JP2006310627A - Wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having a superior connection reliability between a wiring conductor and a through conductor, and also to provide its manufacturing method. <P>SOLUTION: The wiring board 50 comprises a first insulation layer 1a, first wiring conductor 2a consisting of a metal foil which is embedded in one face of the first insulation layer 1a, second insulation layer 1b which includes a through-hole 12 connected to the first wiring conductor 2a and is stacked on one face of the first insulation layer 1a, the through-conductor 3 which has its one end in contact with the first wiring conductor 2a and consists of a conductive material containing metal powder and resin packed in the through-hole 12, and second wiring conductor 2b consisting of a metal foil and is embedded in one face of the second insulation layer 1b opposite from the first insulation layer 1a so as to be in contact with the other end of the through-conductor 3. In the through-conductor 3, metal powder whose grain diameter is small out of the metal powder which constitutes the through-conductor 3 is unevenly distributed at least on the side of one end in contact with the first wiring conductor 2a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, insulating layers and wiring conductors are alternately laminated, and upper and lower wiring conductors are electrically connected by through conductors, and a wiring board excellent in connection reliability between wiring conductors and through conductors and the wiring board It relates to a manufacturing method.

  Conventionally, as a wiring board used for mounting electronic components such as semiconductor elements and resistors, a wiring made of a heat-resistant fiber base material such as a glass fiber base material and an insulating layer made of a thermosetting resin and copper foil or the like 2. Description of the Related Art There is known a wiring board in which conductors are alternately laminated and wiring conductors positioned above and below with an insulating layer are electrically connected by a through conductor formed in the insulating layer.

This wiring board is manufactured as follows, for example.
(A) forming a through-hole with a laser in a wiring board region of an insulating layer impregnated with a thermosetting resin precursor in a heat-resistant fiber base;
(B) A conductive paste made of a low-resistance metal powder containing tin, silver or the like and a thermosetting resin precursor is embedded in this through-hole by screen printing (press-fit) to form a through-conductor.
(C) On the other hand, a copper foil is deposited on the surface of a transfer sheet made of a heat resistant resin, etched into a predetermined pattern to form a wiring conductor at a position corresponding to each wiring board region of the insulating layer,
(D) The transfer sheet on which the wiring conductor is formed is pressed against the insulating layer on which the through conductor is formed, and the wiring conductor is transferred and embedded in the insulating layer and electrically connected to the through conductor. Here, in general, the insulating layer that forms the outermost layer of the wiring board is embedded with a wiring conductor on one side of the surface side, and the insulating layer that forms the intermediate layer is embedded with a wiring conductor on both sides. To do.
(E) Next, after peeling off the transfer sheet from the insulating layer, a plurality of insulating layers in which wiring conductors are embedded are stacked, and the thermosetting is performed using a heat press at a temperature of 180 to 200 ° C. for several minutes to several hours. The wiring substrate is obtained by curing and integrating the functional resin precursor.

  The above-mentioned method of forming the through conductor by filling with a conductive paste can provide the through conductor at an arbitrary position, compared with the conventional method of forming the through conductor by plating, and therefore, particularly for high-density wiring. It is attracting attention as a suitable method.

  FIG. 11 is an enlarged cross-sectional view showing a through conductor portion in the vicinity of the surface of a conventional wiring board created by the above manufacturing method. As shown in FIG. 11, this wiring board 100 has insulating layers 101 and wiring conductors 102 alternately stacked, and through holes in which wiring conductors 102 positioned above and below the insulating layer 101 are provided in the insulating layer 101. It is formed by connecting with a through conductor 106 made of a conductive material containing a metal powder 103 filled in 105 and a thermosetting resin.

  In this wiring board 100, the solder resist layer 4 is deposited on the surface of the insulating layer 101b forming the outermost layer. The insulating layer 101b has the wiring conductor 102b embedded only on one surface, and the insulating layer 101a on which the insulating layer 101b is stacked has the wiring conductor 102a embedded on both surfaces thereof.

  The wiring substrate 100 exhibits conductivity by contact between the metal powders 103 and between the metal powder 103 and the wiring conductor 102. In addition, a so-called diffusion layer is formed between the wiring conductor 102 and the through conductor 106, in which a metal constituting the metal powder 103 is diffused into the wiring conductor 102, thereby connecting the wiring conductor 102 and the through conductor 106. Strengthened.

