JPH09283926A - Multilayer board manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a multilayer circuit board which 13 superior in heat radiation and has a high reliability, without causing voids or cracks in through- holes. SOLUTION: This multilayer board manufacturing method is to hot compression-form inner layer circuit board and metal foils for forming circuits of surface layers through adhesive prepregs into a multilayer board. The metal foils for forming circuits of the surface layers are each 100μm thick or more, the adhesive prepregs adhered to the circuit faces use a glass nonwoven cloth for its base and inorg. filler-contained thermosetting resin for the impregnation resin. The inorg. filler content is pref. 50wt. parts or more to 100wt. parts of the thermosetting resin and resin content of the prepreg (incl. the inorg. filler) is pref. 75wt.% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer board which has excellent heat dissipation and has no voids in its inner layer.

[0002]

2. Description of the Related Art Recently, MPU (Micro Processi) to be incorporated into electronic and electrical equipment which has been highly densified, highly integrated and miniaturized.
ng Unit) has a higher clock frequency and an increased total number of pins. Along with this, the power consumed by the MPU and the amount of heat generated are also increasing. A metal base printed wiring board having a metal plate (aluminum, iron, stainless steel, etc.) as a core material is used as a printed wiring board on which an MPU having a large amount of heat generation is mounted in order to improve heat dissipation. When a conductive through hole is formed in a metal base printed wiring board to form a high density wiring, it is necessary to insulate between the metal base and the through hole wall. In order to insulate, a through hole larger than the through hole is formed at a position where the through hole of the metal base is to be formed, and the through hole is filled with resin.
Then, a through hole is formed in the resin portion to form a conductive through hole. The filled resin is present between the wall of the through hole formed in the metal base and the wall of the conductive through hole to insulate them from each other. However, cracks are likely to occur in the filled resin due to heat stress and the like, and insulation reliability is low. In addition, since the core material of the metal-based printed wiring board has conductivity, it is not possible to form circuits for the power supply layer and the ground layer on it, and it is difficult to make the circuits multi-layered to achieve high density. I have to. On the other hand, there is proposed a multilayer board in which a metal foil having a thickness of 70 μm or more is punched into a predetermined circuit shape and is inserted in a layer of a prepreg layer, and heat-pressed together with the metal foil arranged on the surface to be integrated. (Japanese Patent Laid-Open No. 1-190419). This multi-layer board can be expected to have heat dissipation because the metal foil forming the circuit of the inner layer is thick. However, in the circuit portion of the inner layer, there is a large difference in unevenness between the place where the circuit is present and the place where the circuit is not present, so that the recess cannot be sufficiently filled with the resin, and a void is likely to occur. Further, since the thermosetting resin forming the prepreg contains no filler, cracks are likely to occur due to heat stress or the like.

[0003]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide a multilayer board capable of forming a circuit of a power supply layer and an earth layer with excellent heat dissipation and to avoid the risk of cracking due to thermal stress. To improve the reliability of through-hole insulation.

[0004]

In order to solve the above-mentioned problems, a method of manufacturing a multilayer board according to the present invention is such that an inner circuit board and a metal foil to be a circuit of a surface layer are heated and pressed through an adhesive prepreg. In the manufacturing method in which the metal foil for forming at least one layer of the inner layer circuit board is 100 μm thick
Above. Then, a glass nonwoven fabric is used as the base material and an inorganic filler-containing thermosetting resin is used as the impregnating resin for the adhesive prepreg that comes into contact with the circuit surface composed of the metal foil of 100 μm or more.

Since a metal foil having a thickness of 100 μm or more is used as at least one layer of the inner layer circuit, the heat dissipation is good and a highly integrated MPU having a large heat generation amount can be mounted. The circuit layer formed of a metal foil having a thickness of 100 μm or more of the inner layer circuit board has a large unevenness in the place where the circuit exists and where it does not exist. However, in the heat and pressure molding step of the multilayer board, the thermosetting resin containing an inorganic filler, which is softened and fluidized by the adhesive prepreg in contact with the circuit layer, flows into the concave portion without the circuit and fills the concave portion. At this time, since the glass fibers constituting the glass nonwoven fabric which is the base material of the adhesive prepreg also flow into the recesses together, the recesses are sufficiently filled and a multilayer board without voids can be manufactured. Since it is a thermosetting resin containing an inorganic filler, the coefficient of thermal expansion of the heat of the thermosetting resin is small, and the generation of cracks due to thermal stress can be suppressed.

