JP2003298212A - Printed wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board which is prevented from the increase of contact resistance, in the printed wiring board in which interlayer connections are obtained by embedding wiring patterns in a base and compressing a conductive paste, and to provide a manufacturing method thereof. <P>SOLUTION: Since wiring patterns 6, 9 formed on support boards 2, 7 and metal layers formed thereon, for example, electrolytic nickel plating layers 5, 8 are embedded in a base, a conduction paste 14 filled in through-holes 13 arranged in prescribed positions of the porous base is fully compressed, and the densification of the conductive material in the conduction paste 14 is enhanced. Hence the printed circuit board having low connection resistance and reliable interlayer connections can be provided. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board for mounting surface mounted components, particularly electronic components such as bare chips, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Due to recent demands for higher functionality, smaller size, and lighter weight of electronic devices centering on information and communication terminals, high integration and speed-up technologies for semiconductors are rapidly advancing.

Therefore, high density wiring and high density mounting are possible even on a printed wiring board for mounting electronic components such as bare chips in order to achieve these miniaturization and weight reduction, and at the same time, inexpensive ones are required. There is.

In order to meet the demands of the market as described above, a conductive paste is applied to the interstitial via holes (hereinafter referred to as IVH) instead of the conventional printed wiring board which basically has through-hole connection by copper plating. Full-layer IVH that can be manufactured at low cost by filling and conducting connection and forming IVH directly under the component land and between any layers
A multilayer printed wiring board having a structure (Japanese Patent Laid-Open No. 6-268345) has been developed and supplied to the market.

This multi-layered printed wiring board having an IVH structure is formed by forming a through hole in a substrate, filling the through hole with a conductive paste, and then laminating a metal foil and applying heat and pressure to form an interlayer. It is a connection.

A conventional method for manufacturing a printed wiring board will be described below.

FIG. 5 is a sectional view of steps showing a conventional method for manufacturing a printed wiring board.

First, a substrate 22 having release films 21 made of polyester or the like on both sides is prepared. As this base material, for example, a base material obtained by impregnating a non-woven fabric of resin fiber or glass fiber with a thermosetting epoxy resin is used (FIG. 5).
(A)).

Next, a through hole 23 is formed in a predetermined portion of the base material 22 (FIG. 5B), and a conductive paste 24 is filled therein. As a filling method, the conductive paste 24 is directly printed on the release film 21 (FIG. 5C).

Next, the release film 2 is formed on both sides of the substrate 22.
After peeling off 1, the metal foil such as copper foil 25 is attached to both surfaces (FIG. 5 (D)), and the base material 22 is compressed and the copper foil 25 is heated and pressed by a vacuum heat press machine. And are bonded (FIG. 5 (E)).

In this step, the conductive paste is also compressed, but at that time, the binder component is extruded from between the conductive materials, and the conductive materials and the bond between the conductive material and the copper foil are strengthened, so that the conductive paste is formed. The conductive material therein is densified, the base material is also compressed, and the epoxy resin and the conductive paste 24, which are the constituent parts of the base material 22, are hardened. As a result, the connection resistance value is low and the reliability is high. High interlayer connection can be obtained.

Thereafter, the copper foil 25 is selectively etched by a photo process to form a predetermined wiring pattern 26 (FIG. 5 (F)).

Nowadays, as the wiring density of the substrate is further increased and the diameter of the land is required to be further reduced, it is necessary to reduce the diameter of the through hole which becomes the via hole.

However, in the above-described structure and manufacturing method, when the diameter of the through hole is reduced, the initial connection resistance value increases and the variation thereof increases.

Further, reliability tests such as a temperature cycle test and a pressure cooker test (destruction test under high temperature and high pressure) have a problem that the connection resistance value varies. This is because if the diameter of the through hole becomes small, the filling property of the conductive paste becomes poor, and it becomes impossible to secure the compression ratio necessary for stabilizing the electrical connection.

Also, in the step of peeling the release film, when the through-hole diameter is small, the conductive paste is easily adhered to the release film side when the release film is peeled off and is easily removed. The filling amount of the conductive paste in the holes is reduced. As a result, it may not be possible to secure the compression of the conductive paste necessary for stabilizing the electrical connection.

