Saturday, March 23, 2013

Desoldering Surface Mount Devices (SMD)–The hard way

In my previous post, I used some scavenged parts from an old mother board. These old circuit boards are gold mines as they got many reusable components. They may also have very rare vintage chips too. But desoldering SMD is a quite complex task without proper instrument such as hot air gun,reflow oven or a soldering pot. But you can easily desolder SMD components with small pin count. I recommend upto  8 pin or so using this way, If the pins are so close you may try for higher pin count chips too.

You need a normal soldering iron,soldering wire,some tool to push chips and flux would also be helpful in some cases.

My Flux pen (Kester 951):


My tool(small flat screw driver) to remove chips:


First you have to apply some flux (if you have) and add some solder to the pins of the chip just as normal soldering.Make two solder blob in both sides like in this picture(only for one side is shown).


Then simply heat both sides switching between two sides. Don’t take too much time and it will fry your chip. Simply push the chip from the back side using the tool when the solder is melted on pins and chip becomes loose. It will be better to use tweezers to pull up the chip if you have them. I used that flat screw driver as I don’t have a good tweezer. Finally you have to do is cleaning up the board and the desoldered chip. I haven’t used any special thing for it but I think desoldering wick will be helpful.

I have desoldered  this LM431 chip using this technique. You can see the PCB pads where it was soldered in the below picture too.



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