Patent Publication Number: US-2023158547-A1

Title: Electronic Device

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-189196, filed Nov. 22, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an electronic device. 
     2. Related Art 
     In the past, there has been known an electronic device having piezoelectric elements arranged in a matrix. For example, an electronic device provided with a sealing plate having an opening, a vibrating plate for closing the opening, and a piezoelectric element which is installed on the vibrating plate, and in which a piezoelectric body is sandwiched by an upper electrode and a lower electrode is disclosed in JP-A-2021-106183 (Document 1). 
     According to Document 1, the vibrating plate and the sealing plate are arranged to be opposed to each other. The sealing plate limits a range in which the vibrating plate vibrates. A frequency with which the vibrating plate vibrates is set by a size of the vibrating plate surrounded by the opening of the sealing plate. As a material of the sealing plate, there is used a material difficult to absorb the vibration of the vibrating plate. 
     The sealing plate is provided with a pair of through electrodes. The upper electrode and the lower electrode are electrically coupled to the through electrodes, respectively. The sealing plate is arranged so as to be opposed to a wiring board. The wiring board is provided with pads. The through electrodes protrude toward the wiring board. The pads and the through electrodes have electrical contact with each other, respectively. The upper electrode and the lower electrode are electrically coupled to the pads via the through electrodes, respectively. 
     The through electrodes are each formed of a resin adhesive including filler metal. When forming the through electrodes, the liquid resin adhesive including the filler metal is poured into through holes. The liquid resin adhesive is dried by heating, and is thus solidified. On this occasion, a solvent included in the liquid resin adhesive evaporates. In the process in which the resin adhesive is solidified, a volume of the resin adhesive decreases. 
     In the electronic device in Document 1, there is a possibility that the through holes of the sealing plate contract to generate a crack in the vibrating plate when the through electrodes contract in a manufacturing process of the through electrodes. 
     SUMMARY 
     An electronic device includes a first substrate provided with an element, and including a first face on which a first electrode to be coupled to the element is disposed, and a second substrate which has a second face and a third face, and which is disposed so that the second face is opposed to the first face, wherein the second substrate has a through hole at a position corresponding to the first electrode, the through hole penetrating from the second face to the third face, the through hole is provided with a through electrode electrically coupled to the first electrode, and a void is disposed in a part of the through electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic exploded perspective view showing a configuration of an electronic device according to a first embodiment. 
         FIG.  2    is a schematic sectional side view showing a configuration of the electronic device. 
         FIG.  3    is a schematic sectional side view showing the configuration of the electronic device. 
         FIG.  4    is a schematic plan view showing a configuration of a first substrate. 
         FIG.  5    is a schematic sectional side view showing a configuration of a through electrode. 
         FIG.  6    is a schematic sectional side view for explaining a method of manufacturing the through electrode. 
         FIG.  7    is a schematic sectional side view for explaining the method of manufacturing the through electrode. 
         FIG.  8    is a schematic sectional side view for explaining the method of manufacturing the through electrode. 
         FIG.  9    is a schematic sectional side view for explaining the method of manufacturing the through electrode. 
         FIG.  10    is a schematic sectional side view for explaining the method of manufacturing the through electrode. 
         FIG.  11    is a schematic sectional side view for explaining the method of manufacturing the through electrode. 
         FIG.  12    is a schematic sectional side view for explaining the method of manufacturing the through electrode. 
         FIG.  13    is a diagram for explaining a relationship between an area ratio of the through electrode to a through hole and an inter-terminal resistance. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     In the present embodiment, characteristic examples of an electronic device and an electronic device manufacturing method of manufacturing the electronic device will be described. 
     As shown in  FIG.  1   , in an electronic device  1 , a third substrate  2 , a second substrate  3 , a first substrate  4 , and a fourth substrate  5  are stacked in a Z direction in this order. In the Z direction, the fourth substrate  5  side is defined as a positive Z direction, and the third substrate  2  side is defined as a negative Z direction. A direction along the positive Z direction is defined as a first direction  6 . The first direction  6  is a stacking direction of the first substrate  4  and the second substrate  3 . 
     When viewed from the first direction  6 , the third substrate  2 , the second substrate  3 , the first substrate  4 , and the fourth substrate  5  each have a rectangular shape. The third substrate  2 , the second substrate  3 , the first substrate  4 , and the fourth substrate  5  are the same in longitudinal direction. The second substrate  3 , the first substrate  4 , and the fourth substrate  5  are the same in shape. The third substrate  2  is larger than the second substrate  3 , the first substrate  4 , and the fourth substrate  5 . 
     A longitudinal direction of the third substrate  2  is defined as an X direction. A short-side direction of the third substrate  2  is defined as a Y direction. The X direction, the Y direction, and the Z direction are perpendicular to each other. 
     The first substrate  4  includes a first face  4   a  facing to the second substrate  3 . On the first face  4   a , there are arranged elements  7  in a matrix. The elements  7  are each a piezoelectric element. According to this configuration, the elements  7  are the piezoelectric elements. By applying an AC voltage to the elements  7 , it is possible for the electronic device  1  to vibrate the first substrate  4  to emit an ultrasonic wave. The first substrate  4  is also referred to as a vibrating plate. 
     The number of the elements  7  is not particularly limited. In the present embodiment, for example, the elements  7  constitute a 4×4 matrix, and therefore, the number of the elements  7  is sixteen. 
     The fourth substrate  5  is provided with four fourth holes  8  elongated in the X direction. When viewed from the first direction  6 , the shape of the fourth hole  8  is a parallelogram. The fourth substrate  5  is formed of a silicon single-crystal substrate. The fourth holes  8  are formed using a wet-etching process. A side surface of the fourth hole  8  is a crystal face low in etching rate. Since in the silicon single-crystal substrate, the crystal face low in etching rate has a parallelogram shape, the shape of each of the fourth holes  8  is a parallelogram. The fourth holes  8  penetrate the fourth substrate  5 . The fourth holes  8  are arranged at places opposed to the arrangement of the elements  7 . It should be noted that the number of the fourth holes  8  is not limited to four. 
     The second substrate  3  has a second face  3   a  and a third face  3   b . The second face  3   a  is arranged so as to be opposed to the first face  4   a  of the first substrate  4 . The second substrate  3  is provided with four second grooves  9  elongated in the Y direction on the second face  3   a . When viewed from the first direction  6 , the shape of the second groove  9  is a parallelogram. The second substrate  3  is formed of a silicon single-crystal substrate. The second grooves  9  are formed using a wet-etching process. Therefore, the shape of the second groove  9  is a parallelogram. The second grooves  9  are arranged at places opposed to the arrangement of the elements  7 . 
     When viewed from the first direction  6 , the elements  7  are arranged at places where the fourth holes  8  and the second grooves  9  cross each other. Therefore, at the place where the element  7  is arranged, the first substrate  4  can vibrate in the positive Z direction and the negative Z direction. 
     The first substrate  4  and the fourth substrate  5  are integrated with each other. The material of the first substrate  4  is silicon oxide, and the first substrate  4  is formed by oxidizing the fourth substrate  5 . 
     The first substrate  4  is provided with a common terminal  11  as a first electrode and a drive terminal  12  as the first electrode on the first face  4   a . The common terminal  11  and the drive terminal  12  are electrically coupled to the elements  7 . 
     The second substrate  3  has a first through hole  13  as a through hole penetrating from the second face  3   a  to the third face  3   b  at a position corresponding to the common terminal  11 . The second substrate  3  has a second through hole  14  as a through hole penetrating from the second face  3   a  to the third face  3   b  at a position corresponding to the drive terminal  12 . 
     A size of the first through hole  13  is not particularly limited. In the present embodiment, for example, a length of a long side of the first through hole  13  is about 1 mm. A width in the X direction of the first through hole  13  is about 350 μm. A thickness of the second substrate  3  is about 400 μm. The second through hole  14  is the same in size as the first through hole  13 . 
     In the first through hole  13  of the second substrate  3 , there is disposed a first through electrode  15  as a through electrode at the negative Z direction side of the common terminal  11 . The first through electrode  15  is electrically coupled to the common terminal  11 . In the second through hole  14  of the second substrate  3 , there is disposed a second through electrode  16  as a through electrode at the negative Z direction side of the drive terminal  12 . The second through electrode  16  is electrically coupled to the drive terminal  12 . 
     The second substrate  3  is provided with an opening hole  17  at the positive X direction side of the second grooves  9 . The opening hole  17  penetrates from the second face  3   a  to the third face  3   b . The opening hole  17  and the second groove  9  are connected with a first communication groove  18 . The four second grooves  9  are connected to each other with second communication grooves  19 . 
     The second substrate  3  and the first substrate  4  are fixed with an adhesive. The second grooves  9  are connected to the opening hole  17 , the first communication groove  18  and the second communication grooves  19 , and are therefore not sealed. When the first substrate  4  vibrates, the air in the second grooves  9  is connected to the outside air, and therefore, inside pressure of the second grooves  9  is difficult to fluctuate. Therefore, the first substrate  4  is made easy to vibrate. 
     The third substrate  2  is arranged so as to be opposed to the third face  3   b  of the second substrate  3 . The third substrate  2  is provided with a common coupling terminal  21  as a second electrode at a place corresponding to the first through electrode  15 . The common coupling terminal  21  is electrically coupled to the first through electrode  15 . The third substrate  2  is provided with a drive coupling terminal  22  as the second electrode at a place corresponding to the second through electrode  16 . The drive coupling terminal  22  is electrically coupled to the second through electrode  16 . 
     According to this configuration, the common coupling terminal  21  is electrically coupled to the first through electrode  15 . The drive coupling terminal  22  is electrically coupled to the second through electrode  16 . Therefore, by supplying the common coupling terminal  21  and the drive coupling terminal  22  with electrical power, it is possible to supply the electrical power to the elements  7 . 
     The third substrate  2  is provided with an external common terminal  23  at the negative X direction side of the common coupling terminal  21 . The external common terminal  23  and the common coupling terminal  21  are electrically coupled to each other with an interconnection  24 . The third substrate  2  is provided with an external drive terminal  25  at the negative X direction side of the drive coupling terminal  22 . The external drive terminal  25  and the drive coupling terminal  22  are electrically coupled to each other with an interconnection  26 . 
     The interconnection  24  and the interconnection  26  are covered with a resist  27 . The common coupling terminal  21 , the drive coupling terminal  22 , the external common terminal  23 , and the external drive terminal  25  are not covered with the resist  27  but are exposed. The common coupling terminal  21  is electrically coupled to the first through electrode  15 . The drive coupling terminal  22  is electrically coupled to the second through electrode  16 . 
     On an end at the positive X direction side of the second substrate  3 , a corner at the positive Y direction side and a corner at the negative Y direction side are fixed by bonding to the third substrate  2  with fixing adhesives  28 . On an end at the negative X direction side of the second substrate  3 , the periphery of the first through electrode  15  and the second through electrode  16  is fixed by bonding to the third substrate  2  with the fixing adhesive  28 . 
       FIG.  2    is a cross-sectional view along a line A-A in  FIG.  1   .  FIG.  3    is a cross-sectional view along a line B-B in  FIG.  1   . As shown in  FIG.  2    and  FIG.  3   , when viewed from the first direction  6 , the elements  7  are arranged at the places where the fourth holes  8  and the second grooves  9  cross each other. The elements  7  are arranged on the first face  4   a  of the first substrate  4 . The element  7  is constituted by a drive electrode  7   a , a piezoelectric film  7   b , and a common electrode  7   c  arranged in the negative Z direction from the first face  4   a.    
     The piezoelectric film  7   b  is formed using, for example, transition metal oxide having a perovskite structure. Specifically, the piezoelectric film  7   b  is formed using lead zirconate titanate including Pb, Ti, and Zr. 
     The plurality of drive electrodes  7   a  is electrically coupled to a drive interconnection  29  extending in the X direction. The drive electrodes  7   a  and the drive interconnection  29  are the same in material as each other. The plurality of common electrodes  7   c  is electrically coupled to a common interconnection  31  extending in the Y direction. The common electrodes  7   c  and the common interconnection  31  are the same in material as each other. 
     The first substrate  4  and the element  7  constitute an ultrasonic transducer  32 . The common electrode  7   c  is kept at a predetermined reference potential. Further, by inputting a drive pulse signal into the drive electrode  7   a , the element  7  deforms, and thus, the first substrate  4  vibrates. Thus, the ultrasonic transducer  32  transmits an ultrasonic wave toward the positive Z direction. When an object exists at the positive Z direction side of the electronic device  1 , the ultrasonic wave is reflected by the object. When the reflected ultrasonic wave passes through the fourth hole  8  of the fourth substrate  5  to reach the ultrasonic transducer  32 , the first substrate  4  vibrates in accordance with sound pressure of the ultrasonic wave. The piezoelectric film  7   b  deforms due to the vibration of the first substrate  4 , and thus, a potential difference occurs between the drive electrode  7   a  and the common electrode  7   c . Thus, a reception signal corresponding to the sound pressure of the ultrasonic wave received is output from the drive electrode  7   a  of the ultrasonic transducer  32 . In other words, the ultrasonic wave is detected. 
     By measuring the time from when the electronic device  1  transmits the ultrasonic wave to when the electronic device  1  receives the ultrasonic wave, it is possible to measure a distance between the electronic device  1  and the object. 
       FIG.  4    is a diagram of the first substrate  4  viewed from the second substrate  3  side. As shown in  FIG.  4   , on the first face  4   a , there are arranged the four drive interconnections  29  extending in the X direction. The drive interconnections  29  are integrated with each other at the negative X direction side, and are electrically coupled to the drive terminal  12 . On the first face  4   a , there are arranged the four common interconnections  31  extending in the Y direction. The common interconnections  31  are integrated with each other at the negative Y direction side, and are electrically coupled to the common terminal  11 . 
       FIG.  5    is a cross-sectional view along a line C-C in  FIG.  1   . As shown in  FIG.  5   , the first through electrode  15  electrically couples the common terminal  11  and the common coupling terminal  21  to each other. The second through electrode  16  electrically couples the drive terminal  12  and the drive coupling terminal  22  to each other. 
     The third substrate  2  is arranged so as to be opposed to the third face  3   b  of the second substrate  3 . The third substrate  2  has the common coupling terminal  21  which is electrically coupled to the first through electrode  15 . The third substrate  2  has the drive coupling terminal  22  which is electrically coupled to the second through electrode  16 . 
     According to this configuration, the common coupling terminal  21  is electrically coupled to the first through electrode  15 . The drive coupling terminal  22  is electrically coupled to the second through electrode  16 . Therefore, by supplying the common coupling terminal  21  and the drive coupling terminal  22  with electrical power, it is possible to supply the electrical power to the elements  7 . 
     The first through electrode  15  and the second through electrode  16  are each formed of an electrically-conductive adhesive. Specifically, the first through electrode  15  and the second through electrode  16  are resin including silver filler. The resin is obtained by heating the resin adhesive to thereby solidify the resin adhesive. As the resin adhesive, there can be used, for example, an epoxy resin adhesive, an urethane resin adhesive, or a silicone resin adhesive. 
     In a formation process of the first through electrode  15 , the adhesive poured into the first through hole  13  is dried by heating. In a formation process of the second through electrode  16 , the adhesive poured into the second through hole  14  is dried by heating. The adhesives are solidified with contraction. 
     A void  33  is provided to a part of each of the first through electrode  15  and the second through electrode  16 . According to this configuration, even when the material of the first through electrode  15  and the second through electrode  16  contracts when forming the first through electrode  15  and the second through electrode  16 , the voids  33  expand. Therefore, since the stress of contracting the first through hole  13  and the second through hole  14  is reduced, the contraction of the first through hole  13  and the second through hole  14  is reduced. As a result, it is possible to reduce an occurrence of a crack in the first substrate  4 . 
     A proportion of a volume of the void  33  to a volume of the first through hole  13  is no lower than 1% and no higher than 50%. According to this configuration, since the proportion of the volume of the void  33  to the volume of the first through hole  13  is no lower than 1%, even when the material of the first through electrode  15  contracts when forming the first through electrode  15 , the contraction of the first through hole  13  is reduced. Since the proportion of the volume of the void  33  to the volume of the first through hole  13  is no higher than 50%, it is possible to make the electrical resistance of the first through electrode  15  low. Further, it is possible to prevent a conduction failure due to a broken line of the first through electrode  15 . 
     Similarly, a proportion of a volume of the void  33  to a volume of the second through hole  14  is no lower than 1% and no higher than 50%. Therefore, even when the material of the second through electrode  16  contracts, the contraction of the second through hole  14  is reduced. It is possible to make the electrical resistance of the second through electrode  16  low. Further, it is possible to prevent a conduction failure due to a broken line of the second through electrode  16 . 
     A length in the first direction  6  of the second through hole  14  is defined as a first through hole length  34 . A length in the first direction  6  of the void  33  in the second through hole  14  is defined as a first void length  35 . A ratio of the first void length  35  to the first through hole length  34  is no lower than 25% and no higher than 95%. 
     According to this configuration, since the ratio of the length in the first direction  6  of the void  33  to the length in the first direction  6  of the second through hole  14  is no lower than 25%, even when the material of the second through electrode  16  contracts when forming the second through electrode  16 , the contraction of the second through hole  14  is reduced. Since the ratio of the length in the first direction  6  of the void  33  to the length in the first direction  6  of the second through hole  14  is no higher than 95%, it is possible to make the electrical resistance of the second through electrode  16  low. Further, it is possible to prevent the conduction failure due to the broken line of the second through electrode  16 . 
     Similarly, a ratio of the length in the first direction  6  of the void  33  to the length in the first direction  6  of the first through hole  13  is no lower than 25% and no higher than 95%. Therefore, even when the material of the first through electrode  15  contracts, the contraction of the first through hole  13  is reduced. It is possible to make the electrical resistance of the first through electrode  15  low. Further, it is possible to prevent the conduction failure due to the broken line of the first through electrode  15 . 
     Out of directions perpendicular to the first direction  6 , a longitudinal direction of the first through hole  13  and the second through hole  14  is defined as a second direction  36 . The second direction  36  corresponds to the Y direction. A length in the second direction  36  of the second through hole  14  is defined as a second through hole length  37 . A length in the second direction  36  of the void  33  in the second through hole  14  is defined as a second void length  38 . A ratio of the second void length  38  to the second through hole length  37  is no lower than 10% and no higher than 60%. 
     According to this configuration, since the ratio of the length in the second direction  36  of the void  33  to the length in the second direction  36  of the second through hole  14  is no lower than 10%, even when the material of the second through electrode  16  contracts when forming the second through electrode  16 , the contraction of the second through hole  14  is reduced. Since the ratio of the length in the second direction  36  of the void  33  to the length in the second direction  36  of the second through hole  14  is no higher than 60%, it is possible to make the electrical resistance of the second through electrode  16  low. Further, it is possible to prevent the conduction failure due to the broken line of the second through electrode  16 . 
     Similarly, a ratio of the length in the second direction  36  of the void  33  to the length in the second direction  36  of the first through hole  13  is no lower than 10% and no higher than 60%. Therefore, even when the material of the first through electrode  15  contracts, the contraction of the first through hole  13  is reduced. It is possible to make the electrical resistance of the first through electrode  15  low. Further, it is possible to prevent the conduction failure due to the broken line of the first through electrode  15 . 
     Then, a method of manufacturing the first through electrode  15  and the second through electrode  16  will be described. As shown in  FIG.  6   , the second substrate  3 , the first substrate  4 , and the fourth substrate  5  are prepared. The first substrate  4  is formed by oxidizing one surface of the fourth substrate  5 . 
     The first substrate  4  is provided with the drive electrodes  7   a , the drive interconnections  29 , the piezoelectric films  7   b , the common electrodes  7   c , the common interconnections  31 , the common terminal  11 , and the drive terminal  12 . For the formation of these elements, there are used a deposition method such as a sputtering method, a photolithography method, a dry-etching process, and so on. For the formation of the fourth holes  8  of the fourth substrate  5 , there are used a photolithography method, a wet-etching process, and so on. For the formation of the second grooves  9 , the first through hole  13 , the second through hole  14 , the opening hole  17 , the first communication groove  18 , and the second communication groove  19  of the second substrate  3 , there are used a photolithography method, a wet-etching process, and so on. Then, the second substrate  3  is fixed to the first substrate  4  with an adhesive. 
     For the formation of the first through electrode  15  and the second through electrode  16 , there is used a stencil printing method. The stencil printing method is in the same category of a leakage printing method as a silk-screen method. A stencil  39  is arranged on the third face  3   b  of the second substrate  3  in an overlapping manner. The stencil  39  is provided with holes  39   a  the same in shape as the first through hole  13  and the second through hole  14 . It should be noted that the formation of the first through electrode  15  and the second through electrode  16  is not particularly limited. For example, it is possible to form the first through electrode  15  and the second through electrode  16  using a dispenser. On this occasion, it is possible to form the voids  33 . 
     A paste  41  is mounted on the stencil  39  at the negative Y direction side. The paste  41  is a paste-like resin adhesive including the silver filler. The paste  41  includes a solvent and has fluidity. The paste  41  is sandwiched by a squeegee  42  and the stencil  39 . The squeegee  42  is a plate long in the positive X direction. The positive Y direction is defined as a first sliding direction  43 . The squeegee  42  is slid in the first sliding direction  43  in the state in which the squeegee  42  at the negative Y direction side has contact with the stencil  39 . The paste  41  is pushed by the squeegee  42  to move in the first sliding direction  43 . 
     As shown in  FIG.  7   , when the squeegee  42  passes through the first through hole  13 , a part of the paste  41  passes through the hole  39   a  to enter the first through hole  13 . The part of the paste  41  moves to the common terminal  11  along a first wall  13   a  as a wall of the first through hole  13  at the positive Y direction side. The part of the paste  41  having reached the common terminal  11  moves in the negative Y direction along the common terminal  11 . The paste  41  moving in the negative Y direction along the common terminal  11  does not reach a second wall  13   b  as a wall of the first through hole  13  at the negative Y direction side. By adjusting the viscosity of the paste  41 , it is possible to prevent the paste  41  from reaching the second wall  13   b.    
     A wall at the positive Y direction side in the second through hole  14  is defined as a third wall  14   a . A wall at the negative Y direction side in the second through hole  14  is defined as a fourth wall  14   b . In the second through hole  14 , a part of the past  41  moves to the drive terminal  12  along the third wall  14   a . The part of the paste  41  having reached the drive terminal  12  moves in the negative Y direction along the drive terminal  12 . The paste  41  moving in the negative Y direction along the drive terminal  12  does not reach the fourth wall  14   b.    
     As shown in  FIG.  8   , as a result, the paste  41  is poured into the first through hole  13  and the second through hole  14 . The paste  41  is arranged so as to be deflected to the positive Y side of the first through hole  13  and the second through hole  14 . In each of the common terminal  11  and the drive terminal  12 , the paste  41  is also arranged so as to be deflected to the positive Y direction side. The paste  41  arranged in the first through hole  13  and the second through hole  14  by the squeegee  42  moving in the first sliding direction  43  is defined as first paste  41   a.    
     As shown in  FIG.  9   , the negative Y direction is defined as a second sliding direction  44 . The second sliding direction  44  is a reverse direction to the first sliding direction  43 . The squeegee  42  is slid in the second sliding direction  44  in the state in which the squeegee  42  at the positive Y direction side has contact with the stencil  39 . The paste  41  is pushed by the squeegee  42  to move in the second sliding direction  44 . 
     As shown in  FIG.  10   , when the squeegee  42  passes through the second through hole  14 , a part of the paste  41  passes through the hole  39   a  to enter the second through hole  14 . The paste  41  arranged in the second through hole  14  by the squeegee  42  moving in the second sliding direction  44  is defined as second paste  41   b . A part of the second paste  41   b  moves toward the drive terminal  12  along the fourth wall  14   b . Since the first paste  41   a  has already existed on the drive terminal  12 , the second paste  41   b  having reached the first paste  41   a  moves in the positive Y direction along the first paste  41   a . The second paste  41   b  moving toward the drive terminal  12  along the fourth wall  14   b  does not reach the drive terminal  12 . By adjusting the viscosity of the paste  41 , it is possible to prevent the second paste  41   b  from reaching the drive terminal  12 . 
     When the squeegee  42  passes through the first through hole  13 , a part of the paste  41  passes through the hole  39   a  to enter the first through hole  13 . The part of the paste  41  moves toward the common terminal  11  along the second wall  13   b . Since the first paste  41   a  has already existed on the common terminal  11 , the paste  41  having reached the first paste  41   a  moves in the positive Y direction along the first paste  41   a . The paste  41  moving toward the common terminal  11  along the second wall  13   b  does not reach the common terminal  11 . 
     As shown in  FIG.  11   , the paste  41  is poured into the first through hole  13  and the second through hole  14 . In the first through hole  13 , the void  33  is formed at a place where the second wall  13   b  and the common terminal  11  cross each other. In the second through hole  14 , the void  33  is formed at a place where the fourth wall  14   b  and the drive terminal  12  cross each other. The void  33  is provided to a part of the paste  41  to form each of the first through electrode  15  and the second through electrode  16 . The voids  33  are each an enclosed space. The voids are filled with air. The air in the voids  33  is made unachievable to move outside the first through hole  13  and the second through hole  14 . 
     It should be noted that in the present embodiment, the first sliding direction  43  is the positive Y direction, and the second sliding direction  44  is the negative Y direction. In this case, the void  33  is formed at the negative Y direction side of each of the first through hole  13  and the second through hole  14 . The first sliding direction  43  can be the negative Y direction, and the second sliding direction  44  can be the positive Y direction. In this case, in the first through hole  13 , the void  33  is formed at a place where the first wall  13   a  and the common terminal  11  cross each other. In the second through hole  14 , the void  33  is formed at a place where the third wall  14   a  and the drive terminal  12  cross each other. 
     As shown in  FIG.  12   , the stencil  39  is removed from the second substrate  3 . The paste  41  in the first through hole  13  and the second through hole  14  is dried by heating. As a result, in the first through hole  13 , the paste  41  is solidified to form the first through electrode  15 . In the second through hole  14 , the paste  41  is solidified to form the second through electrode  16 . The void  33  is provided to a part of each of the first through electrode  15  and the second through electrode  16 . On this occasion, since the solvent included in the paste  41  evaporates, the paste  41  contracts. The volume of each of the first through electrode  15  and the second through electrode  16  becomes smaller than the volume of the paste  41 . 
     Even when the paste  41  contracts when the first through electrode  15  and the second through electrode  16  are formed, the voids  33  expand. Therefore, since the stress of contracting the first through hole  13  and the second through hole  14  is reduced, the contraction of the first through hole  13  and the second through hole  14  is reduced. 
     According to this configuration, the paste  41  as the resin paste including the silver filler is poured into the first through hole  13  and the second through hole  14 . By the solvent of the paste  41  evaporating, it is possible to provide the void  33  to a part of each of the first through electrode  15  and the second through electrode  16 . In particular, by pouring the paste  41  into the first through hole  13  and the second through hole  14  in a plurality of times, it is possible to provide the void  33  to the part of each of the first through electrode  15  and the second through electrode  16 . 
     In  FIG.  13   , the area ratio in the horizontal axis represents a ratio of the area of the first through electrode  15  to the area of the first through hole  13  when viewed from the first direction  6 . The inter-terminal resistance in the vertical axis represents the electrical resistance between the common terminal  11  and the common coupling terminal  21 . 
     As long as the inter-terminal resistance is no higher than 1 ohm, the first through electrode  15  can properly be used. On this occasion, the ratio in area of the first through electrode  15  is equal to or higher than 3%. 
     When the proportion of the volume of the void  33  to the volume of the first through hole  13  is equal to or lower than 50%, since the ratio of the area of the first through electrode  15  to the area of the first through hole  13  is higher than 3%, the inter-terminal resistance between the common terminal  11  and the common coupling terminal  21  is no higher than 1 ohm. Therefore, the first through electrode  15  can properly be used. 
     When the ratio of the length in the second direction  36  of the void  33  to the length in the second direction  36  of the first through hole  13  is equal to or lower than 60%, since the ratio of the area of the first through electrode  15  to the area of the first through hole  13  is higher than 3%, the inter-terminal resistance between the common terminal  11  and the common coupling terminal  21  is no higher than 1 ohm. Therefore, the first through electrode  15  can properly be used. 
     Second Embodiment 
     In the first embodiment described above, the elements  7  are the piezoelectric elements. Besides the above, the elements  7  can be pressure detection elements or inertia detection elements. In this case, it is possible to adopt a structure in which the through electrode includes the void  33 . It is possible to prevent the failure when the through electrode contracts.