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I have a PCB mounted to a chassis with 16 feedthrus, the feedthrus posts are soldered to plated thru-holes in the PCB. I would like to remove the PCB from the chassis, the problem is that I am unable to remove 100% of the solder from the plated thru-holes and I am unable to simultaneous heat all 16 points to try and remove the board while the solder is hot. The 16 posts are arranged in two identical groups of 8 with an identical outline.

Whole assembly with solder points circled in red: Another view of whole assembly with solder points in red: Closeup view of just 1 group of 8 solder points:

I've tried to remove the solder from the thru-holes using solder wick and a vacuum solder-removal gun but a little solder is always left, this is probably due to the sizing of the holes which are only slightly bigger than the feedthru pin, 22 and 18 mils respectively.

One idea is to make a custom soldering iron tip that exactly matches the hole pattern so that all 16 holes can be heated simultaneously, then the board can be removed while the solder is liquid. I've never made a custom soldering tip before so this method has some inherent risks from the unknowns.

Any other suggestions for removing the PCB? Also, heating the whole assembly above 150°C is not desirable due to sensitive components that are mounted to the chassis on the other side.

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    \$\begingroup\$ What about a shaped hot air nozzle? \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Jan 14, 2015 at 16:32
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    \$\begingroup\$ When you use a vacuum desoldering iron, are you adding solder to the joints beforehand? Try adding fresh solder to the joint (with a regular iron and plenty of heat), then using the vacuum desoldering iron. That tends to help remove all of the solder in one fell swoop. \$\endgroup\$
    – Shamtam
    Jan 14, 2015 at 18:28

3 Answers 3

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You might want to try with ChipQuik. It is a solder that has much lower melting point than your everyday solder. When you remove as much solder as you can, flood it with ChipQuik. Given enough solder, it should be possible to keep all points in melted state by reheating them in turn as they turn solid.

Once you do have them all melted at the same time just wiggle the board until you get it out. And don't forget to clean ChipQuik before you resolder things back in.

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    \$\begingroup\$ I ended up using a bit of Indium solder (Indalloy 290) that we already had on-hand, expensive I know but I've ordered some ChipQuik for next time. The lower melting point of the Indium mixed with the Tin from the regular solder was good enough for me to extract the board while warm. The procedure I used was to remove all the regular solder possible with a vacuum solder gun and copper solder wick and then apply the Indium based solder to the pins. I then removed as much of that solder as possible, and then with the board still warm I lifted up on the PCB; worked like a charm. \$\endgroup\$
    – DakotaD
    Jan 23, 2015 at 19:58
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I'm assuming no access to the other side. (Otherwise cut the pins and remove them one at a time.) I like a solder sucker for this. (But this also assumes none of the pads are connected to a ground plane... It's sometimes hard to get enough heat into the ground pad pins.) Make sure the solder sucker is clean (My has an o-ring that I will take out and re-grease.) Then work hole by hole, sucking out the solder. Then for that last bit of solder that holds the pin to the pad, heat it and try wiggling it with some tweezers until it is free... sometimes you can push it down a bit. If this doesn't work then my only other thought is to try and drill the pins out.

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    \$\begingroup\$ +1 Ideally a good solder rework station with an electric pump and not one of those plunger toys. Sometimes you can suck enough of the solder out with a good wick to do without the rework station, but there are inexpensive Chinese ones available now for the cell phone repair trade. My strategy is to suck as much as possible of the solder off and then push the pin sideways to try to break the remaining solder holding it to the edge of the hole plating. Even if that slightly damages the plating, it's only part of the PTH plating. Probably not proper hi-rel procedure but it's not failed (yet). \$\endgroup\$
    – Spehro Pefhany
    Jan 14, 2015 at 16:53
  • \$\begingroup\$ @SpehroPefhany , I've got a DP-100 desoldering pump from OK. It works fine for me. (I hate the little ones) A technician here has a rework station with pump, But I've had more luck with my big plunger. \$\endgroup\$
    – George Herold
    Jan 14, 2015 at 17:02
  • \$\begingroup\$ I have a Pace station with a graphite vane pump, which works okay (don't use it very often, but it does come in handy sometimes). Maybe you're better at using the plunger things than I was. I bought a dubious-looking RS thing with a red squeeze bulb, as a backup, but I don't think it's ever been used. \$\endgroup\$
    – Spehro Pefhany
    Jan 14, 2015 at 17:45
  • \$\begingroup\$ I've seen a BGA rework station with temp controlled air above and below used to change out thermal-pad QFN's on a boards in such a heat-sucking RF housing with mixed success. Preheat the housing from below (not to soldering temp, but every bit helps), large hot air nozzle above, work in stages as suggested. \$\endgroup\$
    – Chris Stratton
    Jan 15, 2015 at 4:03
  • \$\begingroup\$ @SpehroPefhany - Those dubious things with the squeeze bulb are actually surprisingly effective. The main issue with them is the tip plating is terrible, and the tip gets eaten away after a few hundred joints. For the price, they're absolutely great, though. \$\endgroup\$
    – Connor Wolf
    Jan 15, 2015 at 6:39
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This always worked for me. Use a hot air gun and heat up one side and lift it up a little bit and hold it until the solder cools down. Do the same on the other side. Repeat until the pins come out of the board. This way you don't heat up the whole boards and endanger sensitive components. Best for the job would be a narrow nozzle hot air gun, or you can make a nozzle reduction using some aluminum foil and shape it conveniently for the area you want to heat up. Good luck.

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