JPH06128895A - Base paper for laminated board - Google Patents

Abstract

PURPOSE:To provide a base paper for laminated board suitable for producing a laminated board having excellent dimensional and shape stability in the processing step of a printed circuit board. CONSTITUTION:The base paper for laminated board contains >=10wt.% of bleached kraft pulp fiber produced from a hardwood having the cross-sectional area of the fiber of $200m<2> in the wood.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a laminated board base paper used for producing a laminated board such as a printed wiring board.

[0002]

2. Description of the Related Art Conventional laminates, especially laminates for printed wiring boards, are obtained by impregnating a laminate base paper with a thermosetting resin such as a phenol resin or an epoxy resin, and heating and drying it to a semi-cured resin state. (This is referred to as a prepreg), and a plurality of the prepregs are laminated and manufactured by thermocompression molding together with a metal foil. Such a laminated board is relatively inexpensive and almost satisfies the performance required for use in ordinary electric or electronic devices, and is therefore mainly used for household electric appliances.

However, due to the recent lighter, thinner, shorter and smaller electric products, the mounting density of electric parts such as ICs, capacitors and resistors has increased, and the conductor patterns of printed wirings have become finer. Therefore, not only the electrical performance of the laminated board but also the dimensional change in the process of processing the printed wiring board and the prevention of deformation such as warpage and twisting are becoming more and more strict.

That is, the printed wiring board processing step includes many steps of heating the printed wiring board, such as a printing and drying step of various resist inks, a washing and drying step, a heating step before punching, and the like. A soldering process must be performed to form and ultimately connect the electrical components.

Before and after such various heating steps,
If the printed wiring board undergoes a large dimensional change or deformation such as warpage or twisting, it may cause process troubles and render the product unusable.

On the other hand, as the pulp conventionally used for laminated board base paper, unbeaten bleached kraft pulp (LBKP) from domestic (especially Hokkaido) hardwood is generally used, but depending on the application. When blending softwood kraft pulp to increase the strength of laminated board base paper, using unbleached pulp for cost reduction, or using sulfite pulp (SP) for high whiteness There is. Such pulp is paper-made by a known paper machine, and the density of the obtained laminated base paper is 0.45 to 0.55 g / cm.
^It is as low as ³ .

[0007] In order to prevent the dimensional change and the shape change such as warpage and twist during the processing step of the printed wiring board as much as possible, the characteristics required for the base paper are pulp fiber and fiber network during the processing step. It can be mentioned that the effect of suppressing the dimensional change of the thermosetting resin is large.

To solve these problems, various proposals have been made in the past. For example, a method of adjusting the fiber orientation with a wire part of a paper machine to make the longitudinal / transverse tensile strength suitable (JP-A-57-176788), or a method of maintaining an orientation angle in a specific range (JP-A-57-176788). (Sho 59-49959 publication)
However, the improvement in dimensional stability is not sufficient.
Further, a method of mixing glass fibers (JP-A-59-16653, JP-A-59-201855, JP-A-60-179244)
However, it is difficult to adopt because of the large cost increase due to the deterioration of the glass fiber composition and the recovery of broke.

On the other hand, by increasing the dynamic elastic modulus of the laminated base paper,
Further, as a method of improving the dimensional stability of the laminated plate, a method of using pulp fibers having a thick cell wall and a large Runkel ratio, such as mangrove (JP-A-1-184126, Japanese Patent Application No.
No. 1-284104) has been proposed, but pulp from mangrove wood with a large Runkel ratio improves the dimensional stability of the laminated board, but since the fiber thickness is large, the laminated board decreases as the fiber bonding point decreases. There is a drawback that the strength of the base paper is lowered, which causes a paper break in the impregnation step and the workability is lowered.

On the other hand, although improvements have been made to improve the dimensional stability by modifying the impregnated thermosetting resin, there is a strong dependence on the essential characteristics of the base paper, and further improvement of the base paper is required. ing.

