JP2002198658A - Prepreg and method of manufacturing the same, and method of manufacturing wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate such a problem that when transferring a fine conductor layer such as a metal foil on the surface of a prepreg formed of glass woven fabric and organic resin, a wiring pattern deforms, generating short circuits, or vias are discontinued, generating conduction defects. SOLUTION: Rigid plates are laminated on both faces of a sheet body which is glass woven fabric impregnated with thermosetting resin, and then the sheet body is heat-treated at 40-220 deg.C while being pressureized at 200 MPa or above, to be turned fine in texture. Then, a porous layer containing thermosetting resin is formed at least on one face of the fine sheet to obtain a prepreg which comprises the fine layer (a) which is formed of the glass woven fabric (x) impregnated with the thermosetting resin (y) and which has a porosity of 5% or above, and the porous layer (b) which contains thermosetting resin and has a porosity of 10 to 50% and is formed on one face of the fine layer (a) in the thickness of 1-30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg suitable for forming an insulating substrate for a wiring board for manufacturing a wiring board, a method for manufacturing the same, a package for housing a semiconductor element and a multilayer wiring board using the same. The present invention relates to a method for manufacturing a wiring board suitable for such applications.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size.
In recent years, with the development of portable information terminals and the spread of so-called mobile computing in which a computer is carried and operated, there is a tendency that a smaller, thinner, and higher-definition multilayer wiring board is required.

[0003] Further, electronic devices that require high-speed operation, such as communication devices, have been widely used. The requirement for high-speed operation includes various requirements such as accurate switching of high-frequency signals. In order to cope with such electronic devices, a multilayer printed wiring board suitable for high-speed operation is required.

In order to perform high-speed operation, it is necessary to reduce the length of wiring and shorten the time required for transmitting an electric signal. In order to reduce the length of the wiring, there is a tendency for a small, thin, and high-definition multilayer wiring substrate in which the width of the wiring is reduced and the gap between the wirings is reduced. A wiring board having such a fine high-density wiring circuit is a conventional printed circuit board in which a via hole is formed through a core substrate with respect to a core substrate, and plating and the like are applied to the inside of the via hole to perform interlayer connection. In many cases, circuit design was limited by via holes, and high-density wiring was difficult.

Also, a so-called build-up method has been developed in which an insulating layer and a wiring circuit layer are alternately coated and plated on a predetermined substrate surface, or a via hole is formed to form a multilayer structure. Therefore, it was difficult to achieve high-density wiring. In addition, in the case of multi-layering by the build-up method, if a process such as forming a wiring circuit layer by an etching method or applying a conductor to the inner surface of a via hole by plating or the like is repeated, the insulating layer is etched. Although it is immersed in a solution or plating solution, as the number of layers increases with the increase in wiring density, the number of times that the insulating layer is immersed in these chemicals increases, and as a result, the insulating layer itself absorbs moisture and deteriorates. There was a problem that it would. Further, since the process is complicated as a whole, it has to be an expensive wiring board, and has not been used for a general wiring board.

In general, a prepreg using glass cloth for an organic resin is mainly used as an insulating material used as a core substrate of a wiring board, and the mechanical and thermal characteristics of the wiring board are reduced. Have improved.

In order to respond to such a demand for high-density wiring, a process similar to the manufacturing process of a ceramic multilayer wiring board,
That is, a multilayer printed wiring board in which a plurality of prepregs on which via-hole conductors and wiring circuit layers are formed is laminated has been proposed by Japanese Patent Application Laid-Open No. 10-27959.

In this method, specifically, after forming a via hole in a prepreg and filling a metal powder to form a via hole conductor, the transfer sheet having a wiring circuit layer made of a metal foil formed on the surface thereof in advance is used to form the via hole conductor. The wiring circuit layer is transferred to form a wiring circuit layer to form a single-layer wiring sheet, and a plurality of wiring sheets created in the same manner are laminated and integrated to form a multilayer.

