JPWO2016088540A1 - Conductive composition, wiring board and manufacturing method thereof - Google Patents

Abstract

The conductive composition of the present invention includes a conductive filler, an epoxy resin, and a curing agent for the epoxy resin. The curing agent comprises at least one acid anhydride. The acid anhydride is contained in an amount of 0.4 to 1.2 molar equivalents relative to 1 molar equivalent of the epoxy group of the epoxy resin. It is preferable that the epoxy resin and the curing agent are contained in a total amount of 3% by mass to 35% by mass with respect to the total amount of the conductive filler. It is also preferable that the conductive filler contains copper-based powder or / and silver-based powder.

Description

  The present invention relates to a conductive composition. Moreover, this invention relates to the wiring board using this electrically conductive composition, and its manufacturing method.

  Various conductive compositions containing a conductive filler, a thermosetting resin, and a curing agent thereof are known. For example, Patent Document 1 describes a conductor paste composition for filling via holes, which includes a conductor filler, a liquid epoxy resin, and a curing agent thereof.

  Patent Document 2 includes a base metal powder having an average particle size of 0.5 μm or more and 15.0 μm or less, an epoxy resin and a curing agent, and the equivalent of the curing agent added to the epoxy resin reaction equivalent is 30% to 50%. The following thermosetting paste compositions are described. An acid anhydride is used as the curing agent. This paste composition is characterized by a long pot life.

  Patent Document 3 describes a conductive paste for bottomed via filling containing conductive particles and a solvent. The conductive particles include Sn—Ag—Cu solder powder and silver powder. In this document, it is described that when this conductive paste is used, bubbles can be removed without introducing a special device even if the diameter of the bottomed via hole is reduced. Patent Document 4 describes a conductive composition containing solder powder, silver powder, an epoxy resin, and an acid anhydride.

US5652042A JP-A-9-31307 JP 2008-288368 A US2010 / 084757A1

  In the technique described in Patent Document 1, the insulating layer is in a B stage and in an uncured state at the stage of filling the via hole with the composition, and after the conductor paste composition is filled into the via hole, the press contact process is performed. The composition can be applied only to the printed wiring board manufacturing method as described above, and is not applicable because it does not exhibit electrical conductivity in a connection body that does not perform pressurization such as pressing during curing. The paste composition described in Patent Document 2 is characterized in that it is cured at a low temperature in a short time, and has a drawback that it is difficult to exhibit conductivity when it is cured after filling a via hole. Since the technologies described in Patent Documents 3 and 4 use a fusible metal such as solder powder as a main component, the fusible metal is placed in the wiring layer, the copper particles, or the like under an environmental test such as a high temperature standing test. Diffusion is promoted and voids are generated, so that there is a drawback that deterioration of conduction resistance occurs.

  The object of the present invention is to eliminate the various disadvantages of the prior art described above, and to provide a conductive composition having good connection with metal terminals and good internal conductivity without the need for pressure welding in the curing stage. There is to do.

The present invention is a conductive composition comprising a conductive filler, an epoxy resin, and a curing agent for the epoxy resin,
The curing agent comprises at least one acid anhydride represented by the following formula (1):
It provides a conductive composition in which the acid anhydride is contained in an amount of 0.4 molar equivalent or more and 1.2 molar equivalent or less with respect to 1 molar equivalent of the epoxy group of the epoxy resin.

In the present invention, the cured body of the conductive composition is filled in vias,
A metal conductor layer is formed on each of an upper portion and a lower portion of a cured body, and a wiring board in which upper and lower conductor layers are conducted through the cured body is provided.

Further, the present invention fills the conductive composition in a via that penetrates the insulating layer and whose lower opening is closed by the lower conductor layer from which the metal is exposed,
Curing the filled conductive composition to form a cured body of the composition in the via;
A method of manufacturing a wiring board comprising a step of forming an upper conductor layer on a top of the cured body by vapor phase or liquid phase film formation, and electrically connecting the upper conductor layer and the lower conductor layer through the cured body Is to provide.

  Furthermore, the present invention provides a conductor comprising the above-described conductive composition, exposed in the plane of the wiring board, and connecting between at least two metal wirings or / and metal terminals spaced apart from each other. .

Furthermore, the present invention supplies the conductive composition between at least two metal wirings or / and metal terminals that are exposed in the plane of the wiring board and spaced apart from each other,
Provided is a method for connecting a metal wiring or / and a metal terminal, which includes a step of curing the conductive composition to form a cured body and conducting the metal wiring or / and the metal terminal via the cured body. Is.

