Daan,

        Can you define exactly what the platings are, in terms of thickness
     and purity if any, ie Ni is 4-6uM with 0.5uM Au etc!! and what the
     solders etc are Is the problem effect the whole batch, or just some of
     the boards?

        Regarding your specific questions:-

        Prebake of boards will enhance any diffusion of Cu through the Ni
     and into the Au, I cant see why this would effect solderabilty, but
     may effect reliability  The degree of diffusion etc will be related to
     time and temp of prebake and the thickness and quality of the Ni
     plating.

        Effect of previous soldering operations would all effect the
     diffusion as above

        I assume that as long as the solder paste is relatively active it
     should work fine on Ni-Au as HASL

        Have you done any surface analysis of the pads? sounds like they
     are contaminated with something, either from the plating, storage
     handling, or even within your own facility and process.


        I think we need more info, and you should get some basic surface
     analysis of the pads themselves.

                Roger
                Motorola AIEG


______________________________ Reply Separator _________________________________
Subject: [TN] soldering to immersion gold boards
Author:  "TechNet E-Mail Forum." <[log in to unmask]> at #email
Date:    10/09/99 14:17


Hi Technet,

I'm having some problems lately with soldering of pcb's with an electroless
nickel/ immersion gold conductor finishing, which brings me (after some
discussions with our board supplier) to the following questions :
Is solderability influenced by pre-baking the boards ? Does the first soldering
step have an effect on solderability for the second soldering step (double sided
reflow) ? How about the time between all these thermal excursions ?
Is it possible that a solder paste that performs excellent with HASL-boards (and
normally also with immersion gold boards) is a bad choice for soldering to
immersion gold ?

Greetings,

Daan Terstegge
Unclassified mail

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