TW201208514A - Multilayered printed circuit board and method for manufacturing the same - Google Patents

Abstract

A multilayer printed wiring board 1 is provided with a first conductive layer 12 arranged on a first substrate 11, a second conductive layer 22 arranged on a second substrate 21, and a through hole 2 penetrating the second substrate 21 and using the first conductive layer 12 as a bottom face. The through hole 2 is filled with a conductive paste 3 comprising a plate-shaped filler serving as a conductive filler.

Description

201208514 VI. [Technical Field] The present invention relates to a multilayer printed wiring board and a method of manufacturing the same, in which a conductive paste is provided in a through hole provided in a substrate for connecting to a plurality of substrates. a conductive layer of each substrate. [Prior Art] In recent years, in the field of electronic equipment, with the increase in density or miniaturization of electronic equipment, printed wiring boards have been used in various applications. Among them, a multilayer printed wiring board in which a plurality of substrates are laminated to form a large number of wirings has been known. The multilayer printed wiring board includes a first conductive layer provided on the first substrate and a second conductive layer provided on the second substrate. The first conductive layer and the second conductive layer are electrically connected by providing a through hole in the second substrate and plating the substrate on which the through hole is provided. However, when the substrate is plated, if the desmear of the wall surface or the bottom surface of the through hole is insufficient, there is a problem of electrical connection reliability, and the fine pitch of the wiring pattern cannot be obtained. Further, since a plating mask must be produced, the cost cannot be reduced, and since the plating waste liquid is generated, the environmental burden is also large. For example, Patent Document 1 discloses a method of producing a multilayer printed wiring board by laminating the first laminated body and the second laminated body, respectively. In this document, in order to electrically connect the first conductive layer and the second conductive layer, a conductive paste is applied to the through hole penetrating through the second substrate instead of plating.

-3- S 201208514 Specifically, first, as shown in FIGS. 7(a) and 7(b), after the first substrate hi on which the first conductive layer 112 is provided is prepared, the first substrate 111 is connected to the first conductive layer. The adhesive layer 160 is provided on the surface on the opposite side of the layer 112. Next, as shown in FIGS. 7(c) and (d), after the predetermined conductive pattern is formed on the first conductive layer 112, the cover film 130 formed by the adhesive layer 131 and the resin film 132 is bonded to the first layer. 1 conductive layer 1 12 . Next, as shown in FIGS. 7(e) and (f), a masking tape 170 is formed on the adhesive layer 160, and then a through hole 104 is formed through the first substrate 1 1 1 . Next, as shown in Figs. 7(g) and 00, after the conductive paste 105 is filled in the through hole 104, the masking tape 170 is peeled off, whereby the first layered body is produced. Further, as shown in FIGS. 8(a) and 8(b), after the second substrate 121 on which the second conductive layer 122 is provided is prepared, the surface of the second substrate 121 opposite to the second conductive layer 1 22 is formed on the second substrate 121. An adhesive layer 1 60 is provided. Next, as shown in FIGS. 8(c), (d), and (e), after the predetermined conductive pattern is formed on the second conductive layer 122, the masking tape 170 is formed on the adhesive layer 160, and the formation of the second through-layer is performed. The through hole 1 〇 2 of the substrate 12 1 . Then, as shown in Fig. 8 (f) and (g), after the conductive paste 103 is filled in the through hole 102, the masking tape 170 is peeled off, whereby the second layered body is produced. Further, as shown in Fig. 9 (a) and (b), after the first layered body and the second layered body are aligned, the first layered body and the second layered body and the other electrically conductive layer .113 are laminated. Next, as shown in FIGS. 9(c) and (d), after the predetermined wiring pattern is formed on the other conductive layer 113 as the outermost layer, the cover film formed by the adhesive layer 141 and the resin film 142 is formed. 140 attached to another

