JP2003209355A - Circuit board and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a circuit board in which a wiring circuit of a metal foil having a fine pattern can be inexpensively formed by a dry process. <P>SOLUTION: The method for manufacturing the circuit board comprises the steps of forming a connecting electrode 12 for connecting a via on an insulation resin film 11, then disposing a metal foil 13a for forming a wiring circuit 13 on the resin film 11, aligning a pressing jig 14 having a protruding shape 14a simulating to the wiring pattern of the circuit 13 to be disposed on the foil 13a, and sandwiching the jig 14 between hot platens 15a and 15b. Thus, the foil 13a is punched according to a wiring pattern by the shaped pattern 14a of the jig 14, and hot pressed on an upper surface of the electrode 12 and the film 11 around the electrode 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a wiring board in which a wiring circuit and connection electrodes for via connection are provided on an insulating resin base material, and a wiring board thereof.

[0002]

2. Description of the Related Art Conventionally, a wiring board is widely used in which a wiring circuit is formed by a metal foil such as Cu on a substrate of thermosetting resin such as epoxy resin, and electronic parts such as IC bare chips are mounted. ing. In addition, in a laminated wiring board in which such resin substrates are laminated, an electrode formed by filling a through hole provided on the resin substrate with a conductive paste,
A method of making via connection between wiring boards is often used.

In recent years, thermoplastic resins have been attracting attention as a material for wiring boards. Since the thermoplastic resin is easy to mold a wiring pattern and the like and has a re-fusion property due to heat, the wiring board, the IC chip, and the wiring boards are firmly fixed to each other without using an adhesive. It becomes possible.

[0004]

By the way, when an electronic component is mounted on a wiring board, solder is usually used for electrical connection with a wiring circuit. However, when mounting an electronic component on the connection electrode formed by the conductive paste, because the adhesiveness between the conductive paste and the solder is poor, a metal foil is formed on the upper surface of the connection electrode, and the metal foil and the electronic A method of joining parts with solder is adopted.

However, conventionally, a wiring circuit made of a metal foil has generally been formed by a wet process using a chemical such as etching or plating. For this reason, a waste liquid treatment facility is required for manufacturing the wiring board, and there is a possibility of a work environment problem and a possibility of a chemical liquid outflow accident. Therefore, an alternative manufacturing method has been demanded.

[0006] For example, Japanese Patent Publication No. 2000-509909 proposes a so-called eye bonding method in which a special copper foil is used as a material for a wiring circuit, the special copper foil is punched out by a die and transferred to a thermoplastic resin substrate. Has been done. However, although this method solves the problems related to the environment due to the wet process, in order to manufacture products that require fine wiring, the cost required to form the mold becomes enormous, and small-quantity high-mix production Not suitable for etc.

The present invention has been made in view of the above problems, and is a method for manufacturing a wiring board, which allows a wiring circuit made of a metal foil having a fine pattern to be formed at a low cost by a dry process. The purpose is to provide.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a wiring board in which a wiring circuit and a connection electrode for via connection are provided on an insulating resin base material. A via hole corresponding to the shape of the connection electrode is formed on the base material, the via hole is filled with a conductive paste to form the connection electrode, and an indentation cure having a convex shape imitating the shape of the wiring circuit is formed. Using a tool, a metal foil is hot pressed onto the insulating resin base material to bring the metal foil into contact with the connection electrode, and an extra portion attached to a portion of the insulating resin base material that is not pressed by the pressing jig. A method for manufacturing a wiring board is provided, characterized in that the metal foil is removed.

In such a method of manufacturing a wiring board, a metal foil is hot-pressed onto an insulating resin base material by a pressing jig having a convex shape imitating the shape of a wiring circuit.
The metal foil is punched on the insulating resin base material according to the wiring pattern of the wiring circuit, and then the excess metal foil on the insulating resin base material is removed to form the wired circuit.

Further, for example, by using a metal foil having different roughness on one surface and the other surface, and pushing the metal foil so that the surface having a large roughness contacts the connecting electrode, the metal foil and the connecting electrode are pressed. Connectivity with

Further, for example, when a connection electrode is formed using a conductive paste containing a metal filler,
At least one surface of the metal foil is provided with a layer of a material which is alloyed with a metal filler at a temperature below the temperature at which the insulating resin base material can be hot pressed, and the metal foil is pressed so that the layer of this material contacts the connecting electrode. You may do it. In this case, with respect to the metal foil adhered on the insulating resin base material, a large difference in adhesion strength occurs between a portion pushed by the pushing jig and a portion not pushed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first wiring board of the present invention.
It is sectional drawing which shows the example of embodiment.

