JPH10150276A - Insulating material for wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the high density, thinning material, high reliability, and low cost on a multiple layer printed-wiring board by specifying the length of a short fiber type filler not to exceed a specific times of the thickness of the wiring board. SOLUTION: A carrier base material is flowed with varnish comprising insulating resin 2 scattered with a short fiber type filler 1 for the shape holding so as to manufacture a sheetlike insulating material. At this time, short fiber type filler 1 is crushed down in its length not exceeding 35μm and the thickness 32μm of the insulating layer of the wiring board not exceeding about 1.1 times thereof. Through these procedures, the insulation reliability of the insulating material for wiring board can be improved. Besides, owing to the feasibility of thinning material and easy handling, the printed-substrate using the material can improve the circuit workability due to smooth surface thereof. Furthermore, owing to the high rigidity, the package reliability can be improved also owing to the high surface hardness, the wirebonding property can be improved and owing to the small thermal expansion coefficient, the dimensional stability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating material for a wiring board.

[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. In addition, the multilayer printed wiring board is usually obtained by hot-pressing the printed wiring boards via a prepreg, or laminating and integrating the printed wiring boards and the copper foil by hot-pressing via a prepreg. It is manufactured by forming a circuit on the surface of a multilayer copper clad laminate containing an inner layer circuit.

As a prepreg used for such a printed wiring board or a multilayer printed wiring board, a prepreg in which a glass cloth is impregnated with a resin, heated and dried, and the resin is semi-cured is generally used. For the production of a multilayer printed wiring board, in addition to the above-described prepreg, JP-A-6-200216 and JP-A-6-242465.
Japanese Patent Application Laid-Open Publication No.
An adhesive film with a copper foil formed by forming an adhesive film on one side of a copper foil as disclosed in 196,862 may be used. In addition, the film-forming ability referred to herein means a property that hardly causes cracking or chipping of the resin in the steps of transporting, cutting, laminating, etc. of the prepreg, and by having this property, during subsequent hot pressing. ,
This has the effect that the interlayer insulating layer becomes abnormally thin at the location of the inner layer circuit, the interlayer insulation resistance is reduced, and the short circuit between the layers is less likely to occur.

[0004]

In recent years, electronic devices have been reduced in size, weight, performance, and cost, and printed wiring boards and multilayer printed wiring boards have been increased in density, thickness, and reliability. Therefore, cost reduction is required. In order to achieve such high density, fine wiring is required, and for that purpose, the surface must have good flatness and good dimensional stability, and furthermore, fine through holes must be formed. And an interstitial via hole (hereinafter, referred to as IVH) are required, and it is also required that drill workability and laser hole workability be good.

[0005] In order to improve the flatness of the surface, it is necessary to increase the fluidity of the resin during the multilayer lamination molding, and it is preferable to use a thermosetting resin such as an epoxy resin. This epoxy resin shows high fluidity if the molecular weight is low at the stage before molding, but it is difficult to form a sheet-like insulating material using only the resin because it does not have a film forming ability, and conventionally, , Made as a semi-cured prepreg impregnated with a reinforcing substrate such as glass cloth,
This has been used for the insulating layer.

However, it is difficult to reduce the thickness of a printed wiring board or a multilayer printed wiring board using this epoxy resin. This is because, as the thickness of a glass cloth generally used for prepreg decreases, the gap between the yarns (glass fiber bundles) increases as the thickness of the cloth decreases. The warp yarns and the weft yarns, which should intersect at right angles, do not intersect at right angles but intersect at right angles.), Which causes abnormal dimensional changes and warpage after hot pressing. This is because there is a problem that the volume fraction of the cloth in the prepreg decreases, the rigidity of the interlayer insulating layer decreases, and the deflection tends to increase after processing the circuit of the outer layer.

For example, among the generally used glass cloths, the thinnest is a cloth of 30 μm, and the thickness of a prepreg using this is about 40 μm.
Therefore, it is difficult to reduce the thickness of the prepreg. This is because, when the resin content is reduced, the filling property of the resin to the unevenness of the inner layer circuit is reduced by the resin and voids are generated, and the unevenness of the inner layer circuit easily appears on the surface, and there is a problem that the surface flatness is poor, When the glass cloth is made thinner, the strength of the cloth itself decreases, and in the step of impregnating the glass cloth with a resin, the glass cloth is easily broken, and there is a problem that the production of the prepreg becomes difficult. Further, when a multilayer printed wiring board is manufactured using such a thinned prepreg, there is a problem that when drilling with a small-diameter drill, the core is easily misaligned due to unevenly distributed glass cloth and the drill is easily folded. In addition, when laser drilling is performed instead of drilling, due to the presence of glass fiber,
There is a problem in that irregular reflection of laser light occurs and drilling properties are low. Therefore, the prepreg using the current glass cloth cannot meet the increasing demand for higher density and thinner multilayer printed wiring boards.

