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ELECTRICAL DISCHARGE MACHINING OF INK RESERVOIR THROUGH HOLES IN THERMAL INK JET DEVICES

IP.com Disclosure Number: IPCOM000027720D
Original Publication Date: 1999-Feb-28
Included in the Prior Art Database: 2004-Apr-09
Document File: 4 page(s) / 197K

Publishing Venue

Xerox Disclosure Journal

Abstract

Disclosed is the use of electrical discharge machining or electrochemical machining to form substantially vertical, walled-through holes for ink filling in thermal ink jet channel wafers. 16 XEROX DISCLOSURE JOURNAL - Vol. 24, No. 1 JanuarylFebruary 1999

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XEROX DISCLOSURE JOURNAL

ELECTRICAL DISCHARGE MACHINING OF INK RESERVOIR THROUGH HOLES IN THERMAL INK JET DEVICES
Joel A. Kubby
William J. Greene
James F. O'Neill

Proposed Classification
U. S. C1. 347/026 Int. C1. B41j 2/165

24 26

_I

XEROX DISCLOSURE JOURNAL - Vol. 24, No. 1 JanuaryFebruary 1999 15

-L

-w-

FIG. 7

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ELECTRICAL DISCHARGE MACHINING OF INK RESERVOIR THROUGH HOLES IN THERMAL INK JET DEVICES (Cont'd)

\\-

FIG. 2

Disclosed is the use of electrical discharge machining or electrochemical machining to form substantially vertical, walled-through holes for ink filling in thermal ink jet channel wafers.

16 XEROX DISCLOSURE JOURNAL - Vol. 24, No. 1 JanuarylFebruary 1999

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

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ELECTRICAL DISCHARGE MACHINING OF INK RESERVOIR THROUGH HOLES IN THERMAL INK JET DEVICES (Cont'd)

Advantages with respect to presently used orientation dependent through-etch include:
a) consuming less lateral real estate in the chip,
b) allowing direct ink path connections to the channels, and
c) eliminating the sharp, fragile edge of the inlet.

The current thermal ink jet channel wafer uses orientation dependent wet chemical etching to provide a through-hole to connect the ink channels on one side of a wafer to the ink supply on the other side of the wafer. A disadvantage of orientation wet etching through the thickness of a (100) wafer is the large amount of real estate that is consumed by the sloped <111> side walls that are at an angle of 54.7 degrees with respect to the wafer surface. As shown in Figure 1, the sloped side walls 20 and 22 of through-hole 40 in ink
reservoir 18 require a mask opening to be wider than the fmal orifice dimension W by an amount 21 where:
t

    I= tan(54.7") to etch through a wafer of thickness t. For a 500 microns thick wafer, the sloped side walls consume 708 microns, nearly a millimeter. The real estate consumed on the channel wafer is indicated in Figure 2. In Figure 2, channel wafer 30 is composed of a plurality of channels 32, ink reservoirs 18 and 19 and wire bond via 34 and 36. The situation is even worse for etching a through-hole in (110) oriented silicon, where the sloped <111> side walls are at an angle of thirty-five degrees with respect to the wafer surface, requiring over 1,170 microns of real estate to be consumed.

An alternative to wet orientation dependent etching is to use Electrical-Discharge- Machining (EDM) or ElectroChemical Machining (ECM) to obtain a vertical wall through-hole. In the EDM technique, a series of rapidly recurring electrical discharges between an electrode (the cutting tool, typically graphite) and the work piece causes minute particles of material to be removed by melting and vaporization. The technique has tolerances in the 5 to 50 microns range, and has been used to drill a 50 microns hole through a 330 microns thick silicon wafer. Some larger cuts have also be...