JPH0135512B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a circuit board, and its purpose is to have a conductive part and an insulating part on the same plane, a smooth mirror-like surface, and further have good heat resistance, moisture resistance, impact resistance, etc. Our goal is to provide superior circuit boards. Conventionally, many proposals have been made regarding methods of forming conductive patterns on circuit boards. For example, as shown in FIG. 1a, an organic adhesive 2 is applied onto an electrically insulating substrate 3 made of paper-phenolic resin or glass fiber-epoxy resin, and a metal foil 1 made of copper or the like is bonded. Alternatively, as shown in FIG. 1b, a metal foil 1 made of copper or the like is hot-press molded onto an electrically insulating substrate 3 made of glass fiber-diallyl phthalate resin prepreg, and the prepreg is cured and the metal foil is bonded at the same time. In any case, there is a method of manufacturing a so-called copper-clad laminate and then removing unnecessary portions of the metal foil by etching or the like. On the other hand, there is also a method in which, instead of removing unnecessary parts of the metal foil, a metal such as copper is deposited only on the necessary parts by plating or the like to form a conductive pattern. However, as shown in FIG. 2, the circuit boards obtained by these methods all have a conductive pattern 4 protruding from an electrically insulating substrate 3, and the conductive part and the insulating part are on the same plane. It is impossible to do as above. In order to make this possible, various proposals have been made, such as forming a conductive pattern on a release plate using a printing method and then inverting and pasting it onto an electrically insulating substrate. There are restrictions on conductive materials, making it extremely difficult to build a circuit with low resistance, and considering the thickness of the printed film, it is generally impossible to run a large current;
It was also difficult to obtain fine patterns. Moreover, circuit boards using these conventional general-purpose resins as the shaft fat for electrically insulating boards have poor toughness, so the resulting circuit boards may crack, chip, or
Or, there is an inconvenience that may cause a crack.
Furthermore, the heat resistance and moisture resistance were also far from satisfactory. Taking the above points into consideration, the inventors of the present invention took advantage of the excellent features of copper-clad laminates, while making sure that the conductive and insulating parts are on the same plane, that the board itself has a smooth mirror-like surface, and that the board itself is heat resistant. As a result of various studies aimed at obtaining a circuit board with excellent physical properties such as moisture resistance and impact resistance, the present applicant has developed a novel allyl resin that has been previously developed by the applicant as a material for electrically insulating boards. It was possible to achieve the purpose. That is, the present invention includes a step of forming a conductive pattern by removing unnecessary portions of a copper layer electrodeposited on an aluminum base material, and placing the conductive pattern on an electrically insulating substrate so that the pattern surface is in contact with the insulating substrate. The process of laminating the laminate into a laminate by thermoforming, and the process of dissolving and removing the aluminum base material in the laminate by alkali treatment, provide heat resistance, moisture resistance, and A method for manufacturing a circuit board with excellent impact resistance, etc., characterized in that the following terephthalic acid diallyl ester copolymer resin is used as the electrically insulating resin used for the electrically insulating board. The terephthalic acid diallyl ester copolymer resin refers to a copolymer resin of terephthalic acid diallyl ester and an aromatic hydrocarbon having at least one hydrogen atom at the benzyl position represented by the following formula (). (However, in the above formula (), R ¹ and R ² each represent a group selected from the group consisting of a hydrogen atom and a lower alkyl group, and n = an integer of 1 to 3.) Explain the invention. Figure 3a
~FIG. 4 shows one embodiment of the present invention. Figure 3a
A copper layer 6 is electrodeposited on an aluminum base material 5 (hereinafter referred to as aluminum-coated copper foil).
