JPH10287832A - Production of insulating varnish and multi-layered printed wiring board using the insulating varnish - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an insulating varnish capable of giving printed wiring broads flat in surfaces and good in circuit processability by stirring whiskers in an organic solvent to dissociate whisker aggregates contained in the whiskers, adding the prepared homogeneous slurry to a resin varnish and subsequently stirring the mixture. SOLUTION: This method for producing an insulating varnish comprises stirring electrically insulating ceramic whiskers having an average diameter of 0.3-3 μm and an average length of 3-50 μm in an organic solvent to dissociate whisker aggregates contained in the whiskers in a dry state, adding the prepared homogeneous slurry to a resin varnish, and subsequently stirring the mixture. Thereby, the objective insulating varnish giving printed wiring boards high in mounting reliability, good in wire bondability and good in dimensional stability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating varnish applied to an adhesive film for a printed wiring board or a multilayer printed wiring board which can meet the demand for thinner and higher density printed wiring boards on which electronic components are mounted. The present invention relates to a manufacturing method and a multilayer printed wiring board using the insulating varnish.

[0002]

2. Description of the Related Art A printed wiring board is usually obtained by laminating a copper foil and a prepreg, and performing circuit processing on a copper-clad laminate obtained by hot pressing. Further, a multilayer printed wiring board was obtained by hot-pressing these printed wiring boards via a prepreg, or by hot-pressing these printed wiring boards and copper foil through a prepreg and integrating them. It is obtained by forming a circuit on the surface of a multilayer copper clad laminate containing an inner layer circuit.

As a prepreg for a printed wiring board, a glass cloth prepreg obtained by impregnating a glass cloth with a resin and drying the resin to make the resin semi-cured has been used. For a multilayer printed wiring board, the prepreg of the glass cloth prepreg has been used. other,
JP-A-6-200216 and JP-A-6-24246
Japanese Patent Application Laid-Open No. 6-19686, which describes a prepreg that does not use a glass cloth and is made of a resin having a film forming ability in a semi-cured state.
An adhesive film with a copper foil having an adhesive film formed on one side of a copper foil, as described in Japanese Patent Publication No. 2 (JP-A) No. 2 (1994), is used. The film-forming ability referred to here means that troubles such as cracking or chipping of the resin hardly occur during the steps of transporting, cutting, and laminating the prepreg, and the interlayer insulating layer is formed in the portion where the inner layer circuit exists at the time of subsequent hot pressing. It means performance that is unlikely to cause troubles such as abnormal thinning, reduction in interlayer insulation resistance and short circuit.

[0004]

In recent years, electronic devices have been reduced in size, weight, performance, and cost, and printed wiring boards have been required to have higher density, thinner, higher reliability, and lower cost. Has been requested. For high density, fine wiring is required, and for that purpose, the surface must have good flatness and good dimensional stability. Further, fine through holes and interstitial via holes (IVH) are required, and good drill workability and laser hole workability are required. In order to improve the flatness of the surface, it is necessary to increase the fluidity of the resin at the time of multilayer lamination molding, and it is desirable to use a thermosetting resin such as an epoxy resin.

[0005] However, epoxy resins exhibit high fluidity due to their low molecular weight before molding, and do not have the property of forming a sheet-like adhesive film. Therefore, in the past, a prepreg in which an insulating resin was impregnated into a reinforcing base material such as glass cloth was prepared in advance, and this was used for the insulating layer. However, it has become difficult to respond to the above requirements with the conventional prepreg. .

At present, in the glass cloth generally used for the prepreg, the gap between the yarns (glass fiber bundles) increases as the thickness decreases. For this reason, the thinner the cloth, the more the curling (the phenomenon that the yarn is bent or the warp and the weft, which should intersect at right angles, intersect at right angles rather than at right angles) is more likely to occur. Due to this bending, abnormal dimensional changes and warpage tend to occur after hot pressing. Further, the thinner the glass cloth is, the larger the gap between the yarns is, the lower the volume fraction of the fibers of the prepreg becomes, and the lower the rigidity of the interlayer insulating layer becomes. For this reason, there is a problem in that the deflection is likely to increase in a component mounting step or the like after processing the circuit in the outer layer.

At present, the thinnest glass cloth generally used is a 30 μm cloth, and the thickness of a prepreg using the cloth is about 40 μm. If the resin content is reduced in order to further reduce the thickness of the prepreg, the ability to fill holes in the unevenness of the inner layer circuit with the resin is reduced, and voids are generated. Further, if the glass cloth is made thinner than this, the strength of the cloth itself is reduced, so that the glass cloth is easily broken in the step of impregnating the glass cloth with a resin, and it becomes difficult to manufacture a prepreg. Furthermore, a multilayer printed wiring board manufactured using a prepreg using these glass cloths is easily misaligned by a glass cloth unevenly distributed during small-diameter drilling, and the drill is easily folded. In addition, due to the presence of glass fibers, laser drilling is poor,
The unevenness of the inner layer circuit easily appears on the surface, and the surface flatness is poor.
Therefore, it is not possible to meet the increasing demand for higher density and thinner multilayer printed wiring boards using the current glass cloth base material prepreg.

On the other hand, an adhesive film which is a prepreg without a glass cloth or an adhesive film with a copper foil can be made thinner, and is excellent in small diameter drill workability, laser hole workability and surface flatness. However, the multilayer printed wiring boards made with these prepregs have extremely low rigidity because the outer insulating layer does not have a glass cloth base material. This low rigidity is extremely remarkable at a high temperature, and is likely to bend in the component mounting process, and the wire bonding property is extremely poor. In addition, there is no glass cloth substrate in the outer insulating layer and the coefficient of thermal expansion is large because the thermal expansion coefficient is large, the reliability of connection with the mounted component is low, and cracks in the solder connection due to the thermal expansion and contraction of heating and cooling And many problems such as easy breakage. Therefore, it is not possible to meet the increasing demand for higher density and thinner multilayer printed wiring boards by using an adhesive film which is a prepreg without a glass cloth or an adhesive film with a copper foil.

