JPS61174796A - Manufacture of multilayer circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a multilayer circuit board having circuits in its inner layers, in which through-holes can be formed by punching.

Conventional technology In recent years, there has been a strong demand for higher density and higher performance for printed circuit boards (on the other hand, price competition is fierce, and especially for multilayer circuit boards, the processing cost ratio is high, so reducing costs has become a major issue. ing.

Since electrical reliability is required for ordinary multilayer circuit boards, glass cloth-based epoxy resin is used, and the thickness is 0.
It is formed by stacking two or more single-sided or double-sided circuit boards with a thickness of 1 to 1.0 mm with an adhesive prepreg (glass cloth base epoxy resin) interposed therebetween and bonding them under heat. After opening these multilayer circuits, through-hole plating is applied.

However, since this drilling condition is related to the electrical reliability of the through-hole plating portion, it is necessary to set conditions that will prevent cracks and peeling from occurring in the hole portion and its surroundings. This type of drilling work takes time and increases processing costs, going against the trend of unit price reductions that have been increasingly requested in recent years.

Problems to be Solved by the Invention As mentioned above, in the case of multilayer circuit boards, since electrical reliability is required, epoxy resins based on glass cloth are usually used. The material is hard (drilling is used. In order to improve the efficiency of drilling work, 0, 8 to 1.
If an attempt is made to obtain a 2φ hole by punching, cracks will occur between the layers.

On the other hand, in the case of the additive method in which circuit processing is performed by electroless plating using a laminate containing a sensitizer, holes may be punched by punching, but the target substrate is paper-based epoxy resin or Since it is a paper-based phenolic resin and is opaque, it is disadvantageous for finding voids, which are considered to be serious defects in multilayer circuit boards.

The present invention solves these drawbacks by providing an inexpensive multilayer circuit board that has transparency to the extent that cracks and voids inside the layers can be easily detected and that allows through-holes to be formed by punching.

Means for solving the problem, that is, the present invention is characterized in that a glass nonwoven fabric with a unit weight of 30 to 150 g/m2 is used as a base material in the production of a multilayer board with a circuit provided in the inner layer.

As a result, through-hole plating holes can be formed by punching if the thickness is 1.2 mm or less without significantly changing the electrical reliability compared to the case of glass cloth substrates, and high-quality through-hole plating can be formed using the normal through-hole plating process. High-quality through-hole reliability can be obtained.

Additionally, this circuit board is translucent, making it easy to detect cracks and peeling within the layers.

As a glass non-woven fabric, the unit weight is 30g/m2~150
It is necessary to use a material in the range of g/m2. If the unit weight of the glass nonwoven fabric is less than 30g 7m2, the tensile strength will be weak and the base material will break during the resin coating process, making it impossible to coat.If the unit weight exceeds 150g 7m2, the coating will not dry. The solvent impregnated inside the base material during the process cannot be sufficiently scattered and removed, resulting in voids when it is made into a multilayer circuit board.

Example In the present invention, if high-speed steel is used as the material of the punching pin and about 5KD-12 is used as the material of the mold, the thickness is 1.2 mm.
Until now, it is possible to provide a multilayer circuit board in which through holes can be formed by punching.

Of course, a glass nonwoven fabric base material is also used for the adhesive prepreg used to join each glabella of the circuit board from the viewpoint of punching processing, but the recommended amount of resin to be impregnated into the glass nonwoven fabric base material is 50 to 8596. I can do it. Furthermore, the glass nonwoven fabric is not only made of glass fibers, but also contains a mixture of cellulose fibers and the like.

Next, examples of the present invention will be described.

Example 1 (1) 80 parts by weight of bisphenol-type epoxy resin (manufactured by Sumitomo Chemical, trade name ESA-001) and 20 parts by weight of flexible epoxy resin (manufactured by Shell Chemical, trade name EP-872) Acetone was added to a mixture of 4 parts by weight of dicyandiamide and 0.3 parts by weight of 2-ethyl-4-methylimidazole to prepare a face.

(2) This face is impregnated with cellulose fiber-mixed glass nonwoven with a unit weight of 100 g/m'' that has been pretreated with polymethylolated phenol, and heated and dried to prepare prepreg A (resin ft 5096) and adhesive prepreg B ( resin f
f16596) was obtained.

(3) 35% on each side of these two sheets of prepreg A
and made a double-sided circuit board.

(4) Prepreg B between the two circuit boards obtained in (3) above
One sheet was sandwiched and heated to obtain a 1.1 mm thick multilayer circuit board.

In order to confirm the reliability of through-hole plating on the above circuit board,
Using a die (bottle material: high-speed steel, die material: 5KD-12) capable of punching out the through-hole portion at once, punching was performed with an 80'ff hydraulic press at a punching temperature of 50°C. This was subjected to through-hole plating using a conventional method (plating thickness: 25 to 35 μm), and a pattern for through-hole plating reliability testing (110×115 mm, number of holes: 293) was obtained.

Comparative Example 1 Three double-sided circuit boards were used in Example 1, and a six-layer circuit board with a thickness of 1.5 mm was obtained in the same manner.

Using this, punching of through holes was attempted using the same mold as in Example 1.

Comparative Example 2 (1) A glass cloth with a thickness of 0119 mm pretreated with epoxy silane was impregnated with the same fabric as in Example 1,
Prepreg C (+1 fat content: 45%) was obtained by heating and drying, and adhesive prepreg D (resin content: 55%) was produced in the same manner using glass cloth with a thickness of 0.10 mm.

(2) Next, a double-sided circuit board was obtained in the same manner as in Example-1,
Furthermore, a four-layer circuit board was produced using two of these sheets. An attempt was made to punch through holes on this circuit board using the same mold as in Example 1.

Comparative Example 3 In Example 1, through holes were formed by drilling (drilling conditions: 2 rotations 55.00 rpm, feed rate 0.0
5rev, three stacked multilayer circuit boards (0.9φ carbide drill), and a through-hole plating reliability test pattern were prepared.

Table 1 shows the punching workability of each of the above laminates.

=--knee □ Further, FIG. 1 shows the test results of through-hole plating reliability of Example 1 and Comparative Example 3. This reliability test is 260
A cycle of immersion in silicone oil at 5 seconds at 20 degrees Celsius and 20 seconds at 20 degrees Celsius was repeated as one cycle, and changes over time in through-hole conduction resistance were measured. The through hole diameter is 1 mm.

Effects of the Invention As is clear from Table 1, the conventional product cracks during punching and is unusable, but the present invention has a good appearance and its effects are remarkable.

Furthermore, the reliability of through-hole plating is equivalent to that of drilling as shown in FIG. 1, and it can be used sufficiently as a multilayer circuit board.

Note that the thickness of the multilayer circuit board must be limited even in the configuration of the present invention because if it becomes thick, peeling will occur during punching.

[Brief explanation of the drawing]

FIG. 1 is a curve diagram showing changes in conduction resistance in a reliability test of through-hole conduction resistance.

Claims (1)

[Claims] A method for manufacturing a multilayer circuit board, characterized in that a glass nonwoven fabric having a unit weight of 30 to 150 g/m^2 is used as a base material in manufacturing a multilayer circuit board with a circuit provided on the inner layer.