Replacing ICs, double-sided boards with plated holes
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Author:  PAiA-Scott [ Fri Jun 05, 2009 10:48 am ]
Post subject:  Replacing ICs, double-sided boards with plated holes

Removal of ICs on double-sided printed-circuit boards with small, plated-through holes can be difficult, and hard on the board, but is do-able.

The way I do it here is to use diagonal cutters to get in at the side of the part clipping each pin as near to the body as possible. When this first row has all been clipped, use a small flat blade screwdriver or similar to pry up the cut half being careful to not scrape any top-side pcb traces below the part. Wiggle the body back and forth to break the legs on the other side and leave stubs that can be grasped using forceps or needle-nose pliers. One at a time, melt each joint with the iron and pull the leg from the board. Then melt a tiny bit of solder onto each solder joint to get some new rosin-flux in the joints before going at each one with a desoldering tool or bulb. With the pins not in the hole, it should be possible to clear practically all the solder so a new part can be installed. Note it helps too having a good 60/40 alloy rosin-core solder such as Kester "44" or similar which readily wets and flows. The cylindrical desoldering tools that have a spring-loaded and trigger action really develop a good vacuum for pulling the melted solder out of the hole. Rubber squeeze bulbs work good but you have to keep the tip cleared and it takes a bit more practice. The wicking material puts a lot of heat to the board and isn't so good for evacuating the IC pin holes as it is for, say, removing a blob between adjacent joints that shouldn't be touching. Some isopropyl alcohol on a Q-tip can be used to clean the rosin flux and tidy-up the area before the new part is installed (be sparing so the residue doesn't run to other areas of the board; in particular, into IC socket pin receptacles).

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