Therefore, if an adhesive film which is a prepreg without using a glass cloth or an adhesive film with a copper foil can be used, the thickness can be reduced, and small-diameter drilling property, laser hole processing property and surface flatness are excellent. The multilayer printed wiring board manufactured by using the prepreg has problems that the rigidity is extremely low because the outer insulating layer does not have glass cloth, the deflection is easily generated after processing the outer layer circuit, and the wire bonding property is extremely low. In addition, since there is no glass cloth in the outer insulating layer, the coefficient of thermal expansion is large, the difference in thermal expansion with the mounted component is large, and cracks and breaks are likely to occur in the solder connection portion due to thermal expansion and contraction of heating and cooling. Has low connection reliability. Therefore,
Even if an adhesive film that is a prepreg that does not use a current glass cloth or an adhesive film with a copper foil is used, it cannot meet the increasing demand for higher density and thinner multilayer printed wiring boards.

An object of the present invention is to provide an insulating material for a wiring board having high rigidity and excellent thickness reduction.

[0010]

The insulating material for a wiring board according to the present invention is, as schematically shown in FIG. 1, an insulating material for a wiring board comprising a short fiber filler and a resin. The length of the short fiber filler is 1.1 times or less the thickness of the interlayer insulating layer of the wiring board when the wiring board is manufactured using the wiring board insulating material as an interlayer insulating material. I do.

The present inventors have proposed glass cloth as a new insulating material for solving the problems of high density, thinness, high reliability, and low cost in a multilayer printed wiring board that cannot be solved by a conventional prepreg. Not including, it has been found that a sheet-like insulating material obtained by casting a varnish obtained by dispersing a filler in the form of short fibers for maintaining shape in an insulating resin on a carrier substrate is effective. . For example, an electrically insulating whisker can be used as the short fiber filler.

The multilayer printed wiring board has a diameter of 0.3 to
When a sheet-shaped insulating material having a distribution of 3.0 μm and a length of 3 to 60 μm and having an electrically insulating whisker as a filler is used, for example, a whisker having a length of 50 μm is made of resin at the time of hot pressing. Due to the influence of the flow and the like, the insulating layer may be oriented in a state of standing in the thickness direction, and as shown in FIG. 2, whiskers are sandwiched between the conductors of the surface layer and the inner layer. At this time, since the whiskers are insulators, the insulation between the layers is maintained in the short term, but after several years of energization, the original reliability of the insulating resin material cannot be maintained and the whiskers are oriented in the thickness direction. CAF (Conductive Ano) between conductors between
dic Filament), a reliability evaluation test revealed that there was a problem of causing insulation failure.

The present inventors have conducted intensive studies on the relationship between the distribution of whisker lengths and the deterioration of insulation properties by a reliability test. As a result, they found that insulation reliability depends on the whisker lengths. Reached. That is, as a result of measuring the whisker length of an aluminum borate whisker having a nominal length of 30 μm as a sample, the distribution of the whisker length was 3 μm.
６０60 μm, and dozens of 10,000 whiskers are 40
μm or more. Since it is generally known that a material having a larger particle size is easily pulverized by pulverization by mechanical operation, the aluminum borate whisker is used by using a pulverizer such as a rolling ball mill, a planetary ball mill, and a bead mill. The length of was adjusted. The whiskers thus crushed are dispersed in an insulating resin to form a varnish, and formed into a 50 μm thick sheet by a knife coater.
Further, the inner layer circuit board having a conductor thickness of 18 μm is hot-pressed, and the minimum thickness of the insulating layer is 32 μm (= 50 μm-18 μm).
m), and as a result of evaluating the insulation reliability thereof, the maximum whisker length was set to about 35 μm.
m, that is, the thickness of the insulating layer is 32 μm.
It has been found that the insulation reliability is improved when the value of m is about 1.1 times or less. The fact that the whiskers are completely vertically oriented between the conductor layers means that the whiskers are stochastically low and are often slightly obliquely oriented, and that even if the maximum length is 35 μm, the length exceeds 32 μm. Since it is very small, it is considered that the probability that the whisker contacts the conductive layer is very small. Needless to say, it is more preferable that the thickness be less than the thickness of the insulating layer for safety. Therefore, when the conductor thickness of the inner layer is 35 μm, a sheet-like insulating material having a resin layer thickness of 70 μm is often used. In this case, the minimum interlayer insulating layer thickness of the wiring board is 70 μm. −35 = 35 μm, and the whisker length in this case needs to be 39 μm or less, which is about 1.1 times 35 μm, and more preferably less than 35 μm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Whisker) The whisker used in the present invention is an electrically insulating ceramic whisker having an elastic modulus of 20.
It is preferably 0 GPa or more, and if it is less than 200 GPa, sufficient rigidity cannot be obtained when a multilayer printed wiring board is formed.