When a glass woven cloth is used as a base material of an adhesive prepreg that comes into contact with a circuit surface composed of a metal foil of 100 μm or more, even if the impregnating resin of the prepreg is a thermosetting resin containing an inorganic filler. Since the glass fiber does not move to the concave portion having no circuit, the concave portion cannot be sufficiently filled with the inorganic filler-containing thermosetting resin. In the present invention, for the first time, a glass nonwoven fabric is used as a base material for an adhesive prepreg that comes into contact with a circuit surface composed of a metal foil of 100 μm or more and a thermosetting resin containing an inorganic filler is used as an impregnating resin. It is possible to solve the intended problem.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In an adhesive prepreg obtained by impregnating a glass nonwoven fabric with an inorganic filler-containing thermosetting resin, the content of the inorganic filler is preferably 50 parts by weight or more based on 100 parts by weight of the thermosetting resin. . By doing so, it is convenient for suppressing the generation of cracks due to thermal stress. The resin amount (including the inorganic filler) of the adhesive prepreg is preferably 75% by weight or more. This is more advantageous in filling the recesses having no circuit with the thermosetting resin containing the inorganic filler. The glass non-woven fabric, which is the base material of the adhesive prepreg, is formed by binding glass fibers together with a binder, and it is preferable that the binder contains a coupling agent. The coupling agent is preferably phenylaminosilane. It is possible to improve the moisture resistance of the multilayer board.

In the present invention, the above-mentioned glass nonwoven fabric base material prepreg is used as the adhesive prepreg that comes into contact with the circuit surface made of a metal foil having a thickness of 100 μm or more, but the base of the adhesive prepreg used at other locations. The types of materials and thermosetting resins are not particularly limited. Further, the types of the base material and the thermosetting resin used for producing the laminated board which becomes the insulating substrate of the inner layer circuit board are not particularly limited. In carrying out the present invention, a thickness of 100
The material of the metal foil (metal sheet) having a thickness of μm or more is copper, aluminum, nickel or the like, and is not particularly limited as long as it is a conductive metal, but from the viewpoint of using existing circuit processing equipment, copper foil ( It is preferable to use a copper sheet).
The thermosetting resin used in the present invention is preferably a heat resistant resin such as an epoxy resin, a cyanate resin or a polyimide resin. In particular, the epoxy resin is tough and has excellent resistance to heat stress. In order to improve the adhesiveness between the circuit surface of the inner layer circuit board and the resin in the heat and pressure molding of the multilayer board, the circuit surface is roughened in advance. There are mechanical and chemical roughening methods, but chemical roughening is preferable from the viewpoint of adhesiveness to the resin. In addition, it is desirable that the heat and pressure molding of the multilayer plate is performed in a vacuum or reduced pressure atmosphere in order to further suppress the generation of voids. The material of the glass fiber forming the glass nonwoven fabric is E glass, S glass, D glass or the like which is usually used for electrical insulation, and is not particularly limited.

[0009]

【Example】

Examples 1-9, Comparative Examples 1-2 Bisphenol A type epoxy resin ("Ep made by Yuka Shell
-1045 ", epoxy equivalent: 500) and cresol novolac type epoxy resin (" YDCN-70 "manufactured by Tohto Kasei)
4 ", epoxy equivalent: 210) was mixed with dicyandiamide as a curing agent and 2-ethyl-4-methylimidazole as a curing accelerator to prepare varnish A. Also, varnish A
A varnish was prepared by adding the inorganic filler (aluminum hydroxide) at various ratios shown in each table to 100 parts by weight of the epoxy resin composition. A woven glass cloth (weight: 210 g / m ² ) was impregnated with varnish A and dried to obtain a prepreg A having a resin amount of 42% by weight. Further, the above-mentioned various inorganic filler-added varnishes were impregnated and dried in a glass nonwoven fabric (weight: 35 g / m ² ) in which the coupling agent in the binder was as shown in each table, and each resin amount shown in each table was dried. The adhesive prepreg of was obtained. The resin amount shown here is calculated by the following (Formula 1).