[0009]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 10-2 is disclosed.
In the transfer method proposed by No. 7959, the prepreg can be manufactured by a dry process that is not immersed in a chemical such as an etching solution or a plating solution, so that the prepreg is not deteriorated, and the prepreg is formed by heat and pressure. It has advantages such as excellent flatness because it is embedded in the surface.

However, a dense metal foil wiring circuit layer is transferred to a prepreg made of a glass woven fabric and an organic resin.
In the case of embedding, there is a problem that the resin flows following the irregularities of the glass woven fabric of the prepreg, deforms the wiring pattern, and in severe cases, the circuit is short-circuited.

A conventional prepreg is made of a composite material obtained by impregnating a thermosetting organic resin into a woven fabric obtained by bundling dozens to hundreds of fibrous bodies. The wiring pattern is transferred without any problem. Even if there is no sufficient pressure applied to the portion where there is no wiring pattern, a sufficient amount of resin is not impregnated in the glass woven fabric bundle, resulting in voids. When the gap becomes a design circuit in which the pitch between vias is narrowed, metal powder in the via migrates along the gap when a voltage is applied, leading to insulation deterioration (CAF: Conductor).
ave Anordic Filaments).

Further, when the pattern is transferred to the via forming portion and cured, the resin layers above and below the glass woven fabric flow, and the via is deformed. In the worst case, there were problems such as breakage leading to open failure.

Accordingly, the present invention solves the above-mentioned conventional problems, and the wiring pattern is deformed even when a dense conductor layer such as a metal foil is transferred onto the surface of a prepreg made of a glass woven fabric and an organic resin. To provide a prepreg capable of manufacturing a highly reliable wiring board that does not cause a short circuit and does not cause a conduction failure due to disconnection of a via, and provides a highly reliable prepreg using such a prepreg. An object of the present invention is to provide a method of manufacturing a wiring board for manufacturing a wiring board with a high yield.

[0014]

Means for Solving the Problems As a result of repeated studies on the above object, the present inventor has found that a resin near a glass woven cloth and
The inventors have found that, by making the difference in the porosity of the resin on the surface, it is possible to form a wiring pattern and a via without deformation, and to prevent voids in the glass woven fabric that cause CAF, and have reached the present invention.

That is, the prepreg of the present invention has a porosity containing a thermosetting resin on at least one surface side of a dense layer having a thermosetting resin impregnated in a glass woven fabric and having a porosity of 5% or less. Is characterized in that a porous layer of 10 to 50% is provided. In addition, the said porous layer is 1
Desirably, the thickness is set to 30 μm. Further, it is used for forming a wiring circuit layer made of metal foil by such a transfer method. The thermosetting resin is desirably polyphenylene ether. Further, it is preferable that the volume ratio of the glass woven fabric and the thermosetting resin in the whole is in a ratio of 20:80 to 80:20.

Further, as a method for producing such a prepreg, (a) a step of producing a sheet body in which a thermosetting resin is impregnated into a glass woven fabric; and (b) both sides of the sheet body,
A step of laminating a rigid plate and performing heat treatment at a temperature of 40 to 220 ° C. while applying a pressure of 200 MPa or more to densify; and (c) applying heat to at least one surface of the densified sheet body. Forming a porous layer containing a curable resin.

In order to manufacture a wiring board using the above prepreg, a via hole is formed at a predetermined portion of the prepreg, and a conductive paste containing a metal powder is filled in the via hole to form a via hole conductor. Forming a via-hole conductor, and a transfer step of transferring a wiring circuit layer made of a metal foil previously formed on the surface of the transfer sheet to the surface of the prepreg on which the via-hole conductor is formed,
A thermosetting step of heating the prepreg on which the via-hole conductors and the wiring circuit layer are formed to harden the thermosetting resin.

Further, in order to manufacture a multilayered wiring board, it can be manufactured by including a step of laminating a plurality of prepregs before the above-mentioned thermosetting step.

