JPH0364306B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a laminate suitable for printed wiring. BACKGROUND OF THE INVENTION In recent years, laminates made of glass nonwoven fabric as a base material and impregnated with epoxy resin, which is a thermosetting resin, have come into widespread use as laminates for printed wiring. This is because properties such as electrical insulation are comparable to epoxy resin laminates made of glass cloth as a base material, and furthermore, they have excellent punching workability. Glass nonwoven fabrics are usually manufactured by cutting glass fibers into appropriate lengths, dispersing them in water, and forming them onto a running net. However, epoxy resin powder or emulsion is used as a binder for the glass fibers. There are two known types: one type that uses kraft pulp and the other type that mixes cellulose fibers such as softwood kraft pulp, and each type has its own drawbacks. Problems to be Solved by the Invention In the type that uses epoxy resin powder or emulsion, the binder that can be applied in the papermaking process is inherently easily softened by heat, so it is laminated with a thermosetting resin under normal molding conditions. During molding, the binder softens and cannot withstand the flow of resin, causing the nonwoven fabric to break and making it difficult to produce a normal laminate. In addition, types that mix cellulose fibers such as softwood kraft pulp have less nonwoven fabric breakage during molding, but the punching processability of the laminate is relatively poor. In particular, as the mounting density of printed wiring boards has increased in recent years, cracks have become a problem between the holes when punching a pattern with a large number of small holes. The present invention provides a laminated plate based on glass nonwoven fabric that does not cause the nonwoven fabric to break during molding and has good punching workability, especially IC pitch (2.54 mm pitch).
The purpose of the present invention is to provide a laminate plate that can be punched out with a dense pattern of small holes without cracking. Means for Solving the Problems In order to achieve the above object, the laminate of the present invention uses, as a sheet-like base material, a glass nonwoven fabric in which 10% by weight or more of hardwood kraft pulp is mixed with glass fiber. The upper limit of the content of hardwood kraft pulp in the glass nonwoven fabric is not particularly limited, but it should be set at 40% in consideration of properties other than punching processability.
Preferably, it is expressed as % by weight. Furthermore, hardwood kraft pulp may be used in combination with other cellulose fibers such as softwood kraft pulp. Function Hardwood kraft pulp has a fiber length of 0.5 to 2 mm.
In short, it is obtained from trees such as beech and birch. As a result of extensive studies on other cellulose fibers such as vascular fibers such as bamboo and Manila hemp, bast fibers such as flax, hemp, and mitsumata, and wood fibers such as softwood, we found that using hardwood kraft pulp is the most suitable for punching. The properties were good. The glass nonwoven fabric used in the present invention is produced by mixing hardwood kraft pulp with glass fibers cut into appropriate lengths, dispersing the mixture in water, and forming it onto a running net. As mentioned above, hardwood kraft pulp has a short fiber length, and therefore has good dispersibility during paper making, and can provide a paper-like glass nonwoven fabric with good texture. As a result, it is presumed that the punching workability of a laminate using this improves. If the length of cellulose fibers to be mixed is short, the initial strength of the glass nonwoven fabric tends to be weakened, but if pre-treated with melamine resin, low condensation type phenolic resin, etc., the subsequent thermosetting properties will be improved. Can be used for resin impregnation and molding without any problems. However, the content of hardwood kraft pulp is 10
When the amount is less than % by weight, the strength of the glass nonwoven fabric decreases, making it unusable for practical use, and even if a laminate can be formed, the punching processability is not improved. On the other hand, if the content of hardwood kraft pulp is high, there will be no problem in terms of punching workability of the laminate, but other properties
That is, in consideration of dimensional stability, moisture resistance properties, etc., it is desirable to keep the content to 40% by weight or less, and in this case, dimensional stability and moisture resistance properties equivalent to those of glass cloth base material laminates can be obtained. Examples Glass fibers constituting the glass nonwoven fabric include:
E-glass fibers are commonly used, but glass fibers of other compositions with excellent electrical properties may also be used. Also,
Glass fibers may be produced by any method, such as cutting long fibers into appropriate lengths by melt spinning, or directly converting molten glass into short fibers by centrifugation or blowing. In addition to epoxy resins, the thermosetting resins used are those normally used for laminated boards. Next, examples of the present invention will be described. The various glass nonwoven fabrics shown in Table 1 are used as base materials, and after pretreatment with melamine resin (resin impregnation amount at this time is 5% by weight), epoxy resin is impregnated so that the resin impregnation amount is 60% by weight, and dried. and obtained prepreg. This prepreg is layered at a temperature of 160℃ and a pressure of
Heat and pressure mold for 30 minutes at 40Kg/ ^cm2 , and the thickness
A 1.6 mm glass nonwoven epoxy resin laminate was used.
Although this laminate does not have metal foil pasted on its surface, the same applies even if metal foil is pasted on the surface.

【table】

[Table] Table 2 shows the presence or absence of nonwoven fabric breakage during molding of the laminates using each of the glass nonwoven fabrics as a base material, and the properties of the laminates. For the laminates of Comparative Example 1 and Conventional Example 2, property tests were not conducted because the nonwoven fabric broke significantly during molding and normal laminates could not be obtained. In Table 2, the punching property is determined by the 1.0φmm pin.
Room-temperature punching was performed using a mold with 10 holes arranged at a 2.54 mm pitch, and the presence or absence of cracks between the holes was examined (mold clearance was 0.05 mm). The dimensional change rate is E-
The amount of dimensional change in the length direction after the 0.5/150 treatment was calculated using the following formula (specimen size is 50 x 200 mm). Dimensional change rate = (dimensions upon receipt) - (E-0.5
/150 Dimensions after treatment) / (Dimensions upon receipt) × 100 Moisture-resistant insulation conforms to JIS-C-6481. The amount of warpage is the amount of warpage after E-0.5/150 treatment according to JIS-C.
−6481 (test piece size is 300×
300mm).

[Table] Effects of the Invention As is clear from Table 2, the present invention has better punching properties than a laminate made of glass nonwoven fabric as a base material mixed with only softwood kraft pulp, and also has less warpage. Because punching performance is improved,
When applied to printed wiring, it can sufficiently cope with the increase in packaging density in recent years, and its other characteristics are also good, so its industrial value is extremely large.

Claims (1)

[Scope of Claims] 1. A laminate made by impregnating a thermosetting resin into a sheet-like base material and stacking them and forming them under heat and pressure, in which glass fiber is mixed with 10% by weight or more of hardwood kraft pulp as the base material. A laminate board characterized by using nonwoven fabric. 2. The laminate according to claim 1, wherein the glass nonwoven fabric has a hardwood kraft pulp content of 10 to 40% by weight.