The wiring board 1 shown in FIG. 1 is a resin film 1.
A plurality of connection electrodes 12 for via connection and a plurality of wiring circuits 13 are formed on each of the wirings 1. Resin film 1
Reference numeral 1 is an insulating base material formed of a material containing a thermoplastic resin or a thermosetting resin into a film shape having a thickness of 50 to 200 μm, for example. As the thermoplastic resin material, for example, a relatively high heat resistant resin material such as PEEK (polyetheretherketone), PEK (polyetherketone), PEI (polyetherimide), PPS (polyphenylene sulfide) or the like can be used. . Further, as the thermosetting resin material, a resin material such as glass epoxy material such as FR4 and FR5 can be used. Further, such a thermosetting resin material may be mixed with the above-mentioned thermoplastic resin material, or the like. In the case of a thermoplastic resin or a material containing the same, a material having a heat fusion temperature range in a temperature range not lower than the glass transition temperature and lower than the melting point is desirable, as described later.

The connection electrode 12 is formed by filling the inside of a via hole 11a formed through the resin film 11 with a conductive paste and solidifying it. As this conductive paste, it is desirable to use, for example, a thermoplastic binder containing a highly conductive filler such as Ag particles or Cu particles. In this case, since it has a self-bonding property, when a plurality of resin films 11 are laminated, electrical conduction with the connection electrodes 12 and the wiring circuits 13 on another resin film 11 is not particularly required. Can be taken easily.

The wiring circuit 13 is formed by embedding a metal foil 13a of Cu or the like on the upper surface of the formation portion of the connection electrode 12. The height of the surface of the metal foil 13a is equal to or lower than that of the surface of the resin film 11, so that the wiring circuit 13 is formed so as not to project from the surface of the resin film 11. Further, as the metal foil 13a, for example, one having a surface roughness different from that of the other surface is used, and a surface having a large surface roughness is brought into contact with the connection electrode 12 so that the electrical connection with the connection electrode 12 is reduced. It is possible to improve the adhesiveness as well as the physical connectivity.

A plurality of the wiring boards 1 described above can be stacked and used. In that case, since the resin film 11 is made of a material containing a thermoplastic resin,
The resin films 11 can be joined together by heat fusion. Therefore, it is not necessary to use an adhesive at the time of stacking, the material cost is suppressed, and the manufacturing efficiency is improved. Further, as compared with the case of fixing with an adhesive, the reliability of the fixing portion with respect to the environmental temperature is improved.

In the above wiring board 1, as an example,
The wiring circuit 13 is provided only on the upper surface of the connection electrode 12 for via connection.
Although the wiring circuit 13 is formed, the wiring circuit 13 may be formed on the surface of the resin film 11 other than this.

Next, an example of a specific manufacturing process of the wiring board of the present invention will be described. In this manufacturing process example, an insulating resin material containing a thermoplastic resin is used as the resin film 11.

First, a flat film-like resin film 11 having a thickness of 100 μm, for example, is formed. As described above, the resin film 11 uses a single thermoplastic resin material having relatively high heat resistance, or a thermosetting resin such as a glass epoxy material mixed with the thermoplastic resin material. Things are used. Also, with high heat resistance and high rigidity,
A material having isotropic property is preferable, and a material containing a reinforcing filler for suppressing resin shrinkage during heat molding is more preferable.

Next, a via hole 11a for forming the connection electrode 12 is formed at a predetermined position on the resin film 11 by using a drill, a laser or the like. Then, the formed via hole 11a is filled with a conductive paste using, for example, a squeegee. As the conductive paste, for example,
A thermoplastic binder containing a highly conductive filler such as Ag particles or Cu particles is used. Further, as described later, the surface roughness Rmax of the contact surface of the metal foil 13a with the connection electrode 12 is increased.
Therefore, it is desirable to contain a highly conductive filler having a small average particle size. After that, for example, after drying at a temperature of 80 degrees, heat treatment at 150 degrees is performed to solidify the conductive paste. By the above, the connection electrode 12 is formed.

