Liquid ejecting head and method of manufacturing the same

Abstract

The invention discloses a liquid ejecting head and a method of manufacturing the same. A liquid ejecting head includes an ejecting element substrate, the ejection element substrate has a substrate, a vibration plate provided at the substrate, a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode in this order on a surface of the vibration plate opposite to the substrate, a first wiring electrically connected to the first electrode, a second wiring electrically connected to the second electrode, and a pad electrode electrically connected to the first wiring and / or the second wiring. The liquid ejecting head further includes an electrical wiring board electrically connected to the pad electrode with the mounting electrode interposed therebetween. The pad electrode has a higher hardness than the first wiring and the second wiring, and has a pad region bonded to the mounting electrode and a connection region bonded to the wiring electrically connected to the pad electrode.

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection head and a method of manufacturing a liquid ejection head. Background Art

[0002] As a liquid ejection head that performs printing by ejecting a liquid onto a printing medium, the following liquid ejection head is known: for example, a part of a pressure chamber communicating with a nozzle that ejects ink droplets is formed by a diaphragm. By being deformed by a piezoelectric element, this diaphragm allows pressure to be applied to the ink in the pressure chamber and allows ink droplets to be ejected from the nozzle. The piezoelectric element of such a liquid ejection head includes a piezoelectric diaphragm that is a diaphragm-shaped piezoelectric element and electrodes (also referred to as an upper electrode and a lower electrode) formed to sandwich the piezoelectric diaphragm from above and below. The piezoelectric diaphragm is driven by a voltage applied by the upper electrode and the lower electrode, and the piezoelectric element deforms the diaphragm and ejects droplets (ink droplets) from the nozzle. In this case, the voltage required for the piezoelectric diaphragm to be sufficiently displaced is several tens of volts. In the case of forming a piezoelectric film using a semiconductor, a relatively high voltage for semiconductor devices needs to be applied.

[0003] In addition, the liquid ejection head has a fine design so as to be able to print high-resolution images, and a plurality of piezoelectric elements are arranged at a high density. In recent years, the pitch between the nozzles of the piezoelectric elements in the arrangement direction of the piezoelectric elements has become increasingly narrow, and thus the density has become increasingly high, such as 600 nozzles per inch (npi), 1200 npi, or 2400 npi. Since the piezoelectric elements are thus arranged at a high density, the leads electrically connected to the piezoelectric elements and the pad electrodes for imparting an electrical signal (drive signal) from the outside to the piezoelectric elements are also arranged at a high density. A flexible board or the like is mounted on the pad electrodes so as to be connected to an external drive circuit and impart an electrical signal to the piezoelectric elements. One method of mounting a flexible board is a wire bonding method. Other methods of mounting a flexible board include a method using an anisotropic conductive film (ACF) or an anisotropic conductive paste (AFP) and a method using a non-conductive film (NCF) or a non-conductive paste (NCP). Note that the method using ACF or ACP is also referred to as anisotropic conductive film / paste (ACF / ACP), and the method using NCF or NCP is also referred to as non-conductive film / paste (NCF / NCP).

[0004] When the pitch between adjacent pad electrodes among a plurality of pad electrodes is about 50 μm or less, it is difficult to adopt a mounting method using wire bonding due to the size of quick bonding. In the case of a mounting method using wire bonding, a measure that can be taken is to arrange the pad electrodes in a staggered layout, but this increases the possibility of short - circuit between adjacent pad electrodes (bonding wires). In addition, as described earlier, a relatively high voltage is required to sufficiently deform the piezoelectric diaphragm, and this relatively high voltage is also applied to the pad electrodes. For this reason, in the case of ACF / ACP having conductive particles present in the adhesive, leakage current or the like may occur. For these reasons, when the pitch between adjacent pad electrodes is about 50 μm or less, from the perspective of reliability, NCF / NCP is generally used. For example, Japanese Patent Laid - Open No. 2017 - 132050 discloses using NCF / NCP for mounting when the drive contacts (pad electrodes) of a piezoelectric element are arranged at a fine pitch.

[0005] In addition, in the manufacture of a liquid ejection head, electrical inspection, aging, screening, etc. are performed on the piezoelectric element to ensure the reliability of the liquid ejection head. For example, Japanese Patent Laid - Open No. 2009 - 184247 discloses aging and screening of the piezoelectric element after forming the pressure chamber. Note that in the aging of the piezoelectric element, an electrical signal (also referred to as a drive signal) with a voltage and frequency higher than those applied in actual use is applied to the piezoelectric diaphragm. In addition, in the aging of the piezoelectric element, the piezoelectric element may be heated. This polarizes the piezoelectric diaphragm and relieves the internal stress in various thin films constituting the piezoelectric element, so as to reduce the fluctuations of the piezoelectric element that occur over time under actual use conditions. In the screening of the piezoelectric element, the piezoelectric diaphragm is driven under conditions more stringent than those for aging to eliminate non - compliant piezoelectric elements. When performing electrical inspection, etc. midway through the process of manufacturing a liquid ejection head, an electrical signal is applied to the piezoelectric element by detection, where a probe used to apply the electrical signal contacts the pad electrode connected to the lead. Summary of the Invention

[0006] Materials with low resistivity (e.g., gold (Au), aluminum (Al), or copper (Cu)) are generally used for wires and pad electrodes. Many of the above - mentioned materials with low resistivity are relatively soft materials, and their Vickers hardness is about 20 HV to 30 HV. Therefore, the pad electrode may be physically damaged (e.g., scratched) by detection, and an unevenness with a height difference of 1 μm or more, that is, a probe mark, may be formed at the pad electrode. When a flexible board is mounted at the pad electrode where a probe mark is formed, the unevenness of the probe mark may cause connection failure.

[0007] A liquid ejection head according to one aspect of the present disclosure includes: an ejection element substrate having a substrate in which a pressure chamber is formed, the pressure chamber communicating with an ejection port from which droplets are ejected; a diaphragm provided on one surface side of the substrate; a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode in this order on a surface of the diaphragm opposite to the substrate; a first wiring electrically connected to the first electrode; a second wiring electrically connected to the second electrode; and a pad electrode electrically connected to at least one of the first wiring and the second wiring, the pad electrode including a layer formed of the same material as the first electrode; and an electric wiring board electrically connected to the pad electrode with a mounting electrode interposed therebetween. The pad electrode has a higher hardness than the first wiring and the second wiring, and the pad electrode has a pad region and a connection region, the mounting electrode being joined to the pad region and the wiring electrically connected to the pad electrode being joined to the connection region.

[0008] More features of the present disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A and Figure 1B is a schematic diagram showing a flow path configuration of a liquid ejection head;

[0010] Figure 2A and Figure 2B is a schematic diagram illustrating a liquid ejection head;

[0011] Figure 3 is a schematic diagram showing a state in which a flexible board is mounted on a mounting electrode;

[0012] Figures 4A to 4D is a step-by-step cross-sectional view illustrating steps of manufacturing a liquid ejection head;

[0013] Figures 5A to 5D is a step-by-step cross-sectional view illustrating steps of manufacturing a liquid ejection head;

[0014] Figure 6A and Figure 6B is a step-by-step cross-sectional view illustrating steps of manufacturing a liquid ejection head;

[0015] Figure 7A and Figure 7B is a plan view of a liquid ejection head;

[0016] Figure 8 is a plan view of a liquid ejection head;

[0017] Figures 9A to 9Cis a plan view of a pad electrode;

[0018] Figure 10 is a plan view of a pad electrode;

[0019] Figure 11A and Figure 11B is a schematic cross-sectional view showing a comparative example of an electrical inspection; and

[0020] Figure 12 is a view showing a liquid ejection head. DETAILED DESCRIPTION

[0021] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the following embodiments do not limit the matters of the present disclosure, and not all combinations of the features described in the following embodiments are necessary for the solution provided by the present disclosure. Note that the same reference numerals are used to describe the same configurations.