S -4- 201208514 - a conductive layer 113. Further, the cover film 150 formed of the adhesive layer 151 and the resin film 152 is bonded to the second conductive layer 122 to manufacture the multilayer printed wiring board 101. However, in the multilayer printed wiring board described in the patent document, as shown in Fig. 9(a), two substrates are laminated after the conductive paste is filled in the through hole. Therefore, it is difficult to align the conductive paste 103 to face the opening of the cover film 130. Therefore, a method of filling the conductive paste after laminating a plurality of substrates and forming the through holes can also be considered. However, in this method, the through hole becomes long, so that the conductive paste cannot be sufficiently filled in the through hole. Therefore, the adhesive covering the cover film of the through hole is melted and mixed with the conductive paste and enters the through hole, and sufficient reliability cannot be obtained in the electrical connection between the first conductive layer and the second conductive layer. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION The object of the present invention is to provide a reliable improvement in electrically connecting a first conductive layer and a second conductive layer by a conductive paste. Multi-layer printed wiring board and its manufacturing method. Means for Solving the Problem In order to solve the above-described problems, according to a first aspect of the present invention, a multilayer printed wiring board includes: a first conductive layer provided on a first substrate; and a second conductive layer is disposed on The second substrate; the through hole penetrates the second substrate and the second conductive layer of -5,085,085, and has a bottom surface formed of the first conductive layer; and the cover film is provided to cover the through hole. A conductive paste containing a flat material as a conductive material is filled in the through hole. According to this configuration, the conductive paste filled in the through holes contains a flat plate material as a conductive material. This conductive paste exhibits lower fluidity than the conventional conductive paste, and therefore, it is possible to prevent the material constituting the adhesive layer of the cover film from being mixed with the conductive paste and entering the through hole. In this way, the conductive paste filled in the through hole can be reliably electrically connected to the first conductive layer located on the bottom surface of the through hole. Therefore, the reliability of electrically connecting the first conductive layer and the second conductive layer by the conductive paste can be improved. In the multilayer printed wiring board, the ratio of the plate-like material to the entire conductive material is preferably 6 7 to 100% by mass. According to this configuration, the flowability lower than that of the conventional conductive paste is exhibited, and therefore, the material constituting the adhesive layer of the cover film can be further suppressed from entering the through hole by mixing with the conductive paste. As a result, the reliability of electrically connecting the first conductive layer and the second conductive layer by the conductive paste can be further improved. In the multilayer printed wiring board, the diameter of the through hole is preferably 3 Ο μ m or more and 20 μm or less. According to this configuration, since the diameter of the through hole is 200 μm or less, the pitch of the second substrate can be reduced by reducing the diameter of the through hole. Further, since the diameter of the through hole is 30 μm or more, the conductive paste can be easily filled in the through hole.

-6- S 201208514 In the multilayer printed wiring board, the conductive paste filled in the through hole is continuously provided on the second conductive layer, and the diameter of the conductive paste provided on the second conductive layer and the diameter of the through hole The difference is preferably 20 μm or more and 200 μm or less. According to this configuration, the difference between the diameter of the conductive paste on the second conductive layer and the diameter of the through hole is 200 μm or less, thereby reducing the conductive paste on the second conductive layer. The diameter can be made to be fine pitched on the second substrate. Further, since the difference between the diameter of the conductive paste on the second conductive layer and the diameter of the through hole is 20 μm or more, the conductive paste which has been filled in the through hole and the second conductive provided with the conductive paste can also be used. The layers are indeed connected. In order to solve the above problems, according to a first aspect of the present invention, a method of manufacturing a multilayer printed wiring board comprising: a first conductive layer ′ is disposed on a first substrate; and a second conductive layer is provided The second substrate and the through hole are formed through the second substrate and have a bottom surface formed of the first conductive layer. The manufacturing method includes: a printing process for printing a conductive paste containing a conductive material as a conductive paste on a second substrate provided with a through hole; and a second substrate printed with a conductive paste to cover the conductive substrate The cover film is provided in a manner of a paste, and a pressurization process for pressurizing the second substrate is performed on the cover film. In the pressurizing process, the conductive paste is filled in the through hole by being pressed together with the cover film. According to this configuration, the conductive paste containing the flat material as the conductive material is printed on the second substrate and then filled in the through hole. Since the conductive paste exhibits lower fluidity than the conventional conductive paste, it is possible to suppress the material of the adhesive layer of the cover film from being mixed with the conductive paste and entering the through hole. As a result, the conductive paste which has been filled in the through holes can be reliably connected to the first conductive layer which is the bottom surface of the through hole. Therefore, the reliability of electrically connecting the first conductive layer and the second conductive layer by the conductive paste can be improved. Further, in the process of pressurizing the cover film on the second substrate, the cover film is pressurized with the conductive paste to fill the through hole. Therefore, in addition to the above-described addition process, it is not necessary to use other processes for filling the conductive paste into the through holes, and the number of manufacturing processes can be reduced. [Embodiment] The present invention is directed to an embodiment in which two printed wiring boards having flexibility are laminated, and the multilayer printed wiring board of the present invention will be described with reference to Figs. 1 to 6 . As shown in Fig. 1, the multilayer printed wiring board 1 includes a first printed wiring board 1 〇 'second printed wiring board 20 ' covering the first printed wiring board 10 with the cover films 30 and 40 and covering the second printed wiring board The cover film 50 of 20 and the adhesive layer 60 for bonding the respective printed wiring boards 1 and 20 are bonded. The first printed wiring board 1 is a double-sided printed wiring board on which wiring patterns are printed on both sides. The first printed wiring board includes a first conductive layer 12' having a first substrate formed on one side surface of the first substrate 11, and another conductive layer 13 formed on the other side surface of the first substrate 11. The second printed wiring board 20 is a single-sided printed wiring board in which a wiring pattern is printed on only one side. The second printed wiring board 20 includes a second substrate 21 and a second conductive layer 22 formed on one side surface of the second substrate 21. +

