Electronics Forum | Wed Nov 10 10:41:57 EST 2010 | esoderberg
subject board fabrication calls for .05 -.125um of gold over 2 - 5 um of nickel. When doing double sided reflow using same profile, parts of the gold are tarnishing and causing test pad failures. any ideas as to the cause?
Electronics Forum | Thu Nov 11 14:29:18 EST 2010 | davef
When you say 'tarnished,' is that based on: * Appearance of the gold over-plate * That you can't get good contact during ATE processing ... OR ... * Something else?
Electronics Forum | Thu Nov 11 15:55:53 EST 2010 | davef
We guess the nickle has a rougher that normal finish AND the gold is at or below your specification. The nickle bumps are poking through the gold and are oxidized, preventing contact with you ATE probes. If this is correct, it would be interesting
Electronics Forum | Wed Nov 10 16:03:07 EST 2010 | davef
Were the gold surfaces acceptable: * At incoming inspection * After first reflow ... How do know this issue was caused by the second reflow?
Electronics Forum | Wed Nov 10 16:33:09 EST 2010 | esoderberg
I don't. However we perform inline ICT and functional testing on both sides and the first side has never had issues. It is only when we flip the board and start reflowing on the bottom side.
Electronics Forum | Thu Nov 11 15:11:16 EST 2010 | esoderberg
Getting adaquate contact with the test fixture. I have given a board to our vendor to perform analysis. Maybe we will see something there.
Electronics Forum | Fri Nov 26 05:22:44 EST 2010 | 89jeong
Hello Esoderberg. Did you get the analyis report from your vendor? If so, could you pls share it wiht us? Based on my experiance, this issue may be caused by the Au plating. You need to ask your vendor to check the Au thickness or Au plating proces
Electronics Forum | Fri Nov 26 09:01:52 EST 2010 | stepheniii
An independant analysis might also be warrented. And what I've seen is that you can't save money on PCB's. If you go with cheap providers you end up with boards that cost big time in other ways.
Electronics Forum | Thu Dec 20 19:41:27 EST 2001 | ianchan
I called a cuppa of indutrial friends, and they concluded that the flex-PCB in question, was being subject too high a oven-baking temperature of 100deg-C...50~60deg-C oven-baking temperature would be more appropriate for flex-PCB, due to its very pad
Electronics Forum | Sat Oct 24 13:03:20 EDT 2015 | mikekeens
With regards to PCB surface finish I would recommend Electroless Nickel Immersion Gold (ENIG) because of the long shelf life, tarnish resistance, RoHS-compliance, and easy soldering compared to other surface finishes. http://www.surfacemountprocess.
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