JP2004349729A - Circuit board and its producing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board in which a wiring layer and an insulator layer have a sufficient bonding strength, and high reliability is realized in inner via connection. <P>SOLUTION: The circuit board comprises inner via conductors 102 formed in the thickness direction of an insulator layer 101 in order to connect the upper and lower surfaces of the insulator layer 101 electrically, and lands 103 arranged on the upper and lower surfaces of the insulator layer 101 while being connected electrically with the inner via conductors 102. The insulator layer 101 includes a surface 105 having a high compositional ratio of organic resin, and a core 106 having a low compositional ratio of organic resin formed in the order of the surface 105/the core 106/the surface 105. The core 106 is composed of a porous body, the lands 103 arranged on the upper and lower surfaces of the insulator layer 101 are buried in the surface until they touch the core 106 and the inner via conductors 102 has a thickness substantially identical to that of the core part 106. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a circuit board having excellent connection reliability and excellent bonding strength of a wiring pattern, and a method for manufacturing the same.

  In recent years, as electronic devices have become smaller, lighter, and have higher functions and higher performance, multilayer circuits that allow semiconductor chips such as LSIs to be mounted at high density not only in industrial applications but also in the field of consumer devices. There is a strong demand for supplying substrates at low cost.

  In response to such market demands, technology development has been conducted to make resin multilayer circuit boards that can be supplied at lower cost, suitable for high-density mounting, instead of conventional ceramic multilayer boards. I have.

As such a circuit board, for example, a circuit board having an all-layer inner via hole structure has been proposed (Patent Document 1 below). Since this circuit board is a resin multilayer board using a composite material of an aramid nonwoven fabric reinforcing material and an epoxy resin for an insulator layer, it can be supplied relatively inexpensively. In addition, since an inner via connection method that can connect an arbitrary position of an arbitrary wiring layer with a conductive paste, that is, an all-layer inner via hole structure is employed, the present invention is suitable for high-density mounting.
JP-A-6-268345

  In such a circuit board, it is important to ensure the connection reliability of the inner via. However, there are the following problems regarding the connection reliability of the inner via.

  That is, since the inner via has a different material from that of the insulator layer, it naturally has different physical properties (thermal expansion coefficient, humidity expansion coefficient, etc.), and particularly, the organic resin of the insulator layer having a relatively large thermal expansion coefficient. Due to the mismatch between the material and the inner via material whose main constituent material is a metal with a relatively small coefficient of thermal expansion, "temperature cycling causes tensile stress in the thickness direction inside the inner via material, resulting in excessive stress. Is added, the inner via is destroyed, and the connection reliability is degraded. "

  As a countermeasure against such a problem, as a countermeasure, it is possible to prevent the inner via from being broken by reducing the difference between the physical properties of the constituent materials used for the insulator layer and the inner via. That is, the resin of the insulator layer is filled with an inorganic filler such as silica, so that the resin content of the insulator layer is reduced and the coefficient of thermal expansion is reduced.

  However, the resin of the insulator layer plays a role of firmly bonding the wiring layer and the insulator layer. If the resin in the surface layer of the insulator layer is reduced and the adhesive strength is reduced, the wiring layer is separated. This causes a problem that the components mounted on the component mounting surface are peeled off together with the pads and the like, and cannot be a sufficient solution.

  The present invention has been made in order to solve the above-mentioned problems in the related art, and the wiring layer and the insulator layer have sufficient adhesive strength, and can realize excellent inner via connection reliability. Provided is a circuit board and a method of manufacturing the same.

The circuit board of the present invention has an insulator layer for electrically insulating, and an inner via conductive layer formed in a thickness direction of the insulator layer and electrically connecting upper and lower surfaces of the insulator layer. Body and
A land portion disposed on the upper and lower surfaces of the insulator layer, and electrically connected to the inner via conductor, wherein the insulator layer has an organic resin and a thermal expansion coefficient higher than that of the organic resin. A composite material containing a small material, wherein a surface portion having a high composition ratio of the organic resin and a core portion having a low composition ratio of the organic resin are formed in the order of surface portion / core portion / surface portion;
The core portion is formed of a porous body, and the land portions disposed on the upper and lower surfaces of the insulator layer are buried in the surface portion until the core portions contact the core portion on the upper and lower surfaces of the core portion, and the inner via conductive layer is provided. The body has a thickness substantially equal to the thickness of the core portion.

  Further, the circuit board of the present invention is a circuit board having three or more insulator layers, wherein in at least one of the inner layers, the land portions disposed on the upper and lower surfaces of the insulator layer include the land portions, The upper and lower surfaces of the core portion are embedded in the surface portion until they come into contact with the core portion.

  Next, a first method for manufacturing a circuit board according to the present invention includes forming at least two wiring layers, an insulating layer for electrically insulating the wiring layers, and forming the insulating layer in a thickness direction of the insulating layer. And a method of manufacturing a circuit board having an inner via conductor for electrically connecting the wiring layers to each other, wherein the insulator layer has an organic resin and a thermal expansion coefficient higher than that of the organic resin. A composite material containing a small material, wherein a surface portion having a high composition ratio of the organic resin and a core portion having a low composition ratio of the organic resin are formed in the order of surface portion / core portion / surface portion; When a core portion is made of a porous material, an inner via hole is opened in the thickness direction of the insulator layer to fill the conductive paste, and a metal foil is arranged on both sides of the insulator layer. A convex part at a predetermined part so that The metal foil was placed, and heated and pressed by a hot press from the outside of the metal foil, and the convex portion of the metal foil was pushed until almost in contact with the core portion of the insulator layer, and the thickness of the inner via conductor was reduced. The thickness is substantially equal to the thickness of the core portion, and thereafter, the metal foil is etched to leave the convex portion as a land portion.

