V4 - Plating of PCIe card edge connector not specified
About the required gold contacts on the SPEC board:
The PCI express specifications require 0.7um gold over 1.2um nickel (PCI express card electromechanical specification rev 2.0, page 78, below figure 5-5) (CERN library, CERN only).
It is actually not sure if this is the actual specification for the
thickness. The text is actually about Connector Environmental
Requirements (Durability (mating/unmating) rating of 50 cycles, 7 year
field life) and actually reads:
| To be sure that the environmental tests measure the stability of the connector, the add-in cards used
shall have edge finger tabs with a minimum plating thickness of 30 microinches of gold over
50 microinches of nickel for the environmental test purpose only. |
This amount of gold can be applied using an electrolytic gold plating method. This is the method for gold plating for the edge connector contacts. The SPEC design files have all features for this plating process.
However, the SPEC manufacturing
only mentions ENIG gold with a much thinner gold plating specification
despite the fact that the design has been also been made for
| Surface Finish: | ENIG - Electroless Nickel / Immersion Gold according to IPC-4552 |
| Thicknesses:: | Ni: 3μm min - 6μm max / Au: 0.05μm min - 0.125μm max |
- Add in PCB specification the correct metallisation process and specification that will arrive at the Environmental Requirements as specified.
Issue signalled by a subcontractor producing the card.