Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-02-23
2003-12-16
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06663231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monolithic nozzle assembly for fluid formed using a mono-crystalline silicon wafer, and a method for manufacturing the same by continuous self-alignment.
2. Description of the Related Art
A laminated ink jet recording head disclosed in EP 0 659 562 A2 is shown in FIG.
1
A. As shown in
FIG. 1A
, the laminated ink jet recording head has a nozzle plate
101
with a nozzle
100
, three plates
201
a
,
201
b
and
201
c
with communication holes, a plate
301
with a pressure producing chamber
300
, and a vibration plate
400
, which are stacked in sequence. Ink contained in an ink tank
800
flows through an inlet
700
into a reservoir chamber
600
a
, and is temporarily stored in the reservoir chamber
600
a
. As the ink flows through an ink inlet
600
c
and the communication hole
600
b
into the pressure producing chamber
300
, the ink tank
800
fills with ink. A filter
900
for filtering the ink supplied from the outside is located on the top of the ink tank
800
. The vibration plate
400
has piezoelectric vibration elements, so that a predetermined pressure can be applied to the ink filling the pressure producing chamber
300
according to a voltage signal applied to the piezoelectric vibration elements. As a result, ink is discharged out of the nozzle
100
through the communication holes
200
a
,
200
b
and
200
c
. The laminated ink jet recording head having the configuration needs align and bonding processes to combine each of the plates. As illustrated in FIG.
1
B. a complicated assembling process is needed to combine each plate, which lowers yield and efficiency. Furthermore, an alignment error occurs during the alignment. In particular, the nozzle assembly indicated by “A” in
FIG. 1A
, including a damper serving as a flow path of fluid and nozzle, are formed by depositing the plates having different sized holes. The conventional nozzle assembly nozzle assembly, which effects a smooth fluid flow and discharge of ink droplets, is formed by depositing the individual plates. Thus, if the individual plates are misaligned, a directional smooth flow of fluid is not obtained.
The nozzle assembly can be manufactured in a variety of ways, as illustrated in
FIGS. 2A through 2F
,
FIGS. 3 and 4
, and
FIGS. 5A through 5C
. The illustrations of the drawings are limited to the formation of nozzles. Thus, additional deposition processes are needed to form a damper. These additional deposition processes are disadvantageous in terms of efficiency and yield, as described above.
In particular,
FIGS. 2A through 2F
illustrate a method for forming nozzles, which is disclosed in U.S. Patent No. 3,921,916. Referring to
FIGS. 2A through 2C
, a selective doping is performed on one surface of a substrate. Then, the opposite surface of the substrate is wet etched, as shown in FIG.
2
D. During the wet etching, only the doped silicon is selectively etched, forming a nozzle part, as illustrated in
FIGS. 2E and 2F
. Limitation of this method are related to doping depth and overall processing complexity.
FIG. 3
illustrates a method for forming nozzles by mechanical punching. This method results in uneven cut surfaces and a low yield. In addition, the method is applicable only to the structure formed by deposition.
FIG. 4
illustrates a method of forming nozzles, which was described in an article by Jafar Haji Babaei, et al., entitled “An integrable nozzle for monolithic microfluid devices,” published in Sensors and Actuators A, Vol. 65 (998), pp. 221-227. According to this method, the nozzle is formed by a two-side alignment and a time-controlled wet etching. The nozzle size is determined depending on the depth of etching and the feature size of a mask pattern used for wet etching. Thus, there is a problem of uniformity. It is inconvenient to stop the etching process by measuring time.
FIGS. 5A through 5C
illustrate a method for forming nozzles, which was described in an article by G. Siewell, et al., entitled “The thinkjet orifice plate: A part with many functions,” published in the Hewlett-Packard Journal, Vol. 36, No. 5, (May 1985), pp. 33-37. In particular, a photoresist pattern is applied on a portion of the substrate, as illustrated in FIG.
