Sunday, February 2, 2014

Korg Pad Kontrol Repair: SMT soldering issues


This Korg Pad Kontrol came to me with issues with not turning on. When I disassembled the unit, I noticed that Lead Free Solder was used ("lead free" printed proudly on the circuit board). I applaud efforts at preserving the environment, but also have become aware that in more than a few circumstances I have found lead free solder to fail. For every unit with failed lead-free solder that I have repaired, I am sure there are hundreds that met an early demise and wound up in the landfill. It has made me question the value of lead free solder, especially as an environmentally friendly alternative to good old fashioned lead. So, personally, whenever I see that lead free solder was used, I check especially hard for failed solder connections.

Sure enough, around IC7 I was able to locate broken solder around some of the pads. The board was most likely flexed, and some of the legs of IC7 had pulled up from their pads. You will see in the first picture that one of the legs on IC 7 had actually gotten bent away from its pad; this actually occurred when I touched the leg with a DMM probe, as I was trying to ring out one of the leg to somewhere on the board. Of course, the fact that it moved so easily was a clear indication that the leg was detached from the pad.

Working slowly with a razor blade, I was able to carefully line the leg up again, and then reflowed all the traces around that IC with some fresh solder. With lead in it.

Some pictures of the work are below; you can notice the size of the chip by seeing a penny on top of it.

For work like this, I use a USB microscope, solder paste, and a hot air rework station. Cleanup afterwards is essential, I use a toothbrush and 91% alcohol.

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