JP5044246B2 - Multilayer printed wiring board and method for manufacturing multilayer printed wiring board - Google Patents

Description

The present invention relates to a multilayer printed wiring board in which a resin base material on which a wiring pattern is formed is superposed and thermocompression bonded by a heating / pressurizing unit and a method for manufacturing the multilayer printed wiring board.

  Electronic devices such as personal digital assistants and digital cameras are required to be smaller, have higher performance, and be thinner. To meet the demands of these electronic devices, various modules can be used without internal signal connection connectors that occupy a large volume. Multi-layer printed wiring boards in which the parts are connected flexibly without connectors have been developed and commercialized.

Patent Document 1 and Patent Document 2 are multilayer printed wiring boards called so-called flex-rigid wiring boards, and a resin substrate made of a thermoplastic resin film such as polyimide having a wiring pattern formed of copper foil is applied to the resin by a laser or the like. A via hole is formed to connect the wiring pattern layers of the base material, and a plurality of the resin base materials filled with the conductive material such as a conductive paste are stacked by vacuum printing to form a laminated sheet Furthermore, via holes for connecting the wiring pattern layers of the second resin base material are formed by laser or the like on the second resin base material on which the wiring pattern is formed of the copper foil, and conductive by vacuum printing or the like. The second resin base material in which the via hole is filled with a conductive material such as a paste is superimposed on the laminated sheet via a thermosetting adhesive. Allowed by a laminated sheet for a multilayer printed wiring board manufacturing for electrically connecting with integrated by being thermocompression bonding. As a method for producing a multilayer printed wiring board, as shown in Patent Document 1 and Patent Document 2, a wiring pattern is formed with a copper foil on a thermoplastic resin film, and a conductive paste for interlayer connection is filled and cured. Then, a plurality of resin base materials made of the thermoplastic resin film are overlaid and formed by thermocompression bonding and electrically connected to form a flex wiring board, on the flex wiring board, After forming an adhesive layer made of a thermosetting adhesive, and then forming a wiring pattern with a copper foil on the second resin substrate, filling and curing the interlayer connection conductive paste, A method for manufacturing a multilayer printed wiring board is disclosed in which two resin base materials are superposed on the above-mentioned flex wiring board and integrated by thermocompression bonding and electrically connected. In this manufacturing method, the resin base material is filled with a conductive paste by forming a bottomed via hole with a laser or the like, and after laminating the resin base material, the metal particles which are the main components of the conductive paste are heated. Since melting and forming solder bumps to electrically connect the layers, compared to the method of forming a through hole (through hole) with the NC drill or the like on the base material and performing plating treatment, and electrically connecting the layers, The wiring pattern can be made thin and is suitable for a high-density wiring board.
Japanese Patent Publication WO2004 / 093508 JP 2005-109299 A

  However, the adhesive layer composed of the thermosetting adhesive and the binder of the conductive paste described in Patent Document 1 and Patent Document 2 have a property that the viscosity is lowered during the thermosetting process and subsequently becomes high viscosity and hardens. is there. That is, when the adhesive layer made of the thermosetting adhesive has a low viscosity in the process of thermosetting, the binder of the conductive paste for interlayer connection filled in the second resin base material has a low viscosity. There is a problem that short-circuit failure or insulation resistance deterioration failure is liable to occur when metal scraps such as solder that has melted or softened in the state and exudes adhere to the wiring. Further, the elastic modulus of the second resin base material is a temperature at which the binder of the conductive paste for interlayer connection filled in the second resin base material becomes a low viscosity state in the process of thermosetting. If it is small, there is a problem that the shape of the via collapses due to thermal deformation of the second resin base material, which eventually causes disconnection or high resistance.

Accordingly, an object of the present invention is to cause seepage due to melting or softening of the binder of the conductive paste for interlayer connection or deformation of the via due to thermal deformation of the resin base material when thermocompression bonding is performed by heating / pressurizing means. It is to provide a method for manufacturing a multilayer printed wiring board and multilayer printed wiring board so as not.

Multilayer printed wiring board of the present invention is a multilayer printed circuit board having a heat-bonding a resin substrate on which a wiring pattern is formed is overlapped by the heat and pressure means by a conductor foil, an interlayer that is filled in the via hole and cured A first resin base material having a first conductive paste for connection; a second resin base material having a second conductive paste for interlayer connection filled in a via hole and cured; and a first resin base material When an adhesive layer for bonding the second resin substrate, the adhesive layer is made of thermosetting adhesive, the first conductive paste and the second conductive paste, any heat The binder is a curable adhesive, and the gelation temperature (Tp2) of the binder of the second conductive paste is lower than the gelation temperature (Tp1) of the binder of the first conductive paste (Tp2 <Tp1) The The second binder gelling temperature of the conductive paste (Tp2) is configured as a low temperature (Tp2 <Sp) than the gelling temperature of the adhesive layer (Sp), said first conductive paste No. The first metal particles have a melting point (Tk1) equal to or lower than the gelation temperature (Tp1) of the first binder (Tk1 ≦ Tp1), The conductive paste contains second metal particles, and the melting point (Tk2) of the second metal particles is configured to be equal to or lower than the gelation temperature (Tp2) of the second binder (Tk2 ≦ Tp2). Furthermore, the melting point (Tk2) of the second metal particles is configured to be lower than the melting point (Tk1) of the first metal particles (Tk2 <Tk1) .
Method for manufacturing a multilayer printed circuit board of the present invention relates to a method for manufacturing a multilayer printed wiring board you thermocompression bonding by heating and pressurizing means superposed resin substrates on which a wiring pattern is formed by conductive foil, filled into the via holes a first resin substrate having a first conductive paste for interlayer connections Ru cured, and the second resin substrate having a second conductive paste for interlayer connection that Ru is filled in the via hole curing, When forming a laminated sheet including an adhesive layer for bonding the first resin base material and the second resin base material, the adhesive layer is a thermosetting adhesive, and the first conductive paste is used. and the second conductive paste are both thermosetting adhesive and binder, the second gelation temperature of the binder of the conductive paste (Tp2) a first binder gelling temperature of the conductive paste (Tp1) Lower temperature Tp2 configured as <Tp1), constitute the second gelation temperature of the binder of the conductive paste (Tp2) as the gelling temperature of the adhesive layer (Sp) lower than the temperature (Tp2 <Sp), said first The conductive paste contains first metal particles, and the melting point (Tk1) of the first metal particles is configured to be equal to or lower than the gelation temperature (Tp1) of the first binder (Tk1 ≦ Tp1). The second conductive paste contains second metal particles, and the melting point (Tk2) of the second metal particles is equal to or lower than the gelation temperature (Tp2) of the second binder (Tk2). ≦ Tp2) configured as further constitutes a melting point (Tk2) of the second metal particles as low temperature (Tk2 <Tk1) than the melting point (Tk1) of said first metal particles by the thermocompression bonding Unite The features.

