Hi Technetters
Some time we have to qualify new materials and processes as solder
resist, fluxer, cleaning processes and conformal coating. To assure the
performance we are performing ROSE (sometimes SIR and el.chem.migration
tests). Annoying: the single materials often are qualified itself, but
because our process we feel the need to qualify the whole combination.
Question: is there "open files" comunity to share our experiences?
Bernhard Wanner
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----------
Von: Sherman Banks[SMTP:[log in to unmask]]
Gesendet: Dienstag, 22. Juni 1999 16:15
An: [log in to unmask]
Betreff: Re: [TN] Cleanliness Problem
Our experience and testing with Ion Chromotography and SIR show
that by
using an RMA flux and Semiaqueous cleaner (in particular
Qualitek 730 paste,
Kester 185 liquid flux, and Axarel 38 cleaning solution) the
residues,
while present, are not detrimental to the performance. This has
been
supported by 10's, if not hundred's of thousands of units in the
field, in
outdoor environments throughout the world with no known
corrosion problems.
In general we do NOT conformally coat our boards. In fact, we
have just
about satisfied our only customer that requires it, that it is
not
necessary.
By the way some of our ceramic disc antennas are approximately 2
inches in
diameter and sit flush on the board - we also use a 6 mil
stencil.
Hope this helps - If you want to contact me off line I would be
glad to go
into more detail.
REGARDS
Sherman Banks
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408/481-6047
> -----Original Message-----
> From: VOLPE, RAY [SMTP:[log in to unmask]]
> Sent: Monday, June 21, 1999 6:49 AM
> To: [log in to unmask]
> Subject: [TN] Cleanliness Problem
>
> Fellow TechNetters:
>
> I have a ceramic resonator surface mounted on a (Type 1) FR-4
PCB in a
> Class 2 application. The flush pads (gold flash plated) on the
underside
> of the component have castellations similar ta an LCC. There
is almost
> no component to PCB surface clearance. We are using an .008
mil stencil
> to apply the solder paste then reflow solder. We believe the
> insufficient clearance under this part is limiting the
cleaning
> solutions ability to adequately flush the solder residues from
under the
> part. We have had failures due to residue trapped beneath this
> component. When the component was removed and cleaned
underneath then
> resoldered to the board at a rework station, the part would
function
> normally. I am looking for, and would very much appreciate
some success
> stories on similar parts or ideas to fix this problem. We can
not comply
> to J-STD-001 as required, because we can not demonstrate
satisfactory
> cleaning.
>
> Some inhouse suggestions have been:
> * Increase stencil thickness (raise part)
> * Drill holes under part in PCB (no board, no
entrapment)
>
> Any validity to these ideas ?
>
> Thanks in advance,
>
> Ray Volpe
> [log in to unmask]
> (609) 583-9400 x286
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