A cut run or line on a printed circuit board (PCB) is a problem most technicians face. There are several ways to repair a cut run, but before performing this work on a critical board, it would be wise to practice on some scrap boards first. While the skills can be learnt through trial and error, formal classroom training is preferred. Listed are three methods that may remedy a cut line on a motherboard.
- Skill level:
Things you need
- Hobby knife
- Toothpick or dental pick
- Conductive epoxy
- Conformal coating
- Solid bus wire
- Rosin flux
- Temperature-controlled soldering iron
- Cotton swabs
- Circuit board repair kit
Repair a broken conductor on a PCB with conductive epoxy. Use a hobby knife to scrape the solder resist coating from atop the conductor on both sides of the break. Scrape down to bare copper, but exercise care because the runs are thin and easily damaged. Expose about a quarter of an inch on both sides. Clean the area with alcohol. Mix the epoxy and apply it using a toothpick or dental pick. After it fully cures, apply conformal coating over the repair.
Repair a broken run with a piece of solid bus wire. Begin by scraping the run clean of solder resist coating with a hobby knife. Scrape down to the copper, but be careful not to cut the conductor. Clean it with alcohol, and then apply rosin flux to the ends. Tin the ends with the soldering iron by applying a small amount of solder. Cut a piece of bus wire to fit the tinned ends and place it carefully along the run. Solder it to the ends, and then clean up any excess flux with alcohol. Cover the repair with conformal coating.
Repair a cut in a run with a PCB repair kit. These kits normally come with a selection of pre-tinned run repair materials in various widths. With a hobby knife, clean the run on either side of the cut for about one quarter of an inch. Apply flux and tin the ends. Select a run repair piece that is about the same width. Carefully align it, and then sweat it down by applying the soldering iron on top. The solder layers will bond. Clean up with alcohol and cotton swabs. Cover the repair with conformal coating.
Tips and warnings
- Never try to rush this work. Do it carefully so that it's right the first time.
- Alcohol and conformal coating are flammable. Keep them away from your soldering iron.
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