  Here, the metal powder 103 has a particle size distribution in which the metal powder 103a having a small particle size to the metal powder 103b having a large particle size are dispersed substantially uniformly. In such a state, the contact point between the metal powder 103 of the through conductor 106 and the wiring conductor 102 is likely to be insufficient due to the presence of the metal powder 103b having a large particle size. If the contact points are insufficient, the electrical resistance between the through conductor 106 and the wiring conductor 102 becomes high and the diffusion layer is hardly formed, and the connection reliability between the wiring conductor 102 and the through conductor 106 is lowered. is there.

  On the side of the insulating layer 101 where the wiring conductor 102 is embedded, for example, between the wiring conductor 102b and the through conductor 106 in the insulating layer 101b, the wiring conductor 102b and the through conductor 106 are strong when the wiring conductor 102b is embedded. Because of pressure contact, lack of contact points is unlikely to occur. On the other hand, since the pressure contact is weak between the opposite side, that is, the through conductor 106 of the insulating layer 101b and the wiring conductor 102a of the insulating layer 101a in contact with the through conductor 106, the contact points are likely to be insufficient.

  Patent Document 1 is characterized in that an average particle diameter is in a range of 0.5 to 20 μm, and conductive powder obtained by mixing a plurality of conductive powders having different average particle diameters is dispersed in a liquid epoxy resin. A conductive paste composition for filling via holes is described. According to this document, it is described that dents that occur during filling of conductive powder (conductor paste) into via holes (through holes) are eliminated. However, there is no particular description of the lack of contact points.

In Patent Document 2, a plurality of insulating layers and wiring conductors are alternately stacked, and a through hole in which the wiring conductors positioned above and below the insulating layer are provided in the insulating layer has a predetermined conductive material. In the wiring board formed by electrically connecting through the through conductors filled with the wiring conductor, the wiring conductor has 10 to 30 bonding points per 1000 μm ² on the surface connected to the through conductor. A characteristic wiring board is described. According to this document, it is described that a wiring board excellent in connection reliability between a wiring conductor and a through conductor can be obtained. However, the present situation is that sufficient connection reliability is not always obtained even in the case of a wiring board in which the coupling point is a predetermined value. For this reason, development of a wiring board having better connection reliability is desired.

JP 2003-92024 A JP 2004-31814 A

  The subject of this invention is providing the wiring board excellent in the connection reliability of a wiring conductor and a penetration conductor, and its manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventor has found that the metal powder having a small particle size out of the metal powder of the through conductor in the insulating layer in which the wiring conductor is embedded on one side is the wiring conductor. Is unevenly distributed on the non-embedded side, the number of contact points between the through conductor on the side where the metal powder having a small particle size is unevenly distributed and the wiring conductor in contact with the through conductor increases. The inventors have found a new knowledge that a wiring board excellent in connection reliability between a through conductor and a through conductor is obtained, and have completed the present invention.

That is, the wiring board and the manufacturing method thereof according to the present invention have the following configurations.
(1) having a first insulating layer, a first wiring conductor made of a metal foil embedded in one surface of the first insulating layer, and a through-hole communicating with the first wiring conductor, A second insulating layer laminated on one side of the first insulating layer, and a through hole made of a conductive material including a metal powder and a resin with one end contacting the first wiring conductor and filling the through hole A conductor, and a second wiring conductor made of a metal foil embedded in contact with the other end of the through conductor on one side of the second insulating layer opposite to the first insulating layer. The through-conductor is characterized in that a metal powder having a small particle size is unevenly distributed among metal powders constituting the through-conductor at least on one end side in contact with the first wiring conductor. Wiring board to be used.
(2) The wiring board according to (1), wherein the metal powder having a small particle size is a metal powder having a particle size smaller than half of the maximum particle size of the metal powder filled in the through hole.
(3) A step of preparing a first insulating layer and a second insulating layer, a step of drilling a through hole in the second insulating layer, and a conductive paste containing a metal powder and a resin in the through hole A step of filling from one end side of the through-hole, and embedding a first wiring conductor made of metal foil on at least one surface of the first insulating layer, and in the through-hole of the second insulating layer A step of embedding a second wiring conductor made of a metal foil on one surface on the other end side so as to be in contact with the conductor paste, and the first insulating layer and the second insulating layer are A method of manufacturing a wiring board comprising a step of stacking and integrating the wiring conductor so that the wiring conductor is in contact with the conductive paste at one end of the through-hole in the second insulating layer, and the step of filling the conductive paste Large particle size from the surface of the conductive paste And removing the metal powder, leaving the metal powder having a small particle size, and filling the metal powder having a small particle size so as to be unevenly distributed on at least one end side of the through hole. A method for manufacturing a wiring board.
(4) The wiring board according to (3), wherein the step of filling the conductive paste is a step of repeating the step of filling the through hole with the conductive paste and the step of wiping the surface of the filled conductive paste a plurality of times. Manufacturing method.

