HP Solder mask and MS111

[Bertho]

After reading a lot of solder mask removal procedures I have been trying to find a good solution for very old HP PCBs with gold plating. Apparently there are at least two different types: An extremely difficult "transparent" solder mask and a more regular green color. I have been testing different options. I tried to break it down by heating the PCB but the PCB itself broke down with the "transparent " mask unaffected!
"Jasco Premium paint & epoxy remover" removed the green mask in a day and started to affect the "transparent" one after three days but I big mess to work with and to remove afterwards,
I tried Methylene Chloride but no change after over a day.
I have a VERY old bottle with a little leftover MS111 that I bought to dissolve some ICs for failure analysis.
It stripped the transparent resist in an hour!
From the label it contains:
Methylene Chloride
Formic Acid
Acetic Acid
Phenol
The ratios are unknown.

I have too little left to do any serious testing.
Any suggestion of what to to easily add to regular Methylene Chloride to in effect create a DIY MS111?
Presumably it is easier to just bite the bullet and buy MS111.

I just checked the sample again. Beautiful perfectly clean gold with the solder mask floating in little pieces.
SUCCESS!

 

[Lino1406]

Phenol is a known ingredient of paint removal, it etches your skin as well

 

[Paruima]

I have successfully removed most but not all types of solder mask by boiling in sodium hydroxide. I had pretty good success by adding one pound of sodium hydroxide crystals with 2 liters of water. I raised the water temperature to 200 degrees farenheit for approximately 44 minutes then washed off the sodium hydroxide in cool water.

 

[rickbb]

boiling in sodium hydroxide.

Talk about etching your skin. :shock:

 

[butcher]

Eyes are very useful, and seeing is also valuable to recovery and refining, they may survive acid but they will not survive NaOH.

 

[Findm-Keepm]

HP famously uses Parylene, a very difficult to remove conformal coating.

Chemical Removal is the quickest. There is a solvent, Tetrahydrofuran, but it is prohibitively expensive. That what we used in the military for "gross" removal.

Mechanical Removal is slow - used to remove coating from one or two components. Usually, scraping and using a dental burr will remove enough for component removal.

Bake (overcure) in a oven at 400 degrees for days at a time will often make the Parylene somewhat separate from the substrate (longer for plexiglass!), but again, slow and costly.

I've soaked boards in various solvents to no avail myself, and usually feed entire boards to a band saw to cut out heavily plated areas, then use a toaster oven at it's highest setting (outdoors - fumes!!) to debond the parylene from the surface of the boards. It'll turn cloudy, then debond a bit. Standard CuCl processing after that. One HP Instrument controller left me with a 6 square inch foil.

There just isn't much economical sense in processing HP boards with parylene - sell them whole on eBay to the folks needing the boards or sell them to a board buyer.

 

[g_axelsson]

I too have fought with that conformal coating. Luckily enough most cards were only coated on the solder side... which makes for some beautiful cards. The plating is also quite thick, which isn't too bad.

I finally broke up the cleaned boards, put them in a bucket with copper chloride and forgot about it for a couple of years. When I found them the liquid had evaporated but copper in the boards were almost all turned into copper chloride even if the coating still covered the traces. A steel brush, a bucket of water and a lot of elbow grease and I could collect all the foils in the water at the end.






The pale green traces on the solder side are pale compared to normal cards thanks to the gold, copper is darker and creates darker traces.

Göran

 

[Johnny5]

Such a beautiful board! I several totes full of boards like that. Some years back I ran a bunch of them, and I was shocked at the volume of gold in the plating.
After having such a difficult time finding a buyer for my stuff, I am seriously considering processing everything myself.

 

[Paruima]

Talk about etching your skin. :shock:

Extreme care with safety glasses, gloves and vigilance!

 

[Paruima]

Eyes are very useful, and seeing is also valuable to recovery and refining, they may survive acid but they will not survive NaOH.

Won't touch the stuff without eye protection and full face shield.

 

[Bertho]

After reading a lot of solder mask removal procedures I have been trying to find a good solution for very old HP PCBs with gold plating. Apparently there are at least two different types: An extremely difficult "transparent" solder mask and a more regular green color. I have been testing different options. I tried to break it down by heating the PCB but the PCB itself broke down with the "transparent " mask unaffected!
"Jasco Premium paint & epoxy remover" removed the green mask in a day and started to affect the "transparent" one after three days but I big mess to work with and to remove afterwards,
I tried Methylene Chloride but no change after over a day.
I have a VERY old bottle with a little leftover MS111 that I bought to dissolve some ICs for failure analysis.
It stripped the transparent resist in an hour!
From the label it contains:
Methylene Chloride
Formic Acid
Acetic Acid
Phenol
The ratios are unknown.

I have too little left to do any serious testing.
Any suggestion of what to to easily add to regular Methylene Chloride to in effect create a DIY MS111?
Presumably it is easier to just bite the bullet and buy MS111.

I just checked the sample again. Beautiful perfectly clean gold with the solder mask floating in little pieces.
SUCCESS!

Update on the MS-111: I had to buy it for an unrelated project at my business. It is horribly expensive: basically $200 for a gallon and $200 for shipping inside the USA by ground and special truck. UPS will not handle it.
After being immersed for few hours, even the PCB itself was disintegrating! Definitely not cost-effective but it is an extremely effective solvent.

 

[cejohnsonsr1]

That’s way too much trouble. You can remove the mask with lye, but first you need to depopulate the board.