JPH09209298A - Base paper for electrical insulating laminated board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a base paper for laminated board suitable for the production of an electrical insulating laminated board, excellent in silver migration resistance and dimensional stability. SOLUTION: This base paper for an electrical insulating laminated board is produced by adding a zirconyl compound to a base paper composed mainly of cellulose fiber. For example, the base paper is produced by impregnating an aqueous solution of zirconyl ammonium carbonate in a base paper composed mainly of cellulose fiber and drying the product. The zirconium content of the base paper is preferably about 0.2-1.5% in bone dry state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated board base paper used for an electrically insulating laminated board, and more particularly to a laminated board base paper used for producing a laminated board having good dimensional stability and silver migration resistance.

[0002]

BACKGROUND OF THE INVENTION Ordinary laminates, especially electrically insulating laminates,
Manufactured by impregnating laminated board base paper with a thermosetting resin such as phenol resin or epoxy resin, heating and drying it into a semi-cured resin prepreg, stacking multiple prepregs and thermoforming with metal foil. To be done. Such a laminated plate is relatively inexpensive and almost satisfies the performance required for use in ordinary electric or electronic devices, and is therefore widely used mainly for household electric appliances.

However, due to the recent lighter, thinner, shorter, and smaller electric products, the packaging density of electric parts has increased, and the conductor patterns of printed wiring boards have become finer. Moreover,
Even in printed wiring boards using paper as a base material, the conductor patterns have become more and more double-sided, and silver through holes have been used for the purpose of electrical connection between the front and back. For this reason,
In addition to the workability, dimensional stability, and punchability of laminated plates, deterioration of electrical insulation due to the phenomenon of silver migration becomes a problem, and there is a demand for improvement in silver migration prevention performance (hereinafter referred to as silver migration resistance). It's getting tougher. Conventionally, the pulp used for laminated board base paper is unbeaten bleached kraft pulp (L
BKP) is generally used, but depending on the application, softwood bleached kraft pulp may be blended to increase the strength of laminated board base paper, or unbleached pulp may be blended for the purpose of cost reduction. In some cases, sulfite pulp (SP) is used for whitening. Such pulp is produced by a known paper machine, and the density of the base paper obtained is as low as 0.45 to 0.55 g / cm ³ .

In order to improve the silver migration resistance of the printed wiring board, the characteristics required for the base paper are that there are few residual ions in the base paper that contribute to the ionization of silver and the precipitation as metallic silver, and the thermosetting property. Examples include good resin impregnation and low hygroscopicity. As a method for solving the above problems, a method using a resin varnish containing an inorganic ion exchanger (JP-A-2-133442 and JP-A-5162245) is known, but a laminated board base paper is used. In the case of the paper-based phenolic resin laminated board prepared above, since the laminated board base paper is manufactured from pulp fibers, the above-mentioned method allows the inorganic ion exchanger to take time to sufficiently remove the impurity ions in the pulp. Therefore, it was not a fundamental solution and the silver migration resistance was not sufficient. Further, in Japanese Patent Laid-Open No. 5-162245, an inorganic ion exchanger layer is provided on the surface of the laminated plate so that the influence of residual ions in the base paper does not affect the metal foil. No effect can be obtained for suppressing the migration between them. In addition,
In 63-1452 publication, as an ion removal filter from various solutions, it is designed to carry an inorganic ion exchanger between pulp fibers, in this method, a large particle size inorganic ion exchanger particles, Alternatively, since inorganic ion exchanger particles that have undergone secondary agglomeration in the wet papermaking raw material are present in the paper base material, poor phenol varnish impregnation and poor heat resistance after molding may occur, so it is not easy to adopt. Can not.

On the other hand, in order to improve the electrical properties of the laminate, a method of increasing the α-cellulose content (JP-A-60-7)
9952 gazette) has been proposed, a method of increasing the α-cellulose content is to perform a high degree of bleaching with a known bleaching agent sandwiching an alkali refining and alkali extraction step, or by heating steam prior to cooking. It takes a means of performing pre-hydrolysis or refining cold alkali in the latter stage, and in such a case, if the α-cellulose content is attempted to be significantly improved, the bending ratio of the fiber becomes large and the dimension of the laminated plate is increased. It has the drawback of deteriorating stability and warpage. Further, it is not intended to improve the silver migration resistance.