FIG. 1A to FIG. 1C are schematic views sequentially showing a part of a process of manufacturing a wiring board using the conductive composition of the present invention. 2 (a) to 2 (d) are schematic views sequentially showing a part of the process of manufacturing a wiring board using the conductive composition of the present invention, following FIG. 3 (a) to 3 (d) are schematic views sequentially showing a part of the process of manufacturing a wiring board using the conductive composition of the present invention, following FIG. 4 (a) to 4 (c) are schematic views sequentially showing steps of manufacturing a wiring connection structure using the conductive composition of the present invention. FIG. 5 is a schematic view showing a connection structure of another wiring manufactured using the conductive composition of the present invention.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The conductive composition of the present invention contains a conductive filler. The conductive filler can include, for example, copper-based powder or / and silver-based powder. As the copper base powder, copper powder, copper base alloy powder, silver inclined copper powder, metal-coated copper powder such as silver-coated copper powder and nickel-coated copper powder, and the like can be used. On the other hand, as the silver base powder, silver powder, silver base alloy powder and the like can be used. These powders can be used alone or in combination of two or more. The conductive filler may be composed only of copper-based powder and / or silver-based powder, or, in order to strengthen the bonding between the conductive fillers, the content of 20% by mass or less in the entire conductive filler. If so, tin base powder or solder powder can be included.

  The conductive filler preferably has a particle size of 0.05 μm to 10 μm, more preferably 0.1 μm to 8.0 μm, and still more preferably 0.3 μm to 7.0 μm. . By using a conductive filler having a particle diameter in this range, the conductive composition can be successfully filled into a small diameter via hole, for example, a via hole having a diameter of 75 μm or less. The particle diameter is defined as an arithmetic average value obtained by magnifying and observing the conductive composition with an electron microscope, measuring the ferret diameter of 100 or more particles. In addition, the shape of the conductive filler is not particularly limited, and a spherical shape, an ellipsoid shape, a flake shape, a rod shape, and a dendrite shape can be employed. It is possible to set desired viscosity characteristics and filler filling properties.

  The conductive filler is preferably contained in the conductive composition in an amount of 70% by mass to 95% by mass, and more preferably 75% by mass to 93% by mass. When the copper-based powder and / or the silver-based powder is contained in an amount within this range, the cured product formed from the conductive composition has a sufficiently high conductivity and the flow of the conductive composition. Sex can be secured.

  The conductive composition contains an epoxy resin in addition to the copper-based powder and / or the silver-based powder. The epoxy resin is a thermosetting synthetic resin having a reactive epoxy group at the end of the molecule. Epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetramethylbiphenyl type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, dicyclopentadiene-phenol addition reaction Type epoxy resin, phenol aralkyl type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, hydroxynaphthalene type epoxy resin, anthracene type epoxy resin, naphthol-cresol co-condensed novolak type epoxy resin, aromatic Hydrocarbon formaldehyde resin modified phenolic resin type epoxy resin, biphenyl novolac type epoxy resin, glycidylamine type epoxy resin, Futanren type epoxy resins, glycidyl amine epoxy resins can be used. The epoxy resin can be used alone or in combination of two or more, and the viscosity characteristics of the conductive composition, the curing speed, the viscoelasticity, heat resistance, thermal expansion coefficient, etc. of the cured body are determined depending on the blending ratio. Can be set. Among these, bisphenol A type, bisphenol F type, naphthalene type epoxy resin, glycidylamine type epoxy resin, and dicyclopentadiene-phenol addition reaction type epoxy resin are resins that can easily control the paste viscoelasticity of the conductive composition. It is particularly preferable from the point that the heat resistance of the cured body can be improved.

Furthermore, these epoxy resins have an epoxy equivalent of 90 g / eq. 500 g / eq. By being the following, the curing rate suitable for practical use can be controlled while maintaining the conductive activity of the conductive composition of the present invention in a high state. Furthermore, 95 g / eq. 450 g / eq. Or less, more preferably 97 g or more and 420 g or less. Epoxy equivalent is 90 g / eq. In the case of the above, the pot life of the conductive composition of the present invention can be made sufficiently long. The epoxy equivalent is 500 g / eq. In the case of the following, a cured product can be obtained without requiring excessive time for curing. Further, by using an epoxy resin having an epoxy equivalent within this range, a cured product having satisfactory reactivity and heat resistance can be obtained from the conductive composition of the present invention. The term “epoxy equivalent” as used herein refers to the weight average epoxy equivalent of the total epoxy resin present in the conductive composition of the present invention. For example, when the weight fraction with respect to the sum of the epoxy resin components of the epoxy resin compounded in any i-th type is ω _i and the epoxy equivalent is E _i , the epoxy equivalent of the total epoxy resin present in the conductive composition P E _P is expressed by the following formula.
E _P = Σ (ω _i × E _i )

  The conductive composition also includes an epoxy resin curing agent. In the present invention, it is preferable to use at least one acid anhydride represented by the following formula (1) as a curing agent.