  Next, a second method for manufacturing a circuit board according to the present invention includes forming at least two wiring layers, an insulating layer for electrically insulating the wiring layers, and forming the insulating layer in a thickness direction of the insulating layer. And a method of manufacturing a circuit board having an inner via conductor for electrically connecting the wiring layers to each other, wherein the insulator layer has an organic resin and a thermal expansion coefficient higher than that of the organic resin. A composite material containing a small material, wherein a surface portion having a high composition ratio of the organic resin and a core portion having a low composition ratio of the organic resin are formed in the order of surface portion / core portion / surface portion; The core portion is made of a porous body, and an inner via hole is opened in the thickness direction of the insulator layer to fill the conductive paste, so that both sides of the insulator layer match the conductive paste filling portion. Patterned metal foil on predetermined parts The transfer substrate is arranged, and heated and pressed by a hot press from the outside of the transfer substrate, and the metal foil is pushed until almost in contact with the core portion of the insulator layer, and the thickness of the inner via conductor is reduced by the core portion. Characterized in that the thickness is substantially the same as the thickness.

  In the above, the thickness of the inner via conductor is substantially the same as the thickness of the core portion, that the thickness of the inner via conductor is not the same as the thickness of the core portion or not more than 10%, or It means that it is not thicker than 5 μm than the thickness.

  According to the present invention, while holding the wiring layer with an organic resin having excellent adhesiveness, and furthermore, a mismatch in the coefficient of thermal expansion hardly occurs, so that the wiring layer and the insulator layer have a sufficient adhesive strength, and And a circuit board capable of realizing excellent inner via connection reliability and a method of manufacturing the same. Also, since a part of the metal foil is buried until it comes into contact with the core layer of the insulating layer, the conductive paste part can be selectively compressed, and a circuit board which enables stable interlayer connection and its manufacture. We can provide a method.

  In the configuration of the circuit board of the present invention, the material having a smaller coefficient of thermal expansion than the organic resin is preferably a woven fabric of inorganic fibers. According to this preferred example, in addition to sufficient adhesive strength and excellent inner via connection reliability, the rigidity of the entire circuit board can be increased, and a circuit board excellent in mechanical strength can be realized. In this case, the woven fabric is preferably a glass woven fabric.

  In the configuration of the circuit board of the present invention, the material having a smaller thermal expansion coefficient than the organic resin is preferably a nonwoven fabric of inorganic fibers. According to this preferred example, a circuit board having excellent mechanical strength in addition to sufficient adhesive strength and excellent inner via connection reliability can be realized at low cost. In this case, the nonwoven fabric is preferably a glass nonwoven fabric.

  Further, in the configuration of the circuit board of the present invention, it is preferable that the material having a smaller thermal expansion coefficient than the organic resin is an organic film. According to this preferred example, in addition to sufficient adhesive strength and excellent inner via connection reliability, an insulator layer having a uniform thickness can be easily obtained, and a circuit board with easy impedance control can be realized. it can. In this case, the organic film is selected from the group consisting of polyimide, BCB (benzocyclobutene), PTFE (polytetrafluoroethylene), aramid, PBO (polyparaphenylenebenzobisoxazole), and wholly aromatic polyester. It is preferably at least one organic film.

  In the configuration of the circuit board of the present invention, it is preferable that the material having a smaller thermal expansion coefficient than the organic resin is an inorganic filler. According to this preferred example, in addition to sufficient adhesive strength and excellent inner via connection reliability, a circuit board having properties such as thermal conductivity can be easily realized by selecting the type and composition ratio of the inorganic filler. be able to. In this case, the inorganic filler is preferably at least one inorganic filler selected from the group consisting of aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.

  Further, in the configuration of the circuit board of the present invention, it is preferable that the material having a smaller thermal expansion coefficient than the organic resin is a porous body. According to this preferred example, in addition to sufficient adhesive strength and excellent inner via connection reliability, the rigidity of the entire circuit board can be increased, and a circuit board excellent in mechanical strength can be realized. In this case, it is preferable that the core portion is formed by impregnating the porous body made of an organic resin with a composition of an inorganic filler and an organic resin. In this case, the porous body made of the organic resin is a porous body made of a fluororesin, and the inorganic filler is made of aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride. And at least one inorganic filler selected from the group consisting of Fluororesins have a low dielectric constant and are suitable for high-frequency circuits.

  In the configuration of the circuit board of the present invention, the organic resin may be an epoxy resin, a polyimide resin, a cyanate ester resin, a phenol resole resin, a wholly aromatic polyester resin, a PPE (polyphenylene ether) resin, a bismaleimide triazine resin, It is preferably at least one organic resin selected from the group consisting of fluororesins. In this case, it is preferable that the organic resin contains at least one inorganic filler selected from the group consisting of aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.

  In the configuration of the circuit board of the present invention, it is preferable that the inner via is made of a composite material of a conductive filler and an organic resin. Further, in this case, the conductive filler is at least one metal selected from the group consisting of gold, silver, copper, nickel, palladium, lead, tin, indium and bismuth, or an alloy or a mixture thereof. Preferably, the filler is

  Hereinafter, the present invention will be described more specifically with reference to embodiments.

  FIG. 1 is a schematic sectional view showing a circuit board (double-sided circuit board) of the present invention. As shown in FIG. 1, a circuit board of the present invention includes an insulator layer 101, an inner via 102 formed in the insulator layer 101 and containing a metal as a main component, and a land 103 embedded in the insulator layer 101. It consists of: Here, the insulator layer 101 includes a surface portion 105 made of an organic resin and a core portion 106, and a surface 104 of the land 103 facing the inner via 102 is substantially flush with an interface between the surface portion 105 and the core portion 106. It is in. The thickness of the inner via 102 is substantially the same as the thickness of the core portion 106. The thickness of the core is preferably in the range of 5 to 200 μm. The resin content of the core is preferably in the range of 0 to 50% by weight.

  The surface portion 105 of the insulator layer 101 is made of an organic resin layer, and has a role of holding and bonding the land 103. The thickness of the organic resin layer is preferably in the range of 2 to 50 μm. In addition, even if an inorganic filler is dispersed in an organic resin or a material having a small coefficient of thermal expansion of the core portion 106 is mixed, if a sufficient adhesive strength can be developed, the surface portion of the circuit board of the present invention can be used. can do.