Copper and aluminum are strongly bonded, and the copper layer is formed by electrodeposition, so the interface has good smoothness. The surface of the copper layer 6 may be subjected to an appropriate treatment in order to increase the adhesive strength with the electrically insulating substrate. In FIG. 3B, a conductive pattern 4 is formed on an aluminum base material 5 by removing unnecessary portions of the copper layer using an etching solution that does not attack aluminum using various well-known methods. Figure 3c
3 shows a state in which an electrically insulating substrate 3 made of an electrically insulating terephthalic acid diallyl ester copolymer resin and the conductive pattern shown in FIG. Pattern 4 is embedded in an electrically insulating substrate. The fourth material is the one in which the aluminum base material 5 in FIG. 3c is removed using an alkaline aluminum etching solution.
In the figure, the conductive pattern 4 is embedded in the electrically insulating substrate 3, the conductive part and the insulating part are on the same plane, and the circuit board has a smooth mirror-like surface. Furthermore, according to the present invention, not only a conductive path using a copper layer but also a resistor element 7 is provided in a necessary part of a conductive pattern 4 formed on an aluminum base material 5, as shown in FIG. After assembling by printing or other methods, the aluminum base material is removed after lamination with an electrically insulating substrate as described above and hot-press molding, as shown in Figure 6. Elements such as conductive parts and resistors It is thus possible to produce circuit boards in which the sections and the insulating sections are all coplanar. The thickness of the aluminum base material for aluminum-coated copper foil can be selected taking into consideration ease of handling and removal of aluminum after forming the conductive pattern, but it is 30~
A value of about 100μ is easiest to use in the present invention.
The thickness of the copper layer depends on the intended use of the circuit board. For example, to form a fine pattern such as passing three lines between the pins of a 2.54mm IC, a 5μ
While it is advantageous to use a thin copper layer, such as less undercutting due to etching, a thicker copper layer is advantageous for purposes such as passing large currents. Various known methods can be applied to form a conductive pattern on aluminum-coated copper foil. For example, in order not to attack the aluminum base material, a solvent-soluble resist agent is uniformly applied onto the copper layer, and after temporary curing, ultraviolet rays are irradiated through a pattern mask, and unnecessary resist agent is removed by development. do. Next, it is immersed in an etching solution consisting of, for example, ammonium persulfate solution to dissolve the non-resist portions of the copper layer, and then the resist agent is peeled off to form a conductive pattern. As the material used for the electrically insulating substrate, in order to embed the conductive pattern obtained above, it is recommended to use a terephthalic acid diallyl ester copolymer resin newly developed by the applicant as an electrically insulating resin, and the resin itself is It is advantageous because it has excellent electrical properties, heat resistance, high temperature and humidity resistance, bending strength, etc., as well as excellent impact resistance. The above-mentioned terephthalic acid diallyl ester copolymer resin refers to a copolymer obtained by polymerizing terephthalic acid diallyl ester and an aromatic hydrocarbon in the presence of an organic peroxide and an azo compound. A terephthalic acid diallyl ester copolymer as described in 1. is preferable as the resin used for the electrically insulating substrate. That is, the following formula () However, in the above formula (), R ¹ and R ² each represent a group selected from the group consisting of a hydrogen atom and a lower alkyl group, and n = an integer of 1 to 3. An aromatic hydrocarbon having at least one hydrogen atom at the benzylic position represented by the following formula () A copolymer resin with terephthalic acid diallyl ester represented by (a) one monomer unit of formula () at the end of the monomer unit of formula (), and an allyl group of the monomer unit of formula () at the benzyl position and its It has a carbon-carbon bonded structure with *C and/or *C. Furthermore, (b) the number of monomer units of the formula () in the carbon-carbon bond molecular chain portion formed by the allyl group of the monomer unit of the formula () of the copolymer resin is 3 to 11, preferably 3 to 10; It is a copolymer resin with certain structural characteristics. Furthermore, copolymer resins having the following properties are desirable. (c) Iodine value measured by Wijs method: 40~
