JPH09260843A - Multilayer copper-clad laminate board with inner circuit and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer copper-clad laminate board with an inner circuit superior in forming thin type, high-density, high-productivity, high- reliability and low-cost multilayer printed wiring boards. SOLUTION: A multilayer copper-clad laminate board with an inner circuit has an inner layer circuit board and outer layer circuit Cu foil joined on the circuit board through an insulation layer contg. electrically insulative whiskers dispersed in a thermosetting resin such that the whiskers are compounded with the resin and uniformly dispersed the rein which is then applied at least to one roughed surface of the foil and heated to dry enough to remove the solvent and half set it to form a Cu foil-attached prepreg, and the prepreg is formed on the inner layer circuit board having a previously completed circuit with the prepreg surface facing to this board and hot pressed to from the board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer copper clad laminate with an inner layer circuit for a multilayer printed wiring board which can be made thinner and higher in density, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a multilayer printed wiring board, a method of forming a circuit on a multilayer copper clad laminate with an inner layer circuit has been performed. A multilayer copper clad laminate with an inner layer circuit has a circuit on the inner layer. It is formed in advance and a copper foil is laminated on the entire surface with an insulating layer as an outer layer. This multilayer copper clad laminate with an inner layer circuit is obtained by thermocompressing a prepreg on both sides of a circuit-formed printed wiring board or a circuit-formed multilayer printed wiring board, and further laminating copper foil on the outside. The prepreg used here is generally a glass cloth prepreg in which a resin is semi-cured by impregnating and drying a glass cloth with a resin, but recently, a prepreg that does not use a glass cloth is formed into a film. An adhesive film (see JP-A-6-200216 and JP-A-6-242465) obtained by semi-curing a thermosetting resin having a function, or the adhesive film on one side of a copper foil instead of the copper foil and the prepreg. A copper foil-bonded adhesive film (see Japanese Patent Laid-Open No. 6-196862) has been proposed. Therefore, the conventionally known multilayer copper clad laminate with an inner layer circuit has an electrically insulating layer made of resin and glass cloth or an electrically insulating layer made of resin between the inner layer circuit and the outer layer copper foil.

[0003]

In recent years, electronic devices have become smaller and lighter, have higher performance, and have lower costs, so that multilayer copper clad laminates with inner layer circuits are made thinner, higher in density, and more productive. Higher reliability and lower cost are required. In order to realize thinning, the interlayer insulating layer must be thinned.
In addition, fine wiring is required for high density, and for that purpose, surface smoothness must be good and dimensional stability must be good. Further, fine through holes and interstitial via holes are required, and it is required that the drill workability and laser hole workability are good. Further, in terms of high productivity, it is required that the wire bonding property is good in order to shorten the component mounting time and the substrate rigidity is high in order to enlarge the work size. With regard to higher reliability, it is required to lower the coefficient of thermal expansion of the substrate, improve the adhesion of the plating, and improve the migration resistance in order to improve the connection reliability with the mounted components. It is difficult to meet these requirements with the conventional multilayer copper clad laminate containing an inner layer circuit.

At present, the glass cloth generally used for a multilayer copper clad laminate containing an inner layer circuit has a larger gap between yarns (glass fiber bundles) as the thickness thereof becomes thinner. Therefore, the thinner the cross is, the more easily the eyes are bent (the yarn is bent, or the warp yarns and the weft yarns, which should originally intersect at right angles, intersect each other at right angles). Due to this bending, abnormal dimensional changes and warpage tend to occur after hot pressing. Since the thinner the glass cloth is, the larger the gap between the yarns is, the volume fraction of the fibers in the interlayer insulating layer is lowered, and the rigidity is lowered. Therefore, in a component mounting process or the like after processing the outer layer circuit, the deflection is likely to be large, which is a problem. Currently, the thinnest glass cloth generally used is 30 μm, and the thickness of the interlayer insulating layer using this is 40 μm.
m. If the amount of resin is reduced in order to further reduce the thickness of the interlayer insulating layer, the filling of the concave and convex portions of the inner layer circuit with the resin is deteriorated and voids are generated. Further, if the glass cloth is made thinner than this, the strength of the cloth itself decreases, so that the glass cloth is easily broken in the prepreg manufacturing process in which the resin is impregnated into the glass cloth, which makes the manufacturing difficult.