-8-S • 201208514 Each of the substrates 11 and 21 is made of a resin material excellent in flexibility. As the resin for forming the substrates 11 and 21, for example, polyimide, polyester, or the like is used as a general-purpose resin for a printed wiring board, and particularly suitable from the viewpoint of high heat resistance in addition to flexibility. For example, a polyamine-based resin or a polyimine-based resin such as polyimine or polyamidimide. The thickness of each of the substrates 11 and 21 is 10 μη or more and 50 μm or less. As each of the conductive layers 12, 13, and 22, a metal such as copper is used. For example, each of the conductive layers 12, 13, 22 having a predetermined wiring pattern is formed by etching a metal foil such as a copper foil. It is also possible to form a wiring pattern by a semi-additive method and by plating. The thickness of each of the conductive layers 12, 13, and 22 is 5 μm or more and 50 μm or less. The cover film 30 covers the insulating layer of the first conductive layer 12. The cover film 30 is composed of an adhesive layer 31 laminated on the first conductive layer 12 and a resin film 32 laminated on the adhesive layer 31. The subsequent agent layer 31 is then laminated on one side surface of the first substrate 11 and the first conductive layer 12. Thereby, the cover film 30 is provided so as to cover the first conductive layer 12 on the first printed wiring board 10. The cover film 40 is used to cover the insulating layer of the other conductive layer 13. The cover film 40 is composed of an adhesive layer 41 laminated on the other conductive layer 13 and a resin film 42 laminated on the adhesive layer 41. The subsequent agent layer 41 is then laminated on the other side surface of the first substrate 11 and the other conductive layer 13. Thereby, the cover film 40 is disposed to cover the other conductive layer 13 on the first printed wiring board 1?.

