JPWO2013111626A1 - Inkjet head manufacturing method and inkjet head - Google Patents

Abstract

The present invention provides an ink jet head that can maintain the quality of the pressure generating means without causing a drop in the function of the pressure generating means even when wire bonding is performed on the pressure generating means by ball bonding, and can stabilize the discharge performance. For the purpose of providing a manufacturing method, a plurality of nozzles that eject ink, a plurality of pressure chambers that are respectively disposed corresponding to the nozzles and that accommodate ink therein, and a pressure chamber that is disposed corresponding to each pressure chamber A plurality of pressure generating means for applying a pressure for ejecting ink in the pressure chamber by vibrating the wall surface between the chambers as a vibration plate, and wiring for supplying power to the pressure generating means are formed. In the manufacture of an inkjet head having an external wiring member, the space between the wiring of the external wiring member and the pressure generating means is formed by wire bonding using ball bonding. When electrically connecting in down loading wire, to form a bonding wire fast bonding wire bond as a pressure generating means side.

Description

  The present invention relates to a method for manufacturing an ink jet head and an ink jet head, and more particularly to a method for manufacturing an ink jet head and an ink jet head that can stabilize the discharge performance by preventing the function of a pressure generating means from being lowered.

  An ink jet head used in an ink jet recording apparatus that records an image or the like by ejecting minute ink droplets onto a recording medium such as recording paper is applied to ink in a pressure chamber by driving a pressure generating means including a piezoelectric element such as PZT. A pressure change is generated, and ink in the pressure chamber is ejected from the nozzle. In recent years, in order to realize high-precision and high-definition image formation by an ink jet recording apparatus, high definition of nozzles in an ink jet head has been demanded.

  Conventionally, as a method for supplying power to the pressure generating means of an inkjet head, a substrate on which a driving IC is mounted is stacked above the pressure generating means, and a bonding wire is used between the driving IC and a lead electrode drawn out from the pressure generating means. An electrical connection is known (Patent Document 1).

JP 2004-160947 A

  In the method described in Patent Document 1, since it is necessary to draw out the lead electrode from the pressure generating means, the manufacturing process such as application of the insulating layer and patterning of the electrode by etching is complicated and only takes time. There is also a problem that the manufacturing cost increases.

  For this reason, the present inventor, as a method of supplying power to the pressure generating means without pulling out the lead electrode from the pressure generating means, a method of establishing an electrical connection by directly performing wire bonding by ball bonding on the pressure generating means. It was investigated.

  However, it has been found that if the electrical connection is made by performing wire bonding by ball bonding on the pressure generating means, there is a problem that variation in ejection performance occurs in the obtained ink jet head. The inventor diligently studied the cause and obtained the following findings.

  The surface on which the pressure generating means is installed is the surface of the diaphragm of the pressure chamber, and this surface is formed in a thin film shape so that the pump function by vibration can be easily exerted, and it matches the mechanical displacement of the pressure generating means. Can be vibrated easily. For this reason, the diaphragm has a mechanically weak part against the load. When wire bonding is performed as it is on the pressure generating means in close contact with the upper surface of the diaphragm, the diaphragm is bent by the load applied during wire bonding. Along with this, a force to deform the pressure generating means acts. When this deformation force acts on the pressure generating means, the pressure generating means causes self-power generation due to the piezoelectric effect, causing electrical damage to the pressure generating means, leading to a decrease in function of the pressure generating means (decrease in displacement). become. Such a decrease in the function of the pressure generating means is a serious problem that deteriorates the ejection performance of ink droplets and leads to a decrease in image quality.

  Therefore, the present invention can maintain the quality of the pressure generating means without degrading the function of the pressure generating means even if wire bonding is performed by ball bonding on the pressure generating means, and the discharge performance is stabilized. It is an object of the present invention to provide an ink jet head manufacturing method and an ink jet head capable of performing the above.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1. A plurality of nozzles for ejecting ink;
A plurality of pressure chambers respectively disposed corresponding to the nozzles and containing ink therein;
A plurality of pressure generating means disposed corresponding to each of the pressure chambers, and applying a pressure for ejecting ink in the pressure chamber by vibrating a wall surface between the pressure chambers as a vibration plate; An external wiring member on which wiring for supplying power to the means is formed,
A method of manufacturing an inkjet head, wherein the wiring of the external wiring member and the pressure generating means are electrically connected by a bonding wire formed by wire bonding using ball bonding,
The method of manufacturing an ink jet head, wherein the bonding wire is formed using the first bond of the wire bond as the pressure generating means side.

