JPH0841223A - Method for producing thermosetting resin laminate board - Google Patents

Abstract

PURPOSE:To obtain the paper-based laminate board excellent in silver migration resistance, enhanced the reliability, and useful for silver through-hole printed circuit boards by impregnating raw paper controlled in a specific raw paper density. CONSTITUTION:This laminate is obtained by impregnating (A) raw paper controlled in a raw paper density of 0.48-0.60g/cm<3> by adding a pressure to the raw paper in a wet state in a paper-making process (e.g. craft paper or linter paper in a raw paper density of 0.48-0.60g/cm<3>) with (B) a thermosetting resin such as a (flexibilizer-modified) phenolic resin, a (flexibilizer-modified) epoxy resin or a (flexibilizer-modified) melamine resin. The flexibilizer for modifying the component B is, e.g. a drying or semi-drying oil such as tung oil, tall fatty acid, cashew oil or linseed oil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a method of manufacturing a silver through-hole printed wiring board, in which a silver migration phenomenon which causes deterioration of reliability is less likely to occur (excellent silver migration resistance). It is a thing.

[0002]

2. Description of the Related Art Conventionally, a paper-based thermosetting resin laminated board is obtained by impregnating a base paper with a thermosetting resin compound varnish, laminating a plurality of the impregnated papers, and adhesive on one or both sides depending on the application. It is manufactured by stacking coated copper foils and then heat-pressing. It is well known that, after silver through-hole processing is applied to the laminated plate thus obtained, a silver transfer phenomenon occurs with time when a voltage is applied between the silver through-holes under high temperature and high humidity conditions. There is. In particular, in a place where the silver through-holes are close to each other, a silver migration phenomenon occurs so as to connect the through-holes inside the laminated plate, and eventually a short circuit occurs. In order to prevent the occurrence of the silver migration phenomenon inside such a laminated plate, the present inventors have filed Japanese Patent Application No. 5-469.
No. 15, Japanese Patent Application No. 5-48376, Japanese Patent Application No. 5-6977
No. 0, Japanese Patent Application No. 6-33938 and other methods have been used to increase the resin impregnation inside the paper fiber.

However, due to the development of the evaluation method as described in Japanese Patent Application No. 6-27789 and Japanese Patent Application No. 6-32678, there is a deviation in the impregnation of the resin into the paper fiber inside the laminated plate. It was found to be a major factor in the occurrence of the silver migration phenomenon.

[0004]

The present invention has been completed as a result of various studies based on the knowledge of such a silver migration phenomenon, and provides a method for producing a laminated plate in which the silver migration phenomenon is less likely to occur. To do.

[0005]

The present invention provides a base paper having a base paper density adjusted to 0.48 to 0.60 g / cm ³ by applying pressure while the base paper is wet during the papermaking process. The present invention relates to a method for producing a paper-based thermosetting resin laminated plate (hereinafter referred to as a laminated plate) in which a silver migration phenomenon is unlikely to occur by impregnating a thermosetting resin (hereinafter referred to as a resin).

The present invention will be described in detail below. The key to suppressing the occurrence of the silver migration phenomenon is how much resin can be impregnated inside the base paper fiber. By taking measures against the resin, the ability to impregnate the resin inside the base paper fiber is enhanced. It is possible. As a matter of course, when the resin is completely permeated and filled between the raw paper fibers and the resin and the raw paper fibers are in firm contact with each other, the impregnation ability of the resin into the raw paper fibers is most efficiently exhibited.

[0007] Conventionally, it has been considered that the base paper used for the laminated board is preferably low in density and swells in the thickness direction during the coating step in order to enhance the penetration of the resin between the base paper fibers. In such a raw paper, the void volume existing between the raw paper fibers is large, and the void volume existing between the raw paper fibers becomes excessive with respect to the required amount of the resin impregnated into the raw paper. For this reason, the penetration of the resin into the fibers of the base paper becomes non-uniform, and uneven distribution of the resin impregnation inside the fibers of the base paper occurs.

In order to eliminate such uneven distribution of resin impregnation inside the base paper fibers, there is a method of increasing the base paper density to reduce the void volume between the base paper fibers, but by suppressing the swelling of the base paper in the thickness direction. It is possible to reduce the void volume between the fibers of the base paper during the resin impregnation step.

Since the constituent units of cellulose and the like are bonded to each other by hydrogen bonds, the base paper fiber has its original form when wet with a resin or solvent (including water) even if it is deformed under stress in a dry state. It has the property of restoring to.
On the other hand, when deformed by stress in the wet state,
Because the hydrogen bond is cleaved, it can easily accept deformation,
During drying, hydrogen bonds are formed according to the deformation,
After that, even if it gets wet with resin or solvent, the power to restore the original form is lost.

Therefore, by using a base paper whose base paper density is adjusted by applying pressure in a wet state of the base paper during the paper making process, the base paper swells in the thickness direction during the resin impregnation process, and Since the increase of the void volume is suppressed and the appropriate voids are maintained, the resin is uniformly permeated into the fiber of the base paper.

