JP2002283563A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a wiring area and a pad area for leading out pads by taking discrete electrodes out from the rear face side of an electrode substrate, and reduce costs of an ink jet head by making a chip size small. SOLUTION: A driving voltage is impressed between a diaphragm 13 and the discrete electrode 23 formed on the electrode substrate 21, whereby the diaphragm 13 is deformed by an electrostatic force. Ink in a liquid chamber 12 is consequently pressured and ink liquid drops are discharged from a nozzle 33. A through hole 26 is formed to the electrode substrate 21 to reach the discrete electrode 23. A conductive film (Cr-Cu-Au alloy) 29 is formed to an inner wall and the periphery of the through hole 26, and a Pb-Sn alloy 30 is formed on the conductive film 29. When the electrode substrate 21 is heated in an H2 atmosphere to a temperature not lower than a melting point of a solder, a bump 31 is formed by a surface tension of the solder itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet head used in an ink-jet recording apparatus, and more particularly, to an ink-jet head provided with an actuator utilizing electrostatic force, which is used for recording in a printer, a facsimile, a copier, and the like. The present invention relates to an ink jet head having a feature in electrode extraction.

[0002]

2. Description of the Related Art An electrostatic actuator type ink jet head which generates a pressure wave in an ink chamber by displacing a vibrating plate by electrostatic force can be manufactured by a wafer process, so that it is easy to increase the density and to mass produce it. It is widely used because it can produce an element with stable characteristics, and because it is based on a planar structure, it can be easily miniaturized.
Many inventions have been made.

FIG. 4 shows an ink jet head disclosed in Japanese Patent Application Laid-Open No. 7-125196. FIG. 4 (A) is a side sectional view, and FIG. 4 (B) is a view taken along line AA. FIG.
The ink jet head described in (1) is composed of a first substrate 1a formed of a silicon substrate and integrally formed with a discharge chamber 6a having a bottom wall as a vibration plate 5a, and a glass substrate formed with a vibration plate 5a and a gap therebetween. A second substrate 2a having individual electrodes 21a opposed to each other and a third substrate 3a made of a glass substrate and forming a nozzle hole 4a are laminated and joined, and the individual electrodes 21a are formed of an insulating film 24a. The gap is defined by (the step of the insulating film) − (the thickness of the individual electrode). Further, the individual electrode 21a and the diaphragm electrode are drawn out on the same plane, so that a voltage can be applied.

FIG. 5 shows an ink jet head disclosed in Japanese Patent Application Laid-Open No. 10-61308.
A through hole 3b is formed in the glass substrate 1b on which the counter electrode 7b is formed, and a conductor 5b is embedded in the through hole 3b. Further, a metal wiring pattern 14b and a bump-shaped conductor 6b are formed on the back surface of the glass substrate 1b,
It is electrically connected to the counter electrode 7b. In this ink jet head, ink is supplied to the common liquid chamber 11b using the ink supply communication hole 12b.
From the back side. Further, the bump-shaped conductor 6b can be arranged at an arbitrary position by the metal wiring pattern 14b on the back surface of the glass substrate 1b.

FIG. 6 shows a configuration of Japanese Patent Application No. 11-224541.
No. 33, a nozzle 12c, an ink passage 13c, a diaphragm 12c provided in a part of the ink passage 13c, and a diaphragm 1
In an ink jet head having an individual electrode 22c provided opposite to 2c, a through hole 27c is opened from the back surface of the electrode substrate 21c to the individual electrode 22c, and the electrode is drawn out of a conductive material such as a metal. A pad 26c for electrical connection with the terminal is formed.

[0006]

The operation of the above-mentioned conventional electrostatic ink jet head is performed when a voltage is applied between a diaphragm formed on the bottom surface of the liquid chamber and an individual electrode formed at a position facing the diaphragm. The ink is sucked and ejected by vibrating the vibration plate by the attraction of electrostatic force generated by the vibration and the rigidity of the vibration plate. JP-A-7-12 shown in FIG.
The individual electrode of the ink jet head disclosed in Japanese Patent No. 5196 is taken out at a portion on the surface of the individual electrode substrate where there is no liquid chamber / diaphragm substrate. Further, in taking out the individual electrodes, as in the ink jet head disclosed in JP-A-10-61308 shown in FIG. 5 and the ink jet head described in the specification of Japanese Patent Application No. 11-224541 shown in FIG. In some cases, the process is performed from the back side of the electrode substrate to reduce the chip area and simplify the mounting process.