Therefore, a substrate such as glass cloth is used as a novel adhesive film for solving the problems of high density, thinness, high reliability, and low cost for a multilayer printed wiring board that cannot be solved by a conventional prepreg. It was found that a sheet-like adhesive film obtained by casting a varnish obtained by dispersing an electrically insulating whisker for maintaining shape in an insulating resin on a carrier base material was effective. However, electrical insulating whiskers have the property of agglomerating in a dry state, and special kneading equipment is required to disperse the electrical insulating whiskers in the insulating resin. However, even if such measures are taken, the aggregates of the electrically insulating whiskers cannot be completely eliminated. By the way, in the multilayer wiring board material, the insulating layer thickness is set to be equal to or greater than the inner layer circuit thickness in order to secure the inner layer circuit filling property.
In order to reduce the overall thickness of the multilayer wiring board, it is desired to reduce the thickness as much as possible as long as insulation can be ensured. Therefore, the thickness of the insulating layer is usually 25 to 100 μm, and at least 25 μm is secured. However, the size (length) of the electrically insulating whisker aggregate exceeds 50 μm,
Some of them exceeded 300 μm. When a sheet-like adhesive film produced using a varnish containing the aggregate of the electrically insulating whisker is applied to the multilayer wiring board, the aggregate of the electrically insulating whisker contacts between the conductors,
Insulation failure similar to CAF (Conductive Anodic Filament) may occur.

An object of the present invention is to provide a method for producing an insulating varnish which is excellent in suppressing the incorporation of aggregates of electrically insulating whiskers into an adhesive film in which electrically insulating whiskers are compounded.

[0011]

According to the method for producing an insulating varnish of the present invention, an electrically insulating whisker exhibiting cohesiveness in a dry state is previously stirred in an organic solvent to form a slurry,
It is characterized in that the slurry is blended in a resin varnish and then stirred.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Slurry) The slurry used in the present invention is obtained by stirring and mixing whiskers in an organic solvent in order to dissociate aggregates present in the electrically insulating ceramic whisker aggregate in a dry state. Here, the organic solvent used in preparing the slurry must be compatible with the resin varnish, and is preferably the same as the varnishing solvent in order to stabilize the insulating varnish. The solids content of this slurry is 20-
It is 80% by weight, preferably 25 to 50% by weight. 2
If the amount is less than 0% by weight, the solvent added to the resin varnish becomes too large, so that the application of the insulating varnish cannot be performed. If the amount exceeds 80% by weight, the effect of dispersing the electrically insulating whisker is lost.

(Whisker) The whisker used in the present invention is an electrically insulating ceramic whisker.
It is preferable that the elastic modulus is 200 GPa or more.
If it is less than 0 GPa, sufficient rigidity cannot be obtained when a multilayer printed wiring board is formed. Examples of whisker types include aluminum borate, wollastonite, potassium titanate, basic magnesium sulfate, silicon nitride, α-
One or more materials selected from alumina can be used. Among them, aluminum borate whiskers are
It has a modulus of elasticity of about 400 GPa, much higher than that of glass, a small coefficient of thermal expansion, and is relatively inexpensive. The printed wiring board manufactured using the prepreg of the present invention using the aluminum borate whisker has higher rigidity at room temperature and high temperature than the conventional printed wiring board using glass cloth, and has excellent wire bonding properties. Low thermal expansion coefficient and excellent dimensional stability. Therefore,
As a material of the whisker used in the present invention, aluminum borate is optimal.

If the average diameter of the whiskers is less than 0.3 μm, it is difficult to mix the whiskers with the resin varnish and the coating workability is reduced. If the average diameter exceeds 3 μm, the surface flatness is adversely affected and the whiskers are microscopically observed. Uniform dispersibility is impaired. Therefore, the average diameter of the whiskers is 0.3
It is preferably in the range of ３3 μm. Further, for the same reason and good coatability (easy to apply smoothly), the average diameter is more preferably in the range of 0.5 to 1 μm. By selecting a whisker having such a diameter, a printed wiring board having more excellent surface flatness than using a prepreg using a conventional glass cloth as a base material can be obtained.

The average length of the whiskers is preferably at least 10 times the average diameter. If the ratio is less than 10 times, the reinforcing effect as a fiber becomes small, and at the same time, it becomes difficult to perform two-dimensional orientation in the resin layer of the whisker described later, so that sufficient rigidity cannot be obtained when the wiring board is used. However, when the whisker is too long, it is difficult to uniformly disperse the whisker in the varnish, and the coatability is reduced. In addition, the probability that a whisker in contact with one conductor circuit comes into contact with another conductor circuit increases, and there is a possibility of causing an inter-circuit short circuit accident due to migration of copper ions that tend to move along the fiber. There's a problem. Therefore, the average length of the whiskers is preferably 50 μm or less. A printed wiring board manufactured using the adhesive film of the present invention using the whiskers having such a length has better migration resistance than a conventional printed wiring board using a prepreg based on a glass cloth.

In order to further increase the rigidity and heat resistance of the printed wiring board, it is effective to use whiskers whose surfaces have been treated with a silane coupling agent. Whiskers surface-treated with a coupling agent are excellent in wettability and bonding with a resin, and can improve rigidity and heat resistance.
As the coupling agent used at this time, known compounds such as silicon-based, titanium-based, aluminum-based, zirconium-based, zirconaluminum-based, chromium-based, boron-based, phosphorus-based, and amino acid-based can be used.

(Resin) The resin used in the present invention is a resin used for a conventional prepreg based on a glass cloth and an adhesive film containing no glass cloth substrate or an adhesive film with a copper foil. Thermosetting resin or the like can be used. The term “resin” as used herein means a resin, a curing agent, a curing accelerator, and, if necessary, a coupling agent or a diluent.

The resin used in conventional prepregs based on glass cloth has no film forming ability by itself, so it is formed as an adhesive layer on one side of a copper foil by coating, and the solvent is heated. When the resin is removed and semi-cured, troubles such as cracking or missing of the resin are likely to occur during the process of transport, cutting, lamination, etc. Conventionally, it has been difficult to use it for an adhesive film with a copper foil because it is abnormally thin and easily causes problems such as a decrease in interlayer insulation resistance and a short circuit. However, in the present invention, whiskers are dispersed in the resin, and the resin is reinforced by the whiskers.
During the processes such as cutting and lamination, troubles such as cracking or chipping of the resin hardly occur, and the occurrence of an abnormal thinning of the interlayer insulating layer during hot pressing due to the presence of whiskers can be prevented.

It is also effective to use a resin conventionally used for an adhesive film or an adhesive film with a copper foil. These resins have a film forming ability even when used alone by containing a high molecular weight component and the like.However, by dispersing whiskers in the resin according to the present invention, the film forming ability is further enhanced and the handleability is improved. In addition, the insulation reliability can be further improved. It is also possible to reduce the amount of the high molecular weight component to be added by the amount of the film forming ability enhanced by the dispersion of the whiskers, thereby improving the heat resistance and adhesiveness of the resin in some cases.