Further, in a multilayer copper clad laminate containing an inner layer circuit produced by using these glass cloths, when the small-diameter drill is processed, the glass cloth unevenly distributed in the insulating layer easily causes core runout and the drill is easily broken. Further, due to the presence of the glass fiber, the perforation property by laser is poor, and the unevenness of the inner layer circuit is likely to appear on the surface, resulting in poor surface smoothness. on the other hand,
An adhesive film that is a prepreg without glass cloth,
The multilayer copper clad laminate with an inner layer circuit using an adhesive film with a copper foil as an insulating layer between the inner and outer layers can have a smaller thickness and is excellent in small-diameter drilling workability, laser hole workability, and surface smoothness. However, these multilayer copper clad laminates with inner layer circuits have extremely low rigidity because the outer insulating layer does not have a glass cloth base material. This low rigidity is remarkable at high temperatures, so that it is likely to bend during the component mounting process, and the wire bonding property is extremely poor. In addition, since there is no glass cloth base material in the outer insulation layer and the coefficient of thermal expansion is large, the difference in thermal expansion from the mounted parts is large, the connection reliability with the mounted parts is low, and the solder connection part due to thermal expansion and contraction during heating and cooling There are many problems such as cracks and fractures.

The present invention has been made as a result of intensive studies in view of such circumstances, and is an inner layer circuit excellent in thinning, high density, high productivity, high reliability and low cost of a multilayer printed wiring board. It is an object of the present invention to provide a multi-layered copper clad laminate containing the same.

[0007]

According to the present invention, such an object is to provide a multilayer copper clad laminate containing an inner layer circuit in which an inner layer circuit board and an outer layer circuit copper foil are laminated via an insulating layer,
The insulating layer is achieved by using a thermosetting resin in which electrically insulating whiskers are dispersed. Further, the method for producing a multilayer copper clad laminate containing an inner layer circuit of the present invention comprises blending a thermosetting resin with an electrically insulating whisker, and uniformly dispersing the whisker in the thermosetting resin by stirring, At least one surface is coated on the roughened surface of the copper foil, the solvent is removed by heating and drying, and the prepreg surface of the prepreg with copper foil in which the resin is semi-cured is the inner layer that has completed circuit processing in advance. It consists of laminating so as to face the circuit board and thermocompression molding.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the whiskers used in the present invention, ceramic whiskers which are electrically insulating and have an elastic modulus of 200 GPa or more are preferable. When the whiskers are less than 200 GPa, sufficient rigidity cannot be obtained when a multilayer printed wiring board is obtained. . As the type of whiskers, for example, one or more selected from aluminum borate, wollastonite, potassium titanate, basic magnesium sulfate, silicon nitride, and α-alumina can be used. Among them, aluminum borate whiskers have an elastic modulus of about 400.
It is much higher than GPa and glass, and has a small coefficient of thermal expansion.
Moreover, it is relatively inexpensive. A multilayer printed wiring board prepared from a multilayer copper clad laminate containing an inner layer circuit of the present invention using the aluminum borate whiskers as a base material in an outer insulating layer has a room temperature and a temperature lower than those of conventional multilayer printed wiring boards using a glass cloth. High rigidity at high temperature, excellent wire bonding property, small thermal expansion coefficient, and excellent dimensional stability. If the average diameter of the whiskers is 0.1 μm or less, it becomes difficult to mix with the resin varnish, and the coating workability decreases, and if it is 3 μm or more, the smoothness of the surface is adversely affected, and the whisker microscopic Uniform dispersibility is impaired. Therefore, the average diameter of the whiskers is 0.1-3μ
The range of m is preferable, and the average diameter is more preferably 0.5 to 2 μm because the coatability is good (smooth coating is easy).

The average length of the whiskers is preferably 10 times or more the average diameter. If it is less than 10 times, the reinforcing effect as a fiber becomes small, and at the same time, the two-dimensional orientation of the whiskers in the resin layer described later becomes difficult,
Sufficient rigidity cannot be obtained when used as a wiring board. For the above reasons, it is more preferable that the average length of the whiskers is about 20 times or more the average diameter. However, if the whiskers are too long, it becomes difficult to uniformly disperse the whiskers in the varnish, and at the same time, the coating workability deteriorates. In addition, there is a problem that whiskers that come into contact with a conductor circuit have a high probability of coming into contact with other conductor circuits, which may cause a short circuit between circuits due to migration of copper ions that tend to move along the fibers. Therefore, the average length of the whiskers is preferably 100 μm or less, more preferably 50 μm or less.