Therefore, the inventor of the present invention adjusts the density of the base paper by applying pressure while the base paper is wet, and the method of applying pressure in the dry state is not used or is used only for auxiliary adjustment. By impregnating the known base paper with a resin, we succeeded in developing a laminate that is less likely to cause the silver migration phenomenon than the base paper in which the base paper density was adjusted by applying pressure to the base paper in the conventional dry state. It is a thing. The base paper density here is measured based on JIS P-8118. In addition, compared to the conventional laminated board, it is possible to stably suppress the silver migration phenomenon in a wider range of base paper density, and even if there is a change in the base paper density due to an unexpected cause, a stable laminated board is supplied. It becomes possible.

The method for producing a laminated plate of the present invention can be applied regardless of the impregnation method such as the one-step impregnation method and the two-step impregnation method. Examples of the base paper used in the present invention include kraft paper and linter paper. As the resin, phenol resin, epoxy resin, unsaturated polyester resin, melamine resin, or the like, or these, tung oil, tall fatty acid,
Modified with cashew oil, linseed oil, castor oil, linolenic oil, linole oil, epoxidized vegetable oil and other drying oils, semi-drying oils, glycerides of these, epoxidized polybutadiene, polyethylene glycol, polyester, polyether and other flexibilizing agents. Those mentioned above are listed, and these may be used alone or in combination.

[0013]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 The density of the base paper was 0.48 g / cm ³ by applying pressure in the wet state during the paper making process of the base paper.
The base paper prepared as above was impregnated with a resol-type phenol resin having a tung oil modification rate of 35% so that the amount of adhesion was 50% to obtain a prepreg a. Eight prepregs and copper foil with an adhesive were superposed on both front and back surfaces of the prepreg and heat-pressed to obtain a laminate A having a thickness of 1.6 mm.

Example 2 By applying pressure in a wet state during the paper making process of the base paper, the density of the base paper is 0.52 g / cm ^3.
The prepreg b was obtained by impregnating the base paper prepared as above with a resol-type phenol resin having a tung oil modification rate of 35% so as to have an adhesion amount of 50%. Eight sheets of this prepreg and copper foil with an adhesive were superposed on both front and back surfaces of the prepreg and heat-pressed to obtain a laminated board B having a board thickness of 1.6 mm.

Example 3 The density of the base paper was 0.56 g / cm ³ by applying pressure in the wet state during the paper making process of the base paper.
The base paper prepared as above was impregnated with a resole-type phenol resin having a tung oil modification rate of 35% so that the amount of adhesion was 50% to obtain a prepreg c. Eight sheets of this prepreg and copper foil with an adhesive were superposed on the front and back surfaces of the prepreg and heat-pressed to obtain a laminate C having a thickness of 1.6 mm.

Comparative Example 1 A stencil oil modification rate of 35% was applied to a stencil paper having a stencil density adjusted to 0.48 g / cm ³ in a normal dry state.
Was impregnated with the resol-type phenol resin of No. 1 so as to have an adhesion amount of 50% to obtain a prepreg d. Eight prepregs and copper foil with an adhesive were superposed on both front and back surfaces of the prepreg and heat-pressed to obtain a laminate D having a thickness of 1.6 mm.

Comparative Example 2 A stencil oil modification rate of 35% was applied to a stencil paper whose stencil density was adjusted to 0.52 g / cm ³ in a normal dry state.
Was impregnated with the resol-type phenol resin of (1) so as to have an adhesion amount of 50% to obtain a prepreg e. Eight sheets of this prepreg and copper foil with an adhesive were superposed on the front and back surfaces of the prepreg and heat-pressed to obtain a laminate E having a thickness of 1.6 mm.

Comparative Example 3 A stencil oil modification ratio of 35% was applied to a stencil paper whose stencil density was adjusted to 0.56 g / cm ³ in a normal dry state.
Was impregnated with the resol-type phenol resin of No. 1 so as to have an adhesion amount of 50% to obtain a prepreg f. Eight prepregs and copper foil with an adhesive were superposed on both front and back surfaces of the prepreg and heat-pressed to obtain a laminate F having a thickness of 1.6 mm.

Table 1 shows the characteristics of each laminate obtained by the above method.

[Table 1]

(Test method for silver migration resistance) Land diameter 1.2 m
m, through hole diameter 0.5 mm, 10 silver through holes
Create a test pattern in which two circuits with 0 holes are arranged adjacent to each other so that the distance between the centers of the through holes is 1.5 mm. Under the conditions of a temperature of 40 ° C. and a humidity of 93% RH, the through holes are formed. A voltage (50 VDC) is continuously applied for a predetermined time, and the insulation resistance between through holes is measured thereafter.

[0022]

As is clear from the above results, the laminated sheet obtained by the present invention has extremely excellent silver migration resistance.

Claims (2)

[Claims] 1. The base paper density is 0.48 to by applying pressure while the base paper is wet during the paper making process.
A method for producing a paper-based thermosetting resin laminate, which comprises impregnating a base paper adjusted to 0.60 g / cm ³ with a thermosetting resin. 2. The method for producing a laminated board according to claim 1, wherein the thermosetting resin is a phenol resin.