Examples of the type of resin include epoxy resin, bismaleimide triazine resin, polyimide resin,
Phenol resins, melamine resins, silicon resins, unsaturated polyester resins, cyanate ester resins, isocyanate resins, or various modified resins thereof are suitable. Among them, bistriazine resin and epoxy resin are particularly preferable in terms of characteristics of the printed wiring board. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A novolak type epoxy resin, salicylaldehyde novolak type epoxy resin, Bisphenol F novolak type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, aliphatic cyclic epoxy resin and their halides and hydrogenated products And mixtures of the above resins.
Among them, bisphenol A novolak type epoxy resin or salicylaldehyde novolak type epoxy resin is preferable because of its excellent heat resistance.

(Curing agent) As the curing agent for such a resin, those conventionally used can be used. When the resin is an epoxy resin, for example, dicyandiamide, bisphenol A, bisphenol F, polyvinyl phenol, phenol novolak Resins, bisphenol A novolak resins, and halides and hydrides of these phenolic resins can be used. Among them, bisphenol A novolak resin is preferable because of its excellent heat resistance. The ratio of the curing agent to the resin may be a conventionally used ratio, and is preferably in the range of 2 to 100 parts by weight with respect to 100 parts by weight of the resin. Further, in the case of dicyandiamide, 2 to 5 parts by weight, For other curing agents, the range is preferably 30 to 80 parts by weight. If it is less than 2 parts by weight, sufficient curing cannot be obtained,
If the amount exceeds 100 parts by weight, an excessive curing agent may remain, and the electric properties and the like of the cured product may be deteriorated.

(Curing Accelerator) As the curing accelerator, when the resin is an epoxy resin, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt or the like is used. The ratio of the curing accelerator to the resin may be a conventionally used ratio, and is preferably in the range of 0.01 to 20 parts by weight, more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the resin.
A range of 10 parts by weight is more preferred. If the amount is less than 0.01 part by weight, the curing will be remarkably slow, and if it exceeds 20 parts by weight, the curing rate will be so high that the curing reaction cannot be controlled.

(Diluent) The thermosetting resin of the present invention is diluted with a solvent and used as a resin varnish. As such a solvent, acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide and the like can be used. The ratio of the diluent to the resin may be a conventionally used ratio,
The amount is preferably in the range of 1 to 200 parts by weight, and more preferably 3 to 200 parts by weight.
The range of 0 to 100 parts by weight is more preferable. If the amount is less than 1 part by weight, there is no effect as a diluent, and if it exceeds 200 parts by weight, the viscosity of the resin composition is too low, and it is difficult to apply the resin composition to a copper foil or a carrier film.

(Other Ingredients) In the present invention, conventionally known coupling agents, fillers, flame retardants and the like may be appropriately added to the resin, if necessary, in addition to the above-mentioned components. Good.

(Ratio of Resin to Whisker) If the compounding amount of the electrically insulating whisker with respect to the resin is less than 5 parts by weight with respect to 100 parts by weight of the resin solids, the resin is finely crushed at the time of cutting and the resin is scattered. In addition, the handleability is deteriorated, for example, and the sufficient rigidity cannot be obtained when the wiring board is used. On the other hand, the whisker content was 350
If the amount exceeds the weight part, the filling property of the inner layer circuit at the time of hot pressing and the resin filling property between the circuits are impaired, and the whisker composite resin layer after the hot pressing tends to generate voids and fading, and the wiring board There is a risk that the characteristics will be impaired. Therefore, the amount of the whisker is 5 to 100 parts by weight of the resin solid content.
A range of 350 parts by weight is preferred. In addition, it has excellent fillability of the inner layer circuit and resin filling between the circuits, and the manufactured wiring board has the same or higher rigidity as compared to the wiring board manufactured using the prepreg using the conventional glass cloth. Due to the dimensional stability and wire bonding properties, the whisker content is 10% resin solids.
More preferably, the amount is 30 to 230 parts by weight with respect to 0 parts by weight.

(Carrier Film) In the present invention, the carrier film on which the whisker composite resin layer (B-stage state), which is an insulating layer, is formed on one surface thereof is a metal foil such as a copper foil or an aluminum foil, a polyester film, or the like. A polyimide film or a film obtained by treating the surfaces of the metal foil and the film with a release agent is used.

(Orientation of Whisker) Whiskers in the adhesive film composed of the electrically insulating whisker of the present invention and the resin in the B-stage state are in a state close to two-dimensional orientation (whisker is in the axial direction of the adhesive film layer). (A state close to being parallel to the surface to be formed). By orienting the whiskers in this manner, the adhesive film of the present invention can obtain good handleability and, at the same time, high rigidity, good dimensional stability and surface flatness when formed into a wiring board.

(Coating method) In order to orient the whiskers as described above, a whisker having a fiber length in the above-described preferred range is used, and at the same time, when a resin varnish in which whiskers are mixed with a copper foil is coated, a blade is used. A coating that can apply a shearing force in the direction parallel to the copper foil such as a coater, rod coater, knife coater, squeeze coater, reverse roll coater, transfer roll coater, etc., or can apply a compressive force in the direction perpendicular to the copper foil surface. The construction method may be adopted.

The present invention relates to a method for producing an insulating varnish by adding an electrically insulating whisker prepared in a slurry form using an organic solvent to a resin varnish and mixing with stirring. Since no whisker aggregates are included, the insulation reliability of the adhesive film in which the electrically insulating whiskers are compounded can be improved. In addition, since the insulating layer produced using the adhesive film of the present invention is a fine whisker, since the base material has better workability with respect to laser than glass and is a fine whisker, the insulating layer using the conventional glass cloth prepreg is not used. Difficult laser drilling can be done easily. Therefore, a small-diameter interstitial via hole (IVH) having a diameter of 100 μm or less can be easily manufactured, and the circuit of the printed wiring board can be miniaturized, which greatly contributes to higher density and higher performance of electronic devices.

