I used 2 years before a Customized selective soldering German machine 
     (INERTEC) to solder a specific aplication with conectors and coils in 
     automotive boards.
     The process was no-Clean alcohol base Flux Cobar 390-XR, and in the 
     solder pot I've got a mix nitrogen + formic acid to realy minimize the 
     solder dross.
     To obtain a good wetting was necessary increase the solder pot 
     temperature since 250°C to 310°C, and also was required make a control 
     with the Pb/Sn alloy (Cuantitative Chemical analisis of 13 elements).
     
     Suerte
     F. Briceno
     
     
     


______________________________ Reply Separator _________________________________
Subject: Re: [TN] Selective Wave Solder Pallet Problems
Author:  Aric Parr <[log in to unmask]> at INTERNET
Date:    07/28/1999 7:38 AM


Do you have room for solder thieves? They work pretty well for fixing these 
shorts.
     
Take a sheet of paper (thermal FAX or Ph paper depending upon flux type) and 
tape it to the top side of the pallet. Run it through the fluxer and remove 
it without preheating. Look at your spray pattern. Is the pallet lip (or 
component lead) masking the shorted area?
     
Aric Parr
Sr. Process Engineer
Eaton Corporation
1400 S. Livernois
PO Box 5020
Rochester Hills, MI 48308-5020
248 608 7780
[log in to unmask]
---------- Original Text ----------
     
From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 7/27/99 10:36 PM:
     
Here are some more "outside the envelope" suggestions:
     
1.   Try rotating the board within the pallet 45 degrees.  It works wonders 
for wavesoldering and solderpaste printing but usually is not an option for 
most situations.  Who knows, you might have a 24 inch wide wavesolder.
     
2.   Try increasing the angle of the conveyor rails and if that isn't 
possible, try to do it within your pallet.  The idea is to bring the 
trouble area of the part to the lowest possible location so that there is a 
minimal lip (or pallet thickness) right there.
     
3.  Try removing the Omega wave paddles and sealing up the holes if you 
have an Electrovert machine.  The holes in the nozzle cause turbulence at 
the surface and has been shown to contribute to bridging.  You can tell if 
this applies to your situation if your defects occur consistently within a 
certain geographical region across the nozzle in the neighborhood of the 
two holes.
     
4.  Try slowing down the conveyor speed (after lowering the preheater 
temps) to reduce the "snap back" force a little.
     
5.  Use press fit  for the connectors and then selectively solder the PGAs 
using semi-automated solder pots system (Airvac for example)  with a 
programmable conveyor so that the exiting direction of travel from the 
solderpot is vertical primarily.  This is fairly common but requires design 
changes.
     
All too often we see questions asked and suggestions made, but far to 
infrequently do we see the solutions reported on the TechNet for everyone's 
benefit.  If you do solve this one, please send out an email to let us know 
what you did.
     
Hope this helped....
     
Phil
     
>        -----Original Message-----
>        From:   Ryan Jennens [SMTP:[log in to unmask]] 
>        Sent:   Monday, July 26, 1999 9:36 PM
>        To:     [log in to unmask]
>        Subject:        [TN] Selective Wave Solder Pallet Problems 
>
>        Hey all-
>
>            We use selective wave solder pallets extensively to solder 
>through-hole leads, as almost all our boards are mixed tech.  A couple typ 
>boards consistently show a single short on the trailing edge of large 
>through-hole connectors.  One board always shorts on the trailing pins of a 
>PGA socket, while the other always shorts on the trailing edge of a
>40-pin dual-row female header.  No amount of tweaking the wave machine 
>settings affects the short.  My theory is this:  When the solder leaves the 
>larger pallet openings, it has nothing to "snap" to.  Therefore, it "snaps" 
>to the last couple of pins it leaves.  I have made sure that the solder 
>flows off the back of the wave at the same speed as the conveyer.  Has 
>anybody else seen, or heard, of this problem with selective solder pallets? 
>The advantages of reflowing bottom-side components make wave soldering the 
>whole bottom-side unfeasible.  Speaking with the pallet house has left us 
>with grooved pallet bottoms and chamfered openings; but the problem 
>remains.  Is there a way to alter the selective wave solder pallet openings 
>to avoid these "snap-back" shorts?
     
Phil Bavaro
     
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