I think LCOA did a study of hole wall roughness way back. I might still have
a copy somewhere. Or maybe there's some info on LCOA's website www.lcoa.com.

geoff layhe

> ----------
> From:         Dennis Fritz[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;[log in to unmask]
> Sent:         04 August 2000 04:06
> To:   [log in to unmask]
> Subject:      Re: [TN] Hole wall roughness
>
> 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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