JPH0637447A - Manufacture of multilayered printed-circuit board - Google Patents

Abstract

PURPOSE:To provide a heat-resistant, multilayered printed-circuit board enhanced in adhesion and causing no haloing by formation of copper sulfide and corrosion prevention instead of blackening. CONSTITUTION:A circuit pattern is formed on a two-sided metal-clad laminate having an epoxy-glass or polyimideglass base. The surface of the pattern, after roughened, is subjected to acid rinse and degreasing, and the laminate is immersed in a solution of a sulfur-metal salt and an alkaline substance; for example, a combination of potassium sulfide and sodium hydroxide or ammonium chloride. Inner layers are composed of copper sulfide, containing less than 10% oxygen and subjected to corrosion prevention with benzotriazole. The bonding sheets used are made of fluororesin, or semicured prepreg comprising fiberglass impregnated with resin such as epoxy or polyimide. The inner layers, bonding sheets and outer metal foil are integrally joined into a laminate, which serves as a reliable printed-circuit board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multilayer printed wiring board which is excellent in heat resistance and adhesion and has good workability.

[0002]

2. Description of the Related Art Recent developments in electronic equipment have been remarkable, and printed wiring boards used therein are required to be highly integrated.
In addition, the number of layers is increasing. The multilayer printed wiring board is manufactured by integrally forming a plurality of inner layer boards, prepregs and outer layer copper foils. The inner layer plate is subjected to an oxidation treatment called a blackening treatment in order to improve the adhesiveness with a prepreg used as a bonding sheet for the inner layer plate and the heat resistance of the adhered surface.

However, in a small-diameter through-hole, which is increasing with the increase in integration, blackened copper oxide is very soluble in hydrochloric acid, so that it is eroded by a plating solution containing hydrochloric acid to cause haloing. Due to the characteristics of the multilayer printed wiring board, haloing deteriorates reliability due to poor adhesion between layers, and therefore is often regarded as a failure in visual inspection. For this reason, currently, it is necessary to reduce the number of layers to be drilled and to reduce the drilling speed. In some cases, a double-sided roughened copper foil is used as the inner layer copper foil.

However, if the number of layers to be drilled is reduced or the speed is slowed down, the efficiency of drilling is reduced, especially in the case of small diameter (0.2φ to 0.4φ) holes, it is a normal (1.0φ) hole. There is a drawback that it takes 2 to 3 times longer than the above and the cost is high. Also, in the case of a double-sided roughened copper foil, there are drawbacks that the copper foil itself is expensive and that the surface is easily scratched in the forming step of the inner layer plate and the reprocessing cannot be performed at that time.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks and is excellent in heat resistance and adhesiveness, does not cause haloing, etc., and also results in drilling workability. It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board which is excellent in quality, can prevent an increase in cost, and has high productivity.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that copper sulfide formation and anticorrosion treatment are applied instead of the conventional blackening treatment to The present invention has been completed by discovering that the above object can be achieved.

That is, in the present invention, after selectively forming copper sulfide on the surface of a circuit pattern, an inner layer plate treated with a benzotriazole solution, a bonding sheet, and an outer layer metal foil are integrally laminated. And a method for manufacturing a multilayer printed wiring board.

The present invention will be described in detail below.

The inner layer plate used in the present invention is FR-4.
Double-sided metal-clad laminates of grades such as glass / epoxy and glass / polyimide are used. A circuit pattern is formed on this double-sided metal-clad laminate, and then, as a pretreatment, the surface is mechanically roughened with a buff or other abrasive, pickled and degreased. If necessary, soft etching can be performed. Copper sulfide is selectively formed on such a double-sided metal-copper clad laminate. As a method, it is possible to immerse it in an aqueous solution having a composition in which a combination of a sulfur-metal salt such as potassium sulfide and sodium hydroxide, potassium sulfide and ammonium chloride and an alkali source, which have been conventionally used for decoration and the like, is combined. Is. For example, the solution and treatment conditions of potassium sulfide and sodium hydroxide are as follows.

Potassium sulfide 5-30 g / l Sodium hydroxide 20-60 g / l Temperature 70-92 ° C. Time 30-300 seconds. However, depending on the conditions, an oxide layer is likely to be formed in the treated layer, so potassium sulfide 7-9 g / l sodium hydroxide 27-32 g / l temperature 78-82 ° C time 55-65 seconds is desirable. In addition, if the temperature is too high, or if it is left for a long time after the treatment, it will be oxidized from the surface, which is not preferable. The copper sulfide-formed laminated plate thus obtained is immediately subjected to anticorrosion treatment with a benzotriazole solution. As for the method of anticorrosion treatment, any method such as immersion in an aqueous solution of benzotriazole or spray treatment may be used. The concentration of the benzotriazole aqueous solution is not so thick and it is suitable to be about 0.1%, and soak for about 5 minutes.

In this way, copper sulfide is formed, and the surface of copper sulfide is subjected to antioxidative rust treatment. The oxygen content in copper sulfide is preferably 10% or less, more preferably 5% or less. If the oxygen content exceeds 10%, there is no effect on haloing resistance. Thus, the laminated plate which has been subjected to anticorrosion treatment after forming copper sulfide is used as an inner layer plate.

As the bonding sheet used in the present invention, a prepreg or a fluororesin sheet obtained by coating and impregnating glass fiber with epoxy resin or polyimide resin and semi-curing is used.

As the outer layer metal foil used in the present invention, a copper foil, an aluminum foil or the like, which is usually used for laminated plates / multilayer plates, can be used.