  The acid anhydride represented by the formula (1) has a bulky molecular structure and has a high boiling point. Therefore, the conductive composition of the present invention containing this acid anhydride has a relatively long time until the acid anhydride that has been ring-opened by curing with the epoxy resin is deactivated. In addition, the acid anhydride represented by the formula (1) has high activity of the acid anhydride that is ring-opened when heated, and has the ability to remove oxides present on the metal surface. Due to these reasons, in the conductive composition of the present invention, the acid anhydride represented by the formula (1) is contained in the conductive composition while maintaining the fluid state until it is completely cured. Remove the oxide film present on the surface of the copper-based powder and / or silver-based powder in the object, and remove the oxide film present on the surface of the metal wiring made of the conductor that is the object of application. . As a result, the cured body formed of the conductive composition has an advantageous effect that the conductivity is high and the connection resistance between the cured body and the metal wiring is reduced. Therefore, unlike the conventional technique, for example, the technique described in Patent Document 1, the conductive composition of the present invention can obtain a cured product having sufficiently high conductivity even when applied and cured without applying pressure. Can do. In the present invention, “coating and curing a conductive composition under no pressure” means that when the conductive composition of the present invention is applied by a screen printing method and / or a vacuum printing method, an additional amount other than the coating pressure is applied. This means that the composition is applied and cured in the absence of a pressing step (for example, a step such as a vacuum press or a pressing press).

  From the viewpoint of making the above-mentioned advantageous effects more prominent, the compounds represented by the following formulas (1a) to (1c) are specifically used as the acid anhydride represented by the formula (1). Is preferred. These acid anhydrides can be used individually by 1 type or in combination of 2 or more types.

  The acid anhydride represented by the formula (1) is preferably contained in an amount of 0.4 molar equivalent or more and 1.2 molar equivalent or less with respect to 1 molar equivalent of the epoxy resin contained in the conductive composition. . An acid anhydride is contained in an amount of 0.4 molar equivalent or more and 1.2 molar equivalent or less with respect to 1 molar equivalent of the epoxy resin, for example, the epoxy equivalent of the epoxy resin is x (g), Is equivalent to y (g), it means that the acid anhydride is contained 0.4y (g) or more and 1.2y (g) or less with respect to the epoxy resin x (g). By setting the compounding ratio of the epoxy resin and the acid anhydride in this way, the oxide film present on the surface of the conductive filler in the conductive composition and the oxide film on the surface of the metal wiring that is the object to be coated can be obtained. While being able to remove enough, it can prevent effectively that an unreacted substance produces | generates at the time of hardening, and can fully improve the electroconductivity of the hardening body formed from an electroconductive composition. From the viewpoint of making this effect more remarkable, the amount of the acid anhydride is more preferably 0.6 molar equivalents or more and 1.0 molar equivalents or less with respect to 1 molar equivalent of the epoxy resin. More preferably, it is 0.7 to 0.9 molar equivalent.

  The curing agent comprising the epoxy resin as an organic component in the conductive composition and the acid anhydride represented by the formula (1) is 3% by mass or more and 35% by mass with respect to the amount of the conductive filler. It is preferable that it is contained by mass% or less. By setting the ratio of the organic component and the conductive filler component in the conductive composition within this range, the conductivity of the cured body formed from the conductive composition can be made sufficiently high. From the viewpoint of making this effect even more prominent, the curing agent comprising the epoxy resin and the acid anhydride represented by the formula (1) is 5% by mass with respect to the amount of the conductive filler in the total amount thereof. More preferably, it is contained in an amount of 30% by mass or less, and more preferably 9% by mass or more and 23% by mass or less.

  In the conductive composition, in addition to the above-described components, other components can be blended as necessary. Examples of such components include a reactive diluent that is a substance involved in the curing of the epoxy resin, a solvent, a coupling agent, a leveling agent, and a dispersant. In particular, the conductive composition does not substantially contain a solvent, or even if it contains a solvent, the content is preferably a low ratio of 10% by mass or less with respect to the conductive composition. By suppressing the ratio of the solvent contained in the conductive composition as much as possible, various inconveniences caused by the use of the solvent, for example, significant increase in viscosity due to solvent volatilization in the coating process, and void generation due to bumping of the solvent during heat curing In addition, it is possible to effectively prevent the occurrence of dents due to volume shrinkage before and after heat curing. From this viewpoint, it is preferable that the epoxy resin contained in the conductive composition is liquid. In addition, “substantially free of solvent” is intended to exclude unintentionally adding a solvent to the conductive composition, and inevitably with respect to a small amount of solvent, for example, the conductive composition. It is acceptable that a solvent of 1% by mass or less is mixed. For mixing the conductive composition, a rotating / revolving stirrer, a screw mixer, a Henschel mixer, an internal kneader, a butterfly mixer or the like can be used. If necessary, the conductive filler can be mixed with a three-roll mill. A kneading method that simultaneously performs crushing can be employed.