2. The planar shapes of the pressure chamber and the pressure generating means are each substantially circular, the planar shape of the pressure generating means is smaller than the planar shape of the pressure chamber, and the pressure generating means is the pressure chamber in plan view. Are arranged so as to overlap
2. The method of manufacturing an ink jet head according to claim 1, wherein bumps are formed by disposing the hit points of the first bond at positions away from the center of the pressure chamber on the pressure generating means in plan view.

3. 3. The method of manufacturing an ink jet head according to 2, wherein the bumps are formed by disposing the first bond hit points at positions satisfying the following conditional expressions.

However, _{r a:} the radius r _b of the pressure generating means: the radius of the bump after the ball bond r _c: radius x _b of the pressure chambers, _{y b:} coordinates X _b bump with the origin at the center of the pressure generating means, _{Y b} : Bump coordinates with the center of the pressure chamber as the origin

4). 4. The method of manufacturing an ink jet head according to 1, 2, or 3, wherein the first bond hit point load is 0.3 to 1.0 N.

5. A plurality of nozzles for ejecting ink;
A plurality of pressure chambers respectively disposed corresponding to the nozzles and containing ink therein;
Corresponding to each of the pressure chambers, the pressure chambers are arranged so as to overlap with the pressure chambers in plan view, and a wall surface between the pressure chambers is vibrated as a vibration plate to apply pressure for ejecting ink in the pressure chambers. A plurality of pressure generating means;
An external wiring member on which wiring for supplying power to each of the pressure generating means is formed;
The planar shapes of the pressure chamber and the pressure generating means are each substantially circular, and the planar shape of the pressure generating means is smaller than the planar shape of the pressure chamber, and the wiring of the external wiring member, the pressure generating means, A method for manufacturing an ink jet head, wherein a bonding wire formed by wire bonding by ball bonding is electrically connected between the two,
A method of manufacturing an ink-jet head, comprising: forming a bump by ball bonding by disposing a hitting point at one end of the bonding wire at a position away from the center of the pressure chamber on the pressure generating means in plan view.

6). 6. The method of manufacturing an ink jet head according to 5, wherein the position of the bump on the pressure generating means at one end of the bonding wire satisfies the following conditional expression.

However, _{r a:} the radius r _b of the pressure generating means: the radius of the bump after the ball bond r _c: radius x _b of the pressure chambers, _{y b:} coordinates X _b bump with the origin at the center of the pressure generating means, _{Y b} : Bump coordinates with the center of the pressure chamber as the origin

7). 7. The method of manufacturing an ink jet head as described in 5 or 6, wherein a load at one end of the bonding wire on the pressure generating means is 0.3 to 1.0 N.

8). A plurality of nozzles for ejecting ink;
A plurality of pressure chambers respectively disposed corresponding to the nozzles and containing ink therein;
Corresponding to each of the pressure chambers, the pressure chambers are arranged so as to overlap with the pressure chambers in plan view, and a wall surface between the pressure chambers is vibrated as a vibration plate to apply pressure for ejecting ink in the pressure chambers. A plurality of pressure generating means;
An external wiring member on which wiring for supplying power to each of the pressure generating means is formed;
The planar shapes of the pressure chamber and the pressure generating means are each substantially circular, and the planar shape of the pressure generating means is smaller than the planar shape of the pressure chamber, and the wiring of the external wiring member, the pressure generating means, An ink jet head that is electrically connected by a bonding wire formed by wire bonding by ball bonding,
2. An ink jet head according to claim 1, wherein a ball bond bump formed by a hitting point on the pressure generating means at one end of the bonding wire is formed at a position away from the center of the pressure chamber in plan view.

9. 9. The ink jet head according to 8, wherein the position of the bump on the pressure generating means at one end of the bonding wire satisfies the following conditional expression.

