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DESIGN OF INK INLET SLOT FOR A PRINTHEAD

IP.com Disclosure Number: IPCOM000027648D
Original Publication Date: 1998-Jun-30
Included in the Prior Art Database: 2004-Apr-08
Document File: 4 page(s) / 177K

Publishing Venue

Xerox Disclosure Journal

Abstract

Thermal ink jet devices may be fabricated using two silicon wafers such that one wafer (the heater wafer) contains the heaters and electronics, and the other wafer (the channel wafer), contains the channels and ink inlet slots. On each wafer pair, there are typically

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XEROX DISCLOSURE JOURNAL

DESIGN OF INK INLET SLOT FOR A PRINTHEAD
Gary A. Kneezel
Almon P. Fisher

Proposed Classification -U. S. C1.347/085

Int. C1. B41j 2/175

FIG. 7

Thermal ink jet devices may be fabricated using two silicon wafers such that one wafer (the heater wafer) contains the heaters and electronics, and the other wafer (the channel wafer), contains the channels and ink inlet slots. On each wafer pair, there are typically

f 1

XEROX DISCLOSURE JOURNAL - Vol. 23, No. 3 May/June 1998 137

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DESIGN OF INK INLET SLOT FOR A PRINTHEAD (CONT'D)

many thermal ink jet die sites, so that when the wafers are precisely bonded together face to face and diced apart, many thermal ink jet die modules are produced. The fabrication and geometry of the channel plate is typically accomplished by Orientation Dependent Etching (ODE). In a preferred embodiment of this process, the triangular-shaped channel grooves and the ink inlet slot are etched from the channel side of the wafer. As a result, the ink inlet slot is tapered such that it is much wider on the channel side than it is on the ink inlet side. If the wafer thickness is t, the amount of taper on each side of the ink inlet slot is ,/m. This results in inefficiently used die module real estate which becomes important when attempting to minimize the die module size. One potential way to make the die module smaller is to make the ink inlet slot width narrower. However, the ink flow must not be overly restricted.

FIG. 1 is a sketch of the cross-section of an ink jet die module formed by the etch process described above. The heater die is the large rectangle at the bottom. Coated on the heater die 10 is a patterned polyimide layer 12 which encloses the heater in a pit to allow more efficient bubble expansion without blowing the bubble out at the end of the channel 14 so that air is allowed to enter. The polyimide layer 12 is also patterned to allow ink flow around a plug 16 of silicon which occurs between the channel structure and the large ink
reservoir 18. The channel die 20 is the upper structure having the etched channel and reservoir features. Also shown is the ink inlet gasket 22.

In order to minimize the cost of the thermal ink jet die module, it is desirable to minimize the width of the device (e + f + g + h) so that more die sites will fit on the wafer pair. As
indicated in the caption to FIG. 1, the channel length h is determined by optimizing the drop ejecting performance of the transducer. The reservoir width g is determined by the minimum allowable ink inlet 8 width c (to allow adequate ink flow) plus the total taper

a. The width of the rear bond f needs to be wide enough to allow a reliable bond between the heater die 10 and channel die 20. The wire bond shelfe must be wide enough so that the wire bonding tool can have clearance to reach the bond pad in area a. The other requirement is that it must be possible to m...