[0030]

【Example】

Example 1 70 parts by weight of (varnish) bisphenol A novolak type epoxy resin (molecular weight: 1200, epoxy equivalent: 206) and bisphenol A novolak resin (molecular weight: 7)
00, hydroxyl equivalent: 118) and a thermosetting resin comprising 0.5 parts by weight of 2-ethyl-4-methylimidazole are charged into a slurry-like aluminum borate whisker, and the aluminum borate whisker is varnished. Stir until homogeneously dispersed throughout. Here, the aluminum borate whisker in a slurry state is prepared by adding 90 parts by weight of aluminum borate whisker having an average diameter of 0.8 μm and an average fiber length of 20 μm to 180 parts by weight of methyl ethyl ketone,
This was used by stirring and mixing for 15 minutes. The insulating varnish obtained as described above was applied to a copper foil of 18 μm thickness and a PET film of 50 μm thickness by a knife coater, respectively, and heated and dried at a temperature of 150 ° C. for 10 minutes to remove the solvent. The resin is semi-cured to produce an adhesive film with a copper foil with an adhesive layer thickness of 50 μm and 100 μm, and an adhesive film with a PET film with an adhesive layer thickness of 50 μm and 100 μm. Peel and remove the PET film,
An adhesive film having a thickness of 50 μm and an adhesive film having a thickness of 100 μm were formed from a whisker and a semi-cured epoxy resin having a whisker volume fraction of 30%. The produced adhesive film with a copper foil was cut cleanly by a cutter knife and a shear without scattering of a resin, etc., and there was no blocking between the adhesive films, and the handleability was good. In addition, the adhesive film produced by coating the PET film has no troubles such as cracking during peeling of the PET film or normal handling, and can be cut into small pieces by the cutter knife and shear without scattering of resin. There was no blocking between the films, and the handling was good.

(Electrolytic corrosion test) Next, an etching resist pattern was formed on the copper foil surface of the glass epoxy double-sided copper-clad laminate having a thickness of 0.8 mm in the shape of an electrode on the inner surface of the electrolytic corrosion test. The foil was removed by etching, and an adhesive film with a copper foil having a thickness of 50 μm was laminated on the upper and lower sides so that the adhesive film was in contact with the pattern serving as the electrode on the inner surface of the electrolytic corrosion test. 175 ° C., 2.
Hot pressing was performed under the conditions of 5 MPa for 60 minutes. An etching resist pattern was formed in a shape corresponding to the outer layer electrode on a portion of the obtained laminated plate corresponding to the position of the electrolytic corrosion test pattern serving as the inner layer electrode, and unnecessary copper foil was removed by etching. A test piece was obtained. 50 between the inner and outer layer electrodes
V under a 85 ° C., 85% RH atmosphere.
As a result of measuring the insulation resistance value after lapse of 000 hours, 10 ⁹
A good value of Ω or more was shown, and it was confirmed that the adhesive film was excellent in electric corrosion resistance.

(Flexural Modulus) The thickness 100
A single-sided roughened copper foil having a thickness of 18 μm is placed on and under the μm adhesive film so that the roughened surface faces the adhesive film,
Hot pressing was performed under the conditions of 175 ° C., 2.5 MPa, and 60 minutes. When the copper foil of the obtained copper-clad laminate was removed by etching and the flexural modulus was measured by three-point bending, it was 20 GPa (no copper foil, average vertical length). (Drilling Accuracy) Also, when the copper-clad laminates were drilled by stacking ten copper-clad laminates with a diameter of 0.3 mm, the deviation between the hole positions of the uppermost plate and the lowermost plate was measured to be 20 μm or less.

(Multilayer Printed Wiring Board) An unnecessary portion of the copper foil of the copper-clad laminate is removed by etching to form a circuit.
The adhesive film of the present invention having a thickness of 50 μm previously prepared was stacked on both surfaces thereof, and a single-sided roughened copper foil having a thickness of 18 μm was further laminated on the outside thereof so that the roughened surface faced the adhesive film. It was hot-pressed under the conditions of 0.5 MPa and 60 minutes to produce a multilayer copper-clad laminate having an inner layer circuit. When the surface roughness of the multilayer copper-clad laminate containing the inner layer circuit was measured by a stylus type surface roughness meter, the measurement location was on a straight line having a length of 25 mm including a portion with and without an inner layer circuit immediately below. In the outer layer table, the 10-point average of the level difference between the portion having the inner layer circuit and the portion not having the inner layer circuit was 3 μm or less, and good surface flatness which did not hinder circuit processing was obtained. Further, a predetermined position of the surface copper foil of the multilayer copper-clad laminate containing the inner layer circuit was removed by etching to form a hole having a diameter of 75 μm, and the hole was formed using an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After performing desmear treatment with manganese acid and performing electroless plating,
An etching pattern was formed by baking and developing, and unnecessary copper was removed by etching to form a circuit. The above-mentioned adhesive film having a thickness of 50 μm is overlaid on both sides of the multilayer printed wiring board, and a single-sided roughened copper foil having a thickness of 18 μm is further overlaid so that the roughened surface faces the adhesive film.
A hot-press molding is performed at 75 ° C., 2.5 MPa, for 60 minutes to produce a multilayer copper-clad laminate having an inner layer circuit, a copper foil at a predetermined position is removed by etching, and a hole having a diameter of 75 μm is formed. After drilling using an impact laser manufactured by Heavy Machinery Co., Ltd., performing desmear treatment with permanganic acid, performing electroless plating, baking and developing the etching pattern, etching unnecessary copper A circuit was formed by removal. The above steps were repeated to produce a 10-layer printed wiring board.

(Test of Multilayer Printed Wiring Board) A part of this multilayer printed wiring board was cut out, and its coefficient of thermal expansion and flexural modulus were measured. The coefficient of thermal expansion was measured by TMA, and the flexural modulus was measured by the bending mode of DMA. As a result, the average coefficient of thermal expansion in the vertical direction was 10 ppm / ° C. (at ordinary temperature). The average flexural modulus is 60 at room temperature.
GPa was 40 GPa at a high temperature (200 ° C.). The surface hardness measured by a Barcol hardness meter is 65 at room temperature,
It was 50 at high temperature (200 ° C.). (Wire bonding property) Further, a bare chip was mounted on a part of the 10-layer printed wiring board, and connected to a surface circuit by wire bonding. The wire bonding conditions are
When the ultrasonic output was 1 W, the ultrasonic output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., the wire bonding was successfully performed. (Thermal Shock Test) Further, an IC chip (TSOP) having a size of 8 mm × 20 mm was connected to this 10-layer printed wiring board as a surface circuit via solder, and the substrate on which the IC chip (TSOP) was mounted was replaced by a −65. 30 minutes at 150 ° C and 30 minutes at 150 ° C
A thermal shock test with one cycle of exposure to the environment for one minute revealed that no defects such as disconnection occurred in the solder connection even after 2,000 cycles.

Further, a continuity test of a circuit including an interstitial via hole inside the substrate was performed, but no trouble such as disconnection occurred.

