What type of soldermask are you using?

We have been using PTFE pwbs with LPI soldermask for a number of years now.
We based our acceptance on the IPC-HF-318 (??) specification.  But there
are still some gray (or is it grey?) areas which require disposition.

With LPI, bubbles that do not expose the conductor should be acceptable
provided the height of the maskant is not critical to the next assembly
(like under small chip caps).   Of course this assumes that the problem is
also not in the vicinity of the very sensitive RF circuitry.


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Phil Bavaro
QUALCOMM Inc.                                        Telephone:  (619) 658-2542
6255 Lusk Blvd.                                        Fax:           (619)
658-1584
San Diego, CA 92121                                Email:
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At 3:41 PM 5/2/96, Thomas Stewart wrote:
>Hi all,
>Does anyone have experience with soldermask on teflon?
>
>Is there any information or specification on acceptance criteria for
>bubbles in mask along traces for teflon material specifically?
>
>We have very good adhesion, but on a random basis we will get very small
>(less than .005") hard surfaced bubbles. They will not propagate or break
>with heat.
>
>We use a very gentle bake cycle -- 6 hours with 2 ramps, but the skin on
>the mask just will not allow all the volatiles to escape without causing
>the soldermask to bubble.
>
>
>-------------------------------------------------------------------------------
>Tom Stewart
>Speedy Circuits                              Phone: 714-891-9441
>5292 System Dr.                              Fax:   714-895-8485
>Huntington Beach, Ca  92649                  Email: [log in to unmask]
>-------------------------------------------------------------------------------