Hello Victor,
Typically, SWSP technology is very "hit and miss"
so "hands on experience" plays a very big part in achieving a successful design
on the first pass. The need for such pallets is to allow "mixed technology" to
be wave soldered after SMT without the use of adhesives. We can get into lengthy
discussion here on all of the options of how to build a PCB assembly, but I will
limit the scope to your question.
The pallet presents a significant heat sink to the
thermal processes involved in Wave Soldering. Most significantly in the preheat
section, but it does have some effect in the wave section as well. The "best"
solution to these problems is a good pallet design, but sometimes you simply
cannot overcome the forces of thermodynamics, so having the proper equipment
with enhanced preheat (convection bottom and top) is the only practical
solution.
The solder wave presents significant limitations on
changing the thermal characteristics. Your only alternative here is to use the
chip wave of a dual solder pot machine. I did an IR thermal imaging
experiment with McDonald-Douglas years back to resolve a "partial fill" problem
they had. What we determined it the thermal load of the ground plane inside the
PCB was great enough to freeze the solder while it was coming up through the
PTH. More preheat did not help this condition because the actual failure was
occurring at solder melt temp (or slightly below to be more exact). Using the
chip wave to overcome the load worked like a charm! In your case, even subtle
modifications to the pallet can reduce local thermal loads and effect such
vertical fillet characteristics. It's hard to judge this without seeing the
actual process and making measurements.
Please let me know if I can help in any
way.
Regards,
Ed Popielarski
QTA Machine
10 Mc Laren, Ste D
Irvine, Ca.
92618
Phone:949-581-6601
Fax: 949-581-2448
Cel: 949-337-2578
----- Original Message -----
Sent: Thursday, April 10, 2003 11:13
AM
Subject: RE: [TN] selective wave solder
pallets(1)
Ed,
My interest in Selective Wave Solder Pallets, SWSP,
stems from an artifact that I occasionally see during Destructive Analysis,
cross section, of axial leaded components, Pin In Hole, associated with SWSP
Process Technology. This is what peeked my interest.
Understanding the need and design for such a pallet. I see PTH's
with partial vertical fill solder fillet.
victor,
Hi Victor,
I'd be more than happy to discuss this with you
by phone. Frankly, it could get too "wordy" for e-mail.
If you'd include your phone number, I'd be
happy to call you. If it's better for you, feel free to call me directly as
well.
Regards,
Ed Popielarski
QTA Machine
10 Mc Laren, Ste D
Irvine, Ca.
92618
Phone:949-581-6601
Fax: 949-581-2448
Cel: 949-337-2578
----- Original Message -----
Sent: Thursday, April 10, 2003 8:44
AM
Subject: RE: [TN] selective wave
solder pallets
Fellow TechNetters:
I have an interest in learning more about Selective
Wave Solder Pallets. Can this information be shared with
me.
Victor,
Hi Tenison,
Please contact:
GARLAND SERVICE COMPANY
JIM
GLEASON
Phone:
972-494-1911
Fax:972-276-0972
714 SHEPERD
DR.
GARLAND, TX, 75042
I've copied Jim herein as well.
Regards,
Ed Popielarski
QTA Machine
10 Mc
Laren, Ste D
Irvine, Ca. 92618
Phone:949-581-6601
Fax:
949-581-2448
Cel: 949-337-2578
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