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Date: | Tue, 5 May 2020 02:25:26 -0500 |
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After a bit of advice from the TechNet massive.
The nickel layer on an ENIG finished flexi PCB stiffens the copper and can lead to cracking on a flexi, or so I am led to believe. Where a flex design includes both interconnect functionality and SMT circuitry, how do people specify the surface finish? Ideally you want the nickel thickness to err on the side of the lowest nickel thickness within IPC-4552 and not the upper end of the standard tolerance, don't you? But does that then potentially impair the solderability and reliability of the assembly for other reasons?
Can suppliers even adequately control Nickel to say 1-3um, rather than 1.3-6um?
I've seen papers that suggest using higher phosphorous levels or using columnar rather than laminar nickel deposition, but these seem to be proprietary solutions (pardon the pun) and not universal panacea that any supplier could offer.
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