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PRECISION PRESS-FIT DRILL TO FINISH HOLE SIZE (D2FHS)

IP.com Disclosure Number: IPCOM000249638D
Publication Date: 2017-Mar-10
Document File: 3 page(s) / 436K

Publishing Venue

The IP.com Prior Art Database

Related People

Jeff Bullard: AUTHOR [+2]

Abstract

A process is presented to manufacture a plated thru hole with a tolerance much tighter than the industry standard (+/-2 mils) using precision drill to finish hole size (D2FHS) techniques. A demonstrated capability (< +/- 0.5 mils) eclipses projected next-generation incremental tolerances of +/-1.5 mils. In essence, tighter connector press-fit hole tolerances become a non-issue.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

Copyright 2017 Cisco Systems, Inc. 1

PRECISION PRESS-FIT DRILL TO FINISH HOLE SIZE (D2FHS)

AUTHORS:

Jeff Bullard David Senk

CISCO SYSTEMS, INC.

ABSTRACT

A process is presented to manufacture a plated thru hole with a tolerance much

tighter than the industry standard (+/-2 mils) using precision drill to finish hole size

(D2FHS) techniques. A demonstrated capability (< +/- 0.5 mils) eclipses projected next-

generation incremental tolerances of +/-1.5 mils. In essence, tighter connector press-fit

hole tolerances become a non-issue.

DETAILED DESCRIPTION

Press-fit holes in printed circuit boards (PCBs) commonly have their drilled hole

size (DHS), finished hole size (FHS) and tolerance specified by connector manufacturers.

As signal speeds increase, there has been a transition to smaller FHS's and tighter

tolerances. Some PCB suppliers have made incremental improvements to their plated

through hole (PTH) processes. However, there are cases where even more advanced

PCB suppliers are unable to meet the FHS and tolerance mandated by the connector

(socket) supplier.

Tapered drilling, step drilling, shallow back drilling and pre-scoring are known

methods to achieve a tighter-tolerance press-fit hole. The drawback to tapered drilling is

that a tapered drill bit is required, which is non-standard to PCB manufacturers.

Moreover, tapered drilling does not address tighter press-fit hole tolerances, it only

addresses the "bump" of excessive plating at the knee of the hole (tapered drilling is

performed prior to plating, not after). Step drilling is essentially the same as tapered

drilling in that it only addresses the "bump" at the knee of the hole; it does not improve

press-fit hole tolerance throughout the compliant portion of the PTH. Shallow back

Copyright 2017 Cisco Systems, Inc. 2

drilling completely removes the knee of the hole along with the O/L pad, but does not

improve press-fit hole tolerance. Pre-scoring is a re-work methodology that does not

address press-fit hole tolerance.

Precisio...