JPH06136687A - Base paper for electrical insulating laminate board - Google Patents

Abstract

PURPOSE:To obtain the subject base paper for electrical insulating laminate board useful as base paper for high-density printed-wiring board, having excellent dimensional stability, heat resistance and laminate characteristics in punchability, comprising bleached kraft paper having specific fiber flexibility degree and immersion heat. CONSTITUTION:Eucalyptus chips of South Africa growth as a raw material are subjected to kraft digesting in the presence of an alkali at 160 deg.C digesting temperature to give unbleached pulp having 9.1 potassium permanganate value (K value), which is bleached to give bleached kraft pulp. The bleached kraft pulp is used to give base paper having 135g/m<2> weight and 0.50g/cm<3> density, which is subjected to papermaking to give the objective base paper for electrical insulating laminate board composed of the bleached kraft pulp having <=15 fiber flexibility degree and <55J/g immersion heat. This base paper is impregnated with a phenol resin, dried to give prepreg having 52% resin impregnation ratio and eight sheets of the base paper are laminated to a copper foil with an adhesive and hot-pressed at 155 deg.C under 100kg/cm<2> for 60 minutes to give a one-side copper-clad laminate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-shaped paper base material used for an electrically insulating laminated sheet, which has excellent laminated sheet characteristics such as dimensional stability, heat resistance and punching workability. It relates to the base paper.

[0002]

2. Description of the Related Art A base paper for a laminated board is processed with a phenol resin, a polyester resin or the like and used as a printed wiring board in a wide range of fields such as consumer electronic devices and industrial electronic devices. With the miniaturization, weight reduction and high performance of electronic devices, the density of printed wiring boards is increasing year by year, and there is a demand for a base paper for laminated boards corresponding thereto. In particular, there is a strong demand for a base paper for laminated boards, which is excellent in dimensional stability, punching workability, heat resistance, electrical characteristics, etc., as a measure for higher density.

Currently, bleached kraft pulp mainly made from hardwood from Hokkaido is widely used as a base paper for laminated boards. The laminated sheet using this base paper is inferior in punching workability, heat resistance and electrical characteristics, and is not currently suitable as a base paper for high density printed wiring boards. Further, among the wood pulp, a large amount of cellulose, and a laminated board base paper using a cotton linter which is a dissolved pulp or a non-wood pulp in which the bending of the fibers is remarkable, when the laminated board is relatively good punching workability, Although it has heat resistance and electric characteristics, it has a large inferior dimensional stability as compared with a laminated board using bleached kraft pulp, and lacks suitability as a base paper for high density printed wiring boards.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a base paper for an electrically insulating laminated sheet, which is excellent in heat resistance and punching processability by using bleached kraft pulp without deteriorating the dimensional stability of the laminated sheet. Is.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have a deep relationship between the dimensional stability of a laminated board and the flexibility of pulp fibers, and the heat resistance and punching workability of the laminated board with the immersion heat of the base paper. As a result of repeated studies focused on this, the fiber bending degree was 1
It has been found that the object can be achieved by using a bleached kraft pulp having a heat of immersion of the base paper for laminated plate of 5 or less and less than 55 J / g. The fiber bending degree represents a form of pulp fiber, and a fiber having a straighter form has a better thermal dimensional stability of a laminated board. For example, the dimensional stability of a laminated board made of a base paper for a laminated board using a linter paper or a pulp containing a high amount of α-cellulose is inferior because the morphology of those fibers is generally in a bent state, and when formed into a sheet, a heat history It is thought that it is easy to change with respect to.

Immersion heat of a laminated board base paper means immersing a solid (here, laminated board base paper or raw material pulp) in a liquid,
The minute amount of heat generated at that time is measured, and the immersion heat represents the wettability (or affinity or adhesion) between the solid and the liquid. The heat of immersion of the wood fiber component in water is in the order of (large) hemicellulose>cellulose> lignin (small). Further, it is known that the heat resistance and punching workability of a laminated board are better as the cellulose content in the pulp is higher (Japanese Patent Publication No. 63-8885). In general, bleached kraft pulp is composed of cellulose and hemicellulose, with most of lignin removed during the cooking and bleaching steps. Therefore, the heat resistance and punching workability of the laminate are improved as the heat of immersion in water is smaller, the more cellulose is contained.