-9 - S 201208514 The cover film 50 is used to cover the insulating layer of the second conductive layer 22. The film 50 is composed of an adhesive layer 51 laminated on the second conductive layer 22 and a resin film 52 on the build-up layer 51. The subsequent layer 51 is then laminated on one side surface of the second substrate 21 and the second conductive layer 22. Thereby, the film 50 is provided so as to cover the second conductive layer on the second printed wiring board 20 as an adhesive constituting each of the adhesive layers 31, 41, and 51, and is excellent in heat resistance or heat resistance, for example. Various resin-based adhesives such as nylon, epoxy resin butyral resin, and acrylic resin are used. For each of the resin films 32, 42, and 52, the same material as the resin material constituting each of the substrates 21 can be used. Each of the cover films 30, 40, and 50 is ΙΟμηη or more and ΙΟΟμηη or less. The adhesive layer 60 is composed of an interlayer adhesive for adhering the first printed wiring board 10 and the second wiring board 20. The adhesive layer 60 is formed in a film shape and is disposed between the first printed wiring board 1 〇 and the second printing package 20. The adhesive layer 60 is provided between the film 30 on the first printed wiring board 10 and the second printed wiring board 20. The subsequent layer 60 is followed by the resin film 32 covering the 30 and the second substrate of the second printed wiring board 20. As the adhesive constituting the adhesive layer 60, the same adhesive as the adhesive for the adhesive layers 31, 41, and 51 can be used. Then, the thickness of 60 is ΙΟμηη or more and ΙΟΟμηη or less. The multilayer printed wiring board 1 is provided with the conductive material 3 which is filled in the through hole 2, and the conductive paste 5 which is filled in the through hole 4. The conductive paste 3 has a -10 0 - cover layer and a cover layer of 22 〇 soft type, and 11' thickness is printed with a wire cover cover film 21 to form each layer of a layer paste 1201208514 electric layer 12 and second conductive The layer 22 is electrically connected, and the conductive paste 5 electrically connects the first conductive layer 12 to the other conductive layer 13 . The through hole 2 is provided in a bottomed via which is not plated on the second printed wiring board 20. The through hole 2 penetrates the second conductive layer 22 and the adhesive layer 60 of the second substrate 21'. The bottom surface of the through hole 2 is formed by the first conductive layer 12, and the wall surface of the through hole 2 is formed by the cover film 30' adhesive layer 60, the second substrate 21, and the second conductive layer 22. The diameter D1 of the through hole 2 is preferably 30 μm or more and 200 μm or less. The shape of the through hole 2 may be, for example, an elliptical shape or a cross-sectional polygonal shape in addition to a circular shape. In the case of a circular shape, the diameter D1 of the through hole 2 is the maximum length of the opening. The through hole 4 is provided in the bottomed path of the first printed wiring board 1 which is not plated. The through hole 4 penetrates through the first substrate 11 and the other conductive layer 13. The bottom surface of the through hole 4 is formed by the first conductive layer 12, and the wall surface of the through hole 4 is formed by the first substrate 11 and the other conductive layer 13. The diameter of the through hole 4 is also 30 μm or more and 200 μm or less in the same manner as the diameter D1 of the through hole 2. As the conductive pastes 3 and 5, a paste in which a conductive material such as metal particles is dispersed in a binder resin can be used. Examples of the metal particles include silver, platinum, gold, copper, nickel, and palladium. In order to exhibit excellent conductivity, silver powder, silver coated copper powder, or the like is preferable. The binder resin may, for example, be an epoxy resin, a phenol resin, a polyester resin, a polyurethane resin, an acrylic resin, a melamine resin, a polyimine resin, and a polyamidimide. Resin, etc. Among these resins, a thermosetting resin is preferred from the viewpoint of improving the heat resistance of the conductive 201208514 paste, and in the present embodiment, epoxy resin is preferred. Examples of the epoxy resin include a copolymer of a bisphenol A type, a F type, an s type, an AD type, or a bisphenol a type and a bisphenol p type, or a naphthalene type epoxy resin. 'Phenolic type epoxy resin, biphenyl type epoxy resin, one ring penta thin type epoxy resin, and the like. A phenoxy resin which is a molecular weight epoxy resin can also be used. The binder resin can be used by dissolving in a solvent. The solvent may, for example, be an organic solvent such as an ester, an ether, a ketone, an ether ester, an alcohol, a hydrocarbon or an amine. In order to perform the screen printing of the conductive pastes 3 and 5 in the through holes 2 and 4 as a solvent, it is preferable to use a high boiling point solvent having excellent printability. More specifically, carbitol acetate is used. Or butyl carbitol acetate is preferred. These solvents can also be used in combination. These materials are mixed and dispersed by three rolls, a rotary stirring defoaming machine or the like to form a uniform state, thereby producing conductive pastes 3 and 5. As described above, the multilayer printed wiring board 1 of the present invention includes the first conductive layer 12 provided on the first substrate 11, the second conductive layer 22 provided on the second substrate 21, and the first conductive layer 12 and the first conductive layer 12 2, the through hole 2 electrically connected to the conductive layer 22, and the cover film 50 covering the through hole 2. The through hole 2 penetrates the second substrate 21 and the second conductive layer 22, and the bottom surface of the through hole 2 is formed by the first conductive layer 12. The conductive paste 3 containing a flat plate material as a conductive material is filled in the through hole 2. As shown in Fig. 2, the flat-shaped (scale-like) conductive 塡-12- 3 201208514 4 is expected to have three dimensions orthogonal to each other (the longitudinal direction, the width direction, and the Ιϊ respectively have dimensions. Among them, one direction is made ( The other two directions (length direction and width direction) of the thickness direction are at most 2 or less. The conductive paste 3 contains a flat plate as a conductive material, which shows a low fluidity of a conventional conductive paste. According to this 3', the material constituting the adhesive layer 51 constituting the cover film 50 can be prevented from entering the through hole 2. The ratio of the whole material to the conductive material is 6 7 to 100% by mass. For example, the conductive paste 3 exhibits lower fluidity. Therefore, the material of the adhesive layer 51 can be mixed with the conductive paste 3 and enter the conductive paste 3 as a conductive material. For example, a flat material having a particle diameter of 15 μm or less is contained, and the enthalpy of the through-hole 2 and the enthalpy density in the paste 3 can be obtained by accumulating 99% or less in a state of 15 μm or less. Conductivity with high conductivity | X% cumulative particle size (X is arbitrary It is a particle diameter of X% in the measurement of the particle size distribution, and it can be measured by a particle size distribution measuring device [Microtrac particle size distribution measuring device 93 20HRA (X-measurement). The flat material of the conductive material is averaged. The particle size (that is, the product particle diameter) is preferably 1 μm or more and 4 μm or less. In the state in which the average particle is in such a range, a highly conductive paste can be obtained. -13- ί directional) The size becomes large 1 塡 , 因 因 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电 导电, 50 % of the conductivity is limited to the conductivity of the 201208514 conductive crucible, the specific surface area per unit mass of surface area is, for example, 1.3 m 2 / g, and the tap density is, for example, 2.9 g / cm 3 . The knocking density is a density measured by a density measuring device (manufactured by Shimadzu Corporation, ACCUPY C II 1340). An alloy layer of silver and copper is formed on the surface of the flat material. Therefore, the flat plate material which is pressurized at a predetermined temperature and is filled in the conductive paste 3 of the through hole 2 is fused to a part of the first conductive layer 12 and the second conductive layer 22 to be connected. Such a flat material is obtained, for example, by heating a surface of a metal powder having a copper layer on the surface thereof and then heating it in a wet reducing atmosphere. As the conductive material contained in the conductive paste 3, a spherical material can be used in addition to the flat material. As the spherical material, there are a non-completely spherical material, a material having a plurality of irregularities on the surface, and a material having an elliptical cross section. The average particle diameter of the spherical grave is 1 〇 μηι. The following is better. The fluidity of the conductive paste 3 is improved by containing a spherical material. The conductive paste 3 filled in the perforation 2 is continuously provided on the second conductive layer 22. The difference between the diameter of the conductive paste 3 which is placed on the second conductive layer 22 and the diameter D1 of the through hole 2 is 2〇. Ιιη or more, 2〇〇_ or less. Next, a method of manufacturing a multi-layer printed wiring board as shown in the drawings will be described with reference to Figs. 3(a) to 5(4). Fig. 3 (4) to (4) are cross-sectional views for explaining a method of manufacturing the i-th laminated body. Fig. 4 (4) and (8) are cross-sectional views for explaining a method of manufacturing the second laminate. Fig. 5 (4) to (d) are cross-sectional views for explaining a method of manufacturing a multilayer printed wiring board by using a first laminate and a second laminate to produce a multilayer printed wiring board.

