MEMS device, liquid ejecting head, and liquid ejecting apparatus

There is provided a MEMS device which includes a second substrate which is disposed with an interval from a first substrate, and an interposed member which is interposed between the first substrate and the second substrate, and which has space which is defined by the first substrate, the second substrate, and the interposed member, in which the first substrate includes a wiring which extends from a first surface side which is a surface on a side opposite to the second substrate toward a second surface side which is a surface of the second substrate side and is made of a conductor, in which an end portion of the first surface side of the wiring is covered by a first protective film provided on the first surface side, and in which an end portion of the second surface side of the wiring faces the space.

BACKGROUND

1. Technical Field

The present invention relates to a MEMS device in which space is formed between two bonded substrates, a liquid ejecting head, and a liquid ejecting apparatus.

2. Related Art

A micro electro mechanical systems (MEMS) device which includes two substrates and has space between these two substrates is applied to various apparatus (for example, liquid ejecting apparatus, sensor, or the like). For example, in a liquid ejecting head which is a type of MEMS device, an actuator such as a piezoelectric element is provided in the space described above. In addition, as the liquid ejecting apparatus on which such a liquid ejecting head is mounted, for example, there is an image recording apparatus such as an ink jet type printer and an ink jet type plotter. Recently, the liquid ejecting apparatus having a feature that a very small amount of liquid can be accurately landed to a predetermined position is developed and then is also applied to various manufacturing apparatus. For example, the liquid ejecting apparatus is applied to a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode forming apparatus for forming an electrode such as an organic electro luminescence (EL) display and a face emitting display (FED), and a chip manufacturing apparatus for manufacturing a biochip (biochemical element). Liquid ink is ejected from a recording head for the image recording apparatus and a solution of each color material of red (R), green (G), and blue (B) is ejected from a color material ejecting head for the display manufacturing apparatus. In addition, a liquid electrode material is ejected from an electrode material ejecting head for the electrode forming apparatus, and a solution of a biological organic material is ejected from a biological material ejecting head for the chip manufacturing apparatus.

As the MEMS device described above, there is a MEMS device which is provided with a wiring (hereinafter, also referred to as through wiring) passing through one of the two substrates in a plate thickness direction thereon. Meanwhile, without being limited to the through wiring of the MEMS device, the wiring formed on a substrate or the like is covered with a protective film for suppressing corrosion (see, for example, JP-A-8-181242). In particular, in a substrate having a through wiring, since both end portions of the through wiring (end portion on upper surface side of substrate and end portion on lower surface side of substrate) are exposed, the protective film is formed on both surfaces of the substrate in order to cover the both end portions of the through wiring as disclosed in JP-A-8-181242.

Here, it is preferable that the thickness of the protective film be reduced (that is, film thinning) from the viewpoint of improving the productivity and suppressing the manufacturing cost thereof. In particular, in a case where a metal having conductivity and corrosion resistance is used for the protective film so as to make the protective film function as a portion of the wiring, the manufacturing cost thereof tends to increase. In other words, metals having conductivity and corrosion resistance often include rare metals such as titanium (Ti) and tungsten (W), and thus the manufacturing cost is likely to be increased. Therefore, it is further preferable that the thickness of the protective film be decreased.

SUMMARY

An advantage of some aspects of the invention is to provide a MEMS device, a liquid ejecting head, and a liquid ejecting apparatus which can reduce a thickness of a protective film and reduce manufacturing cost thereof.

According to an aspect of the invention, there is provided a MEMS device which includes a first substrate; a second substrate which is disposed with an interval from the first substrate; and a interposed member which is interposed between the first substrate and the second substrate, and which has space which is defined by the first substrate, the second substrate, and the interposed member, in which the first substrate includes a wiring which extends from a first surface side which is a surface on a side opposite to the second substrate side toward a second surface side which is a surface of the second substrate side and is made of a conductor, in which an end portion of the first surface side of the wiring is covered by a first protective film provided on the first surface side, and in which an end portion of the second surface side of the wiring faces the space.

According to the configuration, since the end portion of the second surface side of the wiring faces the space, the end portion of the second surface side of the wiring is unlikely to be influenced by the environment outside the first substrate and the second substrate. Accordingly, the end portion of the second surface side of the wiring is unlikely to be corroded and the protective film covering the end portion of the second surface side of the wiring can be thinned. Alternatively, the protective film covering the end portion of the second surface side of the wiring can be eliminated. As a result, the manufacturing cost of the MEMS device can be reduced. In addition, the time for forming the protective film can be shortened, and the productivity of the MEMS device can be improved.

In addition, in the configuration, it is preferable that the end portion of the second surface side of the wiring be covered by a second protective film provided on the second surface side, and a film thickness of the second protective film be thinner than that of the first protective film.

