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How to Solder Capacitors in Parallel

In an electronic circuit, a capacitor serves to maintain a constant voltage. If the voltage across it drops, the capacitor supplies current, trying to keep the voltage up; if the voltage increases, the capacitor absorbs current in an effort to keep the voltage down. When space is limited, several small capacitors can do the job of a single large one. When capacitors are wired in parallel, their values are summed. For example, three 200-microfarad capacitors in parallel form a single 600 microfarad unit.

Things You'll Need

Flush cutters
Round-nose pliers
Temperature-controlled soldering iron
Solder
Waxed nylon lacing cord
Epoxy

Instructions

- 1
  Determine the polarity and working voltage of the capacitor before attempting any assembly. Electrolytic capacitors have the highest values and are polarized. One lead or both leads may be marked for positive or negative voltages. Connecting an electrolytic capacitor incorrectly will result in a loud bang and a spray of electrolyte and bits of metal. Do not exceed the working voltage printed on the capacitor. If the circuit carries 12 volts, be certain the capacitor is designed for a higher working voltage.
- 2
  Bundle axial-lead capacitors -- those with a lead on each end -- by tying them with waxed nylon cordage. Ensure that all the positive leads are at one end and all the negative leads are at the other before soldering. The bundle may be flat, with capacitors side by side, or it may be several rows deep. Beginning at one end, bend a lead over to contact the next capacitor's lead, then form it into a U shape. Clip off the excess and solder it to the lead. Take the second lead and repeat the process. Continue until all leads are soldered together neatly.
- 3
  Form large surface-mount capacitors by stacking. Surface mount (SMD) capacitors are rectangular and have no leads. Instead, they have a soldering surface on each end. Like electrolytic capacitors, they may be polarized and they have a maximum working voltage. To stack them, first solder one capacitor to the board. Solder both ends. Place another capacitor on top of the first one and solder it to the one underneath. These capacitors are small, so use a tool to hold it in place to avoid burning your finger.
- 4
  Exercise care when working with bundled capacitors. Even when circuit power is off, they can retain sufficient charge to deliver a painful shock. Bundles must be physically secured with waxed cord or epoxy to prevent movement that may short out other components. For safety, circuits should be designed with a high-value resistor of a megohm or more across the parallel capacitors, allowing the charge to bleed off slowly.

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