Wood raw materials for pulp, which have been conventionally used for laminated board base paper, include Japanese oak, linden, Japanese maple,
It is common to use domestically produced (especially Hokkaido) hardwood such as Harigi, wig, Harunire, and birch, and such wood generally has a fiber cross-sectional area of 200.
Since it is larger than μm ² , the dynamic elastic modulus is low and the dimensional stability of the laminate is not sufficient. Further, the fiber cross-sectional area of softwood such as Akamatsu, Japanese cedar, Yonematsu, rice cedar, and spruce is generally larger than that of the hardwood, and the dimensional stability of the laminate is not sufficient.

Therefore, the conventional laminated board made of such a base material is a printed wiring board for electric equipment having a higher mounting density of components or a printed wiring board for electronic equipment such as a computer requiring high accuracy. It was not suitable for commercial use.

[0013]

SUMMARY OF THE INVENTION In view of the above situation, the inventors of the present invention have taken into consideration the present situation so that the dimensions of a laminated board may be changed in order to prevent a dimensional change and a shape change such as warpage and twist during a process of processing a printed wiring board. Various studies were conducted on the relationship between the change and the physical properties of the base paper, and as a result of the relationship between the fiber morphology of various pulp materials and the physical properties of the base paper, a laminated board base paper containing pulp fibers produced from wood having a specific fiber cross-sectional area was obtained. The inventors have found that the laminated sheet obtained by using it is extremely excellent in stability of size and shape in the process including various heating operations, and completed the present invention.

An object of the present invention is to provide a laminated board base paper suitable for producing a laminated board having good stability in size and shape in the process of processing a printed wiring board.

[0015]

According to the present invention, in a laminated board base paper made from pulp from wood as a raw material, 10 parts by weight of pulp fiber produced from wood having a fiber cross-sectional area in the wood of 200 μm ² or less is used. It is a laminated board base paper characterized by containing at least%.

In the present invention, as a raw material pulp for laminated board base paper, it is essential to use pulp fibers manufactured from wood having a fiber cross-sectional area of 200 μm ² or less in wood as a raw material for laminated board base paper. The fact that the fiber cross-sectional area is small means that the fiber is thin, and the use of pulp fiber having a small cross-sectional area improves the dynamic elastic modulus of the laminated board base paper as described below, and further the laminated board. The dimensional stability of is improved.

The reason for this is that, by using pulp fibers having a small cross-sectional area, the total number of pulp fibers in the laminated base paper is increased when the same basis weight is used for comparison, which increases the fiber bonding points. It is considered that the load applied to one fiber is easily propagated, and the load is dispersed and applied to more fibers and fiber connection points, so that the dynamic elastic modulus is improved. That is, it is possible to increase the effect of suppressing expansion and contraction of the thermosetting resin in the heating / cooling step of the laminate by improving the dynamic elastic modulus of the laminate base paper by using pulp fibers having a small cross-sectional area. it can.

Examples of wood materials preferably used in the present invention include eucalyptus and acacia.
As long as the fiber cross-sectional area in wood is 200 μm ² or less, there is no particular limitation to these materials. These eucalyptus,
Acacia has a fiber cross-sectional area of 200μ due to differences in weather conditions, growth conditions related to land, etc.
Since it is more than m ² or less than 200 μm ² , for the purpose of the present invention, Eucalyptus exata, Eucalyptus deri gatensis, eucalyptus triodora, Eucalyptus grouse No.
1. It is necessary to properly select and use a tree species of 200 μm ² or less such as acacia melancy.

In the laminated base paper of the present invention, when pulp fibers having a fiber cross-sectional area of more than 200 μm ² in wood are used, the dynamic elastic modulus of the laminated base paper becomes low as described above.
It is not suitable because the stability of the size and shape in the process including the heating operation of the laminated plate deteriorates. On the other hand, the wood species having a fiber cross-sectional area of 200 μm ² or less in wood has an extremely excellent effect on the stability of the size and shape, but the wood species is relatively limited. Further, the lower limit value of the fiber cross-sectional area in wood of naturally existing wood is considered to be about 90 μm ² .

