Author Topic: Re-attaching lifted PCB Pads  (Read 704 times)

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Offline paul_g_787

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Re-attaching lifted PCB Pads
« on: April 08, 2021, 03:14:50 pm »
What do you all recommend to use to glue back down lifted PCB Pads?

Would super glue be any good for this purpose? Or would the soldering iron be too hot for it after it is glued?
 

Offline Gyro

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Re: Re-attaching lifted PCB Pads
« Reply #1 on: April 08, 2021, 04:02:12 pm »
What's the context?

Superglue can work as a temporary measure until you get the component soldered - through hole parts shouldn't rely just on the adhesion of the pad for mechanical support and SMD parts hopefully have enough legs that is doesn't matter.
Chris

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Offline paul_g_787

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Re: Re-attaching lifted PCB Pads
« Reply #2 on: April 08, 2021, 04:09:00 pm »
They are through-hole pads for an SIL IC which is attached to a heat-sink.

The heat-sink did not have the mounting-brackets installed, looks like they were missed out for cost. Doh!!

I have made some DIY mounting brackets and so the heat-sink can now be bolted to the PCB.

I intend to bolt the heatsink with the IC attached first, and then solder the joints. That way there should not be any mechanical stress on the pads after I fix the component in place.
 

Offline BreakingOhmsLaw

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Re: Re-attaching lifted PCB Pads
« Reply #3 on: April 08, 2021, 04:10:41 pm »
Would super glue be any good for this purpose? Or would the soldering iron be too hot for it after it is glued?

Regular super glue (cyanoacrylate based) decomposes at 180 °C. So you can't use that.
You can get epoxy with higher ratings (aerospace grade), but even that won't last long at solder temperatures and it is very expensive.

Your best shot is to remove the solder mask from the connecting trace and solder a wire on it and to the component. Keep in mind that sometimes through-holes double as vias, so check both sides of the board.


 

Offline Gyro

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Re: Re-attaching lifted PCB Pads
« Reply #4 on: April 08, 2021, 04:29:51 pm »
They are through-hole pads for an SIL IC which is attached to a heat-sink.

The heat-sink did not have the mounting-brackets installed, looks like they were missed out for cost. Doh!!

I have made some DIY mounting brackets and so the heat-sink can now be bolted to the PCB.

I intend to bolt the heatsink with the IC attached first, and then solder the joints. That way there should not be any mechanical stress on the pads after I fix the component in place.

Ah, nasty. LM3886 amp or similar at a guess!

If it's a power device with the mass of a heatsink (even bracketed), I would put a loop of tinned copper wire around each pin and then take them back along the line of the traces to the nearest secure soldering point. It's the only way it will last.


EDIT: ^ What he said. :D
« Last Edit: April 08, 2021, 04:40:28 pm by Gyro »
Chris

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Offline paul_g_787

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Re: Re-attaching lifted PCB Pads
« Reply #5 on: April 08, 2021, 05:13:01 pm »
They are through-hole pads for an SIL IC which is attached to a heat-sink.

The heat-sink did not have the mounting-brackets installed, looks like they were missed out for cost. Doh!!

I have made some DIY mounting brackets and so the heat-sink can now be bolted to the PCB.

I intend to bolt the heatsink with the IC attached first, and then solder the joints. That way there should not be any mechanical stress on the pads after I fix the component in place.

Ah, nasty. LM3886 amp or similar at a guess!

If it's a power device with the mass of a heatsink (even bracketed), I would put a loop of tinned copper wire around each pin and then take them back along the line of the traces to the nearest secure soldering point. It's the only way it will last.


EDIT: ^ What he said. :D

A KIA6280H In fact. It is in a Dean DGX15 Guitar practice amplifier.
 
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Offline AmnevaR

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Re: Re-attaching lifted PCB Pads
« Reply #6 on: April 08, 2021, 05:54:55 pm »
I usually use a 2 part epoxy for gluing back lifted pads. It dries in 24 hours, so it's the only drawback  :-\
And be careful with epoxies in two tubes, some of them have a metal filler, which could be conductive.

Offline exe

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Re: Re-attaching lifted PCB Pads
« Reply #7 on: April 08, 2021, 06:21:34 pm »
I usually use a 2 part epoxy for gluing back lifted pads. It dries in 24 hours, so it's the only drawback  :-\

I think heating accelerates curing. At 50-70C it solidified within minutes to the point I could use the glued parts. Of course I suggest checking the manual first if it mentions anything about heating and heat resistance.
 

Offline uli12us

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Re: Re-attaching lifted PCB Pads
« Reply #8 on: April 18, 2021, 09:09:54 am »
You can try this or similar glue. https://www.ebay.co.uk/itm/High-Temperature-1200c-Adhesive-Glue-For-Exhaust-Fireplace-Ovens-Collectors70Ml/182720634565?epid=2254398158&hash=item2a8aff9ec5:g:oRcAAOSw1utaovor These parts should be available everywhere around the world. Unfortunatly I don't know how long the content still remains useable. Ordinary Superglue will be cured
inside the tube within several months. Maybe that glue as well.
 

Offline Whales

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Re: Re-attaching lifted PCB Pads
« Reply #9 on: April 18, 2021, 11:35:16 am »
Silicone?  As in the stuff that comes in tubes and is used for sealing gutters.  Slow, cheap and potentially survives soldering temperatures.

Offline BreakingOhmsLaw

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Re: Re-attaching lifted PCB Pads
« Reply #10 on: April 19, 2021, 02:35:40 pm »
Silicone?  As in the stuff that comes in tubes and is used for sealing gutters.  Slow, cheap and potentially survives soldering temperatures.

Unfortunately, regular "bathroom" type silicone releases small quantities of acetic acid over time. That will eventually kill the copper traces by turning them into copper acetate and corrode the remaining copper because the reaction also creates water. That's the reason why EV battery housings are sealed with polyurethane rather than silicone, even if the latter has superior mechanical properties. The fumes would corrode the crap out of the battery.



 
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Offline Microdoser

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Re: Re-attaching lifted PCB Pads
« Reply #11 on: April 19, 2021, 02:54:23 pm »


Some of these old videos have good methods in them. Not sure where you would get eyelets these days though.
 

Offline tkamiya

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Re: Re-attaching lifted PCB Pads
« Reply #12 on: April 19, 2021, 10:57:41 pm »
It really depends but I usually just cut off the trace to a point that is well attached to the board, and bodge wire it, then hot glue it in place. 

It might work if you carefully solder the lifted trace to the part first, then crazy glue it.  When I did that, the solder surface was contaminated with the glue and it didn't wet very well.  If I were to do that again, I would test expoxy instead.  It takes a while to cure, but unlike crazy glue, it won't go all over the place.
 

Online lowimpedance

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Re: Re-attaching lifted PCB Pads
« Reply #13 on: April 19, 2021, 11:08:07 pm »
Silicone?  As in the stuff that comes in tubes and is used for sealing gutters.  Slow, cheap and potentially survives soldering temperatures.

Unfortunately, regular "bathroom" type silicone releases small quantities of acetic acid over time. That will eventually kill the copper traces by turning them into copper acetate and corrode the remaining copper because the reaction also creates water. That's the reason why EV battery housings are sealed with polyurethane rather than silicone, even if the latter has superior mechanical properties. The fumes would corrode the crap out of the battery.
There is neutral cure silicone which you would use, (and should be stated as such on the packaging).
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline Microdoser

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Re: Re-attaching lifted PCB Pads
« Reply #14 on: April 21, 2021, 06:47:26 pm »
For some reason YouTube popped this up on my feed, thought it may come in handy

 

Offline aqibi2000

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Re: Re-attaching lifted PCB Pads
« Reply #15 on: April 21, 2021, 09:06:45 pm »

Solder mask does a very good job sticking pads down
Tinkerer’
 

Offline paul_g_787

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Re: Re-attaching lifted PCB Pads
« Reply #16 on: April 22, 2021, 04:01:13 pm »
Well I managed to repair it!! Thanks for the advice with the pad repair.

Firstly I made a little 90 degree bracket out of an old computer PCI slot blanking plate. Fortunately there was a large ground trace in the PCB right by the IC to drill and bolt this.
So now the weight of the heat-sink is supported nicely and should remove the stress from the pads that caused them to lift in the first place.

I glued the lifted pads back down with Araldite 2 part epoxy. I left them for 48 Hours to be certain it was 100% cured.

As for the other pads which had lifted and snapped off, I glued those back down too, then scraped off the solder mask of the trace right next to the break. When I re-soldered the IC I put a small piece of wire across the break in the trace and made sure the solder flowed fully around the wire and onto the newly exposed copper trace, as well as the original pad and IC pin.

Additionally, when I picked up this Dean DGX15 amp, I was informed it has a loud hum and the guitar sound was very quiet.
Well in fact this was caused by a corroded pin 1 of the KIA6280H. Which is the signal input from the pre-amp. So the joint was barely making contact, but still was slightly. This was causing the hum and the signal level drop.

When I removed the IC, unfortunately pin 1 was so weak and rusted it broke off at the base of the IC!!!!!  :palm:

However I just about managed to rescue it by melting the plastic with the soldering iron to expose the good metal of the pin, just a teeny weeny bit. I was fortunately able to solder a length of wire to this pin (which you can see, the green wire running around the heat-sink). I then soldered this wire to the other side of the board back to where it is supposed to go.

The amp is now assembled back together and is working fine. I had a good go on it for an hour and a half yesterday!
 
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