It is also effective to use whiskers surface-treated with a coupling agent in order to further enhance the rigidity and heat resistance of the multilayer printed wiring board. The whiskers surface-treated with a coupling agent have excellent wettability and bondability with a resin and can improve rigidity and heat resistance. The coupling agent used at this time is a silicon-based,
Known materials such as titanium, aluminum, zirconium, zirconaluminium, chromium, boron, phosphorus, and amino acids can be used.

The thermosetting resin used in the present invention is a glass cloth-based prepreg used for conventional multilayer copper clad laminates with inner layer circuits and an adhesive film containing no glass cloth base material, or copper. The thermosetting resin used for the adhesive film with foil can be used.
The thermosetting resin as used herein means a resin containing a resin, a curing agent, a curing accelerator, and a coupling agent, a diluent and the like which are used as necessary. Examples of the resin type include epoxy resin, bismaleimide triazine resin,
Polyimide resin, phenol resin, melamine resin, silicon resin, unsaturated polyester resin, cyanate ester resin, isocyanate resin, polyimide resin or various modified resins thereof are suitable. Among them, bismaleimide triazine resin and epoxy resin are particularly preferable in terms of printed wiring board characteristics. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, salicylaldehyde novolac type epoxy resin, Bisphenol F novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin,
Glycidylamine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, aliphatic cyclic epoxy resins and their halides, hydrogenates, and mixtures of said resins are suitable. Among them, bisphenol A novolac type epoxy resin or salicylaldehyde novolac type epoxy resin is preferable because it has excellent heat resistance.

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, polyvinylphenol, novolac resin bisphenol A novolac resin Also, halides of these phenolic resins can be used. Among them, bisphenol A novolac resin is preferable because it has excellent heat resistance. The ratio of the curing agent to the resin is preferably in the range of 2 to 100 parts by weight with respect to 100 parts by weight of the resin, and further 2 to 5 parts by weight for dicyandiamide and 30 to 80 parts by weight for other curing agents. Is preferred.

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 is preferably 0.01 to 20 parts by weight with respect to 100 parts by weight of the resin,
The range of 0.1 to 1.0% is more preferable.

The thermosetting resin used in the present invention may be diluted with a solvent and used as a resin varnish. As the solvent, acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide or the like can be used. The ratio of the diluent to the resin is 1 to 20 with respect to 100 parts by weight of the resin.
The range of 0 parts by weight is preferable, and the range of 30 to 100 parts by weight is more preferable. Further, in the present invention, conventionally known coupling agents, fillers and the like may be appropriately blended in the resin in addition to the above-mentioned components.

The blending amount of whiskers in the insulating layer of the multilayer copper clad laminate with an inner layer circuit of the present invention is preferably 5 to 50% by volume. If it is less than 5% by volume, sufficient rigidity cannot be ensured after circuit processing, and the curl of the prepreg with copper foil increases during the manufacturing process, and the resin tends to shatter and scatter when the prepreg with copper foil is cut. This is because the handling property such as is deteriorated. On the other hand, the content of the whiskers is set to 50% by volume or less because when the content exceeds 50% by volume, the hole filling property of the inner layer circuit and the embedding property in the uneven portion during the thermocompression molding during the manufacturing process are impaired, and the thermocompression molding is performed. This is because voids and scratches are likely to occur in the outer insulating layer formed of the whiskers and the resin later, and the characteristics of the wiring board may be impaired. Furthermore, it is excellent in hole filling of inner layer circuits and embedding in irregularities, and the multilayer printed wiring board produced has a rigidity equal to or higher than that of a wiring board manufactured using a conventional prepreg using glass cloth. For the reason that it is possible to have dimensional stability and wire bonding property, the compounding amount of the whiskers in the outer insulating layer of the multilayer copper clad laminate with an inner layer circuit of the present invention is 20 to 50% by volume with respect to the resin solid content. More preferably.

As the copper foil used in the present invention, there is used an electrolytic copper foil, a rolled copper foil, or an ultrathin copper foil with a carrier, which has at least one roughened surface and is used for a conventional printed wiring board. By forming a thermosetting resin layer containing whiskers on a smooth copper foil surface, it is not possible to sufficiently secure the adhesion between the copper foil and the thermosetting resin layer containing whiskers. It is preferable to form a thermosetting resin layer containing whiskers on the roughened surface. The thickness of the copper foil is preferably thin, 30 μ, because fine circuits can be formed.
m or less is preferable. More preferably, an ultrathin copper foil having a thickness of 10 μm or less is preferable, but in this case, it is preferable to use a copper foil with a carrier because it is difficult to handle by itself.