  Here, the above-mentioned gelation temperature is a reaction of a polyfunctional monomer having a plurality of polymerizable functional groups, and when a molecule having three or more functionalities is contained in the reaction, it has a high three-dimensional network structure. A molecule is generated. The gelation point is the point where the insoluble part (gel part) begins to grow and increase during the polymerization in this three-dimensional reaction system, and is recognized as the point where the viscosity of the reaction system rises rapidly (Iwanami Shoten RIKEN Dictionary) . In the present specification, the gelation temperature is synonymous with the gelation point.

  According to these inventions, since the gelation temperature (Tp) of the binder of the conductive paste to be cured is configured to be lower than the gelation temperature (Sp) of the adhesive layer, When thermocompression bonding, the binder of the conductive paste has a low viscosity, and even if it is melted or softened, the adhesive layer does not melt or soften, and it is possible to prevent the conductive paste from bleeding due to melting or softening. Is done. Further, the melting point (Tk) of the metal particles of the conductive paste to be cured is equal to or lower than the gelation temperature (Tp) of the binder of the conductive paste (Tk ≦ Tp), so that the binder can be removed during the thermal curing process. In the melted or softened state, the metal particles are melted, and metal bonds between the metal particles are easily formed. When the viscosity of the adhesive layer is lowered, the binder of the conductive paste has been cured, and the via shape is maintained. For this reason, a high quality multilayer printed wiring board can be manufactured.

The present invention, respectively with the first conductive paste and the second conductive paste, tin (Sn), silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In) or A mixture containing a plurality of different metal particles selected from these alloys is preferable. Here, when the first and second metal particles are a mixture of a plurality of different kinds of metal particles, the melting point of the metal particles made of the metal having the lowest melting point is referred to as “the melting point of the first metal particles (Tk1). ) "And" the melting point of the second metal particle (Tk2) ".

  According to these inventions, the gelation temperature (Tp2) of the binder of the second conductive paste to be cured is configured as a temperature (Tp2 <Sp) lower than the gelation temperature (Sp) of the adhesive layer. From the above, when thermocompression bonding is performed by heating / pressurizing means, a state where the adhesive layer does not melt or soften even when the second conductive paste melts is obtained, and by the melting or softening of the binder of the second conductive paste The situation where bleeding occurs is prevented, and the via shape of the second conductive paste for interlayer connection filled in the via hole and hardened is difficult to deform. Further, the melting point (Tk2) of the second metal particles of the second conductive paste to be cured is equal to or lower than the gelation temperature (Tp2) of the binder of the conductive paste (Tk2 ≦ Tp2). In a state where the binder is melted or softened during the curing process, the second metal particles are melted, and metal bonds between the metal particles are easily formed.

  Then, since the gelation temperature (Tp2) of the binder of the second conductive paste to be cured is configured to be lower than the gelation temperature (Tp1) of the binder of the first conductive paste to be cured, the heating -When thermocompression bonding is performed by the pressurizing means, a state in which the binder of the first conductive paste is not melted or softened even if the second conductive paste is melted is obtained, and by the melting or softening of the binder of the first conductive paste The occurrence of seepage is prevented, and the via shape of the first conductive paste for interlayer connection that is filled and cured in the via hole is difficult to deform. When the first metal particles constituting the first conductive paste and the second metal particles constituting the second conductive paste are the same substance, the first resin base material is formed in the step of creating the first resin base material. After the alloyed metal composition of the first conductive paste is formed in the via hole, the metal particles of the second conductive paste melt when the second resin base material is further laminated on the first resin base material. Even when the substrate is heated at a temperature, the metal composition obtained by alloying the first conductive paste is not remelted, the shape of the via of the first resin substrate is maintained, and a good interlayer is maintained. Connection status is obtained. In addition, when the first metal particles constituting the first conductive paste and the second metal particles constituting the second conductive paste are different substances, the melting point (Tk2) of the second metal particles is determined. By adopting a configuration in which the temperature is lower than the melting point (Tk1) of the first metal particles (Tk2 <Tk1), the first metal particles are not melted even if the second metal particles are melted. The via shape is maintained and a good interlayer connection is obtained.

The present invention is configured such that the elastic modulus (Y1) of the first resin base material at the gelation temperature (Tp1) of the binder of the first conductive paste is 0.1 GPa or more (Y1 ≧ 0.1 GPa) , and said elastic modulus of the second resin substrate in the second binder gelling temperature of the conductive paste (Tp2) (Y2) is configured as above 0.1GPa (Y2 ≧ 0.1GPa) It is characterized by.