  In FIG. 1, the through-hole filled with the inner via 102 (conductor) has a tapered shape with a wide upper side when viewed from a cross section, and is filled with a conductive paste from a wider side. If the conductive paste is filled from the wide opening on the upper side, the filling is easy. In order to form an opening having a wide upper side as shown in FIG. 1, for example, when the core portion 106 is a glass cloth impregnated with resin, one to three shots are irradiated using a carbon dioxide laser having a wavelength of 9.4 μm or 10.6 μm. Can be formed.

  Next, the organic resin and the constituent materials of the wiring layer and the inner via which can be used in the circuit board of the present invention will be described.

(A) Organic Resin As the organic resin of the present invention, epoxy resins, polyimide resins, cyanate ester resins, phenol resole resins, wholly aromatic polyester resins, PPE (polyphenylene ether) resins, bismaleimide triazine resins, fluororesins, etc. A plastic or thermosetting organic resin can be used. Further, a composition in which an inorganic filler such as aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), or silicon nitride is added to these organic resins can also be used. When a resin composition containing an inorganic filler is used, the amount of the inorganic filler is desirably 70% by volume or less. If the amount of the inorganic filler is larger than 70% by volume, the amount of the organic resin in the resin composition becomes insufficient to hold the wiring layer, and the adhesive strength between the wiring layer and the resin composition becomes extremely small. .

(B) Constituent Material of Inner Via The inner via of the present invention can be constituted by a conductive resin composition containing a conductive filler.

  As the conductive filler, a filler made of at least one metal selected from gold, silver, copper, nickel, palladium, lead, tin, indium, and bismuth, or an alloy or a mixture thereof can be used. Further, a coat filler obtained by coating the above-mentioned metal or alloy on a ball made of the above-mentioned metal or alloy, an oxide such as alumina or silica, or an organic synthetic resin can also be used.

  The shape is not particularly limited, and a powder, a fibrous filler, a granulated powder, a spherical ball, or a mixture thereof can be used.

  As a resin used as a binder of the resin composition, a liquid epoxy resin, a polyimide resin, a cyanate ester resin, a phenol resole resin, or the like can be used. Epoxy resins include glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, alicyclic epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin and the like. An epoxy resin containing two or more epoxy groups can be used.

  If necessary, additives such as solvents and dispersants such as butyl cellosolve, ethyl cellosolve, butyl carbitol, ethyl carbitol, butyl carbitol acetate, ethyl carbitol acetate and α-terpineol can also be contained. .

  The constituent material of the inner via is not limited to only the conductive composition. For example, the inner via of the circuit board of the present invention can be formed by filling a metal via post or a metal ball formed by a wet process such as plating or a vacuum process such as sputter deposition.

(C) Wiring Layer A metal foil such as a copper foil can be used for the wiring layer of the circuit board of the present invention. If a copper foil that is at least thicker than the thickness of the surface portion 105 of the insulator layer 101 is used, there is no limitation on the thickness, and a copper foil having a thickness of 3 to 35 μm used for a normal circuit board can be used. Of course, a thicker metal foil can also be used. The depth at which the metal foil is embedded in the surface of the electrically insulating layer is preferably about 5 to 50% of the thickness of the metal foil.

  As the metal foil, a so-called metal foil with a carrier in which a metal foil is formed on a support substrate (carrier) can be used. As an example of the metal foil with a carrier, a metal foil obtained by laminating a copper foil on an aluminum carrier via a release layer is commercially available. When used in the embodiment of the present invention, the copper foil is preliminarily patterned by etching with an aqueous solution of iron chloride, an aqueous solution of ammonium persulfate, and the like, and the wiring pattern is laminated so as to be embedded in the insulator layer 101. It can be removed by etching with hydrochloric acid or the like. When a metal foil with a carrier is used, a structure in which the land 103 does not protrude from the surface of the insulator layer 101 can be achieved by selecting the thickness of the metal foil. In other words, if the surface resin layer is made of a metal foil having substantially the same thickness, a structure in which the land does not protrude from the surface of the insulator layer can be obtained. If a metal foil thicker than the surface resin layer is used, the land protrudes. Can be done.

  Such a method of transferring a wiring pattern formed on a support substrate to an insulating base material to create a circuit board is called a transfer method. A material in which a wiring pattern is formed on a carrier is called a transfer forming material. The metal foil with a carrier used for the transfer method is not limited to the combination of the aluminum carrier and the metal foil described above. For example, a metal foil may be formed on a resin substrate (carrier). The carrier can be removed by sandblasting or the like. Alternatively, the carrier and the metal foil for forming a wiring pattern may be temporarily bonded with an adhesive sheet to form a metal foil with a carrier. For example, if "Riba Alpha" (trade name: manufactured by Nitto Denko Corporation), which easily loses adhesive strength due to heat, is used as the adhesive sheet, the carrier can be easily removed by heating at about 150 ° C. after forming the wiring board.

  As another method for forming a wiring layer, there is a method of forming a wiring pattern by half-etching a normal metal foil (half-etching method). Hereinafter, the case where a copper foil is used as the metal foil will be specifically described with reference to an example.

  First, a wiring pattern is formed by etching the copper foil from one side to about half the thickness with an aqueous solution of iron chloride, an aqueous solution of ammonium persulfate, or the like. Next, after laminating the wiring pattern so as to be embedded in the insulator layer 101, the remaining copper foil is patterned by etching with an aqueous solution of iron chloride, an aqueous solution of ammonium persulfate, or the like. By using the half-etching method, a structure in which the land 103 protrudes from the surface of the insulator layer 101 can be obtained. Therefore, the half etching method is suitable for manufacturing a multilayer wiring board.

  Further, the wiring layer of the present invention may be formed by a wet process such as plating or a vacuum process such as sputter deposition.

