best epoxies for pad & trace repair?

[vivi-d]

Hello, I'm repairing PCB's for my employer (EMS type company). IPC doesn't directly specify which adhesives to use for gluing pads onto a board.

Right now I'm using LocTite 454 which seems to be working mechanically. My question is: what is the professional adhesive I should be using? Some of the boards I work on are very sensitive (measuring fA for instance). What do you guys recommend?

[perieanuo]

hi, i'm not sure gluing pads for fA stuff is professional
i saw in industrial production silicon use, resin use (special laser sealing for power modification impeachment, schematic protection etcaetera) and the glue for component fixing before soldering process. for resin, there were long threads here, the subject is not easy, choosing the wrong resin can put you out of pcb manufaturing/assembly bussiness if done wrong, but for maintenance/repair must be not a big deal, you won't put a wrong resin on 10000 boards just ordered from france
i'll watch carefully this thread 

[jpanhalt]

Circuit-Medic sells an general purpose epoxy for "board repair."
https://www.circuitmedic.com/parts/115-3302.html
The price seems outrageous, but the mix ratio is 1:4 (hardener:resin), which implies it is not your typical hardware store epoxy.  Circuit Medic may have more information related to its use.

Twenty plus years ago, I moved to a new job that had a blood bank.  Someone had repaired the bubble detector on a platelet infusion machine. That person was not certified nor was the manufacturer contacted to re-certify the machine.  (All before I got there.) When the FDA inspected, that was cited as using an unapproved instrument for medical care -- a major deficiency.  Our license was put into a probationary state and subject to unannounced re-inspection within 6 months.

fA sounds like some sort of monitoring device.  Did the medical director of the EMS unit approve such repairs?  What agency inspects?  In any event, it is probably an FDA approved/cleared device, and I recommend contacting the manufacturer to find out what sort of repairs/modification it allows.  Dealing with the FDA can be challenging.

[David Hess]

hi, i'm not sure gluing pads for fA stuff is professional

*Using* pads for femtoamp circuits is marginal.  Such high impedance nodes are commonly wired in air or using Teflon standoffs.  It can be done but it requires careful quality control after assembly and even then it will be subject to contamination.

[vivi-d]

Thanks for the insight

I'll try the stuff from circuit-medic.

I've been asked to repair the fA boards we have, but I've always declined since it didn't seem kosher "so to speak". I'll check with our customer of course.

We do a pretty involved wash process with these boards, in addition to only handling them with gloves.