I have been asked to determine what the best practice is for depaneling PWAs from an array (more than one PWA per panel run down the assembly line), or in other words...

....how should we be depanelizing PWAs, a) v-score, b) pin router, or c) mouse bite/punch.

I do have a personal opinion (listed below), but my experience was with commercial Class 2 and not Hi-rel Class 3 hardware.  I am looking for input from others that have years of experience in the Hi-rel arena:

a) V-scoring was always the easiest but required that the score go all the way across the panel.  The result was that there were a few glass bundles (.012" approx) which were sheared left over while the area of the v-score was smoothly finished by the original router.  The mechanical stress, if performed using the round blade to shear while supporting the v-score from the bottom, in minimal.  The solder joints keep away is a minimum of .080" away from the top edge of the V, but ceramic caps might need further distances and special orientation.  Proper singulation method is important so this is not a high volume production type method.  I have always discouraged jump scoring.

b) The pin router method results in a nicely milled edge but it requires ESD controls (ionized air) as well as excellent FOD controls (vacuum for the dust) to control the process.  The resultant board edge is identical to what a PWB fabricator would supply and one advantage is that the copper to board edge pull back area is less than with a v-score.  We don't have room for tooling pins to hold the boards so vacuum hold down is a requirement and that applies mechanical stress to the PWA as well.  This method is suited well to high volume.

c) The mouse bite punch method leaves the entire board edge thickness exposed for glass bundles and is the least desired due to this.  If the mouse bites are not spaced optimally, the punch or nipping process can impart the highest stresses of all of these methods.  The edge copper pull back is from the edge of the mouse bite holes which is close to the amount needed for v-scoring.  The other drawback is that some people tend to want to flex the mouse bites to failure and that causes unknown but excessive stresses.

Please feel free to respond with your preferences as well as point out any disagreements you might have given that this process needs to be used with hi-rel hardware (non-space, but definitely airborne).


Thanks in advance,

Phil
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