  According to the present invention, the elastic modulus (Y1) of the first resin substrate at the gelation temperature (Tp1) of the binder of the first conductive paste is 0.1 GPa or more (Y1 ≧ 0.1 GPa). Therefore, when thermocompression bonding is performed by heating / pressurizing means, even if the binder of the first conductive paste is melted or softened, the first resin base material is prevented from being thermally deformed and filled into the via hole and cured. The via shape of the first conductive paste for interlayer connection is not easily deformed. In addition, the elastic modulus (Y2) of the second resin base material at the gelation temperature (Tp2) of the binder of the second conductive paste is 0.1 GPa or more (Y2 ≧ 0.1 GPa). -When thermocompression bonding is performed by a pressurizing means, even if the binder of the second conductive paste is melted or softened, the second resin base material is prevented from being thermally deformed, and the interlayer connection is filled and cured in the via hole. The via shape of the second conductive paste for use is not easily deformed.

  According to the present invention, it is possible to prevent the occurrence of leakage due to melting or softening of the binder of the conductive paste and the deformation of the via due to the thermal deformation of the resin base material. It becomes possible to provide a high-quality multilayer printed wiring board having no resistance and a manufacturing method thereof.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic sectional view of a laminated sheet Z1 for manufacturing a multilayer printed wiring board to which the present invention is applied. The present embodiment is a laminated sheet including a first resin base material 1a in which a wiring pattern is formed by a conductor foil 1e and a second resin base material 2a in which a wiring pattern is formed by a conductor foil 2e. The first resin base material 1a is provided with a conductive paste 1p for interlayer connection which is filled and cured in via holes, and an adhesive layer EP is provided on the lower surface side of the first resin base material 1a. The conductive paste 1p preferably includes a thermosetting epoxy adhesive as a binder 1ep and contains metal particles 1me that melt by heating at a temperature (Tk) that is equal to or lower than the gelation temperature (Tp) of the binder 1ep ( Tk ≦ Tp). In a state where the binder 1ep is melted or softened in the process of thermosetting, the metal particles 1me are melted, and metal bonds between the metal particles are easily formed, and the metal particles 1me are melted and the metal particles are bonded to each other. In order to form an alloy layer by metal diffusion and a wiring pattern made of a conductive foil, the wiring pattern made of the conductive foil 1e is electrically connected to the interlayer, and the interlayer connection is made by a thermosetting epoxy adhesive having high heat resistance and strong adhesive strength. It is because it is made strong. Specifically, the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is 150 ° C. to 170 ° C., and the melting temperature (Tk) of the metal particles 1me is equal to or lower than the gelation temperature (Tp) of the binder 1ep. The temperature is 140 ° C to 150 ° C.

  The gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is configured to be lower than the gelation temperature (Sp) of the adhesive layer EP (Tp <Sp). The elastic modulus (Y1) of the first resin substrate 1a at the gelation temperature (Tp) of the binder of the conductive paste 1p is configured to be 0.1 GPa or more (Y1 ≧ 0.1 GPa). Furthermore, the elastic modulus (Y2) of the second resin substrate 2a at the gelation temperature (Tp) of the binder of the conductive paste 1p is preferably configured to be 0.1 GPa or more (Y2 ≧ 0.1 GPa). Specifically, the gelation temperature (Sp) of the adhesive layer EP is 180 ° C. to 200 ° C., and the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is the gelation temperature (Sp) of the adhesive layer EP. Lower than 150 ° C. to 170 ° C. Moreover, the 1st resin base material 1a is a liquid crystal polymer, and the 2nd resin base material 2a is polyamide. Accordingly, when the binder 1ep of the conductive paste 1p is melted or softened when the thermocompression bonding is performed by the heating / pressurizing means K1 and K2, a state where the adhesive layer Ep is not melted is obtained, and the binder 1ep of the conductive paste 1p is not melted. A situation where exudation due to melting or softening occurs is prevented, and a situation where thermal deformation of the first resin substrate 1a is prevented, and the first conductive paste 1p for interlayer connection which is filled and cured in the via hole 1h is prevented. Since the via shape 1h is difficult to deform, a laminated sheet (multilayer printed wiring board) Z1 for manufacturing a high quality multilayer printed wiring board is manufactured.

  FIG. 11 is a graph schematically showing the relationship between the gelation temperature (Sp) of the adhesive layer EP, the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p, and the melting point (Tk) of the metal particles 1me. The vertical axis of the graph represents viscosity, and the horizontal axis of the graph represents temperature (heating temperature). By heating, first, the metal particles 1me (marked with * in the figure) start to melt at the melting point (TK), and then the binder 1ep of the conductive paste 1p becomes the gel point (Tp1) that is the lowest viscosity, and the viscosity continues to rise rapidly. Heat curing starts. Then, the adhesive layer EP becomes a gel point (Sp) that is the lowest viscosity, and the viscosity rapidly increases and thermosetting starts. When the metal particle 1me is a mixture of a plurality of different metal particles, the melting point of the metal particle made of the metal having the lowest melting point is referred to as “the melting point of the metal particle 1me”.

(Comparative Example 1)
FIG. 2A shows a case where the gelation temperature (Sp) of the adhesive layer EP is lower than the gelation temperature (Tph) of the binder hep of the conductive paste hp, contrary to the above. FIG. 2B is a cross-sectional photograph of the comparative example 1 in a state of being thermocompression bonded. Specifically, the gelation temperature (Sp) of the adhesive layer EP is 180 ° C. to 200 ° C., and the gelation temperature (Tph) of the binder hep of the conductive paste hp is the gelation temperature (Sp) of the adhesive layer EP. Higher than 210 ° C to 220 ° C. As is apparent from FIG. 2B, when the adhesive layer EP is melted or softened during the thermocompression bonding, the binder hep of the conductive paste hp is also melted, and the metal particles 1me also flow together. (Exudates). Here, the exuded portion is indicated by an arrow, and the conductive paste hp is scattered between the wiring patterns made of the conductor foil 2e.