In the present invention, the fiber cross-sectional area in wood is 200 μm.
If the pulp fiber is m ² or less, it is not necessary to pay particular attention to its use, and the larger the proportion of pulp fibers having the fiber cross-sectional area of 200 μm ² or less, the better the stability of the size and shape. . However, the fiber cross section is 20
Pulp fiber of 0 μm ² or less is 10% by weight per absolutely dry pulp.
With the above content, the above-mentioned size and shape stability can be practically sufficiently ensured even when used together with pulp fibers having a fiber cross-sectional area of more than 200 μm ² . If the content is less than 10% by weight, the stability of the size and shape cannot be ensured, which is not suitable.

The method for mixing pulp fibers is as follows: 1 wood chip having a fiber cross-sectional area of 200 μm ² or less at the wood chip stage.
It may be a method of bleaching the obtained pulp by mixing it so as to be 0% by weight or more and performing a known kraft cooking, or a known kraft cooking alone for each tree species and containing a predetermined pulp before or after bleaching. A method of mixing so as to obtain a ratio may be used.

On the other hand, it is known that pulp fibers having thick film cells such as mangrove materials having a large Runkel ratio also increase the dynamic elastic modulus of the laminated base paper and improve the dimensional stability of the laminated board. In the laminated board base paper of the present invention, when pulp fibers having a small fiber cross-sectional area are used, the fact that the fiber cross-sectional area is small has a priority over the Runkel ratio and affects the stability. However, even a pulp fiber having a fiber cross-sectional area of 200 μm ² or less is preferable because a larger Runkel ratio contributes to the stability, and a Runkel ratio of less than 0.4 is not preferable.

In order to produce a laminated board from the laminated board raw paper of the present invention, two or more of the thermosetting resin impregnated prepregs thus obtained are impregnated with a thermosetting resin and dried. Are laminated, and the lamination precursor is heated to a required temperature for thermosetting the thermosetting resin, and if necessary, pressure is applied in a predetermined molding die to perform integral molding.

As the thermosetting resin, a resol type phenol-formaldehyde resin is generally used.
Other examples include, but are not limited to, ordinary phenol-formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, epoxy resin, unsaturated polyester resin, polyimide resin, and the like. Used.

The conditions of heating and pressurizing operation for thermosetting vary depending on the kind and amount of the thermosetting resin and the structure and size of the laminate, but generally, the temperature is 150 to 180 ° C., 8
It is carried out at a pressure of 0 to 120 Kg / cm ² for 30 to 60 minutes.

The methods for measuring the cross-sectional area of the pulp fiber, the Runkel ratio of the pulp fiber, the dynamic elastic modulus and the dimensional change rate of the laminate used in the present invention are as follows. Method for measuring the cross-sectional area of fibers in wood Since the wood chips are too hard to cut the cross-section without destroying the fiber morphology when the wood chips are in a dry state, the wood chips are gradually heated by putting them in water. After pretreatment, the ostium of the chips is cut at right angles to the fiber direction using a razor. Since cells swell in the water-containing state and are not suitable for observation, the cells are left in ethanol for dehydration. The fiber cross section of the wood mouth surface is photographed with a scanning electron microscope, a laser microscope, etc., at a magnification of 1000 times, and the fiber widths of 200 or more fibers in the major axis direction and the minor axis direction are measured. From the above, the cross-sectional area of pulp fiber is calculated assuming that the fiber is rectangular. The cross-sectional area of the individual fibers in the wood chips is not constant and mixed in size and size, so 2
It shall be measured for more than 00 fibers and evaluated by the average value.

