How to process mobile phone keypads and flexes

[VanMarco]

Hello!
I've been processing mobile phone boards (empty) in CUCL2. those were regular Fr4 BOARDS.
I do caustic soda to remove comformal coating followed by cucl2.
Now though, i have a massive amount of these flexes and keypads that are on a soft membrane.
I already know that caustic does not expose any copper. So i suspect that these would be impervious to CuCl2, so whats the best way to process these?
I take that as they are mostly gold plated surface i could do hcl+oxidizer (not nitric, a little bit of tin is present)

Thanks

 

[Christian333]

Hello!
I've been processing mobile phone boards (empty) in CUCL2. those were regular Fr4 BOARDS.
I do caustic soda to remove comformal coating followed by cucl2.
Now though, i have a massive amount of these flexes and keypads that are on a soft membrane.
I already know that caustic does not expose any copper. So i suspect that these would be impervious to CuCl2, so whats the best way to process these?
I take that as they are mostly gold plated surface i could do hcl+oxidizer (not nitric, a little bit of tin is present)

Thanks

Process the same as gold plated boards, in CuCl2 base metal leach.

Janie

 

[VanMarco]

and it will get to the copper beneath the gold even though no exposed copper area is visible?

 

[Yggdrasil]

and it will get to the copper beneath the gold even though no exposed copper area is visible?

There is always some microscopic exposed area, and if the plating is not too thick it will even work through the Gold layer.

 

[GoIdman]

Hello!
I've been processing mobile phone boards (empty) in CUCL2. those were regular Fr4 BOARDS.
I do caustic soda to remove comformal coating followed by cucl2.
Now though, i have a massive amount of these flexes and keypads that are on a soft membrane.
I already know that caustic does not expose any copper. So i suspect that these would be impervious to CuCl2, so whats the best way to process these?
I take that as they are mostly gold plated surface i could do hcl+oxidizer (not nitric, a little bit of tin is present)

Thanks

Hi,

The older boards, with the green solder mask were plated ones, almost every board I have found from older mobiles were plated, except these brown and yellow flexible pads. These are mostly ENIG plating so you can drop them in AP and just forget it. You will have to process a large amount of foil type keypads for a significant amount of gold.

I only process these when I heave a very large amount (personally I hate these keypads for their low yield) but its always good for learning and experiments.

Be safe.

Pete

 

[VanMarco]

Thanks, will try. I do have a whole box, thousands of them. I am happy with the gold, but my true happiness is to not have a giant box of junk in the way too! Will update with pictures.

 

[Golddigger76]

You can feed the mylars through a paper shreder before you put them in your hydrochloric acid.

This will expose more copper and give the strips of mylar a zig zag fold when they come out of the bottom of the shreder that will keep them from sticking together so the acid can do its job.

You can do the same thing with keyboard mylars that contain silver before you soak them in nitric acid.

It's a lot of work and the returns are a small amount of gold or silver unless you have a ton or more but it is a good learning experience.