(Comparative Example 2)
FIG. 3A shows a state in which the gelation temperature (SL) of the adhesive layer EPL is the same as the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p and is thermocompression-bonded in Comparative Example 2. FIG. 3B is a photograph of the comparative example 2 in a state of being thermocompression bonded. Specifically, the gelation temperature (SL) of the adhesive layer EPL is 150 to 170 ° C., and the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is equal to the gelation temperature (SL) of the adhesive layer EP. The same 150 ° C. to 170 ° C. is set. As is apparent from FIG. 3B, when the adhesive layer EPL is melted or softened during the thermocompression bonding, the metal particles 1me of the conductive paste 1p also flow (exude). Here, the exuded portion is indicated by an arrow, and the conductive paste 1p is scattered between the wiring patterns made of the conductive foil 2e.

Example 1
On the other hand, FIG. 4A shows the embodiment in which the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is lower than the gelation temperature (Sp) of the adhesive layer EP. FIG. 4 (b) is a photograph of the state after thermocompression bonding. Specifically, the gelation temperature (Sp) of the adhesive layer EP is 180 ° C. to 200 ° C., the first resin substrate 1a is a liquid crystal polymer, and the second resin substrate 2a is polyamide. is there. The gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is set to 150 ° C. to 170 ° C., which is lower than the gelation temperature (Sp) of the adhesive layer EP. Therefore, according to the present embodiment, even when the conductive paste 1p is melted during the thermocompression bonding, the adhesive layer EP does not melt or soften, so that the binder 1ep of the conductive paste 1p oozes out. Is prevented. Further, since the elastic modulus (Y1) of the first resin base material 1a at the gelation temperature (Tp) of the binder 1ep of the conductive paste 1p is 0.1 GPa or more (Y1 ≧ 0.1 GPa), the conductive paste 1p The first resin base material 1a is prevented from being thermally deformed in the step of curing and the via shape of the conductive paste 1p for interlayer connection that is filled and cured in the via hole 1h is difficult to deform.

(Second Embodiment)
FIG. 5 is a schematic cross-sectional view of a laminated sheet Z2 for producing a multilayer printed wiring board to which the present invention is applied. The laminated sheet Z2 for manufacturing a multilayer printed wiring board is formed of a thermoplastic resin such as a liquid crystal polymer or polyimide in which a wiring pattern made of a conductive foil 11e such as a copper foil is formed and filled with a first conductive paste 11p for interlayer connection. A wiring pattern composed of a first laminated sheet (resin substrate) 11 in which a plurality of resin base materials 11a, 11b, and 11c made of a film are stacked and a conductor foil 12e such as a copper foil is formed, and the first laminated sheet 11 is formed. A second laminated sheet (resin base material) made of the second resin base material 12a1, 12a2, 12b1, 12b2 filled with the second conductive paste 12p for interlayer connection formed with an adhesive layer EP for adhering to the base material ) 12. As schematically shown in FIG. 6, the laminated sheet Z2 for producing a multilayer printed wiring board is electrically connected between a rigid portion R1 on which electronic components are mounted and a rigid portion R2 on which electronic components are mounted. 2 is a laminated sheet for manufacturing a flex-rigid wiring board, in which a flexible portion FL connected to is formed. Then, the first laminated sheet 11 is integrated by thermocompression bonding by the heating / pressurizing means K1, K2, and one side and the other side 12a1 of the second laminated sheet are respectively provided on the upper and lower sides of the first laminated sheet 11. , 12a2 and the first and second laminated sheets are integrated with each other by the adhesive layer EP. In the conventional flex-rigid circuit board, the rigid portion R1 and the rigid portion R2 are electrically connected by a connection connector that occupies a large volume. It will be less, and it will be thinner and smaller. In addition, since the rigid portion R1 and the rigid portion R2 can be flexibly connected, for example, in a portable information terminal or the like in which the liquid crystal display portion and the information input portion are foldably connected, the liquid crystal module R1 and the information input module R2 are It is suitable for the specification to be flexibly connected by the flexible part FL.

  In the present embodiment, the second resin base materials 12a1, 12a2, 12b1, and 12b2 arranged on the upper and lower outer sides are made of a highly heat-resistant thermosetting epoxy resin or a prepreg in which a glass fiber is impregnated with an epoxy resin. Although preferable, a thermoplastic resin such as polyimide may be used. The adhesive layer EP is preferably a thermosetting epoxy adhesive having high heat resistance and strong adhesive strength. Moreover, you may form both 2nd resin film 12a1, 12a2, 12b1, 12b2 and adhesive bond layer EP simultaneously with an epoxy adhesive itself.

  The first laminated sheet (resin base material) 11 is formed by laminating a plurality of resin base materials 11a, 11b, and 11c made of a thermoplastic resin film, and pressurizing and heating to weld the joining surfaces of the thermoplastic resin films. In addition, the second resin base materials 12a1, 12a2, 12b1, 12b2 are overlapped so as to sandwich the first laminated sheet 11, and pressurized and heated to cure the adhesive layer EP. It is integrated. The first conductive paste 11p is cured by heating, and electrically connects the wiring pattern made of one conductor foil 11e and the wiring pattern made of the other conductor foil 11e provided in the first laminated sheet 11. The second conductive paste 12p is cured by heating, and electrically connects the wiring pattern made of the conductive foil 12e and the wiring pattern made of the conductive foil 11e provided on the second resin base materials 12a1, 12a2, 12b1, and 12b2. Then, a three-dimensional wiring pattern is formed. And the wiring pattern which consists of conductor foils 12e, such as copper exposed on the surface layer, is covered with the solder resist sr except the part which electrically connects an electronic component in order to prevent the malfunction etc. by the wiring pattern adhesion of a solder scrap. Hereinafter, in this embodiment, the resin base materials 11a, 11b, and 11c made of a thermoplastic resin film are described as three layers for convenience, but the same applies to two layers or four or more layers. In the case of one layer, the laminated sheet forming step may be omitted. For convenience, the second resin base materials 12a, 12b, 12c, and 12d are superposed on the base material 11 one layer at a time, but the same applies when two or more layers are superposed. Further, the second conductive paste 12p for interlayer connection may be appropriately provided in any of the second resin base materials 12a1, 12a2, 12b1, and 12b2 depending on the design of the wiring circuit.

