JP2005251949A - Wiring board and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having the conductor patterns of a plurality of layers which is high in the reliability of inter-layer connection, and to provide a method for manufacturing it. <P>SOLUTION: An insulating base material is formed with a via hole, and the via hole is packed with coat conductive particles having core members made of second metal having a melting point which is higher than a heating temperature at the time of connecting layers and a surface layer made of metal having a conductor pattern and first metal for generating metallic diffusion. Then, the coat conductive particles are heated and pressurized so that the conductive particle lump of the coat conductive particles can be formed, and the metallic diffusion layer of the conductor pattern metal and the first metal is formed so that the conductor patterns of the plurality of layers can be electrically connected by the metallic diffusion layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wiring board having a plurality of conductive patterns and a method for manufacturing the same.

  As a method for manufacturing a wiring board having a plurality of layers of conductor patterns, for example, there is a technique disclosed in Patent Document 1 below. In this technique, a paste including a first metal particle capable of forming an alloy with a metal forming a conductor pattern in a via of a wiring board, and a second metal particle having a melting point higher than a heating temperature at the time of interlayer connection. A wiring board is manufactured by filling and heating and pressing. At that time, the filled paste becomes an integrated conductive composition, and the conductive pattern of the plurality of layers is a metal diffusion layer formed from the metal forming the conductive pattern and the first metal in the conductive composition. It is electrically connected via.

JP 2003-110243 A

  However, in the above technique, the specific gravity and size are different between the metal that forms the conductor pattern, the first metal that causes diffusion, and the second metal that has a melting point higher than the heating temperature at the time of interlayer connection. As shown in FIG. 10, there is a possibility that the two kinds of metal particles 101 (101a and 101b) are not uniformly contained in the via. FIG. 10 shows a cross section of the via hole filled with the first metal particles 101a and the second metal particles 101b. When heating and pressurizing as shown in FIG. 10A, as shown in FIG. 10B. In this case, the metal does not diffuse properly, resulting in poor contact.

  In FIG. 10A, in the region A1, the second metal particle 101b is localized and the first metal particle 101a is less than the appropriate amount, and in the region B1, the first metal particle 101a is localized. In the region C1, the first metal particles 101a are localized not in the vicinity of the conductor pattern but in the middle of the via hole, and the first metal particles 101a are localized. 101a is more than the appropriate amount.

  FIG. 10B shows interlayer connection states in the case of the regions A1, B1, and C1 as regions A2, B2, and C2, respectively, by applying heat and pressure.

  When the amount of the first metal particles 101a causing the metal diffusion is smaller than the appropriate amount as in the state of the region A1, the metal diffusion does not occur, and the conduction with the conductor pattern 103 is the second metal particle as in the state of the region A2. Only the contact 101b results in a decrease in reliability.

  In addition, when the amount of the first metal particles 101a is larger than an appropriate amount as in the state of the region B1, the thickness of the metal diffusion layer of the conductor pattern 103 that contacts the first metal particles 101a as in the state of the region B2 is more than necessary. It becomes thicker. However, since the metal diffusion layer itself is fragile, if a metal diffusion layer thicker than necessary is formed, it becomes difficult to ensure connection reliability.

  Further, when the first metal particles 101a are localized as in the state of the region C1, the first metal particles 101a are melted or aggregated as in the state of the region C2, and the volume is remarkably reduced. However, contact with the conductor pattern may not be obtained, and conduction failure may occur.

  Also, using the first metal particles 101a that cause metal diffusion as large particles contributes to a decrease in conductivity due to a diffusion failure and a decrease in reliability due to voids inside the via. This decrease in conductivity and reliability becomes more serious as the via diameter is reduced by increasing the density of the wiring board.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a wiring board having a high interlayer connection reliability in a wiring board having a plurality of layers of conductor patterns, and a manufacturing method thereof.