85. (d) True specific gravity at 25°C is 1.20-1.25. (e) Softening range: approximately 50 to approximately 120°C. (f) 50% by weight methyl ethyl ketone solution viscosity 80~
300cps (30℃). (g) The polystyrene equivalent number average molecular weight (n) measured by GPC (gel permeation chromatography) method is 4,000 to 10,000, the weight average molecular weight (w) is 70,000 to 200,000, and the relationship between n and Mw is The molecular weight distribution expressed as the ratio w/n is
10-40. (h) The Brabender melt viscosity measured with a Brabender plastograph is 250 to 2600 m·g, and the processing time is 5 to 65 minutes. The details of the manufacturing method of the terephthalic acid diallyl ester copolymer resin are described in Japanese Patent Application No. 189981/1989 (Japanese Unexamined Patent Publication No. 80409/1989) filed by the present applicant. In the present invention, the above terephthalic acid diallyl ester copolymer resin is combined with paper, glass cloth, glass mat, glass nonwoven fabric, synthetic fiber cloth, synthetic fiber nonwoven fabric, etc. to produce an electrically insulating substrate with excellent impact resistance and other properties. Can be used. Of course, the copolymer resin can also be used after being modified with other resins, such as diallyl phthalate resin or unsaturated polyester resin. If a particularly flexible circuit board is required, a plastic sheet or film such as the above-mentioned terephthalic acid diallyl ester copolymer resin-glass fiber or synthetic fiber laminate may be used. Alternatively, it is also possible to use not only a laminate but also a molding material to form an electrically insulating substrate.
The content of resin in these electrically insulating substrates is suitably in the range of 40 to 70% by weight. If the patterned surface of the conductive pattern formed on the aluminum-coated copper foil is in contact with the material selected from the various electrical insulating substrates mentioned above, and the material is laminated and hot-pressed, an aluminum base material as shown in Figure 3c is obtained. A circuit board with Molding conditions are usually a temperature of 100
~190°C, pressure 5~1000Kg/ ^cm2 . In order to remove the aluminum base material, etching may be performed using an alkaline solution, for example, an etching solution containing 50 g of sodium hydroxide or 1 g of sodium glyconate. After removing the aluminum layer, it is washed with water and soaked in a weak copper etching agent such as 20% ammonium persulfate to remove surface dirt, resulting in a circuit board as shown in Figure 4 or Figure 6. . In order to protect the surface of the circuit and maintain solderability, the conductive pattern may be coated with gold, tin/nickel, tin/lead, tin plating, or the like. By effectively utilizing the method of the present invention, it is possible to manufacture multilayer boards as well as circuit boards having conductive patterns on one and both sides. According to the method of the present invention, as the aluminum-coated copper foil,
Since each process such as resist coating, development, and etching can be performed in advance, electrically insulating substrates containing organic substances are less likely to be exposed to etching solutions, other chemicals, moisture, heat, etc., and are less likely to be damaged. One of the important features is that it has the advantage of being less susceptible to damage, and that a high-precision circuit board with excellent dimensional stability can be obtained. The circuit board thus obtained has a conductive part and an insulating part on the same plane, a smooth mirror-like surface, and the circuit board itself has heat resistance, moisture resistance, impact resistance, etc. Therefore, it is particularly suitable for applications such as sliding on circuit boards. It is further advantageous to improve the wear resistance by adding an anti-wear agent or the like to the electrically insulating substrate. The circuit board obtained by the method of the present invention can of course be used as an excellent high-performance printed wiring board, but also can be used to incorporate multi-polar connectors, resistors, etc. For example, if a small motor commutator or carbon electrode is incorporated into various composite elements, potentiometers, encoders, sensors, etc., it can become a power supply circuit, and many other fields that take advantage of the sliding properties due to the smoothness of the surface can be used. be. Production of terephthalic acid diallyl ester copolymer resin. Inner diameter 600 mm equipped with turbine blade type variable stirrer, double pipe type supply nozzle for monomer and catalyst supply, nitrogen purge port, leak valve, sampling port, thermometer and pressure gauge. , with jacket of internal volume 120
A polymerization tank made of SUS304 was used. The double-tube supply nozzle for monomer and catalyst supply is installed below the liquid level in the body of the polymerization layer, and the inner diameter of the outer tube is set to 1.5 mm before entering the polymerization tank to minimize the residence time in the supply piping. I made it shorter. Three such nozzles were installed in preparation for nozzle blockage. A sampling port was also installed in the body of the polymerization tank, making it possible to take samples of the liquid phase using the internal pressure during the polymerization reaction. An oil rotary vacuum pump and a nitrogen cylinder were connected to the nitrogen purge port so that they could be switched as needed. Charge 60 kg of xylene to the above polymerization layer as shown in Table 1 below, reduce the pressure with a vacuum pump at room temperature, and return to normal pressure with nitrogen gas three times to replace the air in the tank with nitrogen. After that, the pressure was reduced again and the polymerization tank was sealed. start the stirrer
While stirring at 240 RPM, steam was passed through the jacket to raise the temperature to 140°C. The stirring speed was increased to 720 RPM, and terephthalic acid diallyl ester was added from the outer pipe of the double pipe nozzle at the specified speed, and at the same time, di-tert-butyl peroxide (DTBPO) and xylene were added at a molar ratio of 0.5:1. were mixed in advance and supplied to the polymerization tank at a predetermined speed using a pump with a discharge pressure of 70 kg/cm ² . During this time, the steam was adjusted so that the temperature of the polymerization tank was maintained at 140°C. Note that the formula () diallyl terephthalate (DAT) to be supplied was cooled to 15°C, the mixture of di-tert-butyl peroxide and xylene was cooled to 5°C, and the piping leading to the polymerization tank was kept cool. The polymerization tank pressure was 0.3 to 2 Kg/cm ² G. Once the specified amounts of diallyl terephthalate, xylene, and di-tert-butyl peroxide have been supplied, the steam is turned off and the stirring speed is reduced to 240 RPM.
Then, cooling water was passed through the jacket to cool it. After cooling to around room temperature, the leak valve was opened to return to normal pressure, and the polymerization reaction was completed. For the polymerization reaction, samples were appropriately taken from the sampling port, and the reaction was monitored by refractive index and GPC. The feed rates and amounts of diallyl terephthalate, xylene, and di-tert-butyl peroxide are shown in Table 1 below. The volatile components of the polymerization reaction solution obtained above were distilled off using a thin film evaporator, and the ratio of unreacted xylene in the evaporation residue to the total of copolymer resin and unreacted diallyl terephthalate was determined. , 0.3 in weight:
1, and then the evaporation residue was added dropwise to a stirring tank containing methanol in an amount 5 times the weight of the supplied diallyl terephthalate and stirred to precipitate a copolymer resin. The precipitated copolymer resin was thoroughly washed with the same amount of methanol, filtered, dried, and pulverized to obtain a powdered copolymer resin. Table 1 shows the yield and physical properties of the copolymer resin.

【table】

[Table] In Table 1 above, (1) is the polystyrene equivalent value measured by the gel vermiaction chromatography method, using a "150CGPC" device manufactured by Waters. For (2), a light transmission type automatic melting point measuring device "PF61" manufactured by Mettler was used. (3) is the value measured by Brabender Plastograph manufactured by Brabender (Germany). Kneading chamber capacity 50c.c., rotor model W50H, sample 50
g+zinc stearate 0.5g, kneading chamber temperature 130
℃, the kneading resistance at rotor rotation speed 22 RPM
The processing was continued until reaching 5000 m·g, and from the torque curve of the recording paper, the lowest torque value was taken as the Brabender melt viscosity, and the time from the end of sample loading to 5000 m·g was taken as the processing time. Example <Formation of conductive pattern on copper foil with aluminum> Aluminum copper foil (“UTC foil 40E” manufactured by Mitsui Metal Mining Co., Ltd.)
A solvent-soluble resist agent was uniformly applied to the surface of the copper layer (No. 9), and after drying, ultraviolet rays were irradiated through a pattern mask, and unnecessary resist agent was removed with a solvent. Next, it was immersed in an etching solution consisting of ammonium persulfate solution to dissolve the copper layer in non-resist areas, and then the resist agent was removed. <Preparation of electrically insulating substrate> 80 parts by weight of the terephthalic acid diallyl ester copolymer resin produced above, 20 parts by weight of unsaturated polyester,
2 parts by weight of dicumyl peroxide, methyl ethyl ketone
An impregnated varnish was prepared by mixing 100 parts by weight, which was impregnated into a plain-woven glass cloth (basis weight 202 g/m ² ) treated with methacrylic silane.
It was dried at ℃ for 30 minutes to obtain a prepreg. The resin content in the prepreg was 45.5% by weight. Here,
The unsaturated polyester used was obtained by dehydrating and condensing 0.5 mol of phthalic anhydride, 0.5 mol of maleic anhydride, and 1 mol of propylene glycol using a melting method.
28.0, a polyester with a softening temperature of 80°C. <Molding of circuit board> The patterned surface of the conductive pattern on the aluminum-coated copper foil was laminated so that it was in contact with the electrically insulating substrate prepreg. Six prepregs were used. Molding was carried out for 30 minutes at a hot platen temperature of 165° C. and a pressure of 50 kg/cm ² to obtain a laminate. <Removal of aluminum base material> Add an etching solution containing 50 g of sodium hydroxide and 1 g of sodium gluconate at a temperature of 70°C.
immerse the above laminate in water to remove the aluminum layer,
After thorough washing with water, it was immersed in a 20% ammonium persulfate solution for 10 seconds to obtain a circuit board. The resulting circuit board has conductive parts and insulating parts on the same plane.
It had a smooth mirror-like surface. Further, the heat resistance test (200°C x 1 hr) conducted on this circuit board based on JISC6481 was good, and the water absorption rate was 0.1% or less in the water absorption test (E-24/50+D-24/30). Incidentally, instead of the resin containing terephthalic acid diallyl ester copolymer resin used for the electric insulating substrate of the circuit board, diallyl phthalate resin alone or a combination of this resin and unsaturated polyester resin (1:
1) In the heat resistance test of the circuit boards obtained in the same manner as above except that a mixture was used, blistering occurred in all cases, and in the water absorption test, each had a water supply rate of 0.1% or more.

[Brief explanation of drawings]

1a and 1b are sectional views of a conventional metal foil-clad laminate, FIG. 2 is a sectional view of a conventional circuit board, and 3a to 3c and 4 are sectional views of a conventional circuit board. 3a to 3c are sectional views of each process, FIG. 4 is a sectional view of a circuit board, and FIGS.
The figures show other embodiments of the present invention, with FIG. 5 being a sectional view of the process, and FIG. 6 being a sectional view of the circuit board. 1: Metal foil, 2: Adhesive, 3: Electrical insulating substrate,
4: Conductive pattern, 5: Aluminum base material, 6:
Copper layer, 7: resistor element.

Claims (1)

[Claims] 1. A step of forming a conductive pattern by removing unnecessary portions of a copper layer electrodeposited on an aluminum base material,
A step of laminating the conductive pattern on an electrically insulating substrate so that the pattern surface is in contact with the insulating substrate to obtain a laminate by hot pressing, and a step of dissolving and removing the aluminum base material in the laminate by an alkali treatment. In a method for manufacturing a circuit board with excellent heat resistance, moisture resistance, impact resistance, etc., in which a conductive part and an insulating part are on the same plane, the following terephthalic acid diallyl ester is used as an electrically insulating resin for the electrically insulating board. A method for manufacturing a circuit board characterized by using a copolymer resin. The terephthalic acid diallyl ester copolymer resin refers to a copolymer resin of terephthalic acid diallyl ester and an aromatic hydrocarbon having at least one hydrogen atom at the benzyl position represented by the following formula (). However, in the above formula (), R ¹ and R ² each represent a group selected from the group consisting of a hydrogen atom and a lower alkyl group, and n = an integer of 1 to 3.