic capacitors. Solid electrolytic capacitors also have self-healing characteristics, but the self-healing method is not used. The specific self-healing mechanism will be discussed in a follow-up article.

✨3. High working electric field strength：

For an aluminum electrolytic capacitor with a working voltage of 450V, the thickness of the oxide film is about 270nm, and the working electric field strength exceeds 600kV/mm; even a low working voltage electrolytic capacitor has a similar working field strength, which is about More than 30 times that of ceramic capacitors and 4 to 5 times that of organic film capacitors. Although the working field strength of the solid electrolyte tantalum electrolytic capacitor is slightly lower, it also has the same order of magnitude. It is precisely because the working field strength of an electrolytic capacitor is larger than that of any type of capacitor, its high specific capacitance is guaranteed.

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• Working principle of aluminum electrolytic capacitor

Aluminum electrolytic capacitor use the oxide film formed on the surface of the anode high-purity aluminum foil as the dielectric, and then the cathode aluminum foil, electrolyte, capacitor paper (electrolytic paper). The oxide film is formed by electrolytic oxidation (formation), is very thin, and has rectifying properties. In addition, by corroding high-purity aluminum foil to expand the effective surface area, a miniaturized and large-capacity capacitor is obtained. The structure of the actual capacitor is composed of anode foil and cathode foil, with electrolytic paper (two layers of foil and two layers of electrolytic paper) sandwiched between the two foils. The electrolytic paper impregnated with electrolyte is a non-solid aluminum electrolytic capacitor, which is used in electrolytic paper The solid electrolyte conductive polymer is aluminum solid

Electrolytic capacitor.

• Basic parameters of aluminum electrolytic capacitor

1. Capacity

According to the principle of aluminum electrolytic capacitor, the capacitance of the electrolytic capacitor is determined by the capacitance Ca of the anode foil and the capacitance Cc of the cathode foil in series

The result is the total capacity of the capacitor:

C = Ca×Cc/Ca＋Cc

The standard capacity tolerance is ± 20% (M), and precision capacitor such as tolerances of ± 10% (K) require special production.

The capacity of aluminum electrolytic capacitor will vary with the test temperature and frequency. Therefore, the standard conditions for capacitance testing are: 120Hz, 20 ° C.

2. Equivalent series resistance

The equivalent series resistance ESR is composed of the resistance of the electrolyte, electrode foil, and lead wires and the connection resistance between them. In the equivalent circuit, it is equivalent to

The capacity is connected in series:

ESR decreases with increasing temperature, and decreases with increasing frequency in the low frequency region. The ESR impedance value is listed in the product catalog or approval letter

About the measurement position during ESR measurement:

Lead type: The measurement position is the bottom of the lead terminal.

Chip type: The measurement position is the electrode part closest to the orifice of the resin plate.

3. Loss angle tangent (Tanδ)

In an equivalent circuit, the ratio of the equivalent series resistance ESR to the capacitive reactance 1 / ωC is called Tanδ. Tanδ = RESR / (l / ωC)

Among them: RESR = ESR (120Hz)

ω = 2 π f (f = 120Hz)

Tanδ increases with the increase of measurement frequency and increases with the decrease of measurement temperature.

4. 4. Leakage current

Since the dielectric is not ideally fully insulated, the electrolytic capacitor will generate a small DC current after the voltage is applied. This DC current is the leakage current.

The leakage current value is related to the applied voltage, charging time and the temperature of the capacitor. The increase in temperature and voltage will increase the leakage current.

5. Rated ripple current

The rated ripple current is the maximum AC current allowed to flow in the capacitor. Due to the power loss in the capacitor (ESR is present), the ripple current will cause the capacitor

There is a temperature rise inside. In order to make the capacitor work normally during the life cycle, each capacitor is specified with a rated ripple current at the rated operating temperature,

Thereby limiting its internal temperature rise. usually:

The maximum allowable temperature of the 85 ° C capacitor is 10 ° C, that is, the maximum allowable temperature of the core package is 95 ° C;

For 105 ° C products, the maximum allowable temperature rises to 5 ° C, and the maximum allowable temperature in the center of the core package can reach 110 °

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In order to meet the needs of patients for treatment in a timely manner and to the greatest extent, during the outbreak of Corona-19, the Chinese government urgently and quickly built some new hospitals, especially in the Wuhan area. The information of these new hospitals has been widely reported in the media. The mobile X-ray machine is configured as a key device in the newly built hospital.

A customer of Xuansn (CH) Electronics specializes in the manufacture of various X-ray equipment. We have been providing bolted aluminum electrolytic capacitors for the manufacture of mobile X-ray machines to our customers for many years. Each set of equipment will use 14 bolted aluminum electrolytic capacitors of this series.