According to the configuration, the manufacturing cost of the MEMS device can be reduced and the productivity of the MEMS device can be improved. In addition, as compared with a case where the end portion of the second surface side of the wiring is not covered with the protective film, corrosion resistance of the wiring can be improved.

Further, in the configuration, it is preferable that the second protective film have conductivity, a protrusion portion which protrudes from the second surface and is made of resin be formed, the second protective film extend from a position covering the end portion of the second surface side of the wiring to a position overlapping the projection portion, and the protrusion portion be connected to a terminal formed on the second substrate with the protective film interposed between the protrusion portion and the terminal.

According to the configuration, the second protective film can function as a bump electrode which is connected to the terminal. Since the film thickness of the second protective film is formed to be thinner than that of the first protective film, when the bump electrode is pressed against the terminal to be electrically connected, cracking and fracturing is unlikely to be generated in the second protective film. As a result, reliability of the connection between the second protective film serving as the bump electrode and the terminal can be increased.

In addition, in the configuration, it is preferable that the protrusion portion include a first resin surface which is a surface along the second surface, and a second resin surface which is a surface provided so as to intersect the second surface and an inner angle at an intersection point between the first resin surface of the protrusion portion and the second resin surface of the protrusion portion be 90 degrees or less in the extending direction of the second protective film.

According to the configuration, disconnection between the second protective film extending from the second surface of the first substrate to the position overlapping the protrusion portion can be suppressed at a boundary between the second surface and the protrusion portion.

According to another aspect of the invention, there is provided a liquid ejecting head which includes a nozzle for ejecting liquid, the liquid ejecting head including: a structure of the MEMS device of any one of the above configurations.

According to the configuration, the manufacturing cost of the liquid ejecting head can be reduced and the productivity of the liquid ejecting head can be improved.

In addition, according to still another aspect of the invention, there is provided a liquid ejecting apparatus, including: the liquid ejecting head of the above configuration.

According to the configuration, the manufacturing cost of the liquid ejecting apparatus can be reduced, and the productivity of the liquid ejecting apparatus can be improved.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, aspects for realizing the invention will be described with reference to the attached drawings. In the embodiments described below, although various limitations have been made as preferred specific examples of the invention, the scope of the invention is not limited to the aspects unless specifically stated to limit the invention in the following description. In addition, in the following description, a liquid ejecting head which is one category of a MEMS device, in particular, an ink jet type recording head (hereinafter recording head)3, which is a type of liquid ejecting head, will be described as an example.FIG. 1is a perspective view illustrating an ink jet printer (hereinafter, printer)1which is a kind of a liquid ejecting apparatus on which a recording head3is mounted.

The printer1is an apparatus that ejects ink (a type of liquid) onto a surface of a recording medium2(a kind of landing target) such as a recording paper and records an image or the like. The printer1includes a recording head3, a carriage4to which the recording head3is attached, a carriage moving mechanism5which moves the carriage4in the main scanning direction, a transport mechanism6which transports the recording medium2in the sub scanning direction, and the like. Here, the ink is stored in the ink cartridge7as a liquid supply source. The ink cartridge7is detachably mounted on the recording head3. A configuration in which the ink cartridge is disposed on the main body side of the printer and ink is supplied from the ink cartridge to the recording head through an ink supply tube can be adopted.

The carriage moving mechanism5includes a timing belt8. The timing belt8is driven by a pulse motor9such as a DC motor. Therefore, when the pulse motor9is operated, the carriage4is guided by a guide rod10installed on the printer1and thus reciprocates in the main scanning direction (in width direction of recording medium2). A position of the carriage4in the main scanning direction is detected by a linear encoder (not illustrated) which is a type of position information detecting means. The linear encoder transmits the detection signal thereof, that is, the encoder pulse (a kind of position information) to a control unit of the printer1.

Next, the recording head3will be described.FIG. 2is a cross-sectional view illustrating the configuration of the recording head3. In addition,FIG. 3is an enlarged sectional view of a main portion of the recording head3. In other words,FIG. 3is an enlarged sectional view of a periphery of the bump electrode37located at an end portion on a side of (left side inFIG. 2) of the recording head3. In the following description, a laminating direction of each member is suitably described as a vertical direction. As illustrated inFIG. 2, the recording head3in the present embodiment is attached to a head case16in a state where an actuator unit14and a flow path unit15are laminated.