[0022] <<Comparative Example>>

[0023] Figure 11A and Figure 11B is a schematic cross-sectional view showing a comparative example of an electrical inspection. Figure 11A is a schematic cross-sectional view showing a comparative example of an electrical inspection using a probe 231. Figure 11B is a schematic cross-sectional view showing how a probe mark 232 is generated by an electrical inspection. In Figure 11A and Figure 11B In the comparative example shown, a pad electrode 211 having a typical aluminum electrode layer is formed on the upper surface side of a substrate 200, and an insulating layer 201 is interposed therebetween. Note that the substrate 200 is formed of silicon (Si) or the like. As Figure 11A shown, in the probing, the probe 231 is brought into contact with the pad electrode 211 and scanned in the arrow direction ( Figure 11A the +X-direction in

[0024] As Figure 11BAs shown in [Fig.], in the detection region 233, the pad electrode 211 may be scratched and deformed. As a result, a large unevenness, i.e., a probe mark 232, may be formed, where the residue of the scratch is a protrusion. When a flexible board (not shown) is mounted on the pad electrode 211 where the probe mark 232 is formed, the unevenness of the probe mark 232 may cause a connection failure. In addition, in the case where a mounting electrode is formed at the pad electrode 211 using gold plating or the like to improve the connection reliability with the electrode of the flexible board, the flexible board is mounted on the pad electrode 211, bringing the mounting electrode of the pad electrode 211 into contact with the electrode of the flexible board. In the case where a mounting electrode is formed using gold plating or the like, the probe mark 232 may cause abnormal growth of the mounting electrode, and unevenness may also be formed at the mounting electrode. When the flexible board is mounted on the pad electrode 211 using NCF / NCP, the unevenness formed at the mounting electrode makes it easier for the NCF or NCP to enter between the mounting electrode of the pad electrode 211 and the electrode of the flexible board. This may make a connection failure more likely to occur.

[0025] In the present embodiment, a configuration of increasing the hardness of the pad electrode to provide a liquid ejection head having high electrical reliability is described.

[0026] <<Embodiment>>

[0027] <Configuration of Liquid Ejection Head>

[0028] As Figure 12 shown, the liquid ejection head 1000 is formed by an array of a plurality of element substrates 1 each having a plurality of ejection elements and an array of a plurality of ejection ports 11. Each element substrate 1 is generally connected to a flexible board 160 (see Figure 3 to be referred to later), and is also connected to an electric wiring board (not shown). The electric wiring board has a power supply terminal for supplying power and a signal input terminal for receiving a drive signal. At the same time, a circulation flow path (not shown) is formed in an ink supply unit (not shown) to supply ink containing a color material and supplied from an ink tank (not shown) to each element substrate 1 and to collect the ink not consumed in printing.

[0029] With the above configuration, based on print data input from the signal input terminal, each of the ejection elements disposed at the element substrate 1 uses the power supplied from the power supply terminal to eject the ink supplied from the ink supply unit from the ejection port in the -Z direction. Note that the dimensional values of each of the above parts are only examples and can be changed as needed according to the required specifications. In addition, although ink is ejected here as an example of the liquid, the present disclosure is not limited thereto, and for example, a primer can be ejected as the liquid.

[0030] <Flow Path Configuration of Liquid Ejection Head>

[0031] Figure 1A and Figure 1B is a schematic diagram showing the flow channel configuration of the element substrate 50 included in the element substrate 1 of the liquid ejection head 1000 of the present embodiment. Figure 1A is a cross-sectional view of the element substrate 50 as viewed from the ejection port 11 side of the flow channel block 10. Figure 1B is along Figure 1A The cross-sectional view taken along IB-IB in. The element substrate (ejection element substrate) 50 includes three substrates (the first flow channel substrate 20, the second flow channel substrate 100, and the third flow channel substrate 40), and the flow channels are formed by the combination of these substrates. As shown in Figure 1A The flow channel block 10 includes ejection ports 11 arranged in the Y direction and pressure chambers 12 and supply channels 13 prepared to communicate with the corresponding ejection ports 11. Each of the supply channels 13 is connected to the common liquid chamber 14 and supplies liquid (hereinafter also referred to as ink) to the corresponding pressure chamber 12. The arrows in FIG. 1 indicate the flow of the liquid (ink).

[0032] As shown in Figure 1B In the present embodiment, the element substrate 50 is configured such that the first flow channel substrate 20, the second flow channel substrate 100, and the third flow channel substrate 40 are stacked in the Z direction. The first flow channel substrate 20 is a substrate including the ejection port 11 for ejecting ink. The second flow channel substrate 100 is a substrate on which the piezoelectric element 105 and the pressure chamber 12 are formed. The third flow channel substrate 40 is a substrate that isolates the piezoelectric diaphragm 103 of the piezoelectric element 105 from the ink, and is also a substrate including a flow channel through which the ink is supplied from the common liquid chamber 14 to the pressure chamber 12. Note that the first flow channel substrate 20, the second flow channel substrate 100, and the third flow channel substrate 40 are formed using silicon (Si) or the like.

[0033] The supply channels 13, the pressure chambers 12, and the ejection ports 11 are formed corresponding to each piezoelectric element 105. The adjacent pressure chambers 12 are separated from each other by partition walls and are not directly affected by the adjacent piezoelectric elements 105. The piezoelectric element 105 is formed adjacent to the insulating film 101 serving as a vibration plate.

[0034] In the steady state, the ink accommodated in the pressure chamber 12 forms a meniscus at the ejection port 11. When a voltage waveform is applied to the piezoelectric element 105 according to a drive signal, the piezoelectric element 105 deforms, allowing the pressure chamber 12 to expand or contract via the insulating film 101. By combining the expansion operation and the contraction operation, droplets (ink droplets) 60 are generated from the meniscus and ejected in the -Z direction.

[0035] After the ink in the pressure chamber 12 is consumed by the ejection operation, the ink is supplied from the common liquid chamber 14 due to the capillary action of the ejection orifice 11, and a meniscus is formed again at the ejection orifice 11. Note that, in the present embodiment, the ejection orifice 11, the piezoelectric element 105, and the pressure chamber 12 are collectively referred to as an ejection element.

[0036] In the present embodiment, the diameter of the ejection orifice 11 may be 25 μm and the thickness may be 30 μm, and the thickness of the first flow channel substrate 20 may be 100 μm. In addition, the viscosity of the ink used may be 4 cp, and the minimum ink ejection amount from each ejection orifice 11 may be 3 pl.

[0037] In the present embodiment, the driving frequency of each piezoelectric element 105 may be 30 kHz. Such a driving frequency may be appropriately set based on the time required for each ejection element to be refilled with new ink and ready for the next ejection operation after actually ejecting the ink when a voltage is applied to the piezoelectric element 105.

