Printed Circuit Soldering Tips

Soldering is a common service procedure for wiring harness repair in automotive service, but modern cars and light trucks have numerous circuits that are very sensitive to heat and rough treatment. Printed circuits are common in dashboards and many sensor circuits like the fuel level sender. If you can’t replace, cracked or damaged boards can often be repaired with careful soldering. The key is to bridge the damaged portion with good, flexible conductor, rather than attempting to bridge the crack with solder alone. The more flexible the joint, the better. An excellent technique is to use the copper desoldering braid that’s used to desolder bad joints. It’s designed to wick up liquid solder by capillary action, a property that you can exploit when repairing a cracked board. Trim with scissors, and then lay the wick across the crack. Solder it to the board on both sides of the split, and let it absorb the solder. The result should be a solid conduction path that’s stronger than solder alone. And remember to put away the gun when soldering printed circuit boards; the heat is high enough to delaminate the copper traces and make the damage worse. Use a low-wattage pencil type iron, 40 watts or less, and don’t be afraid to grind or file the tip to get a shape that works well in tight places. Another useful tool from the electronics trade is the heat sink. Either store-bought or home made with an alligator clip and copper wire, heat sinks protect delicate components like integrated circuit “chips” or transistors from the heat of soldering. The key is to get the sink between the part you’re trying to protect, and the tip of your iron. Work quickly, and feed in a moderate amount of solder, and you should have a fast, reliable repair.