However, _{r a:} the radius r _b of the pressure generating means: the radius of the bump after the ball bond r _c: radius x _b of the pressure chambers, _{y b:} coordinates X _b bump with the origin at the center of the pressure generating means, _{Y b} : Bump coordinates with the center of the pressure chamber as the origin

  According to the present invention, it is possible to maintain the quality of the pressure generating means without stabilizing the function of the pressure generating means even when wire bonding is performed by ball bonding on the pressure generating means, and to stabilize the discharge performance. An inkjet head manufacturing method and an inkjet head can be provided.

An exploded perspective view showing an example of an inkjet head Sectional view cut along the line (ii)-(ii) in FIG. FIG. 1 is a partial cross-sectional view showing a layer structure of a head substrate in the ink jet head shown in FIG. FIG. 1 is a partial plan view showing an electrical connection portion in the ink jet head shown in FIG. The figure which shows the positional relationship in the planar view of a pressure chamber, a pressure generation means, and a bump A graph showing the relationship between the ratio of the bump distance from the center of the pressure chamber and the radius of the pressure chamber (horizontal axis) and the amount of displacement of the pressure generating means (vertical axis)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 is an exploded perspective view showing an example of an ink jet head, FIG. 2 is a cross-sectional view taken along a line (ii)-(ii) in FIG. 1, and FIG. 3 is a diagram of the ink jet head shown in FIG. FIG. 4 is a partial cross-sectional view showing a layer structure of the head substrate, and FIG. 4 is a partial plan view showing an electrical connection portion in the ink jet head shown in FIG.

  In FIG. 1, reference numeral 1 denotes an inkjet head. The inkjet head 1 has a head substrate 2, a holding substrate 3, an external wiring member 4, and an ink chamber member 5.

  The head substrate 2 is configured by stacking and integrating three substrates, a body plate 21, an intermediate plate 22, and a nozzle plate 23.

  The body plate 21 is made of a Si substrate having a long length along the direction A in FIG. 1 and a thickness of about 100 to 300 μm. By etching one surface (the lower surface in FIG. 1), the planar shape is substantially reduced. A plurality of pressure chambers 211 having a circular shape, a common channel 212 formed of a concave groove for supplying ink to the plurality of pressure chambers 211 in common, the common channel 212 and each pressure chamber 211 are individually provided. This is a flow path forming substrate in which an ink supply path 213 formed of a narrow groove for communicating the ink in the common flow path 212 to the pressure chamber 211 is recessed.

  Each pressure chamber 211 has a bulging portion 211a having a shape in which a portion bulges outward to be a communication portion with a communication hole 221 formed in the intermediate plate 22 described later. FIG. 1 shows the body plate 21 in which 16 pressure chambers 211 are arranged along the A direction, and two pressure chambers for supplying ink to every other eight pressure chambers 211 are shown. The common flow channel 212 is disposed so as to sandwich the row of pressure chambers 211 therebetween.

  On the other surface of the body plate 21 (the upper surface in FIG. 1), a piezoelectric element 214 made of PZT or the like that functions as a pressure generating means is laminated so as to correspond to the position of each pressure chamber 211. At the time of driving, the wall surface between the piezoelectric element 214 and the pressure chamber 211 is vibrated as a vibration plate 215, thereby applying pressure for ejection to the ink in the pressure chamber 211.

  The planar shape of each piezoelectric element 214 is formed to be a substantially circular shape similar to that of the pressure chamber 211, but the area is smaller than the planar shape of the pressure chamber 211. The piezoelectric elements 214 are arranged so as to overlap each other without protruding from the pressure chambers 211 in plan view, corresponding to the pressure chambers 211, respectively. Each piezoelectric element 214 has electrodes (not shown) on the upper and lower surfaces, the upper surface electrode is an individual electrode, and the lower surface electrode is in contact with the common electrode provided on the upper surface of the body plate 21.

  Each common flow channel 212 extends along the A direction which is the longitudinal direction of the body plate 21, and its end portion penetrates the body plate 21 in the vicinity of both end portions in the A direction of the body plate 21. The through holes 216 that are formed communicate with each other. The through-holes 216 are arranged side by side along the B direction, which is the short direction of the body plate 21 perpendicular to the A direction, at each end of the body plate 21. It communicates with the end of the.