According to the prepreg of the present invention, the prepreg is suitably used for forming a wiring circuit layer made of a metal foil by a transfer method, and comprises a dense layer obtained by impregnating a glass woven fabric with a thermosetting resin. By forming a porous layer containing a thermosetting resin on the surface, when the wiring circuit layer is transferred and formed on the surface of such a prepreg, the wiring circuit layer moves along the irregularities of the glass woven cloth. Thus, electrical short circuit can be prevented.

Further, by densifying the vicinity of the glass woven fabric, voids in the glass woven fabric which cause CAF can be eliminated, and impregnation failure due to pressure imbalance due to the presence or absence of the wiring circuit layer can be prevented.

According to the method of manufacturing a wiring board of the present invention, after forming a via-hole conductor on the prepreg, a wiring circuit layer made of a metal foil is transferred to the surface of the via-hole conductor, thereby forming the wiring circuit layer. At the same time, while preventing the occurrence of voids in the glass woven fabric, and because the wiring circuit layer can be easily embedded on the surface of the prepreg without deformation of the via hole conductor and the conductor circuit pattern, while improving the flatness of each wiring board, The electrical connection between the wiring circuit layer and the via-hole conductor can be improved, and further, the occurrence of a short circuit between the via-hole conductors or between the via-hole conductor and the wiring circuit layer can be prevented, and the reliability of the circuit can be improved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a prepreg of the present invention comprises a composite containing a glass woven fabric x and at least one or more thermosetting resins y.

The glass woven fabric 1 is formed by knitting a bundle formed by bundling several hundreds of glass fibers into a thread shape, and a glass fiber having a diameter of 1 to 20 μm is suitable. Those having a diameter of about 50 to 100 μm in terms of a circle are desirable.

On the other hand, as the thermosetting resin 2, for example, P
Examples thereof include PE (polyphenylene ether), BT resin (bismaleimide triazine), epoxy resin, polyimide resin, fluororesin, and phenol resin, and further contain a curing agent for these resins.

It is desirable that the thermosetting resin contained in the prepreg contains an inorganic filler as appropriate in order to control the strength of the prepreg and the porosity of the sheet described later. As the inorganic filler used,
Known materials such as SiO ₂ , Al ₂ O ₃ , AlN, and SiC can be used. In such a case, it is appropriate that the thermosetting resin and the inorganic filler are compounded in a volume ratio of 15:85 to 90:10. In addition, the surface of the glass woven fabric and the inorganic filler, in order to improve the paintability with the resin,
Coupling treatment may be performed.

According to the present invention, as shown in FIG. 1, a dense layer a containing a thermosetting resin y in a glass woven fabric x and a porous layer containing a thermosetting resin on at least one surface thereof. A significant feature is that the layer b is formed.

In the dense layer a, the porosity is 5
% Or less, especially 3% or less, and if the porosity is higher than 5%, sufficient pressure is not applied to the portion where the wiring circuit layer is not formed during transfer or curing, and the glass weave Voids remain in the cloth, resulting in CAF and insulation failure.

The porosity of the porous layer b is 10
It is important that it is ５０50%, especially 15-40%.
This is because when the porosity is smaller than 10%, when air is entrained between the metal foil and the prepreg when the metal foil or the wiring circuit layer made of the metal foil is bonded or transferred to the prepreg surface. The air cannot be released out of the system through the pores and remains as a void between the metal foil and the prepreg, which lowers the flatness of the wiring circuit layer surface and causes poor transfer and poor adhesion. This is because it becomes easier. Conversely, if it is larger than 50%, for example, when a via hole is formed and the conductive paste is buried in the via hole, the conductive paste is buried even inside the pores, especially when the pitch between the via holes is narrow.
An electrical short may occur between adjacent vias.

Further, if the thickness of the porous layer b in the prepreg is too large, the foot into which the conductor pattern to be transferred is driven as a wedge does not reach the resin or glass woven cloth having low fluidity therein, and the transfer or hardening during the transfer or curing. If the pattern is severely deformed at the same time as the resin flows, a short circuit may occur between the conductor patterns. Therefore, the thickness of the porous layer b is desirably 1 to 30 μm.