Therefore, as a construction method for compensating for this reduction in compression, a printed wiring board by a transfer method and its manufacturing method have been devised.

6 and 7 are process sectional views showing a method for manufacturing a printed wiring board by a conventional transfer method.

First, a transfer plate 30 comprising a copper foil 32 as a metal foil and a supporting substrate 31 is prepared (FIG. 6).
(A)).

Next, a wiring pattern for transfer is formed on the supporting substrate having the copper foil formed thereon by a photo process.

After forming an etching resist 33 on the surface of the copper foil 32 formed on the support substrate 31 by a photo process (FIG. 6 (B)), unnecessary copper foil is removed by an etching solution such as cupric chloride. Predetermined wiring pattern 3
4 is formed (FIG. 6C), the etching resist 33 is peeled off to complete the pattern formation,
The production of the first transfer plate 30 is completed (FIG. 6D).

Next, a second transfer plate 41 having different wiring patterns 36 formed on the support substrate 35 is manufactured by the same transfer plate manufacturing method as described above (FIG. 6 (E)).

Next, a substrate 38 having release films 37 made of polyester or the like on both sides is prepared (FIG. 7).
(F)).

Next, a through hole 39 is formed in a predetermined portion of the base material 38 (FIG. 7G), and a conductive paste 40 is filled therein. As a filling method, the conductive paste 40 is directly printed on the release film 37.

Next, the release film 3 is formed on both sides of the base material 38.
7 is peeled off (FIG. 7 (H)), the first transfer plate 30 and the second transfer plate 41 produced previously are opposed to each other, and the base material 38 filled with the conductive paste 40 is overlapped therebetween. (Fig. 7
(I)) By heating and pressurizing both sides of the first and second transfer plates with a vacuum heat press machine, the base material 38 is compressed and the wiring patterns 34, 36 are provided inside the base material 38.
Are embedded and adhered to the conductive paste 40 in the through holes 39 (FIG. 7 (J)).

Next, the supporting substrates 31, 35 are chemically or mechanically removed to obtain a wiring substrate in which the wiring patterns 34, 36 are embedded in the base material 38 (FIG. 7).
(K)).

As described above, in addition to compressing the conductive paste together with the base material, the conductive paste is further compressed by burying the wiring pattern, and the conductive substance in the conductive paste is densified, so that the connection is made. A low resistance value and highly reliable interlayer connection can be obtained.

[0028]

The above-mentioned conventional printed wiring board has the following problems. In the background of the progress of finer wiring and the demand for higher precision of wiring pattern formation, it has become necessary to reduce the thickness of the copper foil 25 in order to realize it. However, if the thickness of the copper foil 25 is reduced, Although it is easy to cope with thinning, since the wiring pattern 26 is thin, the depth (thickness) of the wiring pattern 26 embedded in the base material is small. Therefore, since the compressibility of the conductive paste 24 is reduced, the initial connection resistance value is increased, resulting in a large variation in the initial connection resistance value.

Therefore, the present invention is intended to solve the above-mentioned conventional problems. Even when the via hole diameter is made small and the wiring pattern is made fine, the conductive paste can be sufficiently compressed so that the connection resistance value is low and the reliability is high. It is an object of the present invention to provide a high-quality printed wiring board and a manufacturing method thereof.

[0030]

In order to achieve the above-mentioned object, the invention according to claim 1 of the present invention is, in particular, a circuit formed on a supporting substrate and a constant thickness on the circuit,
First and second transfer plates on which a metal layer having a certain size is formed are arranged and laminated so as to face each other with an interlayer adhesive sheet interposed therebetween, and only the circuit and the metal layer are embedded in the interlayer adhesive sheet. And a printed wiring board having a configuration in which the supporting substrate is removed, whereby the conductive paste filled in the through holes provided at predetermined positions of the base material is sufficiently compressed, and Since the conductive material in the paste is densified, it is possible to realize a printed wiring board having a low connection resistance value and highly reliable interlayer connection.

The invention according to claim 2 of the present invention is
The printed wiring board according to claim 1, wherein the metal layer is formed by electrolytic plating, whereby the thickness of the metal layer for controlling the compressibility of the conductive paste can be easily set. The effect is obtained.