(First Embodiment)
FIG. 2 is a schematic sectional view showing a circuit board (double-sided circuit board) according to the first embodiment of the present invention. As shown in FIG. 2, the circuit board according to the present embodiment includes an insulator layer 201 made of an organic resin and a woven fabric of inorganic fibers (a material having a smaller coefficient of thermal expansion than the organic resin). , And a land 203 buried in the insulator layer 201. Here, the insulator layer 201 includes a surface portion 205 mainly composed of an organic resin (having a high organic resin composition ratio) and a core portion mainly composed of a woven fabric of inorganic fibers (a low organic resin composition ratio). The surface 204 of the land 203 facing the inner via 202 is substantially flush with the interface between the surface portion 205 and the core portion 206. The thickness of the inner via 202 is substantially the same as the thickness of the core portion 206.

  Next, the circuit board according to the present embodiment will be described using an example in which a glass epoxy base material is used for the insulator layer 201, a composition of copper and epoxy resin is used for the constituent material of the inner via 202, and copper foil is used for the wiring layer. This will be described more specifically.

  First, as shown in FIG. 3A, a glass epoxy substrate in a prepreg state (semi-cured state) (hereinafter referred to as “glass epoxy prepreg”. The thickness of the core layer is 100 μm, and the thickness of the resin layers on both surfaces is 10 μm). Is formed at the position of, and the through-hole is filled with a paste-like copper-epoxy resin composition 209 by a printing method or the like.

  The through-hole can be formed by a normal circuit board drilling method. Examples of the drilling method include a mechanical drilling method using a drill or a puncher, a laser drilling method using a carbon dioxide laser, an excimer laser, a YAG laser, and the like. Among them, in order to form a tapered hole as shown in FIG. 3A, one to three shots are irradiated from the upper side using a carbon dioxide gas laser having a wavelength of 9.4 μm or 10.6 μm.

  Next, a wiring layer is formed by the half etching method described above. First, a wiring pattern is formed by etching the copper foil 210 from one surface to about half the thickness with an aqueous solution of iron chloride, an aqueous solution of ammonium persulfate, or the like (FIG. 3B).

Next, as shown in FIG. 3B, on both sides of the glass epoxy prepreg 208 filled with the paste-like copper-epoxy resin composition 209, the portions where the wiring patterns are formed face the glass epoxy prepreg 208. The copper foil 210 is overlaid and heated and pressed by a hot press. The conditions are, for example, a heating temperature of 180 ° C. to 250 ° C., a pressure of 30 to 200 kgf / cm ² , and a heating time of 0.5 to 2 hours.

  In this step, curing of the epoxy resin, which is a thermosetting resin, and adhesion between the glass epoxy prepreg 208 and the wiring pattern can be achieved. The glass epoxy base material which is the glass epoxy prepreg 208 after the epoxy resin is cured is the insulator layer. Also, in this step, the copper foil 210 has a high composition ratio between the surface portion of the insulator layer and the glass woven fabric where the composition ratio of the epoxy resin is high (the composition ratio of the epoxy resin is low). It is embedded in the insulator layer so as to be substantially the same as the interface of the core portion of the (low) insulator layer, and electrical conduction between the wiring layers by the inner via 209 is achieved (FIG. 2).

  Next, as shown in FIG. 3C, a wiring pattern is formed on an outer surface portion of the copper foil 210 to form a land 211. Thus, the double-sided circuit board 212 (FIG. 3D) is completed.

  The multilayer circuit board can be manufactured as follows.

  That is, as shown in FIGS. 3D to 3E, a glass epoxy prepreg 213 filled with a paste-like copper-epoxy resin composition is superimposed on both sides of the double-sided circuit board 212, and a wiring is formed on the outside thereof by half etching. The copper foil 214 on which the putter is formed is stacked, heated and pressed by a hot press or the like, and then patterned to produce the uppermost copper foil 214.

  The insulator layer of the present embodiment is not limited to a glass epoxy base material, but may be any composite material composed of an organic resin and a woven fabric of inorganic fibers. For the surface portion mainly composed of the organic resin and the core portion mainly composed of the woven fabric, a composite material having a configuration in which the surface portion / core portion / surface portion is laminated in this order can be used.

  As the woven cloth, a woven cloth made of an inorganic fiber such as a glass fiber can be used.

  When a thermoplastic resin is used as the organic resin, the present embodiment is performed by softening the thermoplastic resin in the hot pressing step and forming the inner via, the insulator layer, and the wiring pattern into a desired shape and state. A circuit board in the form is obtained.

(Second embodiment)
FIG. 4 is a schematic sectional view showing a circuit board (double-sided circuit board) according to the second embodiment of the present invention. As shown in FIG. 4, the circuit board according to the present embodiment includes an insulator layer 301 made of an organic resin and a nonwoven fabric of an inorganic fiber (a material having a smaller coefficient of thermal expansion than the organic resin); It is composed of the formed inner via 302 and a land 303 buried in the insulator layer 301. Here, the insulator layer 301 includes a surface portion 305 containing an organic resin as a main component (the composition ratio of the organic resin is high) and a core portion 306 containing a nonwoven fabric of inorganic fibers as a main component (the composition ratio of the organic resin is low). The surface 304 of the land 303 facing the inner via 302 is substantially flush with the interface between the surface portion 305 and the core portion 306. The thickness of the inner via 302 is substantially the same as the thickness of the core portion 306.

  The circuit board of the present embodiment is a composite material in which an insulator layer is composed of an organic resin and a nonwoven fabric of inorganic fibers, and a surface portion mainly composed of the organic resin and a core mainly composed of the nonwoven fabric. Except for using a composite material in which the portions are laminated in the order of surface portion / core portion / surface portion, it can be manufactured in the same manner as in the first embodiment.

  As the nonwoven fabric, a nonwoven fabric made of an inorganic fiber such as a glass fiber can be used.