  Accordingly, in order to achieve the above-described object, the present invention provides a coated conductive material filled in a via hole provided in an insulating base material in a wiring board having a plurality of conductor patterns on an insulating base material made of a thermoplastic resin. Conductive particle lump and conductor formed by diffusion of conductive particle lump formed by heating and pressurizing particles, coated conductive particle forming conductive particle lump and metal forming conductor pattern A metal diffusion layer electrically connecting the pattern. Here, the coated conductive particles include a core material made of a second metal having a melting point higher than the heating temperature at the time of interlayer connection, a metal forming a conductor pattern, and a surface layer made of a first metal that causes metal diffusion. It is what you have.

  Further, the present invention provides a method for manufacturing a wiring board having a plurality of conductor patterns in an insulating base material made of a thermoplastic resin, wherein a via hole is formed in the insulating base material, and the heating temperature at the time of interlayer connection is higher in the via hole. Coated conductive particles having a core material made of a second metal having a melting point, a metal that forms a conductor pattern, and a surface layer made of a first metal that causes metal diffusion are filled. Then, by heating and pressurizing, a conductive particle lump of the coated conductive particles is formed, and a plurality of conductive patterns are electrically connected by the metal diffusion layer of the conductor pattern metal and the first metal, and the conductive particle lump is formed. The thermoplastic resin is allowed to flow into the gaps and the gaps between the conductive pattern and the conductive particle mass.

  The coated conductive particles, which are interlayer connection materials for connecting a plurality of conductor patterns, are formed by coating the surface of the core material made of the second metal with the metal of the conductor pattern and the first metal that causes metal diffusion. Since the composition is almost the same for each conductive particle, the metal composition in the via hole can be made uniform without being localized. Thereby, an intermetallic compound layer can be formed only in the part which the coated electroconductive particle contacted. In addition, since the first metal is coated, the volume occupied by the first metal is not as large as particles. Therefore, after the interlayer connection is made by metal diffusion, the volume shrinkage hardly occurs even if the heating and pressurization is rapidly performed, so that the generation of voids is small. As a result, via connection reliability can be improved and the efficiency of the heating and pressing process can be improved.

  Further, by providing an intermediate layer made of the third metal on the surface of the second metal serving as the core material, the influence of the first metal forming the surface layer on the second metal serving as the core material can be reduced. It becomes possible. For example, when the first metal diffuses very easily with respect to the second metal, the second metal is coated with a second metal that is difficult to diffuse with the first metal. It becomes difficult for the first metal to diffuse into the metal, and the first metal can be efficiently diffused with the conductive pattern outside the particles and between the conductive particles. Even when it is difficult to coat the first metal directly on the second metal, the first metal can be coated by coating the third metal as the intermediate layer.

  The insulating base material made of a thermoplastic resin has a softening point higher than the melting point of the first metal, and the temperature at the time of heating and pressurizing in the interlayer connection step is equal to or higher than the melting point of the first metal. By controlling the temperature below the softening point, the resin does not soften or flow during metal diffusion between the conductive particle lump and the metal forming the conductive pattern, so that the base resin does not flow into the via. Thereby, since formation of the conductive particle lump in which the coated conductive particles are integrated and formation of the metal diffusion layer between the particles and the conductor pattern are not hindered by the base resin, stable interlayer conduction is obtained. Then, the brittleness of the metal diffusion layer is increased because the strength of the interlayer connection is reinforced by further heating and allowing the resin of the insulating base material to flow into the gap between the conductor pattern and the via filling particles and the gap between the via particles. Will ease and improve reliability.

  In the manufacturing process of the wiring board shown as a specific example of the present invention, the conductive layer coated with the metal that forms the conductive pattern and the metal that causes the metal diffusion is filled in the interlayer connection part that connects the conductive pattern between the layers. Thus, high reliability is obtained for the connection between the conductor patterns.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a method of manufacturing a wiring board according to this embodiment in the order of steps.

  As shown in FIG. 1 (a), a metal foil 1 such as a copper foil roughened on one or both sides, and a thermoplastic resin film 2 of an insulating base, for example, a liquid crystal polymer (LCP) having a thickness of 25 to 100 μm A thermoplastic resin film 2 made of, for example, is attached by heat fusion or adhesion (FIG. 1B), and the metal foil 1 is etched to form a conductor pattern 3 (FIG. 1C).