The invention according to claim 3 of the present invention is
The fixed thickness of the metal layer is 5 to 1 of the thickness of the interlayer adhesive sheet.
It is 0%, The printed wiring board according to claim 1, wherein a metal layer having a constant thickness is embedded inside the base material even if the thickness of the wiring pattern becomes thin due to thinning. Therefore, the conductive paste is sufficiently compressed, and a printed wiring board having a low connection resistance value and highly reliable interlayer connection can be obtained.

The invention according to claim 4 of the present invention is
The sheet for interlayer adhesion is the printed wiring board according to claim 1, characterized in that it has a conductive hole, and when multilayered by this, conduction can be taken only between required layers between arbitrary layers, Since a dead space (unnecessary space) caused by unnecessary conduction between layers is not generated, high density can be realized.

The invention according to claim 5 of the present invention is
The printed wiring board according to claim 4, wherein the conductive hole is formed by filling a conductive paste. Since there is no need to consider), the effect that the diameter can be significantly reduced can be obtained.

The invention according to claim 6 of the present invention is
The print according to claim 4, wherein the metal layer formed on the first transfer plate and the metal layer formed on the second transfer plate are electrically connected through a conduction hole. It is a wiring board, so that between any layers, conduction can be taken only between the required layers, so that it is possible to realize high density without generating dead space, and even if the filling amount of the conductive paste decreases as the diameter decreases, The circuit formed on the support substrate and the metal layer formed on the circuit sufficiently compress the conductive paste while being embedded in the interlayer adhesive sheet, so that a printed wiring board having a low connection resistance value can be realized.

The invention according to claim 7 of the present invention is
The interlaminar adhesive sheet is a printed wiring board according to claim 1, wherein the aramid nonwoven fabric epoxy resin-impregnated sheet has a specific gravity higher than that of the conventional glass nonwoven fabric epoxy resin-impregnated sheet. The small size makes the substrate lighter, which is effective in reducing the weight of the product.

The invention according to claim 8 of the present invention is
The printed wiring board according to claim 1, wherein the size of the metal layer is larger than that of the conductive hole by 40 to 150 μm, and the positional deviation tolerance is set within a certain range.
When a conventional transfer plate and an interlayer adhesive sheet having a conductive hole filled with a conductive paste are overlapped with each other, if the position shifts, the conductive paste is exposed and flows from the land to the surface of the interlayer adhesive sheet, causing a short circuit. The effect of solving the problem that has become is obtained.

The invention according to claim 9 of the present invention is
The printed wiring board according to claim 1, wherein the interlayer adhesive sheet is a porous material having compressibility, whereby the interlayer adhesive sheet is compressed, and at the same time, the conductive paste is compressed. Therefore, the binder component in the conductive paste is extruded toward the sheet for interlayer adhesion which is a porous material, the bond between the conductive substances and between the conductive substance and the copper foil becomes strong, and Since the conductive material is densified, the connection resistance value is low and a highly reliable interlayer connection can be obtained.

According to the tenth aspect of the present invention, in particular, the compressibility of the porous material having compressibility is 10 to 5
It is 0%, It is a printed wiring board of Claim 9, Comprising: When a porous material is compressed, it becomes easy to embed a circuit and a metal layer in a porous material. .
The interaction between the thickness of the embedded circuit and the thickness of the metal layer further densifies the conductive material in the conductive paste, so that a highly reliable interlayer connection having a low connection resistance value can be obtained. it can.

According to the eleventh aspect of the present invention, in particular, the resin content of the interlayer adhesive sheet is 40 to 65%.
The printed wiring board according to claim 1, wherein when the porous material is compressed, a circuit,
Since the resin wraps around the metal layer while being embedded, a printed wiring board having excellent flatness without voids can be obtained.

According to a twelfth aspect of the present invention, in particular, the steps of preparing the first and second transfer plates having the metal foil formed on the supporting substrate, and the first and second transfer plates. Selectively forming a metal layer having a constant thickness and a constant size on the metal foil, the step of forming a circuit of the metal foil using the metal layer as an etching resist, and the step of preparing an interlayer adhesive sheet; A method for manufacturing a printed wiring board, comprising: a step of laminating the circuit forming surfaces of the first and second transfer boards so as to face each other with an interlayer adhesive sheet interposed therebetween; and a step of heating and pressing the layers. As a result, the conductive paste filled in the through holes provided at the predetermined positions of the base material is sufficiently compressed, and the conductive substance in the conductive paste is densified, resulting in a low connection resistance value. Have reliable interlayer connection It is possible to realize a printed circuit board.