The configuration of the individual electrodes is disclosed in
Japanese Patent Application Laid-Open No. 10-613 discloses a method in which a step is formed on an insulating substrate and an electrode of a conductive material such as metal is formed in the step, as in an ink jet head disclosed in Japanese Patent Application Laid-Open No. 5196.
As in the ink jet head disclosed in Japanese Patent Application Laid-Open No. 08-08,083, there is a type in which a conductive type impurity diffusion region different from a substrate formed in a silicon substrate is used as an individual electrode. However, the method of taking out individual electrodes on the surface of the individual electrode substrate without the liquid chamber / diaphragm substrate like the ink jet head disclosed in Japanese Patent Application Laid-Open No. 7-125196 increases the chip area itself. There are drawbacks.
At the same time, an ink supply path for supplying ink to the common liquid chamber is also required, and forming both the electrodes and the extraction of the individual electrodes two-dimensionally requires a complicated structure and leads to an increase in cost. Japanese Patent Application Laid-Open No. 10-61308 and Japanese Patent Application No. 11-22, which take out electrodes from the back surface of an electrode substrate.
The ink jet head disclosed in the specification of Japanese Patent No. 4541 requires a through-hole region for taking out an electrode on the back surface of the electrode substrate, an electrode pad region, and a wiring region for connecting the through-hole and the pad. There is a problem in that the use of the region on the back surface over a wide range makes it difficult to make the nozzles as the number of nozzles increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an ink jet head capable of reducing the head cost by reducing the chip size and sufficiently coping with the increase in the number of nozzles. Aim. Also, by forming the individual electrodes on the electrode substrate thicker,
An object of the present invention is to prevent an electrode portion from being damaged when a through hole is formed, and to easily form a through hole.
Further, it is not necessary to form a wiring pattern or the like on the back surface of the electrode substrate, and it is another object of the present invention to be able to sufficiently cope with the increase in the number of nozzles. It is another object of the present invention to improve the adhesion between the bump and the individual electrode and to obtain high reliability.

[0009]

A first technical means of the present invention comprises a nozzle, an ink liquid chamber communicating with the nozzle, a vibrating plate constituting a part of the ink liquid chamber, and an electrode substrate. An ink droplet is ejected from the ink liquid chamber by applying a voltage between the vibration plate and the individual electrode and deforming the vibration plate by an electrostatic force. In the ink jet head, a through hole reaching the individual electrode is opened from a surface of the electrode substrate opposite to a surface on which the individual electrode is formed, and a side opposite to the surface of the electrode substrate on which the individual electrode is formed. The electrode is taken out from the surface of (1).

A second technical means is the ink jet head according to the first technical means, wherein the material of the individual electrode is single crystal silicon or polycrystalline silicon.

According to a third technical means, in the ink jet head according to the first or the second technical means, a metal bump is formed immediately below the individual electrode.

According to a fourth technical means, in the ink jet head according to the third technical means, at least one or more conductive films are provided between the individual electrodes and the metal bumps.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention.
3 will be described based on the embodiment shown in FIG. 1A and 1B show a configuration of an ink jet head according to an embodiment of the present invention. FIG. 1A is a longitudinal sectional view of a main part of an individual bit, and FIG. 1B is a transverse sectional view. In FIG. 1, the liquid chamber / vibrating plate substrate 11 is made of a <110> silicon wafer, and the silicon wafer is processed into a concave shape according to the shape of the ink liquid chamber 12 by photolithography and etching techniques. 3μ thickness on the bottom
m of diaphragms 13 are formed.

The electrode substrate 21 is made of a <110> silicon wafer, and a silicon oxide film 22 having a thickness of 0.5 μm is arranged on the silicon wafer so as to function as an insulating layer. Polycrystalline silicon having a thickness of 2 μm is arranged on the silicon oxide film 22 to form individual electrodes 23. A silicon oxide film 24 having a thickness of 0.5 μm is formed on the individual electrode 23, and a vibration chamber 25, which is a space in which the vibration plate 13 is displaced by electrostatic force, is formed immediately below the vibration plate 13. It is formed concavely with a step of 0.3 μm. The electrode substrate 21 has a through hole 2
6 are formed and reach the individual electrodes 23. A metal bump 31 is formed immediately below the individual electrode 23, and a conductive film 29 is provided between the bump 31 and the individual electrode 23.
Are formed. The nozzle plate 41 has an ink discharge nozzle 42 formed thereon, and is attached on the liquid chamber / vibrating plate substrate 11.