  The wiring pattern formed by the conductive foils 11e such as copper disposed on the resin base materials 11a and 11c made of the thermoplastic resin film as the surface layer portion of the inner first laminated sheet (resin base material) 11, When exposed to the surface, corrosion due to moisture absorption or the like is likely to occur, and in a conventional sequentially laminated multilayer printed wiring board, a protective sheet called a coverlay had to be attached to the surface layer portion. On the other hand, in the multilayer printed wiring board Z2 of the present embodiment, the first laminated sheet (resin base material) 11 is arranged on the resin base materials 11a and 11c made of the thermoplastic resin film as the surface layer portion. The wiring pattern is formed so that the wiring pattern formed of the conductive foil 11e such as copper is not exposed on the surface of the flexible part FL, and the resin base materials 11a and 11c itself made of the thermoplastic resin film as the surface layer part are formed. The wiring pattern formed by the conductor foil 1e of the rigid portion R1 and the rigid portion R2 plays the role of the coverlay, and the second resin base materials 12a1, 12a2, 12b1, 12b2 themselves play the role of the coverlay. Therefore, it is possible to omit a protective sheet called a coverlay, which has been essential in the past (FIGS. 5 and 6).

  FIG. 7 is a process flowchart showing the manufacturing procedure of the second embodiment. 8 to 10 are workpiece cross-sectional views in the main manufacturing process. A method for manufacturing the multilayer printed wiring board Z2 to which the present invention is applied will be described below in accordance with the process flowchart shown in FIG. S1 to S9 are flexible part FL formation processes, and S11 to S18 are rigid part R1 and R2 formation processes. This manufacturing method is also called a batch stacking method, and since the flexible part FL and the rigid parts R1 and R2 can be formed in parallel, the production period is reduced to about half compared with the conventional sequential stacking method. it can.

  Regarding the flexible part FL forming step, first, a conductor foil 11e such as a copper foil is bonded to one surface of a resin base material 11c (11a, 11b) made of a thermoplastic resin film such as a liquid crystal polymer or polyimide, and thermocompression bonding is performed. Alternatively, the conductor foil 11e is attached to the resin base material 11c (11a, 11b) made of a thermoplastic resin film by a casting method or the like (FIG. 7 (S1), FIG. 8 (a)). For bonding the conductive foil 11e and the resin base material 11c (11a, 11b) made of a thermoplastic resin film, a so-called three-layer structure bonded with an adhesive and a thermoplastic resin without using an adhesive. There are so-called two-layer structures that are welded by melting the adhesive surfaces, and they are used properly depending on the application. Next, a protective film CF made of polyethylene, PET, or the like is adhered to the other surface of the resin base material 11c (11a, 11b) made of a thermoplastic resin film (FIG. 7 (S2), FIG. 8 (b)). ). Then, a wiring pattern is formed on the conductive foil 1e by etching or the like (FIG. 7 (S3), FIG. 8 (c)), and the outer dimensions are adjusted by cutting or the like, or a guide hole is formed (FIG. 7 (S4)). FIG. 8 (c)). The process order of S2 to S4 may be appropriately changed depending on the process design.

  Next, a predetermined position on the other surface of the resin base material 11c (11a, 11b) made of the thermoplastic resin film with the protective film CF attached is irradiated with a laser or the like to connect the wiring patterns to each other. A via hole (hole) 11h is formed (FIG. 7 (S5), FIG. 8 (d)). The via hole 11h has a bottomed hole shape in which at least a part reaches the inner surface of the conductor foil 11e. Then, the first conductive paste 11p is filled into the via hole 11h by vacuum printing or the like. The first conductive paste 11p is filled and cured to the height of the protective film CF (FIG. 7 (S6), FIG. 8 (d)). Next, when the protective film CF is peeled off, the first conductive paste 11p protrudes from the other surface of the resin base material 11c (11a, 11b) made of a thermoplastic resin film by the thickness of the protective film CF. (FIG. 7 (S7), FIG. 8 (e)). The thickness of the protective film CF is usually 12 μm to 100 μm, but is appropriately adjusted according to the processing conditions. In this way, the resin base materials 11a, 11b, and 11c made of the thermoplastic resin film filled with the first conductive paste 11p are overlaid, the copper foil sheet 11e is disposed on the uppermost stage, and thermocompression bonding is performed. One conductive paste 11p is cured, and the wiring pattern made of one conductor foil 11e and the wiring pattern made of the other conductor foil 11e provided on the substrate 1 are electrically connected. And the resin base material 11a, 11b, 11c which consists of the thermoplastic resin film which forms the base material 11, and the copper foil sheet | seat 11e arrange | positioned at the uppermost stage melt | dissolve the adhesive surfaces of a thermoplastic resin, or thermoset of an adhesive agent. (FIG. 7 (S8), FIG. 8 (f)). That is, the resin base material 11 integrated by the thermocompression bonding by the heating / pressurizing means K1, K2 is manufactured. The outermost copper foil 11e is formed with a wiring pattern by etching or the like to become the flexible wiring board 11 (FIG. 7 (S9), FIG. 8 (g)).