The head case16is a box-like member made of synthetic resin, and a liquid introduction path18which supplies ink to each pressure chamber30is formed inside the head case16. The liquid introduction path18is space in which ink common to a plurality of pressure chambers30is stored along with a common liquid chamber25to be described below. In the present embodiment, two liquid introduction paths18are formed corresponding to the columns of pressure chambers30arranged in two columns in parallel. In addition, in a portion on the lower side of the head case16(side of flow path unit15), a accommodation space17which is recessed in a rectangular parallelepiped shape from the lower surface of the head case16(surface of the flow path unit15side) to the middle of the head case16in the height direction is formed. When the flow path unit15to be described below is bonded in a state of being positioned on the lower surface of the head case16, the actuator unit14(pressure chamber forming substrate29, sealing plate33, driving IC34, or the like) laminated on a communication substrate24is configured to be accommodated in a accommodation space17. Although not illustrated in the drawing, an opening which communicates the space outside the head case16and the accommodation space17with each other is formed in a portion of the ceiling surface of the accommodation space17. A wiring substrate such as a flexible printed board (FPC) (not illustrated) is inserted through the opening into the accommodation space17and is connected to the actuator unit14in the accommodation space17. Therefore, the accommodation space17is space opened to the atmosphere.

The flow path unit15in this embodiment includes the communication substrate24and a nozzle plate21. The nozzle plate21is a substrate which is bonded to the lower surface (surface opposite to pressure chamber forming substrate29) of the communication substrate24and is made of silicon. In the present embodiment, an opening on the lower surface side of space to be described below, which is the common liquid chamber25, is sealed by the nozzle plate21. In addition, a plurality of nozzles22are formed linearly (in a common) on the nozzle plate21. Two columns of the nozzles22(that is, nozzle columns) which includes the plurality of nozzles22are formed in the nozzle plate21. The nozzles22constituting each nozzle column are provided at a pitch corresponding to the dot formation density from the nozzle22of one end side to the nozzle22of the other end side, for example, at equal interval along the sub scanning direction. The nozzle plate21is bonded to a region that is deviated from the common liquid chamber25to the inside in the communication substrate24and the opening on the lower surface side of the space which becomes the common liquid chamber25can be sealed by a member such as a flexible compliance sheet.

The communication substrate24is a substrate which constitutes the upper portion (portion on head case16side) of the flow path unit15and is made of silicon. As illustrated inFIG. 2, a common liquid chamber25which communicates with the liquid introduction path18and stores ink common to the respective pressure chambers30, an individual communication path26which separately supplies ink from the liquid introduction path18to each pressure chamber30via the common liquid chamber25, and a nozzle communication path27which communicates the pressure chamber30and the nozzle22with each other are formed on the communication substrate24by etching or the like. A plurality of individual communication paths26and a plurality of nozzle communication paths27are formed along the nozzle column direction. In addition, the common liquid chamber25is an elongated empty portion along the direction of the nozzle column, and as illustrated inFIG. 2, it is formed in two columns corresponding to the columns of the pressure chambers30arranged in two columns in parallel.

As illustrated inFIG. 2, the actuator unit14in the present embodiment is bonded to the communication substrate24in a state where a pressure chamber forming substrate29, a vibration plate31, a piezoelectric element32which is a type of actuator, a sealing plate33, and a driving IC34are laminated to be a unit. The actuator unit14is formed to be smaller than the accommodation space17so as to be capable of being accommodated in the accommodation space17.

The pressure chamber forming substrate29is a substrate made of silicon which constitutes a lower portion (portion on flow path unit15side) of the actuator unit14. A plurality of spaces serving as the pressure chambers30are arranged in parallel along the nozzle column direction by a portion of the pressure chamber forming substrate29being removed in a plate thickness direction by etching or the like. A lower side of the space is defined by the communication substrate24and an upper side thereof is defined by the vibration plate31to constitute the pressure chamber30. In addition, this space, that is, the pressure chamber30is formed in two columns corresponding to the nozzle columns formed in two columns. Each of the pressure chambers30is an empty portion elongated in a direction orthogonal to the nozzle column direction, the individual communication path26, communicates with an end portion on a side, and the nozzle communication path27communicates with an end portion on the other side thereof in the longitudinal direction.

The vibration plate31is an elastic thin film substrate and is laminated on the upper surface (surface opposite to flow path unit15side) of the pressure chamber forming substrate29. An upper opening of the space serving as the pressure chamber30is sealed by the vibration plate31. In other words, the pressure chamber30is defined by the vibration plate31. A portion of the vibration plate31corresponding to the pressure chamber30(specifically, upper opening of pressure chamber30) functions as a displacement portion that is displaced in a direction away from or close to the nozzle22in accordance with flexural deformation of the piezoelectric element32. In other words, a region of the vibration plate31corresponding to the upper opening of the pressure chamber30becomes a driving region35in which the flexural deformation is permitted. On the other hand, a region of the vibration plate31deviated from the upper opening of the pressure chamber30becomes a non-driving region36where flexural deformation is inhibited. A substrate including the pressure chamber forming substrate29on which the vibrating plate31is laminated, that is, the vibrating plate31and the pressure chamber forming substrate29corresponds to the second substrate in the invention.