  Here, the thermoplastic resin film 2 can be fused by a hot press, and is made of a resin having heat resistance necessary for a process of soldering a component to a substrate. Therefore, the thermoplastic resin film 2 includes, for example, a polyether ether ketone (PEEK: melting point 334 ° C.), a polyphenylene sulfide (PPS: melting point 278 ° C.), an amorphous polymer, etc., which is a crystalline polymer, in addition to the liquid crystal polymer. Resins such as certain polyetherimide (PEI) and polyethersulfone (PES) can be used. Moreover, what has electroconductivity, such as silver and nickel other than copper, can be used for the metal foil 1, for example.

  Next, as shown in FIG.1 (d), the conductor pattern 3 was exposed to the bottom by irradiating the carbon dioxide laser to the predetermined position from the conductor pattern 3 side of the thermoplastic resin film 2 of FIG.1 (c). A bottomed via hole 4 is formed. For the formation of the bottomed via hole 4 by laser, laser light such as UV-YAG laser and excimer laser can be used in addition to the carbon dioxide gas laser. If necessary, after the bottomed via hole 4 is formed, the completed via bottom may be desmeared (smear removed). For desmear treatment, chemical desmear using permanganate or the like, or physical desmear using plasma, excimer laser, or the like can be used.

  Next, as shown in FIG. 1 (e), coated conductive particles 5 (interlayer connection material) are filled into the bottomed via hole 4 formed in the base material. Specifically, the coated conductive particles 5 dispersed in an organic solvent and paste-like are printed and filled into the bottomed via hole 4 using a metal mask having an opening aligned with the bottomed via hole 4. After filling, a step of drying the organic solvent may be added. Further, the filling of the bottomed via hole 4 with the paste can be performed by a printing method including the previous screen printing, a dispensing method in which the paste is discharged from a nozzle, or a transfer method. In addition, it is preferable to mask a part other than the via hole with a release film before filling the coated conductive particle powder. Further, it is possible to fill only the coated conductive particles by a spraying method or a vibration method without forming a paste.

  Before filling the coated conductive particles 5, it is preferable to subject the conductor pattern 3 on the bottom surface of the via to soft etching, reduction treatment, or the like. Thereby, solid phase diffusion at the time of interlayer connection described later is performed more satisfactorily. Furthermore, a metal layer that causes metal diffusion with the first metal that is the surface layer of the coated conductive particles 5 and that is not easily oxidized may be formed on the bottom surface of the via subjected to soft etching, reduction treatment, or the like. Thereby, better metal diffusion occurs between the bottom surface of the via and the surface layer of the coated conductive particles 5.

  The coated conductive particles 5 are substantially uniform on the surface of the core material made of the second metal having a melting point higher than the heating temperature at the time of interlayer connection, which will be described later, and the metal that forms the conductor pattern 3 and the first metal that causes metal diffusion. It is a coated one. It is preferable that the first metal includes any one of tin and indium, or a solder made of at least two of tin, silver, copper, zinc, lead, antimony, bismuth, palladium, indium, and gold. . In addition, it is more preferable that solder does not contain lead from an environmental viewpoint. The second metal includes one or more metals among copper, silver, gold, zinc, palladium, and nickel. In addition, when the surface layer made of the first metal is formed on the surface of the core made of the second metal, it is preferable to reduce the surface of the core. This facilitates coating and improves conductivity. The surface layer made of the first metal is formed by vacuum vapor deposition, chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, melting, or the like.

  Moreover, it is preferable that the thermoplastic resin film 2 has a softening point higher than the melting point of the first metal. The softening point indicates a glass transition point for a crystalline polymer, a liquid crystal transition point for a liquid crystal polymer, and a temperature at which fusion occurs when pressure is applied during pressing for an amorphous polymer.