Runkel Ratio of Fibers in Wood The Runkel ratio (R) of fibers in wood is an index for characterizing the morphology of fibers, and is the width L of the lumen (lumen) of the fiber and the thickness t of the cell wall. It is the value obtained from Equation 1 from

[0028]

[Formula 1] R = 2 · t / L

Method of Measuring Dynamic Elastic Modulus The dynamic elastic modulus of the laminated base paper is measured by the following method when it has no directivity like a hand-made sheet. The ultrasonic wave propagation speed C of the laminated board base paper made by the hand-papermaking machine that has been conditioned for at least 24 hours in the environment of temperature 20 ° C and relative humidity 65% is measured by an ultrasonic wave speed meter (eg, SST-250, manufactured by Nomura Shoji). ) Is used for measurement. Next, the thickness of the laminated board raw paper is measured according to JIS P 8118, and the basis weight is measured to obtain the density ρ of the laminated board raw paper.

The dynamic elastic modulus E is obtained from the equation 2.

[0031]

[Equation 2] E = ρ (C) ²

When the laminated base paper is produced by a normal paper machine, since the paper has anisotropy, the dynamic elastic modulus E _MD and E _CD in the machine direction and the cross machine direction are calculated by the equation 3 from the dynamic elastic modulus E. _Calculate (geometric mean of E _MD and E _CD ).

[0033]

[Formula 3]

Measuring Method of Dimensional Change of Laminated Plate The dimensional change rate of the laminated plate is measured by the following method. The laminated base paper was impregnated with a thermosetting resin, that is, a resole-type phenol resin so that the solid weight ratio of the base material to the resin was 1: 1.
Dry at a temperature of 00 ° C. for 5 minutes to prepare a prepreg.
8 sheets of this prepreg are laminated, and 165 ° C, 100 kg /
A laminated plate is manufactured by pressurizing and pressing at cm ² for 60 minutes.
The laminated plate is marked with a span of about 250 mm and the temperature is 2
After conditioning for 24 hours in an environment of 0 ° C and 65% relative humidity,
The distance L ₀ mm between the reference points is measured with a highly accurate two-dimensional coordinate measuring device (for example, digital reader, DR-550-D, manufactured by Dainippon Screen Mfg. Co., Ltd.). Then, heat at 120 ° C. for 15 minutes, and again in an environment of 20 ° C. and 65% relative humidity for 24 hours.
After time humidity control, the distance L ₁ mm between the same gauge points is measured.
The dimensional change rate α is obtained from the equation 4. When the laminated board base paper is manufactured by a normal paper machine and has anisotropy, the dimensional change rate of the laminated board is shown as a longitudinal direction, a transverse direction, and a geometric mean value in the longitudinal direction and the transverse direction. The smaller the dimensional change rate, the higher the dimensional stability of this laminated plate. However, in the present invention, the dimensional change rate (in the case of having anisotropy, the geometric mean value in the machine direction and the machine direction)
Is 0.025% or less, dimensional stability does not pose a practical problem.

[0035]

[Formula 4] α (%) = [(L ₀ −L ₁ ) / L ₀ ] × 100

[0036]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is of course not limited thereto. In the examples and comparative examples,%
Indicates weight% unless otherwise specified.

The method for producing the pulp used in the examples is as follows. Pulp production method (1) Unbleached pulp Cooking conditions: 4 liter autoclave, craft white liquor (sulfurization degree 29%), liquid ratio 4.5, maximum temperature 167 ° C, holding time 90 minutes, alkali addition rate = unbleached copper Value is 18
15.0 per dry-dry tip to be within ± 0.5
Vary within the range of ˜22.0% (as Na ₂ O).