When the resin varnish containing whiskers is applied to the copper foil, a shearing force can be applied in a direction parallel to the surface of the copper foil, or a compressive force can be applied in a direction perpendicular to the surface of the copper foil. Adopt a coating method. Specifically, for example, a coating method such as a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, or a transfer roll coater is used.

In the present invention, a copper foil coated with a thermosetting resin containing whiskers is thermocompression-molded together with an inner layer board to produce a multilayer copper clad laminate with an inner layer circuit. By thermoforming in this way, the whiskers in the resin coated on the copper foil can be brought into a state closer to a two-dimensional orientation. At the same time, the resin can be cured by thermocompression molding to firmly bond the copper foil and the insulating layer. Thermocompression molding can use the heating and pressing press used in the conventional thermocompression molding of copper clad laminates,
Thermocompression molding is performed under the conditions of a conventional copper clad laminate, a pressure of 1 to 20 MPa, a temperature of 130 to 250 ° C., and a time of 1 to 120 minutes.

The outer insulating layer of the multilayer copper clad laminate with an inner circuit according to the present invention does not use an intermediate product such as glass cloth having a limited thickness as a base material as in the conventional case, but an extremely fine whisker. Is used as the base material directly in the manufacturing process, the productivity is high and the thickness of the insulating layer can be freely set. Therefore, a multilayer copper clad laminate having an inner layer circuit having an extremely thin outer insulating layer, which cannot be produced by the conventional glass cloth prepreg, can be produced, and it can greatly contribute to the thinning of the multilayer printed wiring board. Further, in the conventional multilayer copper clad laminate with an inner layer circuit using a conventional glass cloth base material, the glass fibers in the outer insulating layer are partially densely packed at the intersections of the fibers. Since the high-density filling part of does not collapse at the time of thermocompression molding, unevenness appears on the surface due to cross stitches and unevenness of the inner layer circuit, but the multilayer copper clad laminate with inner layer circuit of the present invention Since the prepreg with the copper foil in which the whiskers are uniformly dispersed in the thermosetting resin at a relatively low density is used, the whiskers will have a higher degree of two-dimensional orientation and density in the portion where the inner layer circuit is present during thermocompression molding. By crushing more than other parts, it is possible to absorb the irregularities of the inner layer circuit, and since the whiskers used are much thinner than conventional glass fibers,
The surface of the multilayer copper clad laminate with an inner layer circuit of the present invention is extremely smooth. That is, the inner layer circuit-containing copper clad laminate of the present invention is excellent in surface smoothness, the multilayer printed wiring board produced from the inner layer circuit-containing multilayer copper clad laminate of the present invention is capable of fine wiring. As a result, the wiring density can be increased. Further, whiskers, which are the base material of the outer insulating layer of the multilayer copper clad laminate with an inner layer circuit of the present invention, have much better workability with a laser than the conventional base material, glass cloth. Laser drilling, which was difficult with an insulating layer using glass cloth, can be easily performed. for that reason,
A small diameter interstitial via hole (IVH) having a diameter of 100 μm or less can be easily manufactured, and miniaturization and high density of wiring can be achieved, which greatly contributes to miniaturization and high performance of electronic equipment. Further, in the outer layer insulating layer of the multilayer copper clad laminate containing an inner layer circuit of the present invention, the holes drilled by the laser are appropriately projected whiskers on the hole wall, so that the adhesion of the plating to the insulating layer of the resin alone by the laser. It is much better than the adhesion of plating in open holes, and the reliability of interlayer connection of electric circuits is high. Therefore, the reliability of the electronic device can be improved.