  Next, as shown in FIG. 1F, a plurality of single-sided conductor pattern films (FIG. 1E) in which the conductor pattern 3 is formed on one side and the coated conductive particles 5 are filled in the bottomed via hole 4 are formed. Laminate the sheets. In the present embodiment, the two single-sided conductor pattern films on the lower side have the side on which the conductor pattern 3 is provided as the lower side, and the two single-sided conductor pattern films on the upper side have the side on which the conductor pattern 3 is provided on the upper side. Laminate as That is, the two single-sided conductor pattern films in the center are laminated facing each other on the surface on which the conductor pattern 3 is not formed, and the remaining two single-sided conductor pattern films are composed of the surface on which the conductor pattern 3 is formed and the conductor. The surfaces where the pattern 3 is not formed are laminated facing each other.

  The four single-sided conductor pattern films laminated in this way are pressed from above and below by a vacuum heating press at a temperature not lower than the melting point of the first metal and lower than the softening point of the base resin. Thereby, a conductive particle lump in which the coated conductive particles 5 are integrated is formed, and a metal diffusion layer between the coated conductive particles 5 and the conductor pattern 3 is formed. During this time, the resin does not soften or flow, and the base resin does not flow into the via. Then, by heating at a temperature equal to or higher than the softening point of the base resin, the insulating base resin flows into the gap between the conductor pattern 3 and the conductive particle lump and the gap of the conductive particle lump, and the thermoplastic resin films 2 To integrate. According to such temperature control, since the base resin flows after interlayer conduction is ensured reliably, via conduction is not hindered and highly reliable interlayer connection can be performed.

  The temperature, pressure and time controlled by the vacuum heating press are in the range of 232 to 350 ° C., 2 to 30 MPa and 5 to 30 minutes.

  A multilayer wiring board as shown in FIG. 1G can be obtained by the manufacturing method as described above. Since the resin of each single-sided conductor pattern film is formed of the same thermoplastic resin material, it is softened by heating and reliably integrated by pressurization.

  In the above wiring board manufacturing method, the metal foil 1 and the thermoplastic film 2 are attached, and a plurality of single-sided conductor pattern films each having the conductor pattern 3 formed on one side are laminated. The metal foil 1 may be attached to both outer surfaces of the wiring board with a vacuum heating press, and then the conductor pattern 3 may be formed.

  Next, an interlayer connection mechanism when tin is used as the first metal forming the surface layer of the coated conductive particles 5 and copper is used as the second metal forming the core material will be described with reference to FIGS. FIG. 2 is a partially enlarged view schematically showing a state in the via hole, and FIG. 3 is an SEM photograph of a cross section of the wiring board.

  Before heating by the vacuum heating press, as shown in FIG. 2A, the via hole is filled with coated conductive particles 5 having a surface layer 22 made of tin on the surface of a core material 21 made of copper. And it heat-presses using the vacuum heating press machine at the temperature more than melting | fusing point (232 degreeC) of tin, and less than the softening point of base-material resin. Thereby, tin in the surface layer of the coated conductive particles 5 in contact with each other diffuses into the metal, and tin diffuses from the surface layer of the coated conductive particles 5 to the copper of the core material, as shown in FIG. A conductive particle lump 24 in which the conductive particles 5 are integrated is formed.

  In addition, the conductive particle lump 24 is formed, and the coated conductive particles 5 that are in contact with the conductive pattern 3 are pressed against the conductive pattern 3, whereby the tin component of the surface layer 22 of the coated conductive particles 5 and the conductive pattern The copper constituting 3 diffuses mutually, and a metal diffusion layer 25 is formed at the interface between the conductor pattern 3 and the coated conductive particles 5. Thereby, the interlayer connection between the conductor patterns 3 is ensured through the conductive particle block 24.

  Further, by continuing the heating and pressurization, as shown in FIG. 2C, the resin of the thermoplastic resin film 2 softened by heating becomes a gap between the conductor pattern 3 and the conductive particle lump 24 and the conductive particle lump. The conductive particles lump vias are reinforced by entering into the voids in 24. Thereby, it is possible to ensure mechanical reliability against a temperature shock caused by thermal stress.