  Here, the 1st electrically conductive paste 11p is the structure which mixes a thermosetting epoxy adhesive as the binder 11ep with the metal particle 11me which fuse | melts by heating. Specifically, the metal particles 11me are tin (Sn), silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), or a plurality of these alloys. It is a mixture containing different metal particles. The gelation temperature (Tp1) of the binder 11ep is 190 ° C. to 200 ° C., and the melting temperature (Tk1) of the metal particles 11me is equal to or lower than the gelation temperature (Tp1) of the binder 11ep. ℃. Here, the melting temperature (Tk1) of the metal particles 11me refers to the melting point of metal particles made of a metal having the lowest melting point among the plurality of different metal particles. The elastic modulus (Y1) of the first resin substrate 11a at the gelation temperature (Tp1) of the binder 11ep of the first conductive paste 11p is 0.1 GPa or more (Y1 ≧ 0.1 GPa). Heating by the heating / pressurizing means K1, K2 at the time of gelation of the binder 11ep of the first conductive paste 11p is about 200 ° C. By heating the first conductive paste 11p, at least some of the low melting point metal particles (the metal having the lowest melting point among the plurality of different metal particles) contained in the first conductive paste 11p at 180 ° C. to 190 ° C. A wiring pattern composed of one conductor foil 11e and a wiring pattern composed of the other conductor foil 11e provided on the resin base material 11 by melting and diffusing with other refractory metal particles. The binder 11ep contained in the electrically conductive paste 11p is thermally cured, and is heated at a heating temperature of about 300 ° C. by the heating / pressurizing means K1 and K2, so that the thermoplastic resin substrate 11a, 11b, 11c and the copper foil 11e are integrated.

  Next, regarding the formation process of the rigid parts R1, R2, first, a conductor foil 12e such as a copper foil is bonded to one surface of a prepreg 12b (12a) in which a glass fiber is impregnated with an epoxy resin, and thermocompression bonded. A single-sided copper-clad plate is formed by the above, or a conductor foil 12e such as a copper foil is once bonded to both sides of the prepreg 12b (12a) and thermocompression bonded, and then one side is removed by etching or the like (FIG. 7 (S11)). , FIG. 9 (a)). Next, an adhesive layer EP made of a thermosetting adhesive is provided on the other surface of the single-sided copper-clad plate 12b (12a). For example, the adhesive layer EP before thermosetting is obtained in a dry state by thick-film printing a thermosetting epoxy adhesive and volatilizing the solvent component contained in the thermosetting epoxy adhesive EP (FIG. 7 ( S12)). Here, by using a commercially available FR-4 single-sided copper-clad board with a base adhesive, steps S11 and S12 in-house can be omitted. Next, in order to protect the adhesive layer EP, a protective film CF made of polyethylene, PET, or the like is adhered and attached, or a protective film pre-applied with an adhesive is attached to the single-sided copper-clad plate 12b (12a). (FIG. 7 (S13), FIG. 9 (b)). Then, a wiring pattern is formed on the conductor foil 2e by etching or the like (FIG. 7 (S14), FIG. 9 (c)), and a place corresponding to the flexible portion FL is extracted by pressing or the like to adjust the outer dimensions (FIG. 7 ( S15), FIG. 9 (c)). The process order of S14 to S15 may be appropriately changed for convenience of process design. Then, a laser or the like is irradiated to a predetermined position on the other surface of the single-sided copper-clad plate 12b (12a) to which the protective film CF is attached to form a via hole 12h for interconnecting the wiring patterns (FIG. 7). (S16), FIG. 9 (d)). The via hole 2h has a bottomed hole shape in which at least a part reaches the inner surface of the conductor foil 2e. Then, the second conductive paste 12p is filled into the via hole 12h by vacuum printing or the like. The first conductive paste 11p is filled and cured to the height of the protective film CF (FIG. 7 (S17), FIG. 9 (d)). Next, when the protective film CF is peeled off, the second conductive paste 12p protrudes from the other surface of the single-sided copper-clad plate 12b (12a) by the thickness of the protective film CF (FIG. 7 (S18)). , FIG. 9 (e)). The thickness of the protective film CF is usually 12 μm to 100 μm, but is appropriately adjusted according to the processing conditions. In this way, single-sided copper-clad plates 12a, 12b (12a1, 12a2, 12b1, 12b2) filled with the second conductive paste 2p are formed. In addition, the 2nd lamination sheet 12 which consists of the said single-sided copper clad board 12a, 12b (12a1, 12a2, 12b1, 12b2) may be a single | mono layer or multiple layers.

  Then, the second conductive paste 12p is formed by thermocompression bonding the single-sided copper-clad plates 12a1, 12a2, 12b1, 12b2 on both surfaces of the resin base material 11 so that the copper foil 2e is the outermost layer. Is thermally cured to form a three-dimensional wiring pattern by electrically connecting the wiring pattern made of one conductive foil 2e and the wiring pattern made of the other conductive foil 1e provided on the single-sided copper-clad plates 12a1, 12a2, 12b1, 12b2 Is done. That is, a laminated sheet Z2 for producing a multilayer printed wiring board integrated by thermocompression bonding by the heating / pressurizing means K1, K2 is produced. The single-sided copper-clad plates 12a1, 12a2, 12b1, 12b2 and the first laminated sheet 11 are integrated by thermosetting the adhesive EP (FIG. 7 (S21), FIG. 10). The wiring pattern made of the outermost conductor foil 12e is covered with a solder resist sr made of heat-resistant resin ink, etc., in order to prevent problems due to the adhesion of the wiring pattern of scrap metal such as solder to the electronic parts. (FIG. 7 (S22), FIG. 10).

