Couple of comments on hole wall roughness:

1. Seems I remember a systematic measurement of roughness, using cross
section photos to measure the actual lenghth of the dielectric/copper plate
interface with something like a map maker uses to estimate length of road on
a map.  This length is divided by the laminate thickness to get a number
bigger than 1.0.    A 1.03 hole would be smoother than a 1.08 hole.  Think
this came from a big study of drill parameters - entry material, feeds and
speeds, number of hits, etc.  Anyone got the details of quantifying
"roughness" from that study?

2. Holes are rougher when measured at a 45 degree angle to the weave
directions, than the normal cross sections measured with the weave.  Try it -
cross section holes at the !:30/7:30 and 4:30/10:30 locations rather than
6:00/12:00 and 3:00/9:00.  Reason - the drill is cutting the glass bundles on
an angle there, and tears the glass bundle worse than perpendicular bundle
cuts

Denny Fritz
MacDermid.

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