  FIG. 3 is an SEM (Scanning Electron Microscope) photograph of a cross section of the wiring board manufactured by the above-described method. As shown in FIG. 3A, the connection between the conductor patterns 3 is made by the coated conductive particles 5. Further, as shown in FIG. 3B, a metal diffusion layer 5 a between the coated conductive particles 5 and a metal diffusion layer 5 b between the metal of the conductive pattern 3 and the coated conductive particles 5 are formed between the conductive patterns 3. Has been.

  As described above, by using the coated conductive particles 5 as an interlayer connection material for connecting a plurality of layers of conductor patterns, the metal composition in the via serving as the interlayer connection is made uniform without being localized. Further, tin in the surface layer 22 of the coated conductive particles 5 causes metal diffusion only in a portion in contact with other coated conductive particles or conductor patterns, so that the thickness of the intermetallic compound layer is controlled to a necessary amount.

  Next, as shown in FIG. 4, the coated conductive particles 41 having the intermediate layer 41c made of the third metal between the core material 41b made of the second metal and the surface layer 41a made of the first metal were used. The case will be described. The manufacturing method of the wiring board is the same as the above method except that the coated conductive particles are different.

  In the coated conductive particles 41, the surface of the core material 41b made of the second metal is plated with the third metal serving as the intermediate layer 41c, and the surface of the intermediate layer 41c is plated with the first metal serving as the surface layer 41a. ing. It is preferable that the first metal includes any one of tin and indium, or a solder made of at least two of tin, silver, copper, zinc, lead, antimony, bismuth, palladium, indium, and gold. . In addition, it is more preferable that solder does not contain lead from an environmental viewpoint. Moreover, it is preferable that a 2nd metal contains one or more metals among copper, silver, gold | metal | money, zinc, palladium, and nickel.

  As the third metal, various metals different from the first and second metals can be used depending on the combination of the first and second metals. For example, when the first metal diffuses very easily with respect to the second metal, the second metal is coated by coating the second metal with a third metal that is difficult to diffuse with the first metal. The first metal is less likely to diffuse, and the first metal can be efficiently diffused with the conductive pattern outside the particles and between the conductive particles. That is, a metal is selected such that the diffusion rate at which the first metal diffuses into the third metal is smaller than the diffusion rate at which the first metal diffuses into the second metal. By selecting such a third metal as the intermediate layer 41c, it is possible to prevent the first metal of the surface layer 41a from diffusing into the second metal of the core material 41b.

  Even when it is difficult to coat the first metal directly on the second metal, the first metal can be coated by coating the third metal as the intermediate layer. In other words, the ionization tendency of the third metal forming the intermediate layer 41c is selected so as to be located between the first metal and the second metal. Thereby, since the ionization tendency of the first metal and the second metal is greatly separated, even when it is difficult to directly plate the first metal on the surface of the core material 41b made of the second metal, Plating can be performed through the intermediate layer 41c.

  Here, an interlayer connection mechanism in the case where silver whose hardness is smaller than copper is used for the metal forming the core of the coated conductive particles will be described with reference to FIG. By using silver for the core material 41b, the purpose is to make the gap between the conductor pattern 3 and the conductive particle lump 43 and the gap in the conductive particle lump 43 smaller than when copper is used as the core material, and to ensure higher interlayer conductivity. It is said.

  The coated conductive particles 41 are formed using tin as the first metal forming the surface layer 41a, silver as the second metal forming the core material 41b, and copper as the third metal forming the intermediate layer 41c. Since the diffusion rate at which tin diffuses into copper is smaller than the diffusion rate at which tin diffuses into silver, tin in the surface layer 41a is difficult to diffuse into the core material 41b made of silver.

  Before heating by the vacuum heating press, the via hole is filled with coated conductive particles 41 as shown in FIG. And when the heating and pressurization is performed at a temperature not lower than the melting point of tin (232 ° C.) and lower than the softening point of the base resin by using a vacuum heating press, tin on the surface of the coated conductive particles 41 in contact with each other is metal. Simultaneously with the diffusion, tin begins to diffuse into the intermediate layer 41c made of copper and the core material 41b made of silver, and as shown in FIG. 4B, a metal diffusion layer 42 of tin and copper and tin and silver is formed in the vicinity of the particle surface. Is formed. In addition, an integrated conductive particle mass 43 is formed in the via hole.