(Third embodiment)
FIG. 5 is a schematic sectional view showing a circuit board (double-sided circuit board) according to the third embodiment of the present invention. As shown in FIG. 5, the circuit board according to the present embodiment is formed with an insulator layer 401 made of an organic resin and an organic film (a material having a smaller thermal expansion coefficient than the organic resin), and formed in the insulator layer 401. And a land 403 buried in the insulator layer 401. Here, the insulator layer 401 includes a surface portion 405 containing an organic resin as a main component (the composition ratio of the organic resin is high) and a core portion 406 containing the organic film as a main component (the composition ratio of the organic resin is low). The surface 404 of the land 403 facing the inner via 402 is substantially flush with the interface between the surface portion 405 and the core portion 406. The thickness of the inner via 402 is substantially the same as the thickness of the core portion 406.

  The circuit board of the present embodiment is a composite material in which an insulator layer is composed of an organic resin and an organic film, and has a surface portion mainly containing the organic resin and a core portion mainly containing the organic film. Can be manufactured in the same manner as in the first embodiment, except that a composite material having a structure in which is laminated in the order of surface portion / core portion / surface portion is used.

  The organic film used for the core layer is made of a synthetic resin such as polyimide, BCB (benzocyclobutene), PTFE (polytetrafluoroethylene), aramid, PBO (polyparaphenylenebenzobisoxazole) or wholly aromatic polyester. An organic material sheet or film, or a film or sheet of an inorganic insulating material such as ceramic can be used. For the resin layers formed on both layers, an epoxy resin, a polyimide resin, or the like can be used.

(Fourth embodiment)
FIG. 6 is a schematic sectional view showing a circuit board (double-sided circuit board) according to the fourth embodiment of the present invention. As shown in FIG. 6, the circuit board of the present embodiment is formed in an insulator layer 501 made of an organic resin and an inorganic filler (a material having a smaller coefficient of thermal expansion than the organic resin), and formed in the insulator layer 501. And a land 503 buried in the insulator layer 501. Here, the insulator layer 501 includes a surface portion 505 containing an organic resin as a main component (the composition ratio of the organic resin is high) and a core portion 506 containing an inorganic filler as a main component (the composition ratio of the organic resin is low). The surface 504 of the land 503 facing the inner via 502 is substantially flush with the interface between the surface portion 505 and the core portion 506. The thickness of the inner via 502 is substantially the same as the thickness of the core portion 506.

  The circuit board of the present embodiment is a composite material in which an insulator layer is composed of an organic resin and an inorganic filler, and has a surface portion mainly containing the organic resin and a core portion mainly containing the inorganic filler. Can be manufactured in the same manner as in the first embodiment, except that a composite material having a structure in which is laminated in the order of surface portion / core portion / surface portion is used.

  As the inorganic filler, aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), silicon nitride, or the like can be used.

(Fifth embodiment)
FIG. 7 is a schematic sectional view showing a circuit board (double-sided circuit board) according to the fifth embodiment of the present invention. As shown in FIG. 7, the circuit board according to the present embodiment has an insulator layer 601 made of an organic resin and a porous body (a material having a smaller thermal expansion coefficient than the organic resin), and is formed in the insulator layer 601. And a land 603 buried in the insulator layer 601. Here, the insulator layer 601 has a surface portion 605 mainly composed of an organic resin (having a high organic resin composition ratio) and a core portion 606 mainly composed of a porous material (having a low organic resin composition ratio). The surface 604 of the land 603 facing the inner via 602 is substantially flush with the interface between the surface portion 605 and the core portion 606. The thickness of the inner via 602 is substantially the same as the thickness of the core portion 606.

  The circuit board of the present embodiment is a composite material in which an insulator layer is composed of an organic resin and a porous body, and has a surface portion mainly composed of the organic resin and the porous body mainly. Except for using a composite material in which a core portion is laminated in the order of a surface portion / core portion / surface portion, it can be manufactured in the same manner as in the first embodiment.

  As the core portion mainly composed of a porous material, a sheet or the like in which a porous material such as a fluororesin is impregnated with the above-described organic resin and an inorganic filler is added in some cases can be used.

(Evaluation test)
The connection reliability and the adhesive strength of the wiring pattern of the circuit boards manufactured according to the first to fifth embodiments were evaluated. The connection reliability was evaluated by an acceleration test and a pressure cooker test in which the sample was left in saturated steam at 121 ° C. and 0.2 MPa. The evaluation of the adhesive strength was performed by a 90-degree peel test of a 1 cm wiring pattern. As a constituent material of the inner via, a composition of copper powder and an epoxy resin was used. Copper powder is spherical copper powder (85 mass%) having an average particle size of 5 μm, epoxy resin composition (15 mass%) is a mixture of diglycidyl dimer acid epoxy resin and bisphenol F epoxy resin, and amine adduct as a curing agent. 15 parts of a powder hardener (Ajinomoto Amicure MY-24). The thermal expansion coefficient of this composition is 20 ppm.

  In the first embodiment, a glass woven fabric (thickness: 90 μm, thermal expansion coefficient: 5 ppm) is impregnated with an epoxy resin (thermal expansion coefficient: 60 ppm) as the insulator layer 201, and the epoxy resin layers on the surface portion 205 are each separated. A glass epoxy substrate having a thickness of 10 μm was used. In addition, an electrolytic copper foil having a thickness of 18 μm was used as the wiring layer. The upper hole diameter of the inner via 202 is 200 μm, and the lower hole diameter is 180 μm (Example 1).

  Examples 2 to 4 are the same as Example 1 except that the thickness of the glass woven fabric was 50 μm (Example 2), 150 μm (Example 3), and 200 μm (Example 4), respectively.

  In the third embodiment, as the insulator layer 401, a polyimide film (thickness 12.5 μm, thermal expansion coefficient: 80 ppm) is formed on the core portion 406, and a polyimide adhesive (thickness 5 μm, thermal expansion coefficient: 190 ppm) is formed on the surface portion 405. ) Was used. Further, an electrolytic copper foil having a thickness of 9 μm was used as the wiring layer. The upper hole diameter of the inner via 402 is 50 μm, and the lower hole diameter is 45 μm (Example 5).