A multilayer printed wiring board can be manufactured by using the above-mentioned inner layer board, bonding sheet and outer layer metal foil, and laminating and integrally molding them by a conventional method.

[0015]

According to the method for manufacturing a multilayer printed wiring board of the present invention, chemically stable copper sulfide containing almost no copper oxide is formed on the metal surface of the inner layer plate, so that it is not corroded when immersed in the plating solution. , Hello does not occur. Further, since the double-sided metal foil is not used, there is no need to worry about an increase in the defective rate due to damage to the processing when processing the inner layer board.

[0016]

EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 2 Electrolytic copper foils having a thickness of 70 μm were superposed on both sides of FR-4 grade glass epoxy prepreg and heat-pressed to obtain inner layer plates having a thickness of 0.5 mm. Next, after forming a circuit on this inner layer plate by a conventional method, the surface is polished by a buff, washed with water, acid-washed with 5% hydrochloric acid (25 ° C) and washed with water, and then copper sulfide forming treatment is performed under the conditions shown in Table 1. And subjected to rust prevention treatment. This inner layer board, a prepreg of the same kind as the prepreg used for the inner layer board, and an outer layer copper foil were laminated and heat-pressed to produce a 4-layer printed wiring board with a board thickness of 1.6 mm.

Examples 3 to 4 Electrolyzed copper foils having a thickness of 35 μm were stacked on both sides of FR-4 grade glass epoxy prepreg and heat-pressed to obtain inner layer plates having a thickness of 1.1 mm. Next, after forming a circuit on this inner layer plate by a conventional method, the surface is polished by a buff, washed with water, acid-washed with 5% hydrochloric acid (25 ° C) and washed with water, and then copper sulfide forming treatment is performed under the conditions shown in Table 1. And subjected to rust prevention treatment. This inner layer board, a prepreg of the same kind as the prepreg used for the inner layer board, and an outer layer copper foil were laminated and heat-pressed to produce a 4-layer printed wiring board with a board thickness of 1.6 mm.

Comparative Example 1 A 70 μm thick electrolytic copper foil was placed on both sides of a FR-4 grade glass epoxy prepreg and heat-pressed to obtain an inner layer board having a thickness of 0.5 mm. Next, after forming a circuit on this inner layer plate by a conventional method, the surface was buffed and washed with water, and after being acid washed with 5% hydrochloric acid (25 ° C.), it was washed with water. This inner layer board, the prepreg of the same kind as the prepreg used for the inner layer board, and the outer layer copper foil are laminated, and heated and pressed to form a plate thickness.
A 1.6 mm 4-layer printed wiring board was manufactured.

Comparative Example 2 An electrolytic copper foil having a thickness of 35 μm was superposed on both sides of FR-4 grade glass epoxy prepreg and heat-pressed to obtain an inner layer plate having a thickness of 1.1 mm. Next, after forming a circuit on this inner layer plate by a conventional method, the surface was buffed and washed with water, and after being acid washed with 5% hydrochloric acid (25 ° C.), it was washed with water. This inner layer board, the prepreg of the same kind as the prepreg used for the inner layer board, and the outer layer copper foil are laminated, and heated and pressed to form a plate thickness.
A 1.6 mm 4-layer printed wiring board was manufactured.

Comparative Example 3 A four-layer printed wiring board was manufactured in the same manner as in Comparative Example 1 except that the pretreatment was followed by the black oxide (blackening) treatment as shown in Table 1 after the pretreatment.

Comparative Example 4 A four-layer printed wiring board was manufactured in the same manner as in Comparative Example 2 except that after the pretreatment, the black oxide (blackening) treatment as shown in Table 1 was carried out.

4 obtained in Examples 1 to 4 and Comparative Examples 1 to 4
With respect to the layer printed wiring board, the surface copper foil was removed by etching, and the heat resistance, inner layer peeling strength and haloing resistance were tested. The results are shown in Table 2. In all cases, the remarkable effect of the present invention could be confirmed.

[0024]

[Table 1]

[0025]

[Table 2] * 1: Cut the sample into 50 mm x 50 mm square, boil for 4 hours, and then 2
It was evaluated by immersing it in a solder bath at 60 ° C for 120 seconds and then for 30 seconds. ○: No abnormality, ×: Peeling off. * 2: A release paper was previously sandwiched under the remaining copper foil of 100 mm square or more inner layer foil, and after molding, it was used as a sample, and the peeling strength of this sample inner layer copper foil with a width of 10 mm was measured by a conventional method. * 3: The same sample as * 2 was floated in a solder bath at 260 ° C for 20 seconds and then the peel strength was measured. * 4: 0.4φ drill, rotation speed 72,000 rpm, feed rate
1000 holes were drilled at 1.4 m / min, each was dipped in 4N hydrochloric acid for a predetermined time, and peeling was evaluated. ○: None at all
△: Almost no, ×: Yes The samples of Comparative Examples 1 and 2 had already peeled off at the time of punching.

[0026]

As is apparent from the above description and Table 2, according to the method for manufacturing a multilayer printed wiring board of the present invention,
A multilayer printed wiring board having excellent solder heat resistance, adhesion, haloing resistance, and drill workability can be obtained. And since haloing does not occur at all, drilling and plating processes can be performed easily. As a result, the efficiency is improved, and an inexpensive and reliable multilayer printed wiring board can be obtained.

Claims (1)

[Claims] 1. An inner layer plate treated with a benzotriazole solution, a bonding sheet, and an outer layer metal foil are laminated and integrally formed after selectively forming copper sulfide on the surface of a circuit pattern. Manufacturing method of multilayer printed wiring board.