Example 2 70 parts by weight of salicylaldehyde novolak type epoxy resin (molecular weight: 1000, epoxy equivalent: 180) and bisphenol A novolak resin (molecular weight: 70)
0, hydroxyl equivalent: 118) and 30 parts by weight of N-methylimidazole and 0.5 part by weight of a thermosetting resin,
The slurry was poured into aluminum borate whiskers and stirred until the aluminum borate whiskers were uniformly dispersed in the varnish. Here, the slurry-like aluminum borate whisker has an average diameter of 0.8 μm and an average fiber length of 20 μm.
m of aluminum borate whiskers (90 parts by weight) were added to 180 parts by weight of methyl ethyl ketone, and the resulting mixture was stirred and mixed for 15 minutes. (Adhesive film) The insulating varnish obtained as described above is applied to a copper foil having a thickness of 18 μm and a PET film having a thickness of 50 μm with a knife coater, and is heated and dried at 150 ° C. for 10 minutes to remove the solvent. At the same time, the resin is semi-cured to form an adhesive film with a copper foil having an adhesive layer thickness of 50 μm or 100 μm, and a PET film having an adhesive layer thickness of 50 μm or 100 μm.
An adhesive film with a film is prepared, and the PET film is peeled off from the adhesive film with a PET film. The whisker has a volume fraction of 30% and is composed of an epoxy resin in a semi-cured state.
m was prepared. The produced adhesive film with a copper foil was cut cleanly by a cutter knife and a shear without scattering of a resin, etc., and there was no blocking between the adhesive films, and the handleability was good. Also, PE
Adhesive film made by coating on T film is PET
There was no trouble such as cracking during peeling of the film or during normal handling, and the film could be cut cleanly by a cutter knife and a shear without scattering of the resin.

(Electrolytic corrosion test) Next, an etching resist pattern was formed on the copper foil surface of the glass epoxy double-sided copper-clad laminate having a thickness of 0.8 mm in a shape to be an electrode on the inner surface of the electrolytic corrosion test. Unnecessary portions of the copper foil are removed by etching, and an adhesive film with a copper foil having a thickness of 50 μm of the insulating layer prepared above is laminated on the upper and lower sides so that the adhesive film is in contact with a pattern serving as an electrode on the inner surface of the electrolytic corrosion test. Laminated together, 1
It was hot-pressed under the conditions of 75 ° C., 2.5 MPa and 60 minutes.
On the copper foil surface of the obtained laminate, an etching resist pattern is formed in the shape corresponding to the outer layer electrode on the portion corresponding to the position of the electrolytic corrosion test pattern serving as the inner layer electrode, and the unnecessary portion of the copper foil is etched. It was removed to obtain a test piece for electrolytic corrosion. A voltage of 50 V is applied between the inner layer electrode and the outer layer electrode.
As a result of measuring the insulation resistance after 1000 hours in an atmosphere of 85% RH, a good value of 10 ⁹ Ω or more was shown, and it was confirmed that the adhesive film was excellent in electric corrosion resistance.

(Flexural modulus) Further, the prepared thickness 10
A single-sided roughened copper foil having a thickness of 18 μm was laminated on and under the 0 μm adhesive film so that the roughened surface faced the adhesive film, and was hot-pressed at 175 ° C., 2.5 MPa and 60 minutes. The copper foil of the obtained copper-clad laminate is etched away,
When the flexural modulus was measured by three-point bending, it was 20 GPa (no copper foil, vertical average). (Drilling Accuracy) When the copper-clad laminates were drilled by stacking ten copper-clad laminates with a diameter of 0.3 mm, the amount of displacement between the uppermost plate and the lowermost plate was measured to be 20 μm or less. (Multilayer printed wiring board) An unnecessary portion of the copper foil of the copper-clad laminate is removed by etching to form a circuit, and a 50 μm-thick adhesive film previously prepared is laminated on both surfaces thereof, and a thickness is further formed on the outside thereof. Laminated 18μm single-sided roughened copper foil with the roughened surface facing the adhesive film, 170 ℃, 2.5MP
a) Hot-press molding was performed under the conditions of 60 minutes to produce a multilayer copper-clad laminate containing an inner layer circuit. The surface roughness of the multilayer copper-clad laminate containing the inner layer circuit was measured with a stylus type surface roughness meter. As a result, the measurement location was on a straight line with a length of 25 mm including the part with and without the inner layer circuit immediately below. On the surface of the outer layer, the average of 10 points of the level difference between the portion having the inner layer circuit and the portion not having the inner layer circuit was 3 μm or less, and the surface flatness was satisfactory without any trouble in circuit processing.

Further, a predetermined position of the surface copper foil of the multilayer copper-clad laminate containing the inner layer circuit was removed by etching to have a diameter of 75 μm.
Drilled holes using an impact laser manufactured by Sumitomo Heavy Industries, Ltd., performed desmear treatment with permanganic acid, performed electroless plating, and then baked and developed the etching resist pattern. The circuit was formed by etching away unnecessary portions of copper. On both sides of this multilayer printed wiring board, the adhesive film having a thickness of 50 μm previously prepared is laminated, and further on the outside thereof, a 18 μm-thick one-side roughened copper foil is laminated so that the roughened surface faces the adhesive film, It is hot-pressed under the conditions of 175 ° C., 2.5 MPa and 60 minutes to produce a multilayer copper-clad laminate with an inner layer circuit, and the copper foil at a predetermined position is removed by etching.
Drill a hole with a diameter of μm, drill the hole with an impact laser manufactured by Sumitomo Heavy Industries, Ltd., perform desmear treatment with permanganic acid, perform electroless plating, and then bake and develop the etching resist pattern. The circuit was formed by etching away unnecessary portions of the copper foil. The above steps were repeated to produce a 10-layer printed wiring board.

(Test of Multilayer Printed Wiring Board) A part of the multilayer printed wiring board was cut out, and its coefficient of thermal expansion and flexural modulus were measured. The coefficient of thermal expansion was measured by TMA, and the flexural modulus was measured by a bending mode of DMA. The average coefficient of thermal expansion in the vertical direction is 10 ppm / ° C. (at room temperature), and the average bending elastic modulus in the vertical direction is 60 G at room temperature.
Pa and 50 GPa at high temperature (200 ° C.). The surface hardness measured by a Barcol hardness meter is 65 at room temperature,
It was 55 at high temperature (200 ° C.). (Wire bonding property) Further, a bare chip was mounted on a part of the 10-layer printed wiring board, and connected to a surface circuit by wire bonding. The wire bonding conditions are
When the ultrasonic output was 1 W, the ultrasonic output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., the wire bonding was successfully performed. (Thermal shock test) Also, an IC chip (TSOP) having a size of 8 mm × 20 mm was connected to the surface circuit via solder on the 10-layer printed wiring board, and the substrate on which the IC chip (TSOP) was mounted was −65 ° C. As a result of a thermal shock test in which exposure to an environment of 30 minutes and 150 ° C. for 30 minutes was performed in one cycle, no failure such as disconnection occurred in the solder connection even after 2,000 cycles. A continuity test was performed on a circuit including an interstitial via hole inside the substrate, but no trouble such as disconnection occurred.