  Examples 6 to 8 are the same as Example 5 except that the thickness of the polyimide film was 3 μm (Example 6), 9 μm (Example 7), and 25 μm (Example 8), respectively.

  In the fourth embodiment, an alumina epoxy composite material (thickness: 50 μm, thermal expansion coefficient: 18 ppm) in which an alumina filler (70% by volume) having a particle diameter of 10 μm is dispersed in an epoxy resin is used as the insulator layer 501 in the core portion 506. An epoxy resin (thickness: 5 μm, coefficient of thermal expansion: 60 ppm) was used for the surface portion 505. Further, an electrolytic copper foil having a thickness of 9 μm was used as the wiring layer. The upper hole diameter of the inner via 502 is 150 μm, and the lower hole diameter is 140 μm (Example 9).

  Examples 10 to 12 are the same as Example 9 except that the thickness of the alumina epoxy composite material was 20 μm (Example 10), 70 μm (Example 11), and 100 μm (Example 12).

  In the fifth embodiment, a composite material (35 μm in thickness, in which a core sheet 606 is impregnated with a composition obtained by dispersing silica in an epoxy resin on a porous sheet of a fluororesin (polytetrafluoroethylene)) is used as the insulator layer 601. Epoxy resin (thickness: 5 μm, thermal expansion coefficient: 60 ppm) was used for the surface portion 605. Further, an electrolytic copper foil having a thickness of 9 μm was used as the wiring layer. The upper hole diameter of the inner via 602 is 50 μm, and the lower hole diameter is 45 μm (Example 13).

  In Examples 14 to 16, the thickness of the composite material in which the porous sheet was impregnated with the composition in which the silica was dispersed in the epoxy resin was 10 μm (Example 14), 20 μm (Example 15), and 50 μm (Example 16). Except for this, the configuration is the same as that of the thirteenth embodiment.

  In the first embodiment, the insulating layer 201 is impregnated with a resin composition obtained by dispersing a silica filler (particle diameter: 3 μm) in an epoxy resin in a glass woven cloth (thickness: 90 μm, thermal expansion coefficient: 5 ppm). Then, a filler-containing glass epoxy substrate having an epoxy resin layer of 5 μm on the surface portion 205 was used. The content of the silica filler in the surface portion 205 was 5% by volume (Example 17), 20% by volume (Example 18), 50% by volume (Example 19), and 70% by volume (Example 20).

As a comparison with Examples 1 to 20, a circuit board having a structure as shown in FIG. 8 was manufactured using the same material as the circuit board of each embodiment, and subjected to a test. (Comparative Examples 1 to 20)
In the circuit board shown in FIG. 8, the surface 704 of the land 703 buried in the insulator layer 701 facing the inner via 702 is inside the surface layer 705, and the thickness of the inner via 702 is larger than the thickness of the core portion 706. Is also growing.

  Further, as a comparative example with respect to Examples 17 to 20, a circuit board having the same configuration as Examples 17 to 20 and having a silica filler content of 85% by volume was manufactured (Comparative Example 21).

  Table 1 below shows the evaluation results.

  In the pressure cooker test, the evaluation was evaluated as × when the wiring circuit including the inner via was disconnected after 168 hours, and as ○ when the change in the resistance value was within 10%. The peel strength was rated as ○ when it was 15 N or more, and as x when it was less than 15 N.

  As can be seen from the above (Table 1), according to the first to fifth embodiments of the present invention, it is possible to realize a circuit board having excellent connection reliability and excellent bonding strength of a wiring pattern. .

  In the case where the other insulator layer material described in the present embodiment is used, as in the case of Examples 1 to 20, the circuit has excellent connection reliability and excellent bonding strength of the wiring pattern. A substrate can be realized.

(Sixth embodiment)
9A to 9E are cross-sectional views illustrating a method of manufacturing a circuit board according to the present embodiment in the order of steps.

  First, as shown in FIG. 9A, a metal film 16 (Ni) was formed on a thick copper foil 13 (35 μm) by plating, vapor deposition, sputtering, or the like, and a resist 14 was formed thereon. Next, after etching the metal foil and the thick copper foil to a predetermined thickness, the resist 14 was removed to obtain a thick copper foil 17 with a metal film shown in FIG. 9B. As the metal film, a material made of at least one of Au, Ag, Cr, Pb, Zn, Ni, and Sn may be used.

  Next, as shown in FIG. 9C, thick copper foils 17 with a metal film were arranged on both surfaces of the filled prepreg base material 10. Thereafter, as shown in FIG. 9D, a predetermined pressure was applied to the prepreg base material at a predetermined curing temperature by a press machine to completely bond the prepreg base material, and a copper foil was patterned to obtain a double-sided substrate 18 shown in FIG. 9E.

  Thereafter, as in the third embodiment, sequential multi-layering is possible, but is omitted.

  It is also effective to use a thick copper foil which has been subjected to a blackening treatment, a chromate treatment, a roughening treatment, or the like in a portion removed by etching at the time of forming FIG. 9B.

  As described above, according to the embodiment of the present invention, in a circuit board in which electrical connection between layers is performed using a conductive paste, a through hole is formed in a prepreg base material, and a conductive paste is filled. In a circuit board that electrically connects between copper foils arranged on both sides of the prepreg base material by the conductive paste by arranging the foils by hot pressing, in the case of a glass epoxy base material or the like, the compressibility is low and a stable interlayer is provided. Although there was a problem that the connection could not be secured, it was necessary to perform a half-etching on the thick copper foil to provide a convex portion, and to perform a stable interlayer connection by compressing the conductive paste portion with the protruding portion. Can be.

