JP4973641B2 - Wiring structure manufacturing method and circuit body - Google Patents

Description

  The present invention relates to a method for manufacturing a wiring structure and a circuit body.

  The inkjet head includes a flow path unit provided with a plurality of pressure chambers respectively corresponding to a plurality of nozzles that eject ink, and a piezoelectric actuator superimposed on the flow path unit so as to apply a transfer pressure to the ink in the pressure chamber. There is something to prepare. A plurality of electrode terminals corresponding to each pressure chamber are formed on the surface of the piezoelectric actuator, and electrode lands of an FPC (Flexible Printed Circuit) for supplying a drive signal are electrically connected to the electrode terminals. It is connected to the.

Specifically, a conductive material such as solder is formed in a bump shape on the electrode terminal of the piezoelectric actuator, and an uncured thermosetting resin layer is formed on the surface facing the piezoelectric actuator of the FPC so as to cover the electrode land. Apply and press the bump against the uncured thermosetting resin layer to penetrate the synthetic resin layer, bring the bump and electrode land into contact and cover the periphery of the bump with the thermosetting resin, then the thermosetting resin The layer is cured. That is, the electrode land is in contact with the tip of the bump for electrical connection, and the thermosetting resin layer is mechanically connected to the electrode terminal of the piezoelectric actuator around the bump. Thereby, FPC and a piezoelectric actuator are electrically and mechanically connected (for example, refer patent document 1).
JP 2005-305847 A

  However, in the assembly process after the FPC is connected to the piezoelectric actuator, if an external force acts on the FPC, the FPC is peeled off from the piezoelectric actuator, and electrical conduction is performed only by contact between the bump and the electrode land. Therefore, there is a possibility that electrical disconnection easily occurs due to peeling of the FPC.

  Therefore, an object of the present invention is to further improve electrical connection reliability while simplifying the connection.

  This invention is made | formed in view of the said situation, and the manufacturing method of the wiring structure which concerns on this invention is electrically connected to the member in which the several electrode terminal was formed in the surface, and the said several electrode terminal. A wiring structure including a circuit body, wherein the circuit body includes a substrate having reversible thermal expansion and contraction, and corresponds to the electrode terminal on a surface opposite to the member of the substrate. Forming a plurality of conductive wires having electrode lands at positions to be applied, and having a thermal expansion coefficient smaller than that of the base material so as to cover at least the conductive wires on the surface of the base material opposite to the member, and its thermal expansion and contraction Forming a covering layer having reversibility, forming a through hole that opens to the member side at the location of the electrode land on the substrate, and forming the electrode land on a surface that defines the through hole While conducting with A step of forming a conductor, a step of forming a plurality of conductive and flexible bumps electrically connected to the plurality of electrode terminals on the surface of the member, and heating the circuit body. Expanding the diameter of the through hole toward the member, and reducing the diameter of the through hole by releasing the heating in the state where the bump is inserted into the expanded through hole; It is characterized by having.

  According to this, since the thermal expansion coefficient of the coating layer is smaller than the thermal expansion coefficient of the base material, when the circuit body is heated, the circuit body is deformed so that the diameter of the through hole increases toward the member side. Then, it becomes easy to insert the bump into the through hole. When the heating is released in a state where the bump is inserted into the through hole, the thermal expansion and contraction of the base material and the coating layer has reversibility, so that the through hole contracts to return to the original state. Then, the relay conductor formed on the surface defining the through hole sandwiches the bump, and the relay conductor is in stable contact with the bump. Therefore, the circuit body can be easily connected to a member having a plurality of electrode terminals, and electrical and mechanical connection reliability can be improved.

  The substrate may have a thermal expansion property, and the coating layer may have a heat shrinkability.

  According to this, the difference in the coefficient of thermal expansion between the base material and the coating layer becomes large, and the circuit body significantly warps toward the coating layer side at the portion in the through hole. Can be expanded sufficiently.

  Forming a synthetic resin layer having an opening communicating with the through-hole at least around the through-hole on the member-side surface of the base material; and so as to surround the bump so that the synthetic resin layer surrounds the bump And a step of curing in contact with the surface.

  According to this, the synthetic resin layer around the through hole comes into contact with the surface of the member and hardens, and the circuit body is mechanically bonded to the member using the synthetic resin layer as an adhesive. Therefore, the peeling strength with respect to the member of a circuit body further improves. Further, since the synthetic resin layer has an opening communicating with the through hole, the synthetic resin can be prevented from being sandwiched between the bump and the electrode land. Furthermore, since the synthetic resin layer is cured so as to surround the bumps, the bumps are sealed and migration can be suitably prevented.