COMPARATIVE EXAMPLE 1 70 parts by weight of (varnish) bisphenol A novolak type epoxy resin (molecular weight: 1200, epoxy equivalent: 206) and bisphenol A novolak resin (molecular weight: 7)
00, hydroxyl equivalent: 118), 30 parts by weight of 2-ethyl-4-methylimidazole, 0.5 part by weight of methyl ethyl ketone, and 70 parts by weight of methyl ethyl ketone. Aluminum borate whiskers having a length of 20 μm are mixed with 90 parts by weight of resin solid content of 90 parts by weight.
(Weight) and stirred until the aluminum borate whiskers were uniformly dispersed in the varnish. (Adhesive film) This insulating varnish was applied to a copper foil of 18 μm thickness and a PET film of 50 μm thickness by a knife coater, and was heated and dried at a temperature of 150 ° C. for 10 minutes to remove the solvent and to remove the resin. Cured to produce an adhesive film with a copper foil with an adhesive layer thickness of 50 μm and 100 μm, and an adhesive film with a PET film with an adhesive layer thickness of 50 μm and 100 μm. Peel the PET film from the adhesive film with a PET film Removal was performed to produce an adhesive film having a whisker volume fraction of 30% and an epoxy resin in a semi-cured state with whiskers and having a thickness of 50 μm and 100 μm. The produced adhesive film with copper foil is
With a cutter knife and a shear, the resin film could be cut cleanly without scattering of resin and the like, and there was no blocking between the adhesive films, and the handleability was good. In addition, the adhesive film produced by coating the PET film has no troubles such as cracking during peeling of the PET film or normal handling, and can be cut cleanly with a cutter knife and shear without scattering of resin. There was no blocking between them, and the handling was good.

(Electrolytic corrosion test) Next, unnecessary portions of the copper foil of the glass epoxy double-sided copper clad laminate having a thickness of 0.8 mm were removed by etching to form a pattern to be an electrode on the inner surface of the electrolytic corrosion test. The thickness of the insulating layer prepared above and below is 50
μm adhesive film is laminated so that the adhesive film is in contact with the electrode pattern on the inner surface of the electrolytic corrosion test, and a 18 μm-thick one-side roughened copper foil is further laminated so that the roughening faces the adhesive film. , 175 ° C, 2.5MPa, 60
For 1 minute. Unnecessary portions of the copper foil of the obtained laminated board are removed by etching, and a pattern serving as an outer layer electrode is formed in a portion corresponding to the position of the inner layer electrode serving as an electrolytic corrosion test pattern, thereby obtaining an electrolytic corrosion test piece. Was. A voltage of 50 V is applied between the electrodes of the inner layer and the outer layer, and 85 ° C., 85% RH
As a result, the insulation resistance after 250 hours was less than 10 ⁹ Ω, indicating that the adhesive film was inferior in electric corrosion resistance. (Bending elastic modulus) A single-sided roughened copper foil having a thickness of 18 μm is laminated on and under the prepared adhesive film having a thickness of 100 μm so that the roughened surface faces the adhesive film.
a, Hot-press molding was performed for 60 minutes. When the copper foil of the obtained copper-clad laminate was etched away and the flexural modulus was measured by three-point bending, it was 20 GPa (no copper foil, vertical average)
Met. (Drilling Accuracy) When the copper-clad laminates were drilled by stacking ten copper-clad laminates with a diameter of 0.3 mm, the amount of displacement between the uppermost plate and the lowermost plate was measured to be 20 μm or less. (Multilayer Printed Wiring Board) This copper-clad laminate is subjected to circuit processing, and the adhesive film of the present invention having a thickness of 50 μm previously prepared on both surfaces thereof, and a 18 μm-thick roughened copper foil having a thickness of 18 μm on the outside thereof, The laminate was laminated so that the roughened surface faced the adhesive film, and hot-pressed under the conditions of 175 ° C., 2.5 MPa, and 60 minutes to produce a multilayer copper-clad laminate with an inner circuit. As a result of measuring the surface roughness of the multilayer copper-clad laminate containing the inner layer circuit with a stylus type surface roughness meter, the measurement location was on a straight line having a length of 25 mm including a portion with and without an inner layer circuit immediately below. On the surface of the outer layer, the average of 10 points of the level difference between the portion having the inner layer circuit and the portion not having the inner layer circuit was 3 μm or less, and the surface flatness was satisfactory without any trouble in circuit processing. Further, a predetermined position of the surface copper foil of the multilayer copper-clad laminate containing the inner layer circuit was removed by etching to form a hole having a diameter of 75 μm, and the hole was formed using an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After performing desmear treatment with manganese acid and performing electroless plating,
The circuit was formed by baking and developing the etching resist pattern and etching away unnecessary copper. On both sides of this multilayer printed wiring board, the adhesive film having a thickness of 50 μm previously prepared is laminated, and further on the outside thereof, a 18 μm-thick one-side roughened copper foil is laminated so that the roughened surface faces the adhesive film, Hot-press forming at 170 ° C., 2.5 MPa, 60 minutes to produce a multilayer copper-clad laminate with an inner layer circuit, etching and removing a predetermined position of the copper foil to form a hole having a diameter of 75 μm. Drill holes using an impact laser manufactured by Sumitomo Heavy Industries, Ltd., perform desmear treatment with permanganic acid, perform electroless plating, bake and develop an etching resist pattern, and remove unnecessary copper by etching. Thus, a circuit was formed. Repeat the above steps to get 1
A zero-layer printed wiring board was produced.