'1 4_ S 201208514 As shown in Fig. 3(a), in order to manufacture the first laminate, the first substrate 11 provided with the respective conductive layers 12 and 13 on both sides is prepared. Although the conductive layers 12 and 13 may be provided on the first substrate 11 through an adhesive layer (not shown), it is preferable that the conductive layers 12 are not transmitted through the adhesive layer in consideration of flexibility and flexibility. And 13 are provided on the first substrate 11. Next, as shown in FIG. 3(b), after the first conductive layer 12 is shielded, a predetermined wiring pattern is formed on the first conductive layer 12 by well-known etching such as chemical etching (for example, wet etching). Next, as shown in FIG. 3(c), the adhesive layer 31 of the cover film 30 is placed on the side surface of the first substrate 11 and the first conductive layer 12. Thereby, the cover film 30 is placed on the first printed wiring board 10 to complete the first laminated body. Further, as shown in Fig. 4(a), in order to manufacture the second layered body, the second substrate 21 on which the second conductive layer 22 is provided on one side is prepared. Although the second conductive layer 22 may be provided on the second substrate 2 1 through an adhesive layer (not shown), it is preferable that the second conductive layer is not transmitted through the adhesive layer and the flexibility. 22 is provided on the second substrate 21. Next, as shown in FIG. 4(b), the adhesive layer 60 is bonded to the other side surface of the second substrate 21, that is, the surface opposite to the second conductive layer 22, to complete the second laminated body. Each of the laminates thus produced was laminated in the manner as shown in Fig. 5(a). That is, the adhesive film 40 provided on the second substrate 21 is adhered to the resin film 32 of the cover film 30. Next, the second conductive layer which becomes the outermost layer is shielded from the other conductive layer 13. Then, using wet etching, etc.

-15-S 201208514% etching method forms a predetermined wiring pattern on the second conductive layer 22 and the other conductive layer 13, respectively. Next, as shown in FIG. 5(b), a CO 2 laser (YAG laser) or a polyimide etchant or the like is used for the second conductive layer 22, the second substrate 21, the adhesive layer 60, and the cover film 30. Make holes. Thereby, the through hole 2 is formed. Similarly, another conductive layer 13 is opened to the first substrate 11 to form a through-hole 4 . Next, the residue (smear) remaining in each of the through holes 2, 4 is removed. Specifically, wet slag removal treatment or plasma treatment using alkaline and potassium permanganate is performed to clean each of the through holes 2, 4. Then, as shown in Fig. 5(c), the conductive paste 3 is printed so as to be filled in the through hole 2, and the conductive paste 5 is printed so as to be filled in the through hole 4. In this manner, the conductive paste 3 can be placed in the through hole 2, and the conductive paste 5 can be placed in the through hole 4. As a method of printing the conductive pastes 3 and 5, for example, a screen printing method can be mentioned. In the present embodiment, after the first layered body and the second layered body are laminated (ie, after the first substrate 11 and the second substrate 21 are laminated), the through holes 2 are formed, so that the first substrate 11 and the second substrate can be easily formed. The alignment of the substrate 21. Further, the masking tape 170 used in the method of manufacturing the multilayer printed wiring board 101 is not required. Next, as shown in Fig. 5(d), the adhesive layer 41 of the cover film 4 is next to the other side surface of the first substrate 11, the other conductive layer 13, and the conductive paste 5. Further, the adhesive layer 51 of the cover film 50 is applied to the other side surface of the second substrate 21, the second conductive layer 22, and the conductive paste 3. At this time, the purpose of heating the conductive paste 3 into the long through hole 2 is to heat the cover film 50 at a temperature of 200 ° C while the second base-16-3 201208514 plate 21 is heated. Pressure pressurization of MPa. Thereby, the conductive paste 3 can be pressurized to the through hole 2 together with the cover film 50. In this manner, the multilayer printed wiring board is manufactured by providing the cover films 40 and 50 on the first and second laminated bodies, respectively. According to the present embodiment, the following effects can be obtained. (1) The conductive paste 3 containing a flat material as a conductive material is filled in the through hole 2. Since the conductive paste 3 exhibits lower fluidity than the conventional conductive paste, the material constituting the adhesive layer 51 of the cover film 50 can be prevented from entering the through hole 2 by being mixed with the conductive paste 3. In this manner, the conductive paste 3 that has been filled in the through hole 2 can be surely connected to the first conductive layer 12 that forms the bottom surface of the through hole 2. Therefore, the reliability of electrically connecting the first conductive layer 12 and the second conductive layer 22 by the conductive paste 3 can be improved. (2) The conductivity of the conductive paste 3 is lower than that of the conventional conductive paste, in the case where the ratio of the flat material is 6 7 to 100% by mass with respect to the entire conductive material. As a result, the material constituting the adhesive layer 51 of the cover film 50 can be further suppressed from entering the through hole 2 by being mixed with the conductive paste 3. As a result, the reliability of electrically connecting the first conductive layer 12 and the second conductive layer 22 by the conductive paste 3 can be further improved. (3) The diameter D1 of the through hole 2 is 30 μm or more and 200 μm or less. In other words, the diameter D1 of the through hole 2 is reduced to 200 μm or less, and the pitch of the second substrate 21 can be reduced. Also, to diameter D1 of the through hole 2