  At the same time that the conductive particle mass 43 is formed, the coated conductive particles 41 in contact with the conductor pattern 3 are pressed against the conductor pattern 3, thereby causing the tin component in the conductive particle mass 43 and the conductor pattern 3 to The constituent copper diffuses mutually, and a metal diffusion layer 44 is formed at the interface with the conductor pattern 3 to ensure electrical conduction between the layers.

  Further, since silver having a hardness lower than that of copper is used for the core material 41b, the silver particles are deformed at the time of pressurization, and the gap between the conductor pattern 3 and the conductive particle lump 43 and the minute gap in the conductive particle lump 43 are copper. Is less likely to occur than the heartwood. Therefore, it is possible to ensure reliability against temperature shock due to thermal stress or the like without causing the base resin to enter the gap between the conductor pattern 3 and the conductive particle lump 43 and the gap in the conductive particle lump 43.

  Thus, the coated conductive particles 41 use tin as the first metal that forms the surface layer 41a, silver as the second metal that forms the core material 41b, and copper as the third metal that forms the intermediate layer 41c. By being formed, it is possible to directly plate silver and tin, which have a large ionization tendency. Further, since the diffusion rate of tin diffusing into copper is smaller than the diffusion rate of tin diffusing into silver, the copper intermediate layer suppresses the diffusion of tin into the core material 41b and is a conductor pattern. Tin can be used effectively for connection with copper.

  In the above wiring board manufacturing method, the single-sided conductor pattern film is laminated as shown in FIG. 2 (f). However, if it is a structure for obtaining a multilayer wiring board or double-sided wiring board that requires interlayer connection, The number of layers and the laminated pattern are not limited.

  For example, as shown in FIG. 5, a single-sided film 5 a on which a copper foil for forming a conductive pattern is attached, a single-sided conductive pattern film 5 b in which a conductive pattern is formed on one side of a base material, and a copper foil 5 c After laminating and heat-pressing, the copper foil 5c on both sides may be patterned to obtain a multilayer wiring board.

  Moreover, as shown in FIG. 6, the single-sided conductor pattern film 6a and the double-sided board 6b in which the conductor pattern was formed on both surfaces of the base material may be laminated and heated to obtain a multilayer wiring board. .

  Further, as shown in FIG. 7, resin films 7b filled with coated conductive particles in via holes are laminated on both sides of a double-sided substrate 7a having a conductor pattern formed on both sides of a base material, and copper foil 7c is further formed on both sides thereof. After laminating and heating and pressing, the copper foil 7c on both sides may be patterned to obtain a multilayer wiring board.

  Furthermore, as shown in FIG. 8, copper foils 8b for forming a conductor pattern are laminated on both surfaces of a resin film 8a filled with coated conductive particles in via holes, heated and pressed, and then copper foils 8b on both sides are formed. The double-sided wiring board may be obtained by patterning.

  Moreover, as shown in FIG. 9, after laminating | stacking the single-sided film 9b and the copper foil 9c with which the copper foil 9a for forming a conductor pattern was stuck and heat-pressing, patterning the copper foils 9a and 9c of both surfaces Thus, a double-sided wiring board may be obtained.