Next, FIG. 2 is a sectional view showing a structure for forming the wiring circuit 13 on the resin film 11. The metal foil 1 is formed on the resin film 11 on which the connection electrodes 12 are formed.
In order to form the wiring circuit 13 of 3a, a pushing jig 14 for punching the metal foil 13a along the wiring pattern of the wiring circuit 13 is used. This pushing jig 1
4, a convex shape portion 14a imitating the wiring pattern of the wiring circuit 13 is formed on the stainless plate by etching with a photolithographic mask, for example. Note that the example of FIG. 2 shows a case where the wiring circuit 13 is formed on the upper surface of the connection electrode 12 to be slightly larger than the width of the connection electrode 12. Therefore, the convex shape portion 14a of the pushing jig 14 is also formed. , And has a circuit pattern width corresponding to this.

Further, the metal foil 13 forming the wiring circuit 13
As a, for example, an electrolytic copper foil having a thickness of 9 μm is used.
The metal foil 13a is processed so that the roughness of one surface thereof is higher than that of the other surface.

Next, as shown in FIG. 2, the resin film 1
The metal foil 13a is sandwiched between the pressing jigs 1 and 1, and the pushing jig 14 is aligned and arranged. At this time, the metal foil 13
About a, it arrange | positions so that the surface with high roughness may become the resin film 11 side. Then, these are pressed down from above and below by the hot plates 15a and 15b, and the pushing jig 14 is pressed.
Is hot pressed onto the resin film 11.

The temperature at this time is preferably higher than the glass transition temperature of the resin film 11 and lower than the melting point. However, in order to prevent the fusion property of the resin film 11 and the accuracy of mutual engagement from significantly lowering when the completed wiring board 1 is laminated, the temperature during the hot pressing is slightly higher than the glass transition temperature. It is more desirable to be done.

During the above hot pressing, the metal foil 13
In order to improve the punchability of a and suppress the adhesion of the conductive paste forming the connection electrode 12 to the hot platen 15b,
The lower surface of the resin film 11 and the connection electrode 12 and the heating plate 15
Between b and the resin film 11 below the temperature during hot pressing
It is more preferable to dispose a release film having a lower elastic modulus.

In FIG. 3, the wiring circuit 1 is formed on the resin film 11.
3 is a cross-sectional view showing how 3 is formed. FIG. Figure 3 (A)
Shows a state in which the hot pressing by the hot plates 15a and 15b is performed by the above method. This Figure 3
As shown in (A), the metal foil 13 is formed only on the wiring pattern portion of the wiring circuit 13 by the pushing jig 14.
The metal foil 13a is embedded in the resin film 11 above the portion where the connection electrode 12 is formed by punching out a. At this time, the metal foil 13a is adhered to the connection electrode 12 and the resin film 11 around the connection electrode 12 due to the fusion property of the conductive paste and the resin film 11.

Therefore, after that, when the pushing jig 14 is removed from the resin film 11 as shown in FIG.
The metal foil 13a is embedded only on the position of the wiring pattern on the resin film 11, and the wiring circuit 13 is transferred. Further, the metal foil 13a in the other portion can be easily peeled off by a mechanical method using, for example, peel. However, in this state, since the excess metal foil 13a may be attached to the surface of the resin film 11, after that, the surface of the resin film 11 is polished to mechanically remove the excess metal foil 13a. May be removed.

After that, when laminating the completed wiring boards 1, the wiring boards 1 are pressed by heating them to a temperature not lower than the glass transition temperature of the resin film 11 and lower than the melting point thereof. 11 and the conductive paste of the connection electrode 12 are heat-sealed.

By the way, the height of the convex shaped portion 14a formed on the pushing jig 14 may be equal to or greater than the thickness of the metal foil 13a. However, when the pressing jig 14 is pressed onto the resin film 11, the height of the convex-shaped portion 14a is set so that the metal foil 13a can be satisfactorily punched into the shape of the wiring pattern. It is desirable to set it according to the elongation characteristics and the like.
When an electrolytic copper foil is used as the metal foil 13a, it is consequently desirable that the height of the convex shape portion 14a is three times or more the thickness of the metal foil 13a. For example, when the electrolytic copper foil having a thickness of 9 μm is used, the height of the convex shape portion 14a is 30
It is desirable that the thickness be ˜50 μm. As a result, the surface of the punched metal foil 13a is positioned lower than the surface of the resin film 11.