As described above, the conductive composition of the present invention is capable of obtaining a cured product having a sufficiently high conductivity without requiring pressure contact in the curing stage. Taking advantage of this advantage, the conductive composition of the present invention can be used, for example, as an interlayer connection via filler for build-up substrates. Specifically, the lower opening of the via that penetrates the hardened buildup insulating layer is blocked by the exposed lower conductor layer of a metal such as copper, and the lower conductor layer is exposed at the lower opening of the via. Filling the via in a state with the conductive composition of the present invention;
Curing the filled conductive composition to form a cured body of the composition in the via;
Forming an upper conductor layer on the hardened body by vapor phase or liquid phase film formation, and electrically connecting the upper conductor layer and the lower conductor layer through the hardened body. The method can be done. FIG. 1 to FIG. 3 show an example of the procedure of this manufacturing method, which is a build-up wiring layer formed by a modified semi-additive method (MSAP method) when a copper foil layer with a carrier is used as a wiring seed layer. An example of formation is shown. By applying the conductive composition of the present invention to the build-up wiring layer by this MSAP method, electroless inside the via as in the case of forming a via filling body (filled via plating) by plating by the conventional build-up wiring method There is an advantage that it is not necessary to form a wiring seed layer by plating or sputtering. However, the method is not limited to this, and a wiring seed layer such as electroless plating or sputtering may be formed as necessary. As for the wiring formation method, in addition to the illustrated MSAP method, a semi-additive method (SAP) in which a copper foil layer is etched in advance to form a replica of the roughened surface of the copper foil layer on the insulating layer and then a wiring seed layer is formed. Method) or the like. Moreover, although the lamination | stacking form of only one side is described in FIG. 1 thru | or FIG. 3 for the simplification, the form laminated | stacked on both surfaces may be taken.

  As shown in FIG. 1A, circuit wiring 11 made of metal is formed on one surface 10 </ b> A of the base material layer 10. There is no restriction | limiting in particular in the kind of metal which comprises the circuit wiring 11, For example, the thing similar to the metal used as the metal foil 14 mentioned later can be used. There is no restriction | limiting in particular in the formation method of the circuit wiring 11, For example, a subtractive method, a pattern plating method, a semi-additive method etc. can be used. An insulating layer 13 is laminated on the surface of the wiring board 12 formed in this way on which the circuit wiring 11 is formed. Further, the metal foil 14 is laminated on the surface 13A opposite to the surface facing the wiring substrate 12 in the insulating layer 13. In this case, the insulating layer 13 and the metal foil 14 may be laminated in advance, and the laminated body (not shown) may be laminated on the wiring board 12.

  The metal foil 14 preferably has a thickness of 4 μm or less. In particular, when the thickness of the metal foil 14 is 0.1 μm or more and 4 μm or less, a high-definition circuit with a narrow circuit pitch can be formed with a better etching factor. As described above, since the metal foil 14 is thin, it may not be easy to handle. Therefore, it is advantageous to use a metal foil 16 with a carrier having a metal foil 14 and a carrier 15 provided so as to be peelable from the metal foil 14. In the metal foil 16 with a carrier, a release layer 17 may be provided between both layers in order to improve the peelability between the metal foil 14 and the carrier.

  The metal foil 14 may be a rolled foil, an electrolytic foil, or a vapor phase foil, but is more preferably an electrolytic foil or a vapor phase foil from the viewpoint that it can be easily formed on a carrier. If it is electrolytic foil, it can obtain by depositing a metal so that it may become predetermined thickness on the surface of the carrier 15. FIG. The metal foil 14 should just have electroconductivity, for example, copper foil, aluminum foil, nickel foil, cobalt foil, gold foil, platinum foil etc. or these alloy foils etc. can be used. In particular, a copper foil or a copper alloy foil can be suitably used because it has a low electrical resistivity and is excellent in workability during circuit formation by etching or the like.

  The carrier 15 is used as a support for supporting the metal foil 14 in order to improve the handleability of the thin metal foil 14. The material constituting the carrier 15 is not particularly limited. For example, resin films such as PET film, PEN film, aramid film, polyimide film, polyamide film, liquid crystal polymer film, copper foil, copper alloy foil, aluminum foil, aluminum A composite metal foil, a stainless steel foil or the like in which a metal plating layer such as copper or zinc is provided on the surface of the foil can be used.