Next, a specific method of manufacturing the ink jet head of the embodiment will be described. FIG. 2 and FIG. 3 are cross-sectional views of essential parts for explaining a series of manufacturing steps of the ink jet head of the embodiment, and include the following steps (A) to (I).
As the electrode substrate 21, a portion having a thickness of 400 μm as a base is made of a silicon wafer having a <110> plane orientation,
A 0.5 μm silicon oxide film 22 is formed thereon,
Further, an SO having an active layer 23L having a thickness of 2 μm thereon is provided.
An I silicon wafer is used. (Fig. 2 (A))

After diffusing impurities into the active layer 23L side of the SOI silicon wafer to such a concentration as to function as an electrode, the individual electrodes 2 are formed by photolithography and etching.
Leave only the part that becomes 3. (FIG. 2 (B))

Subsequently, a silicon oxide film 24L is formed to a thickness of 2.5 μm, which is 0.5 μm thicker than the individual electrode 23, using a CVD technique. After that, the vibration chamber 25 is formed by photolithography and etching. 0.3 level difference of vibration chamber 25
μm can be accurately formed by dry etching technology. (Fig. 2 (C))

Next, the thickness 4 to be the liquid chamber / diaphragm substrate 11
After bonding a <110> silicon wafer of 00 μm by a direct bonding method, the electrode substrate 21 is thinned to 200 μm by a mechanical polishing method. At the same time, the liquid chamber / diaphragm substrate 1
1 is also polished to a thickness of 100 μm by a mechanical polishing method, and the silicon wafer is processed into a concave shape according to the shape of the vibration chamber 25 by photolithography and etching, and at the same time, a 3 μm thick vibration is formed on the bottom surface of the ink liquid chamber 12. Board 13
To form (FIG. 2 (D))

Next, a slightly thicker oxide film 27 having a thickness of 0.5 μm is formed on the back side of the electrode substrate 21 by a wet oxidation method. (FIG. 3 (E))

Next, a through hole 26 is formed at a position aligned with the individual electrode 23. It is desirable that the size of the through hole 26 is smaller than the length of the individual electrode 23 in the width direction. In this case, since the dimension in the short direction of the individual electrode 23 was 120 μm, the opening diameter of the through hole was 50 μm. The through hole 26 is formed by patterning a resist to have an opening diameter of 50 μm in accordance with the shape of the target through hole, exposing the silicon oxide film 22, and then performing anisotropic dry etching. Select the gas according to the etching target,
As a result of efficient etching, the individual electrodes 23 are exposed through the silicon oxide film 22. (FIG. 3 (F))

Thereafter, an oxide film 28 of 0.2 μm is formed on the inner wall of the through hole 26 and the individual electrode 23 by a wet oxidation method.
m. After that, the oxide film 28 formed on the individual electrodes 23 is removed by a dry etching method. (Figure 2
(G) At this time, the oxide film 28 is made slightly thicker, 0.5 μm, so that the film thickness is sufficiently secured even when etching is performed simultaneously with the oxide film 28 formed on the individual electrode 23. Further, the silicon oxide film 28 on the side surface of the through hole 26 is hardly etched, and is left while maintaining the electrical insulation on the side surface of the through hole 26.

Next, a Cr-Cu-Au alloy 29 is formed with a thickness of 2 μm only in and around the through hole 26. As a method for forming the Cr-Cu-Au alloy 29, first, in a semiconductor manufacturing method, a general Cr-Cu-Au alloy was used as a target and a PVD method was used to form a 2 μm-thick film over the entire substrate surface. Next, using photolithography and etching techniques, Cr
-A Cu-Au alloy 29 was formed. Next, Cr-Cu-
Pb and Sn alloy 30 (Pb-5wt) on Au alloy 29
% Sn) is formed to a thickness of 50 μm. As a forming method, it was possible to selectively grow on the Cr-Cu-Au alloy 29 using an electroless plating method. The resulting shape is the underlying Cr
-It could be formed slightly larger than the pattern of the Cu-Au alloy 29. (Fig. 2 (H))

