Dear Netters ,

have a problem down south here , if you would bear with me for a moment
please :

Some decade ago with kind support of esteemed Members here we've established
(validated) nice and steady SMT process ;
which we've happily got through SM-785 on some seven months of reliability
cycling ; all fine.

Now, that decade or so after the initial spec combo compromising bare board
spec (substrate) ,
one of Indiana creams and usual painful component selection that validation
proved faultless , with high sigma yields , negligible field incidence .

The board spec , which was old local telco origin (with million+/an) used to
be with couple decades back , which I've thus proved adopted , reads :
IPC class II , 1oz (35um) copper , UL 94 FR4 Class V-0 , marked with
fabricators UL approval logo and date code
Board Thickness 1.55+/- 0.15 , double sided copper , Liquid Photo , matte,
dark green, 3-20um Ni, 0.3-0.8 Au (ENIG, aka flash)

Now, the crux being 0.3-0.8 ENIG, bit taller than usual :
because our boards serve the storage life, solder, carbon pill silicon pad
switching and card insert (downloads, weekly, 5 year design life) fingers :
with median of 0.4um Au I've validated it's fine for all above, 0.5 better,
but I am not greedy ; any leaps in plate density ?

In past I have been able to hold this bit slower/thicker ENIG plate spec
without any drama , but nowadays in this hectic age both supplier and
purchasing is trying to convince me sub 0.1um Au (lowest IPC standard being
in blissful ignorance slammed over my poor head continuously) would get us
through grandly :
an opinion which I (lonely) don't share .

Hence , to put an end to this misery I have been assigned the CAPA privilege
of addressing Learned Forum for those who can do,
that is keep ENIG within the 0.3-0.8um , median 0.4 is fine in standard
plate, denser the better .

Seen offered 0.5um ENIG in past , hope it still holds somewhere out there.

Current supplier ex HK base , mainland plants, is unfortunately too
fluctuating to remain sustainable partner in our volumes , being 1-2 M/an :
this is a real supplier switch - inevitable, appreciate your consideration .
Direct fabricators and/or recommendations please, would not like to bristle
Jack any more than necessary (if he's still The Cerberus Re).
Open (Net) insights on ENIG process ceiling appreciated, different results
of same thickness measuring methods and/or lab to lab result repeatability
experiences would be kind as well, please.

Much obliged , thx a lot

Paul Klasek
Sr.De.Eng.
http://www.resmed.com
Sydney

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