In addition, the vibration plate31includes, for example, an elastic film which is made of silicon dioxide (SiO2) formed on an upper surface of the pressure chamber forming substrate29and an insulating film which is made of zirconium oxide (ZrO2) formed on the elastic film. Piezoelectric elements32are laminated on a region corresponding to the respective pressure chambers30on the insulating film (surface on side opposite to pressure chamber forming substrate29side of vibration plate31), that is, the driving region35. The piezoelectric element32in the present embodiment is a so-called flexural mode of piezoelectric element. The piezoelectric element32is formed by a lower electrode layer, a piezoelectric layer, and an upper electrode layer, for example, on the vibration plate31being sequentially laminated. Any one of the upper electrode layer or the lower electrode layer becomes a common electrode formed commonly on the respective piezoelectric elements32and the other thereof becomes an individual electrode individually formed on each piezoelectric element32. When an electric field corresponding to potential difference between the lower electrode layer and the upper electrode layer is applied between the lower electrode layer and the upper electrode layer, the piezoelectric element32deforms to be flexural in a direction away from or close to the nozzle22. The piezoelectric elements32in the present embodiment are formed in two columns along the nozzle column direction corresponding to the pressure chambers30arranged in two columns in parallel along the nozzle column direction.

In addition, as illustrated inFIG. 2andFIG. 3, a wiring40connected to the individual electrode or the common electrode of the piezoelectric element32is formed on the vibration plate31. The wiring40extends to the non-driving region36of the vibration plate31and serves as a terminal to be connected to the bump electrode37(to be described below) in the non-driving region36. In other words, as illustrated inFIG. 2, an individual terminal41(a kind of terminal in the invention) connected to the individual electrode of the piezoelectric element32and a common terminal42(a kind of terminal in the invention) connected to the common electrode of the piezoelectric element32are formed in the non-driving region36on the upper surface (surface facing sealing plate33) of the vibration plate31. Specifically, in a direction orthogonal to the nozzle column direction, the individual terminals41are formed on the outside of the column of one piezoelectric element32and the outside of the column of the other piezoelectric element32and the common terminal42is formed between columns of both piezoelectric elements32. Since the individual terminal41is connected to the individual electrode of the piezoelectric element32, the individual terminal41is formed for each piezoelectric element32. In other words, a plurality of individual terminals41are formed along the nozzle column direction. On the other hand, since the common terminal42is connected to the common electrode of the piezoelectric element32, at least one common terminal42is formed. In the present embodiment, the common terminal42is connected to both the common electrode on the column of one piezoelectric element32and the common electrode on the column of the other piezoelectric element32.

As illustrated inFIG. 2andFIG. 3, the sealing plate33(corresponding to first substrate in the invention) is a substrate made of silicon which is placed with an interval from the vibration plate31in a state where a photosensitive adhesive43(corresponding to interposed member in the invention) having insulating properties is interposed between the vibration plate31and the sealing plate33. In this embodiment, a plurality of bump electrodes37which output a driving signal from the driving IC34to the piezoelectric element32side are formed on the lower surface (corresponding to second surface in the invention) which is a surface of the sealing plate33on the side of the pressure chamber forming substrate29. As illustrated inFIG. 2, the bump electrode37is formed at a position corresponding to one individual terminal41formed on the outside of one piezoelectric element32, a position corresponding to the other individual terminal41formed outside the other piezoelectric element32, a position corresponding to the common terminal42formed between the columns of the piezoelectric elements32, and the like. Each bump electrode37is connected to a corresponding individual terminal41or common terminal42, respectively. The sealing plate33and the pressure chamber forming substrate29are bonded in a state of being pressed in an approaching direction to each other so that the bump electrodes37, the individual terminals41corresponding thereto and the common terminal42are electrically connected in a reliable manner.

As illustrated inFIG. 3, the bump electrode37in the present embodiment is a so-called resin core bump which includes a protrusion portion38made of resin protruding from the lower surface of the sealing plate33and a conductive film39which covers a portion of a surface (specifically, surface opposite to surface which is in contact with lower surface of sealing plate33) of the protrusion portion38. The protrusion portion38is made of, for example, a resin having elasticity made of polyimide resin, phenol resin, epoxy resin, or the like and is formed as a protrusion along the nozzle column direction on the lower surface of the sealing plate33. In addition, as illustrated inFIG. 3, in the cross-section in the direction intersecting the nozzle column direction, the protrusion portion38has a lower surface formed in a circular arc shape. In other words, the protrusion portion38has a first resin surface57which extends along the lower surface of the sealing plate33and is in contact with the sealing plate33and a second resin surface58having a circular arc shape rising in a crossing direction with respect to a lower surface of the sealing plate33from both ends of the surface. In the cross section in a direction intersecting the nozzle column direction (that is, extending direction of conductive film39), the rising angle θ of the end portion of the second resin surface58having a circular arc shape, in other words, an inner angle θ at the intersection point between the first resin surface57and the second resin surface58is set to 90 degrees or less. In the present embodiment, the angle θ is set to 60 degrees to 80 degrees.