(2) Bleached pulp By the known C-E-H-D four-stage bleaching method, the whiteness of the pulp by the hunter of sodium hypochlorite was adjusted to be within the range of 89.0 ± 1.0. Pulp was placed in a polyethylene bag in the laboratory at different addition rates and bleached under the conditions described below. Chlorine stage C: Cl ₂ addition rate = Kappa number of unbleached pulp ×
0.2%, temperature normal temperature, time 60 minutes, pulp concentration 4%; alkali extraction stage E: NaOH addition rate = Kappa number of unbleached pulp x 0.1%, temperature 60 ° C, time 90 minutes, pulp concentration 10% Sodium hypochlorite stage H: Sodium hypochlorite addition rate = 0.3 to 4.0% per absolutely dry unbleached pulp, temperature 40
C, time 120 minutes, pulp concentration 10%; chlorine dioxide stage D: chlorine dioxide addition rate = 0.4% per absolutely dry unbleached pulp,
Temperature 75 degrees, time 120 minutes, pulp concentration 10%

Examples 1 to 4 The fiber cross-sectional area in wood is 128 μm ² , and the Runkel ratio is 0.
96 eucalyptus exata materials were digested by the above-mentioned kraft cooking method to produce unbleached kraft pulp with a Kappa number of 18.5, and this pulp was used in the laboratory under the above-mentioned bleaching conditions by the four-stage bleaching method to produce LBKP ( Pulp whiteness = 89.2%) was produced. Similarly, LBKP (pulp whiteness =) was obtained by using Hokkaido hardwood mixed wood chips having a fiber cross-sectional area in wood of 248 μm ² and a Runkel ratio of 0.48.
89.2%). This eucalyptus LBKP and Hokkaido hardwood LBKP are mixed to give 12% (Example 1), 30% (Example 2) of eucalyptus LBKP per absolutely dry pulp.
The content of 50% (Example 3) and 100% (Example 4) was used as a papermaking raw material, without beating, and without adding papermaking chemicals, fillers, etc., in a laboratory square type handmaking machine, the basis weight was 125 g /
A laminated base paper having an m ² , a thickness of 255 μm and a density of 0.5 g / cm ³ was made into a paper, and its dynamic elastic modulus was measured. Using these laminated board base papers, a laminated board was prepared by the method for measuring the dimensional change rate of the laminated board, and the dimensional change rate was measured.

Example 5 The fiber cross-sectional area in wood is 175 μm ² , and the Runkel ratio is 1.
07 eucalyptus delgatensis wood was cooked by the above-mentioned kraft cooking method to produce unbleached kraft pulp with a Kappa number of 18.5, and this pulp was then used in the laboratory under the bleaching conditions under the above-mentioned bleaching conditions to obtain LBKP (pulp whiteness = 89. .8
%) And using this pulp alone Examples 1-4
The same method as above, basis weight 126 g / m ² , thickness 255 μ
Laminated paper having m and a density of 0.5 g / cm ³ was made into a paper, and its dynamic elastic modulus was measured. Further, a laminated board was produced from this laminated board base paper, and the dimensional change rate was measured.

Example 6 The fiber cross-sectional area in wood was 107 μm ² , and the Runkel ratio was 0.
65 eucalyptus citriodora wood was digested by the above-mentioned kraft cooking method to produce unbleached kraft pulp with a Kappa number of 18.4, and this pulp was used in the laboratory under the bleaching conditions under the above-mentioned bleaching conditions to obtain LBKP (pulp whiteness = 89). .3%)
Was used to make a laminated base paper having a basis weight of 126 g / m ² , a thickness of 255 μm, and a density of 0.5 g / cm ³ by the same method as in Examples 1 to 4, and the dynamics thereof were used. The elastic modulus was measured. Further, a laminated board was produced from this laminated board base paper, and the dimensional change rate was measured.

Example 7 The cross-sectional area of fibers in wood was 125 μm ² , and the Runkel ratio was 1.
77 eucalyptus grouse No. 1 wood was cooked by the above-mentioned kraft cooking method to produce unbleached kraft pulp with a Kappa number of 18.3, and this pulp was used in the laboratory under the bleaching conditions under the above-mentioned bleaching conditions. Degree = 89.4
%) And using this pulp alone Examples 1-4
In the same manner as above, the basis weight is 126 g / m ² , the thickness is 255 μm,
A laminated base paper having a density of 0.5 g / cm ³ was made into a paper, and its dynamic elastic modulus was measured. Further, a laminated board was produced from this laminated board base paper, and the dimensional change rate was measured.