As described above, in the method of manufacturing the wiring board 1 according to the present invention, the metal jig 13a is pressed onto the resin film 11 by using the pressing jig 14, so that the wiring circuit 13 is formed on the resin film 11. The metal foil 13a is punched and transferred according to the wiring pattern to form the wiring circuit 13. Therefore, the dry process makes it possible to easily form the wiring circuit 13 using the metal foil 13a while suppressing the influence on the environment.

Further, it is possible to easily form a convex shape imitating the wiring pattern of the wiring circuit 13 on the pushing jig 14 by a photolithographic mask process or the like, and further, for example, a conventional eye bonding method. Since an expensive punching die or receiving die is not required, it is possible to form the wiring circuit 13 having a fine wiring pattern at low cost.

Further, by using the metal foil 13a having one surface having a higher roughness than the other surface and fixing the surface having a large roughness to the connection electrode 12 or the resin film 11, the adhesive force between them is increased. . In addition, the average particle diameter of the metal filler contained in the conductive paste used for the connection electrode 12 is defined as the surface roughness Rmax of the metal foil 13 a in contact with the connection electrode 12.
By making it smaller, the metal foil 13a and the connection electrode 1
The electrical connectivity with 2 is enhanced. Therefore, the connection electrode 12
When mounting an electronic component on the wiring circuit 13 provided above, high adhesiveness can be obtained by using solder, and electrical and mechanical connection can be reliably performed.

Further, since the material containing the thermoplastic resin is used as the resin film 11, the pattern shape of the wiring circuit 13 is easily embedded in the resin film 11 by the pressing jig 14 by utilizing its thermoformability. It becomes possible to do. Further, when the wiring board 1 is subsequently laminated, it is possible to firmly bond the resin films 11 by heat fusion without using an adhesive, which suppresses the manufacturing cost and enables efficient manufacturing. Becomes

When a thermosetting resin material is used as the resin film 11, an adhesive agent is required to bond the resin films 11 to each other when laminating the manufactured wiring boards 1.

By the way, in the manufacturing process of the wiring board 1 described above, after the metal foil 13a is hot-pressed to the resin film 11 using the pushing jig 14, the excess metal foil attached to the resin film 11 is mechanically processed. However, in this case, the metal foil 13a of the unnecessary portion is not added to the adhesive strength between the metal foil 13a of the portion to be bonded and the connection electrode 12.
Since there is little difference in the adhesive strength between the resin film 11 and
It was difficult to remove only unnecessary parts accurately by mechanical methods. Therefore, in the following second embodiment, by coating the metal foil with a material that can be alloyed with the conductive paste at a temperature equal to or lower than the temperature at the time of hot pressing, the adhesive force of the necessary portion is increased and the unnecessary portion is removed. A description will be given of a wiring board that makes it easy to remove only the above.

FIG. 4 is a sectional view showing a second embodiment of the wiring board of the present invention. The basic configuration of the wiring board 2 shown in FIG. 4 is similar to that of the above-described first embodiment. That is, the wiring board 2 includes the connection electrode 22 for via connection and the connection electrode 22 on the resin film 21 containing the high heat resistant thermoplastic resin.
A plurality of wiring circuits 23 are respectively formed.

The connection electrode 22 is formed of a conductive paste made of a thermoplastic binder containing Ag particles as a highly conductive filler. Further, the wiring circuit 23 provided on the upper surface of the connection electrode 22 is formed by the multilayer metal foil 23a including two metal layers.

Here, FIG. 5 is a view showing a cross section of the multilayer metal foil 23a used in the wiring board 2 described above. The multilayer metal foil 23a is composed of two metal layers 23b and 23c. Of these, the metal layer 23b is a metal foil that serves as a base of the multilayer metal foil 23a, and is made of, for example, the same electrolytic copper foil as that used in the above-described first embodiment. The roughness of one surface of the metal layer 23b is high.

On the other hand, the metal layer 23c is made of a metal having a relatively low melting point which is alloyed with the highly conductive filler contained in the conductive paste forming the connection electrode 22. For example, when Ag particles are used as the highly conductive filler, Sn can be used as the metal layer 23c.

In such a multi-layer metal foil 23a, Sn is coated on the roughened surface of the metal layer 23b made of electrolytic copper foil by vapor deposition, sputtering, plating or the like to form the metal layer 23.
form c. By this coating, the metal layer 23b
The roughness of the roughened surface is averaged, and the roughness of the surface of the metal layer 23c decreases. This can reduce the adhesive strength with the resin film 21 when the resin film 21 is hot pressed. On the other hand, since the metal layer 23c is coated on the roughened surface of the metal layer 23b, the adhesive strength between them is increased.

After such coating, heat treatment is further performed at a temperature necessary for causing an alloy reaction between the metal layers 23b and 23c. Metal layers 23b and 2
When 3c is Cu and Sn, respectively, they are heat-treated at a temperature of 230 degrees at which they are alloyed. This ensures the interfacial beer strength between the metal layers 23b and 23c,
When removing the excess multilayer metal foil 23a after hot pressing,
The metal layer 23b and the metal layer 23c are prevented from peeling off.

The manufacturing process of the wiring board 2 using the above-mentioned multilayer metal foil 23a will be described below. FIG. 6 is a cross-sectional view showing a structure for forming the wiring circuit 23 on the resin film 21.

The manufacturing process of the wiring board 2 according to the second embodiment of the present invention is basically the same as that of the above first embodiment. First, the insulating property containing a thermoplastic resin is used. Using the resin material of, a flat film-shaped resin film 21 having a thickness of 100 μm, for example, is formed. Next, a via hole 21a for forming the connection electrode 22 is formed at a predetermined position on the resin film 21 by using a drill or a laser.
To form. Then, the formed via hole 21a is filled with a conductive paste containing Ag particles as a highly conductive filler. Then, it is dried and heat-treated to solidify the conductive paste to form the connection electrode 22.

Next, as shown in FIG. 6, for example, a pushing jig 24 in which a convex shape portion 24a simulating the wiring pattern of the wiring circuit 23 is formed by etching on a stainless plate is prepared. This convex shaped portion 24a is 30 to 5
It has a height of 0 μm. And the resin film 21
A multi-layer metal foil 23a is placed on top of this, and a pushing jig 24 is further positioned and placed, and these are sandwiched by hot plates 25a and 25b. At this time, the multilayer metal foil 23a is arranged so that the surface coated with the metal layer 23c faces the resin film 21. Further, the temperatures of the heating plates 25a and 25b are set to be equal to or higher than the glass transition temperature of the resin film 21 and lower than the melting point, but it is preferable that the temperature is not too high and the temperature is slightly higher than the glass transition temperature. However, as described later, at this time, the temperature needs to be a temperature at which an alloying reaction between Sn of the metal layer 23c and Ag contained in the conductive paste occurs.

In FIG. 7, the wiring circuit 2 is formed on the resin film 21.
3 is a cross-sectional view showing how 3 is formed. FIG. FIG. 7 (A)
As shown in FIG. 5, when sandwiched by the heating plates 25a and 25b, the multilayer metal foil 23a is punched out by the convex shape portion 24a of the pushing jig 24, and is heat pressed to the resin film 21 and the connection electrode 22 to form the wiring circuit. The wiring pattern 23 is transferred onto the resin film 21. At this time, the multi-layer metal foil 23a adheres to the connection electrode 22 and the resin film 11 around the connection electrode 22 due to the fusion property of the conductive paste and the resin film 21. Along with this, Sn of the metal layer 23c coated on the multilayer metal foil 23a
And Ag contained in the conductive paste forming the connection electrode 22.
An alloy reaction occurs with the multi-layer metal foil 23a and the connection electrode 22.
The adhesive strength with

After that, as shown in FIG. 7B, after the pushing jig 24 is removed, the extra multilayer metal foil 23a attached to the portion other than the portion where the wiring circuit 23 is formed on the resin film 21 is removed. Peel off. By the way, the contact surface of the multilayer metal foil 23a with the resin film 21 is the metal layer 23c.
Since the roughness is lowered by the coating of
The adhesive strength with the resin film 21 is small. On the other hand, since the metal layer 23c of the multilayer metal foil 23a and the conductive paste are alloyed, the multilayer metal foil 2 is formed on the upper surface of the connection electrode 22.
The adhesive force with 3a is locally increased.

Therefore, the multi-layer metal foil 23a adhered on the resin film 21 is easily peeled off by a mechanical method using, for example, peeling, and the multi-layer metal foil 23a forms the wiring circuit 23 on the resin film 21 accurately. Formed in shape. Further, since the multilayer metal foil 23a is subjected to the alloying treatment between the metal layers 23b and 23c by the heat treatment in advance, when the extra multilayer metal foil 23a is peeled off, the metal layer 23c bonded to the connection electrode 22 is It does not peel off from the metal layer 23b.