5
A. Then, nickel (Ni) is deposited on the structure exclusive of a pattern deposited portion to be nozzles by electroplating, as illustrated in FIG.
5
B. Then, the Ni plated layer is separated from the substrate, as illustrated in
FIG. 5C
, thereby completing a nozzle part. The size of nozzles formed through this method varies in the range of a few microns, and the tilt angle of the nozzle part cannot be accurately adjusted.
FIGS. 6A and 6B
, and
FIGS. 7A through 7D
illustrate conventional methods for manufacturing a nozzle assembly by combining two silicon wafers each having a damper and nozzle part made of silicon. Referring to
FIGS. 6A and 6D
, a bulk silicon wafer
20
having a damper
21
is attached to a nozzle plate
30
having a nozzle opening
31
to form a nozzle assembly. In another method, referring to
FIG. 7A
, first a damper
42
is formed in a bulk silicon wafer
40
. Then as illustrated in
FIG. 7B
, a wet etch mask
42
is deposited on the sidewalls of the damper
41
, and a nozzle plate
50
is prepared. The bulk silicon wafer
40
is stacked on the nozzle plate
50
, as illustrated in FIG.
7
C. Then, as shown in
FIG. 7D
, the portion of the nozzle plate
50
, which is exposed through the damper
41
, is wet etched to form a nozzle opening
51
.
For both of the methods described above, a thin wafer is used as the nozzle plates
30
and
50
, so that careful handling is required to keep the thin nozzle plates
30
and
50
from breaking. The method illustrated in
FIGS. 6A and 6B
needs a damper-to-nozzle alignment in combining the bulk silicon wafer
20
and the nozzle plate
30
. Although the method described with reference to
FIGS. 7A through 7D
requires no alignment, there is a problem of handing two separated fragile wafers.
FIGS. 8A through 8C
illustrate a nozzle structure formed using the characteristic of the crystal planes of silicon by wet etching. In particular,
FIG. 8A
illustrates the crystal planes of silicon. The etch rate of the (111) silicon plane in an etchant such as trimethylammonium hydroxide (TMAH) is slower than the (100) silicon plane. As a result, the (100) silicon plane is etched, as shown in
FIGS. 8B and 8C
.
FIG. 9
illustrates the formation of a nozzle structure by dry etching. As illustrated in
FIG. 9
, because the thickness of a coated layer is not uniform over the structure, i.e., because the coated layer is thicker at the trench sidewall portion c than at the portion a, uniform dry etching with plasma is difficult.
In the nozzle assembly having a damper outlet and a nozzle, the nozzle guide controls the flow of a fluid for smooth discharge. Additionally, the nozzle serves as the outlet of a valve, or a deposition unit, such as printer heads. The damper outlet enables fluid to flow in a direction, and serves as an auxiliary discharging unit as well as a damper.
A conventional method for forming a stepped nozzle assembly having a nozzle and a damper outlet with a silicon wafer by a micro-electro mechanical system (MEMS), wherein a single step of the stepped structure has a height greater than tens of microns, is illustrated in
FIGS. 10A through 10K
. In particular,
FIGS. 10A and 10B
are sectional views of substrates for nozzle assemblies each having multiple steps.
FIGS. 10C and 10D
are sectional views illustrating problems in the manufacture of a nozzle assembly with such a multi-step configuration. For example, reference numeral
5
indicates a void
5
formed in a deep trench during deposition of a photoresist layer.
FIGS. 10E through 10K
are sectional views illustrating a method for manufacturing the nozzle assembly shown in
FIG. 10A
with multiple stepped masks.
For the nozzle assembly illustrated in
FIG. 10A
, a bulk silicon wafer
80
is prepared first, as shown in FIG.
Kim Hyun-cheol
Lee Eun-sung
Oh Yong-soo
Song Ci-moo
Feggins K.
Lee & Sterba, P.C.
Nguyen Lamson
Samsung Electronics Co,. Ltd.
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