It is known that when linter pulp having a high α-cellulose content is used, the insulation resistance is improved, but since the fibers of linter pulp are remarkably bent, the dimensional stability and the laminar stability of the laminate are improved. It has the drawback of poor warpage, and since linter pulp is made from cottonseed, the raw material supply is unstable and the price is expensive and fluctuating, which makes it difficult to adopt. On the other hand, modification of the impregnated thermosetting resin has been devised to improve dimensional stability and silver migration resistance, but other laminated sheet properties may deteriorate, and paper base materials are used. In the case of the phenolic resin laminated plate which is used, there is a strong dependence on the essential characteristics of the base paper, and further improvement of the base paper is required.

[0007]

DISCLOSURE OF THE INVENTION In view of the above situation, the present inventors have studied various methods for suppressing silver migration of a printed wiring board without impairing the dimensional stability, and as a result, a laminate containing a zirconyl compound was obtained. The present inventors have found that a laminated sheet using a board base paper is excellent in dimensional stability and also excellent in silver migration resistance, and completed the present invention. An object of the present invention is to provide a method for producing a laminated board base paper suitable for producing a laminated board having good dimensional stability and silver migration resistance.

[0008]

[Means for Solving the Problems] Conventionally, the use of an aqueous zirconyl compound solution in the art has been as a water-proofing agent for a coating layer in coated paper, or as a pitch control agent in the case of using uncoated paper as a raw material. Only an aqueous solution of zirconyl ammonium carbonate is used, and it is not used as an additive to the laminated base paper.
However, the present inventors have found that a laminated plate excellent in dimensional stability and silver migration resistance can be obtained by using a laminated plate base paper obtained by containing an aqueous zirconyl compound solution and then drying.

The present invention includes the following aspects. [1] An electrically insulating laminated board base paper obtained by incorporating a zirconyl compound into a base paper mainly composed of cellulose fibers.

[2] The electrically insulating laminated board base paper according to [1], which is obtained by adding a zirconyl ammonium carbonate aqueous solution to a base paper mainly composed of cellulose fibers and drying the base paper.

[3] The zirconium content in an absolutely dry state is 0.2 to 1.5% [1]
Alternatively, the electrically insulating laminated board base paper according to [2].

[4] The electrically insulating laminate base paper according to [1] or [3], wherein the zirconyl compound is a zirconyl carbonate salt.

[5] A method for producing a base paper for an electrically insulating laminated board, characterized in that a base paper mainly composed of cellulose fibers is made to contain an aqueous zirconyl compound solution and then dried.

[6] A metal foil is prepared by impregnating a thermosetting resin on the electrical insulating laminate base paper described in any one of [1] to [4] and laminating a plurality of prepregs obtained by curing the resin. Electrically insulating laminated board molded together with.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Although this effect is not always clear, it is considered as follows. In a laminate obtained by impregnating a paper with a thermosetting resin, the paper plays a role of suppressing the expansion and contraction of the resin, and therefore, it is considered that the more rigid the fiber, the better the dimensional stability of the laminate. The migration of silver in the laminated plate proceeds through various routes, but often proceeds along the interface between the fiber and the resin or through the fiber wall. On the other hand, when the paper contains an aqueous zirconyl compound solution, the aqueous solution permeates into the cellulose fibers, but since zirconyl has the property of binding to oxygen adjacent to carbon, it reacts with the hydroxyl group or the carboxyl group of cellulose to give cellulose. It is presumed to bridge between the two. As a result, it is estimated that the rigidity of the fiber is increased and the dimensional stability is improved. In addition, the cross-linking between cellulose blocks the path of silver migration in the fiber wall,
It is considered that the silver migration resistance is improved.

The cellulose fiber used in the present invention is not particularly limited, and kraft pulp obtained from wood chips, wood pulp such as sulfite pulp, mechanical pulp, and non-wood pulp such as linter and hemp are used. it can.
The zirconyl compound in the present invention refers to a compound containing zirconyl (ZrO), and examples thereof include zirconyl ammonium carbonate, zirconyl acetate, zirconyl acetate ammonium, zirconyl chloride, zirconyl sulfate, and zirconyl nitrate. Two or more kinds are appropriately selected and used. Zirconyl ammonium carbonate is particularly preferred because of its high reactivity.

The zirconium content in the absolutely dry state of the laminated base paper of the present invention (see the following measuring method) is 0.2-1.
Preferably it is 5% by weight. By the way, when the zirconium content is low, the sufficient effect may not always be obtained, and conversely, even when the zirconium content is high, the effect of improving dimensional stability and silver migration resistance is saturated. Further, when the amount is extremely large, the water absorption of the base paper tends to be slightly decreased, which may cause a decrease in impregnation speed in the resin varnish impregnation step.

Method for Measuring Zirconium Content in Laminated Paper Base Paper The zirconium content in laminated paper is measured according to JIS P 81.
Determine the absolute dry basis weight of laminated board base paper according to No. 27, 900 ° C,
Ash weight per unit area of base paper and laminated board base paper obtained by ashing under the condition of 3 hours, atomic weight of zirconium (9
1.22), the molecular weight of zirconia (ZrO ₂ ) (formula weight:
123.22) was used, and zirconium was found to be present in the state of zirconia after ashing, and was calculated from the formula 1. However, if there is no base paper, after ashing the laminated board base paper, determine the zirconium content in the ash by a fluorescent X-ray method,
It is also possible to calculate the zirconium content in the laminated base paper. (Equation 1) Zirconium content (%) = {(W1 -W0) x (M1 /
M2) / W} × 100 W: absolute dry basis weight of laminated base paper (g / m ² ) W0: ash weight per 1 m ^{2 of} base paper (g / m ² ) W1: ash weight per 1 m ^{2 of} base laminate (G / m ² ) M1: Zirconium atomic weight M2: Zirconia molecular weight

The method for incorporating the zirconyl compound into the base paper is not particularly limited, and for example, any known method such as size press, impregnation, coating, spraying or the like may be used as the zirconyl compound aqueous solution (hereinafter also referred to as a working fluid). It is possible to employ a method in which the base paper is contained and dried. Of course, these are on-machine (in a continuous process on the paper machine)
Alternatively, it may be either off-machine (using a coating device as a separate step for the papermaking base paper). Further, in consideration of the permeability of the processing liquid into the cellulose fibers, the water content of the base paper containing the processing liquid is not particularly limited, but is preferably 4% or less.

Further, it is possible to add a surfactant, a flame retardant, a pH adjusting agent, a viscosity adjusting agent or the like to the processing liquid within a range not impairing the effects of the present invention. The drying method after containing the processing liquid is not particularly limited, and any known method can be adopted. In the present invention, the electrically insulating laminated base paper may be internally added when the paper is made, but size press, coating, impregnation and the like are more efficient.

[0021]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples,% means% by weight unless otherwise specified.

Example 1 Pulp made of 100% domestically unbeaten LBKP was used as a papermaking raw material, and the basis weight was 125 g in a laboratory square hand-made machine.
/ M ² , a thickness of 260 μm and a density of 0.48 g / cm ³ were obtained. Next, the base paper was impregnated with an impregnating solution prepared by diluting an aqueous solution of zirconyl ammonium carbonate with water to a concentration of zirconia of 0.1%, and then dried at a temperature of 120 ° C. for 5 minutes to obtain a laminated base paper. The zirconium content of the laminated base paper in an absolutely dry state was 0.13%. A laminated board was produced using this laminated board base paper.

Example 2 Pulp made of domestically unbeaten LBKP 100% was used as a papermaking raw material, and the basis weight was 125 g in a laboratory square hand-making machine.
/ M ² , a thickness of 260 μm and a density of 0.48 g / cm ³ were obtained. Next, the base paper was impregnated with an impregnating solution prepared by diluting an aqueous zirconyl ammonium carbonate solution with water to a zirconia conversion concentration of 0.2%, and then dried at a temperature of 120 ° C. for 5 minutes to obtain a laminated base paper. The zirconium content of the laminated base paper in the absolutely dry state was 0.25%. A laminated board was produced using this laminated board base paper.

Example 3 Except that the zirconia conversion concentration of the impregnating liquid was 0.7%,
A laminated base paper and a laminated board were obtained in the same manner as in Example 1.
Zirconium content of laminated base paper in absolute dry state is 0.8
8%. Example 4 Except that the zirconia conversion concentration of the impregnating liquid was 1.2%,
A laminated base paper and a laminated board were obtained in the same manner as in Example 1.
Zirconium content of laminated base paper in absolute dry condition is 1.4
5%.

Example 5 A laminated base paper and a laminated board were obtained in the same manner as in Example 1 except that the concentration of the aqueous zirconyl compound solution was 1.3% in terms of zirconia. The zirconium content of the laminated base paper in the absolutely dried state was 1.65%.

Example 6 A zirconyl acetate aqueous solution was added to water to obtain a zirconia-equivalent concentration of 0.7.
A laminated base paper and a laminated board were obtained in the same manner as in Example 1 except that the one diluted to 10% was used as the impregnating liquid. The zirconium content of the laminated base paper in the absolutely dried state was 0.88%.

Comparative Example 1 A laminated board base paper and a laminated board were obtained in the same manner as in Example 1 except that water was impregnated in place of the zirconyl compound aqueous solution. Comparative Example 2 A laminated board base paper and a laminated board were obtained in the same manner as Comparative Example 1 except that pulp made of linter 100% was used as a papermaking raw material.

