|yldouright||6/12/2018 1:42 PM|
|How do you fix torn/worn solder pads?|
Any electronics repair veteren has run into these and I'm sure there are numerous ways to address them. I'd like to hear them all.
|J M Fahey||6/12/2018 2:10 PM|
|If just unglued but still healthy otherwise I re glue to board with a tiny drop of clear epoxy, whatever a toothpick tip can pick.|
Soldering makes it harden and I consider them "as good as new",after all original copper was glued to original board when it was manufactured, either epoxy or phenolic.
You may have to scratch board surface first, it will probably be covered or smeared with rosin flux, which is NOT an adhesive by any means.
|drewl||6/12/2018 3:49 PM|
|Slice out the bad section and scratch off the coating of the nearest good section and run a jumper to that, or drill through a good section.|
You want a good mechanical connection to solder to.
|yldouright||6/12/2018 3:53 PM|
Damn, that's aggressive! I never drill multilayer boards.
@J M Fahey
Yep, I use crazy glue after cleaning off any residual flux and crap with denatured alcohol. What do you do when you lose a bit of trace too? Do you mend with aluminum foil, solder braid?
|Enzo||6/12/2018 4:16 PM|
|Can't solder to aluminum with electrical solder.|
If I lose a trace, I use wire.
|g1||6/12/2018 6:41 PM|
|You mentioned multi-layer boards, how many layers? If vias (feedthroughs) are involved, there are bigger problems.|
I don't think any of the responses were for multi-layer, as we don't see a lot of that with (repairable) music gear.
|xtian||6/12/2018 7:20 PM|
|Stake a turret, if enough room.|
|yldouright||6/12/2018 8:22 PM|
Yes, I was thinking mostly of CPU boards when I made that comment. I recapped a motherboard board years ago that stopped working. It took me months to discover I damaged vias inside the hole!
Yes, aluminum only works with a spot weld repair but it is an option.
|drewl||6/12/2018 8:36 PM|
|We had this stuff at work, Circuit Coat or something.|
Green goo that dried coating boards with an insulator keeping things in place.
Been trying to find more as we ran out.
|J M Fahey||6/12/2018 10:18 PM|
|I specifically mentioned transparent Epoxy because itīs closest to whatīs used to make Epoxy PCBs but most important, is thermo stable and stands soldering temperatures; krazy glue or other adhesives do not, just melt/bubble/burn at molten solder temperature.As of missing tracks, yes, wire is the only option.|
"Somebody" used to sell adhesive tracks and pads specifically to repair PCBs, but know no details about that.
|olddawg||6/12/2018 10:58 PM|
|I always kept a jar of various lengths an thicknesses of solid wire to repair traces of various sizes. If you have a large ground plane, yeah solder braid works great and will help structural integrity. If you have a crack, always drill a hole at the end of the crack. IMHO, never jumper a broken trace with just a blob of solder... it inevitably will fail. We used to get these fiberglass scrubbers that looked a bit like a pen that were convenient for scrubbing the protective surface off of the board and expose the copper trace. Most of the boards I repaired were rarely epoxy. They were resin impregnated thick paper. That’s why they would charcoal and become conductive if components got hot enough. In that case you have to grind the affected area out with a dremel and run fly wires.|
|Mick Bailey||6/13/2018 12:47 AM|
|Often pads become loose with power components such as dropper resistors or zeners and if there's enough room I insert a 1.5mm tubular brass eyelet and solder in the component. Sometimes the edge of the eyelet will overlap onto the trace, other times I wire back to the destination pad. With regular components I'll stick down a lifted pad with epoxy. With SMD this is often the best option, with through-hole there's more choice over what to do.|
If a board is seriously damaged and the equipment is valuable enough I etch a new section, dremel out the old area and epoxy the new piece in place then bridge the joints with copper foil soldered into position.
|J M Fahey||6/13/2018 1:46 AM|
|ric||6/13/2018 9:11 AM|
|Is there a type/ brand of "clear"/ heat tolerant epoxy that you people use?|
The brand I use (Devcon) sets somewhat amber and I've never thought of it as particularly heat resistant, though I guess that was an assumption that I've never needed to test.
I lifted a trace and would like use this info, but want to use the right stuff.
|yldouright||6/13/2018 2:04 PM|
|mozz||6/13/2018 2:33 PM|
|We use these at work when we have to but very expensive.|
Most pcb's for musical equipment amplifiers are junk. Good boards cost good money and we can't have that can we? Best bet is "get in get out" solder as fast as you can and do not get the board hotter than absolutely necessary.
|nickb||6/13/2018 2:52 PM|
36in of 2 x 5 thou copper wire $39.95! Seriously!! Tinned copper will do the same job equally well.
|glebert||6/13/2018 3:22 PM|
|I just have this image of Juan mixing two part epoxy, but just enough for a toothpick tips worth. Dude's got a trick for everything, I am sure he has one for this too.|
|J M Fahey||6/13/2018 3:53 PM|
I meant "pure epoxy" instead of the powdered aluminum filled one or white or black which carry pigments.
It will lose strength while solder hot , exact same as original Epoxy PCB material Epoxy, of course, but unless you juggle the component lead around while itīs at peak temperature or push through an unopened hole it will reasonably hold.
In an nutshell, what made the *original* pad or track lift.
If the hole is clean, surface is clean, you solder fast and not subject it to mechanical effort while soldering, it will be practically "as good as new".
Cyanoacrilate? .... maybe there is some NASA quality version out there, dunno, but standard one is way weaker than Epoxy, specially when hot.
There must be some reason that speaker voice coil wire is routinely bonded to form with Epoxy and not with CA.
And that copperclad board material is bonded by curing under pressure a copper sheet and Epoxy or Phenolic Rosin impregnated paper/fiberglass sheet.
I know no PCB material made by glueing copper to insulating base using CA.
|Mick Bailey||6/14/2018 2:00 AM|
|I use all kinds of Cyanoacylate for work-holding in the lathe and miller. Strong enough when cold but easily separated when warmed up. I have my doubts that it would hold a pad where a component gets warm. I never tried it on a regular solder pad because of the heat of soldering (especially unleaded) breaking it down.|
Whenever a pad has lifted, after repair I clean away the flux residue and use UV epoxy over the top as extra security. It flows really well and strengthens the joint area.
|ric||6/14/2018 4:31 PM|
|Sounds like if the boards are laminated with epoxy, that's the stuff to use. Now I see what Juan meant by "clear" epoxy. The question now becomes: what is the UV epoxy Mick mentions? Ultra violet light stabilized?|
|Mick Bailey||6/15/2018 3:50 AM|
|The UV cure epoxy is polymerized with a UV torch and is really tough. I have some used for tying fishing flies and it's available in different viscosities. You can use regular epoxy, though this stuff is water-clear so in the future you can see what's going on underneath. I just happen to have this to hand as I use it for guitar repairs.|
|ric||6/15/2018 8:20 AM|
|Helmholtz||6/15/2018 9:01 AM|
|Many UV curing adhesives are actually urethane based with a temperature range up to only 150°C. For the purpose here I would only buy stuff with a data sheet explicitely specifying epoxy and/or a temperature range up to 200°C or more.|