In the outer layer insulating layer of the multi-layered copper clad laminate with inner layer circuit of the present invention, the whiskers as the base material are uniformly dispersed, so that the conventional multi-layer with inner layer circuit using glass cloth as the base material. When drilling a copper clad laminate,
The problem of core misalignment and breakage due to uneven distribution of glass is unlikely to occur. Therefore, it is possible to increase the number of piles when drilling holes and improve productivity, and moreover, the positional accuracy of the drilled holes is improved, so that finer wiring and higher adhesion can be achieved, and high electronic device It can greatly contribute to performance improvement. Further, the whiskers of the base material of the outer insulating layer of the multilayer copper clad laminate with an inner layer circuit of the present invention are:
It has much higher rigidity than the conventional glass cloth of the base material,
Moreover, it is evenly dispersed throughout the glass cloth. Therefore, the multilayer copper clad laminate with inner layer circuit of the present invention has higher surface hardness and excellent wire bonding property than those using the conventional glass cloth, and is excellent in mountability of electronic components. Further, the multilayer copper clad laminate with an inner layer circuit of the present invention can have a higher elastic modulus than the multilayer copper clad laminate with an inner layer circuit using a conventional glass cloth by increasing the compounding amount of whiskers, and is manufactured using this. Since the printed wiring board thus produced has high rigidity and the deflection during solder reflow is reduced, the productivity can be improved by increasing the work size. Further, in the multilayer copper clad laminate with an inner layer circuit of the present invention, the insulating layer has much higher rigidity than glass,
In addition, it is uniformly reinforced by whiskers with a low coefficient of thermal expansion, and has dimensional stability equivalent to or better than that of a conventional multi-layer copper-clad laminate with an inner layer circuit that uses glass cloth, so the circuit of the printed wiring board can be miniaturized. . Further, the printed wiring board manufactured from the multilayer copper clad laminate containing the inner layer circuit of the present invention has a small coefficient of thermal expansion and a small difference in coefficient of thermal expansion from the electronic components to be mounted, so that the connection reliability between the board and the components is high. Can contribute to improving the reliability of electronic devices. In addition, the multilayer copper clad laminate with an inner layer circuit of the present invention has an insulating layer made of fine and discontinuous whiskers as a base material instead of continuous fibers such as glass cloth. It is possible to reduce the occurrence of short circuit accidents due to migration of ions, which contributes to the improvement of reliability of electronic devices. Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

[0021]

【Example】

Example 1 47 parts by weight of tetrabromobisphenol A based on 100 parts by weight of bisphenol A novolac type epoxy resin,
Aluminum borate whiskers having an average diameter of 0.8 μm and an average fiber length of 20 μm in a thermosetting resin varnish consisting of 37 parts by weight of bisphenol A novolac resin, 0.5 parts by weight of 2-methyl-4-methylimidazole, and 100 parts by weight of methyl ethyl ketone. 89 parts by weight was blended with 100 parts by weight of the resin solid content, and the mixture was stirred until the aluminum borate whiskers were uniformly dispersed in the varnish. This is thickness 18
The roughened surface of the one-side roughened electrolytic copper foil having a thickness of μm was coated with a knife coater, and dried by heating at a temperature of 150 ° C. for 10 minutes to remove the solvent and semi-cured the resin. By appropriately adjusting the gap of the knife coater, a prepreg with a copper foil having a prepreg layer of whiskers and semi-cured resin with a thickness of 30 μm was produced. Whisker volume fraction of prepreg layer is 30 vo
1%.

The prepared prepreg with a copper foil was laminated on a double-sided copper clad laminate having a copper foil thickness of 18 μm and an insulating layer thickness of 100 μm so that the prepreg surface would match the circuit surface of the inner layer board having a circuit formed thereon, and the temperature was 170 Thermosetting was performed at a pressure of 2 MPa for 60 minutes to obtain 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 by a stylus type surface roughness meter, and as a result, it was about 2 μm or less, indicating good surface smoothness. Further, the outer copper foil of the multilayer copper clad laminate containing the inner layer circuit is etched at a predetermined position to have a diameter of 5 mm.
A hole from which the copper foil was removed was opened in a circular shape of 0 μm, and the hole was irradiated with a laser beam. The oscillation frequency of the laser beam is 15
0 Hz, irradiation pulse number 5, energy fluence is 2
It was 3.5 J / cm ² . Next, after performing desmear treatment with permanganic acid to this sample, electroless copper plating was performed, and as a result of microscopic observation of the cross section of the hole of this sample, the insulating layer of the portion irradiated with the laser beam was removed, The hole reached the inner layer circuit. The hole wall has a slight taper from the laser beam incident side toward the inner layer circuit in the direction of decreasing hole diameter, and the diameter of the hole bottom part that is the connection part with the inner layer circuit is 40 μm, but a sufficient connection area as a conduction hole. Was secured. Furthermore, the hole wall is 3 μm from the resin part.
Since the whiskers protruded in the front and back, the throwing power of the plating was extremely good.