The surface of this prepreg has an average surface roughness (Ra) of 4 μm or less and a maximum surface roughness (Rmax).
Is not more than 30 μm, it is possible to prevent the deformation, disconnection, and transfer failure of the wiring that occur when a fine wiring is formed at the time of forming the wiring circuit, and it is possible to easily form the conductor in the through via hole.

(Manufacturing Method) Next, a method of manufacturing the prepreg of the present invention will be described with reference to FIGS. FIG.
FIG. 3 is a process chart of a method of manufacturing a prepreg, and FIG. 3 is a schematic view for explaining a method of heat-treating the prepreg. 1)
First, the glass woven fabric 3 is impregnated with the thermosetting resin 1. As shown in FIG. 2, the viscosity is 5 to 50 poise, preferably 5 to
The varnish-like thermosetting resin 1 of ~ 30 poise was stored in the container 2 and the varnish-state thermosetting resin 1 was impregnated in the glass woven fabric 3 by passing the glass woven fabric 3 through it. Thereafter, the sheet body A is dried to produce a semi-cured sheet body A.

The sheet A can be wound into a roll or cut into a predetermined size depending on the use in a later step. At this time, the average surface roughness (Ra) of the sheet body A usually exceeds 50 μm.

Next, as shown in FIG. 3, at least one side and, if necessary, both sides of the sheet body A prepared as described above are sandwiched by the release film 4 and both sides are made of stainless steel. It is set in a press machine 6 that can be heated and pressurized by sandwiching it between rigid rigid plates 5.

The release film 4 used at this time has a thickness of about 30 to 100 μm, and its contact surface with the sheet A has an average surface roughness (Ra) of 10 μm or less, particularly 5 μm.
It is desirable that: The release film 4 is preferably made of polyethylene terephthalate (PET), Teflon-based, polyolefin-based, polyimide-based, or the like, and the surface of which is subjected to a surface treatment such as Si is also effective.

Then, the sheet A sandwiched between the release films 4 is further sandwiched between rigid plates 5 such as a stainless steel plate. The rigid plate 5 is preferably made of a rigid body having a thickness of 0.1 to 2 mm, and has an average surface roughness (R
a) is also close to a mirror surface of 10 μm or less, preferably 5 μm or less, and the maximum surface roughness (Rmax) of the surface is 70 μm.
μm or less, preferably 50 μm or less.

On the other hand, examples of a heating and pressurizing device include a single-axis single-acting press, a two-axis double-acting press, a two-axis roll-type laminator, and a hydrostatic press 6. The sheet A is subjected to the heating and pressurizing treatment using such an apparatus.

It is effective to perform the treatment at a heating temperature of 40 to 220 ° C., preferably in a range of ± 50 ° C. around a temperature at which the melt viscosity of the resin impregnated in the woven or non-woven fabric becomes a minimum value. When the heating temperature is lower than 40 ° C., the viscosity of the resin is poorly reduced, cannot follow the surface state of the release film, and it is difficult to densify the resin because fluidization does not occur. If it is too high, the resin component is decomposed, and the resin properties are degraded and pores are generated.

Further, the pressure condition must be 200 MPa or more, preferably 200 to 1000 MPa. This is because if the pressure is less than 200 MPa, the smoothing of the fiber and the penetration of the resin into the woven fabric are weak, and the porosity is 5%.
This is because it is difficult to densify below. However, 10
If it is larger than 00 MPa, depending on the resin, there is a tendency that the molten resin flows out or residual stress is generated in the fiber after the pressure treatment, and the maximum surface roughness tends to be large. The heating time under pressure is desirably about 10 to 180 seconds. By such a treatment, the porosity of the sheet A after the treatment is reduced to 5% or less, particularly 3% or less.