  According to the wiring board and the manufacturing method of the present invention, among the metal powder of the through conductor in the insulating layer in which the wiring conductor is embedded on one side, the metal conductor having a small particle size is embedded in the wiring conductor. Therefore, the number of contact points between the through conductor on the side where the metal powder having a small particle size is unevenly distributed and the wiring conductor in contact with the through conductor increases, and the electrical connection between the through conductor and the wiring conductor is increased. The resistance is reduced, and a diffusion layer is formed well between the through conductor and the wiring conductor, so that there is an effect that a wiring board excellent in connection reliability between the wiring conductor and the through conductor can be obtained.

<Wiring board>
Hereinafter, a wiring board according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing the wiring board of this embodiment, and FIG. 2 is an enlarged cross-sectional view showing a through conductor portion in the vicinity of the surface of the wiring board of this embodiment.

  As shown in FIG. 1, the wiring board 50 of this embodiment has a plurality of insulating layers 1 and wiring conductors 2 alternately stacked. The wiring conductors 2 positioned above and below the respective insulating layers 1 are electrically connected by the through conductors 3 penetrating the respective insulating layers 1. Further, protective solder resist layers 4, 4 are provided on the surface of the outermost insulating layer 1, and a semiconductor element such as a semiconductor integrated circuit element is provided at a portion leading to the center of the upper surface of the wiring substrate 50. A semiconductor element connection pad 9 a to which the five electrodes are electrically connected via the solder bump 6 is formed. Further, external connection pads 9b that are electrically connected to the wiring conductors of the external electric circuit board via the solder balls 7 are formed at the portion leading to the lower surface.

  The insulating layer 1 is made of, for example, an electrically insulating material obtained by impregnating a heat-resistant fiber base material obtained by weaving a bundle of glass fibers vertically and horizontally into a sheet shape and impregnating a thermosetting resin such as an allyl-modified polyphenylene ether resin. Specifically, the insulating layer 1 preferably has a thickness of 50 to 150 μm, has a function of supporting the wiring conductor 2 and maintaining insulation between the wiring conductors 2 positioned above and below, A heat-resistant fiber substrate such as an aramid fiber or wholly aromatic ester fiber is impregnated with a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin, or an allyl-modified polyphenylene ether resin.

  In addition, when the thickness of the insulating layer 1 is less than 50 μm, the rigidity of the wiring board tends to decrease and the wiring board 50 tends to bend easily. When the thickness exceeds 150 μm, the thickness of the insulating layer 1 becomes unnecessarily thick. As a result, the weight reduction of the wiring board 50 tends to be difficult. Therefore, the insulating layer 1 preferably has a thickness of 50 to 150 μm.

  The wiring conductor 2 is made of a metal foil such as a copper foil, for example, and is arranged in a state of being embedded in the surface of each insulating layer 1. The wiring conductor 2 has a function as a part of a conductive path that electrically connects each electrode of the semiconductor element 5 or the like that is an electronic component mounted on the wiring board 50 to the external electric circuit board, and has a width of 20 to 20. It is preferable that it is 200 micrometers and thickness is 5-50 micrometers. If the width of the wiring conductor 2 is less than 20 μm, the wiring conductor 2 tends to be deformed or disconnected, and if it exceeds 200 μm, high-density wiring tends to be unable to be formed. Further, when the thickness of the wiring conductor 2 is less than 5 μm, the strength of the wiring conductor 2 tends to be reduced and deformation or disconnection tends to occur. When the thickness exceeds 50 μm, it is difficult to embed in the insulating layer 1. Tend. Therefore, the wiring conductor 2 preferably has a width of 20 to 200 μm and a thickness of 5 to 50 μm.

