Doug
Yes and I can!
Bergendahl, C.G. and Dunn, B.D. Evaluation of Test Equipment for the
Detection of Contamination on Electronic Circuits, European Space Agency
Technical Memorandum ESA-STM-234, Paris (1984)
Brian
[log in to unmask] wrote:
>
> Brian,
> Was the ESTEC study you refer to ever published? If so, can you provide
> the reference?
>
> Doug Pauls
>
>
> *Brian Ellis <[log in to unmask]>*
> Sent by: TechNet <[log in to unmask]>
>
> 08/25/2009 01:17 AM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> Brian Ellis <[log in to unmask]>
>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: [TN] ROSE Equivalency Factors
>
>
>
>
>
>
>
>
> I agree with Doug. The European Space Agency (ESTEC) did a profound
> study with 4 different makes of tester and (I think) 6 different types
> of flux, cleaned according to manufacturers' recommendations and found
> there was absolutely zero correlation between them. It was impossible to
> determine a so-called equivalency factor (aka as fiddle factor or fudge
> factor) for any given instrument, as it varied greatly with different
> fluxes and different cleaning processes. The whole notion was dreamt up
> by NAFI in a nightmare; their testing was unscientific as they
> determined it for instruments very different for those used today with
> uncleaned boards, using a reference method that is, in itself,
> unscientific and imprecise.
>
> Forget the whole notion of equivalence because none exists and the
> figures were, in any case, determined for instruments that were marketed
> a quarter of a century ago and whose only resemblance to todays' ones is
> that they may bear the same name. The ONLY way of using ionic
> contamination testers is, during qualification, to determine the mean
> and the standard deviation of the residual contamination on assemblies
> deemed safe for the intended purpose, individually for each type of
> board you make, using YOUR instrument under standardised conditions.
> During manufacture, the mean should fit within the Gaussian curve
> determined during qualification. If it deviates in either direction,
> then you know that your process has changed somewhere along the line
> between goods-in and cleaning.
>
> If you have a certain book, Chapter 20 explains the danger of using
> equivalence factors and the use of mean/standard deviation for
> determining SAFE process control.
>
> Brian
>
> Richard Kraszewski wrote:
> > Can someone please refresh my memory and tell me which document has the
> > equivalency factors for the various ROSE testers? I seem to think that
> > it was the IPC TR 583, but I don't see them there. Believe it may have
> > been a Military document.
> >
> > Thanks
> >
> > Rich Kraszewski
> >
> >
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