Next, a porous layer having a thickness of 1 to 30 μm is formed on at least one surface of the heat-pressurized sheet A. In forming this porous layer, the sheet body A subjected to the pressure and heat treatment is passed through a container having a varnish-like thermosetting resin having a viscosity of 5 to 50 poise, desirably 5 to 30 poise. By drying, the prepreg of the present invention in which the porous layer is formed on the surface of the dense sheet body A can be produced.

As another method, the porous layer can also be formed by applying the varnish-like thermosetting resin to at least one surface of the sheet A subjected to the heat and pressure treatment. .

According to the present invention, it is important that the porosity of the porous layer after drying is from 10 to 50%. Can be controlled by the composition, amount of solvent, and the like. In particular, the amount of porosity can be easily controlled by mixing an inorganic filler into the thermosetting resin. That is, the pore size can be increased as the content of the inorganic filler is larger or as the particle size of the inorganic filler is larger.

The thickness of the porous layer can be adjusted to an arbitrary thickness by adjusting the viscosity of the varnish and the number of coatings.

Next, a method for manufacturing a wiring board, particularly a multilayer wiring board using the above prepreg will be described with reference to FIG. First, for prepreg 10 (a),
A desired via hole 11 is formed by punching, laser or the like in an uncured state (B stage state) (b), and a conductive paste is filled in the via hole 11 to form a via hole conductor 12 (c).

The conductor paste is made of copper, aluminum, gold,
It is composed of a metal powder mainly composed of at least one or two or more alloys selected from the group consisting of silver, a solvent, a thermosetting resin and a curing agent. The solvent is α-terpineol, 2-
Octanol or a thermosetting resin liquid at room temperature is used. As the thermosetting resin and the curing agent, a resin having the same composition that does not hinder the curing of the prepreg or a resin that cures at the same temperature is selected. This is used to maintain the shape retention of the conductive pastes after curing.

Next, after the metal foil 14 is adhered to the surface of the transfer sheet 13 (d), a resist 15 is applied (e), exposure and development (f), and etching is performed to form a wiring circuit layer 16 (g). ). As the transfer sheet 13, a sheet having mechanical characteristics and dimensional stability that can withstand processes such as etching when forming the wiring circuit layer 16 is used, and a polyethylene-based sheet is preferably used. Further, as an adhesive for bonding the metal foil, an acrylate ester which is resistant to acid and alkali is preferably used.

Thereafter, the transfer sheet 13 on which the wiring circuit layer 16 is formed is aligned and laminated on the prepreg 10 on which the via-hole conductors 12 are formed (h), and the prepreg in the B-stage state is heated to 70 to 200 ° C. While applying a pressure to the extent that the wiring circuit layer 16 can be embedded in the surface of the prepreg 10 (i), the transfer sheet 13 is then peeled off (j), whereby the wiring circuit layer 16 is removed from the prepreg 10.
To form a single-layer wiring sheet a (k). The pressure for embedding the wiring circuit layer 16 is desirably 100 MPa or more, particularly preferably in the range of 200 to 700 MPa.

In the transfer step, the wiring circuit layer 16 formed on the prepreg 10 having the predetermined pores is defined by the contraction or compressibility of the prepreg 10 in the thickness direction and the surface of the prepreg 10 and the wiring circuit layer. 1
The six surfaces can be flattened so as to be flush with each other. The via-hole conductor 12 is compressed in the thickness direction by burying the wiring circuit layer 16, so that the filling property is improved and the resistance can be reduced.

When the wiring substrate is a single layer, the wiring circuit layers 16 are formed on both sides of the prepreg 10 and heated to a temperature at which the thermosetting resin in the prepreg 10 is completely cured, thereby forming one layer of the insulating layer. Can be manufactured.

When a multilayer wiring board is manufactured,
After the prepreg having the wiring circuit layer 16 transferred and formed on only one side or both sides is formed by the same process as above, these are aligned and laminated, and then heated to a temperature at which the thermosetting resin in the prepreg is completely cured. By doing so, a multilayer wiring board can be manufactured.

[0050]

EXAMPLES (Preparation of prepreg) A glass cloth woven with E glass was 50% by volume, and polyphenylene ether (P) was used.
PE) 50% by volume of resin, PP in glass cloth
FIG. 2 shows a Teflon release film having an average surface roughness (Ra) of 0.3 μm and a stainless steel plate having an average surface roughness of 3 μm and a maximum surface roughness of 15 μm on the front and back surfaces of the prepreg impregnated with the E resin. As shown, they were sequentially arranged and sandwiched. Then, the laminate is set on a single-axis single-acting press capable of vacuum processing, and is set at a temperature of 135 ° C. and 500 MPa.
Heat treatment was performed under the following conditions. The porosity of the surface of the heat-treated sheet was measured.

Further, if necessary, polyphenylene ether (P
A varnish consisting of 60% by volume of PE) resin and 40% by volume of SiO ₂ filler was impregnated on the prepreg to obtain a prepreg having a two-layer structure.

The porosity of the surface of the prepared prepreg was measured by a scanning electron microscope (SE) from the surface direction.
M) From the photograph, the area of the pores and the area of the resin part were determined, and the area ratio of the pores shown in the whole was determined to be the porosity. The porosity was measured by the Archimedes method, and the average open pore diameter was measured by the mercury intrusion method. The results are shown in Table 1.

Next, a via hole having a diameter of 0.1 mm was formed at a predetermined position by punching using each of the prepregs shown in Table 1, and the via hole had an average particle size of 4 μm.
m is filled with a metal paste obtained by mixing 100 parts by weight of copper powder coated with silver, 0.2 parts by weight of cellulose, and 10 parts by weight of 2-octanol to form a via-hole conductor.
It was dried by heating at 0 ° C. for 60 minutes.

After that, a copper foil having a thickness of 12 μm was bonded
A wiring circuit layer for the front surface and a wiring circuit layer for the back surface were formed on the copper foil of the transfer sheets by a photoresist method. Then, the transfer sheet is positioned and superimposed on the front side and the back side of the insulating substrate on which the via-hole conductor is formed, and a pressure of 50 MPa is applied to at least the via-hole conductor formation position, and the wiring circuit layer is formed from both ends of the via-hole conductor. Was embedded in an insulating layer to produce a core wiring sheet. At this time, the minimum diameter of the wiring circuit layer provided at the end of the via-hole conductor was 0.2 mm.

Similarly, four wiring sheets having a wiring circuit layer formed only on one side of the prepreg having via-hole conductors were prepared, and the two wiring sheets were positioned on the upper and lower surfaces of the core wiring sheet. After lamination, temperature 200
The composition was cured at a temperature of 200 ° C. and a pressure of 200 MPa to prepare a multilayer wiring board having six wiring circuit layers. In this circuit, 500
Via-hole conductors of holes were formed, and they were alternately connected by wiring circuit layers formed on the front side and the back side, thereby forming a series-connected circuit.

Then, 50 samples were prepared for each sample, the initial resistance at both ends of the series circuit was measured, and a defect that caused a conduction defect (open), insulation defect (short circuit), or appearance defect (displacement of wiring, etc.) occurred. The numbers are shown in Table 1. In addition, as a reliability evaluation of the insulation between the walls of the via hole conductor, H
AST (130 ° C./85% RH / 5.5 V) was performed for 300 hours, 50 samples were measured for each sample, and the number of samples having a value of 10 ⁸ Ω · cm or less after the test was shown in Table 1.

