JPS615940A - Laminated board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a laminate suitable for printed wiring.

BACKGROUND OF THE INVENTION In recent years, laminates formed by impregnating a glass nonwoven fabric as a base material with an epoxy resin filled with a thermosetting resin have come into widespread use as printed wiring laminates. This is because it has properties such as electrical insulation that are comparable to epoxy resin laminates made of glass cloth as a base material, and it also has excellent punching workability. However, glass nonwoven fabrics are usually made by cutting glass fibers into appropriate lengths.
It is manufactured by dispersing it in water and forming it onto a running net, and epoxy resin powder or emulsion is used as the binder for the glass fibers.

Problems with the Prior Art Accordingly, in a laminate using the above-mentioned glass nonwoven fabric as a base material, the glass fiber binder is thermoset during the molding process, making it difficult to withstand the flow of the thermosetting resin impregnated into the base material. The problem was that the nonwoven fabric broke and a normal laminate could not be obtained. Furthermore, this phenomenon of nonwoven fabric breakage occurs because the binder that can be used in the nonwoven fabric papermaking process is inherently susceptible to thermal softening, and cannot be prevented even if the amount of binder used is increased.

For this reason, during laminated molding, in the case of glass cloth-based ffl laminates (in comparison, it is necessary to slow down the mold clamping speed of the hot platen or lower the molding pressure to reduce resin flow). As a matter of course, the number of air bubbles encapsulated in the glass nonwoven fabric base laminate increased, which caused deterioration of properties such as moisture resistance and heat resistance.

An object of the present invention is to provide a laminate that does not break the glass nonwoven fabric during molding, does not contain air bubbles, and has excellent moisture resistance and heat resistance by applying sufficient molding pressure.

Means for Solving the Problems In order to achieve the above object, the laminate of the present invention is made by mixing 10 to 40 pieces of softwood kraft bulb with a fiber length of 2 or more in glass fiber as a sheet-like base material. It uses glass nonwoven fabric.

In order to prevent nonwoven fabric breakage, the upper limit of the fiber length of the softwood kraft pulp in the glass nonwoven fabric is not particularly limited, but considering the deterioration of other properties due to the increase in the fiber length of the softwood kraft pulp, it should be within the 10 range. It is preferable that

Function Softwood kraft pulp mixed with glass fiber has the effect of binding the glass fibers, increasing the strength of the glass nonwoven fabric, and reducing its strength deterioration even at high temperatures. As cellulose fibers to be mixed with glass fibers, in addition to coniferous kraft pulp, we have conducted intensive experiments and studies on bamboo, Manila hemp, which are made of vascular fibers, flax, hemp, and Sanbu, which are bast fibers, and hardwood fibers, which are made with wood fibers. Coniferous kraft valves were selected because they were the best in terms of strength, electrical insulation properties of the laminate, etc.

The glass nonwoven fabric used in the present invention is produced by mixing softwood kraft pulp with glass fibers cut into appropriate lengths, dispersing the mixture in water, and forming it onto a running net. The fiber length of the softwood kraft pulp to be mixed is 2f.
If it is shorter than i, the dispersibility is good, but the strength of the glass nonwoven fabric cannot be increased, and breakage of the nonwoven fabric during molding cannot be prevented. On the other hand, if long fibers are mixed, their dispersibility will be poor and the longitudinal/lateral strength ratio of the glass nonwoven fabric will increase, which will increase the directionality of the laminate using this, resulting in curling, twisting, etc. Therefore, in order to maintain the same level of properties as the glass cloth base laminate, 10II
It is preferable to use a length up to llI.

Furthermore, if the content of softwood kraft pulp is less than 10% by weight, the strength of the glass nonwoven fabric will deteriorate significantly at high temperatures, making it impossible to achieve the object of the present invention. On the other hand, if the content of softwood kraft pulp exceeds 40% by weight, there is no problem in terms of nonwoven fabric breakage during molding, but softwood kraft pulp is inherently inferior in dimensional stability and moisture resistance compared to glass fiber. Therefore, the resulting laminate has poor properties, and there is no value in using glass nonwoven fabric.