(Test of Multilayer Printed Wiring Board) A part of this multilayer printed wiring board was cut out, and its coefficient of thermal expansion and flexural modulus were measured. The coefficient of thermal expansion was measured by TMA, and the flexural modulus was measured by a bending mode of DMA. The average coefficient of thermal expansion in the vertical direction is 10 ppm / ° C. (at room temperature), and the average bending elastic modulus in the vertical direction is 60 G at room temperature.
Pa and 40 GPa at high temperature (200 ° C.). The surface hardness measured by a Barcol hardness meter is 65 at room temperature,
It was 50 at high temperature (200 ° C.). (Wire bonding property) Further, a bare chip was mounted on a part of the 10-layer printed wiring board, and connected to a surface circuit by wire bonding. The wire bonding conditions are
When the ultrasonic output was 1 W, the ultrasonic output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., the wire bonding was successfully performed. (Thermal shock test) Further, an IC chip (TSOP) having a size of 8 mm × 20 mm was connected to the surface circuit via solder on the 10-layer printed wiring board, and the substrate on which the IC chip (TSOP) was mounted was subjected to −65 ° C. And a 30-minute exposure at 150 ° C. for 1 cycle, and no failure such as disconnection occurred in the solder connection after 2000 cycles. A continuity test was performed on a circuit including an interstitial via hole inside the substrate, but no trouble such as disconnection occurred.

Comparative Example 2 (prepreg) bisphenol A novolak type epoxy resin (molecular weight: 1200, epoxy equivalent: 206) was mixed with 7
0 parts by weight, 30 parts by weight of bisphenol A novolak resin (molecular weight: 700, hydroxyl equivalent: 118), and 2 parts by weight.
0.5 parts by weight of -ethyl-4-methylimidazole;
A thermosetting resin consisting of 70 parts by weight of methyl ethyl ketone is impregnated into glass cloth having a thickness of 50 μm and 100 μm.
It is coated and heated and dried at a temperature of 150 ° C. for 10 minutes to remove the solvent and semi-cured the resin, and is made of a glass cloth and a semi-cured epoxy resin having a thickness of 70 μm.
And an epoxy prepreg having a thickness of 120 μm. The resin was scattered in the prepared prepreg when cutting with a cutter knife and a shear.

(Electrolytic corrosion test) Next, an etching resist pattern was formed on a copper foil of a glass epoxy double-sided copper clad laminate having a thickness of 0.8 mm in a shape to be an electrode on the inner surface of the electrolytic corrosion test. The copper foil is removed by etching, and the epoxy prepreg having an insulating layer thickness of 70 μm and the one-side roughened copper foil having a thickness of 18 μm prepared above and below the epoxy prepreg are used as an electrode on the inner surface of the electrolytic corrosion test. And hot-pressed under the conditions of 175 ° C., 2.5 MPa, and 60 minutes. Unnecessary portions of the copper foil of the obtained laminate were removed by etching, and a pattern serving as an outer layer electrode was formed in a portion corresponding to the position of the electrolytic corrosion test pattern serving as an inner layer electrode, to obtain an electrolytic corrosion test piece. . The inner layer and a voltage of 50V was applied between the outer electrodes, 85 ° C., a result of measuring the insulation resistance value after 1000 hours passed in an atmosphere of RH 85%, showed good values of more than 10 ⁹ Omega, adhesive It was confirmed that the film had excellent corrosion resistance. (Bending elastic modulus) A single-sided roughened copper foil having a thickness of 18 μm was laminated above and below the prepared epoxy prepreg having a thickness of 120 μm so that the roughened surface faced the prepreg, and then heated at 175 ° C.
Hot pressing was performed under the conditions of 2.5 MPa and 60 minutes. When the copper foil of the obtained copper-clad laminate was removed by etching, and the flexural modulus was measured by three-point bending, it was 8 GPa (no copper foil, average vertical length). (Drilling Accuracy) Further, when the copper-clad laminates were drilled by stacking ten copper-clad laminates with a diameter of 0.3 mm, the deviation between the hole positions of the uppermost plate and the lowermost plate was measured and found to be 50 μm or more.

(Multilayer Printed Wiring Board) This copper-clad laminate is subjected to circuit processing to produce an inner layer circuit board, and the 70 μm thick glass epoxy prepreg previously prepared is provided on both sides thereof.
Further on the outside, a single-sided roughened copper foil having a thickness of 18 μm was laminated so that the roughened surface faced the prepreg, and hot-pressed to produce a multilayer copper-clad laminate having an inner circuit. As a result of measuring the surface roughness of the multilayer copper-clad laminate containing the inner layer circuit with a stylus type surface roughness meter, the measurement location was on a straight line having a length of 25 mm including a portion with and without an inner layer circuit immediately below. On the outer layer surface of
The 10-point average of the step between the part with and without the inner layer circuit is:
It was 8 μm or more. Further, a predetermined position of the surface copper foil of the multilayer copper clad laminate containing the inner layer circuit was removed by etching to obtain a diameter of 7 mm.
A hole of 5 μm was made, and an attempt was made to make a hole using an impact laser manufactured by Sumitomo Heavy Industries, Ltd., but the glass portion could not be removed.

Comparative Example 3 (Adhesive Film) 50 parts by weight of a high molecular weight epoxy polymer having a weight average molecular weight of 50,000 and diluent
N, N-dimethylacetamide was used so that the high molecular weight epoxy polymer had a solid content of 30% by weight, 50 parts by weight of a bisphenol A type epoxy resin (molecular weight: 343, epoxy equivalent: 175), and a high molecular weight epoxy resin 0.2 equivalent of a phenolic resin-masked diisocyanate as a cross-linking agent and 2-ethyl-4- as a curing agent
A thermosetting resin consisting of 0.5 parts by weight of methylimidazole is coated on a 18 μm-thick copper foil and a 50 μm-thick PET film with a knife coater, and heated and dried at 150 ° C. for 10 minutes to remove the solvent. At the same time, the resin is semi-cured to produce an adhesive film with a copper foil having an adhesive layer thickness of 50 μm and an adhesive film with a PET film having an adhesive layer thickness of 50 μm. Was peeled and removed to prepare an adhesive film having a whisker volume fraction of 30% and an epoxy resin in a semi-cured state with a whisker and a thickness of 50 μm. The produced adhesive film was free of troubles such as cracking during peeling of the PET film or normal handling, and could be cut cleanly without scattering of resin by a cutter knife and shear, but blocking between the adhesive films occurred. The handling was bad.