  The intermediate plate 22 is formed of a glass substrate having the same shape as the body plate 21 in plan view and a thickness of about 100 to 300 μm, and is formed in the pressure chamber 211 of the body plate 21 when laminated with the body plate 21. Communication holes 221 are formed individually at positions corresponding to the bulging portions 211a so as to penetrate the intermediate plate 22 on the front and back sides and serve as ink flow paths at the time of ejection. Borosilicate glass (for example, Tempax glass (trade name)) is preferably used for the intermediate plate 22.

  The nozzle plate 23 is made of a Si substrate having a thickness of about 100 to 300 μm. When the nozzle plate 23 is laminated with the intermediate plate 22, nozzles 231 that discharge ink droplets are formed at positions corresponding to the communication holes 221 of the intermediate plate 22. Has been. Each nozzle 231 has an opening on the opposite surface of the nozzle plate 23 to the intermediate plate 22, and communicates with the nozzle 231 from the surface on the intermediate plate 22 side, and has a large-diameter portion formed by a recess having a larger diameter than the nozzle 231. 232 is recessed.

  Note that an ink repellent film (not shown) is formed on a nozzle formation surface (nozzle surface) 230 where the nozzles 231 open in the nozzle plate 23.

  The head substrate 2 is laminated with the body plate 21, the intermediate plate 22 and the nozzle plate 23 aligned so that the bulging portion 211a of the pressure chamber 211, the communication hole 221, and the large diameter portion 232 (nozzle 231) communicate with each other. And are integrally joined. As a method for joining the body plate 21, the intermediate plate 22, and the nozzle plate 23, anodic bonding is generally used.

  By joining the body plate 21, the intermediate plate 22, and the nozzle plate 23, the lower surfaces of the pressure chamber 211, the common flow path 212, and the ink supply path 213 of the body plate 21 are closed, and at both ends of each common flow path 212. The through-holes 216 communicating with each other open only on the upper surface of the head substrate 2 in FIG. 1 and serve as openings for supplying ink to each common flow channel 212 or discharging ink from each common flow channel 212. .

  In the head substrate 2, the nozzles 231 are arranged in one row along the A direction.

  The holding substrate 3 is a substrate that is bonded to the head substrate 2 with an adhesive to hold the head substrate 2 and retains and fixes the head substrate 2, and has a thickness of about 0.5 mm to 3 mm. It consists of a substrate or a glass substrate. As the glass substrate, borosilicate glass (for example, Tempax glass (trade name)) is preferably used similarly to the intermediate plate 22 of the head substrate 2.

  The holding substrate 3 has a plan view shape larger than the head substrate 2 in both the A direction and the B direction. In particular, both end portions along the A direction of the holding substrate 3 are greatly projected from both ends of the head substrate 2 in the A direction.

  In the central portion of the holding substrate 3, one opening having a size that can surround all the piezoelectric elements 214 arranged on the body plate 21 of the head substrate 2 when bonded to the head substrate 2. 31 is formed through. The opening 31 is formed in a rectangular shape extending along the direction A in FIG. 1 and can surround all the piezoelectric elements 214 on the head substrate 2 in the opening 31, but two openings that respectively open at both ends of the head substrate 2. It is formed in a size that does not reach the position of each through-hole 216.

  In the vicinity of both end portions in the A direction of the holding substrate 3, one through hole 32 serving as an ink flow path having a size capable of surrounding each of the two through holes 216 opening on the upper surface of the head substrate 2 is formed. Yes. Accordingly, one through hole 32 communicates with two through holes 216 and 216 arranged in parallel on the head substrate 2.

  The holding substrate 3 is aligned with the head substrate 2 so that all the piezoelectric elements 214 on the head substrate 2 are located in the opening 31 and each through-hole 216 is located in and communicates with the through-hole 32. , And bonded together by an adhesive. Although the holding substrate 3 is made of a glass substrate, since the linear expansion coefficient is close to the Si substrate and the glass substrate constituting the head substrate 2, even when a bonding method involving heating such as a thermosetting adhesive is used as an adhesive, Warpage between the holding substrate 3 and the head substrate 2 is suppressed.

  Further, when the holding substrate 3 is made of a glass substrate, since it has ultraviolet transparency, a UV curable adhesive or a UV thermosetting adhesive is used as the adhesive, and a bonding method that does not involve heating in the initial curing is used. May be.

