JPH0538789A - Manufacture of prepreg and laminated board for silver through-hole printed wiring board - Google Patents

Abstract

PURPOSE:To manufacture a laminated board having excellent silver migration resistance. CONSTITUTION:Kraft paper is impregnated with a water-soluble melamine-phenol resin and a flame retardant as required, dried at a temperature higher than a conventional method or a prolonged time, dried until volatiles reach 1-4%, preferably 2-3%, and impregnated with a phenol resin and dried, thus manufacturing a prepreg. The prepreg is laminated, thus preparing a laminated board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, when formed into a laminated board,
The present invention relates to a method for producing a paper-based prepreg having high insulation resistance and excellent punching workability, and a silver through-hole printed wiring board laminate having good silver migration resistance.

[0002]

2. Description of the Related Art Silver paste through-holes are being developed for laminated sheets using a paper base material. A silver through-hole printed wiring board is required to have excellent silver migration resistance. In order to improve the silver migration resistance, the moisture resistance may be improved so that the insulation resistance does not deteriorate even if moisture is absorbed.

Conventionally, a paper base material is impregnated with a water-soluble phenol resin or a water-soluble melamine resin as an undercoat resin and dried, and then a general thermosetting resin is impregnated and dried to improve moisture resistance. Was there.

[0004]

The drying after impregnating the undercoat resin is generally performed so that the volatile content is about 5% or more. This is because if it is too dry, the affinity with the topcoat resin will deteriorate. However, in recent years, the wiring density has increased, and higher silver migration resistance has been required. It is an object of the present invention to provide a method for producing a prepreg for producing a laminate having excellent silver migration resistance.

[0005]

Means for Solving the Problems The present inventors have made various studies on the relationship between the degree of drying of the undercoat resin and the insulation resistance in the manufacturing process of the prepreg. As a result, it is obtained by drying in the undercoating step at a higher temperature than before or for a long time so that the volatile content becomes 1 to 4%, preferably 2 to 3%, and then impregnating and drying the thermosetting resin for topcoating. It was found that the laminated plate obtained by heating and pressing the prepreg is extremely excellent in silver migration resistance. Here, the volatile matter is defined as follows. Volatile content = [(weight before drying-weight after drying) / weight before drying]
× 100 Drying: A sample dried by impregnation with a resin varnish is dried in a hot air dryer at 160 ° C for 5 minutes to reduce the volatile content to 1% or less, impairing the impregnation of the topcoat resin, and rather reducing the moisture resistance and punching processability. Become.

Examples of the undercoat resin include water-soluble phenol resin, melamine resin, and melamine / phenol co-condensation resin, with melamine / phenol co-condensation resin being most preferred. The melamine content of the melamine / phenol co-condensation resin must be 15% or more by weight. 20% to 25
% Is preferred.

In order to improve the flame retardancy of the laminate, a flame retardant is added. The flame retardant may be blended with either the undercoat resin or the overcoat resin. As the flame retardant, dibutoxyphosphinylpropylamide, dimethyl-N, N-bis (2-
Hydroxyethyl) aminomethylphosphonate, dipropyl-N, N-bis (2-hydroxyethyl) aminomethylphosphonate, diethyl-N, N-bis (2-hydroxyethyl) aminomethylphosphonate and the like can be mentioned. The amount of the flame retardant compounded is 0.5 parts to 50 parts, preferably 2 parts to 20 parts with respect to 100 parts of the resin (the same applies hereafter by weight).
Part. If the amount is less than 0.5 part, the flame retardant effect is insufficient, and if it exceeds 50 parts, the electrical characteristics are deteriorated.

Examples of the thermosetting resin for top coating include phenol resin, melamine resin and unsaturated polyester resin. Particularly, a dry oil-modified phenol resin is preferable because it has good punching workability. As the drying oil, tung oil, dehydrated castor oil, deer oil, etc. are used, and as the phenols, phenol, metacresol, paracresol, orthocresol, isopropylphenol, paratertiarybutylphenol, paraisopropenylphenol oligomer, nonylphenol, bisphenol A. Etc. are used.