  The insulating layer 13 located between the metal foil 14 and the wiring board 12 is used for electrical insulation between the circuit wiring 11 on the wiring board 12 and the metal foil 14. The insulating layer 13 is, for example, a sheet obtained by impregnating an insulating resin (epoxy resin, cyanate resin, bismaleimide / triazine resin (BT resin), polyphenylene ether resin, phenol resin, imide resin, or the like) into paper or glass nonwoven fabric. It may be an insulating resin base material such as a prepreg in which a necessary number of layers are stacked, or may be an insulating resin layer made of an insulating resin such as an epoxy resin, a polyimide resin, or a polyester resin. This insulating resin layer may contain filler particles composed of various inorganic particles such as silica and alumina from the viewpoint of improving the insulating properties. The insulating layer 13 may be thick enough to achieve electrical insulation between the circuit wiring 11 and the metal foil 14. Moreover, the insulating layer 13 and the metal foil 16 with a carrier may be a metal foil with a resin coating carrier (for example, RCC: Resin Coated on Copper) integrated before lamination.

  A state in which the insulating layer 13 and the metal foil 14 are laminated on the wiring board 12 is shown in FIG. The laminated structure shown in FIG. 1 includes an insulating layer 13, a metal layer composed of a metal foil 14 disposed on one surface of the insulating layer 13, and a conductor layer composed of circuit wiring 11 disposed on the other surface of the insulating layer 13. And a base material layer 10 disposed on the outer surface of the conductor layer.

  Next, as shown in FIG. 1C, the carrier-attached metal foil 16 is attached to one surface of the insulating layer 13 with the metal foil 14 being attached so as to face the one surface of the insulating layer 13. 15. A hole 19 penetrating the metal foil 14 and the insulating layer 13 is formed. In this way, a laminated body 23 with vias is obtained.

  As shown in FIG. 1C, the conduction hole 19 does not penetrate the entire area in the thickness direction of the laminated body 23 with vias, and is a non-through hole. In other words, in the laminated body 18 including the insulating layer 13, the metal layer made of the metal foil 14, and the conductor layer made of the circuit wiring 11, the conduction hole 19 is the circuit wiring 11 in the plan view of the laminated body 18. The metal foil 14 and the insulating layer 13 are perforated so that the circuit wiring 11 is exposed at a position where the metal wire exists. Therefore, the conduction hole 19 does not penetrate the circuit wiring 11.

  The conduction hole 19 can be formed using various drilling methods. For example, laser light irradiation such as a carbon dioxide laser, UV-YAG laser, or excimer laser, a mechanical drill, or the like can be used. When the small-diameter hole 19 is formed, it is advantageous to employ laser light irradiation. In addition, when the conduction hole 19 is formed by laser light irradiation, a method of directly penetrating the insulating layer 13 from the carrier 15 (direct laser drilling method) can be adopted, and first, the conduction hole 19 is formed as a first step. After etching the carrier 15, the release layer 17, and the metal foil 14 using a subtractive method with respect to the portion where the film is to be formed, the insulating layer 13 is formed by laser light using the peripheral metal portion of the formed hole as a mask as a second step. It is also possible to employ a method (conformal method) in which the holes 19 for conduction are formed by penetrating them. Further, these methods are preferable in that the carrier 15 can be used as a printing mask at the time of paste filling described later. The hole diameter (diameter) of the conduction hole 19 is preferably 10 μm or more and 200 μm or less, and more preferably 15 μm or more and 100 μm or less, from the viewpoint of being able to deal with narrow and narrow pitch circuit wiring.

  If the laminated body 23 with a via is obtained in this way, as shown in FIG. 2A, the conductive hole 19 is filled with a paste made of the conductive composition of the present invention. Various printing methods can be used for filling the paste. For example, screen printing, vacuum printing, roll coating, and the like can be mentioned, but vacuum printing that performs squeezing at a multistage vacuum degree is particularly preferable in that voids (bubbles) generated inside the conductive composition can be effectively removed. . The paste is preferably filled so that the inside of the hole 19 is almost completely filled. Since the paste contains copper-based powder and / or silver-based powder which are conductive fillers, the cured body has conductivity. Thus, the conductive filler 24 is formed in the hole 19. The conductive filler 24 is electrically connected to the circuit wiring 11 that forms the bottom of the hole 19.

  When the holes 19 are filled with the paste, the carrier 15 and the release layer 17 are peeled off from the metal foil 14 as shown in FIG. The exposed metal foil 14 becomes a metal layer for circuit wiring. Further, when the carrier 15 and the release layer are peeled off, the conductive filler 24 is broken as substantially the same surface as the surface of the metal foil 14, and the surface for circuit wiring is exposed. In addition, before peeling, you may perform the drying process of 20 to 100 degreeC and 5 to 180 minutes as needed, for example.

  Thereafter, the conductive filler 24 filled in the holes 19 becomes a cured body by heat curing. The heating conditions can be, for example, 120 ° C. or higher and 230 ° C. or lower and 10 minutes or longer and 180 minutes or shorter. Examples of the heating atmosphere include air and nitrogen atmosphere.