  In addition, the lower surface of the holding substrate 3 (the bonding surface with the head substrate 2) is formed with a recess 33 that extends in a region that is the same as the opening 31 in the A direction and larger than the opening 31 in the B direction. As shown in FIG. 2, the recess 33 is formed to have a size that can include the two common flow paths 212 of the head substrate 2 when the holding substrate 3 and the head substrate 2 are joined. As a result, not only all the piezoelectric elements 214 in the head substrate 2 but also each pressure chamber 211, the common channel 212 excluding both ends, and the ink supply channel 213 are arranged in the recess 33 of the holding substrate 3. 3 is not directly joined.

  The external wiring member 4 is a wiring provided with wiring 41 (see FIG. 4) for electrically connecting the driving circuit to each piezoelectric element 214 in order to apply a driving signal from a driving circuit (not shown). The member is made of, for example, FPC. One end of the external wiring member 4 is joined to one side of the opening 31 along the A direction on the holding substrate 3 by an adhesive. Between each wiring 41 of each external wiring member 4 and each piezoelectric element 214, as shown in FIG. 2 to FIG. It is connected.

  Details of the method of forming the bonding wire 42 will be described later.

  The ink chamber member 5 is formed in a box shape with one surface (lower surface in the drawing) opened by a synthetic resin material such as PPS (polyphenylene sulfide resin), for example, and one at each end of the holding substrate 3 in the A direction. Has been placed.

  Each ink chamber member 5 temporarily stores the ink supplied from an ink tank (not shown) or the like, and passes through the through hole 32 of the holding substrate 3, the through hole 216 of the body plate 21, the common channel 212, and the ink supply channel 213. Thus, ink is supplied into each pressure chamber 211, or vice versa, ink in each pressure chamber 211 is supplied to the ink supply path 213, the common flow path 212, the through hole 216 of the body plate 21, and the through hole of the holding substrate 3. This is for receiving through a waste ink tank 32 and discharging it to a waste ink tank (not shown). On the upper surface of the ink chamber member 5, a flow path port 51 for supplying or discharging ink is provided.

  One of the two ink chamber members 5 may function for supplying ink and the other function for discharging ink, but both ink chamber members 5 may function for supplying ink.

  A filter 52 for removing impurities such as dust and bubbles in the ink so that the ink supplied to the common flow path 212 through the through hole 32 and the through hole 216 can pass inside the ink chamber member 5. Is provided. The filter 52 is made of, for example, a metal mesh such as SUS, and is welded to the resin in the ink chamber member 5.

  These ink chamber members 5 are arranged at both ends in the A direction of the holding substrate 3 and outside the opening 31 of the holding substrate 3. The through holes 32 of the holding substrate 3 communicate with the inside of the ink chamber member 5.

  In this ink jet head 1, two ink chamber members 5 are arranged, so that a large amount of ink can be stored by both ink chamber members 5 and 5, and the ink amount that can be stored is only one conventional ink chamber member. Compared with nothing.

  The ink chamber members 5 are not limited to the same shape (same volume), but may have different shapes (volumes) as necessary. Further, there may be two or more ink chamber members 5 bonded to each end of the holding substrate 3.

  Next, a method for forming the bonding wire 42 for electrical connection between each wiring 41 of the external wiring member 4 and each piezoelectric element 214 on the head substrate 2 will be described.

  A bonding wire 42 that is electrically connected to the wiring 41 of the external wiring member 4 and supplies power (application of a driving signal) from a driving circuit (not shown) to each piezoelectric element 214 is formed on the upper surface of the holding substrate 3. Between the end of each wiring 41 of the external wiring member 4 in a bonded state and the upper surface of each piezoelectric element 214 on the head substrate 2 bonded to the holding substrate 3 (the upper surface of the upper electrode of the piezoelectric element 214) In addition, wire bonding is performed by ball bonding, and bumps 43 and 44 are formed to electrically connect the wiring 41 and the piezoelectric element 214 to each other.