[0010]

[Equation 1]

The inner layer circuit board was manufactured as follows. First, two prepregs A are stacked, one on each side of each of the copper foils of various thicknesses shown in Table 1, and heat-pressed in a reduced pressure atmosphere to form a double-sided copper-clad laminate with an insulating layer thickness of 0.4 mm. A board was manufactured. The copper foils on both sides were etched by a usual method to form circuits for the ground layer and the power supply layer to obtain an inner layer circuit board. The circuit pattern is shown in FIG. Prior to the heat and pressure molding of the multilayer board, the circuit surface of the inner layer circuit board was blackened (chemically roughened) by a usual method. One adhesive prepreg prepared with the above-mentioned inorganic filler-added varnish is placed in contact with the circuit surfaces on both sides of this inner layer circuit board, and one prepreg A is placed outside the adhesive prepreg. A copper foil having a thickness of 18 μm was arranged, and heat-press molding was performed in a reduced-pressure atmosphere to produce a four-layer multilayer board. The characteristics are also shown in each table.

Conventional Example Two prepregs A are disposed on each of the circuit surfaces on both sides of the inner layer circuit board in Example 1, and a copper foil having a thickness of 18 μm is disposed on the outermost surface, and four layers are laminated by heat and pressure molding. A board was manufactured. The characteristics are also shown in Table 3.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

The evaluation methods for the characteristics shown in the above tables are as follows. Number of cracks generated: The number of through holes in which cracks occurred by observing the cross section of the through hole after a thermal shock test in which 5 through holes were formed in the multilayer board and repeated at 260 ° C. for 10 seconds and 20 ° C. for 20 seconds Find out. Number of voids: 5 through holes are formed in the multilayer board,
Observe the cross section of the through hole and check the number of through holes with voids. Insulation characteristics: Measured according to JIS C6481. Thermal conductivity: Measured using "QTM-D3" manufactured by Kyoto Electronics.

From each table, it can be seen that the heat dissipation becomes good when the thickness of the metal foil forming the circuit of the inner layer circuit board is 100 μm or more. Further, it can be seen that in the examples according to the present invention, the effect of suppressing cracks and voids is also good. From a comparison between Examples 1 to 2 and 6 and Examples 7 to 8, it can be seen that when the content of the inorganic filler is 50 parts by weight or more based on 100 parts by weight of the resin, crack generation is further suppressed. From the comparison between Examples 5 and 9 and Example 4, it can be seen that generation of voids is further suppressed by setting the resin amount of the adhesive prepreg to 75% by weight or more. It can also be seen that when phenylaminosilane is used as the coupling agent in the glass nonwoven fabric binder, the insulating properties are improved (comparison between Example 3 and other examples).

[0018]

As described above, according to the method of the present invention, it is possible to manufacture a highly reliable multilayer circuit board which is excellent in heat dissipation and suppresses the generation of voids and cracks in the through hole wall. When the content of the inorganic filler in the resin of the adhesive prepreg is 50 parts by weight or more with respect to 100 parts by weight of the resin, the effect of suppressing the occurrence of cracks due to thermal stress becomes even greater. If the resin amount of the adhesive prepreg is 75% by weight or more, the effect of suppressing the generation of voids becomes even greater. When the glass non-woven fabric that is the base material of the adhesive prepreg is one in which phenylaminosilane is added to the binder that binds the glass fibers together, the moisture resistance of the multilayer board can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing a circuit pattern of an inner layer circuit board.

Claims (5)

[Claims] 1. In the manufacture of a multilayer board in which a metal foil to be a circuit of an inner layer circuit board and a circuit of a surface layer is heat-pressed through an adhesive prepreg to be integrated, a metal constituting at least one layer of a circuit of the inner layer circuit board. The adhesive prepreg, which has a foil thickness of 100 μm or more and is in contact with a circuit surface made of a metal foil having a thickness of 100 μm or more, uses a glass nonwoven fabric as a base material and an inorganic filler-containing thermosetting resin as an impregnating resin. A method for producing a multilayer board, characterized in that. 2. A thermosetting resin having an inorganic filler content of 100.
The method for producing a multilayer board according to claim 1, wherein the amount is 50 parts by weight or more with respect to parts by weight. 3. The resin amount (including the inorganic filler) of the adhesive prepreg that is in contact with the circuit surface composed of a metal foil of 100 μm or more is 75% by weight or more.
Or the method for producing a multilayer board according to item 2. 4. The method for producing a multilayer board according to claim 1, wherein the glass non-woven fabric contains a coupling agent in a binder that binds glass fibers together. . 5. The method for producing a multilayer board according to claim 4, wherein the coupling agent is phenylaminosilane.