Charles Barker
04/16/97 11:27 AM

Eddie,

I do not have any experience with vias in pads (YET), thank goodness.

I think some things I would look at are:
1. Direction of these parts relative to the wave? Are the defects always on
trailing edges of parts, leading edges, or are the parts running with the
long axis parallel to the width of the wave?
2. Was the pad geometry enlarged any on the waved side? Sometimes a larger
pad will fix wave soldering problems.
3. How fast are you running the conveyor? How long is is the board being
exposed to the solder? Have you varied the conveyor speed?
4. What kind of wave(s) are you hitting it with? Turbulent, Rotary Chip,
etc.
5. What is your top side preheat temp? Solder pot temp? Angle of conveyor
to the wave?
6. Do the vias in question connect directly to an inner plane layer? Are
there thermal reliefs on those layers?
7. Have you done any cross sections? Do the via holes seem to be filling
with solder?
8. Are the boards HASL or Organic Coated?
9. Have the boards or coupons from the panels made with the boards been
solderability tested?

Good luck and keep us posted.

Charlie Barker
Mfg Engr
i-o.com

---------------------- Forwarded by Charles Barker/IO-US on 04/16/97 11:10
AM ---------------------------


TechNet @ ipc.org
04/16/97 12:35 PM


To:   TechNet @ ipc.org
cc:    (bcc: Charles Barker/IO-US)
Subject:  VIAS IN 0805 PADS WAVESOLDERING






Our companys design policy is not to put via sites in chip part pads. The
"B" stage will leak onto the surface pads during the lamination cycle. This
could be the cause of the problem you are experiencing.

______________________________ Forward Header _____________________________
_____
Subject: VIAS IN 0805 PADS WAVESOLDERING
Author:  [log in to unmask] at SMTPpost
Date:    4/16/97 8:23 AM


Hi,
Like everybody (?) we are using 0805 components in wavesoldering.
When there is a viahole in the pad, we see a number of very thin
solderjoints (almost undetectable visually) and even non-soldered
components.
Is there an experience in the field about allowing or not allowing this
configuration, and about via-hole size and via-position in the pad to
reduce or prevent defects ?
Eddie Van Horen  [log in to unmask]



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