Examples of whiskers include aluminum borate, wollastonite, potassium titanate,
One or more selected from basic magnesium sulfate, silicon nitride, and α-alumina can be used. Among them, aluminum borate whiskers have an elastic modulus of about 4
It is much higher than glass of 00 GPa, has a lower dielectric constant than glass, has a small coefficient of thermal expansion, and is relatively inexpensive. The printed wiring board manufactured using the prepreg of the present invention using the ammonium 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. Excellent electrical signal transmission characteristics, low thermal expansion coefficient, and excellent dimensional stability. Therefore, as the 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, mixing with the resin varnish becomes difficult and the coatability decreases. If the average diameter exceeds 3 μm, the flatness of the surface is adversely affected and the whiskers are microscopically observed. The average diameter of the whiskers is preferably in the range of 0.3 μm to 3 μm, since such uniformity is impaired. Further, the range of 0.5 μm to 1 μm is most preferable. By selecting a whisker having such a diameter, a printed wiring board having better surface flatness can be obtained than using a prepreg using a conventional glass cloth as a base material.

The average length of the whisker is preferably at least 10 times the average diameter, and if it is less than 10 times, the reinforcing effect as a fiber becomes small and at the same time, the whisker in the resin layer described later However, it is difficult to obtain sufficient rigidity when it is used as a wiring board.
If the whiskers are too long, uniform dispersion in the varnish becomes difficult, the coatability is reduced, and the above-mentioned problem, that is, a short circuit between circuits due to migration of copper ions which tend to move along the fiber is caused. Because of the possibility, the thickness must be 1.1 times or less the thickness of the insulating layer of the present invention.

In order to further increase the rigidity and heat resistance of the printed wiring board, it is effective to use whiskers surface-treated with a silane coupling agent. The whisker that has been subjected to the surface treatment of the coupling agent has excellent wettability and bonding property with the 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.

(Adjustment of whisker length) When commercially available whiskers are used, it is easy and convenient to mechanically pulverize them by various mills such as a ball mill and a bead mill as shown in Examples of the present specification. It is. This is because it is generally known that whiskers having a long fiber length are easily crushed by such mechanical crushing, and are suitable for shortening the vicinity of the maximum length. Although it is more difficult than this, it is also possible to control the whisker crystal growth to obtain a whisker of a desired length, or to select and use a whisker of a desired length by a classification operation.

(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 not containing a glass cloth substrate or an adhesive film with a copper foil. Any thermosetting resin can be used. The term “resin” as used herein means a resin containing a resin, a curing agent, a curing accelerator, a coupling agent (if necessary), and a diluent (if necessary).
The resin used for the prepreg based on the conventional glass cloth has no ability to form a film by itself, so it is formed as an adhesive layer by coating on one side of a copper foil,
When the solvent is removed by heating and the resin is semi-cured, troubles such as cracking or missing of the resin are likely to occur during the process of transporting, cutting, laminating, etc. For example, it was difficult to use it for an adhesive film with a copper foil because it became abnormally thin and easily caused a problem such as a decrease in interlayer insulation resistance or a short circuit. However, in the present invention, whiskers are dispersed in the resin, and the resin is reinforced by the whiskers. Therefore, the prepreg layer composed of the resin of the present invention and the whiskers exhibits film forming ability, and is transported, cut, and laminated. During the steps such as those described above, 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 disperse whiskers in a resin used for a conventional adhesive film or an adhesive film with a copper foil. Although these resins have a film forming ability even when the resin alone contains a high molecular weight component, etc., by dispersing the 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. In addition, it is also possible to reduce the amount of the high molecular weight component to be added by the amount corresponding to the enhancement of the film forming ability by dispersing the whiskers, thereby improving the heat resistance and adhesiveness of the resin in some cases. As the type of resin, for example, epoxy resin, bismaleimide triazine resin, polyimide resin,
Phenol resins, melamine resins, silicon resins, unsaturated polyester resins, cyanate ester resins, isocyanate resins, polyimide resins and various modified resins thereof are preferred. Among them, bismaleimide triazine resin and epoxy resin are particularly preferable in terms of printed wiring board characteristics. As the epoxy resin, bisphenol A
Epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, bisphenol A novolak epoxy resin, salicylaldehyde novolak epoxy resin, bisphenol F novolak epoxy resin, fat Cyclic epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, aliphatic cyclic epoxy resins and their halides, hydrogenated products, and mixtures of the above resins are preferred. It is. Above all, bisphenol A
A novolak type epoxy resin or a 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 resin, 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.
The range is preferably 2 to 100 parts by weight, more preferably 2 to 5 parts by weight for dicyandiamide, and 30 to 80 parts by weight for the other curing agents.