In the thirteenth aspect of the present invention, particularly, in the step of selectively forming the metal layer, a plating resist is formed by a photo process, and an electrolytic nickel plating layer is formed in a portion where the plating resist is not formed. The method for manufacturing a printed wiring board according to claim 12, wherein the thickness of the metal layer for controlling the compressibility of the conductive paste can be easily set. Further, since the electrolytic nickel plating layer has a high hardness, it is possible to obtain the effect of being easily embedded in the interlayer adhesive sheet by heating and pressurizing.

According to a fourteenth aspect of the present invention, in particular, the thickness of the metal layer is set to 5 to 10% of the thickness of the interlayer adhesive sheet by using an electrolytic plating process. In the method for manufacturing a printed wiring board described in 1, the thickness of the metal layer can be easily set by using the electrolytic plating process, and even if the thickness of the wiring pattern becomes thin due to thinning, a metal layer having a constant thickness can be formed. Since it is embedded inside the base material, the conductive paste is sufficiently compressed, so that it is possible to obtain a printed wiring board having low connection resistance and highly reliable interlayer connection.

According to a fifteenth aspect of the present invention, in particular, in the step of forming the circuit of the metal foil, the metal foil is dissolved and removed using an alkaline etching solution containing copper ammonium complex ions as a main component. 13. The method for manufacturing a printed wiring board according to claim 12, wherein, when the metal layer serving as an etching resist is formed by electrolytic nickel plating, the electrolytic nickel plating layer is protected when etching with an alkaline etching solution. At the same time, it is possible to obtain an effect that the circuit can be formed by melting and removing the metal foil.

The invention according to claim 16 of the present invention is the method for manufacturing a printed wiring board according to claim 12, characterized in that the metal layer is formed in a rectangular cross section.
As a result, when the interlayer adhesive sheet is compressed and the circuit and the metal layer are embedded in the interlayer adhesive sheet, the resin of the interlayer adhesive sheet wraps around the circuit and the metal layer to be embedded, and the embedded metal layer Since the width is wider than the upper width of the circuit, the peeling strength and the pulling strength can be significantly improved by the anchor effect.

According to a seventeenth aspect of the present invention, in particular, after the step of heating and pressurizing, the step of removing the supporting substrates of the first and second transfer plates is provided. 12. The method for manufacturing a printed wiring board according to 12, wherein even if foreign matter adheres to the substrate in the process of heating / pressurizing with a vacuum heat press or the like, the metal foil to be the wiring pattern is protected by the supporting substrate. As a result, it is possible to obtain an effect that it is possible to prevent scratches on the metal foil that lead to disconnection of the wiring pattern.

The invention according to claim 18 of the present invention is characterized in that, in particular, the step of removing the supporting substrate is chemical dissolution removal or mechanical polishing removal. This method has the effect that it can be easily removed at a relatively low cost by chemically dissolving the supporting substrate with sulfuric acid, hydrochloric acid or the like or by using mechanical polishing with a belt sander or the like. To be

The invention according to claim 19 of the present invention is, in particular, the method for manufacturing a printed wiring board according to claim 12, characterized in that the supporting substrate is a conductor. Since it is a conductor, it has an effect that a metal foil such as a copper foil can be easily formed on the supporting substrate by electrolytic plating.

The invention according to claim 20 of the present invention is, in particular, the method for manufacturing a printed wiring board according to claim 12, characterized in that the support substrate is a resin film.
As a result, by using the supporting substrate as a carrier, it is possible to obtain an effect that it is easy to handle in ultra-thin copper foil manufacturing equipment and transportation and can be easily peeled by a peeling machine.

The invention according to claim 21 of the present invention is the method for producing a printed wiring board according to claim 20, characterized in that the resin film has heat resistance and releasability. Therefore, even if the resin film as the supporting substrate has heat resistance even if it is heated and pressed by a vacuum hot press, it is possible to prevent welding. Further, when the supporting substrate is removed, since it has releasability, the effect of facilitating peeling and peeling can be obtained.