In addition, the conductive film39is formed by laminating a lower surface side protective film52(corresponding to second protective film in the invention) and a lower surface side metal film53in this order from the lower surface side of the sealing plate33. The lower surface side protective film52is made of, for example, titanium (Ti), nickel (Ni), chromium (Cr), tungsten (W), alloys thereof, laminated thereof, or the like, and has corrosion resistance and conductivity. In addition, the lower surface side metal film53is made of gold (Au) or the like. Therefore, the lower surface side protective film52functions not only as a protective film for protecting the through wiring45to be described below but also as an adhesive layer for increasing the adhesion of the lower surface side metal film53. In addition, the lower surface side protective film52can also function as a barrier layer for suppressing metal diffusion occurring between the lower surface side metal film53and the through wiring45. By suppressing metal diffusion, fluctuation in resistance value can be reduced and thus reliability can be improved. In the present embodiment, the film thickness of the lower surface side protective film52is thinner than that of the upper surface side protective film55to be described below and is formed to be, for example, 50 nm to 150 nm. In addition, the film thickness of the lower surface side metal film53is formed to be substantially the same as that of the upper surface side metal film56to be described below, and is formed to be, for example, 400 nm to 600 nm.

The two-layered conductive film39described above is formed at a position corresponding to the individual terminal41or the common terminal42on the surface of the protrusion portion38. Specifically, a plurality of conductive films39of the bump electrodes37electrically connected to the individual terminals41are formed along the nozzle column direction corresponding to the individual terminals41arranged in parallel along the nozzle column direction. In addition, at least one conductive film39electrically connected to the common terminal42is formed corresponding to the common terminal42. The protrusion portions38are connected to the individual terminal41or the common terminal42in a slightly collapsed state in the height direction with the conductive film39(lower surface side protective film52and lower surface side metal film53) interposed therebetween. In other words, the bump electrode37is connected to the individual terminal41or the common terminal42in a slightly collapsed state in the height direction.

In addition, as illustrated inFIG. 3, the conductive film39extends to position overlapping the through wiring45(corresponding to wiring in the invention) formed at a position different from the protrusion portion38on the lower surface of the sealing plate33along a direction intersecting the nozzle column direction. In other words, the conductive film39extends from a position overlapping the end portion on the lower surface side of the through wiring45to a position overlapping the protrusion portion38in a direction intersecting the nozzle column direction. An end portion on the lower surface side of the through wiring45is covered with the conductive film39(that is, lower surface side protective film52) and thus is electrically connected to the conductive film39. In the present embodiment, since the through wiring45formed on one side of the bump electrode37and the through wiring45formed on the other side of the bump electrode37are disposed alternately along the nozzle column direction, the conductive film39taken out from the position overlapping the protrusion portion38to one side and the conductive film39taken out from the position overlapping the protrusion portion38to the other side or the position overlapping with the protrusion portion38are disposed alternately along the nozzle column direction.

As illustrated inFIG. 2andFIG. 3, the through wiring45is a wiring relaying between the lower surface and the upper surface of the sealing plate33, that is, a wiring extending from the lower surface side to the upper surface side of the sealing plate33and is made of a metal (conductor) such as copper (Cu) formed in an inside portion of the through hole49passing through the sealing plate33in the plate thickness direction. The through hole49in this embodiment is formed at a position corresponding to a sealing space44(to be described below) formed between the pressure chamber forming substrate29and the sealing plate33. In other words, the through wiring45is disposed so that the end (end portion) on the lower surface side thereof faces the inside of the sealing space44. As described above, the portion (that is, end on lower surface side of through wiring45) of the through wiring45exposed at the opening portion on the lower surface side of the through hole49is covered by the corresponding conductive film39. On the other hand, the portion (that is, end (end portion) on the upper surface side of the through wiring45) of the through wiring45exposed at the opening portion on the upper surface side of the through hole49is covered by the corresponding upper surface side wiring46. The conductive film39extending from the bump electrode37and the upper surface side wiring46are electrically connected by the through wiring45. The through wiring45need not be filled in the through hole49, and it is sufficient if at least a portion of the through hole49extends from the upper surface of the sealing plate33to the lower surface of the sealing plate33.