[0038] <Configuration of the element substrate>

[0039] Figure 2A and Figure 2B are schematic views showing the liquid ejection head of the present embodiment. Figure 2A is a plan view schematically showing the liquid ejection head. Figure 2B is along Figure 2A in the cross-sectional view taken along IIB-IIB in. For easier understanding of the arrangement of the piezoelectric element 105, wiring, etc., Figure 2A and 2B only show the second flow channel substrate 100 of the element substrate 50 in a simplified manner, omitting the Figure 1A and Figure 1B the ejection orifice 11 and the supply flow channel 13 shown in.

[0040] As Figure 2A and Figure 2B shown in, the liquid ejection head of the present embodiment includes a second flow channel substrate 100, an insulating film 101, and a plurality of piezoelectric elements 105. The liquid ejection head of the present embodiment further includes a first wiring 112, a second wiring 114, a pad electrode 115, and a mounting electrode 116. As Figure 2B shown in, the insulating film 101 serving as a diaphragm is formed on the upper surface side (one surface side) of the second flow channel substrate 100. For the insulating film 101, for example, typical insulating materials such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or an aluminum oxide film are used. In addition, the insulating film 101 may be a laminated multilayer film having at least two of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and an aluminum oxide film.

[0041] The first electrode 102, the piezoelectric diaphragm 103, and the second electrode 104 are sequentially disposed on the surface of the insulating film 101, and the first electrode 102, the piezoelectric diaphragm 103, and the second electrode 104 form each piezoelectric element 105. Note that, at a portion of the second flow channel substrate 100 on the side opposite to the piezoelectric element 105, a plurality of pressure chambers 12 are formed corresponding to the plurality of piezoelectric elements 105. At the surface of the pressure chamber 12 on the side opposite to the piezoelectric element 105, a plurality of ejection ports 11 ( Figure 2A or Figure 2B not shown in the figure) are disposed corresponding to the plurality of pressure chambers 12. The pressure chamber 12 and the ejection port 11 thus communicate with each other.

[0042] The first electrode 102 is formed on the upper surface of the insulating film 101, or in other words, on the surface of the insulating film 101 opposite to the second flow channel substrate 100. The material of the first electrode 102 may be platinum (Pt) or iridium (Ir). The material of the first electrode 102 may also be a platinum alloy or an iridium alloy. The first electrode 102 also serves as a film for controlling the alignment of the crystal orientation of the piezoelectric diaphragm 103. When the material of the piezoelectric diaphragm 103 is lead zirconate titanate, the material of the first electrode 102 is preferably platinum, iridium, a platinum alloy, or an iridium alloy. Note that the film for controlling the alignment of the crystal orientation of the piezoelectric diaphragm 103 is also referred to as a crystal orientation control film. In addition, as an adhesive layer for ensuring the adhesive strength between the insulating film 101 and the first electrode 102, a thin film (not shown) of titanium (Ti), chromium (Cr), etc. may be formed between the insulating film 101 and the first electrode 102.

[0043] The piezoelectric diaphragm 103 is formed on the upper surface of the first electrode 102, or in other words, on the surface of the first electrode 102 opposite to the insulating film 101. A known material of the piezoelectric diaphragm 103 is lead zirconate titanate ceramic. The piezoelectric diaphragm 103 as a diaphragm-shaped piezoelectric layer can be formed by vacuum sputtering film formation, film formation using a sol-gel solution, CVD film formation, etc. The thickness of the piezoelectric diaphragm 103 is determined by the piezoelectric characteristics required to obtain the desired displacement and the voltage to be applied. For example, the thickness of the piezoelectric diaphragm 103 may be about 1 μm to 2 μm.

[0044] The second electrode 104 is formed on the upper side of the piezoelectric diaphragm 103, or in other words, on the surface of the piezoelectric diaphragm 103 opposite to the first electrode 102. The material of the second electrode 104 can be platinum, titanium, or tungsten (W). The material of the second electrode 104 can also be a platinum alloy, a titanium alloy, or a tungsten alloy. In this way, the material of the second electrode 104 is preferably platinum, titanium, tungsten, a platinum alloy, a titanium alloy, or a tungsten alloy. Note that a titanium alloy is generally used as the material of the second electrode 104. Additionally, as an adhesive layer for ensuring the adhesion strength between the second electrode 104 and the piezoelectric diaphragm 103, a thin film (not shown) of titanium, chromium, etc. can be formed between the second electrode 104 and the piezoelectric diaphragm 103.

[0045] As Figure 2A shown, a plurality of piezoelectric elements 105 are arranged at a high density for printing high-resolution images. To provide an easily understandable illustration of the present embodiment, Figure 2A an example in which the piezoelectric elements 105 are arranged in two arrays in a staggered manner in a planar manner is shown. The piezoelectric elements 105 can be arranged in four arrays or eight arrays, or the liquid ejection head can have piezoelectric elements 105 arranged at a higher density.

[0046] As Figure 2A shown, the first wiring 112 electrically connected to the first electrode 102 is led to the -X direction end of the upper surface of the insulating film 101. At the same time, the second wiring 114 electrically connected to the second electrode 104 is led to the -X direction end of the upper surface of the insulating film 101 and extends on the insulating layer 110. Note that the first wiring 112 and the second wiring 114 are also referred to as leads. Each of the first wirings 112 is a common wiring led out from a plurality (e.g., four) of piezoelectric elements 105 (first electrode 102). The first wiring 112 functions as a common electrode for applying a common electric signal to the plurality of piezoelectric elements 105. Each of the second wirings 114 is an individual wiring led out from an individual piezoelectric element 105 (second electrode 104). The second wiring 114 functions as an individual electrode for applying an electric signal to the individual piezoelectric element 105. Typical metal materials can be used for the first wiring 112 and the second wiring 114. To reduce the influence of effects such as signal delay and voltage drop caused by the wiring resistance, a metal having a relatively low resistivity can be used for the first wiring 112 and the second wiring 114. For example, the materials of the first wiring 112 and the second wiring 114 can be gold, aluminum, or copper. Additionally, the materials of the first wiring 112 and the second wiring 114 can be a gold alloy, an aluminum alloy, or a copper alloy. In this way, the materials of the first wiring 112 and the second wiring 114 are preferably gold, aluminum, copper, a gold alloy, an aluminum alloy, or a copper alloy. Furthermore, as an adhesive layer for improving the adhesion of the first wiring 112 and the second wiring 114, a thin film (not shown) of titanium, chromium, etc. can be formed at the lower surfaces of the first wiring 112 and the second wiring 114.

[0047] The insulating layer 110 is formed at the -X direction side portion of the piezoelectric element 105. For the insulating film 110, for example, typical insulating materials such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or an aluminum oxide film are used. In addition, the insulating film 110 may be a laminated multilayer film having at least two of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and an aluminum oxide film. Note that, for reasons such as the convenience of manufacturing the liquid ejection head and the protection of the components of the liquid ejection head, the insulating layer may be formed between the first wiring 112 and the first electrode 102 and between the second wiring 114 and the second electrode 104. In this case, the first wiring 112 and the first electrode 102 may be joined to each other via a contact hole formed in and penetrating the insulating layer between the first wiring 112 and the first electrode 102, and the second wiring 114 and the second electrode 104 may be joined to each other via a contact hole formed in and penetrating the insulating layer between the second wiring 114 and the second electrode 104. In addition, a protective insulating layer may be formed to cover the upper surface side of the first wiring 112 or the second wiring 114. The insulating layer and the protective insulating layer having contact holes formed therethrough are not depicted to provide an easily understandable illustration of the present embodiment.

