Replacing directly soldered IC on PCB with socketed IC- good, bad or ugly? - Page 1
Forum section: electronics / repair

author: nightfire
author_rank: Frequent Contributor
timestamp: June 06, 2022, 10:34:51 pm
content: Pardon if this is discussed to death- then I would need some hints to the threads...Situation: Old equipment, some IC is directly soldered to the PCB, with more than 8 pins, and it eventually is gone bad.Now, without fancy equipment for desoldering and cleaning up the place where it sits, options are limited. Especially when considering that maybe with re-soldering a good replacement might put some real heat on the neighbouring components...So the thought would be, to de-solder the old IC, and solder in a nice IC socket where to place the new IC.In my recent case, I still am stuck a bit with a linear power supply and a LM224N, as central quad-opamp.Questions:- which possible drawbacks could i have in this concrete scenario? Bad contacts in the socket or some higher resistance on the contacts of the socket?- What about effects of HF etc.? Theoretically a linear PSU should work on quite low frequencies, so the enhanced distance to the PCB should not matter

author: PlainName
author_rank: Super Contributor
timestamp: June 06, 2022, 11:31:50 pm
content: If it's old equipment, and you're talking a possible socket, then it's a DIL package, yes? In which case the trick is to snip all the legs off at the join with the IC body, then remove them one at a time (apply iron to pad, pull pin with pliers/tweezers). Very difficult to go wrong.Still doable with something like PLC44, and even SMD (though you need thin cutters to get in there).As to replacing with a socket, it makes replacement next time easier if you think there will need to be a next time. However, IC pins have a habit of walking out of sockets if there is any vibration around, and a good knock against something solid might see it pop up altogether. Soldering would be the more robust option.

author: strawberry
author_rank: Super Contributor
timestamp: June 07, 2022, 05:57:11 am
content: not for nA fAstamped sheet metal sockets tend to deform or corrode at high temps plastic deforms contact connection get loose and plastic cracks (thin plastic) (not problem for 5..10y)machined sockets are more solid and available gold plating

author: jpanhalt
author_rank: Super Contributor
timestamp: June 07, 2022, 09:02:56 am
content: One concern is socket is height. Machined pin sockets or single pins can be used. They give a reliable contact. For single pins, they can be bought with a carrier that makes installation easier and gives a very low profile socket. Mill-Max sockets are one common brand.EDIT: Added machined pin carrier image.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 07, 2022, 09:57:18 am
content: For high speed the extra inductance and capacitance can be an issue, but not with an LM224. For things like OP-amps it is not the actual frequency the cicuit works with, but the GBW of the part that matters if supply decoupling / sockets are critical.For a repair it absolutely makes sense to add a socket.

author: wn1fju
author_rank: Frequent Contributor
timestamp: June 08, 2022, 01:36:12 am
content: OK, here's an "ugly" example that happened to me. I was trying to diagnose a piece and suspected one particular DIP IC. I have a decent desoldering gun and can usually pull out chips intact. I pulled the chip, installed a socket, then installed a brand new IC in the socket. When that didn't change the malfunction, I decided to put the old IC back in the socket rather than "waste" a brand new one. Big mistake because I must not have gotten all the solder/flux/debris off of the old IC pins when I desoldered it. The result was that the chip did not make good contact. Took me a while to figure out what was going on.

author: David Hess
author_rank: Super Contributor
timestamp: June 08, 2022, 03:42:17 am
content: Quote from: nightfire on June 06, 2022, 10:34:51 pmSockets reduce reliability unless the IC itself is unreliable, but in practice this is not significant for rework.QuoteAt a high enough frequency, the added parasitics from a socket cannot be tolerated, and this also applies when exceptionally low leakage is required. Low profile DIP sockets can be used up to at least 100 MHz.Quote from: jpanhalt on June 07, 2022, 09:02:56 amI cut the machined pin sockets out of the SIP and solder them into place flush as shown below where heat from the 723 regulators caused the leaf sockets to become loose.