The upper surface side wiring46is a wiring which is laminated on the upper surface (corresponding to first surface in the invention) which is a surface of the sealing plate33on the driving IC34side (side opposite to pressure chamber forming substrate29side). The upper surface side wiring46is formed by laminating an upper surface side protective film55(corresponding to first protective film in the invention) and an upper surface side metal film56in this order from the upper surface side of the sealing plate33. The upper surface side protective film55is made of the same metal as that of the lower surface side protective film52and is made of, for example, titanium (Ti), nickel (Ni), chromium (Cr), tungsten (W), alloys thereof, laminated thereof, and the like. Therefore, like the lower surface side protective film52, the upper surface side protective film55also has corrosion resistance and conductivity. In addition, the upper surface side metal film56is made of the same metal as the lower surface side metal film53and is made of gold (Au) or the like. Like the lower surface side metal film53, the upper surface side protective film55functions not only as a protective film for protecting the through wiring45but also as an adhesive layer for increasing the adhesion of the upper surface side metal film56. In addition, the upper surface side protective film55can also function as a barrier layer for suppressing metal diffusion occurring between the upper surface side metal film56and the through wiring45. By suppressing metal diffusion, fluctuation in resistance value can be reduced and reliability can be improved. The film thickness of the upper surface side protective film55in the present embodiment is larger than the film thickness of the lower surface side protective film52, and is formed to be, for example, 250 nm to 350 nm. In addition, as described above, the film thickness of the upper surface side metal film56is formed to be substantially the same as the film thickness of the lower surface side metal film53, and is formed to be, for example, 400 nm to 600 nm. The upper surface side wiring46extends from a position covering the end portion on the upper surface side of the through wiring45to a position corresponding to the IC terminal47of the driving IC34to be described below and becomes a terminal portion connected to the IC terminal47at that position.

The photosensitive adhesive43for adhering the sealing plate33and the pressure chamber forming substrate29(more specifically, vibration plate31laminated on pressure chamber forming substrate29) to each other is an adhesive that has photosensitivity in which the degree of curing changes by light irradiation and a thermosetting property in which degree of curing changes by heating. As the photosensitive adhesive43described above, for example, a resin including an epoxy resin, an acrylic resin, a phenol resin, a polyimide resin, a silicone resin, a styrene resin or the like as a main component is suitably used. In addition, as illustrated inFIG. 2, the photosensitive adhesive43in the present embodiment is provided on the outer peripheral portion of the sealing plate33and on both sides of the bump electrode37in the direction orthogonal to the nozzle column direction. A sealing space44(a kind of space in the invention) is formed between the sealing plate33and the pressure chamber forming substrate29by the photosensitive adhesive43provided on the outer peripheral portion of the sealing plate33. In other words, the sealing space44is defined by the photosensitive adhesive43provided on the sealing plate33, the pressure chamber forming substrate29(vibration plate31), and the outer peripheral portion of the sealing plate33. Therefore, the piezoelectric element32is accommodated in the sealing space44. Since the sealing space44is open to the atmosphere via an atmospheric release path (not illustrated) having a small diameter passing through the sealing plate33, the sealing space is not a completely sealing space. In addition, the photosensitive adhesive43provided on both sides of the bump electrode37is formed to be long along the extending direction of the protrusion portion38, respectively.

The driving IC34is laminated on the upper surface of the sealing plate33. The driving IC34is an IC chip for driving the piezoelectric element32, and is fixed to the upper surface of the sealing plate33via an adhesive48such as an anisotropic conductive film (ACF). As illustrated inFIG. 2, a plurality of IC terminals47connected to terminal portions of the upper surface side wiring46are formed on the lower surface (surface on sealing plate33side) of the driving IC34. A plurality of IC terminals47corresponding to the individual terminals41of the IC terminals47is arranged in parallel along the nozzle column direction. In the present embodiment, two columns of IC terminals47are formed corresponding to the columns of piezoelectric elements32arranged in two columns in parallel.

The recording head3having the configuration described above introduces the ink from the ink cartridge7into the pressure chamber30via the liquid introduction path18, the common liquid chamber25, the individual communication path26, and the like. In this state, when a drive signal from the driving IC34is supplied to the piezoelectric element32via the bump electrode37or the like, the piezoelectric element32is driven to cause pressure variation in the ink in the pressure chamber30. By using this pressure fluctuation, the recording head3ejects ink droplets from the nozzles22.

Next, the method for manufacturing a recording head3, particularly a method for manufacturing a sealing plate33, will be described in detail.FIG. 4toFIG. 7are state transition diagrams for illustrating the method for manufacturing a sealing plate33. First, as illustrated inFIG. 4, a through hole49passing through the sealing plate33in the thickness direction is formed at a predetermined position of a silicon substrate (hereinafter, simply referred to as sealing plate33) which becomes the sealing plate33. The a through hole49described above is formed by, for example, dry etching, wet etching, laser, a method combining these methods, or the like. Once the through hole49is formed in the sealing plate33, the through wiring45is formed in the inside portion of the through hole49by an electrolytic plating method or the like. Specifically, for example, a seed layer is formed in the inside portion of the through hole49by a sputtering method or the like, and metal is grown on the seed layer by the electrolytic plating method, and the inside of the through hole49is filled with metal. The metal precipitated outside the upper surface or the lower surface of the sealing plate33is removed by a chemical mechanical polishing (CMP) method or the like. Accordingly, the through wiring45is formed as illustrated inFIG. 5.

Next, a bump electrode37is formed on the lower surface of the sealing plate33. Specifically, for example, a resin layer is formed on the surface of the sealing plate33, and a resin layer is formed at a predetermined position via a photolithography process or the like. In other words, a resin layer having a rectangular-shaped cross section and extending along the nozzle column direction is formed. Once the resin layer described above is formed, the sealing plate33is heated. The viscosity of the resin layer is decreased by the heating and the corner is formed. Thereafter, the resin layer is solidified by the sealing plate33being cooled. As a result, as illustrated inFIG. 6, a protrusion portion38having a circular arc surface is formed. Next, a conductive film39is formed on the protrusion portion38. Specifically, first, a metal layer which becomes the lower surface side protective film52is formed on the entire lower surface of the sealing plate33to a thickness of, for example, 50 nm to 150 nm, and the metal layer which becomes the lower surface side metal film53is formed thereon to a thickness of, for example, 400 nm to 600 nm. Thereafter, a resist layer is formed on the metal layer which becomes the lower surface side metal film53, and a metal layer which becomes the lower surface side protective film52and a metal layer which becomes the lower surface side metal film53are etched via a photolithography process, an etching process, or the like. Accordingly, as illustrated inFIG. 6, the conductive film39(lower surface side protective film52and lower surface side metal film53) is formed at a predetermined position, and the bump electrode37is formed.

Finally, the upper surface side wiring46and the like are formed on the upper surface of the sealing plate33. Specifically, a metal layer which becomes the upper surface side protective film55is formed on the entire upper surface of the sealing plate33to a thickness of, for example, 250 nm to 350 nm, and a metal layer which becomes the upper surface side metal film56is formed thereon to a thickness of, for example, 400 nm to 600 nm. Thereafter, a resist layer is formed on the metal layer which becomes the upper surface side metal film56, and a metal layer which becomes the upper surface side protective film55and a metal layer which becomes the upper surface side metal film56are etched via a photolithography process, an etching process, or the like. Accordingly, as illustrated inFIG. 7, the upper surface side wiring46(upper surface side protective film55and upper surface side metal film56) is formed at a predetermined position, and the sealing plate33is created. The method for manufacturing the sealing plate33is not limited to the above method. For example, first, the upper surface side wiring46and the like may be formed on the upper surface of the sealing plate33and the bump electrodes37and the like may be formed on the lower surface of the sealing plate33later.

Once the sealing plate33is formed, the photosensitive adhesive43before curing is interposed between the pressure chamber forming substrate29and the sealing plate33and then the pressure chamber forming substrate29on which the vibration plate31and the like are formed and the sealing plate33, are pressed (pressurized) in the approaching direction to each other. In this state, by heating, the photosensitive adhesive43is cured to bond the pressure chamber forming substrate29and the sealing plate33to each other. Thereafter, the driving IC34is bonded to the sealing plate33and then the actuator unit14is created. After the actuator unit14and the flow path unit15are bonded to each other, the flow path unit15to which the actuator unit14is bonded is bonded to the lower surface of the head case16. Accordingly, the actuator unit14is accommodated in the accommodation space17, and thus the recording head3described above is created.

In this manner, since the film thickness of the lower surface side protective film52is made relatively thin, the film forming time of the metal layer which becomes the lower surface side protective film52can be shorten. In other words, the time for forming the lower surface side protective film52can be shortened and the productivity of the recording head3, eventually the printer1, can be improved. In addition, since the thickness of the lower surface side protective film52is decreased, the cost for forming the lower surface side protective film52can be suppressed and the manufacturing cost of the recording head3, eventually the printer1, can be suppressed. In this manner, even if the thickness of the lower surface side protective film52is decreased, since the end portion on the lower surface side of the through wiring45faces the sealing space44, corrosion of the end portion on the lower surface side of the through wiring45can be suppressed. In other words, since the end portion on the lower surface side of the through wiring45is sealed in the sealing space44and is spaced apart from the environment outside the actuator unit14, the end portion on the lower surface side of the through wiring45is unlikely to be corroded. In addition, in the present embodiment, since the end portion on the lower surface side of the through wiring45is covered with the lower surface side protective film52, as compared with a case where the end portion on the lower surface side of the through wiring45is not covered with a protective film, corrosion resistance of the through wiring45can be improved. On the other hand, since the end portion on the upper surface side of the through wiring45is covered with the upper surface side protective film55having a relatively large film thickness, the end portion on the upper surface side of the through wiring45is unlikely to be corroded. As a result, the reliability of the recording head3can be improved.

Further, since the lower surface side protective film52extends from a position covering the end portion on the lower surface side of the through wiring45to the position overlapping the protrusion portion38, the lower surface side protective film52can function as a portion of an electrode (bump electrode) which is connected to the individual terminal41or the common terminal42. Since the film thickness of the lower surface side protective film52is formed to be thinner than that of the upper surface side protective film55, when being electrically connected by pressing the bump electrode37against the terminal, cracking and fracturing is unlikely to be generated in the lower surface side protective film52. As a result, the reliability of the connection between the lower surface side protective film52which becomes the bump electrode37and the individual terminal41or the common terminal42can be improved. Further, in the extending direction of the lower surface side protective film52, since the inner angle θ at the intersection point between the first resin surface57of the protrusion portion38extending along the lower surface of the sealing plate33and the second resin surface58of the protrusion portion38extending in the direction intersecting the lower surface of the sealing plate33is set to 90 degrees or less, the lower surface side protective film52extending from the lower surface of the sealing plate33to a position overlapping the protrusion portion38can be prevented from being disconnected at a boundary between the lower surface of the sealing plate33and the protrusion portion38. In particular, in the present embodiment, since the inner angle θ described above is set to 60 degrees to 80 degrees, even when the film thickness of the lower surface side protective film52is made relatively thin, disconnection of the lower surface side protective film52can be further suppressed.

By the way, in the embodiment described above, although the end portion on the lower surface side of the through wiring45is covered with the lower surface side protective film52, it is not limited thereto. For example, in the second embodiment illustrated inFIG. 8, the lower surface side protective film52is not formed on the lower surface of the sealing plate33. In other words, as illustrated inFIG. 8, the conductive film39includes only the lower surface side metal film53. In this manner, by eliminating the lower surface side protective film, a process of forming the lower surface side protective film is not required and thus it is possible to further improve the productivity of the recording head3. In addition, the manufacturing cost of the recording head3can be further suppressed. Further, there are no problems such as cracking and fracturing of the lower surface side protective film when electrically connecting by pressing the bump electrode37against the terminal. As a result, the reliability of the connection between the bump electrode37and the individual terminal41or the common terminal42can be further improved. In this manner, even when the lower surface side protective film is eliminated, since the end portion on the lower surface side of the through wiring45faces the sealing space44, corrosion of the end portion on the lower surface side of the through wiring45can be suppressed. Since the other configuration, that is, the configuration except that the lower surface side protective film is not provided and the conductive film39is made one layer is the same as the first embodiment described above, the description thereof is omitted.

In addition, in the above description, as an explanation of the configuration of the bump electrode37, or the like, although the bump electrode37connected to one individual terminal41of the plurality of bump electrodes37mainly described, since the configuration of other bump electrodes37(the other bump electrode37connected to the individual terminal41, since the bump electrode37connected to the common terminal42and the like) or the like are substantially the same as the bump electrode37connected to one the individual terminals41, the description is omitted. Further, each embodiment described above, although the photosensitive adhesive43is described as a interposed member which defines the sealing space44between the sealing plate33and the pressure chamber forming substrate29, as an example, it is not limited thereto. The interposed member may be of any type as long as it can define the sealing space between the sealing plate and the pressure chamber forming substrate. For example, a hollow member (substrate) in which the upper surface is bonded to the sealing plate and the lower surface is bonded to the pressure chamber forming substrate may be used between the sealing plate and the pressure chamber forming substrate.

In the above embodiment, although the ink jet type recording head3is described as an example of the liquid ejecting head, the invention can be also applied to other liquid ejecting heads. The invention can be applied to a color material ejecting head which is used for manufacturing a color filter of a liquid crystal display or the like, an electrode material ejecting head which is used for forming an electrode of an organic Electro Luminescence (EL) display, a face emitting display (FED), or the like, a bioorganic ejecting head which is used for manufacturing a biochip (biochemical element), or the like, for example. A solution of each color material of red (R), green (G), and blue (B) is ejected as a kind of liquid from a color material ejecting head for the display manufacturing apparatus. In addition, a liquid electrode material is injected as a kind of liquid from the electrode material ejecting head for an electrode forming apparatus, and a solution of bioorganic matter is ejected as a kind of liquid from the bioorganic ejecting head for a chip manufacturing apparatus.

In addition, the invention can be applied to a MEMS device having a structure in which a first substrate and a second substrate are bonded to each other with interval there between. For example, the invention can be also applied to a MEMS device including a driving region and a piezoelectric element on any one of a first substrate and a second substrate, and applying the piezoelectric element to a sensor or the like for detecting pressure change, vibration, displacement, or the like of a driving region.

The entire disclosure of Japanese Patent Application No. 2016-183925, filed Sep. 21, 2016 is expressly incorporated by reference herein.