JPH09139575A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a precise printed wiring board superior in suppression on the exudation of adhesive into holes. SOLUTION: The through holes 4 are made in metallic foil with adhesive 3 and the adhesive face is stacked with a circuit board 5 which is previously prepared. A sheet 6 whose elastic modulus is less than that in the fusing point or softening point of insulating adhesive 2, in which insulating adhesive 2 can be dissolved with solvent or chemical and which plastically flows in a stacking layer is stacked on the circuit board 5. The board which is heated, pressurized, stacked, incorporated and stacked is cleaned by water, solvent or chemical and the sheet 6 which plastically flows is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lamination process for a multilayer printed wiring board having via holes.

[0002]

2. Description of the Related Art Generally, in order to increase the density of a printed wiring board, a method of increasing the number of wiring layers is generally employed.
Increasing the number of wiring layers inevitably increases the number of connection holes for electrical connection between the layers. Conventionally, since a through hole is used for this interlayer connection, if the through hole increases, the area of the through hole increases and the area for forming the wiring conductor decreases. There was a problem that the density could not be increased.

Therefore, a method of connecting layers between layers only where electrical connection is required has been developed. In a multilayer printed wiring board, a so-called interstitial via hole such as a through hole in an inner layer and a surface via hole connecting an outer layer and an inner layer is formed. Some have IVH). This IVH-containing multi-layer printed wiring board is effective not only for increasing the density, but also for improving wiring flexibility, improving electrical characteristics, and reducing wiring length. However, the conventional method complicates the manufacturing process. A method has been proposed which aims at further densification while simplifying the manufacturing process to reduce the cost.

Such via holes have been widely used in ceramic wiring boards for a long time, and were commonly used in ceramic wiring boards in which an insulating layer and a conductive layer are alternately formed, but a plastic wiring board. In the above, the alternating formation of the insulating layer and the conductive layer reduces the efficiency and is not generally performed.
However, with the recent development of electronic devices, the amount of wiring accommodated in a wiring board has increased remarkably, and a via hole has to be formed. As a proposal, there have been many methods for forming via holes in such a plastic wiring board. For example, JP-A-55-78598.
Japanese Patent Laid-Open No. 59-48996 discloses a method of alternately laminating processed double-sided substrates and prepregs, and Japanese Laid-Open Patent Publication No. 59-48996 discloses forming a hole in a double-sided copper-clad laminate and metallizing the inner wall of the hole.
A method is disclosed in which only one side of the copper foil is processed and laminated and integrated with an inner layer circuit board via a prepreg, a through hole is opened if necessary, the inner wall is metalized, and the outer layer circuit is processed. Such a method uses the technology of the conventional wiring board as it is, and although it is efficient, it cannot reduce the hole diameter, and to accommodate the current high-density wiring, Quite difficult.

Therefore, in recent years, in order to accommodate wiring of higher density, for example, as disclosed in Japanese Patent Laid-Open No. 63-119599, a copper foil surface of a copper foil having a protective metal foil is provided. As disclosed in Japanese Patent Laid-Open No. 1-37083, a method of laminating an adhesive sheet, performing outer shape processing by punching or router processing, and then stacking it on an outer layer material, an inner layer material, a prepreg, etc. , An outer layer base material having an adhesive layer formed on one side and a through hole provided at a desired position, and an inner layer base material on which a conductor pattern is formed face-to-face and laminated and bonded, and a conductor pattern on the inner layer base material in the through hole There has been proposed a method of connecting the electrodes by chemical plating.

Further, in Japanese Unexamined Patent Publication No. 5-191046, a perforated substrate is arranged in the uppermost layer, and an adhesive having a hole corresponding to the hole portion of the perforated substrate is provided between the perforated substrate and a substrate lower than the perforated substrate. In a method for manufacturing a multilayer printed wiring board in which an adhesive agent is sandwiched and heated and pressed to form a laminate, a thermoplastic resin sheet having heat resistance above the curing temperature of the adhesive begins to soften at a temperature lower than the melting temperature of the adhesive. The method of mounting is described.

