hi,

you can put posts on the pwb under your lcc-like device to lift it off of
the surface of the pwb.  this can be done with a dry film soldermask.  this
process is in common use.

phil crepeau

-----Original Message-----
From: VOLPE, RAY [mailto:[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