Further, the amount of deviation between the hole positions of the uppermost plate and the lowermost plate was measured when five multi-layered copper clad laminates with an inner layer circuit according to the present invention were stacked and punched with a drill having a diameter of 0.3 mm. It was 20 μm or less. Further, after forming a circuit on the multilayer copper clad laminate containing the inner layer circuit, an IC bare chip was mounted and connected to the 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. A part of the multilayer copper clad laminate containing the inner layer circuit was cut out, the outer layer copper foil was removed by etching, and the appearance was observed. As a result, no voids or scratches were found, and the embeddability in the unevenness of the inner layer circuit was good. The flexural modulus of the multilayered copper clad laminate containing the inner layer circuit after etching the outer layer copper foil was 3
As a result of measuring by point bending, at room temperature, 40 GPa, 20
It was 20 GPa at 0 ° C. Further, after the outer layer copper foil was etched, the coefficient of thermal expansion of the inner layer circuit-containing multilayer copper clad laminate at room temperature by TMA was measured and found to be 12 p.
pm.

[0024]

Example 2 A varnish consisting of 70 parts by weight of a bisphenol A type novolak resin, 1 part by weight of N-methylimidazole, and 100 parts by weight of methyl ethyl ketone to 100 parts by weight of salicylaldehyde novolak type epoxy resin, an average diameter of 0.8 μm and an average value. 89 parts by weight of silicon nitride whiskers having a fiber length of 20 μm were mixed with 100 parts by weight of the resin solid content, and stirred until the silicon nitride whiskers were uniformly dispersed in the varnish. This is applied to the roughened surface of a one-sided roughened electrolytic copper foil having a thickness of 18 μm with a knife coater, and the temperature is 150 ° C.
The resin was semi-cured while the solvent was removed by heating and drying at 10 minutes. Adjust the gap of the knife coater appropriately,
A prepreg with a copper foil having a prepreg layer of whiskers and semi-cured resin having a thickness of 30 μm was produced. The whisker volume fraction of the prepreg layer was 30 vol%. The prepared prepreg with a copper foil was laminated on a printed wiring board for an inner layer board in which a circuit was formed on a double-sided copper-clad laminate having a copper foil thickness of 18 μm and an insulating layer thickness of 100 μm so that the prepreg surface was aligned with the circuit surface. Then, it was subjected to thermocompression molding to obtain a multilayer copper-clad laminate containing an inner layer circuit. When the surface roughness of this multilayer copper clad laminate containing an inner layer circuit was measured with a stylus type surface roughness meter, the surface roughness was about 2 μm or less, indicating good surface smoothness.
Further, a hole in which the copper foil was removed in a circular shape having a diameter of 50 μm was formed by etching at a predetermined position of the outer layer copper foil of the multilayer copper clad laminate containing the inner layer circuit, and the hole was irradiated with a laser beam. The oscillation frequency of the laser beam was 150 Hz, the number of irradiation pulses was 5, and the energy fluence was 23.5 J / cm ² . Next, after performing desmearing treatment with permanganate to this sample, electroless copper plating was performed, and as a result of microscopic observation of the cross section of the hole of this sample, the insulating layer in the portion irradiated with the laser beam was removed, The hole reached the inner layer circuit. The hole wall has a slight taper in the direction from the laser beam incident side to the inner layer circuit, and the diameter of the hole bottom part that is the connection part with the inner layer circuit is 40 μm, but a sufficient connection area as a conduction hole. Was secured. Furthermore, since the whiskers protruded from the resin portion by about 3 μm on the hole wall, the throwing power of the plating was extremely good.

Further, the amount of deviation between the hole positions of the uppermost plate and the lowermost plate was measured when five multi-layered copper clad laminates with an inner layer circuit according to the present invention were stacked and punched with a drill having a diameter of 0.3 mm. It was 20 μm or less. Furthermore, after forming a circuit on this multilayer copper clad laminate containing an inner layer circuit, a bare chip was mounted and connected to the surface circuit by wire bonding. The wire bonding conditions are 1 W for ultrasonic output and 5 for ultrasonic output time.
When 0 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., good wire bonding was possible. A part of this multilayer copper clad laminate containing an inner layer circuit was cut out, the outer layer copper foil was removed by etching, and the appearance was observed. As a result, no voids or scratches were found, and the embedding property in the unevenness of the inner layer circuit was good. The flexural modulus of the multilayered copper clad laminate containing the inner layer circuit after etching the outer layer copper foil was measured by three-point bending. As a result, it was 40 GPa at room temperature and 30 GPa at 200 ° C. In addition, after the outer layer copper foil was etched, the coefficient of thermal expansion of the inner layer circuit-containing multilayer copper clad laminate at room temperature by TMA was 13 ppm. Next, comparative examples for confirming the effects of these examples will be described.

[0026]

[Comparative Example 1] The same resin varnish as in Example 1 was applied to a thickness of 30 μm.
Impregnated and coated on glass cloth at 10 ℃ at a temperature of 150 ℃
The resin was semi-cured while heating and drying for n to remove the solvent, and a glass epoxy prepreg having a thickness of 30 μm, which was made of glass cloth and epoxy resin in a semi-cured state, was produced. This glass epoxy prepreg, copper foil thickness 18
The printed wiring board for the inner layer is formed on the upper and lower sides of the circuit formed on the double-sided copper clad laminate having a thickness of 100 μm and the insulating layer is 100 μm. Was laminated so as to face the prepreg, and thermocompression-molded to obtain a multilayer copper clad laminate including an inner layer circuit. When the surface roughness of this multilayer copper clad laminate with an inner layer circuit was measured by a stylus type surface roughness meter, the surface roughness was 8 μm or more. Further, a hole in which the copper foil was removed in a circular shape having a diameter of 50 μm was formed by etching at a predetermined position of the outer layer copper foil of the multilayer copper clad laminate containing the inner layer circuit, and the hole was irradiated with a laser beam. The oscillation frequency of the laser beam was 150 Hz, the number of irradiation pulses was 5, and the energy fluence was 23.5 J / cm ² . Next, this sample was subjected to desmearing treatment with permanganate, followed by electroless copper plating, and the cross section of the hole of this sample was observed under a microscope. The resin in the insulating layer at the portion irradiated with the laser beam was partially removed, but the glass cloth remained, and the hole did not reach the inner layer circuit. That is, IVH could not be formed. Also,
The amount of deviation of the hole positions between the uppermost plate and the lowermost plate when 5 layers of the multi-layered copper clad laminate with an inner layer circuit of the present invention were piled up with a drill having a diameter of 0.3 mm was measured and found to be 50 μm or more. . Furthermore, after forming a circuit on this multilayer copper clad laminate containing an inner layer circuit, a bare chip was mounted and connected to the surface circuit by wire bonding. As for the wire bonding conditions, when the ultrasonic wave output was 1 W, the ultrasonic wave output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., wire peeling occurred. When a part of the multilayer copper clad laminate containing the inner layer circuit was cut out, the outer layer copper foil was removed by etching, and the appearance was observed, it was found that fading occurred.

[0027]

[Comparative Example 2] The same resin varnish as in Example 1 was applied to a thickness of 20 μm.
m glass cloth impregnated and coated at a temperature of 150 ° C for 10 m
An attempt was made to manufacture a glass epoxy prepreg having a thickness of 30 μm, which was composed of glass cloth and an epoxy resin in a semi-cured state, in which the resin was semi-cured by heating and drying for 1 hour to remove the solvent. The purpose is to reduce the amount of glass and increase the amount of resin in order to prevent blurring due to insufficient embedding of resin in the inner layer circuit, which occurred in Comparative Example 1. However, the cloth could not bear the weight of the applied resin in the drying oven and broke.

[0028]

