Hi Ben!
Your picture is up! Go to:
http://www.stevezeva.homestead.com
and look for "Tombstone".
Boy the ol' page is getting a workout today!
Kind regards,
-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
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| | "Gumpert, Ben" |
| | <ben.gumpert@LMCO|
| | .COM> |
| | Sent by: TechNet |
| | <[log in to unmask]>|
| | |
| | |
| | 06/08/2005 12:01 |
| | PM |
| | Please respond to|
| | TechNet E-Mail |
| | Forum; Please |
| | respond to |
| | "Gumpert, Ben" |
| | |
|---------+---------------------------->
>--------------------------------------------------------------------------------------------------------------|
| |
| To: [log in to unmask] |
| cc: |
| Subject: Re: [TN] mystery tombstone cause |
>--------------------------------------------------------------------------------------------------------------|
Various component locations have different sides connected to ground or
power planes. The connections to these planes are made directly by vias
from the outside ends of the pads (vias are masked), so there are no traces
running from the pads on either side. I have asked Stephen to post an image
showing the pad configuration. This image will show a large component right
next to a row of 0306 capacitors, but tombstones are in the same direction
on other sides of the component, and a board run without any components
except the 0306 capacitors shows the same results.
In my reflow process, I am ramping at about 1°C per second to about 165°C,
slowing ramp rate (soak period) to increase another 10°C over the next
minute, then ramping to peak.
Ben
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair K. Hogg
Sent: Wednesday, June 08, 2005 12:12 PM
To: [log in to unmask]
Subject: Re: [TN] mystery tombstone cause
Is one side of the component connected to a voltage or ground plane? It
could be that the copper in the plane is taking heat away from the pad. One
solution is to separate the pad from the plane by use of a small short
trace.
Also, if one pad has a large trace connecting to it, and one has a small
trace, the large trace can also take heat away. One way to solve this is to
neck down the trace right next to the pad.
Blair
>>> [log in to unmask] 06/08/05 08:09AM >>>
Technetters,
I have several SMT board styles which give me some trouble with 0306
capacitor tombstones, and through many attempts to reduce the number of
these defects, I have found a condition that I can not seem to attribute a
cause to. I have found that across a board, all the tombstones tend to lift
in the same direction (for components in the same orientation).
I have looked at the build process, but different board styles result in
tombstones in different directions, so I believe the cause to be board
related. I have looked at solder mask registration (misregistration occurs
in various directions), power/ground plane connections by pad (changes from
location to location), and solder bumps due to HASL (wicked pads have
similar results), and nothing has led me to a root cause.
Any ideas???
Thanks,
Ben Gumpert
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