According to a twenty-second aspect of the present invention, in particular, the step of preparing the interlayer adhesive sheet includes a step of forming a through hole in the interlayer adhesive sheet and filling it with a conductive paste. 13. The method for manufacturing a printed wiring board according to claim 12, wherein when a multilayer is formed, only required layers can be electrically connected to each other between arbitrary layers, so that unnecessary layers are electrically connected as in the conventional case. Since a dead space that occurs due to this does not occur, there is an effect that high density can be realized.

According to a twenty-third aspect of the present invention, in particular, the interlayer adhesive sheet is an aramid nonwoven fabric epoxy resin impregnated sheet having compressibility and porosity, and the impregnated resin is in a semi-cured state. 13. The method for manufacturing a printed wiring board according to claim 12, wherein the aramid non-woven fabric epoxy resin-impregnated sheet has a smaller specific gravity than a conventional glass cloth epoxy resin-impregnated sheet, resulting in a lighter substrate. It is effective for weight reduction.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are manufacturing process diagrams of a printed wiring board according to an embodiment of the present invention.

First, a transfer plate 1 including a copper foil 3 as a metal foil and a supporting substrate 2 is prepared. A conductor such as a stainless steel plate or an aluminum foil is used as the support substrate 2, a support substrate 2 having a copper foil 3 formed by electrolytic plating is used, and a resin film is used as the support substrate 2. In some cases, a resin film laminated with copper foil is used (FIG. 1 (A)).

As for the copper foil 3, it is desirable to use an extremely thin copper foil 3 having a thickness of 10 μm or less in order to form a fine wiring pattern 6 (about 30 to 50 μm) by etching.

Next, a plating resist 4 is formed on the surface of the copper foil 3 formed on the supporting substrate 2 by a photo process (FIG. 1 (B)).

Next, an electrolytic nickel plating layer 5 having a rectangular cross section as a metal layer is formed on a portion where the plating resist 4 is not formed.
Are formed (FIG. 1C). Since this electrolytic nickel plating layer 5 has a relatively high hardness, it can be easily embedded in the interlayer adhesive sheet by heating and pressurizing in a later step.

Next, the plating resist 4 is stripped with a solution of sodium hydroxide or the like (FIG. 1 (D)). Then, using the electrolytic nickel plating layer 5 as an etching resist, unnecessary copper foil is removed by an alkaline etching solution containing copper ammonium complex ions as a main component, and a predetermined wiring pattern 6 is formed.
The formation of the first transfer plate 1 is completed by forming (FIG. 1 (E)).

The reason why the copper foil is dissolved and removed by using the alkaline etching solution containing copper ammonium complex ion as a main component is that the copper foil is dissolved and removed while protecting the electrolytic nickel plating layer 5 as the etching resist. This is because a circuit can be formed.

Next, a second transfer plate 10 having different wiring patterns 9 formed on the support substrate 7 is manufactured by the same method as described above for manufacturing a transfer plate (FIG. 1 (F)).
The preparation of the transfer plates 1 and 10 is completed.

Next, a porous substrate 12 having release films 11 made of polyester or the like on both sides is prepared. As the porous substrate 12, an aramid non-woven fabric epoxy resin-impregnated sheet having a thickness of 50 to 100 μm is used (FIG. 2 (G)).

Since the aramid non-woven fabric epoxy resin-impregnated sheet has a small specific gravity, it is effective for weight reduction. Further, since the aramid nonwoven fabric has good laser processability, it is suitable for opening minute holes at high speed. Further, since the aramid non-woven fabric is a resin and has good adhesiveness with the epoxy resin, the occurrence of bleeding due to the flow of the conductive paste is significantly reduced.

If the resin content is in the range of 40 to 65%, it is possible to select one having excellent physical and mechanical properties and electrical properties as a substrate, but it is preferably 55 to 6
It is good to select one that is 0%. As a result, when the porous substrate 12 is compressed, the resin wraps around the wiring pattern 9 and the metal layer while being embedded,
A substrate having excellent flatness without voids can be obtained.

When the aramid non-woven fabric epoxy resin-impregnated sheet as the interlayer adhesive sheet is selected in the above resin content range of 40 to 65%, the compressibility of the porous substrate 12 is in the range of 10 to 50%. When selected in the range of 55 to 60%, the compression rate can be set to 30 to 40%.

