Hold on!  Did you say that these components are plastic or ceramic?

If the components are plastic then I would seriously caution against using
any halides (Chlorine, Fluorine, etc.) like HCl to clean them.  The
semiconductor industry moved away from the use of halides in plastic
assembly operations many years ago.  The chlorine loves to destroy the
aluminum wire bond pads.  Nearly all bad plating can be "fixed" with lead
tinning fluxes which are halide free.  Just when you find something that
works great someone comes along and tells you not to use it.  That's why
they pay you manufacturing types the big bucks.  Cause every time you learn
to jump higher they raise the bar.

If the components are ceramic with a glass seal then the HCl is likely to
cause severe glass attack which will render it conductive between leads.
Not good.

If the components are ceramic with brazed leads then the HCl will likely
cause a galvanic reaction between the gold portion of the lead and the
soldered portion.  This can cause major problems when you go to re-tin the
leads.  Again retinning (hot solder dipping) with an organic acid "halide
free" flux should solve it.

If the components are "unsolderable" then return them.  If you have had them
for years then I believe you need to solder dip the leads to replace the
"bad plating" with a fresh coat of hot solder.  This can get expensive and
you may find it cheaper to toss out the components.

Thats my 2 cents worth.  Hope it helps a bit.

Russ Winslow
Six Sigma
(Lead tinning services)

-----Original Message-----
From: Kelly M. Schriver <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, November 13, 1998 8:40 AM
Subject: Re: [TN] Assy: QFP leadframe tin-lead finish


>Hi Jerry & Dave & All -
>
>Another possibility:  If the lead frame on the devices you're dealing with
was
>PLATED and not reflowed promptly after, then that may be the answer to your
>problem rather than any alloy combination.  Most of the tin/lead platings
lose
>their solderability rapidly after application unless reflowed and cleaned
>immediately after plating.
>
>One additional test that you might try, in addition to an alternate flux,
>might be to try a "bright dip", then rinse, flux and solder the parts
>immediately.  Most of the bright dips are a 1 to 3%  HCl solution which
will
>do a pretty quick job of deoxidizing the parts.  As above, this surface
loses
>its solderability rather quickly and isn't something you would want to do
for
>production.
>
>I think most of us have seen some fairly significant variances in finish
>alloys over the years, even on parts supplied from the same manufacturer.
>Availability of improved fluxes has probably done more to ease concerns and
>difficulties encountered in the military/government sector of the industry
>than anything else in recent years.
>
>Regards - Kelly

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################