[0048] Each pad electrode 115 for applying an external electrical signal is electrically connected to the first wiring 112 or the second wiring 114. Note that the pad electrode 115 electrically connected to the first wiring 112 may be referred to as the first pad electrode, and the pad electrode 115 electrically connected to the second wiring 114 may be referred to as the second pad electrode. The plurality of pad electrodes 115 are arranged in parallel in a region on the upper surface of the insulating film 101 different from the region having the piezoelectric element 105, or specifically, in a region along the peripheral portion of one side (-X direction side) of the second flow channel substrate 100. The direction in which the pad electrodes 115 are arranged is the direction along the peripheral portion of one side (-X direction side) of the second flow channel substrate 100 extending in the Y direction (therefore the Y direction). Although Figure 2A and Figure 2BIn this case, the pad electrodes 115 are only arranged on one side of the second flow channel substrate 100 (insulating film 101), but the present disclosure is not limited thereto. For example, the pad electrodes 115 may be divided and arranged on both sides of the second flow channel substrate 100 (-X direction side and +X direction side). Note that when the pad electrodes 115 are arranged on one side of the second flow channel substrate 100 (insulating film 101), the pad electrodes 115 are aggregated on one side of the second flow channel substrate 100, which reduces the size of the chip-shaped liquid ejection head (element substrate 50). In addition, since the pad electrodes 115 are aggregated on one side of the second flow channel substrate 100, the number of flexible boards mounted on the mounting electrodes 116 can be reduced, thereby enabling a reduction in the man-hours for mounting the flexible boards on the mounting electrodes 116. Therefore, the manufacturing cost of the liquid ejection head can be reduced.

[0049] The pad electrodes 115 are formed of the same layer as the first electrode 102. Therefore, similar to the first electrode 102, the material of the pad electrodes 115 is preferably platinum, iridium, a platinum alloy, or an iridium alloy. In addition, similar to the first electrode 102, as an adhesive layer for ensuring the adhesion strength between the insulating film 101 and the pad electrodes 115, a thin film (not shown) of titanium, chromium, etc. may be formed between the insulating film 101 and the pad electrodes 115. Note that being formed of the same layer as the first electrode 102 means being formed of the layer that is the raw material of the first electrode 102, or specifically, being formed of the first electrode layer 102E described later (see Figure 4B and Figure 4C ).

[0050] Furthermore, each of the pad electrodes 115 is formed in such a manner that it extends longer in the X direction than in the Y direction. Each pad electrode 115 has a pad region 150 and a connection region 151 arranged side by side in the X direction. The pad region 150 is formed on the -X direction side of the pad electrode 115. The mounting electrode 116 for applying an external electrical signal to the piezoelectric element 105 is bonded to the upper surface of the pad region 150. The connection region 151 is formed on the +X direction side of the pad electrode 115. The -X direction end portion of the first wiring 112 or the second wiring 114 is bonded to the upper surface of the connection region 151.

[0051] Preferably, in the direction (X direction) intersecting the arrangement direction of the pad electrodes 115, the ratio of the length of the connection region 151 to the length of the pad electrode 115 is 0.2 or less (20% or less). This makes the pad region 150 relatively long and allows the pad electrodes 115 to have sufficient space for the area of probe contact (detection area).

[0052] In addition, preferably, in the direction (X direction) intersecting with the arrangement direction of the pad electrodes 115, the ratio of the length of the mounting electrode 116 to the length of the pad electrode 115 is 0.5 or more (50% or more). This makes the area of the mounting electrode 116 sufficient, so that even when the arrangement pitch of the pad electrodes 115 is narrow, the electrical connection (mounting of the flexible board) with the mounting electrode 116 can be reliably established.

[0053] The mounting electrode 116 is formed on the upper surface of the pad region 150 and extends longer in the X direction than in the Y direction. Commonly used metallic materials can be used for the mounting electrode 116. For example, the material of the mounting electrode 116 can be gold, aluminum, or copper. The material of the mounting electrode 116 can also be a gold alloy, an aluminum alloy, or a copper alloy. In this way, the material of the mounting electrode 116 is preferably gold, aluminum, copper, a gold alloy, an aluminum alloy, or a copper alloy. In addition, as an adhesive layer for improving the adhesion between the mounting electrode 116 and the pad region 150, a thin film (not shown) of titanium, chromium, etc. can be formed between the mounting electrode 116 and the pad region 150. In addition, a flexible board is mounted on each mounting electrode 116. The material of the mounting electrode 116 is selected in consideration of the electrode material of the flexible board to be mounted on the mounting electrode 116, the method for mounting the flexible board, etc. In the case of using NCF / NCP as the method for mounting the flexible board, it is preferable that the mounting electrode 116 is formed by gold plating or the like and is joined to the pad region 150.

[0054] In the liquid ejection head, each of the piezoelectric elements 105 is driven by individual wirings (second wirings 114) that give individual signals to the piezoelectric elements 105 and common wirings (first wirings 112) that give common signals to a plurality of piezoelectric elements 105. In addition, in the case where there are a large number of piezoelectric elements 105, for some piezoelectric elements 105, a single common wiring is deployed due to problems such as the area where the wiring leads are deployed and the wiring resistance. For example, in Figure 2AWhen the piezoelectric elements 105 shown are arranged in two arrays, a single common wiring is deployed for four piezoelectric elements 105. Further, when the piezoelectric elements 105 are arranged in four arrays, a single common wiring can be deployed for eight piezoelectric elements 105. When the piezoelectric elements 105 are arranged in eight arrays, a single common wiring can be arranged for sixteen piezoelectric elements 105. Thus, the number of the first wiring 112 and the second wiring 114 is greater than the number of the piezoelectric elements 105, and the number of the pad electrodes 115 corresponding to the first wiring 112 and the second wiring 114 is also greater than the number of the piezoelectric elements 105. As an example, the case where the piezoelectric elements 105 are deployed at 600 npi and a single common wiring is deployed for eight piezoelectric elements 105 is described. In this case, when the pad electrodes 115 connected to the common wiring (the first wiring 112) and the pad electrodes 115 connected to the individual wiring (the second wiring 114) are arranged side by side in an array, the array pitch of the pad electrodes 115 is about 50 μm or 50 μm or less. When the array pitch of the pad electrodes 115 is about 50 μm or less, as described earlier, NCF / NCP is generally used as a method for mounting the flexible board.

[0055] In the present embodiment, an electrical inspection of the piezoelectric elements 105 is performed before forming the mounting electrodes 116. In the step of performing the electrical inspection, a probe for applying an electrical signal is brought into contact with the pad region 150 of the pad electrode 115 to perform an electrical inspection, aging, screening, etc. of the piezoelectric elements 105. After the step of performing the electrical inspection, the mounting electrodes 116 are formed on the pad region 150 of the pad electrode 115.

