To My Esteemed Colleagues,
An interesting quandary has been posed to me from the folks in purchasing, and I wanted to poll the opinions of others in the industry before rendering my thoughts on this matter.
It has been brought to my attention that there maybe some question to the acceptance of PTH copper plating thickness based on the following findings/factors:
- PCB surface and PTH are plated with gold flash over Cu.
- My company manufactured approx. 200K assemblies based on the approval of qualification samples and in the absence of any detailed specifications
- The board manufacturer started with 1/2 oz Cu foil.
- Measurements extracted from samples on hand indicate a PTH Cu plating thickness of .228 mils ~ .293 mils and PTH Au plating thickness of .208 mils ~ .260 mils.
It is my understanding that the Cu plating process adds approx. 1 oz Cu/sq. ft to the finished Cu plating thickness, and therefore have concerns about a lack of sufficient Cu plating in the PTH.
Furthermore, IPC-6012A (Table 3-2), minimum allowable Cu plating on the surface and holes for Class II PCB's is 18 um- 20 um.
Understanding all of the above, I would appreciate any feedback on the following concerns:
a. If IPC standards were not insisted upon with the PCB manufacturer, is it fair for my company to insist that it should be followed.
b. Are there any potential circuit failure issues pertaining to the stated Cu/Au plating thickness' in the PTH.
c. If starting with 1/2 oz Cu foil, what is the industry norm finished Cu plating thickness.
I thank you all for your participation in advance.
Hugh
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