Installing a PLCC EEPROM Socket onto a MOBO


Once you have the bottomless socket cleaned up of any spare plastic, it’s time to assemble.   Fire up the soldering iron (with a fine tip already installed!) and while you’re waiting for it to heat up, eyeball the alignment to make sure you can clearly see all the pins aligned with the underlying PLCC pads.   For most of the pads, it’s a no-brainer.   The corner pads are often a bit shorter than the others, so take a close look on how the socket’s leads overlap.   If you’re not careful here, the pads won’t make a good connection to the PLCC leads and the device will be wonky until you go back and fix it.

Now’s a good time to talk about solder.   There should be some solder on each of the PCB pads – it’s probably already here unless you cleaned the pads with solder wick after removing the EEPROM.   Apply a little to any pads that look low.   You can also tin the leads of the socket if you like.   In our case, we didn’t and it worked fine the first try… sorta – we’ll get to that later.

Now that the iron is hot and the pads are prepped, re-align the PLCC socket on the pads and begin tacking it down.   I say tacking because that’s really the technique you will be using.   Just a tap with the point of the iron and each lead should stick down well.   You’ll probably want to do a few pads on the north side, then a few on the south rather than soldering all pads on one side.   This will help to avoid alignment problems.   You should not need to apply any extra solder right now, almost all the leads will solder well with just the small amount of solder that was on the PCB pads.

Fig 3 – Socket installed


Before popping a chip into the socket, you should really do some QA to make sure it’s going to work.   For this example, it can take a few forms.

1. Using a fine set of tweezers or a pin, jab each lead of the socket and apply a little sideways pressure to confirm it is firmly attached to the PCB.   Anyone that moves gets another tap with the iron or some extra solder.
2. Check connectivity if there is enough PCB pad still exposed using a DMM on beep mode.
3. Check for pin to pin shorts using a DMM on beep mode.

We found two leads that were poorly connected and moved when they were jabbed with tweezers.   These were on pads that were pretty low on solder, so it’s not surprising that there was not enough to make a good connection.   It was easy to fix though, with the iron touching the very end of the lead/SMT pad and the solder tapping in about a half mm away.   But we have very fine solder – you may just want to grab a tiny blob with the tip of your iron and go in.

In our case, connectivity was fine and we had no pin to pin shorts.   But if you’re too generous with the solder that may happen.   Usually, pin to pin shorts are caused by excess solder bridging two leads at the PCB level.   Clean it up with solder wick and recheck the lead to make sure it’s still connected strongly.   Finished with QA?   Continue on for the exciting conclusion


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