Here, when the compressibility is 10% or less, the densification of the conductive material in the conductive paste is poor, and when the diameter of the through hole is as small as 50 μm, the connection resistance value increases, and When the compression rate is 50% or more, the conduction hole is deformed,
It is not suitable because the smoothness of the substrate is impaired and the resistance value tends to vary widely.

Therefore, the resin content is 55 to 60%.
By selecting an aramid non-woven fabric epoxy resin-impregnated sheet as an inter-layer adhesive sheet having a compressibility of 30 to 40%, conductive connection as well as physical and mechanical characteristics as a substrate can be achieved. A substrate having stable resistance and excellent flatness can be obtained.

Next, a diameter of 50 to 100 is applied to a predetermined portion of the aramid non-woven fabric epoxy resin-impregnated sheet by a laser processing machine or the like.
The through hole 13 of μm is formed (FIG. 2 (H)), and the through hole 13 is formed.
Is filled with the conductive paste 14. As a filling method,
After setting the aramid nonwoven fabric epoxy resin-impregnated sheet having the through holes 13 in a screen printing machine or the like, the conductive paste 14 is directly printed on the release film 11.

Next, the release film 11 was peeled off from both sides of the aramid nonwoven fabric epoxy resin-impregnated sheet (see FIG. 2).
(I)), an aramid non-woven fabric epoxy resin-impregnated sheet as an interlayer adhesive sheet in which the first transfer plate 1 and the second transfer plate 10 prepared above are opposed to each other and the conductive paste 14 is filled between them. Overlap (FIG. 2 (J)).

Thereafter, the first and second vacuum hot presses were used.
By heating and pressurizing the transfer plate from both sides, the aramid nonwoven fabric epoxy resin-impregnated sheet is compressed and the wiring patterns 6, 9 and the electrolytic nickel plating layers 5, 8 are embedded inside the aramid nonwoven fabric epoxy resin-impregnated sheet, It is bonded to an aramid nonwoven fabric epoxy resin-impregnated sheet (FIG. 2 (K)).

The supporting substrates 2 and 7 used for the first transfer plate 1 and the second transfer plate 10 are made of a resin film having heat resistance and releasability so that the supporting substrates 2 and 7 are extremely thin. It is easy to handle in the copper foil manufacturing equipment and transportation, and it is possible to prevent welding even during heating / pressurizing in a vacuum hot press, and further, it becomes easy to remove and peel off the supporting substrates 2 and 7.

Finally, the supporting substrates 2 and 7 are chemically dissolved in sulfuric acid, hydrochloric acid or the like, or removed by using a mechanical polishing method such as a belt sander which can be easily performed at a low cost. A wiring board in which 9 and electrolytic nickel plating layers 5 and 8 are embedded in an aramid nonwoven fabric epoxy resin-impregnated sheet is obtained (FIG. 2 (L)).

Here, the relationship with the electrolytic nickel plating layer 5 as the metal layer embedded in the aramid nonwoven fabric epoxy resin impregnated sheet as the interlayer adhesion sheet will be described below.

The aramid nonwoven fabric epoxy resin-impregnated sheet has a thickness of 50 μm and a compressibility of 30 to 40%, and the diameter of the through hole 13 to be formed is set to 50 μm.

Further, since the line width and the line width of the wiring patterns 6 and 9 on the first transfer plate 1 and the second transfer plate 10 are set to 30 μm, the thickness of the copper foil 3 should be 5 μm. use.

At this time, the thickness of the electrolytic nickel plating layer 5 as the metal layer is 5 to 10 times the thickness of the interlayer adhesive sheet.
%, The depth embedded in the interlayer adhesive sheet is 7.5 on each side.
It becomes 10 μm, and stable pressurization is possible within a compression rate range of 30 to 40% of the aramid nonwoven fabric epoxy resin-impregnated sheet.

The thickness of the interlayer adhesive sheet is 100 μm.
m (the compressibility is 30 to 40%), the diameter of the through hole 13 to be formed is 100 μm, and the wiring patterns 6 and 9 are used.
Between the lines, the line width is 50 μm, and the thickness of the copper foil 3 is 10 μm.
Even when a very thin m is used, the thickness of the electrolytic nickel plating layer 5 is set to 5 times the thickness of the interlayer adhesive sheet.
The same effect of connection reliability can be obtained by setting the thickness to 10%, which is 5 to 10 μm.