Comparative Example 3 A high-molecular-weight epoxy polymer having a weight-average molecular weight of 500,000 and a thermosetting resin containing bisphenol A type epoxy resin as a main component and having a film-forming ability were prepared by using a one-side roughened electrolytic copper having a thickness of 18 μm. The roughened surface of the foil was coated with 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. By appropriately adjusting the gap of the knife coater, a prepreg with a copper foil having a prepreg layer of a semi-cured resin having a thickness of 30 μm was produced. The prepared prepreg with a copper foil is formed into a circuit on a double-sided copper-clad laminate having a copper foil thickness of 18 μm and an insulating layer thickness of 100 μm, and a printed wiring board for an inner layer board prepared in advance is provided on the circuit surface. The layers were laminated so that the prepreg surfaces were aligned, and thermocompression-molded to obtain 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 by a stylus type surface roughness meter, and the surface roughness was about 2
It was not more than μm, and the surface smoothness was good. further,
A hole in which the copper foil was removed in a circular shape having a diameter of 50 μm by etching was made at a predetermined position of the outer layer copper foil of this multilayer copper clad laminate containing an inner layer circuit, and the hole was irradiated with a laser beam. The oscillation frequency of the laser beam is 150 Hz, the number of irradiation pulses is 5, and the energy fluence is 23.5 J / cm ^2. And Next, this sample was subjected to desmearing treatment with permanganate, followed by electroless copper plating, and the cross section of the hole of this sample was observed under a microscope. The insulating layer in the portion irradiated with the laser beam was removed, and the hole reached the inner layer circuit. The hole wall has a slight taper in the direction from the laser beam incident side to the inner layer circuit, and the diameter of the hole bottom part that is the connection part with the inner layer circuit is 40 μm, but a sufficient connection area as a conduction hole. Is secured. The hole wall was smoother than in Examples 1 and 2, and peeling of the plating was observed in part.

Further, the amount of deviation between the hole positions of the uppermost plate and the lowermost plate was measured when five multi-layered copper clad laminates with an inner layer circuit of the present invention were stacked and punched with a drill having a diameter of 0.3 mm. It was 20 μm or less. Furthermore, after forming a circuit on this multilayer copper clad laminate containing an inner layer circuit, a bare chip was mounted and connected to the surface circuit by wire bonding. The wire bonding conditions are 1 W for ultrasonic output and 5 for ultrasonic output time.
When 0 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., peeling of many wires occurred. A part of the multilayer copper clad laminate containing the inner layer circuit was cut out, the outer layer copper foil was removed by etching, and the appearance was observed. As a result, no voids or scratches were found, and the embeddability in the unevenness of the inner layer circuit was good. The bending elastic modulus of the multilayer copper clad laminate containing the inner layer circuit after etching the outer layer copper foil was measured by three-point bending. As a result, it was 20 GPa at room temperature and 10 GPa at 200 ° C. Further, after the outer layer copper foil was etched, the coefficient of thermal expansion of the inner layer circuit-containing multilayer copper clad laminate at room temperature by TMA was 20 ppm when measured at room temperature.

[0030]

INDUSTRIAL APPLICABILITY The multilayer copper clad laminate with an inner layer circuit according to the present invention can be extremely thinned, has a smooth surface, has good circuit workability, and has high rigidity, so that mounting reliability is high and surface hardness is high. Since it is high, the wire bondability is good, and since the coefficient of thermal expansion is small, the dimensional stability is good. Therefore, the multilayer copper clad laminate with an inner layer circuit of the present invention greatly contributes to thinning, high density, high productivity, high reliability and low cost of the multilayer printed wiring board.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C08L 79/00 LQZ B29C 67/14 G // B29L 9:00 C08K 7:04

Claims (6)

[Claims] 1. A multilayer copper clad laminate containing an inner layer circuit, comprising an inner layer circuit board and an outer layer circuit copper foil laminated via an insulating layer, wherein the insulating layer comprises an electrically insulating whisker in a thermosetting resin. A multi-layer copper clad laminate with an inner layer circuit characterized by being dispersed. 2. The electrically insulating whiskers have an elastic modulus of 200.
The multilayer copper clad laminate with an inner layer circuit according to claim 1, which is a ceramic whisker having GPa or more. 3. The electrically insulating whiskers have an average diameter of 0.1.
3. The multilayer copper clad laminate with an inner layer circuit according to claim 1 or 2, wherein the multilayer copper clad laminate has an inner length of 3 to 3 μm and an average length of 10 times or more the average diameter. 4. The multilayer copper clad laminate with an inner layer circuit according to claim 1, wherein the electrically insulating whiskers are aluminum borate. 5. The multilayer copper clad laminate with an inner layer circuit according to claim 1, wherein the thermosetting resin is mainly composed of epoxy resin or polyimide resin. 6. A roughened surface of a copper foil having at least one surface roughened after blending an electrically insulating whisker with a thermosetting resin and uniformly dispersing the whisker in the thermosetting resin by stirring. Coat on top, remove the solvent by heating and drying, stack the prepreg surface of the prepreg with copper foil in which the resin is semi-cured so that it faces the inner layer circuit board on which circuit processing has been completed in advance, and thermocompress molding A method for producing a multi-layer copper-clad laminate including an inner layer circuit, comprising: