Electronics > Beginners
surface finish thickness
KL27x:
This thread brings back a bad memory on a collaboration. I did the circuit design and firmware, but due to time constraints, physical quirks, and the sheer quantities involved, my client wanted a more experienced PCB guy. The housing was done by another company.
The board was in two parts, with some gold fingers making a contact pressure between the boards. I identified a problem with the prototype because the soldermask on the board encroached on the board with the gold plated contacts. The obvious solution is to enlarge the opening in the soldermask on the bottom board or to reduce the size of the pcb on the top board, so that everything fits without the soldermask getting in between.
I don't know what the big deal was, but he insisted to add carbon to the pads to make them thicker. I knew this would cause other issues and I explained it best I can that this was unacceptable. The housing was already done, and it didn't allow for this. I wanted to strangle him through the phone. He finally conceded to not add carbon. He claimed he would thicken the pads with gold plating. So I said sure, but only gold (knowing there's no way he is going to add gold of any thickness to the board out of his own contracted fees).
Well, the boards arrived, and they had carbon on the pads. I eventually respun the PCB myself, but not before it cost my client $100,000.
langwadt:
--- Quote from: ataradov on January 13, 2019, 04:04:37 am ---
--- Quote ---ENIG General Applications The minimum immersion gold thickness shall be 0.05 µm [2.0 µin] at -4 sigma (standard deviation)
--- End quote ---
So the minimum recommended by the standard is 2.0 µin. It seems reasonable that prototyping service will do bare minimum or less. I'm sure AllPcb will do whatever is requested for real orders.
--- End quote ---
the IPC i looked at said min. 2uin for default ENIG, but min. 1.58uin can be used for soldering only
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