  The surface of the wiring conductor 2 is preferably formed with irregularities having an average surface roughness of 1 to 3 μm on the surface in order to improve adhesion and bonding properties with the through conductor 3. Such irregularities are formed by treatment with formic acid and hydrochloric acid. If the surface roughness is less than 1 μm, the adhesion strength with the insulating layer 1 tends to decrease, and the wiring conductor 2 tends to be peeled off from the insulating layer 1. If the surface roughness exceeds 3 μm, the wiring conductor 2 and the metal powder Therefore, there is a tendency that the diffusion layer cannot be formed satisfactorily. Therefore, the average surface roughness is preferably in the range of 1 to 3 μm.

  Each insulating layer 1 is provided with a plurality of through conductors 3 from the upper surface to the lower surface. These through conductors 3 have a function of electrically connecting the wiring conductors 2 positioned above and below the insulating layer 1 and preferably have a diameter of 30 to 200 μm. When the diameter of the through conductor 3 is less than 30 μm, the processing tends to be difficult, and when it exceeds 200 μm, there is a tendency that high-density wiring cannot be formed. Therefore, the through conductor 3 preferably has a diameter of 30 to 200 μm.

  The through conductor 3 is made of, for example, a metal powder made of an alloy of tin, silver, bismuth and copper and a triazine such as triallyl cyanurate, triallyl isocyanurate, trisepoxypropyl isocyanurate, tris (2-hydroxyethyl) isocyanurate. Containing thermosetting resin. The metal powder exhibits conductivity due to contact between the metal powders and the metal powder and the wiring conductor 2. Further, a diffusion layer of, for example, tin and copper is formed between the metal powder and the wiring conductor 2, thereby strengthening the connection between the wiring conductor 2 and the through conductor 3.

  Further, the content of the metal powder is preferably 80 to 95% by mass with respect to the total amount of the through conductors 3. When the content of the metal powder is less than 80% by mass, connection between the metal powders is hindered by the thermosetting resin, and the conduction resistance tends to increase. When the content exceeds 95% by mass, the metal powder and the triazine type are used. There is a tendency that the viscosity of the conductor paste containing the thermosetting resin is so high that it cannot be embedded well. Therefore, the content of the metal powder is preferably 80 to 95% by mass.

  In the metal powder of the present invention, a metal powder having a small particle size is unevenly distributed on a predetermined side of the through conductor 3. As shown in FIG. 2, the vicinity of the surface of the wiring substrate 50 is a first insulating layer 1a, a first wiring conductor 2a embedded in one surface of the first insulating layer 1a, and a first wiring conductor 2a. A second insulating layer 1b having a through hole 12 leading to the first insulating layer 1a and laminated on one side of the first insulating layer 1a, and one end portion is in contact with the first wiring conductor 2a and filled into the through hole 12 The through conductor 3 made of a conductive material containing metal powder 8 and a resin, and embedded in contact with the other end of the through conductor 3 on one side of the second insulating layer 1b opposite to the first insulating layer 1a. And a second wiring conductor 2b.

  In the through conductor 3, the metal powder 8a having a small particle diameter is unevenly distributed among the metal powders 8 constituting the through conductor 3 on one end side in contact with the first wiring conductor 2a. As a result, among the metal powders 8 of the through conductor 3 in the second insulating layer 1b in which the wiring conductors that are likely to be short of contact points are embedded only on one side, the penetration on the side where the metal powder 8a having a small particle size is unevenly distributed The number of contact points between the conductor 3 and the first wiring conductor 2a in contact with the through conductor 3 is increased. As a result, the electrical resistance between the through conductor 3 and the wiring conductor 2a is reduced and the diffusion layer Is formed well.

  The metal powder 8 a having a small particle size among the metal powders 8 is preferably a metal powder having a particle size smaller than half of the maximum particle size of the metal powder 8 filled in the through-holes 12. Specifically, the particle diameter that is half of the maximum particle diameter is 3 to 11 μm, more preferably 5 to 9 μm, and the metal powder 8a is a metal powder having a particle diameter smaller than a value within this range. Is preferred. When the particle size is smaller than 3 μm, the viscosity of the conductor paste is excessively increased, and the metal powders 8 tend to form agglomerates in the conductive paste and are difficult to disperse uniformly, and the fluidity of the conductor paste deteriorates. It becomes difficult to fill the through holes 12. On the other hand, when the thickness is larger than 11 μm, the metal powder 8 cannot be highly filled, and the number of contact points between the metal powders 8 is not preferable. Therefore, the particle size smaller than half of the maximum particle size of the metal powder 8 is preferably 3 to 11 μm. The metal powder 8 is a metal powder having a minimum particle size of about 0.1 μm and a maximum particle size of about 22 μm, and having a particle size distribution within the range between the minimum particle size and the maximum particle size. preferable. The particle size and particle size distribution are values obtained by measurement with a particle size distribution measuring device.

<Manufacturing method of wiring board>
Next, an example of a method for manufacturing a wiring board according to the present invention will be described in detail with reference to the drawings. 3 to 8 are schematic views showing a method for manufacturing the wiring board of the present invention. Among these, FIG. 3 is a schematic view showing a process of forming a through hole in the insulating layer and filling the through hole with a conductive paste, and FIG. 4 is an enlarged view showing a state in which the through hole is filled with the conductive paste. FIG. 5 is a schematic view showing a method for unevenly distributing metal powder having a small particle diameter, FIG. 6 is a schematic view showing a method for forming a wiring conductor, and FIG. FIG. 8 is a schematic diagram showing a method for embedding in an insulating layer, and FIG. 8 is a schematic diagram showing a method for forming an insulating layer in which through conductors are formed and wiring conductors are embedded into a laminate. 3 to 8, the same or equivalent parts as those in FIGS. 1 and 2 described above are denoted by the same reference numerals and description thereof is omitted.

  First, as shown in FIG. 3A, a prepreg 10 for the insulating layer 1 is prepared. The prepreg 10 for the insulating layer 1 is obtained by impregnating a heat-resistant fiber base material with an uncured thermosetting resin, and a resin film 11 such as polyethylene terephthalate (PET) is adhered to the upper and lower surfaces thereof. Yes.

  Next, as shown in FIG. 3B, the prepreg 10 is drilled with the resin film 11 together with the through-hole 12 by laser light. At this time, the through hole 12 has an opening diameter on the incident side of the laser beam larger than an opening diameter on the emission side.

  Then, as shown in FIG. 3C, the conductor paste 30 for the through conductor 3 is filled from the larger opening diameter of the through hole 12 by a screen printing method using the resin film 11 as a printing mask. Specifically, while pressing the squeegee 45 against the surface of the resin film 11, the squeegee 45 is moved in the direction shown in FIG. The conductive paste 30 contains the above-described metal powder and an uncured thermosetting resin.

  As shown in FIG. 4, in the metal powder 8 constituting the conductor paste 30 filled in the through-hole 12, the metal powder 8a having a small particle size and the metal powder 8b having a large particle size are dispersed substantially uniformly. Here, as shown in FIG. 3D, the prepreg 10a for the first insulating layer 1a in which the wiring conductors are embedded on both surfaces of the wiring substrate 50, respectively, the resin film 11 from both surfaces of the prepreg 10a. It peels and the prepreg 10a with which the conductor paste 30 was filled is obtained.

  On the other hand, the prepreg 10b for the second insulating layer 1b in which the wiring conductor is embedded only on one side is a prepreg 10b in which the conductor paste 30 is embedded in the through hole 12, as shown in FIG. The surface of the conductive paste 30 is wiped in the direction of the arrow shown in FIG. When the wiping is performed, the metal powder 8b having a large particle size is preferentially removed, and the metal powder 8a having a small particle size remains. The remaining metal powder 8a having a small particle size falls into a state of being dropped between metal powders 8b having a large particle size.

  Then, as shown in FIG. 5B, after the conductor paste 30 is additionally printed on the surface of the through-hole 12 after wiping, a plurality of wiping operations are performed as shown in FIG. 5A again. By repeating the process, the metal powder 8a having a small particle diameter can be selectively disposed on the wiped side as shown in FIG. 5 (c). In addition, the frequency | count of wiping should just be the frequency | count that the small metal powder 8a is selectively arrange | positioned, and although it does not specifically limit, For example, it is preferable that it is about 3 to 4 times.

  Next, as shown in FIG. 3 (d), the resin film 11 is peeled from the surface of the prepreg 10b, and a metal powder 8a having a small particle size is selectively formed on one end side of the conductor paste 30 (through conductor 3). Thus, the prepreg 10b for the second insulating layer 1b arranged in the above can be obtained. Even when the process for selectively disposing the metal powder 8a having a small particle diameter on one end side of the conductor paste 30 is applied when the prepreg 10a for the first insulating layer 1a is obtained. It doesn't matter.

  On the other hand, as shown in FIG. 6A, a transfer sheet 20 is prepared in which a metal foil 22 such as a copper foil is detachably bonded to the surface of a transfer film 21 made of a resin such as PET via an adhesive (not shown). . Next, as shown in FIG. 6B, an etching resist 23 having a pattern corresponding to the wiring conductor 2 is formed on the surface of the metal foil 22. Then, as shown in FIG. 6C, the metal foil 22 not covered with the etching resist 23 is removed by etching, and then the etching resist 23 is removed as shown in FIG. A wiring conductor 2 having a predetermined pattern is formed on the surface of the substrate.

  Next, as shown in FIG. 7A, the prepreg 10 in which the through-hole 12 is filled with the conductive paste 30 and the transfer film 21 on which the wiring conductor 2 is formed are aligned, and then, as shown in FIG. As shown, the wiring conductor 2 on the transfer film 21 is pressed from above and below to be embedded in the surface of the prepreg 10, and then the wiring conductor 2 is removed by removing the transfer film 21 as shown in FIG. Is transferred to the prepreg 10.

  Here, in the prepreg 10a for the first insulating layer 1a in which the wiring conductor 2 is embedded on both sides, the process shown in FIG. 7 is performed on both sides of the prepreg 10, and the wiring conductor 2 is embedded on one side. In the prepreg 10b for the second insulating layer 1b, the wiring conductor 2 is transferred to the opposite surface on which the metal powder 8a having a small particle diameter is disposed. On the side where the wiring conductor 2 is transferred and embedded, even if there is a metal powder 8b having a large particle diameter, the wiring conductor 2 and the through conductor 3 are strongly pressed when the wiring conductor 2 is embedded. The connection is good.

  Then, as shown in FIG. 8 (a), a prepreg 10b for the second insulating layer 1b is formed on one side of the prepreg 10a for the first insulating layer 1a, and a prepreg prepared in the same manner as the prepreg 10b on the other side. 10c is aligned with each other, and as shown in FIG. 8B, a plurality of prepregs 10a, 10b, and 10c are heated while being pressed from above and below, and the prepregs 10a, 10b, and 10c and the conductor paste 30 are thermally cured. Insulating layers 1 and wiring conductors 2 are alternately laminated, and a laminated body (wiring board 50) in which the upper and lower wiring conductors 2 are electrically connected by the through conductors 3 is obtained. And the wiring board 50 as shown in FIG. 1 is obtained by showing the soldering resist layer 4 on the upper and lower surfaces of this laminated body.

  In the above embodiment, the wiring board 50 in which three prepregs 10 are laminated has been described. However, the present invention is not limited to this wiring board 50, and an arbitrary number of prepregs 10 can be used depending on the application. Even a laminated wiring board can be suitably applied. Further, although the particle size of the metal powder 8 is small only on one side of the through-hole 12, the metal powder 8 is formed on both sides of the through-hole 12 by performing the process shown in FIG. 5 on both sides of the prepreg 10. The particle size may be small. In this case, since the number of contact points between the through conductor and the wiring conductor in contact with the through conductor is increased, a wiring board with further improved connection reliability between the wiring conductor and the through conductor can be obtained.

<Cross-section observation>
The cross section of the wiring board obtained by said manufacturing method was observed using the scanning electron microscope (SEM). FIG. 9 is an enlarged image obtained by a scanning electron microscope (SEM) showing a cross section of the through conductor portion in the vicinity of the surface of the wiring board according to the present invention obtained by the above manufacturing method.

  As shown in FIG. 9, the wiring board according to the present invention includes a metal powder having a small particle size among the metal powder of the through conductor in the insulating layer in which the wiring conductor is embedded on one side. You can see that it is unevenly distributed on the side that is not.