(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 as the curing accelerator. The ratio of the curing accelerator to the resin may be a conventionally used ratio, and is based on 100 parts by weight of the resin.
The range is preferably 0.01 to 20 parts by weight, and 0.1 to 1 part by weight.
A range of 0 parts by weight is more preferred.

(Diluent) The thermosetting resin of the present invention can be diluted with a solvent and used as a resin varnish.
Solvents include 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, and is preferably in the range of 1 to 200 parts by weight, more preferably 30 to 100 parts by weight, per 100 parts by weight of the resin.

(Other Compounding Agents) Further, in the present invention, conventionally known coupling agents, fillers and the like may be appropriately added to the resin, if necessary, in addition to the above-mentioned components.

(Proportion of Resin and Whisker) If the compounding amount of the electrically insulating whisker to the resin is less than 5 parts by weight based on 100 parts by weight of the resin solid content, the prepreg is crushed and scattered during cutting. 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, if the compounding amount of the whisker exceeds 350 parts by weight, the filling property of the inner layer circuit at the time of hot pressing and the filling property of the resin between the circuits are impaired, and the void whiskers are formed in the whisker composite resin layer after the hot pressing. This easily occurs, and the characteristics of the wiring board may be impaired. Therefore, the amount of the whisker is preferably 5 to 350 parts by weight based on 100 parts by weight of the resin solid content. In addition, the fillability of the inner layer circuit and the filling property between the circuits are excellent, and the manufactured wiring board has the same or higher rigidity than the wiring board manufactured using the prepreg using the conventional glass cloth. The whisker is added in an amount of 30 to 2 parts by weight based on 100 parts by weight of the resin solid content, because it can have dimensional stability and wire bonding properties.
More preferably, it is 30 parts by weight.

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

(Whisker Orientation in Prepreg Layer) The whisker in the insulating material composed of the electrically insulating whisker of the present invention and the resin in the B-stage state is in a state close to two-dimensional orientation (whisker is in the axial direction). (A state close to parallel to the surface on which the material layer is formed). Specifically, 70% of all whiskers in the semi-cured resin
% Or more of the whiskers are preferably oriented in directions within ± 30 degrees with respect to the plane direction of the insulating material. By orienting the whiskers in this manner, the insulating material of the present invention can obtain good handleability, as well as 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 shear force can be applied in the direction parallel to the copper foil such as a coater, rod coater, knife coater, squeeze coater, reverse roll coater, transfer roll coater, or a compressive force can be applied in a direction perpendicular to the copper foil surface. A coating method may be adopted.

In the wiring board insulating material and the wiring board using the same according to the present invention, the electrically insulating whiskers are not sandwiched between the conductor layers of the wiring board without resin. That is, since at least the insulating resin layer is formed between the conductor layers of the wiring board, the insulation reliability inherent in the insulating resin is obtained, and as a result, the insulation reliability of the wiring board can be improved. In addition, the insulating layer manufactured using the insulating material of the present invention has a better workability to laser and a finer whisker than glass, so that the insulating layer using the conventional glass cloth prepreg is used. Then, laser drilling, which was difficult, can be easily performed. Therefore, a diameter of 100 μm
The following small interstitial via holes (IV
H) can be easily manufactured, the circuit of the printed wiring board can be miniaturized, and it can greatly contribute to higher density and higher performance of electric equipment. Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

