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PHOTOMASK DEFINED LASER MACHINING

IP.com Disclosure Number: IPCOM000025325D
Original Publication Date: 1984-Oct-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 117K

Publishing Venue

Xerox Disclosure Journal

Abstract

The use of high power lasers in precision machining operations is now widespread. The technology is limited, however, in one important respect; viz., the precision with which features can be located is limited to the precision of the mechanical transport of the laser or alternatively of the workpiece. This limit would not be important were it not desirable to effect the transport rapidly. Using a single spindle printed circuit board NC drilling head, for example, the hole location tolerances are at best +/- O.OO1'l. (Refer to IPS Printed Wiring Design Guide, Number 4.2.1, "Plated Through Hole Interconnections", Table 1, p. 8). For many applications, these tolerances are unacceptable.

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Page 1 of 2

XEROX DISCLOSURE JOURNAL

PHOTOMASK DEFINED LASER MACHINING Richard Kellerman
Jerry G. Black

  0.005 'I NOM I

Proposed Classification
U.S. CI. 148/14 Int. C1. C2 Id 1 /48

FIG: 1

4 L0.004"D.NOM

0.0 2 I!Jg.#gJ

TYf? CLEARANCE HOLE

Volume 9 Number 5 September/October 1984

295

[This page contains 1 picture or other non-text object]

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PHOTOMASK DEFINED LASER MACHINING (Cont'd)

The use of high power lasers in precision machining operations is now widespread. The technology is limited, however, in one important respect; viz., the precision with which features can be located is limited to the precision of the mechanical transport of the laser or alternatively of the workpiece. This limit would not be important were it not desirable to effect the transport rapidly. Using a single spindle printed circuit board NC drilling head, for example, the hole location tolerances are at best +/- O.OO1'l. (Refer to IPS Printed Wiring Design Guide, Number 4.2.1, "Plated Through Hole Interconnections", Table 1, p. 8). For many applications, these tolerances are unacceptable.

Photomask defined laser machining provides the solution to the related problems of tight tolerance/dimension requirements and layer- to-lay er reg is tra tion. This may be accomplished by depositing upon the surface of the workpiece (which is generally in the form of a flat plate) a layer of a metal highly reflective to the laser radiation. This metallic layer is then photopatterned and etched. The mask so formed is then used to define the action of the laser beam which may be considerably larger than the mask features. In this manner, the location tolerances for the laser tool can be relaxed in proportion to the beam size. At the completion of the machining operations, the mask can be stripped or, if desired, can be left in place in perfect registration with the machined features.

Referring to Figure 1, the fabrication of any array of holes 12 in a fluorinated ethylene propylene (FEP) film 10 is shown. The goal was to produce an array of holes in a metallic conductor 16 in registration with an array of holes 12 in a supporting insulator 10.

The starting material 10 consists of a 0.005" thick sheet o...