mask over gold foil

[Panamahatman]

At first I missed that the gold fingers are actually larger foils that run across the front and back of these cards but are covered by the green mask. I accidentally scratched away some of the mask when I used cutters to remove a component (lower right in photo). I don't want to damage the foils by using mechanical force against the mask.

I tried Acetone, and some 22k test solution on the mask, which did not disturb it so I believe that this is true mask and not some other type of film covering. I found old threads and google searches where they discussed using a chemical solution such as methylene chloride. I only have 6 of these cards so I'll pass on the methylene chloride - expensive and overly toxic imo.

Plan B: Use heat to remove connector. Use an xacto blade to cut through the mask down to the pcb at the gold foil boundaries. I have not tried AP yet to remove foils, but what do y'all think - can AP wick beneath 1 cm width of foil to dissolve base metals and free the foil given sufficient time? Thanks,

PHM

 

[Lino1406]

Normally the mask is used to prevent plating gold under it

 

[rickbb]

can AP wick beneath 1 cm width of foil to dissolve base metals and free the foil given sufficient time? Thanks,

PHM

If by sufficient time being potentially weeks then yes, eventually the mask will peel off.

 

[Panamahatman]

thanks

 

[Qajaq]

try this if you can do it real save:
remove the connector and everything else.
Than put the cards in a bath of hot caustic soda (minutes - up to an hour, depends on the type/thickness of the mask).
Rinse the masks with water, eventually a bit of brushing is needed. But beleve me the mask will peel off.

Be very, very carefull, hot caustic soda is nasty stuff and a serious danger. Fume hood/outdoor gloves & googles is not enough.
You have to be sure to have the Knowledge doing this method in a right and safety manner. And please read martijn´s post!
And think about if it´s worth it!
Incidentally - the same applies to using AP Solution although it is not the same dangerous staff like hot caustic soda.

 

[Martijn]

Gold plating covered with mask is usually a mistake by the manufacturer or an extra layer to protect against oxidizing of copper traces in a very aggressive atmosphere.
Gold underneath mask has no purpose and will most of the times be ENIG plating.

Gold used for contactpoints that are changed out often are the thickest.

That ENIG plating is not worth the risk of getting blind from one drop of lye or worse from working with hot lye!!!
Especially for a new member!!!! Please think about what you advise to who.

Yes it's shiny, but worth going after?

Soak it a little longer in AP.
Collect a bunch of these and process separately to get a yield percentage.
If you can actually measure that tiny amount.

Martijn.

 

[Qajaq]

hi martin
i understand your statement! My warning maybe was a bit short. I will do better next time. And edited my post.
thanks for your input

 

[macfixer01]

Some very good brands such as HP and Tektronix, and the old Sound Blaster cards for example often have gold traces. Some will be thin ENIG, some is not. The original purpose of solder mask was to protect the bare copper traces from oxidation, and to prevent the masked areas of the board from being coated with solder or forming bridges between nearby pads during flow soldering. Normal green/red/blue/etc solder mask (not conformal coatings) can be removed by soaking the board in hot Lye (sodium hydroxide) solution then brushing off the remainder. Lye is dangerous because it’s caustic and is a strong base, it will dissolve your skin and turn the fats into soap. Use proper protective gear, especially safety glasses and gloves. Also hot Lye will etch glass over time, and will vigorously attack aluminum as well. So it’s best not to use glass and definitely not an aluminum container.