Whoa, Kelly! Saponifiers and polyimide flex are a big No! No! combination. That is,
unless you want to etch holes in the substrate. OK, I may exaggerate, but polyimide is
chemically degraded at pHs above about 9,5.
My recommendation: water-soluble flux/paste (not too aggressive), hold flexes in
fixtures with stainless springs looped in holes for that purpose, so that they remain
taut, load fixtures in baskets at c. 20° to the vertical, high-throughput batch washer
(not dishwasher, unless you have very low throughput of just a couple of circuits per
hour), dry in machine with rotary air knives. This will comfortably meet all specs
without damage.
Brian
"Kelly M. Schriver" wrote:
> Hi Nancy -
>
> To begin with, the cleaning media is driven by the particular flux you are
> using. This, in turn, will drive the issue of what equipment you may be
> able to use for the process. I have had good success removing RMA residues
> from flex circuits with quite a number of blended solvents in vapor
> degreasers and conveyorized spray systems. Size of the flex assembly must
> obviously be considered - there are a number of suppliers who can provide
> cleaning baskets to restrain small flexes for processing thru conveyorized
> cleaning systems. Manual cleaning would not be my first choice if I were
> dealing with a high reliability article, particularly if it were to be
> conformal coated.
>
> Another possibility might be one of the saponifiers, in either a heated bath
> or a "dishwasher" type system.
>
> If you are not currently using a low residue ("no clean") flux, might that
> be a possibility? If this is a consideration, and you plan to conformal
> coat or use adhesives on the assembly, be sure to verify full compatibility
> of the flux residues and the specific coating material you intend to use
> before proceeding.
>
> Contact me directly if I can be of assistance.
>
> Regards - Kelly
>
> -----Original Message-----
> From: Nancy M. H. Holloway <[log in to unmask]>
> To: [log in to unmask] <[log in to unmask]>
> Date: Tuesday, January 04, 2000 10:57 AM
> Subject: [TN] cleaning flex circuits
>
> >TechNet,
> >
> > What is the best technique to clean flux off of a polyimide flex circuit
> >after population? Thus far, we have been cleaning the flex circuits with
> >alcohol but it is time consuming and tedious. We use a machine to clean
> >rigid boards, but I am hesitant to use it for our flex circuits. How are
> >you all cleaning your soldered flexible printed circuit boards.
> >
> > Thanks,
> > Nancy
> >
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