[0056] As described earlier, in the step of performing the electrical inspection, the probe reaches the pad region 150 where there is no first wiring 112 or second wiring 114. The materials of the first wiring 112 and the second wiring 114 (such as gold, aluminum, or copper) are soft metal materials having relatively low resistivity. For example, gold has a resistivity of 2.44×10 -8 Ω·m and a Vickers hardness of about 22 HV. Aluminum has a resistivity of 2.65×10 -8 Ω·m and a Vickers hardness of about 25 HV, and copper has a resistivity of 1.68×10 -8 Ω·m and a Vickers hardness of about 38 HV.

[0057] Meanwhile, the pad electrode 115 is formed of the same layer as the first electrode 102. Thus, the material of the pad electrode 115 (such as platinum or iridium) has relatively high resistivity and is a hard material having a Vickers hardness of 45 HV or greater. For example, platinum has a resistivity of 1.06×10 -7 Ω·m and a Vickers hardness of about 50 HV. Iridium has a resistivity of 5.20×10-8 a resistivity of Ω·m and a Vickers hardness of about 180 HV.

[0058] Tungsten, which is commonly used as a probe material, is a harder metal than the metal (such as platinum or iridium) of the pad electrode 115. Tungsten has a Vickers hardness of about 350 HV. During probing, the probe contacts the pad region 150 of the pad electrode 115 and slides against the surface of the pad region 150. Therefore, the pad electrode 115 does not need to be as hard as the probe. In the case where the pad electrode 115 is a flat thin film having a Vickers hardness of about 45 HV or greater, physical damage to the pad electrode 115 caused by probing - that is, probing marks can be reduced.

[0059] Therefore, the piezoelectric element 105 can be electrically inspected, aged, screened, etc. without generating probe marks on the pad electrode 115. Then, after the step of electrical inspection, the mounting electrode 116 for external connection is formed on the pad region 150 of the flat pad electrode 115 without any probe marks. Therefore, the formed mounting electrode 116 is uniform and has a flat surface.

[0060] Figure 3 is a schematic diagram showing a state in which the flexible board 160 is mounted on the mounting electrode 116. In Figure 3 the example shown, NCF / NCP is used as a method for mounting the flexible board 160. The flexible board 160 is mounted on the mounting electrode 116 using a non-conductive adhesive 165 that is an NCF or NCP. In the mounting of the flexible board 160 on the mounting electrode 116, the electrode 161 of the flexible board 160 can be brought into contact with the flat and uniform surface of the mounting electrode 116, which helps to prevent the occurrence of connection failures caused during the mounting of the flexible board 160.

[0061] <Method of manufacturing a liquid ejection head>

[0062] Next, use Figures 4A to 6B to describe a method of manufacturing a liquid ejection head. Figures 4A to 6B is a step-by-step cross-sectional view illustrating the steps of manufacturing a liquid ejection head.

[0063] As Figure 4A shown, a substrate 100E made of single crystal silicon is prepared as a raw material for the second flow channel substrate 100. The substrate 100E as a raw material for the second flow channel substrate 100 is hereinafter simply referred to as the substrate 100E. A thermal oxide film is formed on the upper surface (one of the surfaces) of the substrate 100E by a wet oxidation method using oxygen and hydrogen. Thus, the insulating film 101 is formed.

[0064] In addition, the layer that is the raw material of the first electrode 102 and the pad electrode 115 is referred to as the first electrode layer 102E. The layer that is the raw material of the piezoelectric diaphragm 103 is referred to as the piezoelectric diaphragm layer 103E. The layer that is the raw material of the second electrode 104 is referred to as the second electrode layer 104E. The film that is the raw material of the insulating layer 110 is referred to as the material film 110E. The layer that is the raw material of the first wiring 112 and the second wiring 114 is referred to as the wiring layer 114E.

[0065] Next, as shown in Figure 4B In the insulating film 101, the first electrode layer 102E, the piezoelectric diaphragm layer 103E, and the second electrode layer 104E are sequentially formed in the +Z direction in a stacked manner. In the step of forming the first electrode layer 102E, the first electrode layer 102E is formed by sputtering to cover the insulating film 101. When the material of the piezoelectric diaphragm layer 103E is lead zirconate titanate, the material of the first electrode layer 102E used as the crystal orientation control film is preferably platinum, iridium, a platinum alloy, or an iridium alloy. As an adhesion layer for ensuring the adhesion strength between the first electrode layer 102E and the insulating film 101, a thin film (not shown) of titanium, chromium, etc. can be formed between the first electrode layer 102E and the insulating film 101. In the step of forming the piezoelectric diaphragm layer 103E, the piezoelectric diaphragm layer 103E is formed by using a sol-gel process or the like to cover the first electrode layer 102E, and the piezoelectric diaphragm layer 103E is fired to have a desired crystal orientation. In the step of forming the second electrode layer 104E, the second electrode layer 104E is formed by sputtering to cover the piezoelectric diaphragm layer 103E. A typical metal material can be used as the material of the second electrode layer 104E. Note that the material of the second electrode layer 104E is preferably platinum, titanium, tungsten, a platinum alloy, a titanium alloy, or a tungsten alloy.

[0066] Next, as shown in Figure 4C the second electrode layer 104E and the piezoelectric diaphragm layer 103E are patterned to form the second electrode 104 and the piezoelectric diaphragm 103. In the step of patterning the second electrode layer 104E and the piezoelectric diaphragm layer 103E, a desired resist pattern (not shown) is lithographically formed on the second electrode layer 104E. After the resist pattern is formed, etching is performed to remove the portions of the second electrode layer 104E and the piezoelectric diaphragm layer 103E that are not to be part of the second electrode 104 and the piezoelectric diaphragm 103.

[0067] Next, as shown in Figure 4DAs shown in [reference], the first electrode layer 102E is patterned to form the first electrode 102 and the pad electrode 115. In the step of patterning the first electrode layer 102E, another desired resist pattern (not shown) is lithographically formed on the first electrode layer 102E. After the resist pattern is formed, etching is performed to remove the portions of the first electrode layer 102E that are not to become the first electrode 102 and the pad electrode 115. As a result of this etching, the piezoelectric elements 105 and the pad electrode 115 are formed, each piezoelectric element 105 including the first electrode 102, the piezoelectric diaphragm 103, and the second electrode 104.

[0068] Next, as Figure 5A shown in [reference], a material film 110E is formed to cover the insulating film 101, the piezoelectric elements 105, and the pad electrode 115. In the step of forming the material film 110E, the material film 110E is formed by chemical vapor deposition (CVD) or the like. As the material film 110E, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, an aluminum oxide film, or the like is used.

[0069] Next, as Figure 5B shown in [reference], the material film 110E is patterned to form the insulating layer 110. In the step of patterning the material film 110E, a desired resist pattern (not shown) is lithographically formed on the material film 110E. After the resist pattern is formed, etching is performed to remove the portions of the material film 110E other than the portions to become the insulating layer 110.

[0070] Next, as Figure 5C shown in [reference], a wiring layer 114E is formed to cover the insulating film 101, the piezoelectric elements 105, the pad electrode 115, and the insulating layer 110. In the step of forming the wiring layer 114E, the wiring layer 114E is formed by sputtering. The material of the wiring layer 114E is preferably gold, aluminum, copper, a gold alloy, an aluminum alloy, or a copper alloy.

