I generally agree with what you have written here, when speaking of
no-clean processing, But I believe the test method is still valid for
water soluble fluxes.

And I wonder how you would evaluate process results for no-clean
fluxing. How can one provide assurance that the processed flux residues
are the same as the day the flux process was qualified.


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of
> Mike Fenner
> Sent: Thursday, July 17, 2003 10:49 AM
> To: [log in to unmask]
> Subject: Re: [TN] Ionograph reading for No clean v/s aqueous
> processed (wa ter soluble flux)
>
>
> Could the 50 ug figure relate to uncleaned boards which have
> been put into the Ionograph?
>
> If so the number is meaningless as a measure of reliability
> or anything else when evaluated against the number for a
> cleaned board. The Ionograph was developed as a means of
> process control for cleaning rosin based fluxes that met a
> now obsolete military flux specification. The best you could
> say is that it is probably an indicator for the amount of no
> clean flux present. No clean fluxes are defined as harmless
> if the residue meets certain criteria, none of which includes
> amounts of residual extractable ionics.
>
> If the number is for a cleaned assembly then all we can
> really say for sure is that the boards have a lot more
> extractable ionics on them than they could have, [as amply
> demonstrated by the fact that the other techniques get lower numbers].
>
> If you were using a high solids rosin based RMA flux (say
> 35%) of the type around when the Ionograph was invented, and
> put an uncleaned board into the Ionograph it would likely go
> off scale, the total extractables would be huge. But RMA
> fluxes are considered safe if uncleaned. Poorly cleaned they
> may not be safe and that was the point of the test: to
> provide a means of monitoring cleaning process effectiveness.
>
>
> Regards
>
> Mike Fenner
>
> Applications Engineer, European Operations
> Indium Corporation
> T: + 44 1908 580 400
> M: + 44 7810 526 317
> F: + 44 1908 580 411
> E: [log in to unmask]
> W: www.indium.com
> Pb-free: www.Pb-Free.com
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of
> Carroll, George
> Sent: Tuesday, July 15, 2003 9:09 PM
> To: [log in to unmask]
> Subject: Re: [TN] Ionograph reading for No clean v/s aqueous
> processed (wa ter soluble flux)
>
>
> Ken,
> As the previous respondents have indicated, Ionograph results
> shouldn't be used as a go-no-go.  Taking the process
> approach, what were previous results from this vendor?  from
> other vendors providing similar boards?  Are there components
> that would tend to hold flux under or near them?  That could
> contribute to field reliability issues.  There may be those
> that disagree with me, but 50 sounds a bit steep in
> comparison with no-clean boards that I've measured.
>
> George
>

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