Example 8 The cross-sectional area of fibers in wood is 122 μm ² , and the Runkel ratio is 1.
41 acacia melancly wood was cooked by the above-mentioned kraft cooking method (liquid ratio = 2.85) to produce unbleached kraft pulp with a Kappa number of 18.3, and this pulp was used in the laboratory under the bleaching conditions. To produce LBKP (pulp whiteness of 88.2), and using this pulp alone in the same manner as in Examples 1 to 4, the basis weight is 126 g / m ² , and the thickness is 25.
Paper making of laminated board base paper of 5 μm and density of 0.5 g / cm ³ ,
The dynamic elastic modulus was measured. Further, a laminated board was produced from this laminated board base paper, and the dimensional change rate was measured.

Comparative Example 1 The cross-sectional area of fibers in wood was 248 μm ² , and the Runkel ratio was 0.1.
Cooked from 48 oak woods by the craft cooking method,
An unbleached kraft pulp with a Kappa number of 17.7 was produced, and this pulp was then used in the laboratory to produce LBKP (pulp whiteness 89.2%) under the bleaching conditions described above in Examples 1-4. LBKP from the obtained eucalyptus exata material (fiber cross-sectional area in wood is 128 μm ² ,
A Runkel ratio of 0.96) was used in an amount of 8% based on absolutely dry pulp, and the basis weight was 126 g / m 2 in the same manner as in Examples 1 to 4.
^2. A laminated base paper having a thickness of 255 μm and a density of 0.5 g / cm ³ was made into paper, and its dynamic elastic modulus was measured. Further, a laminated board was produced from this laminated board base paper, and the dimensional change rate was measured.

Comparative Example 2 The fiber cross-sectional area in wood was 254 μm ² , and the Runkel ratio was 1.
No. 2 eucalyptus grandis wood was cooked by the above-mentioned kraft cooking method to produce unbleached kraft pulp with a Kappa number of 18.2, and this pulp was used in the laboratory under the bleaching conditions under the LBKP (pulp whiteness 88. 5%), and using this pulp alone in the same manner as in Examples 1 to 4, basis weight 126 g / m ² , thickness 255 μm, density 0.
A 5 g / cm ³ laminated base paper was made into paper, and its dynamic elastic modulus was measured. Furthermore, a laminated board is manufactured from this laminated board base paper,
The dimensional change rate was measured.

Table 1 shows the measurement results obtained in Examples 1 to 2.

[0047]

[Table 1]

As is clear from Table 1, the fiber cross-sectional area is 2
The laminated board base paper of the present invention produced solely from pulp having a size of 00 μm ² or less has a high dynamic elastic modulus, and the dimensional change rate of the laminated board produced using this base paper is extremely excellent (Examples 4 to 4).
8) Also, the laminated board base paper of the present invention containing 10% or more of the above pulp has a high dynamic elastic modulus, and the dimensional change rate of the laminated board is low enough to be practically used (Examples 1 to 3).
However, the laminated board base paper containing less than 10% of the pulp has a low dynamic elastic modulus and a relatively high dimensional change rate of the laminated board, and therefore cannot be put to practical use (Comparative Example 1). The laminate obtained by using pulp exceeding 200 μm ² alone as a raw material for the laminate base paper cannot be put to practical use for the above reason (Comparative Example 2).

[0049]

As described above, the present invention has the effect of providing a laminated board base paper most suitable for producing a laminated board having good size and shape stability in the process of processing a printed wiring board.

Claims (1)

[Claims] 1. A laminated board base paper made from pulp from wood as a raw material, wherein the fiber cross-sectional area in the wood is 20.
1 pulp fiber made from wood that is 0 μm ² or less
A laminated board base paper characterized by containing 0% by weight or more.