Chris
The concerns I'd have would be:
1) any moisture sensitive parts on the bottom side that are getting
stressed by the heat of the wave?
2) what is that quantity of solder masking material doing to your
cleaner?  I'd guess it's clogging your filters if you re-circulate the
media, at best you are dumping a fair bit of material down the drain.
It might make sense to do for a few, but not in any quantity...

I'm sure it's a lot faster, so I can understand why the operator would
want to try it (although we would be unhappy they tried it without
proper pre-checks).

A couple of alternatives that might work better:
 - get fixtures made to mask the bottom side SMT stuff - we do this and
love it.  No masking, the SMT is paste attached, good times on building
the boards.
 - or glue the parts on and simply wave 'em so long as there are none
that will suffer from the heat

have fun!

regards,

Graham Collins
Process Engineer,
Northrop Grumman Canada Corporation
Halifax
(902) 873-2000 ext 6215

>>> [log in to unmask] 03/04/04 03:22PM >>>
Hello All-
WOW !!! two postings from me in two days...

Here is the case:
We run a double sided reflow process.
We Print, Place, and Reflow the bottom of the boards..

Then

Print, paste, and reflow the top side.

Since the bottom side is mostly discrete and Resistor networks (unlike
the
one pictured on Steve's Site) it works well.

For the through hole components we hand insert and solder them.


I just went down to the wave soldering room and found the
operator...........

Covering  the bottom side components  with removable masking material
(Chemtronics Brand) and sending the boards through wave.

Once Soldered...he removes the masking and all looks well.


Question(s);
1) Is this an acceptable practice?
2) What documentation is available to support or disclaim this?
3) What reliability issues are there due to any thermal mismatch?
4) Any leaching of masking material into the solder join causing poor
joint
integrity?

Please advise,

Cal

P.s. Steve be a fountain; not a drain...keep up the excellent work

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