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 [log in to unmask]