Steve (and the rest of Technet),
LTNS! I've been extraordinarily busy lately. Good thing, I suppose.
Since you said "and we have never seen solderballs like this until we ran
the lead-free boards with the SAC 305 paste" then one can safely assume it
is related to the change, i.e., the lead-free paste. I would venture a guess
that the surface tension (much lower in LF alloys) plays a part in possibly
large areas of paste going liquidus then sluffing off in droplets. If you
could identify a particular assembly this happens consistently with, then
perhaps you could affix an inexpensive, i.e., "disposable" video cam to
watch it happen in the reflow zone. Even if you only get to see it once, it
would verify your suspicions. Another idea that struck me is to try a
competitor's paste and see if the symptom goes away, or tech support from
the original supplier gets smart suddenly?!
Regards,
Ed Popielarski
QTA Machine
27291 Jardines
Mission Viejo, Ca 92692
Ph: 949-581-6601
WWW.QTA.NET
"Nearly 50% of the population is below average intelligence!"
Me 2006
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, October 31, 2006 9:57 AM
To: [log in to unmask]
Subject: [TN] Bizzare Phenomena...
Mornin' All!
This morning I have seen something that I have never, ever have seen before.
It's been a little slow the past week, so we decided to do our maintenance
on our reflow ovens. After we opened the oven up, we found many, many
solderballs laying on the bottom of the oven right around zone 7 - 8, right
at the beginning of the spike zone. Check-out:
http://stevezeva.homestead.com/files/Oven_Solderballs.jpg
http://stevezeva.homestead.com/files/Oven_Solderballs_2.jpg
http://stevezeva.homestead.com/files/Oven_Solderballs_3.jpg
http://stevezeva.homestead.com/files/Oven_Solderballs_4.jpg
We've been having tombstoning problems when we've run the two lead-free jobs
that we have here. I've been working with the paste vendor sending my
profiles and plots, but I haven't been able to solve the problem. The
solderballs in the oven are lead-free solderballs.
We are using a Heller 1809, and my profile set-points are:
120 140 160 180 190 200 230 240 250
120 140 160 180 190 200 230 240 250
Belt speed 26 in per min
The paste is a SAC 305 with a water washable no-clean flux. I think my
profile is pretty reasonable, and the last board we ran is pretty standard,
.062" thick, with no bizzare copper planes. The board finish with both jobs
has been ENIG. The last job I ran we were tombstoning 0805's, the one before
that we were tombstoning 0402's. With both jobs we've had major tombstoning
problems. I've slowed the beltspeed down, sped it up, ramped up slower,
ramped up faster, changed this, changed that, but still haven't resolved my
tombstoning.
Of course, I'm the only one that's having this problem according to my paste
vendor...
I wouldn't have imagined that I would see the solderballs in the oven like
we have...
Have any of you ever seen something like this before?
-Steve Gregory-
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