As a result, even if the wiring patterns 6 and 9 are thinned, a metal layer having a constant thickness is embedded inside the base material for finer patterning, so that the conductive paste is sufficiently compressed. Thus, a printed wiring board having a highly reliable interlayer connection with a low connection resistance value can be obtained.

If the thickness of the copper foil 3 is 10 μm or more, it becomes difficult to form a wiring pattern by etching. On the contrary, if the thickness of the copper foil 3 is 5 μm or less, it becomes difficult to carry and handle in the manufacturing process, and the material cost further increases. It leads to and is not feasible.

When such ultrathin copper foil is used, the supporting substrates 2 and 7 of the first and second transfer plates are made to be conductors such as aluminum foil, so that electrolysis is performed on the supporting substrates 2 and 7. A metal foil such as a copper foil can be easily formed by plating, and by using the ultra-thin copper foil supporting substrates 2 and 7 which are difficult to handle in manufacturing equipment and transportation, as a carrier, It will be easy.

Further, since the size is stabilized by fixing the base material with the supporting substrates 2 and 7, the positional accuracy due to expansion and contraction of the base material, which has been a problem mainly in the heat treatment process in the manufacturing process in the past, is high. Defects are reduced.

Further, it is desirable that the size of the electrolytic nickel plating layer 5 is 40 to 150 μm larger than that of the conduction hole, and the conductive paste 14 in the through hole 13 is formed in the electrolytic nickel plating layer even if the positional deviation occurs during lamination. The conductive paste 14 is less likely to be exposed because it is covered with 5.
The amount of positional deviation is increased. Moreover, since the metal layer having a wide rectangular cross section is embedded in the base material, the peeling strength and the pulling strength are significantly improved by the anchor effect.

Here, when it is 40 μm or less, it becomes difficult to deal with the positional deviation, and when it is 150 μm or more, the wiring accommodability in the wiring design deteriorates, so the above range is preferable.

As described above, according to the present embodiment, conventionally, the compressibility of the conductive paste 40 changes depending on the thickness of the copper foil as shown in FIGS. 3A and 3B. 3 (C)
Even if the copper foil as the wiring pattern is thin as shown in Fig. 5, the thickness of the conductor layer embedded in the base material is equal to the thickness of the electrolytic nickel because the electrolytic nickel plating layer as the metal layer is formed on the copper foil. It can be determined by the thickness of the plating layer,
Since the compressibility of the conductive paste can be controlled by the thickness of the electrolytic nickel plating layer, the copper foil as a wiring pattern is thinned to form a fine pattern, and the connection resistance value is low, so that a highly reliable printed wiring board can be obtained. It becomes possible to obtain.

Further, as shown in FIG. 4 (A), conventionally, the conductive paste may be exposed 15 due to the position shift, but in the present embodiment, as shown in FIG. 4 (B), the conductive paste has a rectangular shape. Since the electrolytic nickel plating layer having a cross section is formed, the conductive paste is less likely to be exposed, and the allowable amount of displacement is increased.

[0086]

As described above, according to the present invention, the wiring pattern formed on the substrate and the metal layer formed on the wiring pattern are embedded in the substrate so that the wiring pattern is provided at a predetermined position of the substrate. The conductive paste filled in the through holes will be compressed sufficiently, and the conductive material in the conductive paste will be densified, so that the connection resistance value is low and the printed wiring with highly reliable interlayer connection. A board can be realized.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a printed wiring board according to an embodiment of the present invention.

FIG. 2 is a process sectional view showing a method for manufacturing a printed wiring board according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view for comparing the compressed state of the conductive paste in the embodiment of the present invention.

FIG. 4 is a cross-sectional view for comparing interlayer connection states when interlayer positions are displaced in the embodiment of the present invention.

FIG. 5 is a process sectional view showing a conventional method for manufacturing a printed wiring board.

FIG. 6 is a process sectional view showing a conventional method for manufacturing a printed wiring board.

FIG. 7 is a process sectional view showing a conventional method for manufacturing a printed wiring board.