Further, as described above, since there is a large difference in adhesive force between the connection electrode 22 and other portions, the excess multilayer metal foil 23a is easily peeled off by a mechanical method. Later extra multi-layer metal foil 23
The necessity of polishing the surface of the resin film 21 to completely remove a is reduced, and the work efficiency is increased.

As described above, in the wiring board 2 of the present embodiment, the wiring circuit 23 having an accurate shape can be easily formed, so that the high-quality wiring board 2 can be manufactured efficiently and stably. It becomes possible to do.

In the above manufacturing process, the transfer of the wiring circuit 23 is performed at a temperature not lower than the glass transition temperature of the resin film 21, and at this time, the metal layer 23c of the multi-layer metal foil 23a and the conductive property are obtained. An alloying reaction with the paste needs to occur. Therefore, in the combination of each material of the metal layer 23c and the highly conductive filler contained in the conductive paste, the temperature at which these are alloyed is about the same as the glass transition temperature of the resin film 21 at which hot pressing is possible. It is desirable to select it to be less than or equal to it.

By the way, in the above first and second embodiments, the wiring circuits 13 and 23 are arranged so that the upper surfaces of the metal foil 13a and the multilayer metal foil 23a are located lower than the surfaces of the resin films 11 and 21, respectively. Had been formed. In such a structure and when the resin films 11 and 21 are made of a material containing a thermoplastic resin, the surfaces of the resin films 11 and 21 are hot pressed again after the wiring circuits 13 and 23 are formed. As a result, the metal foil 13a and the multilayer metal foil 23a can be bonded more firmly.

The following is a description of the second embodiment described above.
The process for performing hot pressing again will be described. FIG. 8 is a cross-sectional view for explaining a step of performing hot pressing again after forming the wiring circuit 23.

As shown in FIG. 8, the wiring board 2 having the wiring circuit 23 formed on the resin film 21 is mounted on the heating plate 25 again.
It is sandwiched by a and 25b and pressed. The temperature at this time is preferably higher than or equal to the glass transition temperature of the resin film 21 and lower than the melting point.

Here, FIG. 9 is an enlarged sectional view of the periphery of the wiring circuit 23 on which the hot pressing is performed again. Figure 9
(A) shows the formation state of the wiring circuit 23 immediately before performing the hot pressing again. As shown in FIG. 9A, the wiring circuit 23 is formed such that the upper surface of the multilayer metal foil 23 a is lower than the upper surface of the resin film 21. When hot pressing is performed again from this state, as shown in FIG. 9B, the resin film 21 is thermally deformed by the pressure and its thickness is reduced, and the resin on both sides of the formation portion of the wiring circuit 23 is reduced. The film 21 is crushed. This allows
The structure is such that the resin material of the resin film 21 wraps the upper surfaces of both ends of the multilayer metal foil 23a.
It is extremely difficult for a to be separated from the resin film 21.

Even if the second hot pressing step is applied to the case of the first embodiment, the effect of preventing the metal foil 13a from peeling off from the resin film 11 can be obtained. However, in the case of the second embodiment, the metal layer 2 is formed on the surface of the multilayer metal foil 23a on the resin film 21 side.
Since the metal layer 23c and the connecting electrode 22 are alloyed with each other to obtain a strong adhesive force because the surface roughness is reduced by the coating of 3c, the resin is The adhesive strength with the film 21 is low. Therefore, in the state shown in FIG. 9 (A) in which the wiring circuit 23 is formed by hot pressing with the pushing jig 24, both ends of the multilayer metal foil 23a are peeled off,
For example, when an electronic component is soldered on the wiring circuit 23, high connectivity may not be obtained. Therefore, the re-hot-pressing step as shown in FIGS. 8 and 9 is effective when applied to the second embodiment in particular.

When a wiring board on which a wiring circuit is formed by a pushing jig is further laminated to produce a laminated wiring board, the above-mentioned hot pressing can be performed simultaneously at the time of lamination. Here, FIG. 10 is a cross-sectional view showing a step of stacking a plurality of wiring boards.

