Graham,
Do you have access to the study results from NPL?  I would like to see that
study.  I would like to know what the effects are of too much/little flux
applied.  Also, do you know how flux density plays a part in solder joint
reliability?

Thanks in advance,
Rob Watson
Sanmina Corp. Plant 10
Durham, NC


Graham Naisbitt wrote:

>  Neil,
>
> I presume from your posting that you are not cleaning after soldering.
>
> I would strongly recommend that you try and keep the amount of flux applied
> under some control. As all fluxes leave residues, the way in which these
> react can lead to unpredictable or at least undesirable reliability issues.
>
> The NPL in the UK have completed a study which shows the amount of flux
> used, grossly affects reliability.
>
> Of course if the product is of low consequence then this may not be
> relevant. However, if you are producing something that is HiRel or Safety
> Critical, then maybe it is relevant.
>
> Might be a good idea to then validate your production process to yield the
> best results and then keep it under control. Try IPC-J-STD-001 Appendix
> D.Regards,
> Graham Naisbitt [log in to unmask] Concoat Ltd
> Alasan House, Albany Park
> CAMBERLEY GU15 2PL UK Tel: +44 (0) 1276 691100  Fax: +44 (0) 1276 691227