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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