S-17 - 201208514 The conductive paste 3 can be easily filled in the through hole 2 even when the temperature is 30 μm or more. (4) The conductive paste 3 filled in the through hole 2 is continuously provided on the second conductive layer 22. Further, the difference between the diameter D2 of the conductive paste 3 provided on the second conductive layer 22 and the diameter D1 of the through hole 2 is 20 μm or more and 200 μm or less. In other words, the diameter D2 of the conductive paste 3 on the second conductive layer 22 is reduced in a state where the difference between the diameter D2 of the conductive paste 3 and the diameter D1 of the through hole 2 is 200 μm or less, and the second substrate 21 can be obtained. Detailing. In the state where the difference between the diameter D2 of the conductive paste 3 and the diameter D1 of the through hole 2 is 20 μm or more, the conductive paste 3 filled in the through hole 2 and the conductive paste 3 can be provided. The second conductive layer 22 is surely connected. (5) A method of manufacturing the multilayer printed wiring board 1 includes: a printing process for printing the conductive paste 3 containing the flat material on the second substrate 2 1 having the through holes 2, and a printing process for printing the conductive paste 3 The substrate 21 is provided with a cover film 50 so as to cover the conductive paste 3, and a pressurization process for pressurizing the cover film 50 against the second substrate 21. In the pressurizing process, the conductive paste 3 and the covering film 50 are pressurized to be filled in the through hole 2. In other words, after the conductive paste 3 containing the flat plate material is printed on the second substrate 21, it is filled in the through hole 2. The conductive paste 3 exhibits a lower fluidity than that of the conventional conductive paste, so that the material constituting the adhesive layer 51 of the cover film 50 can be prevented from entering the through-hole 2 by being mixed with the conductive paste 3. In this manner, the conductive paste 3 that has been filled in the through hole 2 can be surely connected to the first conductive layer 12 that forms the bottom surface of the through hole 2. Therefore, the reliability of electrically connecting the first conductive layer 12 and the second conductive layer 22 by the conductive paste 3 can be improved.

-18-S 201208514 Further, in the pressurizing process in which the cover film 50 pressurizes the second substrate 21, the conductive paste 3 and the cover film 50 are pressurized and filled in the through hole 2. Therefore, in addition to the above-described pressurization process, the other processes for filling the conductive paste 3 into the through-holes 2 are not required, so that the number of processes for the manufacturing process is reduced. As a result, the manufacturing cost of the multilayer printed wiring board 1 can be reduced. The above embodiment can also be modified as follows. It is also possible to mix the latent curing agent to the conductive pastes 3, 5 in which the conductive coating material has been dispersed in the binder resin. As the curing agent, for example, when an epoxy resin is used as the binder resin, an amine compound or an imidazole compound can be used, and when a polyester resin is used as the binder resin, an isocyanate compound can be used. (Embodiment) Hereinafter, the present invention will be described based on the embodiment with reference to Fig. 6. (Preparation of Conductive Paste) (Example 1) When the conductive paste 3 is produced, the epoxy resin as the binder resin is (1) a bisphenol A type epoxy resin having a molecular weight of about 50,000 [Japanese epoxy Resin (manufactured by Resin Co., Ltd., jER (registered trademark) 1256], and (2) an epoxy resin of a double fluorene type F having a molecular weight of about 380 (manufactured by Nippon Epoxy Resin Co., Ltd., jER (registered trademark) 806). As a latent hardener, (3) an imidazole-based latent curing agent (manufactured by Asahi Kasei Chemicals Co., Ltd., Novacure (registered trademark) HX-3941HP) is used. As a conductive material, (4) 99% cumulative particle diameter of about 5. 9 μm and average particle diameter of 2.3 μm, specific surface area of 1.31112/2 and knocking were used.