[0071] Next, as Figure 5D shown in [reference], the wiring layer 114E is patterned to form the first wiring 112 and the second wiring 114. In the step of forming the wiring layer 114E, a desired resist pattern (not shown) is lithographically formed on the wiring layer 114E. After the resist pattern is formed, etching is performed to remove the portions of the wiring layer 114E other than the portions to become the first wiring 112 and the second wiring 114. After the etching is performed, the portions of the wiring layer 114E covering the pad region 150 of the pad electrode 115 are removed, and the ends of the first wiring 112 or the second wiring 114 are joined to the connection regions 151 of each pad electrode 115.

[0072] Next, as Figure 6AAs shown in [FIGURE], an electrical inspection is performed. In the step of performing the electrical inspection, the probe 231 is brought into contact with the pad region 150 of each pad electrode 115 and scanned in the direction indicated by the arrow ( Figure 6A the +X direction in [FIGURE]). This electrically connects the probe 231 to the pad electrode 115. Here, the detection region 233 is set inside the pad region 150 of the pad electrode 115. The pad electrode 115 is formed of the same layer as the first electrode 102. Therefore, the material of the pad electrode 115 is a hard metal material having a Vickers hardness of 45 HV or greater, such as platinum or iridium. Thus, in the detection region 233, the pad electrode 115 is not scratched, and no probe marks 232 as shown in Figure 11B and described earlier are generated. By applying an electrical signal to the piezoelectric element 105 via the probe 231 in this state, electrical inspection, aging, screening, etc. are performed on the piezoelectric element 105.

[0073] Next, as shown in Figure 6B [FIGURE], the mounting electrode 116 is formed on the pad region 150 of the pad electrode 115. A commonly used metal material can be used as the material of the mounting electrode 116. As described earlier, in the case where NCF / NCP is used as the method for mounting the flexible board, it is preferable that the mounting electrode 116 is formed by gold plating or the like and bonded to the pad region 150. In the step of forming the mounting electrode 116, a resist pattern is formed on the unnecessary region using a seed layer which is a laminated film formed of a titanium-tungsten alloy thin film and a gold thin film and formed by sputtering, and gold plating is applied. After applying the gold plating, the resist and the seed layer on the unnecessary region are removed to form the mounting electrode 116. Since the formation of the seed layer and the application of the gold plating are performed on the flat pad region 150 of the pad electrode 115 without probe marks, the formed mounting electrode 116 is flat and uniform.

[0074] Although the detailed description is omitted, after the mounting electrode 116 is formed, the substrate 100E is processed to form a pressure chamber. After the step of forming the pressure chamber, the substrate which is the raw material of the third flow channel substrate 40 is bonded to the upper surface side of the substrate 100E, and the substrate which is the raw material of the first flow channel substrate 20 is bonded to the lower surface side of the substrate 100E. By this, a composite substrate on which a plurality of chip-type liquid ejection heads (element substrates 50) are formed is formed. After the step of bonding the substrates, the plurality of element substrates 50 formed in the composite substrate are divided and separated. After the step of dividing and separating the plurality of element substrates 50, the flexible board is mounted on the mounting electrode 116 using NCF / NCP. Thus, after the formation of the mounting electrode 116, the liquid ejection head is completed by going through steps such as the step of forming the pressure chamber, the step of bonding the substrates, the step of dividing and separating the plurality of element substrates 50, and the step of mounting the flexible board.

[0075] In this embodiment, using NCF / NCP, the flexible board is mounted on the flat and uniform mounting electrode 116. This makes it possible to reduce connection failures caused during the mounting of the flexible board, and thus a liquid ejection head with high electrical reliability can be manufactured with good yield. In addition, each of the pad electrodes 115 has a pad region 150 joined to the mounting electrode 116 and a connection region 151 joined to the first wiring 112 or the second wiring 114. Therefore, even when the piezoelectric elements 105 are deployed at high density, in the step of performing electrical inspection, there is no need to provide additional pad electrodes for electrical inspection, and the pad region 150 of the pad electrode 115 can also be used as a pad electrode for electrical inspection.

[0076] As described above, according to the liquid ejection head and the method of manufacturing the liquid ejection head of this embodiment, a liquid ejection head with high electrical reliability can be provided. Specifically, in this embodiment, the pad electrode 115 is formed of the same layer as the first electrode 102. Therefore, a hard material with a relatively high resistivity can be used as the material of the pad electrode 115. Thus, electrical inspection, aging, screening, etc. can be performed on the piezoelectric element 105 without generating probe marks on the pad electrode 115. Then, after the step of performing electrical inspection, the mounting electrode 116 for external connection is formed on the pad region 150 of the flat pad electrode 115 without probe marks. Therefore, the formed mounting electrode 116 is flat and uniform. In the mounting of the flexible board 160 onto the mounting electrode 116, the electrode 161 of the flexible board 160 can be brought into contact with the flat and uniform mounting electrode 116. This makes it difficult for the non-conductive adhesive 165 to enter between the mounting electrode 116 and the electrode 161 of the flexible board 160, and reduces connection failures caused during the mounting of the flexible board 160. In this way, a liquid ejection head with high electrical reliability can be provided.

[0077] Although in the above embodiment, NCF / NCP is used as the method for mounting the flexible board 160, the present disclosure is not limited thereto. As the method for mounting the flexible board 160, ACF / ACP can be used, or a mounting method using a wire bonder can be used.

[0078] Although in the above embodiment, each of the first wirings 112 is a common wiring led out from a plurality of piezoelectric elements 105 and each of the second wirings 114 is an individual wiring led out from a single piezoelectric element 105, the present disclosure is not limited thereto. The first wiring 112 can be an individual wiring led out from a single piezoelectric element 105 and the second wiring 114 can be a common wiring led out from a plurality of piezoelectric elements 105.

[0079] Although in the above-described embodiment, the pad electrode 115 formed of the same layer as the first electrode 102 is electrically connected to both the first wiring 112 and the second wiring 114, the present disclosure is not limited thereto. The pad electrode 115 formed of the same layer as the first electrode 102 may be electrically connected to the first wiring 112 or the second wiring 114. For example, the pad electrode 115 formed of the same layer as the first electrode 102 may be electrically connected only to the second wiring 114. In this case, the mounting electrode may be bonded to the pad region provided at the -X direction side end portion of the first wiring 112. Further, in this case, ACF / ACP may be used as a method for mounting the flexible board.

[0080] <<Example>>

[0081] Next, a specific example of the liquid ejection head will be described using the drawings.

[0082] <Example 1>

[0083] Figure 7A And Figure 7B is a plan view of Example 1 corresponding to the above-described embodiment. Figure 7A is an overall plan view of the liquid ejection head of Example 1. Figure 7B is a close-up view of the pad electrode 115 of Example 1. The components in Example 1 are configured similarly to the components in the above-described embodiment, and are described using the same reference numerals as the reference numerals of the components in the above-described embodiment.

[0084] In Example 1, as Figure 7A shown, the piezoelectric elements 105 are arranged in four arrays in a staggered pattern at a density of 600 npi in the Y direction. The array pitch p1 of the piezoelectric elements 105 in the Y direction is approximately 42 μm. The size of the piezoelectric element 105 in the X direction is approximately 700 μm, and the size of the piezoelectric element 105 in the Y direction is approximately 50 μm. For the first wiring 112 which is a common wiring, a single first wiring 112 may be deployed for eight piezoelectric elements 105 due to the wiring routing layout and the wiring resistance. As Figure 7B shown, the pad electrodes 115 are arranged only on one side (-X direction side) of the second flow channel substrate 100 ( Figure 7B not shown in the figure). The arrangement pitch p2 of the pad electrodes 115 in the Y direction is approximately 38 μm.