[0007]

By the way, Japanese Patent Laid-Open No. Sho 63-63
In the method disclosed in JP-A-119599 and JP-A-1-37083, when the hole diameter is small, there is a problem that the adhesive seeps into the hole, and particularly, the hole diameter is smaller than 0.5 mm. That tendency is remarkable. Also,
In the method described in JP-A-5-191046, since holes are separately formed in the substrate and the adhesive, there is a problem that as the hole diameter decreases, the alignment accuracy of the holes decreases.

It is an object of the present invention to provide a method for efficiently producing a multilayer printed wiring board which is excellent in suppressing the exudation of the adhesive into the holes and has a high precision.

[0009]

According to the method for manufacturing a multilayer printed wiring board of the present invention, a through hole 4 is formed in an adhesive-attached metal foil 3 in which a semi-cured insulating adhesive 2 is provided on one side of a metal foil 1. Open
The adhesive surface is overlapped with the circuit board 5 prepared in advance, and the elastic modulus at the melting point or softening point of the insulating adhesive 2 is equal to or lower than the elastic modulus on the metal foil 1 of the adhesive-attached metal foil 3, and
Sheets 6 that are soluble in water, a solvent, or a chemical agent and that plastically flow during the lamination process are stacked, and heated and pressed to be laminated and integrated,
Thereafter, the laminated substrates are washed with water, a solvent or a chemical, the plastically flowing sheet 6 is removed, and plating is performed with or without formation of through holes to connect the layers,
It is characterized in that the outer layer conductor is processed to form an outer layer circuit.

Instead of the metal foil 1, a single-sided metal foil-clad laminate 11 can be used.

In this step of laminating and integrating, after heating to a temperature equal to or higher than the melting point or softening point of the plastically flowing sheet 6, the metal foil 3 with an adhesive or the insulating adhesive 2 of the laminated plate 31 with an adhesive is cured. Preferably.

The metal foil 1 used in the present invention may be of any type as long as it is used for a printed wiring board.
It is possible to use rolled copper foil, electrolytic copper foil, or the like that has been roughened in order to increase the adhesive strength with the insulating layer.

The semi-cured insulating adhesive 2 used in the present invention may be an epoxy adhesive, an acrylic adhesive, a polyimide adhesive, a polyamide adhesive, or the like. Alternatively, as a method for providing the semi-cured insulating adhesive 2 provided on one surface of the single-sided metal foil-clad laminate 11, a post-metering coating system such as a blade coater, a knife coater, a squeeze coater, a reverse roll coater, or a kiss roll coater is used. It can be achieved by applying and heating by a pre-weighing system coating method such as a cast coater, a spray coater, an extrusion coater. Further, a film obtained by film-forming the above-mentioned adhesive can be attached to the metal foil. Such an adhesive can be applied more than twice, or can be formed into two or more layers by using two or more film-formed adhesives.

As the plastically flowable sheet 6 used in the present invention, the elastic modulus at the melting point or the softening point of the insulating adhesive 2 of the adhesive-attached metal foil 3 or the adhesive-attached laminate 31 is the adhesive-attached metal. It is necessary that the elastic modulus of the insulating adhesive 2 of the foil 3 or the laminated plate 31 with an adhesive is equal to or lower than that, and it can be dissolved and removed with water, a solvent or a chemical. As the sheet 6 that plastically deforms and plastically flows as described above,
Examples of compounds that can be dissolved and removed with water, an acid or an alkaline aqueous solution include, for example, polymers having a hydroxyl group such as polyvinyl alcohol and polymers having a carboxyl group such as an acrylic acid copolymer and a methacrylic acid copolymer. , Polymers having sulfonic acid groups, amino groups, etc., ether type polymers such as polyethylene oxide, and polysaccharide type natural high molecular weight sugars. Vinyl polymers, aliphatic polyesters that can be dissolved and removed with a solvent. Alternatively, a thermoplastic resin sheet such as polyamide can be used. Here, when the elastic modulus of the plastically flowing sheet 6 at the melting point or softening point of the insulating adhesive 2 is higher than the elastic modulus of the insulating adhesive 2, the metal foil with adhesive during the laminating step. 3 or the through hole 4 formed in the laminated plate with adhesive 31 cannot be filled with the sheet 6 that plastically flows, and the adhesive in a semi-cured state flows inside the through hole 4 and the hole diameter is reduced. Resulting in. In the dismantling work after the laminating step, the plastically flowable sheet 6 may remain in the portion of the through hole 4 formed in the adhesive-attached metal foil 3 or the adhesive-attached laminate 31 so that the inner layer circuit remains as it is. If the plating for connecting the inner layer circuit and the outer layer circuit is incomplete, or if the inner layer circuit and the outer layer circuit are connected when the wiring board is completed, solder for mounting electronic components In the connection step, in the high temperature state where the solder melts, the remaining plastically flowing sheet 6 may be thermally expanded or thermally decomposed to break the connection portion, resulting in incomplete connection.

For this reason, in the present invention, the plastically flowable sheet 6 remaining in the portion of the through hole 4 is treated with water, a solvent or a chemical agent between the laminating step and the step of metallizing the inner wall of the through hole 4. A step of dissolving and removing is required. For example,
When the plastically flowable sheet 6 is made of a thermoplastic resin sheet such as a vinyl polymer, an aliphatic polyester or a polyamide which can be dissolved and removed by a solvent, an alcohol solvent, a ketone solvent or an ester solvent is used. For removal by dissolution, it is possible to immerse in these solvents or spray these solvents. Further, water, a polymer having a hydroxyl group such as polyvinyl alcohol, which can be dissolved and removed with an aqueous acid or alkali solution,
Polymers having carboxyl groups such as acrylic acid copolymers and methacrylic acid copolymers, polymers having sulfonic acid groups, amino groups, etc., ether polymers such as polyethylene oxide, natural polysaccharides of polysaccharides When using, it is also possible by immersing in these chemicals or spraying these chemicals. Furthermore, in order to accelerate dissolution and removal, heating or ultrasonic vibration can be applied. As such a solution, it is most preferable to use water, which is less likely to cause fire or chemical damage. In this case, a plastic flowable sheet 6 can be used.
For example, NOVON film R0390 (manufactured by Chisso Corporation, trade name) which is a water-soluble starch polymer, Soafil (manufactured by Mitsubishi Rayon Co., Ltd.), or flexine film (Daiichi Kogyo Co., Ltd.) which is a polyether polymer. Pharmaceuticals Co., Ltd., trade name) can be used.
Further, through holes may be provided in the substrate after the laminating step. The through hole is provided when a connection other than the inner layer circuit and the outer layer circuit connected by the through hole 4 is required, and the inner layer is metalized to connect the circuits of the necessary layers. is there. As the pretreatment for metallizing the inner wall of such a through hole, it can be performed in the same manner as the smear treatment of a normal multilayer printed wiring board, for example, using a well-known permanganate aqueous solution,
This is to dissolve and remove the resin facet in the through hole generated when drilling. The step of metallizing the through hole can be combined with the step of connecting the inner layer circuit and the outer layer circuit by the through hole 4, and the step of dissolving and removing the plastically flowing sheet 6 can also be combined with the smear treatment step. Is something that can be done. After this lamination step, at least the inner wall of the through hole 4 is metallized, the outer layer conductor and the inner layer circuit are electrically connected, and the outer layer conductor is processed to form the outer layer circuit. The metalization of the inner wall can also be performed by performing electroless plating and subsequent electrolytic plating, or by filling a conductive paste.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
A concrete description will be given according to the embodiment.

[0017]

【Example】

Example 1 As the metal foil 1, an electrolytic copper foil having a thickness of 18 μm was used, and in order to form the insulating adhesive 2 on the roughened surface, a polymer epoxy adhesive sheet AS-3000 (Hitachi Chemical Co., Ltd.) was used. Epoxy resin adhesive varnish used for product name) manufactured by Co., Ltd. is applied using a blade coater at 1
After drying for 0 minutes, as shown in FIG. 1A, a copper foil as an adhesive-attached metal foil 3 in a semi-cured state in which the insulating adhesive 2 had a thickness of 50 μm and a softening point of 75 ° C. was obtained. As shown in FIG. 1B, a through hole 4 having a diameter of 0.2 mm was formed in the copper foil as the adhesive-attached metal foil 3. As shown in FIG. 1C, an inner layer circuit conductor 51 is formed in advance, and an inner layer circuit conductor 51 is formed on the upper and lower sides of a 0.8 mm-thick glass-epoxy double-sided inner layer circuit board 5 whose surface is blackened. The through hole 4 is aligned and overlapped with the place where the circuit is connected, and further,
Above and below the plastic sheet 6 having a thickness of 10
A 0 μm water-soluble NOVON film R0390 (manufactured by Chisso Corporation, trade name) is stacked, and as shown in FIG. 1 (d), these are sandwiched by a stainless steel end plate 8 and pressure 2MP.
a, heating temperature 170 ° C., temperature rising rate 10 ° C./min, high temperature holding time 60 minutes, cooling rate −10 ° C./min, 10 t
Under pressure reduction of orr, press lamination is performed to integrate lamination,
As shown in FIG. 1E, the end plate 8 and the sheet 6 that plastically flows were disassembled. Further, through holes are formed in the laminated and integrated body, and then immersed in hot water at 60 ° C. for 10 minutes to dissolve and remove the plastically fluidized sheet 6 remaining in the holes to be the via holes of the substrate. Next, electroless copper plating and electrolytic copper plating are performed to obtain a plated metal layer having a thickness of 1
After forming a copper layer of 5 μm on the entire surface, an etching resist is formed, and the copper exposed from the etching resist is removed by etching to form a via hole, a through hole and an outer layer circuit as shown in FIG. 1 (f). And a multilayer printed wiring board.

Example 2 An electrolytic copper foil having a thickness of 18 μm was used as the metal foil 1, and one side of the insulating layer 12 of the glass cloth epoxy resin-impregnated laminate laminated on one side thereof was coated with a polymer as the insulating adhesive 2. The epoxy resin adhesive varnish used for the epoxy adhesive sheet AS-3000 (manufactured by Hitachi Chemical Co., Ltd.) is applied using a blade coater, and at 1
After drying for 0 minutes, as shown in FIG. 2A, a semi-cured adhesive-bonded laminate 31 having a thickness of the insulating adhesive 2 of 50 μm and a softening point of 75 ° C. was obtained. As shown in FIG. 2 (b), a through hole 4 having a diameter of 0.2 mm was formed in the adhesive-bonded laminate 31. As shown in FIG. 2C, the inner layer circuit 51 is previously formed.
Of the glass-epoxy double-sided inner layer circuit board 5 having a thickness of 0.8 mm, the surface of which is blackened, and the through holes 4 are aligned with the locations where the inner layer circuit conductor 51 is connected to the outer layer circuit. Then, water-soluble NOVON with a thickness of 100 μm, which is the sheet 6 that plastically flows above and below
Film R0390 (manufactured by Chisso Corporation, product name) is stacked, and as shown in FIG. 2 (d), these are sandwiched by a stainless steel end plate 8, pressure 2 MPa, heating temperature 170 ° C., heating rate 10 ° C./min. , High temperature holding time 60 minutes, cooling rate -1
Press lamination was performed under a reduced pressure of 10 torr under the condition of 0 ° C./min to laminate and integrate, and as shown in FIG. 2E, the end plate 8 and the sheet 6 that plastically flows were disassembled. Further, through holes are formed in the laminated and integrated body, and then immersed in hot water at 60 ° C. for 10 minutes to dissolve and remove the plastically fluidized sheet 6 remaining in the holes to be the via holes of the substrate. Next, perform electroless copper plating and electrolytic copper plating,
After forming a copper layer having a thickness of 15 μm as a plated metal layer on the entire surface, an etching resist is formed, and the copper exposed from the etching resist is removed by etching to form a via hole and a through hole as shown in FIG. A multilayer printed wiring board on which an outer layer circuit is formed.

COMPARATIVE EXAMPLE 1 An experiment was conducted except that a low density polyethylene sheet was used in place of the water-soluble NOVON film R0390 (trade name, manufactured by Chisso Corporation), which is the plastically flowable sheet 6 used in Examples 1 and 2. A multilayer printed wiring board was produced in the same manner as in the example.

Comparative Example 2 Instead of the copper foil which was the adhesive-attached metal foil 3 used in Example 1, a copper foil having through holes and an adhesive sheet having holes at the same positions were used.

The performance of the thus-prepared multilayer printed wiring board was evaluated as follows. Table 1 shows the results. (Initial failure in conduction) A DC voltage of 5 V was applied to the via hole portion of the multilayer printed wiring board to measure the connection resistance value. If the value of the connection resistance was 10 ³ Ω or more, it was judged that the conduction was poor. (Hot oil test) Multilayer printed wiring board at 260 ℃
Immersed in silicone oil for 10 seconds and then immersed in water at 20 ° C. for 60 seconds as one cycle, and the number of cycles when the value of the connection resistance increased by 10% from the initial connection resistance was measured. (Smear of Through Hole Connection) The cross section of the through hole was observed with a microscope. (Smear of Via Hole Connection) The cross section of the via hole was observed with a microscope.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, it is possible to efficiently manufacture a multilayer printed wiring board which is excellent in suppressing the exudation of the adhesive into the holes and which has good positional accuracy and excellent connection reliability. A method can be provided.

[Brief description of the drawings]

1A to 1F are cross-sectional views in each step for explaining an embodiment of the present invention.

2A to 2F are cross-sectional views in each step for explaining another embodiment of the present invention.

[Explanation of symbols]

1. Metal foil 11. Single-sided metal foil clad laminate 2. 2. Insulating adhesive Metal foil with adhesive 31. Laminated board with adhesive 4. Through hole 5. Circuit board 51. Inner layer circuit 6. Plastic flow sheet 8. Mirror plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Mamoru 1500 Ogawa, Shimodate, Ibaraki Pref., Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inventor ▲ Tsuru ▼ Yoshino, 1500 Ogawa, Shimodate, Ibaraki Hitachi Chemical Co., Ltd. Shimodate Research Institute Co., Ltd. (72) Inventor Kazunori Yamamoto 1500 Ogawa, Shimodate, Ibaraki Hitachi Chemical Co., Ltd. Shimodate Research Institute (72) Inventor Atsuyuki Takahashi Shimodate, Ibaraki 1500 Ogawa Hitachi Chemical Co., Ltd. Shimodate Research In-house

Claims (3)

[Claims] 1. A through-hole (4) is opened in a metal foil (3) with an adhesive in which a semi-cured insulating adhesive (2) is provided on one surface of the metal foil (1), and the adhesive surface is preliminarily prepared. Overlaid with the prepared circuit board (5), on the metal foil (1) of the adhesive-attached metal foil (3), it is not more than the elastic modulus at the melting point or softening point of the insulating adhesive (2), and Sheets (6) that can be dissolved in water, solvent or chemicals and that flow plastically in the lamination process are stacked, heated and pressed to integrate them, and then the laminated substrates are washed with water, solvent or chemicals, and plastic flow The sheet (6) is removed, plating is performed with or without formation of through holes to connect the layers, and the outer layer conductor is processed to form an outer layer circuit. Law. 2. A laminated board with an adhesive, wherein a semi-cured insulating adhesive (2) is provided on the insulating layer (12) side of a single-sided metal foil-clad laminated board (11).
A through hole (4) is opened in (31), the adhesive surface thereof is overlapped with the circuit board (5) prepared in advance, and the metal foil (1) of the adhesive-attached laminated board (31).
On top of that, the insulating adhesive (2) is below the melting point or elastic modulus at the softening point, and is soluble in water, a solvent or a chemical agent, a sheet that plastically flows in the laminating process (6), After laminating and integrating by heating and pressurizing, the laminated substrates are washed with water, solvent or chemicals, and the plastically flowable sheet (6) is removed, and plating is performed with or without forming through holes to connect the layers. And the outer layer conductor is processed to form an outer layer circuit. 3. In the step of laminating and integrating, after heating to a temperature equal to or higher than the melting point or the softening point of the plastically flowable sheet (6), the adhesive-attached metal foil (3) or the adhesive-attached laminate (31) is formed. The insulating adhesive (2) is cured, and the insulating adhesive (2) is cured.
The method for manufacturing a multilayer printed wiring board according to.