JP2959392B2 - Laminated board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laminate. More specifically, the present invention relates to a laminate for a printed wiring board, which has a low chlorine ion content, is excellent in resin impregnation, and has improved dimensional change, warpage and twist.

[0002]

2. Description of the Related Art A conventional laminate, especially a laminate for a printed wiring board, is prepared by impregnating a laminate base paper with a thermosetting resin such as a phenolic resin or an epoxy resin and heating and drying the same to form a semi-cured resin. (This is referred to as a prepreg), a plurality of the prepregs are laminated, and a hot-press molding is performed together with a metal foil. Since such printed wiring boards are relatively inexpensive and almost satisfy the performance for use in ordinary electric or electronic devices, they are widely used mainly in home electric appliances.

[0003] However, in recent years, since electric products have become lighter, thinner and smaller, the mounting density of electric product parts such as ICs, capacitors, and resistors has increased, and the conductor patterns of printed wiring have become thinner. For this reason, not only the electrical characteristics of the laminated plate, but also the requirements for the prevention of deformation such as dimensional change and warpage and torsion in the resin impregnation processing step are becoming increasingly severe.

[0004] In order to increase the working efficiency in the prepreg processing step, it is necessary that the resin penetrates into the holes in the base paper at a high speed and that a predetermined weight% of the resin is retained in the paper layer. In addition, the resin does not remain on the surface of the paper layer to cause adhesive trouble, and the resin is uniformly impregnated in the paper layer,
The decisive factor is that the base paper has essential requirements such as no impregnation unevenness. In recent years, high heat resistance and dimensional stability have been required, and in addition to the conventional phenolic resin and epoxy resin, highly viscous resins such as polyester resins have been used, so that better impregnation has been achieved. The necessity of a laminated board having a property is increasing more and more.

Conventionally, in order to obtain good resin impregnating property and dimensional stability, a base paper for laminated board is prepared by using bleached kraft pulp from hardwood material without being beaten to obtain a material having a thickness of 0.45 to 0.55 mm.
It is common to use low density paper of g / cm ³ .

[0006] In order to improve the impregnating property of the resin, a method of removing fine fibers during the pulp treatment step and the papermaking step (JP-A-62-184200, JP-A-63-21)
1395, JP-A-2-300377, JP-A-4-263694, etc.), a wet press pressure or a calender pressure is set in a specific range in a paper making process,
A method of adjusting the density of the obtained paper (Japanese Patent Application Laid-Open No. 3-899) and a method of defining the pore volume ratio in the paper layer (Japanese Patent Application Laid-Open No. 3-890) have been proposed. However, a sufficient effect has not been obtained.

On the other hand, the processing steps of the printed wiring board include various resist printing, drying steps, washing and drying steps, heating steps before punching, formation of silver through holes, and finally, soldering for connecting electric parts. There are many steps for heating the printed wiring board such as processing steps. If the printed wiring board undergoes a large dimensional change or deformation such as warpage or twist before and after such various heating steps, there is a problem that a process trouble occurs and the product cannot be put to practical use.

Therefore, in order to prevent dimensional changes and warping and twisting of the printed wiring board during the processing step as much as possible, dimensional changes due to the thermosetting resin used in the base paper are somewhat reduced. It is required to suppress it at all.

As a method of reducing such dimensional changes, warpage, twist, etc., for example, a method of adjusting the fiber orientation in the wire part of papermaking and optimizing the aspect ratio of the tensile strength (Japanese Patent Laid-Open No. 57-176788). Japanese Patent Application Laid-Open No. 59-49959) and a method of maintaining an orientation angle in a specific range (JP-A-59-49959) have been proposed, but the improvement in dimensional stability is not always sufficient. For the same purpose, a method of mixing paper with glass fibers (JP-A-59-201855, JP-A-60-179244, etc.) has also been proposed. Poor recoverability of the generated waste paper leads to an increase in product cost.

[0010] In addition, as a method of increasing the dynamic elastic modulus of the laminated base paper and improving the dimensional stability of the laminated board, a method of using pulp having a thick cell wall and a large Runkel ratio, such as mangrove material, has been proposed. JP-A-1-184126 and JP-A-3-146794) and a method of using a wood fiber having a small fiber cross-sectional area (Japanese Patent Application No. 4-282818).
Has been proposed. However, when mangrove pulp having a large Runkel ratio is used, the dimensional stability of the laminated board is good, but the fiber bonding point is reduced due to the large pulp fiber diameter, whereby the strength is reduced, and the paper breakage in the impregnation process is reduced. This causes a drawback that the workability is reduced.
Further, when wood fibers having a small fiber cross-sectional area are used, there is a drawback that the type of material used is limited. Further, a method has been proposed in which the pulp sheet is subjected to a pressure treatment to reduce the porosity of the lumen (Japanese Patent Application Laid-Open No. 4-163400), but there is a problem that the resin impregnation property is reduced.

On the other hand, although some measures have been taken to improve the impregnating property, dimensional stability, electrical properties, etc. of the resin by modifying the thermosetting resin to be impregnated, these are dependent on the essential properties of the base paper. Therefore, there is a strong demand for further improvement of the base paper.