  Generally, when a bonding wire is formed by wire bonding by ball bonding, a wire in a state where a ball (FAB: Free Air Ball) is formed at the tip is captured at the tip of the capillary and the capillary is moved to the position of the first target. Thereafter, the capillary is lowered to bring the ball into contact with the first target, and heat, load and ultrasonic waves are applied to form a first bond (hereinafter referred to as 1st bond) which becomes the first hit point of the wire bond. At this time, a bump having a predetermined diameter is formed by crushing the ball. Next, the capillary is raised to a certain height, the capillary is moved to the position of the second target, a wire loop is formed, and the capillary is lowered to press the wire onto the second target. A second bond (hereinafter referred to as 2nd bond) is formed as the second hit point. At this time, the wire is deformed by applying heat, a load and ultrasonic waves, and a stitch bond for joining the wire onto the second target and a tail bond for securing the tail in the next step are formed. Thereafter, the capillary is raised, the wire clamp of the capillary is closed, and the wire is torn off from the tail bond portion, thereby forming a bonding wire that electrically connects the two targets.

  Thus, the 1st bond is formed by bringing the ball formed at the tip of the wire into contact with the first target and applying a predetermined heat, load and ultrasonic wave, whereas the 2nd bond forms a loop. Since the wire is formed by pressing the wire onto the second target with a capillary, it is necessary to apply a larger load than the first bond. The load at the time of the 2nd bond is generally set to 1.0 to 2.0 N in order to ensure that the 2nd bond can be bonded onto the second target.

  On the other hand, the wall surface between the pressure chamber 211 and the piezoelectric element 214 is a diaphragm 215 and is generally formed in a thin film shape so that the pump function by vibration can be easily exhibited. For this reason, when a large load is applied to the diaphragm 215, the diaphragm 215 bends, causing electrical damage due to self-power generation of the piezoelectric element 214, resulting in a function deterioration (decrease in displacement). . This is because the vibration plate 215 is excessively bent by the load due to the hitting point. Therefore, by suppressing the bending of the vibration plate 215 at the hitting point, it is possible to suppress the functional deterioration of the piezoelectric element 214.

  Therefore, in the first embodiment, when the bonding wire 42 for electrically connecting the wiring 41 of the external wiring member 4 and the piezoelectric element 214 is formed by such wire bonding, the 1st bond is piezoelectric. Wire bonding is performed on the element 214 side. Thereby, even when the wiring 41 of the external wiring member 4 and the piezoelectric element 214 are electrically connected by the bonding wire 42, the bending applied to the diaphragm 215 by the load at the time of hitting can be reduced. As a result, the deformation force acting on the piezoelectric element 214 can be reduced, and the functional deterioration of the piezoelectric element 214 can be suppressed.

  The load due to the hit point of this 1st bond is preferably 0.3 to 1.0 N. By setting the load within this range, it is possible to form the bump 43 having an appropriate shape by the wire ball being crushed on the piezoelectric element 214. This load is set by adjusting the pressing force at the time of hitting the capillary.

  If the load is smaller than the lower limit of the above range, the bumps 43 may not be able to adhere to the piezoelectric element 214, and the bumps 43 are liable to occur. If the upper limit of the above range is exceeded, an excessive load is applied to the bump formation, and the bump 43 is crushed. More preferably, it is 0.4 to 0.8N.

  It is possible to form bumps 43 on the piezoelectric element 214 by placing the hit points on the piezoelectric element 214 that will be the first bond when forming the bonding wire 42 at positions away from the center of the pressure chamber 211 in plan view. preferable.

  Since the thin-film diaphragm 215 has the most mechanically weak central portion, the bump 43 formed by the 1st bond hit point is formed at a position away from the mechanically weak center of the pressure chamber 211 in plan view. Thus, when the same load is applied, the amount of deflection of the diaphragm 215 is reduced compared to the center. As a result, the deformation force acting on the piezoelectric element 214 can be further reduced.

  Since the bump 43 on the piezoelectric element 214 formed at one end of the bonding wire 42 has a substantially circular planar shape, the position of the bump 43 is defined by its center position.

The bump 43 on the piezoelectric element 214 is preferably separated from the center of the pressure chamber 211 as much as possible because the influence of the deflection of the vibration plate 215 at the time of striking increases as it approaches the center of the pressure chamber 211. . On the other hand, the bump 43 may be peeled off even if part of the bump 43 protrudes from the upper surface of the piezoelectric element 214, so that the entire bump 43 needs to be within the upper surface of the piezoelectric element 214. For this reason, it is preferable that the position of the bump 43 on the piezoelectric element 214 at one end of the bonding wire 42 satisfies the following conditional expression.

