Cutting by use of rotating axially moving tool – Processes – Bit detachable
Patent
1986-10-14
1988-11-01
Abrams, Neil
Cutting by use of rotating axially moving tool
Processes
Bit detachable
264155, 427 96, 408 56, B23B 5106, B23B 3500
Patent
active
047814950
ABSTRACT:
Thru-holes are drilled in a printed circuit board panel having alternating dielectric layers and electrically conductive layers. A water soluble dry film lubricant sheet is placed adjacent an electrically conductive outer layer of the panel prior to drilling thru-holes through the panel with a rotary drill. The drill surface is lubricated while forming a clean thru-hole from contact between the drill and the lubricant. The dry film lubricant generally may comprise a water soluble lubricant hardened to a solid or semi-solid dry film-form and impregnated in a carrier such as a porous paper sheet. In one embodiment, the dry film lubricant includes a water soluble lubricant such as dipropylene glycol, a non-ionic surfactant, and a wax-like hardener. Following drilling of the thru-holes, the dry film lubricant sheet is removed, and the thru-holes can be rinsed in an aqueous alkaline solution. The thru-holes are then plated with an electrically conductive metal for forming electrical contacts between the metalized thru-holes and the electrically conductive layers of the panel. The dry film lubricant extends drill life and produces a clean thru-hole that prevents epoxy smear and avoids the prior art use of harsh chemical treatment following drilling to otherwise remove dielectric smear or fibers that might extend into the thru-hole and disrupt the continuity of the later-formed electrical contact.
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Lubra Sheet Corp. Laboratory Report, by A. J. Berlin, Ph.D., Dated Sep. 2, 1987.
Foster John W.
Hatch William R.
Abrams Neil
Lubra Sheet Corp.
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