[0012]

SUMMARY OF THE INVENTION In view of the present situation, the present inventors have studied various characteristics of a laminated board required for a series of processing steps of prepreg processing, lamination, hot press molding, and printed wiring.
That is, in order to further improve the resin impregnating property in the prepreg processing step, the dimensional stability in the processing step of the printed wiring board, the electrical properties of the printed wiring board and the punching workability, etc., the relationship between the laminate and the base paper properties, various pulp After extensive studies on the relationship between the fiber morphology of the fibers and the physical properties of the base paper, the laminated base paper obtained by using hemp pulp in combination with bleached hardwood kraft pulp has the properties of the prior art, especially the resin impregnation of the base paper. Further, they have found that the stability of the dimensions and the shape of the laminated plate is extremely excellent, and have completed the present invention.

An object of the present invention is to provide a laminated board for a printed wiring board which has good resin impregnation in a prepreg processing step and stability of dimensions and shape in a printed wiring board processing step.

[0014]

According to the present invention, a laminate made of paper made from cellulose pulp and impregnated with a resin, wherein the pulp comprises 7 to 70% by weight of hemp pulp and 30 to 93% by weight of wood pulp. This is a laminate for a printed wiring board.

The hemp pulp used in the present invention includes, but is not particularly limited to, bast fibers such as cannabis, flax, chomp, kenaf (or hemp), and leaf fibers such as manila hemp and cysile hemp. , Fiber strength, fiber length, digestibility, bleachability,
In consideration of the mixing ratio of contaminants and the like, Manila hemp pulp obtained by alkali cooking, kraft cooking and sulfite cooking is preferred. Such hemp pulp has a very low lignin content compared to wood and is easily digestible and bleachable, so that the amount of cooking chemicals and bleaching chemicals can be significantly reduced as compared to wood. Thus, hemp pulp has a very low chloride ion content.

The content of hemp pulp is 7 to 70% by weight, preferably 10 to 50% by weight, based on the total weight of the bone dry pulp. When the content of hemp pulp is less than 7% by weight, the effect using hemp pulp is not exhibited, and when the content exceeds 70% by weight, the effect reaches a peak and the formation of the base paper deteriorates, which is not suitable.

The wood pulp used in the present invention in combination with the hemp pulp may be either a hardwood lumber or a chemical pulp using softwood, but bleached kraft pulp using hardwood is preferred.

A known technique for producing a laminate base paper from a mixture of hemp pulp and wood pulp by a wet paper machine can be applied to the present invention as it is.

In the present invention, excellent impregnation properties are obtained because the hemp pulp fibers used are rigid and have a longer average fiber length than wood pulp fibers, and the fiber is resistant to various impacts applied during the papermaking process. It is presumed that, since there is little deformation such as bending, bending, twisting, etc., the individual voids formed in the paper layer have a uniform shape when the paper is made, and are not easily deformed.
As a result, the impregnation speed of the resin is improved, the impregnation of the resin is uniform, and uneven impregnation is reduced. Also, since the dynamic elastic modulus of hemp pulp is high, the laminate containing hemp pulp also varies depending on the content, but the dynamic elastic modulus is high, and the laminate obtained using this base paper is The effect of suppressing expansion and contraction during heating and cooling of the laminate in the processing step is great. Further, since the single fiber strength of hemp pulp is higher than that of wood pulp, the strength of the laminated board using hemp pulp also increases, and workability during resin impregnation in the prepreg processing step is remarkably improved.

As described above, the laminate for a printed wiring board of the present invention greatly improves the resin impregnation, the dimensional change of the laminate, and the stability of warpage and twist. In particular, since the resin impregnation unevenness is reduced, the fiber surface is uniformly coated with the resin, and therefore, the moisture-proof property is improved. On the other hand, the hemp pulp used in the present invention, as described above, is extremely excellent in digestibility and bleaching property because of its low lignin content as compared with wood, and therefore requires only a small amount of chemicals. The ion content is also very low. In particular, depending on the digestion method, the amount of chlorine ions can be significantly reduced, and when such hemp pulp is used for a laminate for a printed wiring board, it has excellent electrical insulation properties and excellent properties against silver migration. It is possible to manufacture a printed wiring board laminate having the same.

[0021]

EXAMPLES The present invention will be described more specifically with reference to examples below, but the present invention is of course not limited to these. The percentages in Examples and Comparative Examples are all% by weight.
Is shown.

The hemp pulp used in Examples and Comparative Examples of the present invention was Manila hemp (trade name: N-4) produced in Ecuador under the following pulping conditions. Was charged with absolute dry 870kg Manila hemp Earth kettle 15 m ^3, sodium sulfite was added absolute dry hemp per weight 18.0%, liquor ratio 7.5, the maximum temperature 162 ° C., rise time 60 minutes temperature, the highest temperature Was cooked for 90 minutes, then drained, carefully selected and washed to produce hemp pulp. The kappa number of hemp pulp was 8.9, and the Hunter whiteness of unbleached pulp was 73.5%.