[0057]

[Table 1]

As is clear from the results in Table 1, the porosity of the prepreg near the glass woven fabric was larger than 5%.
o. In No. 6, the initial resistance and the appearance were no problem.
Many defects occurred after the AST test, and CAF also occurred.
Further, the sample N having a porosity on the surface of less than 10%
o. In No. 1, transfer failure occurred frequently, and electrical characteristics could not be evaluated. Further, Sample No. having a porosity on the surface of more than 50%. In No. 10, when the paste was embedded, spitting occurred frequently, and many electrical shorts occurred. Further, in the case of No. 1 in which the thickness of the porous layer was less than 1 μm. In No. 11, transfer failure occurred frequently, and electrical characteristics could not be evaluated. , Again 3
No. 0 thicker than 0 μm. In No. 12, the deformation of the pattern was large, and short-circuit occurred in some parts.

For these comparative examples, the sample N of the present invention was used.
o. Nos. 2 to 5 and 7 to 9 have no initial resistance or poor appearance,
Even after the AST test, there was almost no change in resistance, and the resistance was good.

[0060]

As described in detail above, according to the present invention, even when a dense conductor layer such as a metal foil is transferred to the surface of a prepreg made of a glass woven fabric and a thermosetting resin,
A prepreg capable of manufacturing a highly reliable wiring board in which a wiring pattern is not deformed and a circuit short circuit does not occur can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining the structure of a prepreg of the present invention.

FIG. 2 is a process chart for explaining a prepreg manufacturing method of the present invention.

FIG. 3 is a diagram for explaining a prepreg heat treatment method of the present invention.

FIG. 4 is a process chart showing a method for manufacturing a wiring board according to the present invention.

[Explanation of symbols]

 A Prepreg x Glass woven cloth y Thermosetting resin

Continued on front page F term (reference) 5E343 AA15 AA16 BB67 DD56 DD76 GG14 5E346 AA06 AA12 CC04 CC08 DD12 EE09 FF18 GG22 HH08

Claims (9)

[Claims] A porosity of 10 to 50% containing a thermosetting resin is provided on at least one surface side of a dense layer in which a thermosetting resin is impregnated in a glass woven fabric and has a porosity of 5% or less. A prepreg comprising a porous layer having a thickness of 1 to 30 μm. 2. The prepreg according to claim 1, which is used for forming a wiring circuit layer made of a metal foil by a transfer method. 3. The prepreg according to claim 1, wherein said thermosetting resin is polyphenylene ether. 4. The method according to claim 1, wherein a volume ratio of the glass woven fabric and the thermosetting resin in the whole is in a ratio of 20:80 to 80:20. Prepreg. 5. A step of (a) producing a sheet body in which a thermosetting resin is impregnated in a glass woven fabric; and (b) a rigid plate is laminated on both sides of the sheet body, and a pressure of 200 MPa or more is applied. (C) forming a porous layer containing a thermosetting resin on at least one surface of the densified sheet body while heating and densifying the sheet body at a temperature of 40 to 220 ° C. A method for producing a prepreg, comprising: 6. The method according to claim 1, wherein said porous layer has a thickness of 1 to 5.
The method for producing a prepreg according to claim 5, wherein the prepreg is formed with a thickness of 30 μm. 7. The method for producing a prepreg according to claim 5, wherein said thermosetting resin is polyphenylene ether. 8. A step of forming a via hole at a predetermined position of the prepreg according to claim 1 and filling a conductive paste containing a metal powder in the via hole to form a via hole conductor. Transferring a wiring circuit layer made of a metal foil previously formed on a transfer sheet surface to a prepreg surface on which the via-hole conductor is formed, and heating the prepreg on which the via-hole conductor and the wiring circuit layer are formed by thermosetting. Curing the conductive resin. A method for manufacturing a wiring board, comprising: 9. A via-hole conductor, wherein a via-hole is formed in a predetermined portion of the prepreg according to claim 1, and a conductive paste containing a metal powder is filled in the via-hole to form a via-hole conductor. Forming step, a transfer step of transferring a wiring circuit layer made of a metal foil previously formed on a transfer sheet surface to a prepreg surface on which the via hole conductor is formed, and a plurality of via holes formed by the via hole conductor forming step and the transfer step. A laminating step of laminating and pressing the prepreg, and a step of heating the laminated body to cure the thermosetting resin.