Introduction: Repairing a Damaged Pad on a PCB
Pads are typically damaged when devices are removed from PCBs. I am going to show you a way to repair damaged SMT land/trace combinations. The traces you cut from the circuit frame library are joined to existing printed circuit board traces.This process is part of the IPC 7721 which are the recommended procedures for repairing printed circuit boards. This one is found in 4.2.1 (Trace) and 4.7.1 (Pad). A complete kit can be purchased with all of the materials or you can get complete training on this and other processes or you can follow along with this "how to".
The materials you will need include:
ESD-safe cutting surface
Step 1: Cleaning
Clean the damaged are with isopropyl alcohol and blow dry with canned or compressed air or damp dry with a lint free cloth.
Step 2: Remove the Damaged Pad
Carefully cut away with an Exacto knife the damaged pad.
Step 3: Clean Up the Area in Around the Pad
Remove any burned laminate from the area
Step 4: Remove Mask
Carefully remove solder mask from conductor using a dental pick
Step 5: Clean
Clean the area using isopropyl alcohol and dry via compressed or canned air or a lint free cloth.
Step 6: Tin the Conductor
Using the correct type of solder alloy tin the conductor area in place where the new conductor will be attached
Step 7: Sise Up and Select the Right Circuit Frame
Select the new conductor from the circuit frame. Cut out with sharp small knife.
Step 8: Tin the Replacement Pad/Conductor
Using the right alloy of solder, tin new conductor area that will be overlapping old trace (about 2-3 conductor widths). Mix epoxy. I generally like to mix only a little at a time as the pot life is only 45 minutes or so. Bond to the PCB. Cure in open air or in an oven to accelerate the process per the manufacturers directions.
Step 9: Solder the Replacement Pad/Trace to the Existing Conductor
Hold the replacement conductor in placewith Kapton™ tape. Create the lap joint using the right solder alloy.
Step 10: Clamp and Cure
Hold the replacement pad/trace in place until cured. Remove the clamp. Clean with isopropyl alcohol and inspect. I also like to perform a quick electrical continuity check at this point. In some cases I even envelope the edges of the replacement pad/trace with solder mask or epoxy and cure so that it has extra mechanical strength.
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