FIG. 10 shows how four wiring boards 3, 4, 5 and 6 are laminated. Each wiring board 3 ~
No. 6 has a configuration in which a connection electrode made of a conductive paste and a wiring circuit made of a metal foil are formed on a resin film containing a thermoplastic resin material. Although the wiring circuit is formed of a single-layer metal foil in this example, a multilayer metal foil coated with a material capable of alloying with the conductive paste on the surface of the connection electrode may also be used. Good.

At the time of stacking, as shown in FIG. 10A, these wiring boards 3 to 6 are aligned and arranged,
It is sandwiched by the hot plates 35a and 35b, and hot pressed. As a result, as shown in FIG. 10B, the wiring boards 3 to 6 are integrated by heat-bonding the adjacent resin films to each other, and the adjacent connection electrodes and the connection electrodes and the wiring are connected to each other. The circuit is connected by the heat-sealing property of the conductive paste.

Before lamination, the surface of the metal foil is
When the wiring circuit is formed so as to be inside from the surface of each wiring board 3 to 6, by hot pressing at the time of stacking,
Similar to the case described with reference to FIGS. 8 and 9, the resin film is compressed and both ends of the metal foil are held so as to be wrapped by the resin material of the resin film. Thereby, peeling of the metal foil from the resin film is prevented.

By the way, even when the wiring boards are formed such that the surfaces of the metal foils and the surfaces of the resin films have the same height on the surfaces where the resin films are adhered to each other, the wiring boards 3 to 6 after the lamination are stacked. Inside, the heat-deformed resin film and the conductive paste are arranged around the wiring circuit without a gap, and the metal foil is wrapped therein. However, the surface that becomes the surface layer after stacking, that is, the upper surface of the wiring board 3 and the wiring board 6
In the wiring circuit formed on the lower surface of, it is highly necessary to prevent the peeling of the metal foil. Therefore, regarding the wiring boards 3 and 6 which become the surface layer when laminated, it is particularly preferable to form the wiring circuit so that the metal foil is embedded in the resin film at the time of hot pressing by the pushing jig.

In the manufacturing process of the wiring board using the resin film containing the thermoplastic resin material described above, during the heat pressing of the metal foil on each wiring board to be laminated, Heating is performed twice during hot pressing or during lamination. Therefore, in order to prevent the fusion property of the resin film from decreasing due to heat history, the elastic force of the resin film begins to decrease at the time of the first hot pressing, and the temperature is slightly higher than the glass transition temperature of the material resin. During the subsequent hot pressing or lamination, it is desirable that the temperature be closer to the melting point.

However, the adhesive strength of the laminated resin films is preferably high in heat resistance. For this purpose, it is more desirable to use as the resin film a material that is amorphous in the state of the resin film before the hot pressing step of the metal foil and crystallizes at a temperature lower than the melting point.

When such a material is used, the step of hot pressing is carried out at a temperature slightly above the glass transition temperature, and the final step of hot pressing or lamination again is carried out at a further elevated temperature below the decomposition temperature. As a result, the resin film is crystallized in the final step, so that the heat resistance of the completed wiring board is improved. In particular, when wiring boards are laminated, crystallization progresses when the resin films of the wiring boards are integrated, so that a stable and strong adhesive force against temperature is provided between the completed multilayer wiring boards. It becomes possible to obtain.

Also, when a resin film made of such an amorphous material is used, it is possible to use, as the metal foil, a multilayer metal foil capable of being alloyed with the conductive paste. In this case, for the metal layer on the resin film side of the multilayer metal foil, it is necessary to use a material that causes alloying with the metal filler contained in the conductive paste at a temperature at which hot pressing is possible or lower.

[0065]

As described above, in the method for manufacturing a wiring board of the present invention, the metal foil is hot-pressed onto the insulating resin base material by the pushing jig having the convex shape imitating the shape of the wiring circuit. Thus, the metal foil is punched on the insulating resin base material in accordance with the wiring pattern of the wiring circuit, and then the excess metal foil on the insulating resin base material is removed to form the wiring circuit. Therefore, a fine wiring pattern can be formed at low cost by the dry process.

Further, for example, by using a metal foil having different surface roughness on one surface and the other surface, and pushing the metal foil so that the surface having a large surface roughness contacts the connection electrode, The connectivity with the connection electrode is enhanced.