The method for measuring the fiber flexibility and immersion heat of the present invention will be described in detail below. Fiber Flexibility Measurement Method The fiber flexion is represented by the ratio of the actual length of one fiber to the shortest distance (straight line distance) connecting both ends of the fiber long axis, and is calculated by the following formula. Lt: actual fiber length Ls: linear distance connecting both ends of the fiber long axis

That is, a completely straight fiber has Lt = L
s, and the fiber bending degree becomes 0 (zero). Further, when both ends of the fiber are bent so that they are as close to each other as possible, the fiber bending degree becomes infinitely large. There is no particular limitation on the method for measuring the fiber bending degree, but as an example, randomly sampled fibers are enlarged and projected, and all the fibers (500 or more as the total number of fibers) that have been copied (reflected) are measured and the whole is measured. Find a number that represents.

Immersion heat measurement method Using a base paper for a laminated plate as a sample, about 0.2 g was filled in an ampoule having a volume of about 2 ml, and deaeration and drying was carried out at 105 ° C. for 3 hours as a pretreatment to obtain an immersion heat measurement sample. . The measuring device is a commercially available twin conduction type micro calorimeter (for example, Tokyo Riko
Measurement is performed using a product name of MMC-5111 manufactured by KK
Ion-exchange distilled water is used as a measurement solvent, and measurement is performed at 25 ° C. to obtain the heat quantity due to immersion. After measuring the sample, Joule heat is added so that its size and shape are almost the same as the exothermic curve at the time of measuring the sample, and the measured value is corrected.

The immersion heat of the base paper for laminated plates of the present invention is 55 J /
If it is more than g, heat resistance and punching workability of the laminated plate deteriorate, which is not preferable. As a method for making the heat of immersion less than 55 J / g, impurities such as hemicellulose are reinforced under strong alkaline conditions to enhance kraft cooking to dissolve or elute and remove, or to enhance alkali treatment in the bleaching process, or to perform strong alkali extraction. This can be achieved by carrying out a purification treatment. However, when the kraft cooking is strengthened or a strong refining process is performed, the hemicellulose content is reduced to 55 J / g.
Although it is possible to obtain a dipping heat of less than this, the cellulose is damaged by excessive cooking or bleaching treatment, and the fiber morphology is likely to change. Therefore, in order to secure dimensional stability, it is important to keep the fiber flexibility to 15 or less. That is, in order to obtain a base paper for an electrical insulating laminated board having excellent laminated board characteristics such as dimensional stability, heat resistance and punching workability, it is indispensable to have both properties of fiber bending degree and immersion heat. If one of the properties is not satisfied, the laminated plate which is the object of the present invention cannot be obtained.

As a means for obtaining a bleached kraft pulp having a fiber flexibility of 15 or less and a fiber flexibility of less than 55 J / g, as a result of various investigations, the cooking temperature was lowered by the method such as lowering the cooking temperature during the kraft cooking. It is effective to lower the H factor and increase the alkali addition rate. As a cooking condition, the alkali addition rate is 15% against chips
Above 23%, H factor is above 250 9
It is preferably less than 00. The cooking temperature may be in the range of 150 to 170 ° C. which is applied to general kraft cooking, but the lower the temperature, the less the disintegration of cellulose during cooking and the better the fiber flexibility. Furthermore, the cooking temperature can be lowered by using a tree species containing less hemicellulose as the pulp material. The H factor is an index of cooking conditions in which the cooking time and the cooking temperature are variable factors. (Sum of product of each cooking temperature and cooking time)

[0012]

EXAMPLES The effects of the present invention are shown below by examples.

Example 1 Using South African eucalyptus chips as a raw material, kraft cooking was carried out under the conditions shown in Table 1 to obtain unbleached pulp having a potassium permanganate value (K value) of 9.1. Bleaching kraft pulp (LBKP) obtained by bleaching this unbleached pulp was used to make a base paper for an electrically insulating laminate having a basis weight of 135 g / m ² and a density of 0.50 g / cm ³ . Commercially available phenol resin (manufactured by Showa Highpolymer Co., Ltd., trade name BLS-
3122) and then dried to prepare a prepreg having a resin impregnation rate (*) of 52%. Eight pieces of this prepreg and copper foil with adhesive (thickness 35 μm) are overlaid, 1
Thermoforming was performed under the conditions of 55 ° C. and 100 kg / cm ² for 60 minutes to obtain a single-sided copper-clad laminate having a plate thickness of 1.6 mm.

Example 2 Craft hardwood pulp was produced from Hokkaido hardwood chips under the conditions shown in Table 1 to obtain unbleached pulp having a K value of 12.8. Using LBKP obtained by bleaching this unbleached pulp, a base paper for an electrical insulating laminate having a basis weight of 135 g / m ² and a density of 0.50 g / cm ³ was produced. The obtained base paper for laminated board was treated in the same manner as in Example 1 to obtain a prepreg, and then a laminated board.

Comparative Example 1 Kraft cooking was performed under the conditions shown in Table 1 using hardwood chips from Hokkaido as a raw material to obtain unbleached pulp having a K value of 13.5. Using LBKP obtained by bleaching this unbleached pulp, a base paper for an electrical insulating laminate having a basis weight of 135 g / m ² and a density of 0.50 g / cm ³ was produced. The obtained base paper for laminated board was treated in the same manner as in Example 1 to obtain a prepreg, and then a laminated board.

Comparative Example 2 Using Hokkaido hardwood chips as a raw material, kraft cooking was carried out under the conditions shown in Table 1 to obtain unbleached pulp having a K value of 11.4. Using LBKP obtained by bleaching this unbleached pulp, a base paper for an electrical insulating laminate having a basis weight of 135 g / m ² and a density of 0.50 g / cm ³ was produced. The obtained base paper for laminated board was treated in the same manner as in Example 1 to obtain a prepreg, and then a laminated board.

[0017]

[Table 1]

Fiber bending degrees of Examples 1 and 2 and Comparative Examples 1 and 2, immersion heat of base paper for laminates and punching workability of laminates,
Thermal expansion coefficient as an index of solder heat resistance and dimensional stability
The measurement results of the shrinkage coefficient are shown in Table 2.

[0019]

[Table 2]

* 1 Punching workability: Die hole wall spacing is 0.8, 1.0, 1.2, 1.6 mm
The surface temperature of the laminated plate was 20 ° C, 35 ° C, 55 using a test die having a pair of round holes and a pair of square holes of 1 mm x 2 mm and a clearance of 0.05 mm on one side between the punch and the die. ℃
After punching, the surface, holes, and cuts after punching are judged according to ASTM D617, excellent, good,
The evaluation was made in four grades of good and bad.

* 2 Solder heat resistance: Judged according to JIS C6481. * 3 Thermal expansion coefficient / shrinkage coefficient (dimensional stability); Using a push rod type thermal dilatometer, the expansion is 50 ° C to 150 ° C under the conditions of a load of 5 g and a temperature rising rate of 5 ° C / min (cooling is allowed).
Cooling was performed in the temperature range of 150 ° C to 50 ° C. The evaluation is shown by the average value in the vertical and horizontal directions.

[0022]

As shown in Table 2, the quality of the laminates of Examples 1 and 2 using the laminate base paper of the present invention is excellent in punching workability and heat resistance, and further has good dimensional stability. Shows. The base paper for laminated board shown in Comparative Example 1 has a fiber bending degree of 15
Since it is below, the dimensional stability is good, but on the other hand, since the immersion heat is 55 J / g or more, the punching workability and heat resistance are poor and it cannot be used as a laminate. In addition, the base paper for laminated plate shown in Comparative Example 2 has a dipping heat of less than 55 J / g, and therefore has good punching workability and heat resistance, but on the other hand, since the fiber flexibility is more than 15, the dimensional stability is large. , Poor quality. As described above, the base paper for an electric insulating laminate of the present invention is excellent in punching workability, heat resistance and dimensional stability, and sufficiently satisfies the requirements for high-density wiring, and its industrial significance is extremely large.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location // C08L 61:04 8215-4J (72) Inventor Takashi Inori 1-30 Kamiochiai, Shinjuku-ku, Tokyo -6 Sanyo Kokusaku Pulp Co., Ltd. Product Development Laboratory

Claims (1)

[Claims] 1. A fiber bending degree of 15 or less and an immersion heat of 5
A base paper for an electrically insulating laminated board, which is made of bleached kraft pulp having an amount of less than 5 J / g.