Where r _a : radius of the piezoelectric element r _b : radius of the bump after ball bonding r _c : radius of the pressure chamber x _b , y _b : coordinates of the bump with the origin of the center of the piezoelectric element X _b , Y _b : pressure Bump coordinates with the center of the chamber as the origin

  FIG. 5 shows a positional relationship among the pressure chamber 211, the piezoelectric element 214, and the bump 43 in plan view. Although the center of the pressure chamber 211 and the center of the piezoelectric element 214 are not necessarily completely coincident with each other, here, for convenience of explanation, it is assumed that the centers of both coincide with each other in plan view.

By satisfying the above expression 1, as shown in FIG. 5, the entire bump 43 is fit into the center O side of the radius r _a of the piezoelectric element 214, it never protrudes from the upper surface of the piezoelectric element 214, upper plane It is arranged at a position that fits in. Therefore, there is no fear of peeling of the bumps 43.

On the other hand, by satisfying the above expression 2, the center position of the bump 43 becomes a position away from the center O of the pressure chamber 211. As shown in FIG. 6, the value of 0.2 in the equation 2 indicates that when the position of the bump 43 is actually moved away from the center of the pressure chamber 211, power is supplied to the piezoelectric element 214. This is a value obtained as a result of measuring the amount of displacement of the piezoelectric element 214 when driven. As apparent from the figure, in the range where the distance from the center of the pressure chamber 211 of the bump 43 is greater than a radius r _c × 0.2 the pressure chamber 211, but substantially shows a constant displacement, r _c It can be seen that in the range below × 0.2, the displacement amount of the piezoelectric element 214 starts to drop, and the function is deteriorated. Therefore, by satisfying the above formula 2, it is possible to avoid the functional degradation of the piezoelectric element 214.

  In the first embodiment described above, the bump 43 formed on the piezoelectric element 214 is formed by the 1st bond. However, in the second embodiment, the bump 43 on the piezoelectric element 214 is the 1st bond. Or 2nd bond.

  In the second embodiment, the bump 43 formed by the ball bond formed by the hitting point on the piezoelectric element 214 when the bonding wire 42 is formed is the mechanically weak center of the pressure chamber 211 in plan view as described above. When the same load is applied, the amount of bending of the diaphragm 215 is reduced as compared with the center. As a result, the deformation force acting on the piezoelectric element 214 is also reduced, and an effect of suppressing the functional deterioration of the piezoelectric element 214 can be obtained.

  In the inkjet head 1 described above, the head substrate 2 having the piezoelectric elements 214 arranged on the upper surface is bonded to the holding substrate 3, and the wiring 41 of the external wiring member 4 bonded to the holding substrate 3 and each piezoelectric element 214 are connected. However, for example, the external wiring member 4 may be directly bonded to the head substrate 2, and the present invention provides each wiring 41 and each piezoelectric element 214 of the external wiring member 4. Any bonding wire 42 may be formed on the upper surface of the substrate by wire bonding using ball bonding, and the two may be electrically connected.

1: inkjet head 2: head substrate 21: body plate 211: pressure chamber 211a: bulging portion 212: common flow path 213: ink supply path 214: piezoelectric element (pressure generating means)
215: Diaphragm 216: Through hole 22: Intermediate plate 221: Communication hole 23: Nozzle plate 230: Nozzle formation surface (nozzle surface)
231: Nozzle 232: Large diameter portion 3: Holding substrate 31: Opening portion 32: Through hole 33: Recessed portion 4: External wiring member 41: Wiring 42: Bonding wire 43, 44: Bump 5: Ink chamber member 51: Channel port 52 :filter

Claims (9)