  After this, surface treatment is performed as necessary. The surface treatment combines the surface cleaning of the metal foil 14 and the surface cleaning of the conductive filler 24. Examples of the surface treatment include wet treatment using sodium permanganate and potassium permanganate, and vapor phase treatment such as plasma treatment and corona treatment. Further, an optional layer such as an electroless plating layer, a sputtering layer, or a vapor deposition layer may be formed as necessary.

  Next, as shown in FIG. 2C, a photoresist layer 25 is formed. The photoresist layer 25 is made of a photosensitive resin material such as ultraviolet rays or electron beams. In the present embodiment, a conventionally known photoresist material can be used without any particular limitation. The photoresist material may be positive or negative.

  Next, as shown in FIG. 2 (d), an exposure mask 26 is placed on the laminated body 23 with vias, both are aligned, exposed, and developed to form a resist pattern 29 as shown in FIG. 3 (a). To do. For the development, an appropriate one is used according to the type of the photoresist material. The metal thin film 14 and the conductive filler 24 are exposed at the portion where the photoresist layer 25 has been removed. An upper conductor layer is formed on these exposed portions by vapor deposition or liquid deposition. In this embodiment, as shown in FIG. 3B, electroplating, which is a kind of liquid phase film forming method, is performed to form a plating layer 30 as an upper conductor layer. Note that sputtering or vacuum deposition, which are vapor deposition methods, may be employed instead of the liquid phase deposition method. The upper conductor layer is made of a metal to which a liquid phase film formation method or a vapor phase film formation method can be applied, but electrolytic copper plating is preferable in terms of electrical conductivity and material cost.

  The formed plating layer 30 is electrically connected to the circuit wiring 11 through the conductive filler 24. There is no restriction | limiting in particular in the method of electroplating, The method similar to the method used until now in the said technical field is employable. When the electroplating is completed, the resist pattern 29 is removed, and the metal foil 14 located below the resist pattern 29 is exposed as shown in FIG. The exposed metal foil 14 is easily removed by flash etching as shown in FIG. In this way, the second circuit wiring 31 is formed on the insulating layer 13. For the flash etching, a method similar to the method used so far in the technical field can be adopted. For example, flash etching can be performed using a mixed solution of sulfuric acid and hydrogen peroxide solution.

  As described above, the cured body of the conductive composition of the present invention is filled in the via, and the metal conductor layer is formed on each of the upper part and the lower part of the cured body. Thus, a multilayer wiring board in which the upper and lower metal conductor layers are conductive can be manufactured. Further, by repeating the above operation as many times as necessary, a multilayer wiring board can be manufactured.

  The conductive composition of the present invention can be applied to other uses besides the above-described filling of via holes. For example, it can also be used as a wiring connection paste used to connect two copper wirings exposed in the plane of the wiring board and spaced apart from each other. By applying the conductive composition to such an application, a wiring connection structure in which a cured body of the conductive composition connects two separated copper wirings can be manufactured. This method will be described with reference to FIGS. 4 (a) to 4 (c).

  FIG. 4A shows a plan view of the wiring board 12. The wiring board 12 has two circuit wirings 11a and 11b which are exposed in the plane 12a and are separated from each other. The wiring circuits 11a and 11b are formed of metal wiring such as copper, nickel, tin, and lead. As shown in FIG. 4B, the conductive composition 34 of the present invention is supplied between the two circuit wirings 11a and 11b so as to be bridged. For supplying the conductive composition 34, a supply method under no pressure such as an ink jet method, a dispensing method, a needle coating method, or the like can be used. In the present embodiment, since the conductive composition of the present invention is used, the cured body 35 having sufficiently high conductivity can be obtained even if the supply is performed under no pressure. Next, the conductive composition 34 spanned between the two circuit wirings 11a and 11b is cured in accordance with a conventional method as shown in FIG. The cured body 35 has conductivity. With this cured body 35, the two circuit wires 11a and 11b are made conductive. As a result, the above connection structure is obtained. Instead of supplying the conductive composition 34 between the two circuit wirings 11a and 11b, the conductive composition 34 may be supplied between two metal terminals (not shown). Alternatively, the conductive composition 34 can be supplied between the metal wiring and the metal terminal.

  FIG. 5 shows another embodiment of a wiring connection structure in which a cured body of the conductive composition of the present invention connects two spaced copper wirings. The connection structure of the embodiment shown in FIG. 4C is formed along the plane of the wiring board, whereas the connection structure of this embodiment is orthogonal to the plane H of the wiring board. It is formed along the direction V. Specifically, the wiring board 12 has a laminated structure of a first insulating layer 13a and a second insulating layer 13b. Between the 1st insulating layer 13a and the 2nd insulating layer 13b, the 1st circuit wiring 11a which consists of metal wirings, such as copper, nickel, tin, and lead, is formed. A second circuit wiring 11b made of a metal wiring such as copper, nickel, tin, or lead is formed on the upper surface of the second insulating layer 13b. In FIG. 5, the state in which the second circuit wiring 11b is exposed is shown, but instead, the upper surface of the second circuit wiring 11b may be covered with a third insulating layer (not shown). . The first circuit wiring 11 a and the second circuit wiring 11 b are exposed to the outside on the vertical end surface 12 b of the wiring board 12. The vertical end surface 12b may be an end surface at the peripheral edge of the wiring board 12, or a wall surface of a via hole. The first circuit wiring 11a and the second circuit wiring 11b exposed to the outside on the vertical end surface 12b are electrically connected through a conductive portion made of the cured body 35 of the conductive composition of the present invention. . In the present embodiment, as in the embodiment shown in FIG. 4, instead of supplying the conductive composition 34 between the two circuit wirings 11 a and 11 b arranged along the vertical direction V, the vertical direction The conductive composition 34 may be supplied between two metal terminals (not shown) arranged along V. Alternatively, the conductive composition 34 can be supplied between the metal wiring and the metal terminal arranged along the vertical direction V.

  Also in the connection structure of this embodiment, as in the connection structure shown in FIG. 4C, the conductive composition 34 is supplied with no additive such as an inkjet method, a dispensing method, a syringe coating method, or a tube coating method. Even if the supply method under pressure is used, the cured body 35 having sufficiently high conductivity can be obtained.

  The connection structure shown in FIG. 4C and FIG. 5 is suitable when, for example, a defect such as a disconnection is found in the wiring in the inspection process in the manufacturing process of the wiring substrate, the disconnection is repaired to obtain a completed substrate. Applies to

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, the conductive composition of the present invention can be used in situations such as the connection between the upper and lower terminals and the repair of the component terminal connection short-circuit portion in addition to the above-described filling of the via holes and the connection between the circuit wirings.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” and “part” mean “% by mass” and “part by mass”, respectively.

[Example 1]
As the conductive filler, spherical copper powder having a particle diameter of 3 μm was used. The epoxy resin has an epoxy equivalent of 170 g / eq. A bisphenol A type epoxy resin (EXA-850CRP hereinafter BPA170 manufactured by DIC Corporation) was used. As the curing agent, those shown in Table 1 below were used. As the curing agent, the equivalents shown in Table 1 were used with respect to 1 molar equivalent of the epoxy group of the epoxy resin. The total amount of organic substances (epoxy resin and curing agent) and the amount of copper powder were as shown in Table 1. This raw material was prepared and mixed with a spatula, and then pulverized and mixed using a three-roll mill to obtain a conductive composition.

[Examples 2 to 13 and Comparative Examples 1 to 6]
A conductive composition was obtained in the same manner as in Example 1 except that the composition shown in Table 1 below was adopted. The proportion of silver in the silver-coated copper powder used in Example 6 was 10%.

Example 14
The conductive composition was the same as in Example 1 except that 80 parts of bisphenol F type epoxy resin and 20 parts of glycidylamine type epoxy resin were used as the epoxy resin instead of 100 parts of the epoxy resin used in Example 1. I got a thing.

Example 15
As the epoxy resin, instead of 100 parts of the epoxy resin used in Example 1, 80 parts of bisphenol F type epoxy resin and 20 parts of naphthalene type epoxy resin were used in the same manner as in Example 1 to obtain the conductive composition. Obtained.

Example 16
The conductive composition was the same as in Example 1 except that 80 parts of bisphenol F type epoxy resin and 20 parts of dicyclopentadiene type epoxy resin were used as the epoxy resin instead of 100 parts of the epoxy resin used in Example 1. I got a thing.

Example 17
As the epoxy resin, instead of 100 parts of the epoxy resin used in Example 1, 100 parts of a rubber-modified epoxy resin (EP-4088L manufactured by ADEKA Co., Ltd.) was used. Obtained.

Example 18
A conductive composition was obtained in the same manner as in Example 1 except that 100 parts of glycidylamine type epoxy resin was used as the epoxy resin instead of 100 parts of the epoxy resin used in Example 1.

[Evaluation]
The conductive compositions obtained in the examples and comparative examples were filled into the via holes in the wiring board having 100 via holes in a daisy chain pattern and cured. The diameter of each via hole was 50 μm, and the thickness of the insulating layer was 30 μm. The wiring board was manufactured by the following method.
A glass / epoxy resin double-sided copper-clad board (MCL-E-679FG manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 0.15 mm was used as a substrate, and a lower wiring pattern was formed in advance by a subtractive method. A bismaleimide / triazine resin prepreg (GHPL-830NSF, Mitsubishi Gas Chemical Co., Ltd., thickness 30 μm) and an ultrathin copper foil with a carrier (MT18Ex: Mitsui Kinzoku Mining Co., Ltd .: 18 μm, ultrathin copper layer 2.0 μm) The laminated body with the buildup insulating layer which laminated | stacked and pressure-pressed (220 degreeC 90 minutes, 30 kgf / cm < ² >) and laminated | stacked the copper foil with a carrier was produced. Thereafter, vias were formed by a conformal method. Specifically, an opening having a diameter of 50 μm was previously formed in a copper foil with a carrier by a subtractive method to expose the insulating layer, and a via having a diameter of 50 μmφ was formed by a CO ₂ laser using the opening as a mask. The via was formed so that the lower wiring pattern was exposed at the lower part of the opening. Next, after desmearing the vias with a sodium permanganate solution, the conductive composition was screen-printed at a squeegee pressure of 0.5 MPa and a speed of 10 mm / min under a vacuum of 1 kPa, and further under a vacuum of 70 kPa. The via was filled by screen printing at a squeegee pressure of 0.5 MPa and a speed of 10 mm / min. Then, after temporarily drying (100 degreeC, 30 minutes) in air | atmosphere oven and peeling a carrier manually, it hardened | cured (200 degreeC, 1 hour) in nitrogen oven. Plating resist formation by the MSAP method, copper sulfate plating (thickness 10 μm), resist stripping (sodium hydroxide aqueous solution), flash etching (mixed solution of sulfuric acid and hydrogen peroxide solution), 100-layer single-layer vias in series A daisy chain pattern with two build-up wiring layers was created. The resistance value of this daisy chain pattern was measured by the 4-terminal method to evaluate the conductivity. Evaluation was made according to the following criteria. The results are shown in Table 1.
A: The resistance value is less than 2Ω (best).
B: The resistance value is 2Ω or more and less than 3Ω (good).
C: The resistance value is 3Ω or more and less than 10Ω (possible).
D: The resistance value is 10Ω or more (defect). (O.L: 10 ⁷ Ω or more not included)

  As is apparent from the results shown in Table 1, when the conductive composition of each example is used, the wiring resistance of the wiring board can be suppressed lower than when the conductive composition of the comparative example is used. I understand.

  The conductive composition of the present invention is present on the surface of a metal constituting the bottom surface of a metal-bottomed via hole, for example, an oxide film present on the surface of the metal powder contained in the composition or a mating member as a connection terminal Since it hardens | cures while removing the oxide film to perform, it can become a hardening body with high internal electroconductivity and low contact resistance with a metal terminal. Therefore, even if the conductive composition of the present invention is applied and cured under no pressure, the cured product obtained from the conductive composition has high conductivity and low connection resistance with the metal of the counterpart member. can do.

Claims (11)

A conductive composition comprising a conductive filler, an epoxy resin, and a curing agent for the epoxy resin,
The curing agent comprises at least one acid anhydride represented by the following formula (1):
The electrically conductive composition in which the said acid anhydride is contained 0.4 mol equivalent or more and 1.2 mol equivalent or less with respect to 1 mol equivalent of the epoxy groups of the said epoxy resin.
  The conductive composition according to claim 1, wherein the epoxy resin and the curing agent are contained in a total amount of 3% by mass to 35% by mass with respect to the total amount of the conductive filler.   The conductive composition according to claim 1, wherein the conductive filler contains copper-based powder or / and silver-based powder.   4. The conductive composition according to claim 1, wherein the epoxy resin has an epoxy equivalent of 90 g or more and 500 g or less.   5. The conductive composition according to claim 1, wherein the copper-based or / and silver-based powder has an average particle size of 0.1 μm to 10 μm.   The conductive composition according to any one of claims 1 to 5, which does not contain an organic solvent.   The connection structure of the wiring which the hardening body of the electrically conductive composition as described in any one of Claims 1 thru | or 6 connects between the spaced apart metal wiring or / and a metal terminal. The cured body of the conductive composition according to any one of claims 1 to 6 is filled in a via,
A wiring board in which a metal conductor layer is formed on each of an upper part and a lower part of a cured body, and the upper and lower conductor layers are conducted through the cured body. A conductive composition according to any one of claims 1 to 6 is filled in a via penetrating the insulating layer and having a lower opening closed by a lower conductor layer exposed by metal,
Curing the filled conductive composition to form a cured body of the composition in the via;
A method of manufacturing a wiring board comprising a step of forming an upper conductor layer on a top of the cured body by vapor phase or liquid phase film formation, and electrically connecting the upper conductor layer and the lower conductor layer through the cured body .   A conductor made of the conductive composition according to any one of claims 1 to 6, which is exposed in the plane of the wiring board and connects between at least two metal wirings and / or metal terminals which are spaced apart from each other. . Supplying the conductive composition according to any one of claims 1 to 6 between at least two metal wirings or / and metal terminals that are exposed in the plane of the wiring board and spaced apart from each other;
A method of manufacturing a metal wiring or / and metal terminal connection body comprising a step of curing the conductive composition to form a cured body and conducting the metal wiring or / and metal terminals through the cured body. .