Product performance of bolted aluminum electrolytic capacitors

High reliability and high ripple current capability
Fully welded structure to ensure reliable electrical contact
Comply with RoHS requirements
Rated voltage: 350 … 450 V DC
Surge voltage: 1.10 ∙ VR
Operating temperature range: -40 ºC… + 85 ºC
Rated capacitance (20 ºC, 120 Hz): 1000… 18000 μF
Capacity tolerance: ± 20% (M)

In addition to being used in X-ray scanners, this product can also be used in MRI (nuclear magnetic resonance imaging).

The post Xuansn (CH) aluminum electrolytic capacitors fully support Corona-19 appeared first on Dongguan Xuanxuan Electrolytic Technology Co,.ltd.

1. Aluminum electrolytic capacitor

Aluminum electrolytic capacitor is a liquid electrolytic capacitor. According to the state of the dielectric material, it is divided into liquid aluminum electrolytic capacitors and solid aluminum electrolytic capacitors.

Aluminum electrolytic capacitors have larger capacitance. Compared with non-polar capacitors, they have lower insulation resistance, larger leakage current and poor frequency characteristics. The capacity and loss will vary with the surrounding environment and time, especially when the temperature is too low or too high. Under high conditions, it will fail if it is not used for a long time. Therefore, aluminum electrolytic capacitors are mainly used in low-frequency and low-voltage circuits.

There are various specifications of aluminum electrolytic capacitors, and their shape varies according to the manufacturing process. Commonly used are angular aluminum electrolytic capacitors, bolt-type aluminum electrolytic capacitors, axial aluminum electrolytic capacitors and lead electrolytic capacitors.

2. Tantalum electrolytic capacitor

Tantalum electrolytic capacitors are capacitors made of metal tantalum as the positive electrode material. There are mainly solid button electrolytic capacitors and liquid tantalum electrolytic capacitors. Among them, solid tantalum electrolytic capacitors are divided into discrete tantalum electrolytic capacitors and chip tantalum electrolytic capacitors according to different installation forms.

Tantalum electrolytic capacitors have better temperature characteristics, frequency characteristics and reliability than aluminum electrolytic capacitors, especially low leakage current, good charge storage capacity, long life, and small errors, but they are expensive and usually used in high-precision electronic products.

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The aluminum electrolytic capacitor is made of an aluminum cylinder as a negative electrode, which is filled with a liquid electrolyte, and a capacitor made by inserting a curved aluminum ribbon as a positive electrode.

Among the electronic components used in the entire machine, capacitors are the most widely used and the largest in terms of volume, accounting for about 40% of the total electronic components used, while aluminum electrolytic capacitors also account for three major types of capacitors (electrolytic capacitors, ceramic capacitors, and organic film capacitors). More than 30%.

Aluminum electrolytic capacitors according to different classification criteria can be divided into liquid aluminum electrolytic capacitors, solid aluminum electrolytic capacitors, consumer aluminum electrolytic capacitors. Liquid aluminum electrolytic capacitors can be divided into three types: lead type, solder lug, solder pin type, and bolt type. Consumer aluminum electrolytic capacitors are mainly used in consumer markets such as televisions, stereos, monitors, computers and air conditioners. Industrial aluminum electrolytic capacitors are mainly used in industrial and communications power supplies, professional inverters, numerical control and servo systems, wind power generation and automotive industries. field.
Industry Technology Status Analysis

1, the number of industry patent applications

Judging from the trend of changes in the total number of patent applications for aluminum electrolytic capacitors in China, before 2005, China’s patented aluminum electrolytic capacitors had a relatively small number of patent applications and the growth rate was relatively slow. Aluminum electrolytic capacitor technology was still in its infancy; after 2005, aluminum electrolytic capacitors The technology has gradually entered a stage of rapid development. The number of new patent applications each year has increased to varying degrees. In particular, in 2015-2017, the number of patent applications for aluminum electrolytic capacitors in China exceeded 200, reaching 239, respectively, 234 Items and 236 items.

Exhibit 1: Change in Number of Patent Applications for Aluminum Electrolytic Capacitors in China, 1994-2017 (Unit: Item)

Source: Forward-looking Industry Research Institute

2, the number of public patent disclosure

Judging from the trend of changes in the total number of aluminum electrolytic capacitors in China, from 1998 to 2017, the number of publicly disclosed patents related to aluminum electrolytic capacitors in China showed a fluctuating upward trend. 2016 and 2017 reached their maximum values ​​in recent years with 268 items. As of the end of May 2018, the number of patents related to aluminum electrolytic capacitors in China has reached 181, and it is expected to exceed 300 in the year.

Note: The data for 2018 is from January to May.Note: The data for 2018 is from January to May.
Source: Forward-looking Industry Research Institute

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