  The synthetic resin layer is made of a thermoplastic resin layer, and the step of curing the synthetic resin layer may be a step of releasing the heating.

  According to this, the synthetic resin layer can be cured at the same time as the heating is released to reduce the diameter of the through hole, and the number of work steps can be suppressed.

  The member is an actuator in which an active portion that deforms in response to a signal supplied to the electrode terminal is disposed between the plurality of electrode terminals, and the synthetic resin layer is spaced at a position corresponding to the active portion. It may be partially formed so as to open, and may be cured in contact with the surface of the electrode terminal so as to surround the bump.

  According to this, even when the circuit body is deformed by heating and approaches the active part, the synthetic resin layer is prevented from adhering to the active part, and the occurrence of a malfunction of the actuator can be prevented. In addition, since the synthetic resin layer is in contact with the surface of the electrode terminal, it does not affect the deformation of the active part, and it is possible to more suitably prevent the occurrence of the malfunction of the actuator.

  A cut portion may be formed around the through hole in the surface of the base member on the member side.

  According to this, in a heating process, it becomes easy to expand a diameter of a through-hole toward a member side from a notch part. Further, when a synthetic resin layer is formed on the member side surface of the base material, the synthetic resin that has entered the inside of the cut portion is pushed out from the cut portion when the through hole is expanded, and the synthetic resin layer is It becomes easy to contact the member around the through hole.

  A second electrode land that is electrically connected to the relay conductor may be formed around the through hole on the surface of the base member on the member side.

  According to this, since the bump also contacts the second electrode land and the electrical connection area of the bump with respect to the circuit body is increased, the electrical connection reliability is further improved.

  The coating layer may be partially formed so as to be spaced at positions between the plurality of electrode lands.

  According to this, in a heating process, the stress which arises by the difference in the thermal expansion coefficient of a base material and a coating layer works effectively with respect to a through hole, and can increase the diameter of a through hole smoothly.

  The member is an actuator in which an active portion that deforms in response to a signal supplied to the electrode terminal is disposed between the plurality of electrode terminals, and the surface of the circuit body on the coating layer side has the electrode land And the surface of the circuit body may be pressed by a heater having a flat heating surface in the heating step.

  According to this, since the heating surface of the heater preferentially contacts the portion corresponding to the electrode land in the circuit body, the heat and the pressing force applied by the heater concentrate on the portion corresponding to the electrode land, and the through hole is formed. Ensuring the expansion of the diameter and the contact of the bump to the relay conductor, and further, the heat and pressing force acting on the portion of the circuit body corresponding to the active portion of the actuator are alleviated to prevent the circuit body from contacting the active portion. be able to.

  The circuit body of the present invention includes a base material, a plurality of conductive wires formed on one surface of the base material and having electrode lands, and a coating layer formed so as to cover at least the conductive wires on one surface of the base material. The base material is formed with a through hole that opens to the other surface side of the base material at a location where the electrode land is disposed, and the surface that defines the through hole includes the electrode land and A conductive relay conductor is formed, the base material and the coating layer have reversible thermal expansion and contraction, and the thermal expansion coefficient of the coating layer is smaller than the thermal expansion coefficient of the base material. To do.

  According to this, since the thermal expansion coefficient of the coating layer is smaller than the thermal expansion coefficient of the base material, when the circuit body is heated, the circuit body is deformed so that the diameter of the through hole expands toward the hand member. If it does so, it will become easy to insert the electrical connection part (for example, bump) of an other party member into a through hole. When the heating is released in the inserted state, the heat shrinkage of the base material and the coating layer has reversibility, so that the through hole shrinks so as to return to the original state. Then, the relay conductor sandwiches the bump, and the relay conductor is in stable contact with the bump. Therefore, it is possible to easily connect to the mating member, and electrical connection reliability is improved.

  The substrate may have a thermal expansion property, and the coating layer may have a heat shrinkability.

  According to this, the difference in the coefficient of thermal expansion between the base material and the coating layer becomes large, and the circuit body significantly warps toward the coating layer side at the portion in the through hole. Can be expanded sufficiently.

  A synthetic resin layer having an opening communicating with the through hole may be further provided at least around the through hole on the other surface of the substrate.

