Grant;

  I found this happen when we changed from 4% solids to 2% solids, solder
balls start appears at one specific area in the board, and we wouldn't be
able to eliminate the problem, I only reduced it by increasing the pre
heating temperature.The situation was exactily the same, I changed only the
flux and the other parameters were held constant.

Thanx

Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil


> -----Original Message-----
> From: Grant Emandien [SMTP:[log in to unmask]]
> Sent: 20 de Agosto de 1999 08:51
> To:   [log in to unmask]
> Subject:      [TN] Solder/Flux/ICT Issue
>
> Hi again,
> Thanks for all the input as it has now directed me towards fluxes (and
> control thereof) and ICT.
> Leading from one of the members advice of low residue flux I stumbled
> across
> this Kester comment:
> 'Flux selection does have some play as to the occurrence of solder balls.
> A
> rule of thumb is that the lower the solids content of the flux is the more
> solder balls will be noted when all other parameters are held constant.
> This
> is sort of a dilemma for us as a flux manufacturer in that if we increase
> the solids content, we will more than likely have an adverse impact on
> probe
> testing of final soldered assemblies. The aesthetics of the final soldered
> assembly will also be affected as you can imagine.'  This was posted in
> 1993
> so any idea on what has since transpired and is this statement still valid
> wrt the solids content?
> Geez, my research thusfar has brought an array of variables to this party
> such as test pin profiles and type, gold plating vs gold alloy, pin base
> material hardness, spring force etc. on the ICT aside. Nevertheless it is
> now beginning to get interesting.
> As a comment, I hope my research drives me away from introducing another
> process i.e. cleaning of assemblies hence and control of flux effluent (we
> are coincidentally reviewing ISO14000) etc. and rather focus on improving
> the existing process i.e. flux residue reduction (without cleaning) and
> ICT
> issues.
> Thanks again to all,
> Grant
>
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