[0030]

【Example】

Example 1 (Production of insulating material for wiring board) Aluminum borate whiskers having a nominal length of 30 μm, a length distribution of 3 to 60 μm, and an average diameter of 1 μm were wetted with methyl ethyl ketone, and together with zirconia balls having a diameter of 0.3 mm, After putting in a planetary ball mill and grinding at 2400 rpm for 15 minutes,
The zirconia balls were removed by sieving with a 200 mesh nylon net. From the crushed whiskers, about 10,000 whiskers were photographed with a scanning electron microscope, and the length of the 100 whiskers was measured from the longest. The maximum length of the crushed whiskers was about 35 μm. Whisker pulverized into a thermosetting resin containing bisphenol A novolak type epoxy resin and bisphenol A novolak resin as main components is blended so as to be 90 parts by weight based on 100 parts by weight of the resin solid content, and aluminum borate whisker is added to the varnish. And stirred until homogeneously dispersed.
This is applied to a 18 μm-thick copper foil and a 50 μm-thick polyethylene terephthalate (PET) film by a knife coater, and heated and dried at a temperature of 150 ° C. for 10 minutes to remove the solvent and semi-cured the resin. Then, the insulating material with a copper foil having a whisker volume fraction of 30% and an insulating layer made of a whisker and an epoxy resin in a semi-cured state and a thickness of 50 μm and PET are removed by peeling, and the semi-cured epoxy resin is removed. Thickness of 30 μm, 50 μm, 10 μm
A 0 μm adhesive film was produced.

(Handling property of the produced insulating material) The produced insulating material with copper foil was treated with a cutter knife and a shear.
It could be cut cleanly without scattering of the resin, no blocking between insulating materials occurred, and the handling was good. Also,
The insulating material made by coating the PET 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 resin, and there was no blocking between insulating materials.

(Insulation Reliability) Next, the entire thickness is 0.8 m.
A copper foil double-sided copper-clad laminate with a copper foil thickness of 18 μm and a pattern to be used as an electrode on the inner surface of the electrolytic corrosion test is formed by etching, and a copper foil with a thickness of 50 μm above and below the insulating layer prepared above The attached insulating material was laminated and laminated so that the insulating material was in contact with the pattern serving as the electrode on the inner layer surface of the electrolytic corrosion test, and was subjected to hot pressing. The minimum interlayer insulating layer thickness of the obtained laminate was about 32 μm. A pattern to be an electrode of an outer layer was formed by etching on a portion corresponding to the position of an electrolytic corrosion test pattern to be an electrode of an inner layer of the laminated plate to obtain an electrolytic corrosion test piece. A voltage of 50 V DC was applied between the electrodes of the inner layer and the outer layer, and the insulation resistance was measured after a lapse of 1000 hours in an atmosphere of 85 ° C. and 85% RH.
A good value of ⁰⁹ Ω or more was shown, and it was confirmed that the insulating material was excellent in electric corrosion resistance.

