Author Topic: How to re-attach a lifting pad to PCB?  (Read 2169 times)

0 Members and 1 Guest are viewing this topic.

Offline krivx

  • Frequent Contributor
  • **
  • Posts: 763
  • Country: ie
How to re-attach a lifting pad to PCB?
« on: June 03, 2015, 09:18:00 am »
I have a PCB where the thermal pad of a DPAK voltage regulator has lifted away, presumably from heat. There is still a trace holding to the board. Can I glue this down and solder a new regulator? I was thinking that CA glue may not work because it will melt during soldering, would a 2 part epoxy with a higher temperature rating work better?
 

Offline krivx

  • Frequent Contributor
  • **
  • Posts: 763
  • Country: ie
Re: How to re-attach a lifting pad to PCB?
« Reply #1 on: June 03, 2015, 10:45:27 am »
This has turned out to be a rush-job, so it ended up as high-temperature epoxy (EpoTek 353nd) under the pad, light clamping force and oven-curing for an hour or two. Fingers crossed.
 

Offline Skimask

  • Super Contributor
  • ***
  • Posts: 1425
  • Country: us
Re: How to re-attach a lifting pad to PCB?
« Reply #2 on: June 03, 2015, 12:11:19 pm »
2 part epoxy is about the only way to go for that sort of repair.
Be careful when you go to solder the pad.  Even though you used high temp epoxy, the epoxy itself may over-due to the heat and end up a bit crystalized.
Used plenty of flux, try not to solder directly on top of the epoxy on the repair, keep the heat down as low as you can while still keeping enough heat to melt the solder quickly enough to 'get it and get out'...etc, etc, etc.
I didn't take it apart.
I turned it on.

The only stupid question is, well, most of them...

Save a fuse...Blow an electrician.
 

Offline krivx

  • Frequent Contributor
  • **
  • Posts: 763
  • Country: ie
Re: How to re-attach a lifting pad to PCB?
« Reply #3 on: June 03, 2015, 12:25:25 pm »
The Epotek was curing in the oven at ~100C for an hour and seemed to work great. I used Kapton as a mask thinking it wouldn't adhere (:palm:) so I had to scrape away some Kapton where I had squeeze-out but the voltage regulator is providing correct voltage under load now that I have replaced it.

I would recommend the epoxy for this kind of work. It should be good for 250C continously and 350C momentarily, so it seems like a good fit for most soldering processes.
 

Offline dacman

  • Frequent Contributor
  • **
  • Posts: 397
  • Country: us
Re: How to re-attach a lifting pad to PCB?
« Reply #4 on: June 07, 2015, 08:06:43 pm »
If there is nothing on the other side, and the board isn't multilayer, I'd consider installing an eyelet.
 

Offline wagon

  • Frequent Contributor
  • **
  • Posts: 290
  • Country: au
Re: How to re-attach a lifting pad to PCB?
« Reply #5 on: June 07, 2015, 11:43:20 pm »
I've used a thin piece of copper sheet, cut to size, as a heatsink.  Then I glue the copper to the pcb and solder the SMD part to it.  Worked well on the couple of boards I fixed. (You'll probably need to extend the two legs a bit, probably won't reach the pads)
Hiding from the missus, she doesn't understand.
 

Offline Deathwish

  • Supporter
  • ****
  • Posts: 1426
  • Country: wales
Electrons are typically male, always looking for any hole to get into.
trying to strangle someone who talks out of their rectal cavity will fail, they can still breath.
God hates North Wales, he has put my home address on the blacklist of all couriers with instructions to divert all parcels.
 

Offline wagon

  • Frequent Contributor
  • **
  • Posts: 290
  • Country: au
Hiding from the missus, she doesn't understand.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf