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January 2018

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Subject:
From:
Wayne Showers <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Showers <[log in to unmask]>
Date:
Mon, 22 Jan 2018 18:25:09 -0600
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IAg is not a horrible idea for a surface finish, but it does come with its own warts.
1) Creep Corrosion: DFR Solutions has done much research on this.  Primary recommendation to mitigate it is to paste all component pads whether populated or not.
>> https://link.springer.com/article/10.1007/s11664-004-0025-x

2) Move away from WS fluxes.  Because RMA fluxes utilize the Rosin as a suspension agent, you will get must less secondary issues with the flux penetrating into unwanted areas which include under the solder mask, between plating layers (This is critical for immersion silver as the silver immersion process creates micro-voids and micro-pitting of the underlying copper.)

3) Storage and Handling: Always wear clean cotton or latex gloves (preferred).  Cotton can trap oils and if the gloves are cleaned, many detergents and fabric softeners have phosphor and sulfur compounds in them.
And Silver saver paper is a must.  Silica desiccant and IAg are not compatible.  

And as a final aside, unfortunately the days of Tin-Lead are limited thanks to the tail wagging the dog over in the EU with Electronics as the target.  In 22 years of Electronics Manufacturing, I have had 4 issues with bad ENIG or ENEPIG plating, and Roughly 40-50 issues with flux penetration or entrapment including 1 recall that totaled over $1.5 Million Dollars.

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