  According to this, by heating the circuit body, the synthetic resin layer around the through hole comes into contact with the surface of the connection partner member and hardens, and the circuit body is mechanically bonded to the counterpart member using the synthetic resin layer as an adhesive. Is done. Accordingly, the peel strength of the circuit body with respect to the mating member is further improved.

  On the other surface of the base material, a cut portion may be formed around the through hole.

  According to this, if a circuit body is heated, it will become easy to expand a through-hole toward a member side from a notch part as a base point. In addition, when a synthetic resin layer is formed on the other surface of the substrate, the synthetic resin that has entered the inside of the notch is pushed out from the notch when the through hole is expanded, and the synthetic resin layer is It becomes easy to contact the surface of the mating member around.

  A second electrode land that is electrically connected to the relay conductor may be formed around the through hole on the other surface of the base material.

  According to this, since the electrical connection portion of the mating member also contacts the second electrode land, and the electrical connection area of the mating member with respect to the circuit body increases, the electrical connection reliability is further improved.

  The coating layer may be partially formed so as to be spaced at positions between the plurality of electrode lands.

  According to this, when the circuit body is heated, the stress caused by the difference in thermal expansion coefficient between the base material and the coating layer effectively acts on the through hole, and the through hole can be smoothly expanded in diameter.

  As is clear from the above description, according to the present invention, a circuit body can be easily connected to a member having a plurality of electrode terminals, and electrical and mechanical connection reliability is improved. be able to.

  Embodiments according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is an exploded perspective view of an inkjet head 10 to which an FPC 13 according to the first embodiment of the present invention is connected. The ink-jet head 10 is mounted on the lower part of a carriage (not shown) that can reciprocate in the scanning direction of an ink-jet printer (not shown), and prints in the paper feed direction perpendicular to the scanning direction below the carriage. Printing is performed by transporting the paper, supplying ink from the ink cartridge to the inkjet head, and ejecting the ink from the inkjet head onto the printing paper.

  As shown in FIG. 1, the inkjet head 10 includes a flow path unit 11 in which a plurality of plates are stacked, and a unimorph piezoelectric actuator 12 that is bonded to the flow path unit 11 in an overlapping manner. . The flow path unit 11 is configured such that ink is ejected downward from a nozzle hole 18a (see FIG. 2) opened on the lower surface side of the lowermost layer. The piezoelectric actuator 12 is provided so as to cover the vibration plate 19 disposed facing the flow path unit 11, a common electrode 22 (see FIG. 2) described later formed on the upper surface of the vibration plate 19, and the upper surface of the common electrode 22. And a plurality of individual electrodes 24 arranged on the upper surface of the piezoelectric sheet 23. The individual electrode 24 has a substantially oval main electrode portion 24a similar to a pressure chamber 33, which will be described later, and an individual electrode terminal drawn from the longitudinal end of the main electrode portion 24a to a position not overlapping the pressure chamber 33. 24b. A common electrode terminal 25 that is electrically connected to the common electrode 22 (see FIG. 3) is formed at a required position on the upper surface of the piezoelectric sheet 23.

  On the upper surface of the piezoelectric actuator 12, an FPC (Flexible Printed Circuit) 13 which is a circuit body for making an electrical connection with a control device serving as a drive signal supply source is disposed so as to overlap, and an electrode land exposed on the lower surface of the FPC 13 is disposed. 42 a (see FIG. 2) is conductively connected to the electrode terminals 24 a and 25 of the piezoelectric actuator 12. In addition, an ink supply port 36 covered with a mesh-like filter 35 is formed in the vibration plate 19, and an ink supply port 37 communicating with the ink supply port 36 is also formed in the flow path unit 11.

  FIG. 2 is a cross-sectional view of the main part of the inkjet head 10 to which the FPC 13 shown in FIG. 1 is connected. FIG. 2 shows a cross section cut along a plane orthogonal to the paper feed direction. As shown in FIG. 2, the flow path unit 11 has a configuration in which a pressure chamber plate 15, a connection flow path plate 16, a manifold plate 17, and a nozzle plate 18 are bonded and laminated. The nozzle plate 18 is made of a resin sheet made of polyimide or the like and has an opening for forming a flow path by laser processing or the like, and the other plates 15 to 17 are made of a metal plate such as a stainless steel plate by etching or the like. An opening is formed.