[0085] Further, the liquid ejection head of Example 1 is manufactured in a manner similar to the method of manufacturing the liquid ejection head of the above-described embodiment. In the step of forming the insulating film 101 (see Figure 4A ), the film thickness of the thermally oxidized silicon film is 500 nm.

[0086] In the step of forming the first electrode layer 102E (see Figure 4B), platinum is used as the material of the first electrode layer 102E (i.e., the first electrode 102 and the pad electrode 115), and the thickness of the first electrode layer 102E is 100 nm. In addition, as an adhesive layer for ensuring the adhesion strength between the first electrode layer 102E and the insulating film 101, a titanium thin film (not shown) with a thickness of 10 nm is formed by sputtering. In the step of forming the piezoelectric diaphragm layer 103E (see Figure 4B ), lead zirconate titanate is used as the material for the piezoelectric diaphragm layer 103E (i.e., the piezoelectric diaphragm 103), and the thickness of the piezoelectric diaphragm layer 103E is 2 μm. In the step of forming the second electrode layer 104E (see Figure 4B ), a titanium-tungsten alloy is used as the material of the second electrode layer 104E (i.e., the second electrode 104), and the thickness of the second electrode layer 104E is 100 μm.

[0087] In the step of forming the material film 110E (see Figure 5A ), a silicon oxide film is used as the material film 110E, and the thickness of the material film 110E (i.e., the insulating layer 110) is 400 nm. In the step of forming the wiring layer 114E (see Figure 5C ), an aluminum alloy is used as the material of the wiring layer 114E (i.e., the first wiring 112 and the second wiring 114), and the thickness of the wiring layer 114E is 600 nm.

[0088] As a result, in the step of performing an electrical inspection (see Figure 6A ), the electrical inspection can be performed without scratching the pad electrode 115. In the step of forming the mounting electrode 116 (see 6B), the mounting electrode 116 is formed by gold plating or the like, and the thickness of the mounting electrode 116 is 5 μm. In this case, a seed layer is formed on the pad region 150 of the flat pad electrode 115 without probe marks and gold plating is applied, so that the formed mounting electrode 116 can be flat and uniform.

[0089] Then, in the step of mounting the flexible board, the flexible board can be mounted on the flat and uniform mounting electrode 116 using NCF / NCP. This makes it possible to reduce connection failures caused during the mounting of the flexible board, and thus a liquid ejection head with high electrical reliability can be manufactured with good yield.

[0090] As described above, according to Example 1, a liquid ejection head with high electrical reliability can be provided.

[0091] <Example 2>

[0092] Figure 8 is a plan view of Example 2 corresponding to the above-described embodiment. The components in Example 2 are configured similarly to those in Example 1, so only the parts different from Example 1 will be described.

[0093] In Example 2, as Figure 8 shown, the piezoelectric elements 105 are arranged in eight arrays in a staggered pattern at a density of 1200 npi in the Y direction. The array pitch of the piezoelectric elements 105 in the Y direction is approximately 21 μm. The pad electrodes 115 are divided and arranged on both sides (-X direction side and +X direction side) of the second flow channel substrate 100 ( Figure 8 not shown in the figure). On each side, the array pitch of the pad electrodes 115 in the Y direction is approximately 38 μm, which is similar to Example 1.

[0094] According to Example 2, as in Example 1, a liquid ejection head with high electrical reliability can be provided.

[0095] <Example 3>

[0096] Figures 9A to 9C is a plan view showing the pad electrode 115 of Example 3 corresponding to the above-described embodiment. Figure 9A is a plan view showing the pad region 150 and the connection region 151 of the pad electrode 115 of Example 3. Figure 9B is a plan view showing a state where the second wiring 114 (or the first wiring 112) is joined to the connection region 151 of the pad electrode 115 of Example 3. Figure 9C is a plan view showing a state where the mounting electrode 116 is joined to the pad region 150 of the pad electrode 115 of Example 3. The components in Example 3 are configured similarly to those in Example 1, so only the parts different from Example 1 will be described.

[0097] In Example 3, as Figure 9A shown, the pad region 150 is the region of the central part of the pad electrode 115 surrounded by a dashed line. The connection region 151 is the region outside the pad electrode 115 surrounding the periphery of the pad region 150. Then, as Figure 9B shown, the end of the second wiring 114 (or the first wiring 112) is formed at the connection region 151 of the pad electrode 115 so as to surround the pad region 150. Note that in the step of forming the first wiring 112 and the second wiring 114 (see Figure 5D ), the part of the wiring layer 114E covering the central side pad region 150 of the pad electrode 115 was etched away.

[0098] Furthermore, in the step of performing an electrical inspection (see Figure 6A ), the probe is brought into contact with the pad region 150 surrounded by the second wiring 114 (or the first wiring 112) and scanned in the X direction. Like in Example 1, this example also enables an electrical inspection without scratching the pad electrode 115. After the step of performing the electrical inspection, as Figure 9CAs shown, mounting electrodes 116 are formed at pad regions 150 surrounded by the second wiring 114 (or the first wiring 112). Similar to Example 1, a flat and uniform mounting electrode 116 can also be formed in this example.

[0099] According to Example 3, similar to Example 1, a liquid ejection head having a high resistance can be provided.

[0100] Furthermore, according to Example 3, the second wiring 114 (or the first wiring 112) is formed so as to surround the pad region 150. Therefore, a slight deviation does not prevent the pad electrode 115 from being electrically connected to the second wiring 114 (or the first wiring 112). In addition, since the connection area between the flexible board and the electrode is increased without changing the connection pitch, the pad electrode 115 needs to be formed to be elongated in the X direction. In this case, since the second wiring 114 (or the first wiring 112) having a resistivity lower than that of the pad electrode 115 is formed so as to surround the pad region 150, there is also an advantageous effect of reducing the resistance of the pad electrode 115 during the electrical inspection.

[0101] <Example 4>

[0102] Figure 10 is a plan view showing pad electrodes 115a and 115b of Example 4 corresponding to the above-described embodiment. The components in Example 4 are configured similarly to those in Example 1, and thus only the parts different from Example 1 will be described.

[0103] In Example 4, as Figure 10 shown, multiple sets of two arrays of pad electrodes 115a and 115b staggered in the X direction are arranged in the Y direction. The two arrays of pad electrodes 115a and 115b are formed similarly to the pad electrode 115 of the above-described embodiment. The mounting electrode 116a is joined to the pad region 150a of the pad electrode 115a located on the -X direction side. The first wiring 112 or the second wiring 114 is joined to the connection region 151a of the pad electrode 115a located on the -X direction side. The mounting electrode 116b is joined to the pad region 150b of the pad electrode 115b located on the +X direction side. The first wiring 112 or the second wiring 114 is joined to the connection region 151b of the pad electrode 115b located on the +X direction side. In this way, multiple sets of two arrays of mounting electrodes 116a and 116b staggered in the X direction are arranged in the Y direction. In addition, the two rows of mounting electrodes 116a and 116b are formed similarly to the mounting electrode 116 of the above-described embodiment.

