Electrolytic Capacitor Installation Considerations

Pre-Installation Preparation

Adequate preparation before installation is essential to ensure the reliable operation of capacitors.

Performance Check: For capacitors stored for more than two years, leakage current may increase. Pre-condition them by applying voltage through a ~1kΩ resistor to restore electrical characteristics. Carefully inspect the capacitor body—deformed, damaged, or poorly printed capacitors must not be used.

Parameter and Polarity Verification: Before installation, carefully verify the capacitance value and rated voltage to ensure they meet circuit design requirements. It is generally recommended that the actual operating voltage of the circuit be 20% to 50% lower than the capacitor’s rated voltage to enhance reliability. Also, confirm the polarity—reversing the positive and negative terminals may cause damage or even explosion.

 Installation and Soldering

Proper installation and soldering are critical to capacitor performance.

Mechanical Stress Prevention: Avoid applying excessive mechanical stress to the capacitor body. When using automatic insertion machines, adjust the manipulator’s force. After soldering, never use the capacitor as a handle to move the circuit board, and prevent other components from impacting or squeezing the capacitor.

Soldering Process Control:

Soldering Iron: Keep temperature and time within the range specified in the product datasheet. Avoid direct contact between the soldering iron tip and the capacitor body.

Reflow Soldering: Strictly adhere to reflow soldering conditions. Note that infrared heating may cause uneven heat absorption due to differences in capacitor color and size.

Post-Soldering Handling: Do not tilt, twist, or topple the capacitor after soldering.

Layout and Safety

Proper layout and insulation prevent potential failures.

Explosion-Proof Vent Space: For aluminum electrolytic capacitors with explosion-proof vents, sufficient space must be reserved above the vent to ensure proper operation in case of abnormalities. Refer to the table below for recommended clearances:

Insulation and Heat Dissipation: The aluminum case of liquid aluminum electrolytic capacitors is typically not insulated from the internal negative terminal. During installation, ensure a safe distance between the capacitor body and other components’ metal terminals, traces, or enclosures. If necessary, add insulation sleeves or insulating tape to prevent short circuits. Additionally, keep capacitors away from heat-generating components to avoid accelerated drying of the electrolyte, which leads to capacitance loss and reduced lifespan.

Environmental and Safety Standards

Environmental factors and operational guidelines are equally important.

Environmental Requirements: Avoid storing capacitors in high-temperature, high-humidity (e.g., >35°C, >75% RH), or environments with harmful gases (e.g., hydrogen sulfide, chlorine). After soldering or cleaning, if circuit board cleaning is required, avoid using halogen-based (may cause corrosion), alkaline-based (corrodes aluminum case), terpene-based, petroleum-based, xylene (causes rubber aging), or acetone (removes markings) solvents. Ensure thorough drying after cleaning to prevent residual moisture.

Safety Operations:

Discharge Handling: Even after discharging a previously energized capacitor, a “recovery voltage” may reappear across the terminals. Before re-installation, discharge the capacitor completely using a ~1kΩ resistor.

No Reuse: Do not reuse capacitors that have already been installed and energized in equipment (except for those removed for performance testing).

 Summary

In summary, the installation of electrolytic capacitors is a meticulous process that requires strict control from preparation to completion. Proper installation not only maximizes performance but also ensures the stable operation of the entire device.