S -19- 201208514 Flat material with a tightness of 2.9 g / cm3. As the flat material, silver-coated copper powder having a ratio of silver of 2% by mass to the entire flat material was used. As a solvent, butyl carbitol acetate was used, and (1) to (4) were dissolved at a ratio of (1) 72 / (2) 79 / (3) 26 / (4) 1333 by weight. In the solvent. In addition, the conductive paste 3 was produced by dispersing and kneading (three) to (4) using three rollers so that the solid content in the solution was 75% by mass. In Example 1, the ratio of the flat material to the conductive material was 100% by mass. (Example 2) When the conductive paste 3 was produced, "as a conductive material, a spherical material having an average particle diameter of 0.5 μm was used in addition to the flat material." In addition, ' (1) to (5) are dissolved in a solvent at a weight ratio of (1) 72 / (2) 79 / (3) 26 / (4) 8 93 / (5) 440, and Example! the same. In the second embodiment, the ratio of the flat sheet material to the entire conductive material was 66.9 mass%. (Example 3) When the conductive paste 3 was produced, as the conductive material, (5) a spherical material having an average particle diameter of 〇·5 μm was used in addition to the flat material. Further, in addition to (1) to (5), the ratio of (1) 72 / (2) 79 / (3) 26 / (4) 6 6 7 / (5) 6 6 7 is dissolved in a solvent. The same as in the first embodiment. In the third embodiment, the ratio of the flat material to the entire conductive material is 50% by mass. -20 - 201208514 (Example 4) When the conductive paste 3 is produced, it is a flat material except for the conductive material. In addition, (5) a spherical material having an average particle diameter of 0.5 μm was used. Furthermore, (1) to (5) are dissolved in a solvent in a ratio of (1)72 /(2)79 /(3)26 / (4)200 / (5) 1 1 3 3 by weight. Same as the embodiment i. In Example 4, the ratio of the flat material to the entire conductive material was 15 mass%. (Production of Multilayer Printed Wiring Board) The multilayer printed wiring board 1 was produced using the conductive pastes 3 obtained in each of Examples 1 to 4. When the multilayer printed wiring board is produced, first, the first printed wiring board 10 in which the first conductive layer 12 is laminated on the first substrate 11 is prepared. A substrate made of polyimide having a thickness of 25 #m was used as the first substrate 11, and a copper foil having a thickness of 18 μm was used as the first conductive layer 12. Next, a wiring pattern is formed in the first conductive layer 12 so that the through holes 2 formed in the subsequent process are connected by a daisy chain structure. Then, a cover film 30 composed of the adhesive layer 31 and the resin film 32 is provided on the first printed wiring board 1 to form a first laminated body. The thickness of the cover film 30 was 27 μm. The thickness of the adhesive layer 31 constituting the cover film 30 was 15 cm. The thickness of the adhesive layer 32 constituting the cover film 30 is 12 μm. Next, the second printed wiring board 20 in which the second conductive layer 22 is laminated on the second substrate 21 is prepared. A polyimide-based base having a thickness of 25 #m was used -2 1 - 3 201208514 « As a second substrate 21, a copper foil having a thickness of 18/zm was used as the second conductive layer 22. Next, a wiring pattern is formed in the second conductive layer 22 so that the through holes 2 formed in the subsequent process are connected by a daisy chain structure. Next, the adhesive layer 60 is bonded to the second substrate 21 to form a second laminate. The thickness of the subsequent agent layer 60 is 25#m. Then, the adhesive layer 60 provided on the second substrate 21 is placed next to the resin film 32 of the cover film 30, and the first laminate and the second laminate are laminated. Next, 1,296 through holes 2 penetrating through the second conductive layer 22, the second substrate 21, the subsequent agent layer 60, and the cover film 30 are formed. The 1 296 through holes 2 formed in the second substrate 21 are connected by a daisy chain structure, and are formed such that the diameter D1 of the through hole 2 is 100 #m. Next, the inside of the through hole 2 is cleaned by the slag removal treatment. Next, the conductive paste 3 is printed to fill the through hole 2. The conductive paste 3 is printed on the second conductive layer 22 so that the difference between the diameter D2 of the conductive paste 3 and the diameter D1 of the through hole 2 is 30/zm. Next, a cover film 50 composed of the adhesive layer 51 and the resin film 52 is provided so as to cover the through holes 2. At this time, the conductive paste 3 was pressed against the cover film 50 at a pressurization temperature of 200 ° C and a pressure of 2.5 MPa to pressurize the second substrate 21 . In this way, the conductive paste 22-g 201208514 (measurement of the connection resistance) is filled in the through-hole 2, and the first conductive layer 12 is measured for each of the obtained multilayer printed wiring boards 1 before and after the heat treatment. The electric resistance of the circuit formed by the second conductive layer 22 and the conductive paste 3. Further, the initial resistance of the path including the conductive paste 3 was measured by the 4-terminal method for the multilayer printed wiring board 1 before the heat treatment. Further, with respect to the multilayer printed wiring board 1 after the heat treatment, the resistance after reflow of the circuit including the conductive paste 3 was measured by a four-terminal method. It can be seen that the obtained resistance 値 is the electric resistance of the conductive paste 3 that is filled in the through hole 2, the contact resistance of the first conductive layer 12, the second conductive layer 22, the first conductive layer 12, and the conductive paste 3, and The total contact resistance of the second conductive layer 2 2 and the conductive paste 3 is obtained. The heat treatment in this case is performed by a general reflow profile when electronic parts (electronic parts) are mounted by reflow soldering. In the heat treatment, the multilayer printed wiring board 1 was passed through a reflow furnace having a peak temperature of 260 ° C six times. (Evaluation of connection reliability) Initially, it is shown that the result is a knot, and its degree. The dependency rate can be increased by connecting the resistance of the scoop S to the correction, and the thermal resistance of the post-row welding price is evaluated. For resistance 1 } The electric meter starts from the ratio of m flat material to the total conductive material (% by mass) Initial resistance (Ω) Resistance after reflow (Ω) Resistance increase rate (%) Example 1 1 00 24.8 25.0 1 Example 2 66.9 75.7 76.5 1 Example 3 50 116.1 133.5 15 Example 4 15 790.0 979.6 24 -23- 201208514 The higher the ratio of the flat material to the total amount of the conductive material, the lower the resistance increase rate is obtained from Table 1. And the result of improved connection reliability. In other words, since the conductive paste 3 exhibits lower fluidity than the conventional conductive paste, it is possible to obtain a result that the material of the adhesive layer 51 constituting the cover film 50 is further suppressed from entering the through-hole 2 and the conductive paste 3 is mixed. In particular, the resistance increase rate 丨%' of the embodiment 丨'2 obtained good connection reliability. Therefore, if the ratio of the flat material to the entire conductive material is 67% by mass or more, the material which further suppresses the adhesive layer 5 1 constituting the cover film 5 can be mixed with the conductive paste 3 and enter the through hole. 2 results. (Industrial Applicability) As an inventive example of the present invention, a conductive layer for connecting to each of a plurality of substrates is connected, and a conductive paste is formed in a through hole formed in the substrate. Multilayer printed wiring board and method of manufacturing the same. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a multilayer printed wiring board according to an embodiment of the present invention. Fig. 2 is a view showing an electron micrograph of a conductive paste according to an embodiment of the present invention. 3(a) to 3(c) are cross-sectional views for explaining a method of manufacturing a multilayer printed wiring board according to an embodiment of the present invention. 4(a) and 4(b) are cross-sectional views for explaining a method of manufacturing a multilayer printed wiring board according to an embodiment of the present invention. Fig. 5 (a) to Fig. 5 (d) are cross-sectional views for explaining a method of manufacturing a multilayer printed wiring board according to an embodiment of the present invention.

