Friday, April 17, 2015

Desoldering parts from a buck converter module

A few weeks ago, I wrote about building a power supply based on a LM2596 buck converter module. The design came from a posting on instructables. Destructables might be a better name, as you have to remove two present pots from the board and it's very easy to damage it in doing so. After my first messy attempt I decided to try to do it better. I've desoldered things with a solder sucker and with solder wick, and by just heating and wiggling the part, but all of these have the risk of damaging small tracks or pulling out the through hole plating. A bit of searching pointed me at using ChipQuik. See this video for a good description of it, and also part of this one. It's expensive to buy, but it turned out I had some lying around from a SMD soldering skills kit I got at Jameco. You slather some flux paste on the joints, then melt something which looks like solder over the joints. It's actually not solder, but an alloy which merges with the solder and gives you a mixture that has a lower melting point. You can can then keep all the pins molten which you gently pull on the part. To clean up, I used solder wick, taking a tip from the second video. Melt some solder onto the tip of the soldering iron, place the solder wick over the area to clean up, and then press the soldering iron onto the solder wick. The solder on the tip of the iron helps the wick heat up quickly and transfers heat the the areas of the board you are working on. Together these resulting in a board with clean holes and no damage to the tracks. Nice.

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