Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: How to get through the resin / potting to circuit board


Guru

Status: Offline
Posts: 964
Date:
How to get through the resin / potting to circuit board


Many of the car ECUs are just in a box with a lid held on by screws. Probably because they are located in the safe, dry passenger compartment. It seems most of the bike ECUs on the other hand are 'potted'. The circuit boards are placed in a hard plastic shell that is then filled with a liquid resin that 'hardens' into a rubbery substance with about the same consistency of a pencil eraser.

This protects the board from moisture, dust, and vibration. It also helps dissipate heat. Unfortunately it also makes it very hard to reverse engineer the board when you can't see what's inside.

I had this problem with the ZX-12r ECU. Fortunately I had done something like this years ago for a project I did at my job so I knew it could be done. It just takes a lot of time and patience.

Here is the ECU after I very carefully cut away the top of the outer plastic shell by making shallow cuts with a hand held hacksaw blade.



I left the bottom plastic piece in place so I would be able to smoothly slide the ECU back and forth across the drill press table. I used Dremel tool wire brushes in my bench top drill press. They are stiff enough to remove the resin but not hard enough to damage the components if your careful. They will clog up however. I ended up using about half a dozen of them.

I would set the drill at a height just below the level of the resin then slide the ecu back and forth against the brush till I had removed a layer then crank the drill down a bit and repeat the process.



Eventually you start running into parts that stick up and you have to work your way around those. The trick is to not get greedy or too impatient. You can run the brush right over the small surface mount parts like resistors and diodes. But you need to take care that you don't apply to much pressure or you will rub the value or part number paint off the parts. The whole point of this exercise is to be able to identify the part numbers of the ICs. You don't want to go to all this trouble and find you rubbed away the part number




After you get as much off the top as you can then peel off the bottom plastic and go at the bottom resin. There won't be as much resin and few if any parts that stick up to worry about. But you will have to hold it in your hand while you push it up against the brush.

It took me about 10 hours spread over several days but the results were worth it. By the way did I mention to take your time and not get greedy? I learned that the hard way after ripping off the crystal, the power supply regulator and various small electrolytic caps. Most the parts I was able to solder back on.





You will not be able to finish it a 100%, especially around any large components like driver transistors etc. I bought a pair of small picks like dental picks at the local hobby store. They work good to get into those tight spots to pull and scratch away the resin



The picks also work great as meter probes when you’re trying to trace out circuits. Just use some clip leads to connect them to your meter probes.

Also if you’re married this may not be a project for the living room.










__________________


Member

Status: Offline
Posts: 13
Date:

Nice work. :) Marc Salvisberg at Factory Pro has some sort of dip tank he uses to soften the stuff into slimy strips, more or less. I think it's mostly acetone. You could use that for finishing rather than the picks, and run little risk of the acetone damaging anything. You'll be able to finish removing the potting much more easily and with much less risk of damaging a part or removing the part number or value from components. Maybe get close with the brushes and then soak in acetone?

__________________


Guru

Status: Offline
Posts: 964
Date:

Thanks for the tip. I gave up on the solvent method after some early failures that were very messy / smelly. It's one thing to mess around with an acetone bath in a commercial / industrial setting and quite another to do it in your den. But as a final touch up to get rid of those last little bits its sounds like a good idea.



__________________


Member

Status: Offline
Posts: 13
Date:

Yes; I would absolutely NOT recommend using highly volatile organic solvents inside any enclosed space! :O

A well-ventilated garage, or even outdoors, would be better for your health and help alleviate the possibility of explosion or fire. I somehow doubt a significant other would be impressed with a burned-down house...

__________________


Member

Status: Offline
Posts: 5
Date:

You can use "BARDAHL Paint and gasted remover" and a soft cleaner brush.

There is my ER6n ECU without resin.

Attachments
__________________
www.infomayor.com


Newbie

Status: Offline
Posts: 4
Date:

The product that "easily" removes the epoxy resin is Methylene Chloride, which is also found in paint removing products as dgmcan mentioned.

I used it to remove the epoxy from a Y2K Busa ECM back in late 2000 or 2001.

I did manage to damage a few electrolytic caps when I was cleaning the board, but the chemical does make life a lot easier. The only drawback of the chemical is that it is corrosive, so watch how you handle it... and it takes a while to react with the resin.

__________________


Guru

Status: Offline
Posts: 964
Date:

Maybe I will give the Methylene Chloride a try. I tried some acetone the other day and it didn't seem to work very well at all.

__________________


Guru

Status: Offline
Posts: 2338
Date:

When removing the outer shell I found a hot air blower and even a hair dryer to be very helpful. Heat allows the plastics to be detached from the "rubbery stuff".

Also when removing the outer layers you can first heat it up with hot air blower and a knife and then use dremel or solvent for the rest.


__________________

When asking a question, you can also consider posting it to facebook:

http://www.facebook.com/ecueditorcom



Guru

Status: Offline
Posts: 1344
Date:

thanks for the tips,it cut about half the time off of the job if i was going in blind........marc

__________________

09 busa.????? now what....still got what it takes.......!

I got what you need...!
www.poweredbyford.com

www.marc@poweredbyford.com

 



Newbie

Status: Offline
Posts: 2
Date:

Does anyone know if the '01 GSXR600 ECU is "potted"

__________________


Member

Status: Offline
Posts: 5
Date:

hi guys does any1 have pictures honda ecu without epoxy

__________________


Member

Status: Offline
Posts: 5
Date:

to remove the epoxy use acetone

__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.

Tweet this page Post to Digg Post to Del.icio.us


Create your own FREE Forum
Report Abuse
Powered by ActiveBoard