Further, for example, when the connection electrode is formed by using a conductive paste containing a metal filler,
At least one surface of the metal foil is provided with a layer of a material which is alloyed with a metal filler at a temperature below the temperature at which the insulating resin base material can be hot pressed, and the metal foil is pressed so that the layer of this material contacts the connecting electrode. You may do it. In this case, with respect to the metal foil attached on the insulating resin substrate, a large difference in adhesion strength occurs between the portion pressed by the pushing jig and the portion not pressed. Therefore, the excess metal foil on the insulating resin base material can be easily and accurately removed by a mechanical method, the work efficiency is improved, and a high-quality product can be stably manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a wiring board according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration for forming a wiring circuit on a resin film in the first embodiment example of the present invention.

FIG. 3 is a cross-sectional view showing how a wiring circuit is formed on a resin film in the first embodiment example of the present invention.

FIG. 4 is a sectional view showing a second embodiment of a wiring board according to the present invention.

FIG. 5 is a view showing a cross section of a multilayer metal foil used in a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a configuration for forming a wiring circuit on a resin film in the second embodiment example of the present invention.

FIG. 7 is a cross-sectional view showing a step of forming a wiring circuit on a resin film in the second embodiment example of the present invention.

FIG. 8 is a cross-sectional view for explaining a step of performing hot pressing again after the formation of the wiring circuit in the second embodiment example of the present invention.

FIG. 9 is an enlarged cross-sectional view of the periphery of the wiring circuit on which the hot pressing is performed again.

FIG. 10 is a cross-sectional view showing a step of stacking a plurality of wiring boards.

[Explanation of symbols]

1 ... Wiring board, 11 ... Resin film, 11a ... Via hole, 12 ... Connection electrode, 13 ... Wiring circuit, 13a ...
... Metal foil, 14 ... Pushing jig, 14a ... Convex shape part, 15a, 15b ... Hot platen

Claims (9)

[Claims] 1. A method of manufacturing a wiring board in which a wiring circuit and a connection electrode for via connection are provided on an insulating resin base material, wherein a via hole corresponding to the shape of the connection electrode is formed in the insulating resin base material. Then, the via holes are filled with a conductive paste to form the connection electrodes, and a metal foil is heated on the insulating resin base material by using a pressing jig having a convex shape imitating the shape of the wiring circuit. A wiring board, characterized in that the metal foil is pressed to bring the metal foil into contact with the connection electrode, and the excess metal foil attached to a portion of the insulating resin base material that is not pressed by the pressing jig is removed. Manufacturing method. 2. The method of manufacturing a wiring board according to claim 1, wherein the conductive paste contains a thermoplastic resin. 3. The metal foil according to claim 1, wherein one surface and the other surface have different roughness, and the surface having a high roughness is hot pressed so as to come into contact with the connection electrode. Wiring board manufacturing method. 4. The method for manufacturing a wiring board according to claim 3, wherein the conductive paste contains a metal filler having an average particle size smaller than a surface roughness Rmax of a surface of the metal foil in contact with the metal paste. . 5. The conductive paste contains a metal filler, and at least a surface of the metal foil in contact with the connection electrode is alloyed with the metal filler at a temperature not higher than a temperature at which the insulating resin base material can be hot pressed. 2. The method for manufacturing a wiring board according to claim 1, further comprising a layer of a material to be formed. 6. A layer of the material to be alloyed has a surface roughness of a contact surface with the connection electrode lower than that of a surface of the metal foil on the connection electrode side. A method for manufacturing a wiring board as described above. 7. The method of manufacturing a wiring board according to claim 1, wherein the insulating resin base material contains a thermoplastic resin. 8. When the height of the convex shape of the pushing jig is formed to be larger than the thickness of the metal foil, after removing the excess metal foil on the insulating resin substrate, the insulating The method for manufacturing a wiring board according to claim 7, wherein the resin base material is hot-pressed again. 9. A wiring board in which a wiring circuit and a connection electrode for via connection are provided on an insulating resin base material, wherein the insulating resin base material is made of a material containing a thermoplastic resin, and the connection electrode comprises: The via hole formed in the insulating resin base material is filled with a conductive paste containing a metal filler, and the wiring circuit includes the metal at a temperature not higher than a temperature at which the insulating resin base material can be hot pressed. A metal foil having a layer of a material alloying with the filler provided on one surface is used, and the metal foil is embedded in the insulating resin base material so that the layer of the alloying material contacts the connection electrode. A wiring board characterized by: