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How to get that epoxy off those boards

10/18/2000 8:39 PM
dr.dan	How to get that epoxy off those boards When you guys talk about getting the"epoxy off the boards"are you talking about that black potting compound epoxy?Well,were you aware that with some care and practice,you CAN perform some "archeology"on that effect?The company I work for routinely does repairs on "potted epoxy"circuit boards all the time.What you do is,take a heat gun;heat up the epoxy a little at a time with the heat gun in one hand(hopefully you have a decent vise to hold the board in while youre doing this)and while its heating,take a dental pick,preferably one with a curved and flattened blade with the sharp edges slightly rounded so as not to scrape the traces too much;it should scrape off without too much trouble in flakes.Whatever you do,DONT USE A SCREWDRIVER!!!!!!!!!!Just remember toA)Put a shield in front of the wires,maybe a piece of tin,to help keep excess heat directly off the wires;(B)Dont keep the heat directed on the board constantly-just occasionally,you only need to heat the epoxy up to the flaking point,and not try to "burn"it off.Its tedious,but it works!I would practice on something else first,if you can find something(like something from the auto junkyard maybe?)I wish I had some spare junk boards you could practice on,I would send some out,but this is all I have.Happy pedalmaking!

10/18/2000 8:39 PM

dr.dan

How to get that epoxy off those boards

When you guys talk about getting the"epoxy off the boards"are you talking about that black potting compound epoxy?Well,were you aware that with some care and practice,you CAN perform some "archeology"on that effect?The company I work for routinely does repairs on "potted epoxy"circuit boards all the time.What you do is,take a heat gun;heat up the epoxy a little at a time with the heat gun in one hand(hopefully you have a decent vise to hold the board in while youre doing this)and while its heating,take a dental pick,preferably one with a curved and flattened blade with the sharp edges slightly rounded so as not to scrape the traces too much;it should scrape off without too much trouble in flakes.Whatever you do,DONT USE A SCREWDRIVER!!!!!!!!!!Just remember to

A)Put a shield in front of the wires,maybe a piece of tin,to help keep excess heat directly off the wires;(B)Dont keep the heat directed on the board constantly-just occasionally,you only need to heat the epoxy up to the flaking point,and not try to "burn"it off.Its tedious,but it works!I would practice on something else first,if you can find something(like something from the auto junkyard maybe?)I wish I had some spare junk boards you could practice on,I would send some out,but this is all I have.Happy pedalmaking!

10/18/2000 9:35 PM
aron	Thank you. Yes, R.G. has stated this in the past - recently however, he has been posting this as an alternative: "A stainless steel screw that screws into a cheapo Radio Shack soldering iron tip with its head ground away to a chisel shape makes a good tool for removing hardened epoxy that you don't want where it is. The heat decomposes just a bit of epoxy so it can be peeled up a layer at a time. Slow work, but not particularly dangerous to the PCB."

10/18/2000 9:35 PM

aron

Thank you. Yes, R.G. has stated this in the past - recently however, he has been posting this as an alternative:

"A stainless steel screw that screws into a cheapo Radio Shack soldering iron tip with its head ground away to a chisel shape makes a good tool for removing hardened epoxy that you don't want where it is. The heat decomposes just a bit of epoxy so it can be peeled up a layer at a time. Slow work, but not particularly dangerous to the PCB."

10/18/2000 9:45 PM
R.G.	I've posted this here before. I find this much simpler. In fact, you may want to try this at your work. Get a cheap-o soldering iron that has a tip that simply screws into the heating section. Unscrew the tip, and find yourself a stainless steel screw that screws tightly into the heating section. I used a #8-32 stainless screw I got at Home Depot. Take the screw, and grind the head off to make a slightly-sharp chisel point. Plug in the iron, let it get hot. The temperature is enough to soften and decompose the epoxy and flake it off a small section at a time. It will slowly "plow" up a furrow of epoxy. This is much faster at removing gook than dental pick, at least for me, and it removes the fire danger that exists when you use a non-temperature regulated hot air gun on a compound that has a flame temperature not much above the softening temperature. I suspect that with a more finely fashioned tool that was temperature controlled to the right temperature, it could be downright easy.

10/18/2000 9:45 PM

R.G.

I've posted this here before. I find this much simpler. In fact, you may want to try this at your work.

Get a cheap-o soldering iron that has a tip that simply screws into the heating section. Unscrew the tip, and find yourself a stainless steel screw that screws tightly into the heating section. I used a #8-32 stainless screw I got at Home Depot.

Take the screw, and grind the head off to make a slightly-sharp chisel point. Plug in the iron, let it get hot. The temperature is enough to soften and decompose the epoxy and flake it off a small section at a time. It will slowly "plow" up a furrow of epoxy.

This is much faster at removing gook than dental pick, at least for me, and it removes the fire danger that exists when you use a non-temperature regulated hot air gun on a compound that has a flame temperature not much above the softening temperature.

I suspect that with a more finely fashioned tool that was temperature controlled to the *right* temperature, it could be downright easy.

10/18/2000 10:11 PM
dr.dan	I guess the part I was leaving out was that I forgot to mention the heat gun has a set of reducers,or sleeves of various sizes for focusing the stream of hot air.Its not the common kind you would use,like the Wagner that is used more for stripping paint. Also,the gun has a rheostat to adjust the heat.I dont do that type of work there anymore,but I remember the soldering iron idea,and it worked fine until you run into something fragile.I think we bought those heat guns from someplace like Techni-Tool or MCM.I was going to buy one of those surface mount rework stations with the hot air blowing device until I saw the price....WHEW!!!Guess itll be me an my Metcal for a while longer.

10/18/2000 10:11 PM

dr.dan

I guess the part I was leaving out was that I forgot to mention the heat gun has a set of reducers,or sleeves of various sizes for focusing the stream of hot air.Its not the common kind you would use,like the Wagner that is used more for stripping paint. Also,the gun has a rheostat to adjust the heat.I dont do that type of work there anymore,but I remember the soldering iron idea,and it worked fine until you run into something fragile.I think we bought those heat guns from someplace like Techni-Tool or MCM.I was going to buy one of those surface mount rework stations with the hot air blowing device until I saw the price....WHEW!!!Guess itll be me an my Metcal for a while longer.

10/19/2000 11:55 AM
MKB	I have to depot stuff at work, I use the heat gun with a very sharp 14" wood chisel. Heat up the gun and chisel, and scrape away. The tip shape makes it very easy to remove small amounts of potting but you have to be VERY careful. Plus, one of our manufacturing people has ordered samples of a solvent that our epoxy manufacturer claims will dissolve and remove potting compounds without damaging electronics. I am very skeptical but I plan to try it anyway, I have about 30 devices I have to depot now! I will give updates when we get the solvent in and I try it out.

10/19/2000 11:55 AM

MKB

I have to depot stuff at work, I use the heat gun with a very sharp 14" wood chisel. Heat up the gun and chisel, and scrape away. The tip shape makes it very easy to remove small amounts of potting but you have to be VERY careful.

Plus, one of our manufacturing people has ordered samples of a solvent that our epoxy manufacturer claims will dissolve and remove potting compounds without damaging electronics. I am very skeptical but I plan to try it anyway, I have about 30 devices I have to depot now! I will give updates when we get the solvent in and I try it out.

10/19/2000 4:07 PM

Liam

quote:
"Plus, one of our manufacturing people has ordered samples of a solvent that our epoxy manufacturer claims will dissolve and remove potting compounds without damaging electronics."

If it's the stuff from Dynasolve, it's basically just DCM (dichloromethane). You need to warm it up slightly. It doesn't dissolve cured epoxy, but it does soften it and lesen the adhesion.

Liam

10/19/2000 7:23 PM
Don Symes	Chlorinated Hydrocarbon! Gloves, goggles, use OUTDOORS or under fume hood/exhaust fan. 'course I'm just a worrywart

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