[0009]

[Function] By drying the volatile matter to 1 to 4%,
The undercoat resin and the paper base material are chemically bonded to each other, and it becomes difficult for the fibers of the paper to absorb moisture. As a result, it is considered that the migration of silver ions is hindered and the silver migration resistance is improved.

[0010]

【Example】

Example 1 Melamine / phenol co-condensation resin (melamine amount 40%)
A resin varnish containing 50 parts (parts by weight, hereinafter the same) and 50 parts of a phenol resin is used as a kraft base material with a resin content of 17-20
%, And dried at 175 ° C. for 2 minutes. The volatile content was 2.7%. Next, 100 parts of a tung oil-modified phenolic resin was impregnated with a varnish containing 28 parts of triphenyl phosphate and 20 parts of tetrabromobisphenol A diglycidyl ether so that the resin adhesion amount was 50 to 54%, and then dried. It was a prepreg.

Example 2 Melamine / phenol co-condensation resin (melamine content 40%)
Diethyl-containing 50 parts (by weight) and 50 parts of phenol resin
A kraft base material was impregnated with a resin varnish containing 4 parts of N, N-bis (2-hydroxyethyl) aminomethylphosphonate so that the resin content was 17 to 20%.
And dried for 2 minutes. The volatile content was 2.8%. Thereafter, a prepreg was prepared in the same manner as in Example 1.

Example 3 Melamine / phenol co-condensation resin (melamine content 40%)
4 parts of dibutoxyphosphinyl propylamide in 100 parts
Part of resin varnish is mixed with the kraft base material
It was impregnated to ˜20% and dried at 175 ° C. for 2 minutes. The volatile matter was 2.6%. Thereafter, a prepreg was prepared in the same manner as in Example 1.

Comparative Example Melamine / phenol co-condensation resin (melamine content 40%)
Diethyl-containing 50 parts (by weight) and 50 parts of phenol resin
A kraft base material was impregnated with a resin varnish containing 4 parts of N, N-bis (2-hydroxyethyl) aminomethylphosphonate so that the resin content was 17 to 20%, and the temperature was 150 ° C.
And dried for 3 minutes. The volatile content was 5.8%. Less than,
A prepreg was prepared in the same manner as in Example 1.

Eight prepregs obtained as described above were combined with a copper foil with an adhesive to obtain 170 ° C. and 10 MPa.
By heating and pressurizing, a double-sided copper clad laminate having a thickness of 1.6 mm was manufactured. The characteristics of this copper clad laminate are shown in Table 1.

[0015]

[Table 1]

Test Method Silver Migration Resistance Hole pitch 2.0 mm, land diameter 1.5 mm, hole diameter 0.
Insulation resistance between circuits after processing for 2000 hours at an applied voltage of 50 V, a relative humidity of 90% RH, and a silver migration test pattern of 2 circuits of 7 mm and 90 holes continuously. Punching workability Punching with a hole pitch of 2.0 mm and a hole diameter of 0.7 mm was performed, and the occurrence of peeled whiteness was evaluated.

[0017]

According to the present invention, the impregnation with the undercoat resin is followed by drying so as to have a volatile content of 1 to 4% and then impregnation with the overcoat resin, so that the silver migration resistance is improved. It also has excellent punching workability.

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Claims (4)

[Claims] 1. A method for producing a prepreg, characterized in that a paper base material is impregnated with an undercoat resin varnish, dried to a volatile content of 1 to 4%, and then impregnated with an overcoat thermosetting resin varnish. .. 2. The method for producing a prepreg according to claim 2, wherein the undercoat resin is a melamine / phenol co-condensation resin. 3. The method for producing a prepreg according to claim 1, wherein the thermosetting resin for top coating is a drying oil-modified phenol resin. 4. A laminate for a silver through-hole printed wiring board, which is obtained by stacking a predetermined number of prepregs obtained by the method according to claim 1, 2 or 3 and heating and pressing.