  FIG. 10 is a schematic explanatory view showing a wiring board according to another embodiment of the present invention. As shown in FIG. 10, the wiring substrate 50 according to the present invention may be used as a core substrate, and insulating layers 40 made of thermosetting resin and wiring conductors 41 made of plated metal may be alternately laminated thereon. . In FIG. 10, the same reference numerals are given to the same or equivalent parts as those in FIGS. 1 to 8 described above, and the description thereof is omitted.

It is a schematic explanatory drawing which shows the wiring board concerning one Embodiment of this invention. It is an expanded sectional view showing the penetration conductor part near the surface of the wiring board concerning one embodiment of the present invention. (A)-(d) is the schematic which shows the process of forming a through-hole in an insulating layer and filling this through-hole with a conductor paste. It is an expanded sectional view which shows the state which filled the through-hole with the conductor paste. (A)-(c) is the schematic which shows the method of unevenly distributing the metal powder with a small particle size. (A)-(d) is the schematic which shows the method of forming a wiring conductor. (A)-(c) is the schematic which shows the method of embedding a wiring conductor in an insulating layer. (A), (b) is the schematic which shows the method of shape | molding the insulating layer by which the penetration conductor was formed and the wiring conductor was embedded to a laminated body. It is an enlarged image by the scanning electron microscope (SEM) which shows the cross section of the penetration conductor part in the surface vicinity of the wiring board concerning this invention. It is a schematic explanatory drawing which shows the wiring board concerning other embodiment of this invention. It is an expanded sectional view which shows the penetration conductor part in the surface vicinity of the conventional wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,40 Insulating layer 1a 1st insulating layer 1b 2nd insulating layer 2,41 Wiring conductor 2a First wiring conductor 2b First wiring conductor 3 Through conductor 4 Solder resist layer 5 Semiconductor element 6 Solder bump 7 Solder ball 8 Metal powder 8a Metal powder with small particle size 8b Metal powder with large particle size 9a Semiconductor device connection pad 9b External connection pad 10, 10a, 10b, 10c Prepreg 11 Resin film 12 Through hole 13 Dust-free cloth 20 Transfer sheet 21 Transfer film 22 Metal foil 23 Etching resist 30 Conductive paste 45 Squeegee 50 Wiring board

Claims (4)

A first insulating layer and a first wiring conductor made of a metal foil embedded in one surface of the first insulating layer;
A second insulating layer having a through hole leading to the first wiring conductor and laminated on one side of the first insulating layer;
A through conductor made of a conductive material including a metal powder and a resin, one end of which is in contact with the first wiring conductor and filled in the through hole;
A wiring board comprising a second wiring conductor made of a metal foil embedded in contact with the other end of the through conductor on one surface of the second insulating layer opposite to the first insulating layer Because
The wiring board according to claim 1, wherein a metal powder having a small particle size is unevenly distributed among metal powders constituting the through conductor on at least one end side in contact with the first wiring conductor.   2. The wiring board according to claim 1, wherein the metal powder having a small particle size is a metal powder having a particle size smaller than half of the maximum particle size of the metal powder filled in the through hole. Preparing a first insulating layer and a second insulating layer;
Drilling a through hole in the second insulating layer;
Filling a conductive paste containing metal powder and resin into the through hole from one end side of the through hole; and
A first wiring conductor made of metal foil is embedded in at least one surface of the first insulating layer, and a second wire made of metal foil is formed on one surface on the other end side of the through hole of the second insulating layer. Embedding a wiring conductor in contact with the conductor paste;
Stacking and integrating the first insulating layer and the second insulating layer so that the first wiring conductor is in contact with the conductor paste at one end of the through hole in the second insulating layer; A method for manufacturing a wiring board comprising:
The step of filling the conductive paste removes the metal powder having a large particle size from the surface of the conductive paste, leaving the metal powder having a small particle size, and the metal powder having a small particle size is at least one end of the through-hole. A method of manufacturing a wiring board, which is a step of filling so as to be unevenly distributed on the part side. 4. The method of manufacturing a wiring board according to claim 3, wherein the step of filling the conductive paste is a step of repeating the step of filling the through hole with the conductive paste and the step of wiping the surface of the filled conductive paste a plurality of times.