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Date: | Thu, 18 Apr 96 14:41:10 EST |
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Question. When you mention breakout do you mean drilled hole beyond
the pad diameter away from the trace? (Differentiating drilled into
the trace area as "break in"?) I have seen (a long time ago with
difunctional) 1 oz copper connections with "break in" create thermal
opens (intermittent opens).
Groovy
______________________________ Reply Separator _________________________________
Subject: RE:Annular ring breakout
Author: [log in to unmask] at SMTPLINK-HADCO
Date: 4/18/96 11:32 AM
The reason for annular ring orginated in pre-MIL-P-55110 Signal Corps spec.
that reuqired it in order to get a good solder fillet around the teminals
that were staked into every hole to mount resistors, capacitors and tube
sockets.
Annular ring breakout is of no consequence in many test that have been run in
the world. In one study that I am aware of the boards were 10 layer with 1
oz. copper; the board thicknesses were .060, 090 and .125; breakouts were
none, 90 degrees and 180 degrees; hole sizes were .018 and .036; testiing was
1000cycles (-40 to 125) and 3 solder dips at 266 deg C. The evaluations were
by electrical test and microsection. Results were that there was no
significant difference between any of the three breakout types.
The breakouts in this case were all oriented by offsetting drill rather than
random as might be experience in a printed board. The test, also did not
test if the breakout occurred at the trace-to-hole intersection. I
understand that one of the groups is doing this test
presentl.
Phil Hinton
Hinton PWB Engineering
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