[0104] According to Example 4, similar to Example 1, a liquid ejection head having high electrical reliability can be provided.

[0105] In addition, according to Example 4, due to the staggered arrangement of the pad electrodes 115a and 115b, the pad electrodes 115a and 115b can be arranged at a higher density in the Y direction without changing the sizes of the pad electrodes 115a and 115b. Note that, in the case of arranging the pad electrodes 115a and 115b in a staggered arrangement, for example, corresponding to the arrangement of the mounting electrodes 116a and 116b, bumps need to be formed at the wirings of the flexible board. In addition, due to the low rigidity of the flexible board, connection failures may occur. For these reasons, for example, a silicon board with high rigidity or an insertion board with wirings formed on a glass substrate can be used instead of the flexible board.

[0106] Although the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation so as to encompass all such modifications as well as equivalent structures and functions.

Claims

1. A liquid ejection head, comprising: An ejection element substrate having a substrate in which a pressure chamber is formed, the pressure chamber being communicated with an ejection port from which a droplet is ejected, a vibration plate provided on one surface side of the substrate, a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode in this order on a surface of the vibration plate opposite to the substrate, a first wiring electrically connected to the first electrode, a second wiring electrically connected to the second electrode, and a pad electrode electrically connected to at least one of the first wiring and the second wiring, the pad electrode including a layer formed of the same material as the first electrode; as well as an electric wiring board electrically connected to the pad electrode with the mounting electrode interposed therebetween, wherein The pad electrode has a higher hardness than the first wiring and the second wiring, and The pad electrode has a pad region to which the mounting electrode is bonded, and A connection region to which the wiring electrically connected to the pad electrode is bonded.

2. The liquid ejecting head according to claim 1, wherein The pad electrode is formed of platinum, iridium, a platinum alloy or an iridium alloy.

3. The liquid ejecting head according to claim 1, wherein The pad electrode has a Vickers hardness of 45 HV or greater.

4. The liquid ejecting head according to claim 1, wherein The wiring electrically connected to the pad electrode is formed of gold, aluminum, copper, a gold alloy, an aluminum alloy, or a copper alloy.

5. The liquid ejection head according to claim 1, further comprising Multiple pad electrodes, wherein the plurality of pad electrodes include the pad electrode, wherein the pad electrodes of the plurality of pad electrodes are arranged side by side, and Wherein a ratio of a length of the connection region to a length of each of the plurality of pad electrodes in a direction intersecting a direction in which the pad electrodes of the plurality of pad electrodes are arranged is 0.2 or less.

6. The liquid ejection head according to claim 1, further comprising Multiple pad electrodes, wherein the plurality of pad electrodes include the pad electrode, wherein the pad electrodes of the plurality of pad electrodes are arranged side by side, and wherein a ratio of a length of the mounting electrode to a length of each of the plurality of pad electrodes in a direction intersecting a direction in which the pad electrodes of the plurality of pad electrodes are arranged is 0.5 or greater.

7. The liquid ejection head according to claim 1, further comprising Multiple pad electrodes, wherein the plurality of pad electrodes include the pad electrode, wherein the pad electrodes of the plurality of pad electrodes are arranged side by side, and The arrangement pitch of the pad electrodes among the plurality of pad electrodes is 50 μm or less.

8. The liquid ejection head according to claim 1, further comprising Multiple pad electrodes, wherein the plurality of pad electrodes include the pad electrode, The pad electrodes among the plurality of pad electrodes are arranged side by side along a peripheral portion of one side of the substrate.

9. The liquid ejecting head according to claim 1, wherein The ejection element substrate has a plurality of piezoelectric elements. The plurality of piezoelectric elements include the piezoelectric element, The substrate has a plurality of ejection ports and a plurality of pressure chambers corresponding to the plurality of piezoelectric elements. the plurality of injection ports include the injection ports and the plurality of pressure chambers include the pressure chambers, The first wiring is a common wiring common to a plurality of piezoelectric elements among the plurality of piezoelectric elements, and The second wiring is an individual wiring for an individual piezoelectric element among the plurality of piezoelectric elements.

10. The liquid ejection head according to claim 1, wherein The mounting electrode is formed of a material different from a material of the wiring electrically connected to the pad electrode.

11. The liquid ejection head according to claim 1, wherein The mounting electrode is formed of at least one of gold, aluminum, copper, a gold alloy, an aluminum alloy, or a copper alloy.

12. The liquid ejection head according to claim 1, wherein The electric wiring board is a flexible board.

13. The liquid ejection head according to claim 12, wherein The flexible board is bonded to the ejection element substrate using an anisotropic conductive film, anisotropic conductive paste, a non-conductive film, or a non-conductive paste.

14. The liquid ejection head according to any one of claims 1 to 13, wherein The electric wiring board is electrically connected to the pad electrode in such a manner that the electric wiring board faces the pad electrode.

15. A liquid ejection head comprising: An ejection element substrate having a substrate in which a pressure chamber is formed, the pressure chamber being communicated with an ejection port from which a droplet is ejected, a vibration plate provided on one surface side of the substrate, a piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode in this order on a surface of the vibration plate opposite to the substrate, a first wiring electrically connected to the first electrode, a second wiring electrically connected to the second electrode, and a pad electrode electrically connected to at least one of the first wiring and the second wiring; as well as an electric wiring board electrically connected to the pad electrode with the mounting electrode interposed therebetween, wherein The pad electrode has a higher hardness than the first wiring and the second wiring, and the pad electrode has a pad region to which the mounting electrode is bonded, and a connection region to which the wiring electrically connected to the pad electrode is bonded, The first electrode is formed of platinum, iridium, a platinum alloy or an iridium alloy, and The pad electrode is formed of platinum, iridium, a platinum alloy or an iridium alloy.

16. A method for manufacturing a liquid ejection head, the liquid ejection head having a piezoelectric element, the piezoelectric element having a first electrode, a piezoelectric layer, and a second electrode in sequence, the method comprising: forming a first layer on a substrate; forming the piezoelectric layer and the second electrode on the first layer; patterning the first layer to form the first electrode covered by the piezoelectric layer and a pad electrode to be electrically connected to an electric wiring board; forming a second layer covering the pad electrode and the second electrode; patterning the second layer to form wiring that electrically connects the pad electrode and the piezoelectric element to each other; as well as The electrical wiring board is electrically connected to the pad electrode with the mounting electrode interposed therebetween, wherein The pad electrode has a pad region and a connection region, the mounting electrode is bonded to the pad region, the connection region is different from the pad region and the wiring is connected to the connection region, and In patterning the second layer, the wiring is connected to the connection region.

17. The method for manufacturing a liquid ejection head according to claim 16, wherein In forming the second layer, the second layer having a lower hardness than the first layer is formed.

18. The method for manufacturing a liquid ejection head according to claim 16, wherein In patterning the second layer, a portion of the second layer is removed, the portion covering the pad region of the pad electrode.

19. The method for manufacturing a liquid ejection head according to claim 16, further comprising: After the formation of the wiring, an electrical inspection is performed by bringing a probe into contact with the pad area; as well as After electrical inspection, the mounting electrodes are bonded to the pad areas.

20. The method for manufacturing a liquid ejection head according to any one of claims 16 to 19, further comprising: The electric wiring board is electrically connected to the pad electrode in such a manner that the electric wiring board faces the pad electrode.

Images