  In the sequential method in which the inner layer core is sequentially multilayered, by providing convex portions on both surfaces of the inner layer core, it is possible to compress the conductive paste by the convex portions in the next layer. Electrolytic copper foil (for example, GT-GLD 18 μm manufactured by Furukawa Circuit Wheel) can be used.

  Therefore, a glass epoxy substrate FR-4 (manufactured by Hitachi Chemical Co., Ltd.) having a low compressibility in all layers can be used. That is, it is possible to configure the base material according to each performance such as high bandwidth and high reliability.

  Alternatively, at the time of etching, a blackening process, a chromate process, or the like is performed on a portion other than the convex portion so that the metal filler containing the conductive paste portion and the copper foil are easily adhered to each other. In the performed part, the adhesive strength of the copper foil can be strengthened.

  Further, when performing the half etching, the adhesive strength can be strengthened in the same manner as described above by increasing the surface roughness of the copper foil portion other than the projections. And it is possible to arbitrarily commercialize products in accordance with customer requirements.

  In the present embodiment, an example of a wiring board in which a convex portion formed by half etching becomes a land as a metal foil has been described. However, the circuit wiring of the present invention can be manufactured in the same manner by using the sacrifice substrate to form a land pattern by completely etching the pattern wiring.

(Seventh embodiment)
10A to 10E are schematic cross-sectional views illustrating a circuit board (double-sided circuit board) according to the seventh embodiment of the present invention. The circuit board according to the present embodiment includes an insulator layer 201 made of an organic resin and a woven fabric of an inorganic fiber (a material having a smaller thermal expansion coefficient than the organic resin), and an inner via 202 formed in the insulator layer 201. And a land 203 buried in the insulator layer 201. Here, the insulator layer 201 includes a surface portion 205 mainly composed of an organic resin (having a high organic resin composition ratio) and a core portion mainly composed of a woven fabric of inorganic fibers (a low organic resin composition ratio). The surface 204 of the land 203 facing the inner via 202 is substantially flush with the interface between the surface portion 205 and the core portion 206. The thickness of the inner via 202 is substantially the same as the thickness of the core portion 206.

  Next, the circuit board according to the present embodiment will be described using an example in which a glass epoxy base material is used for the insulator layer 201, a composition of copper and epoxy resin is used for the constituent material of the inner via 202, and copper foil is used for the wiring layer. This will be described more specifically.

  First, as shown in FIG. 10A, a glass epoxy prepreg 208 in a prepreg state (semi-cured state) (core layer thickness is 100 μm, resin layers on both surfaces are 10 μm each) has a wavelength of 9. Using a 4 μm or 10.6 μm carbon dioxide laser, irradiating 1 to 3 shots to form a through hole, and paste the copper-epoxy resin composition 209 from the wide opening side of the through hole by a printing method or the like. Fill.

  Next, as the transfer forming material 803, a carrier 801 was used in which a copper foil 802 having a thickness of 18 μm was adhered to a surface of an aluminum plate having a thickness of 50 μm. In this case, the land protrudes from the glass epoxy prepreg base material 208, and the protruding portion can be embedded in the next insulating layer to be laminated. This transfer material 803 is arranged on both sides of the glass epoxy prepreg base material 208 as shown in FIG. 10B.

Next, heat and pressure are applied by a hot press. The conditions are, for example, a heating temperature of 180 ° C. to 250 ° C., a pressure of 30 to 200 kgf / cm ² , and a heating time of 0.5 to 2 hours.

  In this step, the epoxy resin, which is a thermosetting resin, can be cured and the glass epoxy prepreg 208 and the wiring pattern 802 can be bonded. The glass epoxy base material which is the glass epoxy prepreg 208 after the epoxy resin is cured is the insulator layer. Further, in this step, the copper foil 802 has a high composition ratio of the surface of the insulator layer on the side where the wiring pattern is formed and the insulating layer having a high composition ratio of the epoxy resin and a high composition ratio of the glass woven fabric (the composition ratio of the epoxy resin is high). It is embedded in the insulator layer so as to be substantially the same as the interface of the core portion of the (lower) insulator layer, and electrical conduction between the wiring layers by the inner via 209 can be achieved (FIG. 10C). Next, the entire aluminum carrier 801 is removed by etching with hydrochloric acid. Thus, the double-sided circuit board 212 (FIG. 10D) is completed.

  The multilayer circuit board can be manufactured as follows.

  That is, as shown in FIG. 10D to FIG. 10E, a glass epoxy prepreg 213 filled with a paste-like copper-epoxy resin composition is stacked on both sides of the double-sided circuit board 212 described above, and further outside the same as above. After the transfer materials 803 are stacked and heated and pressed by a hot press or the like, the aluminum carrier 801 is removed.

1 is a schematic cross-sectional view illustrating a circuit board according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a circuit board according to the first embodiment of the present invention. FIGS. 4A to 4E are cross-sectional views illustrating a method of manufacturing the circuit board according to the first embodiment of the present invention. It is a cross section showing the circuit board in a 2nd embodiment of the present invention. It is a cross section showing a circuit board in a 3rd embodiment of the present invention. It is a cross section showing a circuit board in a 4th embodiment of the present invention. It is a cross section showing a circuit board in a 5th embodiment of the present invention. FIG. 4 is a schematic cross-sectional view illustrating a circuit board of a comparative example. FIGS. 13A to 13E are cross-sectional views showing the steps of the method for manufacturing a circuit board according to the sixth embodiment of the present invention. FIGS. 13A to 13E are cross-sectional views showing the steps of the method for manufacturing a double-sided circuit board according to the seventh embodiment of the present invention.

Explanation of reference numerals

101,201,301,401,501,601,701 insulator layer
102,202,302,402,502,602,702 Inner via
103,203,303,403,503,603,703 Land
104,204,304,404,504,604,704 Surface in contact with inner land of land
105,205,305,405,505,605,705 Surface part
106,206,306,406,506,606,706 core part
208,213 Glass epoxy prepreg
209 Inner Via
210,214 Copper foil
211 Land
212 Double-sided circuit board

Claims (24)

An insulator layer for electrically insulating;
An inner via conductor formed in a thickness direction of the insulator layer, and electrically connecting upper and lower surfaces of the insulator layer;
A land portion disposed on the upper and lower surfaces of the insulator layer and electrically connected to the inner via conductor,
The insulator layer is an organic resin, a composite material including a material having a smaller coefficient of thermal expansion than the organic resin,
A surface portion having a high composition ratio of the organic resin and a core portion having a low composition ratio of the organic resin are formed in the order of surface portion / core portion / surface portion,
The core portion is made of a porous body,
The land portions disposed on the upper and lower surfaces of the insulator layer are buried in the surface portion until the upper and lower surfaces of the core portion contact the core portion,
A circuit board wherein the thickness of the inner via conductor is substantially the same as the thickness of the core portion.   In a circuit board having three or more insulator layers, in at least one of the inner layers, the land portions disposed on the upper and lower surfaces of the insulator layer are formed on the upper and lower surfaces of the core portion by the core. The circuit board according to claim 1, wherein the circuit board is buried in the surface portion until it comes into contact with the portion.   The circuit board according to claim 1, wherein an embedding depth of the land is in a range of 2 to 50 μm.   The circuit board according to claim 1, wherein the land portion protrudes from a surface portion of the organic resin.   The circuit board according to claim 4, wherein a protruding length of the land portion is in a range of 2 to 50 μm.   The circuit board according to claim 1, further comprising an inorganic filler in the core portion.   The circuit board according to claim 6, wherein the inorganic filler is at least one kind of filler selected from aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.   The circuit board according to claim 1, wherein the porous body is made of a fluororesin.   The circuit board according to claim 1, wherein the porous body is impregnated with a composition of an inorganic filler and an organic resin.   The circuit board according to claim 9, wherein the inorganic filler is at least one filler selected from aminium hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.   The organic resin is at least one resin selected from an epoxy resin, a polyimide resin, a cyanate ester resin, a phenol resole resin, a wholly aromatic polyester resin, a PPE (polyphenylene ether) resin, a bismaleimide triazine resin and a fluororesin. Item 2. The circuit board according to item 1.   The circuit board according to claim 11, wherein the organic resin further contains at least one filler selected from aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.   The circuit board according to claim 1, wherein the inner via conductor is made of a composition of a conductive filler and an organic resin.   The conductive filler according to claim 13, wherein the filler is at least one metal selected from gold, silver, copper, nickel, palladium, lead, tin, indium and bismuth, or an alloy or mixture thereof. Circuit board.   2. The circuit board according to claim 1, wherein the through hole filled with the inner via conductor has a tapered shape when viewed from a cross section, and is filled with the conductor from a wider side. 3. An insulator layer for electrically insulating;
An inner via conductor formed in a thickness direction of the insulator layer, and electrically connecting upper and lower surfaces of the insulator layer;
A land portion arranged on the upper and lower surfaces of the insulator layer and electrically connected to the inner via conductor, and a method of manufacturing a circuit board comprising:
The insulator layer is a composite material including an organic resin and a material having a smaller coefficient of thermal expansion than the organic resin, and a surface portion having a high composition ratio of the organic resin and a core portion having a low composition ratio of the organic resin. Are formed in the order of surface portion / core portion / surface portion,
The core portion is made of a porous body,
Fill the conductive material by opening an inner via hole in the thickness direction of the insulator layer,
When arranging the metal foil on both sides of the insulator layer, arrange a metal foil provided with a convex portion in a predetermined portion to match the conductive material filled portion of the inner via hole,
Heating and pressurizing with a hot press from the outside of the metal foil, pushing the convex portion of the metal foil until it comes into contact with the core portion of the insulator layer, and making the thickness of the inner via conductor substantially the same as the thickness of the core portion. ,
After that, the metal foil is etched to leave the convex portion as a land portion,
A method for manufacturing a circuit board.   The method according to claim 16, wherein the convex portion of the metal foil is formed by patterning by etching.   The metal foil is a copper foil, and a rust-preventive treatment selected from a blackening treatment and a chromate treatment is performed on a concave portion removed by etching of a thick metal foil having a pattern formed by etching to a predetermined thickness. Of manufacturing a circuit board.   The method for manufacturing a circuit board according to claim 16, wherein a roughening process is performed on the recesses removed by etching the thick metal foil on which the pattern is formed by etching to a predetermined thickness.   17. The method according to claim 16, wherein the inner via hole has a tapered shape when viewed from a cross section, and is filled with a conductive material from a wider side.   21. The method for manufacturing a circuit board according to claim 16, wherein the conductive substance is a conductive paste. An insulator layer for electrically insulating;
An inner via conductor formed in a thickness direction of the insulator layer, and electrically connecting upper and lower surfaces of the insulator layer;
A land portion arranged on the upper and lower surfaces of the insulator layer and electrically connected to the inner via conductor, and a method of manufacturing a circuit board comprising:
The insulator layer is a composite material including an organic resin and a material having a smaller coefficient of thermal expansion than the organic resin, and a surface portion having a high composition ratio of the organic resin and a core portion having a low composition ratio of the organic resin. Are formed in the order of surface portion / core portion / surface portion,
The core portion is made of a porous body,
Fill the conductive material by opening an inner via hole in the thickness direction of the insulator layer,
On both sides of the insulator layer, a transfer substrate having a metal foil patterned on a predetermined portion is arranged so as to match the conductive material filling portion of the inner via hole,
A circuit that heats and presses with a hot press from the outside of the transfer base material and pushes the metal foil into contact with the core portion of the insulator layer until the thickness of the inner via conductor is substantially equal to the thickness of the core portion. Substrate manufacturing method.   23. The circuit board manufacturing method according to claim 22, wherein the inner via hole has a tapered shape when viewed from a cross section, and is filled with a conductive material from a wider side.   23. The method according to claim 22, wherein the conductive material is a conductive paste.

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