Check IPC 7525. There is a section in there about intrusive reflow. Two
Print stencils are good for situations where there is not enough real estate
for overprint. We have several customers using Two Print Stencils.
William E. Coleman
Vice President - Technology
Photo Stencil An ISO 9001 Registered Company
4725 Centennial Blvd.
Colorado Springs, CO 80919
Phone # 719-535-8528
Fax # 719-599-4334
Cell # 719-331-2433
email: [log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: Morse, Carrie [SMTP:[log in to unmask]]
Sent: Friday, April 11, 2003 9:37 AM
To: [log in to unmask]
Subject: Re: [TN] Apertures for intrusive reflow
You might get bridging. You might not.
If there is sufficient surface tension to pull the solderpaste into
the hole, then, you
probably won't get bridging. If the surface tension is
insufficient, you may end up with a large solder ball between the pins. I
think that scenario is more likely than the bridge considering the wide
pitch. The only way to really know is to try it. I'd also be concerned
about some solder joints getting more solder than others (one scavenging
from the other)
-Carrie
-----Original Message-----
From: Tempea, Ioan [mailto:[log in to unmask]]
Sent: Friday, April 11, 2003 8:22 AM
To: [log in to unmask]
Subject: [TN] Apertures for intrusive reflow
Hi Technos,
I am investigating intrusive reflow and big part of the topic is OK
for me.
I learned how to calculate the volume of the paste, I even tried the
process
on several assemblies, all OK.
Now I'm running into a board with less real estate, so not so much
space to
do the overprinting. According to my calculations the apertures for
this
particular TH connector would overlap. It's a 78.7 mils pitch.
The question is: could I overlap the apertures and print paste all
over,
bridging between the pins? Since we deal with large pitch and we're
talking
liquid paste flowing towards the holes, would this not create solder
bridges
after reflow?
Thanks for your insights,
Ioan
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