Repair/bodge footprint too small (PLCC-6) - Page 1
Forum section: electronics / repair

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: January 30, 2017, 01:17:09 pm
content: So... On theonefootprint I thought safe to just download online and use I get regrets after...Thought it was a standard 5050 PLCC-6 but I failed to double check and this is where I'm at:Any ideas how to fix?These pesky APA102's have a very low temp melt on the bonding wire. Cant touch it for long even with my lowest temp soldering tip.1) How about tinning the LED and using hot air to make it flow onto the pads? Seems they arebarelytouching.2) Getting some solder paste & flux and proceed with hot air gun?3) Is there such a thing as conductive double sided tape? Maybe I can extend the pads somehow?Any ideas are welcome! I guess I'll start butchering one of the PCBs and try some stuff out

author: Twoflower
author_rank: Frequent Contributor
timestamp: January 30, 2017, 08:18:00 pm
content: I would solder some copper wires or if you have copper tape (google it) on the PCB and then solder the LED on top of the wires. Probably use Kapton tape to hold the 'extenders' in place while solder them on the PCB. Especially if you use copper tape the pieces can be hold in place by the LED during soldering the LED on. Using some glue to fix the LED afterwards to prevent losing itself.Alternatively there's copper tape with glue on one side. I haven't used it. But it might be worth a shot. But try it on a scrap PCB first to see how the glue behaves. You can fold the part that goes on the pad to have pure copper to solder it on the pad. To get that folding part in the right size and place them in the correct position might take more time than just use the non glue option.Conductive colour cant be used to solder on (at least to my knowledge).

author: elecman14
author_rank: Unknown
timestamp: January 30, 2017, 08:26:26 pm
content: The copper tape Twoflower mentions with the "glue" in me experience does not stand up well to soldering. The glue/adhesive seems to not stick once the copper has been re-flowed. Not really sure where I got this copper tape, it just appeared in the junk box. You may want to search for "PCB land repair". That will probably point you in the correct direction. It will probably be cheaper to re-spin the PCB unless it is something exotic like 6+ layers or huge.

author: Ian.M
author_rank: Super Contributor
timestamp: January 30, 2017, 08:37:08 pm
content: Low temperature solder paste, hot air and *HOPE* there's enough footprint overlap. If it works, clean up the flux then run superglue under them for strength.

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: January 31, 2017, 01:47:21 am
content: Thanks for all the input guys!I think I'll try this route first:Quote from: Ian.M on January 30, 2017, 08:37:08 pmThe thing about a respin is that I really don't have time to get this stuff done. Deadline in a few days only. So I'll get on it tomorrow or the next day cross my fingers very hard. It seems to at least besomeoverlap.It's a four layer board, done by MacroFab (so quite expensive per piece, but I've only spent about 10 hours total on them so far so grand total - still cheap), can't afford the time or really the money for a respin.It's for a client, under the "rapid prototyping" umbrella. It of course means way too little time, and "luckily" also too little money...Thanks again guys, I'll find a way. When I do I'll take a photo of the nightmare here

author: sleemanj
author_rank: Super Contributor
timestamp: January 31, 2017, 02:08:14 am
content: Quote from: alexanderbrevig on January 30, 2017, 01:17:09 pmYes there is, not to say it's a solution to your problem, but you asked if it exists. It's colloquially called "Z Tape", it's conductive in the Z direction only...https://www.adafruit.com/product/1656http://solutions.3m.com/wps/portal/3M/en_US/Electronics_NA/Electronics/Products/Electronics_Product_Catalog/~/3M-Electrically-Conductive-Adhesive-Transfer-Tape-9703?N=8704978+3294001720&rt=rud

author: Ian.M
author_rank: Super Contributor
timestamp: January 31, 2017, 04:00:36 am
content: Worst case: You can sweat on pre-tinned copper foil pad extensions using normal solder, (tin and wipe off all excess before cutting them out), tin the pad and apply with a probe to hold in place, by fluxing and heating with a freshly wiped flat surfaced bit (so as to avoid increasing the solder on the top of the foil). Clean up then hot-air reflow the LEDs to the pad extension using low melting point paste, exploiting the difference in melting points.

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: March 05, 2017, 04:47:57 am
content: This took a while as priorities changed, but now (05:43 AM) I finally got firmware uploaded to the ESP8266 and got an LED working!What I ended up doing was:1) "extend" the pads with some thin tinned copper wire2) tack on one side of the LED to the footprint3) wrap the wires up and solder on to the LED on the other side4) ? ? ? ?5) PROFITApologies for the mess! Hehe....Kind of difficult the first times, but I'm starting to get the hang of it (and I'll only have to do it about 30 times which is manageable).Thanks again for all your ideas