The method for producing the laminate used in the present invention, the method for evaluating the impregnation with the aqueous resin, the method for measuring the silver migration resistance, and the method for evaluating the dimensional stability are as follows.

Manufacturing Method of Laminated Plate A laminated plate is manufactured by impregnating a base paper for laminated plate with a commercially available water-soluble phenolic resin (trade name: Shonor BRL-2854 / Showa Polymer Co., Ltd.) and drying with a drier. By doing so, a primary prepreg having a resin / base material ratio of 15:85 was prepared, and then a commercially available oil-modified phenolic resin (trade name: Shonor BLS-3122 / Showa Polymer Co., Ltd.) was used for the primary prepreg. ) And dried to produce a prepreg having a resin / base material ratio of both water-soluble phenolic resin and oil-modified phenolic resin of 50:50. Next, stack 8 prepregs at 165 ° C and 100 kg / cm.
^A phenol resin laminate was obtained by pressure molding for ² and 60 minutes.

Evaluation Method of Water-Soluble Phenolic Resin Impregnating Property The water-soluble phenolic resin impregnating property was measured by Klemm-type water absorption test (JIS P-8141), and the water absorption height (mm) after 10 minutes was used as a criterion for evaluation. did. In this case, it was judged that the higher the water absorption height, the richer the water absorption and the better the impregnation property of the water-soluble phenol resin.

Evaluation Method for Silver Migration Resistance of Laminated Plate A comb-shaped electrode having a line width of 1 mm and a line width of 1 mm was prepared on the laminated plate with a silver paste, and an ion migration evaluation system (trade name: AMI-025-P / Tabay Espec ( stock)
Manufactured by the company) at a constant temperature and humidity of 40 ° C. and 93% RH,
The insulation resistance between the electrodes was measured with a direct current of 50 V applied. In the evaluation, in order to prevent dew condensation at the start of the test, the sample was left at 60 ° C. for 1 hour, the sample was sufficiently stabilized at that temperature, the humidity was set, and the measurement was started 1 hour after the humidity was set. As an evaluation standard, the insulation resistance between electrodes was continuously measured, and it was determined that migration had occurred on the substrate having a resistance of 10 ⁶ Ω or less. From this continuous measurement data, the time until the first migration occurred (failure occurrence time) was used as a criterion for evaluation. When an ordinary commercially available circuit board is evaluated, durability of 1000 hours or more is required under the above conditions, but when the board is not subjected to moisture resistance treatment as in the above-mentioned laminated board manufacturing method, , At least 2
00 hours or more is desirable, and those having durability of 250 hours or more are judged to be excellent.

Evaluation Method of Dimensional Stability The dimensional stability of the laminated plate was evaluated by measuring the dimensional change rate by the following method. 25 spans on laminate
A mark is attached at 0 mm, and the dimension between the marks before and after heating and cooling is highly accurate two-dimensional coordinate measuring device (trade name: Digital Reader D
R-555 / D / manufactured by Dainippon Screen Mfg. Co., Ltd.). The dimensional change rate α was obtained from Equation 2. When the laminated base paper is manufactured by a normal paper machine and has anisotropy, the dimensional change rate is shown in the longitudinal direction and the transverse direction. The closer the dimensional change rate is to 0%, the better. (Equation 2) α (%) = {(L0-L1) / L0} × 100 L0: Length between gauge points before heating / cooling L1: Length between gauge points after heat treatment and cooling at 160 ° C. for 1 hour The results obtained in the examples are shown in Table 1. As is clear from Table 1, the laminated board base paper according to the production method of the present invention has good resin varnish impregnation property and silver migration resistance, and is capable of obtaining a laminated board having excellent dimensional stability. It was

[0033]

[Table 1]

[0034]

As described above, the present invention has the effect of providing a method for producing a laminated board base paper suitable for producing a laminated board having good silver migration resistance and dimensional stability. Therefore, its industrial effect is extremely large.

Claims (3)

[Claims] 1. A base paper for an electrically insulating laminated board obtained by incorporating a zirconyl compound into a base paper containing cellulose fibers as a main raw material. 2. A base paper mainly made of cellulose fiber,
The base paper for an electrically insulating laminated board according to claim 1, which is obtained by containing an aqueous zirconyl ammonium carbonate solution and drying. 3. The electrically insulating laminated board base paper according to claim 1 or 2, wherein the zirconium content in an absolutely dry state is 0.2 to 1.5%.