Examples 1 to 4 The above-mentioned hemp pulp and bleached hardwood kraft pulp (LBKP) having a hunter brightness of 85.0%
Was mixed to prepare a mixed pulp. The content of hemp pulp was 10% (Example 1) and 30% based on the total weight of the bone-dry pulp.
(Example 2), 50% (Example 3) and 65% (Example 4), each of the mixed pulp was unbeaten and hand-made in a laboratory square-type hand-making machine, and the basis weight was 126 g / m2. ² and a base paper having a density of 0.5 g / cm ³ were prepared. The obtained laminate base paper was measured for chloride ion content, formation, oil permeability, dynamic elastic modulus, tensile strength, and dimensional change of the laminate by the following test methods.

Test method (1) Visual observation with a joint The evaluation was made on three scales: good for observation, poor for practical use, but bad for practical use. (2) Oil Penetration A container containing castor oil is placed in a thermostat kept at a water temperature of 30 ° C., the temperature of the castor oil is kept at a constant temperature of 30 ° C., and a test piece punched into a circular shape having a diameter of 20 mm is cast into a liquid of castor oil. The test piece was placed horizontally on a surface, and the time from when the test piece came into contact with the castor oil liquid surface to when the castor oil uniformly penetrated into the upper surface of the test piece was measured for a number of seconds to determine the degree of penetration. The measurement was performed on both the front and back sides of the paper, and the average value of the front and back sides was calculated. The lower the numerical value, the better the impregnating property, which is an index of the resin impregnating property.

(3) Dynamic Modulus Since the hand-made sheet has no fiber orientation, it was measured by the following method. The humidity was conditioned for 24 hours in an environment of a temperature of 20 ° C. and a relative humidity of 65%, and the ultrasonic wave propagation speed C of the laminate base paper created by the hand making machine was measured with an ultrasonic wave speed meter (trade name: SST-250,
Nomura Corporation). Next, the thickness of the laminated base paper is measured in accordance with JIS P 8118, and the basis weight of the rice is measured to determine the density ρ of the laminated base paper, and the dynamic elastic modulus E is determined by E = ρ (C) ² . Was. (4) Tensile strength Using a Tensilon tensile tester (model: U-1573, manufactured by Toyo Baldwin), a test piece 15 mm, span 10
It was measured at 0 mm and a load of 100 kg.

(5) Chloride ion content Measured according to JIS K 0101 32.1, absorbance method. (6) Dimensional change rate of laminated board “Preparation of laminated board” A laminate base paper is impregnated with a thermosetting resin, that is, a resol-type phenol resin, so that the solid content weight ratio of the base material to the resin is 1: 1. It dried at the temperature of 100 degreeC for 5 minutes, and prepared the prepreg. Eight of these prepregs were laminated and pressed at a temperature of 165 ° C. and a pressure of 100 kg / cm ² for 60 minutes to produce a laminate. "Dimensional change rate" This laminate was rated at a span of 250 mm, and a temperature of 20
After adjusting the humidity for 24 hours in an environment of 65 ° C. and a relative humidity of 65%, the distance L0 mm between the scores is measured with a high-precision two-dimensional coordinate axis measuring device (digital reader, model: DR-550-D, manufactured by Dainippon Screen). Then, the laminated plate is
After heating for 15 minutes in a dryer at
After conditioning for 24 hours in an environment at a temperature of 65 ° C. and a relative humidity of 65%, the distance L1 mm between the same scores was measured. The dimensional change rate α is
α (%) = [(L0−L1) / L0] × 100.

Comparative Examples 1-3 The content of hemp pulp (manila hemp) was reduced to 0% (Comparative Example 1), 4% (Comparative Example 2) and 80%.
Except for (Comparative Example 3), a laminated base paper was prepared in the same manner as in Examples 1 to 4, and the quality was evaluated.

Table 1 shows the measurement results obtained in the examples and comparative examples.

[0029]

[Table 1]

As is clear from Table 1, the laminated base paper according to the present invention in which hemp pulp is contained in LBKP is LBKP.
Compared to a 100% laminate base paper (hemp pulp 0%, Comparative Example 1), the oil permeability is low (the resin impregnation property is good), and the dynamic elastic modulus and tensile strength are high. Furthermore, the chloride ion content in the laminate for printed wiring boards decreases as the hemp pulp content increases. The dimensional change rate of the laminate made of the base paper of the present invention is small, and the effect is more excellent as the content of hemp pulp is higher (Examples 1 to 3).
On the other hand, if the content of hemp pulp is small, no effect is exhibited (Comparative Example 2). Conversely, if the content of hemp pulp is large, the formation deteriorates and it cannot be used practically (Comparative Example 3).
Not suitable.

[0031]

According to the present invention, there is provided a laminate for a printed wiring board having a low content of chlorine ions, which is excellent in resin impregnating property in a processing step of a prepreg and stability of dimensions and shape in a processing step of a printed wiring board. It has the effect of doing.

Claims (1)

(57) [Claims] 1. A papermaking process using cellulose pulp as a raw material,
A laminated board for a printed wiring board, wherein the pulp is composed of 7 to 70% by weight of hemp pulp and 30 to 93% by weight of wood pulp.