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March 2004

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Subject:
From:
Mike McMonagle <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 4 Mar 2004 13:31:37 -0600
Content-Type:
text/plain
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text/plain (78 lines)
Cal,
        If it's an ongoing assembly, I'd get some dedicated selective
wave carriers made to mask the bottom side surface mount. The masking
process you're currently doing shouldn't be causing any of the potential
problems you are concerned about, but does consume a huge amount of
labor that could be directed to something more productive....

Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Cal Driscoll
Sent: Thursday, March 04, 2004 1:22 PM
To: [log in to unmask]
Subject: [TN] Removable masking/ Double sided reflow


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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