It is sectional drawing which shows the manufacturing method of the wiring board in embodiment of this invention in the order of the process. It is sectional drawing which shows typically the state in the via hole in the interlayer connection part of the wiring board in embodiment of this invention. It is a SEM photograph of the section of the wiring board in the embodiment of the present invention. It is sectional drawing which shows typically the state in the via hole in the interlayer connection part of the wiring board in embodiment of this invention. It is sectional drawing which shows the other lamination | stacking method of the wiring board in embodiment of this invention (the 1). It is sectional drawing which shows the other lamination | stacking method of the wiring board in embodiment of this invention (the 2). It is sectional drawing which shows the other lamination | stacking method of the wiring board in embodiment of this invention (the 3). It is sectional drawing which shows the other lamination | stacking method of the wiring board in embodiment of this invention (the 4). It is sectional drawing which shows the other lamination | stacking method of the wiring board in embodiment of this invention (the 5). It is sectional drawing which shows typically the state in the via hole in the interlayer connection part of the wiring board in a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Metal foil, 2 Thermoplastic resin film, 3 Conductor pattern, 4 Bottomed via hole, 5 Coated conductive particle, 21 Core material, 22 Surface layer, 23 Metal diffusion layer, 24 Conductive particle lump, 25 Metal diffusion layer, 41 Coated conductive particle , 42 metal diffusion layer, 43 conductive particle mass, 44 metal diffusion layer, 101 metal particle, 102 insulating substrate, 103 conductor pattern

Claims (12)

In an insulating substrate made of a thermoplastic resin, in a wiring board having a plurality of conductor patterns,
Conductive particle mass formed by heating and pressurizing the coated conductive particles filled in the via holes provided in the insulating base material,
A metal diffusion layer that electrically connects the conductive particle mass formed by diffusion of the metal forming the coated conductive particles and the metal forming the conductive pattern and the conductive pattern;
The coated conductive particles have a core material made of a second metal having a melting point higher than the heating temperature at the time of interlayer connection, and a surface layer made of a metal that forms the conductor pattern and a first metal that causes metal diffusion. A wiring board characterized by that. The coated conductive particles have an intermediate layer made of a third metal between a core material made of the second metal and a surface layer made of the first metal,
The third metal is a metal whose diffusion rate into the second metal is smaller than the diffusion rate of the first metal into the second metal, and / or whose ionization tendency is the first metal. The wiring board according to claim 1, wherein the wiring board is a metal positioned between the first metal and the second metal.   The wiring board according to claim 1, wherein the thermoplastic resin has a softening point higher than a melting point of the first metal.   The first metal contains tin or indium, or contains two or more metals selected from tin, silver, copper, zinc, lead, antimony, bismuth, palladium, indium and gold. The wiring board according to claim 1.   2. The wiring board according to claim 1, wherein the second metal includes one or more metals selected from copper, silver, gold, zinc, palladium, and nickel.   The wiring board according to claim 1, wherein the first metal occupies 5 mass% to 60 mass% of the mass of the coated conductive particles.   2. The wiring board according to claim 1, wherein the first metal is tin and the second metal is copper.   3. The wiring board according to claim 2, wherein the first metal is tin, the second metal is silver, and the third metal is copper. In the method of manufacturing a wiring board having a plurality of conductor patterns on an insulating base material made of a thermoplastic resin,
Forming a via hole in the insulating substrate;
Coat conductivity having a core material made of a second metal having a melting point higher than the heating temperature at the time of interlayer connection in the via hole, and a surface layer made of the metal forming the conductor pattern and the first metal causing metal diffusion. A filling step of filling the particles;
By heating and pressurizing, a conductive particle lump of the coated conductive particles is formed, a metal diffusion layer of the metal of the conductor pattern and the first metal is formed, and the conductor patterns of the plurality of layers are electrically connected. A method for manufacturing a wiring board, comprising: a connecting step.   In the connecting step, pressurization is performed for a predetermined time at a temperature equal to or higher than the melting point of the first metal and lower than the softening point of the thermoplastic resin, and after the predetermined time, at a temperature equal to or higher than the softening point of the thermoplastic resin. The method for manufacturing a wiring board according to claim 9, wherein pressurization is performed. The coated conductive particles have an intermediate layer made of a third metal between a core material made of the second metal and a surface layer made of the first metal,
The third metal is a metal whose diffusion rate into the second metal is smaller than the diffusion rate of the first metal into the second metal, and / or whose ionization tendency is the first metal. The method of manufacturing a wiring board according to claim 9, wherein the metal is located between the first metal and the second metal. The method for manufacturing a wiring board according to claim 9, wherein the thermoplastic resin has a softening point higher than a melting point of the first metal.

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