(Electrolytic corrosion test) Next, a pattern to be an electrode of the inner layer surface of the electrolytic corrosion test was formed on the copper foil surface of the glass epoxy double-sided copper clad laminate having a thickness of 0.8 mm, and unnecessary copper foil was etched. The adhesive film with a copper foil having a thickness of 50 μm and having an adhesive layer prepared above was overlaid and laminated so that the adhesive film was in contact with a pattern serving as an electrode on the inner surface of the electrolytic corrosion test. , 2.5 MPa and 60 minutes. Unnecessary portions of the copper foil of the obtained laminate were removed by etching, and a pattern serving as an outer layer electrode was formed in a portion corresponding to the position of the electrolytic corrosion test pattern serving as an inner layer electrode, to obtain an electrolytic corrosion test piece. . A voltage of 50 V was applied between the inner layer electrode and the outer layer electrode, and the insulation resistance was measured after 1000 hours in an atmosphere of 85 ° C. and 85% RH.
It showed a good value of ⁰⁹ Ω or more, and it was confirmed that the adhesive film was excellent in electric corrosion resistance.

(Multilayer Printed Wiring Board) The adhesive film having a thickness of 50 μm previously prepared was laminated on both sides of the inner circuit board prepared in Comparative Example 1, and a 18 μm-thick roughened copper foil was further provided on the outside thereof. The laminate was laminated so that the roughened surface faced the adhesive film, and was hot-pressed under the conditions of 175 ° C., 2.5 MPa, and 60 minutes to produce a multilayer copper-clad laminate with an inner circuit. As a result of measuring the surface roughness of the multilayer copper-clad laminate containing the inner layer circuit with a stylus type surface roughness meter, the measurement location was on a straight line having a length of 25 mm including a portion with and without an inner layer circuit immediately below. Of the step between the part with and without the inner layer circuit on the outer layer surface of
The point average was 3 μm or less, and good surface flatness that did not hinder circuit processing was obtained. Further, a predetermined position of the surface copper foil of the multilayer copper-clad laminate containing the inner layer circuit was removed by etching to form a hole having a diameter of 75 μm, and the hole was formed by Sumitomo Heavy Industries, Ltd.
After drilling using an impact laser manufactured, performing desmear treatment with permanganic acid, performing electroless plating, baking and developing an etching resist pattern, etching away unnecessary copper, and removing the circuit Was formed. On both sides of this multilayer printed wiring board, the adhesive film having a thickness of 50 μm previously prepared is laminated, and further on the outside thereof, a 18 μm-thick one-side roughened copper foil is laminated so that the roughened surface faces the adhesive film, 175 ° C, 2.5MPa, 6
It is hot-pressed under the condition of 0 minutes to prepare a multilayer copper-clad laminate containing an inner layer circuit, a predetermined position of the copper foil is removed by etching, a hole having a diameter of 75 μm is formed, and the hole is formed in the hole by Sumitomo Heavy Industries, Ltd.
Drilling was performed using an impact laser manufactured, desmearing with permanganic acid was performed, electroless plating was performed, an etching resist pattern was formed by baking and development, and unnecessary copper was removed by etching to form a circuit. . The above steps were repeated to produce a 10-layer printed wiring board.

(Test of Multilayer Printed Wiring Board) A part of this multilayer printed wiring board was cut out, and its coefficient of thermal expansion and flexural modulus were measured. The coefficient of thermal expansion was measured by TMA, and the flexural modulus was measured by a bending mode of DMA. The average coefficient of thermal expansion in the vertical direction is 30 ppm / ° C. (at room temperature), and the average bending elastic modulus in the vertical direction is 20 G at room temperature.
Pa and 10 GPa at a high temperature (200 ° C.). The surface hardness measured by a Barcol hardness tester was 30 at room temperature,
It was 10 at high temperature (200 ° C.). (Wire bonding property) Further, a bare chip was mounted on a part of the 10-layer printed wiring board, and connected to a surface circuit by wire bonding. The wire bonding conditions are
The ultrasonic output was 1 W, the ultrasonic output time was 50 μs, and the bond load was 100 g. Wire bonding temperature 10
Even when the temperature was lowered to 0 ° C., peeling of the wire occurred. (Thermal shock test) Also, an IC chip (TSOP) having a size of 8 mm × 20 mm was connected to the surface circuit via solder on this 10-layer printed wiring board, and this IC chip (TSOP)
Is mounted at -65 ° C for 30 minutes and 150 ° C for 30 minutes.
As a result of a thermal shock test in which exposure to the environment for one minute was performed as one cycle, a disconnection defect occurred in the solder connection part after about 100 cycles. Further, a continuity test of a circuit including an interstitial via hole inside the substrate revealed a broken portion.

[0051]

According to the method for producing an insulating varnish of the present invention,
Mixing of the aggregate of the electrically insulating whiskers into the adhesive film in which the electrically insulating whiskers are combined can be suppressed at the stage of the insulating varnish, and the insulation reliability of the adhesive film can be increased. Adhesive film obtained using the insulating varnish produced according to the present invention,
Epoxy resin could be formed into a sheet by adding an electrically insulating whisker.Printed wiring boards using this epoxy resin had a flat surface, good circuit workability, and high rigidity, resulting in high mounting reliability. In addition, since the surface hardness is high, the wire bonding property is good, and the dimensional stability is good because the coefficient of thermal expansion is small. Therefore, it greatly contributes to high density, thinner, higher reliability, and lower cost of the multilayer printed wiring board.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08L 63/00 C08L 63/00 C (72) Inventor Yasushi Yashiro 1500 Ogawa Oji, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Shimodate Within the research institute (72) Inventor Atsuyuki Takahashi 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Kasei Kogyo Co., Ltd. 72) Inventor Shigeharu Ariya 1500, Oji, Shimodate, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd., Shimodate R & D Laboratories Naoyuki Urasaki 1500 Ogawa Oaza, Shimodate City, Ibaraki Prefecture Inside Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inventor Fujimoto Daisuke 1500 Ogawa, Shimodate, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd.

Claims (4)

[Claims] 1. A slurry in which aggregates present in a whisker aggregate in a dry state are dissociated by stirring a whisker in an organic solvent, and the slurry is added to a resin varnish and stirred. A method for producing an insulating varnish, comprising: 2. An electrically insulating whisker comprising a ceramic whisker having an average diameter of 0.3 to 3 whiskers.
The method for producing an insulating varnish according to claim 1, wherein a material having an average length in a range of 3 to 50 µm is used. 3. An insulated varnish obtained by adding a slurry to a resin varnish and then stirring and mixing the resulting mixture is further kneaded with a bead mill so that an average whisker length is in a range of 3 to 30 μm. The method for producing an insulating varnish according to claim 1 or 2, wherein: 4. The insulating varnish according to claim 1, wherein
After laminating an adhesive film obtained by applying a copper foil or a carrier film to a wiring board on which an inner layer circuit is formed, a circuit on an outer layer surface is formed, and the circuit and the inner layer circuit are electrically connected. Multilayer printed wiring board.