When designing circuits, it is essential to confirm the use and installation environments and then design within the rated performance range according to the capacitor catalog or product specification. ROQANG, a supplier of LCSC shared us precautions when designing circuits using surface mount aluminum electrolytic capacitors. Here are the detailed points to consider:
1. Aluminum Electrolytic Capacitor Use and Installation Environments:
Temperature and Frequency: Changes in temperature and frequency can affect the electrical characteristics of aluminum electrolytic capacitors. Consider these changes in your aluminum electrolytic capacitors circuit design.
- At high temperatures, leakage current increases.
- At low temperatures, the static capacitance decreases, and both the dissipation factor (tanδ) and impedance increase.
- At high frequencies, the static capacitance decreases, and both the dissipation factor (tanδ) and impedance increase.
- At low frequencies, the equivalent series resistance increases, leading to increased ripple current and potential overheating.
2. Temperature and Life Expectancy Calculations:
The life of a aluminum electrolytic capacitor is influenced by the operating temperature. Generally, for every 10°C decrease in temperature, the life expectancy approximately doubles. Use the aluminum electrolytic capacitor at a temperature as low as possible compared to the maximum guaranteed temperature.
Operating outside the guaranteed temperature range can lead to rapid performance degradation or even damage. The use temperature refers not only to the ambient and internal temperatures of the equipment but also to the temperature of the aluminum electrolytic capacitor influenced by heat radiation from heat-generating components (power semiconductors, resistors, etc.) and self-heating due to ripple current. Avoid installing heat-generating components directly behind the aluminum electrolytic capacitor.
The accelerated life formula is calculated as follows: L2 = L1* 2^(T1-T2)/10
- L1: Life at temperature T1 (in hours)
- L2: Life at temperature T2 (in hours)
- T1: The upper classification temperature (in °C)
- T2: The environmental temperature for life calculation plus the heat generated by the ripple current (in °C)
Do not exceed the specified product life. Otherwise, rapid aging, short circuits, or pressure relief valve operation, electrolyte leakage, and other damages may occur. Based on the environmental resistance of the sealing rubber, the expected product life should not exceed 15 years.
3. Aluminum Electrolytic Capacitor Load Conditions:
Applying the following loads to a aluminum electrolytic capacitor can lead to rapid performance degradation, short circuits, rapid heating, gas generation causing an increase in internal pressure, pressure relief valve operation, and even explosion or fire. Capacitor damage may also cause the ejection of internal flammable materials (electrolyte and component fixing materials, etc.).
Polarity: Aluminum electrolytic capacitors are polarized. Do not apply reverse or AC voltage. Ensure the correct orientation of the capacitor when installing it to avoid circuit short circuits or pressure relief valve damage. Confirm the polarity marking before use. In circuits with unstable or unclear polarity, consider using non-polar capacitors, but even these should not be used in AC circuits.
Applied Voltage: Do not apply overvoltage (voltage exceeding the rated voltage). When the peak value of the ripple voltage (AC component) overlaps with the DC voltage, use it below the rated voltage. Although there are provisions for surge voltages exceeding the rated voltage, these are under limited conditions and do not guarantee long-term use.
Ripple Current: Do not use excessive current (current exceeding the rated ripple current). Using too much current can sometimes cause internal overheating, reduced life, and pressure relief valve operation. Even when using within the allowable range of ripple current values, there is a risk of applying reverse voltage due to low DC bias. Use within the range that avoids reverse voltage.
Charging and Discharging: General capacitors should not be used in circuits with rapid charging and discharging. For capacitors that need to be used in circuits with repeated rapid charging and discharging, please contact us.
On-Off Circuits: Do not use this product in on-off circuits that are turned on and off more than 10,000 times a day. If you need to use it in such circuits, please inform us of the circuit conditions.
4. Series and Parallel Connections:
Parallel Connection: When capacitors are connected in parallel, it can sometimes disrupt the current balance between capacitors, leading to excessive current flowing through some capacitors. Ensure proper wiring to avoid excessive current.
Series Connection: When capacitors are connected in series, it can sometimes disrupt voltage balance, leading to overvoltage being applied. To avoid disrupting voltage balance, consider the leakage current factor and parallel a voltage-dividing resistor across each capacitor.
Capacitor Insulation: Capacitors should be electrically isolated between the following states:
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The outer casing and the negative and positive terminals, as well as the circuit.
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The self-standing type without connecting terminals (for strength reinforcement) and the positive and negative terminals, as well as the circuit.
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External Housing and Label: The external housing and label of the capacitor are for identification purposes only and do not guarantee electrical insulation.
5. Aluminum Electrolytic Capacitor Design of Installation Position:
Aluminum electrolytic capacitors use conductive electrolyte and combustible electrolytic paper as the main solvent. If the electrolyte leaks onto the printed circuit board, it can corrode the circuit, causing a short circuit and potentially smoke or fire. Please confirm the following for design:
