JPH06256546A - Production of laminated board - Google Patents

Abstract

PURPOSE:To provide a paper substrate thermosetting resin laminated board excellent in silver transfer resistance by swelling a paper substrate into a larger thickness than its original thickness and simultaneously impregnating the swollen paper substrate with a resin until reaching the inner parts of the paper fibers. CONSTITUTION:This method for producing the objective laminated board is characterized by swelling a paper substrate such as craft paper or linter paper into a thickness larger >=10% than its original thickness and simultaneously impregnating the swollen paper substrate with a polar solvent (e.g. water, an alcohol) and a thermosetting resin (e.g. a phenol resin, epoxy resin, unsaturated polyester resin) until reaching the inner parts of the paper fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper base thermosetting resin laminated plate (hereinafter referred to as a laminated plate) in which a silver migration phenomenon is less likely to occur (hereinafter referred to as "excellent silver migration resistance"). ) Is provided.

[0002]

2. Description of the Related Art Conventionally, a laminated board is prepared by impregnating a varnish containing a thermosetting resin compound into a kraft paper or a linter paper, laminating a plurality of the impregnated papers, and copper with an adhesive on one or both sides depending on the application. It is manufactured by stacking foils and then heat-pressing. The laminated plate thus obtained shows a migration phenomenon of silver over time when a voltage is applied between two silver electrodes (silver jumpers, silver through holes, etc.) formed on the laminated plate under temperature and humidity conditions. It is well known to occur.
In recent years, the trend toward lighter, thinner, shorter, and smaller electronic products requires higher density of printed circuit wiring boards, and the pitch between silver through holes is 2.5.
It has been narrowed down to ~ 2.0 mm, and now even a 1.5 mm pitch is about to be put to practical use. Therefore, a short circuit due to the migration phenomenon of silver is likely to occur, and in order to secure the reliability of the printed circuit wiring board, there is an increasing demand for a laminated board having more excellent silver migration resistance.

It is known that the silver migration phenomenon in a laminated plate occurs by the following mechanism. ^{Ag⇔Ag + + e - Ag + +} OH - ⇔AgOH (1) 2AgOH⇔Ag 2 O + H 2 O (2) Ag 2 O + H 2 O⇔2AgOH⇔2Ag + + 2OH - (3) Thus, ionization of silver main factor Therefore, it is indispensable that moisture penetrates into the laminated plate. Further, the elution of ionic impurities into the invaded water deteriorates the electrical characteristics of the laminated plate, particularly promotes the ionization of silver, and significantly reduces the resistance to silver migration. For this reason, the method of improving the moisture resistance of the laminate by making the resin hydrophobic or improving the impregnation of the resin by two-stage impregnation or the ionization of silver by adding an ion collector to the resin Methods have been adopted to suppress this.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a laminate having excellent silver migration resistance.

[0005]

Means for Solving the Problems The present invention is obtained by impregnating a resin while impregnating the paper base material with the resin swelling in the thickness direction by 10% or more in the resin impregnation step so that the resin penetrates into the fibers of the paper. By using the resin-impregnated paper base material, it is possible to obtain a laminated plate having excellent silver migration resistance. Hereinafter, the present invention will be described in detail. The silver migration phenomenon occurs inside paper fibers in the laminate due to moisture absorption. Therefore, it is possible to suppress the silver migration phenomenon by impregnating the inside of the paper fiber with the resin to make it difficult to absorb moisture.

The inventors of the present invention have found that the main component of paper fiber is cellulose having a large amount of alcoholic hydroxyl groups, and the alcoholic hydroxyl groups adsorb polar solvent molecules and finally allow the polar solvent molecules to penetrate into the inside of the paper fibers. Paying attention to the fact that the paper fiber itself swells, by selecting and adding an appropriate polar solvent and water-soluble thermosetting resin combination into the varnish, the paper fiber swells during the impregnation step, and specifically By swelling the thickness of the base material by 10% or more and impregnating the resin with the polar solvent into the inside of the paper fiber, the silver migration resistance of the laminate was remarkably improved. The method 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, and particularly when applied to the primary treatment of the two-step impregnation method, a great effect can be obtained.