S-24-201208514 Fig. 6 is a cross-sectional view showing a schematic structure of the multilayer printed wiring board of Examples 1 to 4. Fig. 7 (a) to Fig. 7 (h) are cross-sectional views for explaining a method of manufacturing a conventional multilayer printed wiring board. Figs. 8(a) to 8(g) are cross-sectional views for explaining a method of manufacturing a conventional multilayer printed wiring board. Fig. 9 (a) to Fig. 9 (d) are cross-sectional views for explaining a method of manufacturing a conventional multilayer printed wiring board. [Description of main component symbols] 1 multilayer printed wiring board 2, 4 through holes 3, 5 conductive paste 10 first printed wiring board 11 first substrate 12 first conductive layer 13 conductive layer 20 second printed wiring board 2 1 second Substrate 22 Second conductive layer 30, 40, 50 Cover film 3 1 , 41, 5 1 Subsequent layer 3 2 , 42 , 52 Resin film 60 Subsequent layer S. -25- 201208514 D 1 Diameter 2 of hole 2 D Conductivity The diameter of the paste 3 is 10 1 multilayer printed wiring board 102 - gg - perforation 103 conductive paste 104 - g * perforation 105 conductive paste 111 first substrate 112 first conductive layer 113 conductive layer 12 1 second substrate 122 second conductive layer 13 1 adhesive layer 13 2 resin film 140 cover film 14 1 adhesive layer 142 resin film 15 1 adhesive layer 1 52 resin film 1 60 adhesive layer 1 70 mask tape -26-

Claims (1)

.201208514 VII. Patent Application Range: 1 . A multilayer printed wiring board comprising: a first conductive layer disposed on a first substrate; a second conductive layer disposed on a second substrate; and a through hole extending through the second The substrate and the second conductive layer have a bottom surface formed by the first conductive layer; and the cover film is provided to cover the through hole; and the through hole is filled with conductive 塡A conductive paste of a flat material. 2. The multilayer printed wiring board of claim 1, wherein the ratio of the flat material is 67 to 100% by mass with respect to the entire conductive material. 3. The multilayer printed wiring board according to claim 1 or 2, wherein the diameter of the through hole is 30 μm or more and 200 μm or less. 4. The multilayer printed wiring board according to claim 1 or 2, wherein the conductive paste filled in the through-hole is continuously provided on the second conductive layer, and is provided on the second conductive layer. The difference between the diameter of the conductive paste and the diameter of the through-hole is 20 μm or more and 200 μm or less. A method of manufacturing a multilayer printed wiring board comprising: a first conductive layer provided on a first substrate; a second conductive layer disposed on a second substrate; and a through hole extending through the foregoing The second substrate has a bottom surface formed by the first conductive layer. S-27-201208514 The manufacturing method includes a printing process for the second substrate provided with the through hole, and the printing includes conductivity a conductive paste for the flat material of the dip; and a pressurizing process for providing the cover film on the second substrate on which the conductive paste is printed, and covering the conductive paste, and the cover film is provided on the cover film The second substrate is pressurized; in the pressurizing process, the conductive paste is filled in the through hole by pressurization together with the cover film. -28- S