  Here, the second conductive paste 12p has a configuration in which a thermosetting epoxy adhesive is mixed as a binder 12ep with the second metal particles 12me that are melted by heating. Is the melting point (Tk2) of the second metal particles 12me the same as the gelling temperature (Tp2) of the binder 12ep in order to facilitate the formation of metal bonds between the metal particles when the second metal particles 12me melt? A low temperature is set (Tk2 ≦ Tp2). Further, the second conductive paste 12p has a gelation temperature of the adhesive layer EP so that, when the second metal particles 12me are melted, the via shape is maintained to prevent the bleeding. Curing is performed at a temperature lower than (Sp). Specifically, the gelation temperature (Sp) of the adhesive layer EP is set to 180 ° C. to 200 ° C., and the gelation temperature (Tp2) of the binder 12ep of the second conductive paste 12p is set to 160 ° C. to 170 ° C. In addition, the second metal particles 12me may be tin (Sn), silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), or a plurality of these alloys. It is a mixture containing different metal particles. The gelling temperature (Tp2) of the binder 12ep is 160 ° C. to 170 ° C., and the melting temperature (Tk2) of the second metal particles 12me is equal to or lower by about 10 ° C. than the gelling temperature (Tp2) of the binder 11ep. It is set as 150 to 160 degreeC which is (Tk2 <= Tp2). Here, the melting temperature (Tk2) of the second metal particles 12me refers to the melting point of metal particles made of a metal having the lowest melting point among the plurality of different metal particles. The elastic modulus (Y2) of the second resin substrate 12a at the gelation temperature (Tp2) of the binder 12ep of the second conductive paste 12p is 0.1 GPa or more (Y2 ≧ 0.1 GPa). Heating by the heating / pressurizing means K1, K2 at the time of gelation of the binder 12ep of the second conductive paste 12p is about 170 ° C. By heating the second conductive paste 12p, at least a part of the low melting point metal particles contained in the second conductive paste 12p at 160 ° C. to 170 ° C. (the metal having the lowest melting point among the plurality of different metal particles) The metal pattern) is melted and diffused with the other refractory metal particles to form an alloy, and the wiring pattern consisting of one conductor foil 12e provided on the single-sided copper-clad plate 12b (12a) and the other conductor foil 11e. The adhesive layer is electrically connected to the wiring pattern, and the binder 12ep contained in the conductive paste 12p is thermally cured and heated at a heating temperature of about 200 ° C. by the heating / pressurizing means K1 and K2. The EP is thermally cured, and the single-sided copper-clad plate 12b (12a) and the first laminated sheet 11 are integrated.

  As described above, when the gelation temperature (Tp2) of the binder 12ep of the second conductive paste 12p is set to 160 ° C. to 170 ° C., the gelation temperature (Tp1) of the binder 11ep of the first conductive paste 11p described above. The gelation temperature is lower than 190 ° C to 200 ° C. Here, in the present embodiment, the gelation temperature (Sp) of the adhesive layer EP is 180 ° C. to 200 ° C., and the gelation temperature (Tp1) of the binder 11ep of the first conductive paste 11p is 190 ° C. to 200 ° C. Although it is set to ° C., not all of these conditions must be satisfied. The heating / pressurization of the first resin base material 11a, 11b, 11c is performed in the previous step separately from the subsequent heating / pressurization of the second resin base material (prepreg) 12b1 (12a1). is there. The heating temperature of the first laminated sheet by the heating / pressurizing means K1, K2 is two-stage heating of about 200 ° C. and about 300 ° C., and the second laminated sheet is heated by the heating / pressurizing means K1, K2. The temperature is about 170 ° C., and the heating temperature by the heating / pressurizing means K1, K2 between the first and second laminated sheets and the adhesive layer performed thereafter is about 200 ° C. Is heated at a low temperature. This is because, in the present embodiment, the central flexible portion FL is set to a temperature at which the gelation temperature and the heat deformation temperature are higher than the rigid portions R1 and R2 arranged on both sides thereof.

  Therefore, after the first resin base materials 11a, 11b, and 11c that are located on the inner side are heated and pressurized, the second resin base material (the prepreg) that is located on the outer side (upper and lower sides). ) When 12b1 (12a1) is thermocompression-bonded by the heating / pressurizing means K1 and K2, the adhesive layer EP remains even if the binder 12ep of the second conductive paste 12p on the outer side (upper and lower sides) melts or softens. By obtaining a state that does not melt or soften, the via shape of the second conductive paste 12p is maintained, and a situation in which bleeding occurs is prevented. Moreover, the elastic modulus (Y1) of the first resin substrate 11a at the gelation temperature (Tp1) of the binder 11ep of the first conductive paste 11p is 0.1 GPa or more (Y1 ≧ 0.1 GPa), and Since the elastic modulus (Y2) of the second resin substrate 12a at the gelation temperature (Tp2) of the binder 12ep of the second conductive paste 12p is 0.1 GPa or more (Y2 ≧ 0.1 GPa), the first In the step of curing the conductive paste 11p, the first laminated sheet 11 is prevented from being thermally deformed, and the via shape of the first conductive paste 11p for interlayer connection filled in the via hole 11h and cured is deformed. hard. Further, in the step of curing the second conductive paste 12p, a situation in which the second laminated sheet 12 is thermally deformed is prevented, and the vias of the second conductive paste 12p for interlayer connection filled in the via holes 12h and cured. The shape is difficult to deform.

  The via holes 11h and 12h have various shapes such as a cylindrical shape, a conical shape, and a square shape. The via holes 11h and 12h can be easily formed by laser irradiation or the like on the first resin base material 11c (11a and 11b) and the second resin base material 12b (12a).

  When the via holes 11h and 12h are formed by a laser or the like, residues (smear) associated with the processing of the conductor foils 11e and 12e and the resin base materials 11a, 11b, 11c, 12a, and 12b are near the entrances of the via holes 11h and 12h. In some cases, the bottom of the via hole may be formed, and a desmear process for removing the smear mechanically or chemically may be added before the filling process of the conductive pastes 11p and 12p.

  As described above, the present invention is not limited to the embodiment described above. For example, here, the laminated sheet 1 is formed by superposing a thermoplastic resin film such as a liquid crystal polymer and thermocompression bonding the adhesive surfaces, but the thermosetting resin film may be adhered via an adhesive. The flex portion FL may be positioned between the rigid portions R1 and R2, or the flex portion FL may be protruded from one side or both sides of the rigid portion R1. Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

It is a cross-sectional schematic diagram which shows the lamination sheet for multilayer printed wiring board manufacture of 1st Embodiment to which this invention is applied. It is a figure explaining the thermocompression bonding state of the comparative example 1 compared with the thermocompression bonding state of the said 1st Embodiment, (a) is the cross-sectional schematic diagram, (b) is the figure which image | photographed the photograph. . It is a figure explaining the thermocompression bonding state of the comparative example 2 compared with the thermocompression bonding state of the said 1st Embodiment, (a) is the cross-sectional schematic diagram, (b) is the figure which image | photographed the photograph. . It is a figure explaining the thermocompression bonding state of the said 1st Embodiment, (a) is the cross-sectional schematic diagram, (b) is the photographed figure. It is a cross-sectional schematic diagram which shows the lamination sheet for multilayer printed wiring board manufacture of 2nd Embodiment to which this invention is applied. It is a perspective view which shows typically the multilayer printed wiring board of the said 2nd Embodiment. It is a process flowchart which shows the manufacturing process sequence of the multilayer printed wiring board of the said 2nd Embodiment. It is a cross-sectional schematic diagram which shows the manufacturing process of the flexible wiring board of the said 2nd Embodiment. It is a cross-sectional schematic diagram which shows the manufacturing process of the rigid wiring board of the said 2nd Embodiment. It is a cross-sectional schematic diagram which shows the manufacturing process of the said 2nd Embodiment. It is a graph which shows typically the relationship between the gelling temperature of the adhesive bond layer of 1st Embodiment to which this invention is applied, the gelling temperature of the binder of an electrically conductive paste, and melting | fusing point of a metal particle.

Explanation of symbols

Z1, Z2 Multilayer printed wiring board laminated sheet (multilayer printed wiring board),
1, 11, 1a, 11a, 1b, 11b, 11c
Resin base material, (first resin base material, first laminated sheet),
1e, 11e, 2e, 12e conductive foil,
12a1, 12a2, 12b1, 12b2 second resin base material (single-sided copper-clad plate, prepreg, second laminated sheet),
1p, 11p1, 12p, 11p, 12p conductive paste (first conductive paste, second conductive paste),
1ep, 11ep, 2ep, 12ep Conductive paste binder (first binder, second binder)
1me, 11me metal particles (first metal particles),
2me, 12me second metal particles,
1mp, 11mp binder (first binder),
2mp, 12mp second binder,
1h, 2h, 11h, 12h Via hole (via hole, via),
EP adhesive (adhesive layer),
sr solder resist,
FL flexible part,
R1, R2 rigid part,
K1, K2 Heating / pressurizing means

Claims (5)

A multilayer printed wiring board in which a resin base material on which a wiring pattern is formed by a conductor foil is overlaid and thermocompression bonded by a heating / pressurizing means, and a first conductive paste for interlayer connection filled in a via hole and cured A first resin base material, a second resin base material having a second conductive paste for interlayer connection filled in a via hole and cured, and the first resin base material and the second resin base material are bonded together And the adhesive layer is made of a thermosetting adhesive, and both the first conductive paste and the second conductive paste have a thermosetting adhesive as a binder, The second conductive paste binder has a gelation temperature (Tp2) lower than the first conductive paste binder gelation temperature (Tp1) (Tp2 <Tp1), and the second conductive paste Ba The gelation temperature (Tp2) of the solder is configured as a temperature (Tp2 <Sp) lower than the gelation temperature (Sp) of the adhesive layer, and the first conductive paste contains first metal particles, The melting point (Tk1) of the first metal particles is configured to be equal to or lower than the gelation temperature (Tp1) of the first binder (Tk1 ≦ Tp1), and the second conductive paste is the second metal particles. The melting point (Tk2) of the second metal particles is equal to or lower than the gelation temperature (Tp2) of the second binder (Tk2 ≦ Tp2), and the second metal particles The multilayer printed wiring board is characterized in that the melting point (Tk2) is lower than the melting point (Tk1) of the first metal particles (Tk2 <Tk1) . The first conductive paste and the second conductive paste are tin (Sn), silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), or an alloy thereof. multilayer printed wiring board according to claim 1, wherein the a mixture comprising a plurality of dissimilar metal particles selected from. The elastic modulus (Y1) of the first resin substrate at the gelation temperature (Tp1) of the binder of the first conductive paste is configured to be 0.1 GPa or more (Y1 ≧ 0.1 GPa), and the first The elastic modulus (Y2) of the second resin base material at the gelation temperature (Tp2) of the binder of the conductive paste 2 is configured to be 0.1 GPa or more (Y2 ≧ 0.1 GPa). The multilayer printed wiring board according to claim 1 or 2 . The present invention relates to a method for manufacturing a multilayer printed wiring board in which a resin substrate on which a wiring pattern is formed by a conductor foil is superposed and thermocompression bonded by a heating / pressurizing means, and has a first conductive paste for interlayer connection that fills and cures via holes. In order to bond the first resin base material, the second resin base material having the second conductive paste for interlayer connection that fills and cures the via hole, and the first resin base material and the second resin base material When forming a laminated sheet having the adhesive layer, the adhesive layer is a thermosetting adhesive, and the first conductive paste and the second conductive paste are both thermosetting adhesives. The binder has a gelation temperature (Tp2) of the second conductive paste that is lower than the gelation temperature (Tp1) of the binder of the first conductive paste (Tp2 <Tp1). The conductive paste binder has a gelation temperature (Tp2) lower than the adhesive layer gelation temperature (Sp) (Tp2 <Sp), and the first conductive paste contains the first metal particles. The melting point (Tk1) of the first metal particles is configured to be equal to or lower than the gelation temperature (Tp1) of the first binder (Tk1 ≦ Tp1). The melting point (Tk2) of the second metal particles is configured to be equal to or lower than the gelation temperature (Tp2) of the second binder (Tk2 ≦ Tp2). A multilayer printed wiring board characterized in that the melting point (Tk2) of the metal particles is configured to be lower than the melting point (Tk1) of the first metal particles (Tk2 <Tk1) and integrated by the thermocompression bonding. How to make . The first conductive paste and the second conductive paste are respectively tin (Sn), silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), or an alloy thereof. The method for producing a multilayer printed wiring board according to claim 4, wherein the mixture comprises a plurality of different metal particles selected from the group consisting of:

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