Technetters':

Thanks go out to all who have responded so far.I will add a caveat and state
that LPISM is not an issue because the circuit boards do not have any solder
mask on them. The boards are constructed in a way that all the traces are on
the internal layers and only the pads are on the external surfaces.

I am re-running the post with the hopes of soliciting more responses,
however I will be out of the office next week (8/6-8/11) so I will not be
able to report on any findings until 8/13 or shortly thereafter.

Thanks go out to all for their two-cents worth.

Bill Kasprzak
Moog Inc., Electronic Assembly Engineering

RE-RUN ......

> Technetters'
>
> I've recently run into a problem with Wavesoldering some circuit boards
> where I am having problems getting topside solder joints. The process that
> I'm running has the topside of the board at 195-200 F just prior to the
> solder wave. My conveyor speed is 4.0 fpm. My fluxer is a spray fluxer.
> The
> board is a .062 - 6 layer board that has an aluminum heat sink on it. I
> feel
> that my process is set correctly.
>
> The original process that previously used on these boards was very
> successful when we used an OA water soluble flux. This process was on that
> I
> qualified many years ago to  J-Std-001A for Class 3 assemblies.
>
> On these circuit boards, I'm trying to use a No Clean Lo Activity level
> flux
> that is water washable. Because I have new equipment for wavesoldering, I
> was hoping to not have to do a re-qualification process for our level 3
> assemblies. Because our new equipment has much better controls than our
> old
> equipment I thought that it would be easy to solder these boards with an
> LO
> active flux. Well, my initial pass has been a disaster so far. There are
> three pictures that I'm looking for comments on. They are located on
> Steve's
> Webpage at http://stevezeva.homestead.com. (A thousand thanks go out to
> Steve Gregory for providing a site for posting the pictures.) Two of the
> pictures, called Bare Pad and Bare Pad2 show a condition that I can
> describe
> but I don't know if this condition has a name. In those pictures, there is
> a
> heavier coat of solder on the pad, but it seems to form a concentric ring
> on
> the pad.The extremities of the pads, both toward the outside and the
> inside,
> show a tinned surface but it appears to be much thinner. To me, it seems
> like these thin areas do not readily solder. It seems like this thin area
> is
> barrier that can only be overcome with a very strong OA flux. This may
> explain why I did not have a problem before. The other picture shows
> another
> condition that I see in various places on the bare board where there are
> protrusions on the inside of the PTH's. This appears to be trapped
> volitiles
> that were being expulsed during the HASL process.
>
> I'm trying to determine if I have a board problem or a process problem.
>
> Is it unreasonable for me to think that this board can be soldered with a
> no-clean (but water washable) LO activity level flux?
>
> Any help or comments would be greatly appreciated.
>
> Bill Kasprzak
> Moog Inc., Electronic Assembly Engineering
>

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