[Explanation of symbols]

1,10 Transfer plate 2,7 support substrate 3 copper foil 4 Plating resist 5,8 Electrolytic nickel plating layer 6,9,34,36 wiring pattern 11 Release film 12,38 Porous substrate 13 through holes 14,40 Conductive paste 15 Flow of conductive paste (exposure of conductive paste)

Claims (23)

[Claims] 1. A circuit formed on a supporting substrate and first and second transfer plates having a metal layer having a certain thickness and a certain dimension formed on the circuit face each other with an interlayer adhesive sheet interposed therebetween. A printed wiring board having a configuration in which the circuit and the metal layer are embedded in an interlayer adhesive sheet, and the supporting substrate is removed. 2. The printed wiring board according to claim 1, wherein the metal layer is formed by electrolytic plating. 3. The printed wiring board according to claim 1, wherein the certain thickness of the metal layer is 5 to 10% of the thickness of the interlayer adhesive sheet. 4. The printed wiring board according to claim 1, wherein the interlayer adhesive sheet has a conductive hole. 5. The printed wiring board according to claim 4, wherein the conductive hole is formed by filling a conductive paste. 6. The metal layer formed on the first transfer plate and the metal layer formed on the second transfer plate are electrically connected through a conduction hole. The printed wiring board according to item 4. 7. The interlaminar adhesive sheet is an aramid non-woven fabric epoxy resin-impregnated sheet.
The printed wiring board described in. 8. The size of the metal layer is 40 to 150 from the through hole.
The printed wiring board according to claim 1, wherein the printed wiring board has a size of only μm. 9. The printed wiring board according to claim 1, wherein the interlayer adhesive sheet is a porous material having compressibility. 10. The printed wiring board according to claim 9, wherein the compressibility of the compressible porous material is 10 to 50%. 11. The resin content of the interlayer adhesive sheet is
It is 40-65%, The printed wiring board of Claim 1 characterized by the above-mentioned. 12. A step of preparing first and second transfer plates having a metal foil formed on a supporting substrate, and a step of providing a constant thickness and a constant dimension on the metal foil of the first and second transfer plates. A step of selectively forming a metal layer having the metal layer, a step of forming a metal foil circuit using the metal layer as an etching resist, a step of preparing an interlayer adhesive sheet, and a circuit formation of the first and second transfer plates A method of manufacturing a printed wiring board, comprising: a step of laminating the surfaces so as to face each other with an interlayer adhesive sheet interposed therebetween; 13. The method according to claim 12, wherein the step of selectively forming the metal layer comprises forming a plating resist by a photo process and forming an electrolytic nickel plating layer on a portion where the plating resist is not formed. Manufacturing method of printed wiring board. 14. The method of manufacturing a printed wiring board according to claim 12, wherein the thickness of the metal layer is set to 5 to 10% of the thickness of the interlayer adhesion sheet by using an electrolytic plating process. 15. The printed wiring according to claim 12, wherein in the step of forming the circuit of the metal foil, the metal foil is dissolved and removed by using an alkaline etching solution containing copper ammonium complex ions as a main component. Method of manufacturing a plate. 16. The method of manufacturing a printed wiring board according to claim 12, wherein the metal layer is formed in a rectangular cross section. 17. The method for manufacturing a printed wiring board according to claim 12, further comprising a step of removing the supporting substrates of the first and second transfer plates after the step of applying pressure and heating. 18. The method for manufacturing a printed wiring board according to claim 17, wherein the step of removing the supporting substrate is chemical dissolution removal or mechanical polishing removal. 19. The method of manufacturing a printed wiring board according to claim 12, wherein the support substrate is a conductor. 20. The method for manufacturing a printed wiring board according to claim 12, wherein the support substrate is a resin film. 21. The method of manufacturing a printed wiring board according to claim 20, wherein the resin film has heat resistance and releasability. 22. The step of preparing an interlayer adhesive sheet,
The method for manufacturing a printed wiring board according to claim 12, further comprising the step of forming a through hole in the interlayer adhesive sheet and filling it with a conductive paste. 23. The printed wiring according to claim 12, wherein the interlayer adhesive sheet is an aramid nonwoven fabric epoxy resin impregnated sheet having compressibility and porosity, and the impregnated resin is in a semi-cured state. Method of manufacturing a plate.