  The pressure chamber plate 15 has a number of pressure chamber holes 15a arranged in two rows so as to extend along the long side in a plan view (viewed from a direction orthogonal to the surface of the diaphragm 19). The pressure chamber holes 15a have an oval shape having a major axis in the scanning direction (a direction orthogonal to the row direction of the pressure chamber holes 15a) in plan view (see FIG. 5). The connection flow path plate 16 has a communication hole 16a that communicates with one end of the pressure chamber hole 15a, and an outflow through hole 16b that communicates with the other end of the pressure chamber 15a. The manifold plate 17 includes a manifold hole 17a extending in the row direction so as to communicate with each row of the pressure chamber holes 15a via the communication holes 16a, and an outflow through hole 17b communicating with the outflow through hole 16b. have. The nozzle plate 18 has a nozzle hole 18a that communicates with the outflow through hole 17b and ejects ink to the outside.

  A common liquid chamber 31 is formed in the flow path unit 11 by sandwiching and closing the upper and lower sides of the manifold hole 17 a between the connection flow path plate 16 and the nozzle plate 18. The common liquid chamber 31 communicates with ink supply ports 36 and 37 (see FIG. 1) to which ink is supplied from an ink tank (not shown). The common liquid chamber 33 communicates with one end portion of the upper pressure chamber hole 15a through the connection flow path 32 formed by the communication hole 16a of the connection flow path plate 16. The pressure chamber 33 is formed by the upper and lower sides of the pressure chamber hole 15a being sandwiched between the diaphragm 19 and the connection flow path plate 16 and closed. A descender 34 formed by the outflow through holes 16b and 17b communicates with the other end portion of the pressure chamber 33, and the descender 34 communicates with the lower nozzle hole 18a.

  The piezoelectric actuator 12 has a vibration plate 19 that is bonded to the upper surface of the flow path unit 11 so as to overlap therewith. The diaphragm 19 includes a diaphragm main body 20 made of a metal plate such as a stainless steel plate, and an insulating layer 21 made of alumina or the like formed on the upper surface of the diaphragm main body 20. On the upper surface of the diaphragm 19, a common electrode 22 continuously arranged corresponding to a large number of pressure chamber holes 15 a is printed. A sheet-like piezoelectric sheet 23 made of a ceramic material of lead zirconate titanate (PZT) is formed on the upper surface of the common electrode 22. The piezoelectric sheet 23 is formed on the diaphragm 19 and the common electrode 22 without using an adhesive by a film forming method such as an aerosol deposition method, a sputtering method, a vapor deposition method, or a sol-gel method. On the upper surface of the piezoelectric sheet 23, a large number of individual electrodes 24 arranged so as to correspond to the respective pressure chamber holes 15a are printed and formed in two rows. The common electrode 22 and the individual electrodes 24 are made of, for example, a metal material such as an Ag—Pd system.

  The polarization direction of the piezoelectric sheet 23 of the piezoelectric actuator 12 is the thickness direction thereof. The piezoelectric actuator 12 is an active layer in which the active portion A that deforms the upper one piezoelectric sheet 23 is present, and the lower diaphragm 19 is used as the lower vibration plate 19. It has a so-called unimorph type configuration as an inactive layer. The active part A is located between the plurality of individual electrode terminals 24b. When a predetermined voltage is applied to the individual electrode 24 through the electrode terminal 24a, for example, if the electric field and polarization are in the same direction, the electric field application portion sandwiched between the electrodes in the piezoelectric sheet 23 acts as the active portion A, and the piezoelectric lateral effect This shrinks in the direction perpendicular to the polarization direction. On the other hand, since the diaphragm 19 is not affected by the electric field and does not spontaneously shrink, a difference in distortion in the direction perpendicular to the polarization direction occurs between the piezoelectric sheet 23 and the diaphragm 19. The seat 23 and the diaphragm 19 are deformed so as to be convex toward the pressure chamber 33 (unimorph deformation). Instead of the diaphragm 19, a piezoelectric sheet that is an inactive layer that is not affected by the electric field may be provided.

  On the surface of the individual electrode terminal 24b of the individual electrode 24, a bump 39 of a conductive adhesive containing a metal material such as Ag and a resin (for example, NH-070A (T) manufactured by Nihon Solder Co., Ltd.) is directed upward. The bumps 39 are electrically connected to the electrode lands 42 a of the FPC 13.

The FPC 13 includes a film-like base material 41, a plurality of conductive wires 42 and electrode lands 42a formed of a conductive metal such as copper foil on the upper surface of the base material 41, and a base material so as to cover the conductive wires 42 from above. 41 and a coating layer 43 formed on the upper surface of 41. The conductive wire 42 has an electrode land 42a at a position corresponding to the bump 39, and is formed in a wiring pattern for individually connecting a driver IC (not shown) mounted on the FPC 13 and the plurality of electrode lands 42a. ing. Further, the upper surface of the covering layer 43 is formed such that the portion corresponding to the electrode land 42 a is higher than the portion corresponding to the active portion A. The base material 41 is made of an insulating material that expands (heat expandability) when heated and returns to its original state (reversibility) when the heating is released, and is made of an insulating material having a high coefficient of thermal expansion such as polyimide. The covering layer 43 is made of an insulating material that shrinks when heated (heat shrinkable) and returns to its original state when heated (reversible). For example, the coating layer 43 is made of Na ₂ SO ₄ , KNO ₃ or Na ₂ CO ₃ encapsulated and mixed with a general solder resist material (for example, epoxy resin) or zirconium tungstate. .

  In the base material 41, a through hole 41a that opens to the lower surface side is formed at a place where the electrode land 42a is disposed. A relay conductor 44 that is electrically connected to the electrode land 42a is formed on the inner peripheral surface that defines the through hole 41a by Cu plating. Further, a second electrode land 45 that is electrically connected to the relay conductor 44 is formed around the through hole 41 a on the lower surface of the base material 41. The second electrode land 45 has an annular shape in plan view, and is formed to have an outer diameter substantially the same as that of the bump 39 in plan view. On the lower surface of the base material 41, a notch 41b having a V-shaped cross section is formed in an annular shape in plan view around the through hole 41a and around the second electrode land 45. Further, a thermoplastic resin layer 46 having an opening 46 a communicating with the through hole 41 a around the through hole 41 a is formed on the lower surface of the base material 41. The thermoplastic resin layer 46 is partially formed so as to be spaced at a position corresponding to the active portion A. The bumps 39 enter the through holes 41a through the openings 46a, come into contact with the relay conductors 44 and the second electrode lands 45, and are connected to the individual electrode terminals 24b in a state in which the thermoplastic resin layer 46 surrounds the bumps 39 and is sealed. Mechanically connected. In this way, the wiring structure 50 composed of the FPC 13 and the piezoelectric actuator 12 is formed.

  Next, the manufacturing procedure of the wiring structure 50 will be described. FIGS. 3-8 is principal part sectional drawing which shows the 1st-6th process at the time of manufacturing FPC13 shown in FIG. 3 to 8 show cross sections cut along a plane orthogonal to the scanning direction. First, as shown in FIG. 3, on the upper surface of the base material 41, a plurality of conductive wires 42 having electrode lands 42 a are printed and formed in a required wiring pattern. Next, as shown in FIG. 4, a coating layer 43 is printed on the upper surface of the base material 41 so as to cover the conductive wires 42. At this time, the upper surface of the covering layer 43 is formed such that the portion 43a corresponding to the electrode land 42a is higher than the portion corresponding to the active portion A.

  Next, as shown in FIG. 5, a cylindrical through hole 41 a that opens downward at the position where the electrode land 42 a is disposed is formed on the lower surface of the base material 41 by etching or laser processing. That is, the upper opening of the through hole 41a is closed by the electrode land 42a. Next, as shown in FIG. 6, the relay conductor 44 that is electrically connected to the electrode land 42 a is formed on the inner peripheral surface that defines the through hole 41 a, and the relay conductor 44 is formed around the through hole 41 a on the lower surface of the base material 41. A conductive second electrode land 45 is formed. At this time, the relay conductor 44 is formed in a bottomed cylindrical shape opening downward, and the second electrode land 45 is formed in an annular shape in plan view in which the inner peripheral edge is continuous with the lower end of the relay conductor 44.

  Next, as shown in FIG. 7, an annular cut portion 41 b is formed on the lower surface of the base material 41 around the through hole 41 a and around the second electrode land 45. The cut portion 41b is formed in a V-shaped cross section so as not to reach the upper surface of the base material 41 by laser processing or etching processing. Next, as shown in FIG. 8, a thermoplastic resin layer 46 (for example, acrylonitrile / styrene) having an opening 46 a communicating with the through hole 41 a provided with the relay conductor 44 around the through hole 41 a on the lower surface of the base material 41. (Resin, methacrylic resin) is applied. The thermoplastic resin layer 46 is partially provided at a position corresponding to the through hole 41a, and is not provided at a position facing the active portion A (see FIG. 2). Further, the thermoplastic resin 46 fills a space having a V-shaped cross section of the cut portion 41b. The FPC 13 is formed by the above procedure. 3 to 8 may be changed, for example, the electrode land 42a may be formed after the through hole 41a is formed, or the through land 41b may be formed after the cut portion 41b is formed. The relay conductor 44 and the second electrode land 45 in the hole 41a may be formed. The second electrode land 45 may be printed on both sides when the electrode land 42a is formed. In this case, the first electrode land 42a is disposed on the upper surface side of the substrate 41, and the lower surface is disposed on the lower surface. After forming a land at a position corresponding to the first electrode land 42a on the side, when forming the through hole 41a, the land is also processed together with the base material 41 to form the annular second electrode land 45 Then, the relay conductor 44 may be provided later.

  9 to 11 are cross-sectional views of the main part showing the first to third steps when connecting the FPC 13 shown in FIG. 9 to 11 show cross sections cut along a plane orthogonal to the scanning direction. As shown in FIG. 9, conductive bumps 39 are formed on the upper surfaces of the individual electrode terminals 24 b formed of the Ag—Pd material of the piezoelectric actuator 12. The bump 39 is formed of a conductive adhesive containing a metal material such as Ag and a resin, and has a flexibility that can be easily deformed by an external force. The dome-shaped outer shape is maintained when no external force is applied. It has become so.

  Next, as shown in FIG. 10, the flat heating surface 60 a of the heater 60 is pressed against the upper surface of the FPC 13 to heat the FPC 13. Then, while the base material 41 is thermally expanded, the coating layer 43 is thermally contracted, and the FPC 13 is pressed downward by the heater 60. Therefore, the FPC 13 expands the diameter of the through hole 41a downward. Transforms into At this time, the FPC 13 is deformed with the notch 41b as a base point, so that the diameter of the through hole 41a is easily increased downward. Further, as the through-hole 41a expands in diameter, the V-shaped space of the cut portion 41b becomes narrow, so that the thermoplastic resin 46 that has entered the space is pushed out of the cut portion 41b and is thermoplastic. A protruding portion 46 b protruding downward is formed on the resin layer 46.

  Next, the FPC 13 is pressed downward by the heater 60 so that the bumps 39 are inserted into the through holes 41a, and the protruding portions 46b of the thermoplastic resin layer 46 are brought into contact with the individual electrode terminals 24b. At this time, since the through hole 41a has an enlarged diameter, the bump 39 is easily inserted into the through hole 41a. Further, since the bump 39 has a flexibility that can be easily deformed by an external force, the bump 39 is deformed so as to fill a space formed by the through hole 41a and the relay conductor 44. In addition, since the thermoplastic resin layer 46 has the opening 46a communicating with the through hole 41a, the thermoplastic resin 46 is prevented from being sandwiched between the bump 39 and the electrode land 42a.

  Further, even if the FPC 13 is deformed by heating and approaches the active part A of the piezoelectric actuator 12, the thermoplastic resin layer 46 is not provided at a position facing the active part A. It is prevented from adhering to. Since the upper surface of the covering layer 43 is formed such that the portion 43a corresponding to the electrode land 42a is higher than the portion corresponding to the active portion A, the heating surface 60a of the heater 60 preferentially contacts the portion 43a, The heat and pressing force applied by the heater 60 are concentrated on the portion 43a to ensure the expansion of the through hole 41a and the contact of the bump 39 with the relay conductor 44, and further to the portion corresponding to the active portion A in the FPC 13. The heat and the pressing force are alleviated and the FPC 13 is prevented from contacting the active part A.

  Next, the heater 60 is released from the state to release the heating. Then, since the thermal expansion of the base material 41 and the thermal contraction of the coating layer 43 are both reversible, the diameter of the through hole 41a is reduced so as to return to the original shape. Then, the relay conductor 44 sandwiches the bump 39, and the relay conductor 44 comes into stable contact with the bump 39. Therefore, the electrical and mechanical connection reliability between the FPC 13 and the piezoelectric actuator 12 is improved.

  Further, by releasing the heating, the through hole 41a is reduced in diameter and restored to the original shape, and at the same time, the thermoplastic resin layer 46 is cured in contact with the individual electrode terminal 24b, and the thermoplastic resin layer 46 is bonded to the adhesive. The FPC 13 is mechanically joined to the individual electrode terminal 24b. Therefore, the bonding strength of the FPC 13 to the piezoelectric actuator 12 is further improved. In addition, when the through hole 41a expands in the thermoplastic resin layer 46, the thermoplastic resin 46 is pushed out from the cut portion 41b, and a protruding portion 46b protruding downward is formed on the thermoplastic resin layer 46. Since the thermoplastic resin layer is thick, when the bump 39 enters the through hole 41a, the periphery of the bump 39 is covered with a lot of thermoplastic resin, and the bonding strength can be improved. Furthermore, since the thermoplastic resin layer 46 comes into contact with the surface of the individual electrode terminal 24 and seals the bump 39, the occurrence of migration or the like can be suitably prevented. Further, the deformation of the active portion A is not affected, and the occurrence of a malfunction of the piezoelectric actuator 12 is prevented.

  As described above, the wiring structure 50 including the FPC 13 and the piezoelectric actuator 12 is formed.

(Second Embodiment)
FIG. 12 is a cross-sectional view of an essential part for explaining an FPC 113 according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the same structure as 1st Embodiment, and description is abbreviate | omitted. As shown in FIG. 12, in the FPC 113 of this embodiment, the coating layer 143 is partially formed on the upper surface of the base material 41 so as to be spaced at positions between the electrode lands 42a. That is, the coating layer 143 is provided at a location covering the conductive wire 42, while the coating layer 143 is not provided at a location where the conductive wire 42 is not disposed. According to this, when the heater 60 (see FIG. 10) is pressed against the FPC 113, the stress caused by the difference in thermal expansion coefficient between the base material 41 and the coating layer 143 works effectively on the through hole 41a. The through hole 41a is smoothly expanded in diameter. Since other configurations are the same as those of the first embodiment described above, description thereof is omitted.

  In each of the embodiments described above, the base material 41 has a thermal expansion property and the coating layers 43 and 143 have a heat shrinkability. However, the present invention is not limited to this, and the thermal expansion coefficient of the coating layer is based on this. It only needs to be smaller than the coefficient of thermal expansion of the material. In each of the embodiments described above, the second electrode land 45 is provided. However, when sufficiently stable conduction can be achieved between the relay conductor 44 and the bump 39, the second electrode land 45 is provided. It does not have to be provided. Further, instead of the thermoplastic resin layer 46, a thermosetting resin layer (for example, an epoxy resin or a solder resist) may be provided. In that case, when expanding the diameter of the through-hole 41a by heating, the temperature of the heater 60 is set so that the uncured thermosetting resin layer does not reach the curing temperature, and the through-hole 41a causes the bump 39 to cover the bump 39 by releasing the heating. After the diameter is reduced so as to be sandwiched, the FPC 13 is heated again by the heater 60 so that the temperature of the thermosetting resin layer is raised to the curing temperature.

  As described above, the method for manufacturing a wiring structure and the circuit body according to the present invention can easily connect a circuit body to a member having a plurality of electrode terminals, and can be electrically and mechanically connected. It is beneficial to apply widely to a connection structure between an inkjet head and an FPC, which has an excellent effect of improving reliability and can exhibit the significance of this effect.

It is a disassembled perspective view of the inkjet head to which FPC which concerns on 1st Embodiment of this invention was connected. It is principal part sectional drawing of the inkjet head to which FPC shown in FIG. 1 was connected. It is principal part sectional drawing which shows the 1st process at the time of manufacturing FPC shown in FIG. It is principal part sectional drawing which shows the 2nd process at the time of manufacturing FPC shown in FIG. It is principal part sectional drawing which shows the 3rd process at the time of manufacturing FPC shown in FIG. It is principal part sectional drawing which shows the 4th process at the time of manufacturing FPC shown in FIG. It is principal part sectional drawing which shows the 5th process at the time of manufacturing FPC shown in FIG. It is principal part sectional drawing which shows the 6th process at the time of manufacturing FPC shown in FIG. FIG. 3 is a cross-sectional view of a main part showing a first step when connecting the FPC shown in FIG. 1 to an actuator. It is principal part sectional drawing which shows the 2nd process at the time of connecting FPC shown in FIG. 1 to an actuator. FIG. 10 is a cross-sectional view of a principal part showing a third step when connecting the FPC shown in FIG. 1 to an actuator. It is principal part sectional drawing explaining FPC which concerns on 2nd Embodiment of this invention.