A plurality of nozzles for ejecting ink;
A plurality of pressure chambers respectively disposed corresponding to the nozzles and containing ink therein;
A plurality of pressure generating means arranged corresponding to each of the pressure chambers, and applying a pressure for ejecting ink in the pressure chamber by vibrating a wall surface between the pressure chambers as a vibration plate;
An external wiring member on which wiring for supplying power to the pressure generating means is formed;
A method of manufacturing an inkjet head, wherein the wiring of the external wiring member and the pressure generating means are electrically connected by a bonding wire formed by wire bonding using ball bonding,
The method of manufacturing an ink jet head, wherein the bonding wire is formed using the first bond of the wire bond as the pressure generating means side. The planar shapes of the pressure chamber and the pressure generating means are each substantially circular, the planar shape of the pressure generating means is smaller than the planar shape of the pressure chamber, and the pressure generating means is the pressure chamber in plan view. Are arranged so as to overlap
2. The method of manufacturing an ink jet head according to claim 1, wherein bumps are formed by disposing the hit points of the first bond at positions away from the center of the pressure chamber on the pressure generating means in plan view. 3. The method of manufacturing an ink jet head according to claim 2, wherein the bumps are formed by disposing the first bond hit points at positions satisfying the following conditional expression.

However, _{r a:} the radius r _b of the pressure generating means: the radius of the bump after the ball bond r _c: radius x _b of the pressure chambers, _{y b:} coordinates X _b bump with the origin at the center of the pressure generating means, _{Y b} : Bump coordinates with the center of the pressure chamber as the origin   4. The method of manufacturing an ink-jet head according to claim 1, wherein a load at a hit point of the first bond is 0.3 to 1.0 N. A plurality of nozzles for ejecting ink;
A plurality of pressure chambers respectively disposed corresponding to the nozzles and containing ink therein;
Corresponding to each of the pressure chambers, the pressure chambers are arranged so as to overlap with the pressure chambers in plan view, and a wall surface between the pressure chambers is vibrated as a vibration plate to apply pressure for ejecting ink in the pressure chambers. A plurality of pressure generating means;
An external wiring member on which wiring for supplying power to each of the pressure generating means is formed;
The planar shapes of the pressure chamber and the pressure generating means are each substantially circular, and the planar shape of the pressure generating means is smaller than the planar shape of the pressure chamber, and the wiring of the external wiring member, the pressure generating means, A method for manufacturing an ink jet head, wherein a bonding wire formed by wire bonding by ball bonding is electrically connected between the two,
A method of manufacturing an ink-jet head, comprising: forming a bump by ball bonding by disposing a hitting point at one end of the bonding wire at a position away from the center of the pressure chamber on the pressure generating means in plan view. 6. The method of manufacturing an ink jet head according to claim 5, wherein the position of the bump on the pressure generating means at one end of the bonding wire satisfies the following conditional expression.

However, _{r a:} the radius r _b of the pressure generating means: the radius of the bump after the ball bond r _c: radius x _b of the pressure chambers, _{y b:} coordinates X _b bump with the origin at the center of the pressure generating means, _{Y b} : Bump coordinates with the center of the pressure chamber as the origin   7. The method of manufacturing an ink jet head according to claim 5, wherein a load at one end of the bonding wire on the pressure generating means is 0.3 to 1.0 N. A plurality of nozzles for ejecting ink;
A plurality of pressure chambers respectively disposed corresponding to the nozzles and containing ink therein;
Corresponding to each of the pressure chambers, the pressure chambers are arranged so as to overlap with the pressure chambers in plan view, and a wall surface between the pressure chambers is vibrated as a vibration plate to apply pressure for ejecting ink in the pressure chambers. A plurality of pressure generating means;
An external wiring member on which wiring for supplying power to each of the pressure generating means is formed;
The planar shapes of the pressure chamber and the pressure generating means are each substantially circular, and the planar shape of the pressure generating means is smaller than the planar shape of the pressure chamber, and the wiring of the external wiring member, the pressure generating means, An ink jet head that is electrically connected by a bonding wire formed by wire bonding by ball bonding,
2. An ink jet head according to claim 1, wherein a ball bond bump formed by a hitting point on the pressure generating means at one end of the bonding wire is formed at a position away from the center of the pressure chamber in plan view. 9. The ink jet head according to claim 8, wherein the position of the bump on the pressure generating means at one end of the bonding wire satisfies the following conditional expression.

However, _{r a:} the radius r _b of the pressure generating means: the radius of the bump after the ball bond r _c: radius x _b of the pressure chambers, _{y b:} coordinates X _b bump with the origin at the center of the pressure generating means, _{Y b} : Bump coordinates with the center of the pressure chamber as the origin

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