Today I was debugging a product with a membrane/keypad, I noticed that the contacts of the flat cable were black, ie not plated, I never saw this before, I am used to the FFC cables only
Is there any problem related with this kind of termination? I suppose is for lowering the price and, as it has a considerable resistance, it is possible to “carbonize” the contact and have a bigger resistance? if a high voltage is applied, like an ESD, because is what I see, high resistance if measured form the contact, and low if measured form the track itself (just before the contact)
Thank you,
Edit, when I said black, it was not shinny or bare metal look, cleaning with alcohol did not remove the black, but scrapping did it, so the ESD test did create that layer, I though it was a different kind (lower cost) termination.
I did not know that there are 2 options for traces on membrane panels, copper and silver that are actually printed.
As you can see, contacts are not clear and shine, it is not copper, so I think silver should be, light and the angle of the photo does not help, but is the looks exactly as a pencils tip.
In any case, is bare metal that, somehow*, has a thin layer of something.
The only sympton was a set of keys that shared one pin of the matrix, due to higher resitance, but the other pins also had tens of ohms, just not enough to fail.