(Other characteristics) The thickness 10
A single-sided roughened copper foil having a thickness of 18 μm was laminated on and under a 0 μm insulating material so that the roughened surface faced the insulating material, followed by hot pressing. When the bending elastic modulus of the obtained copper-clad laminate was measured by three-point bending, it was 20 GPa (no copper foil, average vertical length). Further, the dielectric constant was measured according to JIS C 6486, and it was 4.0 (1 MHz).
Further, when the displacement of the hole position between the uppermost plate and the lowermost plate when ten copper-clad laminates were drilled with a 0.3 mm diameter drill was measured, it was 20 μm or less. This copper-clad laminate is subjected to circuit processing, and the insulating material of the present invention having a thickness of 50 μm previously prepared on both surfaces thereof, and a single-sided roughened copper foil having a thickness of 18 μm on the outer surface thereof is further provided with a roughened surface as an insulating material. They were laminated so as to face each other, and were hot-pressed 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. The measurement location was the outer layer surface on a straight line having a length of 25 mm including a portion with and without an inner layer circuit immediately below. The 10-point average surface roughness of the step between the part with and without the inner layer circuit is:
3 μm or less, and good surface flatness that did not hinder circuit processing. Further, a predetermined diameter of the surface copper foil of the multilayer copper-clad laminate containing the inner layer circuit was etched to a diameter of 75 μm by etching.
After drilling a hole with an impact laser manufactured by Sumitomo Heavy Industries, Ltd., performing desmearing by permanganate treatment, performing electroless plating, and forming a circuit by pattern baking etching. . The insulating material of the present invention having a thickness of 30 μm is again laminated on both sides of the multilayer printed wiring board, and a single-sided roughened copper foil having a thickness of 18 μm is further laminated on the outer side thereof so that the roughened surface faces the insulating material. A multi-layer copper-clad laminate with an inner layer circuit was formed, and a hole having a diameter of 75 μm was formed at a predetermined position by etching, and the hole was formed with an impact laser manufactured by Sumitomo Heavy Industries, Ltd.
After desmearing by permanganate treatment and electroless plating, a circuit was formed by pattern baking etching. The above steps were repeated to produce a 10-layer 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 thermal expansion coefficient in the vertical direction is 10 pp
m / ° C (at room temperature), and the average bending elastic modulus in the vertical direction is 60 GPa at room temperature and 40 at high temperature (200 ° C).
GPa. The surface hardness measured by a Barcol hardness meter was 65 at room temperature and 50 at high temperature (200 ° C.). 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. As for the wire bonding conditions, 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. As a result, the wire bonding was successfully performed. Also, a TSOP having a size of 8 × 20 mm is connected to the surface circuit via solder on the 10-layer printed wiring board, and the TSOP mounting board is heated to −65 ° C. →→
When evaluated by a heat cycle test at 150 ° C., 2000
No defect such as disconnection occurred in the solder connection even after the cycle. A continuity test was performed on a circuit including an interstitial via hole inside the substrate, and no trouble such as disconnection occurred.

Example 2 (Production of insulating material for wiring board) A thermosetting resin mainly composed of a salicylaldehyde novolak type epoxy resin and a bisphenol A novolak resin was added to a thermosetting resin having a nominal length of 30 μm.
Aluminum borate whiskers having a length distribution of 3 to 60 μm and an average diameter of 1 μm are mixed with 90 parts by weight of aluminum borate whiskers with respect to 100 parts by weight of the resin solid content until the aluminum borate whiskers are uniformly dispersed in the varnish. Stirred. In this varnish with whiskers,
Alumina balls were added, and the mixture was put into a bead mill and pulverized for 60 minutes. This varnish was filtered under pressure through a nylon mesh of 200 mesh to separate alumina balls. This was applied to a copper foil of 18 μm thickness and a polyethylene terephthalate (PET) film of 50 μm thickness using a knife coater, and was heated and dried at 150 ° C. for 10 minutes to remove the solvent and semi-cured the resin. The thickness of the insulating layer made of epoxy resin in a semi-cured state with whiskers having a whisker volume fraction of 30% is 50 μm and 10 μm.
The insulating material with a copper foil of 0 μm and the PET are removed by peeling, and the thickness of the semi-cured epoxy resin is
A 50 μm adhesive film was produced. 50 μm produced
In an electric furnace at 600 ° C.
After baking for minutes, the resin was incinerated and removed, and the whiskers were taken out. The extracted whiskers were photographed with a scanning electron microscope to photograph about 10,000 whiskers.
The length of 00 whiskers was measured. The maximum length of the crushed whiskers was about 30 μm.

(Handleability of Insulation Material Produced) The insulation material with copper foil thus produced was cut with a cutter knife and a shear.
It could be cut cleanly without scattering of the resin, no blocking between insulating materials occurred, and the handling was good. Also,
The insulating material made by coating the PET 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 resin, and there was no blocking between insulating materials.

(Insulation Reliability) Next, the overall thickness is 0.8 m.
m, a pattern to be used as an electrode on the inner surface of the electrolytic corrosion test was formed on a glass epoxy double-sided copper-clad laminate having a copper foil thickness of 18 μm by etching. The insulating material with a foil was overlapped and laminated so that the insulating material was in contact with the pattern to be the electrode on the inner layer surface of the electrolytic corrosion test, and was hot-pressed. The minimum interlayer insulating layer thickness of the obtained laminate was about 32 μm. A pattern to be an outer layer electrode is formed by etching on a portion corresponding to the position of the electrolytic corrosion test pattern to be an inner layer electrode of this laminate,
An electrolytic corrosion test piece was obtained. DC 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
It showed a good value of Ω or more, and it was confirmed that the insulating material was excellent in electric corrosion resistance.