Finally, when heated in a H ₂ atmosphere at a solder melting point of about 300 ° C. or higher, a bump 31 having a desired shape was obtained by the surface tension of the solder itself. (FIG. 3 (I))

In the embodiment of the present invention, an SOI silicon wafer was used as the electrode substrate 21, but a thermal oxide film of 0.5 μm was grown on a <110> silicon wafer, and then 2 μm of polycrystalline silicon was formed thereon. The same operation and effect can be obtained. The metal thin film used between the individual electrode 23 and the bump 31 is Cr-Cu-A described in the embodiment.
It is not necessary to use the u alloy 29, and as an alternative, any material having good adhesion to Si and good wettability to the bump material may be used, such as Cu, Ni, Sn, Pb, Ag, and at least one of them. And the like. Although a single layer is used in this embodiment, a multilayer structure including the above-described metal may be used. In this embodiment, solder was used as a bump material. However, this can be replaced with any material having good wettability with the Si individual electrode or the conductive film of the intermediate layer. For example, Cu, Au, Ag, Al, Sn, Ge, Pb, and an alloy containing at least one of these are possible.

[0025]

As is apparent from the above description, according to the first aspect of the present invention, since the individual electrodes are taken out from the back side of the electrode substrate, a wiring area and a pad area for drawing out pads are not required. Therefore, the chip size can be reduced, and the cost of the ink jet head can be reduced.

According to the second aspect of the present invention, since the individual electrodes are formed of single crystal silicon or polycrystalline silicon, the thickness of the individual electrodes themselves can be relatively easily increased, and the through electrodes can be formed from the back surface of the electrode substrate. When the holes are formed, the rigidity of the individual electrodes prevents the penetration to the front side, and the through holes can be formed relatively easily.

According to the third aspect of the present invention, since the bump is directly taken out from the back electrode without a wiring pattern, there is no need for a step of forming a wiring pattern, and the structure can be used immediately for subsequent mounting. This makes it possible to reduce costs in the manufacturing process of the inkjet head and the subsequent mounting process.

According to the fourth aspect of the present invention, since the metal thin film is interposed between the bump and the individual electrode, the adhesiveness between the bump and the individual electrode is improved, and in actual use, it is resistant to stresses such as heat, humidity, and vibration. It is possible to obtain high reliability in which electrical defects and omissions hardly occur.

[Brief description of the drawings]

FIGS. 1A and 1B show a configuration of an ink jet head according to an embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view of a main part of an individual bit, and FIG.

FIG. 2 is a diagram illustrating a manufacturing process for manufacturing an inkjet head according to an embodiment of the present invention.

FIG. 3 is a view illustrating a manufacturing process subsequent to FIG. 2 for manufacturing the inkjet head according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a configuration of a conventional inkjet head.

FIG. 5 is a cross-sectional view illustrating another configuration of a conventional inkjet head.

FIG. 6 is a cross-sectional view illustrating still another configuration of the conventional inkjet head.

[Explanation of symbols]

11: liquid chamber, diaphragm substrate, 12: ink liquid chamber, 13: diaphragm, 21: electrode substrate, 22: silicon oxide film, 23:
Individual electrodes, 24: silicon oxide film, 25: vibration chamber, 26
... through-hole, 27 ... oxide film, 28 ... silicon oxide film, 29 ... conductive film (Cr-Cu-Au alloy), 30 ...
Pb-Sn alloy, 31: bump, 41: nozzle plate, 42: nozzle.

Claims (4)

[Claims] A nozzle, an ink chamber communicating with the nozzle, a vibrating plate constituting a part of the ink chamber, and an individual electrode disposed on the electrode substrate so as to face the vibrating plate. An ink jet head that applies a voltage between the vibration plate and the individual electrode and discharges ink droplets from the ink liquid chamber by deforming the vibration plate with electrostatic force, wherein the individual electrode of the electrode substrate is formed. An ink jet head comprising: opening a through hole reaching the individual electrode from a surface opposite to a surface on which the individual electrode is formed; and taking out the electrode from a surface of the electrode substrate opposite to the surface on which the individual electrode is formed. 2. The ink jet head according to claim 1, wherein the material of said individual electrode is single crystal silicon or polycrystalline silicon. 3. The ink jet head according to claim 1, wherein a metal bump is formed immediately below said individual electrode. 4. The ink jet head according to claim 3, further comprising at least one conductive film between said individual electrode and said metal bump.