EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: AlfBaz on April 20, 2014, 11:57:04 pm
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So I lifted a pad off the PCB whilst de-soldering an SMD trimpot. Fortunately it's still attached to the very short track which goes to a via underneath the trimpot.
A bodge wire will be out of the question so I want to try and glue the pad back down before re-soldering.
Initially supa-glue seemed the obvious answer but it seems to be only good for 75degC (167degF). "Heat resistant" supa-glue that I've googled seems to only go to a max of around 120degC (248degF).
A couple of questions...
1. Can you get away with a lower temperature glue considering the very brief time you apply heat to solder the connection, before the glue fails.
2. What glue have any of you guys used in this situation?
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Short answer, epoxy.
Here's a Circuit Board Repair Guide (http://www.circuitrework.com/guides/guides.shtml) that might be really useful.
BEST PCB Trace Repair Kit (http://www.solder.net/products/pcb-repair/trace-repair-kits/). Page has a HOW TO video link at the top of the page.
Hope this helps. :)
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Short answer, epoxy.
So something like araldite should do the trick?
I'm finding it difficult to find any technical data on these "consumer" products where more effort is put into selecting the right hand models than presenting specifications |O
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Short answer, epoxy.
So something like araldite should do the trick?
I'm finding it difficult to find any technical data on these "consumer" products where more effort is put into selecting the right hand models than presenting specifications |O
Not familiar with the brand.
But if you take a look at the guide and video link, you'll notice the epoxy is applied after the trace section has been replaced and soldered, so it's not even exposed to heat at all from the iron (= non-issue, thus opening up the ability to use whatever you can find locally/off the shelf). ;) Good quality stuff should be available at a local hobby store that sells R/C cars and planes for example (cures hard rather than soft).
I'm assuming the broken trace is really close to the pad, which is why you're concerned. I get this, but realistically, unless it's a part that has a large thermal mass, on a ground/power plane or both, the amount of time the iron will be on the joint at some potential later date (fix as per the guide first, then some later repair), a common, good quality, off the self brand should survive (talking a couple of seconds here).
Not sure on brands available to you, but if you're still concerned, a temp specification you'll want to look for is 260C/500F (i.e. test data, if available, should show it can survive for ~ 1 hour/60 min. at this temp without degradation). Up it to 288C/550F, and the test data will drop to ~ 20 min. BTW, this is the type of epoxy ratings you'd find used in standard FR4 PCB material (no need to look for higher, which does exist).
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Short answer, epoxy.
So something like araldite should do the trick?
I'm finding it difficult to find any technical data on these "consumer" products where more effort is put into selecting the right hand models than presenting specifications |O
Araldite is very effective,but messy--Oh,& don't believe the "5 minute" label,it takes nearly as long as the normal stuff.
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Ok thanks for the info. The little bit I was able to gather on epoxy is that the bond degrades under heat but regains its strength when it cools down.
With regards to trace repair, my situation is that a pad has lifted and its connection to the trace is currently still intact. What I want to do is glue the pad down prior to soldering the component onto it, which is why I was concerned about the heat
Sorry about the brand name. Areldite is a two part epoxy that comes in a dual plunger syringe. You squeeze some out onto a working surface and stir the 2 parts together causing an exothermic reaction. I've used this stuff extensively in the past and has a very high viscosity which can be lowered substantially for pouring by applying mild heat from a heat gun.
With regards to the 5 minute crap, I've learnt the hard way. It's 5 minutes til it gels, 6hrs for half cured 24 for full.
I'm heading down to bunnings to get some now :)
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With regards to trace repair, my situation is that a pad has lifted and its connection to the trace is currently still intact. What I want to do is glue the pad down prior to soldering the component onto it, which is why I was concerned about the heat
Wasn't entirely sure, so figured worse case that there may have been a tear involved (had this happen either right where the pad connects to the trace or just before <desolder, lifts & tears when pulling the part>).
You should be fine with the epoxy you've mentioned in any event. ;) Just don't scorch it with the iron set too high/keep it on too long, and you'll be good to go. :o :P
Good luck, and happy soldering when it's cured. :)
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Just don't scorch it with the iron set too high...
Especially when it was this https://www.eevblog.com/forum/chat/rtfm-idiot (https://www.eevblog.com/forum/chat/rtfm-idiot!/msg428928/#msg428928)!/ that probably caused it to delaminate
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Just don't scorch it with the iron set too high...
Especially when it was this https://www.eevblog.com/forum/chat/rtfm-idiot (https://www.eevblog.com/forum/chat/rtfm-idiot!/msg428928/#msg428928)!/ that probably caused it to delaminate
:-DD
Just needed an adjustment to sort that bit out, which you already took care of (thermocouple to the rescue :-+). ;D
Hakko's UI on that station is rather sad though. No idea why they didn't just use "Up" and "Down" buttons, and a pot for calibration. :-// |O
My Weller WD1 uses 5 buttons (Up, Down, & 3 "Radio" buttons to select the presets). Everything else is done in the special feature menus, which takes a unique combination of buttons (UP & DOWN held simultaneously for something like 5 seconds, so not easy to do accidentally). Rather easy actually, even with the additional features it can do. So it's not like you need a lot of them to get a nice UI. Favorite feature? Power switch on the front. >:D
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Hakko's UI on that station is rather sad though.
There's an up button and an enter button, pressing and holding the up button changes calibration :palm:
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Never use cyanoacrylate based glues on stuff that gets hot. When you touch that with your soldering iron for even a very short time you will regret it immediately. It starts to fume and produces a very potent tear gas, even a tiny amount hurts like hell.
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Never use super glue on any electronics. It is conductive.
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I used it all the time for lifted track repair, to hold down the track after soldering. just have to wipe off the bloom afterwards with a solvent. I used to use TCE, but changed later to acetone and an ear bud. Even used it to stick components down, never had an issue with it being conductive.
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Short answer, epoxy.
Here's a Circuit Board Repair Guide (http://www.circuitrework.com/guides/guides.shtml) that might be really useful.
BEST PCB Trace Repair Kit (http://www.solder.net/products/pcb-repair/trace-repair-kits/). Page has a HOW TO video link at the top of the page.
Hope this helps. :)
Very nice information. Thanks for sharing those links. :-+
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Short answer, epoxy.
Here's a Circuit Board Repair Guide (http://www.circuitrework.com/guides/guides.shtml) that might be really useful.
BEST PCB Trace Repair Kit (http://www.solder.net/products/pcb-repair/trace-repair-kits/). Page has a HOW TO video link at the top of the page.
Hope this helps. :)
Very nice information. Thanks for sharing those links. :-+
You're welcome. :)