(Other Characteristics) The thickness 10
A single-sided roughened copper foil having a thickness of 18 μm was laminated on and under a 0 μm insulating material so that the roughened surface faced the insulating material, followed by hot pressing. When the bending elastic modulus of the obtained copper-clad laminate was measured by three-point bending, it was 20 GPa (no copper foil, average vertical length). Further, the dielectric constant was measured according to JIS C 6486, and it was 4.0 (1 MHz).
Further, when the displacement of the hole position between the uppermost plate and the lowermost plate when ten copper-clad laminates were drilled with a 0.3 mm diameter drill was measured, it was 20 μm or less. This copper clad laminate is subjected to circuit processing, and the insulating material 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 outer surface thereof is further provided with an insulating material having a roughened surface. And a hot-press molding to produce a multilayer copper-clad laminate with 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. The measurement location was the outer layer surface on a straight line having a length of 25 mm including a portion with and without an inner layer circuit immediately below. The 10-point average surface roughness of the step between the part with and without the inner layer circuit is:
3 μm or less, and good surface flatness that did not hinder circuit processing. Furthermore, a predetermined diameter of the surface copper foil of the multilayer copper-clad laminate containing the inner layer circuit is etched to a diameter of 7 mm.
A hole of 5 μm was drilled, the hole was drilled by an impact laser manufactured by Sumitomo Heavy Industries, Ltd., desmearing was performed by permanganic acid treatment, electroless plating was performed, and a circuit was formed by pattern baking etching. . The insulating material of the present invention having a thickness of 50 μm is again laminated on both sides of the multilayer printed wiring board, and a single-side roughened copper foil having a thickness of 18 μm is further laminated on the outer side thereof so that the roughened surface faces the insulating material. A multi-layer copper-clad laminate with an inner layer circuit is formed by pressure molding, a hole having a diameter of 75 μm is formed at a predetermined position by etching, and the hole is formed with an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After performing desmearing and electroless plating, a circuit was formed by pattern baking etching. The above steps were repeated to produce a 10-layer 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 thermal expansion coefficient in the vertical direction is 1
0 ppm / ° C (at room temperature), the average bending elastic modulus in the vertical direction is 60 GPa at room temperature, and high temperature (200 ° C)
Was 50 GPa. The surface hardness measured by a Barcol hardness meter was 65 at room temperature and 55 at high temperature (200 ° C.). 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 condition of wire bonding is as follows.
W, ultrasonic output time 50 μs, bond load 100
g, when the wire bonding temperature is 180 ° C.,
Good wire bonding was achieved. An 8 × 20 mm TSOP is connected to this 10-layer printed wiring board as a surface circuit via solder, and the TSOP mounting board is connected to a −65 mm.
When evaluated in a heat cycle test at 150 ° C
Even after 000 cycles, no defect such as disconnection occurred in the solder connection part. A continuity test was performed on a circuit including an interstitial via hole inside the substrate, and no trouble such as disconnection occurred. Next, comparative examples for confirming the effects of these examples will be described.

Comparative Example 1 (Preparation of Insulating Material) The same operation as in Example 1 was performed except that pulverization by the ball mill of Example 1 was not performed. Aluminum borate whiskers without ball mill grinding
About 10,000 pieces were photographed with a scanning electron microscope, and the length of 100 pieces was measured from the longest one. The maximum length of the unmilled whiskers was approximately 60 μm.

(Handling property of the produced insulating material) The produced insulating material with a copper foil was prepared using a cutter knife and a shear.
It could be cut cleanly without scattering of the resin, no blocking between insulating materials occurred, and the handling was good. Also,
The insulating material made by coating the PET 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 resin, and there was no blocking between insulating materials.

(Insulation Reliability) Next, the overall thickness is 0.8 m.
m, a pattern to be used as an electrode on the inner surface of the electrolytic corrosion test was formed on a glass epoxy double-sided copper-clad laminate having a copper foil thickness of 18 μm by etching. The insulating material with a foil was laminated and laminated so that the insulating material was in contact with the pattern to be the electrode on the inner layer surface of the electrolytic corrosion test, and was subjected to hot pressing. The minimum interlayer insulating layer thickness of the obtained laminate was about 32 μm. A pattern to be an electrode of an outer layer was formed by etching on a portion corresponding to the position of an electrolytic corrosion test pattern to be an electrode of an inner layer of the laminated plate to obtain an electrolytic corrosion test piece. A voltage of 50 V DC was applied between the electrodes of the inner layer and the outer layer, and the insulation resistance was measured after a lapse of 1000 hours in an atmosphere of 85 ° C. and 85% RH.
Becomes less than 0 ⁹ Omega, insulation reliability was confirmed that reduced.