The method for measuring the thickness of the paper base material swollen in the impregnation step here is as follows. That is, when the paper base material is inserted into a thickness measuring gauge adjusted so that the load applied to the paper base material is 0, a sufficient amount of varnish is dropped on the paper base material, and the same time as the impregnation time during the manufacturing process has elapsed. The thickness of the paper base material is measured. The paper base material used in the present invention includes kraft paper, linter paper, and the like, and the polar solvent is water,
There are alcohols. Further, as the thermosetting resin used in the present invention, phenol resin, epoxy resin,
Unsaturated polyester resin, melamine resin, or tung oil, tall fatty acid, cashew oil, linseed oil, castor oil, linolenic oil, linole oil, epoxidized vegetable oil and other drying oils, semi-drying oils, glycerides of these, epoxidation Examples thereof include those modified with a flexibilizing agent such as polybutadiene, polyethylene glycol, polyester and polyether, and these may be used alone or in combination.

[0008]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto. Example 1 A paper base was prepared by primary treatment using a primary treatment varnish consisting of 90 parts by weight of water and 10 parts by weight of a water-soluble low molecular weight phenolic resin varnish (solid content 50% by weight) so that the impregnation time was 25 seconds. Swell the material 30% in the thickness direction,
Then, a prepreg A was obtained by coating and impregnating with a dry oil-modified phenol resin varnish (solid content: 50% by weight) so that the resin amount became 50% by weight. Example 2 Paper base material by primary treatment using a primary treatment varnish consisting of 60 parts by weight of water, 30 parts by weight of methanol and 10 parts by weight of the water-soluble low-molecular weight phenolic resin varnish so that the impregnation time is 25 seconds. Was swelled by 23% in the thickness direction, and then coated and impregnated with the dry oil-modified phenolic resin varnish so that the resin amount was 50% by weight to obtain a prepreg B.

Example 3 Water 60 parts by weight, methanol 3
0 parts by weight of the water-soluble low molecular weight phenolic resin varnish 1
Impregnation time 20 with a primary treatment varnish consisting of 0 parts by weight
The paper base material is swelled by 18% in the thickness direction by a primary treatment for 10 seconds, and then coated and impregnated with the dry oil-modified phenolic resin varnish so that the resin amount becomes 50% by weight to obtain a prepreg C. It was <Example 4> Paper base material by primary treatment using a primary treatment varnish consisting of 60 parts by weight of water, 30 parts by weight of methanol, and 10 parts by weight of the water-soluble low-molecular weight phenolic resin varnish so that the impregnation time is 15 seconds. Was swelled by 14% in the thickness direction, and then coated and impregnated with the dry oil-modified phenolic resin varnish so that the resin amount was 50% by weight to obtain a prepreg D.

<Example 5> 10 parts by weight of water and 20 parts by weight of the water-soluble low-molecular-weight varnish were added to the drying oil-modified phenol resin varnish to swell the paper base material by 10%, and the resin amount became 50% by weight. Thus, coating and impregnation were carried out to obtain a prepreg E. Comparative Example 1 A prepreg F was obtained by coating and impregnating a paper base material with the dry oil-modified phenol resin varnish so that the resin amount was 50% by weight.

Eight pieces of each prepreg obtained as described above and a copper foil with an adhesive are set as a set and heat-pressed to obtain four kinds of laminated plates A, B, C having a thickness of 1.6 mm. D,
E and F were obtained. Table 1 shows the characteristics of the laminated plate thus obtained.

[0012]

(Test method) Silver migration resistance Two circuits in which 100 silver through-holes having a land diameter of 1.5 mm and a through-hole diameter of 0.7 mm are continuously connected to each other and the pitch between the through-holes is 2.0 mm. A test pattern was formed so as to be adjacent to each other. Using this test pattern, the insulation resistance between circuits was measured after 1000 hours of treatment under the conditions of an applied voltage of 50 VDC, a temperature of 40 ° C. and a relative humidity of 93%.

[0014]

As is clear from the above results, the laminate according to the present invention has extremely excellent resistance to silver migration.

Claims (1)

[Claims] 1. A thermosetting resin for a paper base material, characterized in that, in the step of impregnating a paper base material with a resin, the resin penetrates into the fibers of the paper base material while swelling the thickness of the paper base material by 10% or more. Laminated board manufacturing method.