Explanation of symbols

12 Piezoelectric actuator (member)
13 FPC (circuit body)
24a Individual electrode terminal 39 Bump 41 Substrate 41a Through hole 41b Cut portion 42 Conductor 42a Electrode land 43, 143 Cover layer 44 Relay conductor 45 Second electrode land 46 Thermoplastic resin layer 46a Opening 50 Wiring structure 60 Heater 60a Heating surface

Claims (15)

A method of manufacturing a wiring structure comprising a member having a plurality of electrode terminals formed on a surface and a circuit body electrically connected to the plurality of electrode terminals,
Forming a plurality of conductive wires having electrode lands at positions corresponding to the electrode terminals on the surface of the circuit body opposite to the member of the circuit body including the substrate having thermal reversibility.
Forming a coating layer having a smaller coefficient of thermal expansion than the base material and reversible in thermal expansion and contraction so as to cover at least the conductive wire on the surface opposite to the member of the base material;
Forming a through hole that opens on the member side at the location of the electrode land on the substrate; and
Forming a relay conductor in conduction with the electrode land on a surface defining the through hole;
Forming a plurality of bumps having electrical conductivity and flexibility electrically connected to the plurality of electrode terminals on the surface of the member;
Expanding the diameter of the through hole toward the member by heating the circuit body; and
In the state where the bump is inserted into the enlarged through hole, the step of reducing the diameter of the through hole by releasing the heating;
A method for manufacturing a wiring structure, comprising:   The method for manufacturing a wiring structure according to claim 1, wherein the base material has a thermal expansion property and the coating layer has a heat shrinkability. Forming a synthetic resin layer having an opening communicating with the through hole at least around the through hole on the member-side surface of the substrate;
The method for manufacturing a wiring structure according to claim 1, further comprising a step of curing the synthetic resin layer in contact with the surface of the member so as to surround the bump. The synthetic resin layer is composed of a thermoplastic resin layer,
The method of manufacturing a wiring structure according to claim 3, wherein the step of curing the synthetic resin layer is a step of releasing the heating. The member is an actuator in which an active portion that is deformed according to a signal supplied to the electrode terminal is disposed between the plurality of electrode terminals,
The synthetic resin layer is partially formed so as to be spaced at a position corresponding to the active portion, and is cured while being in contact with the surface of the electrode terminal so as to surround the bump. A method for manufacturing a wiring structure according to 3 or 4.   The method for manufacturing a wiring structure according to claim 1, wherein a notch is formed around the through hole on the surface of the base member on the member side.   7. The wiring structure according to claim 1, wherein a second electrode land that is electrically connected to the relay conductor is formed around the through-hole on the member-side surface of the base material. Manufacturing method.   The method for manufacturing a wiring structure according to claim 1, wherein the covering layer is partially formed so as to be spaced at positions between the plurality of electrode lands. The member is an actuator in which an active portion that is deformed according to a signal supplied to the electrode terminal is disposed between the plurality of electrode terminals,
The surface of the circuit body on the coating layer side is formed such that the surface of the portion corresponding to the electrode land is higher than the surface of the portion corresponding to the active portion,
9. The method of manufacturing a wiring structure according to claim 1, wherein in the heating step, the surface of the circuit body is pressed by a heater having a flat heating surface. A substrate;
A plurality of conductive wires formed on one surface of the substrate and having electrode lands;
A coating layer formed so as to cover at least the conducting wire on one surface of the base material,
In the base material, a through hole that opens to the other surface side of the base material is formed at a position where the electrode land is disposed, and a relay conductor that is electrically connected to the electrode land is formed on a surface that defines the through hole. Formed,
The base material and the coating layer have reversible thermal expansion and contraction,
The circuit body characterized in that the thermal expansion coefficient of the coating layer is smaller than the thermal expansion coefficient of the substrate.   The circuit body according to claim 10, wherein the base material has a thermal expansion property, and the coating layer has a heat shrinkability.   The circuit body according to claim 10, further comprising a synthetic resin layer having an opening communicating with the through hole at least around the through hole on the other surface of the base material.   The circuit body according to claim 10, wherein a cut portion is formed around the through hole on the other surface of the base material.   The circuit body according to claim 10, wherein a second electrode land that is electrically connected to the relay conductor is formed around the through hole on the other surface of the base material.   The circuit body according to claim 10, wherein the covering layer is partially formed so as to be spaced at positions between the plurality of electrode lands.

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