Comparative Example 2 (Preparation of insulating material) The same operation as in Example 2 was performed except that the pulverizing time in the bead mill in Example 2 was changed to 5 minutes. The crushing operation for 5 minutes here uniformly mixes the whisker and the varnish, but the whisker crushing effect is a time set to such an extent that it is hardly observed. 50 made
The μm adhesive film was baked in an electric furnace at 600 degrees Celsius for 10 minutes, the resin was incinerated and removed, and the whiskers were taken out. Of the whiskers taken out, about 10,000 whiskers were photographed with a scanning electron microscope, and the length of the 100 whiskers was measured from the longest. The maximum length of the whiskers milled for 5 minutes was about 50 μm.

(Handling property of the produced insulating material) The produced insulating material with a copper foil was treated with a cutter knife and a shear.
It could be cut cleanly without scattering of the resin, no blocking between insulating materials occurred, and the handling was good. Also,
The insulating material made by coating the PET 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 resin, and there was no blocking between insulating materials.

(Insulation Reliability) Next, the overall thickness is 0.8 m.
On a glass epoxy double-sided copper-clad laminate having a copper foil length of 18 μm, a pattern to be an electrode on the inner surface of the electrolytic corrosion test was prepared by etching, and the upper and lower insulating layers having a thickness of 50 μm were formed. The insulating material with a copper foil was laminated and laminated so that the insulating material was in contact with the pattern to be the electrode on the inner layer surface in the electrolytic corrosion test, and was hot-pressed. The minimum interlayer insulating layer thickness of the obtained laminate was about 32 μm. A pattern to be an electrode of an outer layer was formed by etching on a portion corresponding to the position of an electrolytic corrosion test pattern to be an electrode of an inner layer of the laminated plate to obtain an electrolytic corrosion test piece. As a result of applying a voltage of 50 V DC between the electrodes of the inner layer and the outer layer and measuring an insulation resistance value after a lapse of 1000 hours in an atmosphere of 85 ° C. and 85% RH,
It was less than 10 ⁹ Ω, confirming that the insulation reliability was reduced.

[0044]

The insulating material for wiring boards of the present invention can be made extremely thin and has good handleability. Moreover, the printed wiring board using this has a smooth surface, good circuit workability, high rigidity, high mounting reliability, high surface hardness, good wire bondability, and small thermal expansion coefficient, dimensional stability. Will be better. Therefore, the prepreg of the present invention greatly contributes to thinning, high density, high productivity, high reliability, high speed, and low cost of a multilayer printed wiring board.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing one embodiment of the present invention.

FIG. 2 is a schematic sectional view for explaining the principle of the present invention.

[Explanation of symbols]

1. Short fiber filler 2. Resin 3. Outer layer circuit 4. Inner layer circuit 5. Inner layer substrate 6. Interlayer insulation layer thickness

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kazunori Yamamoto 1500 Oji Ogawa, Shimodate City, Ibaraki Prefecture Inside the Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Kazuhito Kobayashi 1500 1500 Oji Ogawa Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Inside the Shimodate Research Laboratory (72) Inventor: Kyo Daishiro 1500, Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. 72) Inventor: Takata Morita, 1500 Ogawa, Oji, Shimodate, Ibaraki Pref., Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inventor: Shigeharu Ariya 1500, Oji, Oji, Shimodate, Ibaraki Pref., Shimodate Research Laboratory, Hitachi Chemical (72) Inventor Naoyuki Urasaki 1500 Ogawa Oji, Shimodate-shi, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (72) Inventor Daisuke Fujimoto 1500 Ogawa, Oji, Shimodate-shi, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd.

Claims (4)

[Claims] An insulating material for a wiring board comprising a filler in the form of short fibers and a resin, wherein the length of the filler in the form of short fibers is determined by using the insulating material for a wiring board as an interlayer insulating material. Characterized in that the thickness is not more than 1.1 times the thickness of the interlayer insulating layer of the wiring board when manufactured. 2. The short fiber-shaped filler is an electrically insulating whisker having an average diameter in the range of 0.3 to 3.0 μm and a length of 3 μm or more. Item 2. The insulating material for a wiring board according to Item 1. 3. The insulating material for a wiring board according to claim 1, wherein the resin is an insulating thermosetting resin. 4. The insulating material for a wiring board according to claim 2, wherein the electrically insulating whisker is a ceramic whisker.