Examples The glass fibers constituting the glass nonwoven fabric used in the present invention are generally E-glass fibers, but glass fibers of other compositions with excellent electrical properties may also be used. Further, as a method for producing glass fibers, any method may be used, such as a method in which long fibers are cut into appropriate lengths by melt spinning, or a method in which molten glass is directly made into short fibers by centrifugation or blowing. The thermosetting resin used is an epoxy resin, which is usually used for laminated boards.

Next, the present invention will be explained in detail.

Various glass nonwoven fabrics shown in Table 1 were used as base materials, and a prepreg obtained by impregnating and drying an epoxy resin was layered on the base material, and heat and pressure molded at a temperature of 160" C and a pressure of 40 kf/cT/l for 30 minutes. This molding The conditions were the same as those for the glass cloth base epoxy resin laminate. Table 1 shows the presence or absence of nonwoven fabric breakage during molding of each of the obtained laminates.

Further, the tensile strength of each glass nonwoven fabric at room temperature and when heated is shown in FIG. The tensile tester is a Schottspa complete tensioner with a crosshead speed of 0.5 volts/min.

Next, use various glass nonwoven fabrics shown in Table 1 and 2 (however, conventional example 3 is glass fabric) as a base material, and add epoxy resin to this in an amount of 6.
The prepregs obtained by impregnating and drying to a concentration of 0% by weight were stacked and heated and press-molded at a temperature of 160° C. and a pressure of 4Qky/c++f for 30 minutes to obtain a laminate with a thickness of 1.6 mm. However, in Conventional Example 2 only, the temperature was set to 1 to prevent the nonwoven fabric from breaking.
Heat and pressure molding was carried out at 60° C. and a pressure of 1 sky/ci for 30 minutes.

Although these laminates do not have metal foil pasted on the surface, the same effect can be achieved even if metal foil is pasted on the surface. The results of a characteristic test of a laminate using the following are shown.

In Table 3, moisture resistance insulation and soldering heat resistance are JIS-
0-6481. The amount of warpage is E-0,5/15
The warpage after the zero treatment was measured in accordance with JIS-0-Y 6481 (test dimensions were 300 x 300 m+). The dimensional change rate was calculated by calculating the amount of dimensional change in the longitudinal direction after the E-0,5/150 treatment using the following formula (specimen size was SOX 200 m).

×100 Punching workability was based on ASTM method.

Table 3 From Table 1 and Figure 1, the softwood kraft valve mixed with the nonwoven fabric has a fiber length of 21 mm to prevent the nonwoven fabric from breaking.
It can be seen that the content needs to be 111I or more and 10% by weight or more. In addition, if the glass nonwoven fabric has a tensile strength of 3.5 k51/15 m or higher at 120°C, it will not cause nonwoven fabric curl under normal molding conditions for glass fabric base epoxy resin laminated Ii plates. Understood.

Next, from Table 3, the content of coniferous tree 7
It has been found that those containing 0% by weight have poor moisture resistance and heat resistance, and it is necessary to reduce the content to 40% by weight or less. In addition, by reducing the fiber length of the softwood craft valve to 10cm or less,
It is possible to reduce the warpage of the laminate, and in this case, it is possible to maintain properties comparable to those of the glass cloth base laminate.

Effects of the Invention As mentioned above, the present invention uses a glass cloth that does not deteriorate in strength when heated, so the nonwoven fabric does not break during molding and has excellent moisture resistance and heat resistance! 11shi,
Its industrial value is extremely great as it also has good punching workability.

[Brief explanation of the drawing]

Figure 1 is a comparison diagram of the tensile strength of various glass nonwoven fabrics.

Claims (1)

[Scope of Claims] 1. A laminate in which a sheet-like base material is impregnated with a thermosetting resin and then stacked and molded under heat and pressure, in which 10% of softwood kraft pulp with a fiber length of 2 mm or more is added to glass fiber as the base material.
A laminate characterized by using a glass nonwoven fabric mixed with ~40% by weight. 2. The laminate according to claim 1, wherein the fiber length of the softwood kraft pulp is 2 to 10 mm.