JPH11100767A - Base material for laminate board and its production, and prepreg and laminate board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the curvature and distortion of a laminate board using a glass fiber nonwoven fabric as a base material. SOLUTION: A glass fiber nonwoven fabric produced by blending glass fibers with thermoplastic resin fibers having a softening point of 220 deg.C, such as meta- aramide fibers, is used as a base material to produce a laminate board. In the glass fiber nonwoven fabric, the fibers are bound to each other with a resin binder, and the thermoplastic fibers are fused with the glass fibers. The content of the thermoplastic resin fibers having a softening point of >=220 deg.C is preferably 5-30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base material for a laminated board comprising a mixed nonwoven fabric comprising glass fibers and a thermoplastic resin fiber having a softening temperature of 220.degree.
The present invention also relates to a prepreg and a laminate using the laminate substrate. This laminated board is suitable as an insulating substrate of a printed wiring board on which leadless chip components such as resistors and ICs are surface-mounted.

[0002]

2. Description of the Related Art Conventionally, as an insulating substrate of a printed wiring board to be incorporated in an electronic device, a laminated board obtained by heating and pressing a prepreg layer formed by impregnating and drying a thermosetting resin in a sheet-like base material is used. I have. As a sheet-like base material used in the production of the laminate, there is a glass fiber nonwoven fabric in which glass fibers are formed and the fibers are bound with a binder such as an epoxy resin. However, when a laminated board is manufactured using a glass fiber nonwoven fabric as a base material, there is a problem that warpage and twist of the laminated board are increased. As a solution to this problem, there have been proposed techniques such as forming a nonwoven fabric by mixing cellulose fibers with glass fibers, and increasing the heat resistance of a binder resin that binds the glass fibers.

[0003]

However, the above solutions are still insufficient. A laminated board using a conventional glass fiber nonwoven fabric as a base material is liable to be warped and twisted after molding or processing into a printed wiring board. The thermosetting resin impregnated in the base material melts and flows due to heat and pressure during the formation of the laminate. Further, the melting temperature of the thermosetting resin impregnated in the base material (8
(0 to 140 ° C.) is close to or exceeds the glass transition temperature of the resin binder binding the glass fibers, so that the resin binder softens and the binding between the glass fibers is loosened. At this time, the loosely bound glass fibers are deformed non-uniformly by the flow of the resin. This causes warpage and twist. Furthermore, when a laminate (metal-foil-clad laminate) based on the above-mentioned conventional glass fiber nonwoven fabric is processed into a printed wiring board, and a leadless chip component is soldered by a surface mounting method, heat of 200 ° C. or more is required. It takes. At this time, the substrate does not expand and contract uniformly as a whole, but exhibits an uneven behavior in which the substrate partially expands and contracts. It has also been found that this is the cause of warpage and torsion of the printed wiring board.

[0004] The problem to be solved by the present invention is to suppress warping and twisting of a laminate (including a metal foil-clad laminate) based on a glass fiber nonwoven fabric. Another object is to provide a substrate (glass fiber nonwoven fabric) for such a laminate.

[0005]

The base material for a laminated board according to the present invention is a glass fiber non-woven fabric made mainly of a thermoplastic resin fiber having a softening temperature of 220 ° C. or higher such as glass fiber and meta-aramid fiber. . In order to solve the above-mentioned problems, the fibers are bonded with a resin binder, and the thermoplastic resin fibers or the thermoplastic resin fibers are fused to glass fibers. Here, the term “for laminate” includes the following uses (1) and (2) in its concept. (1) A use in which a laminated board is manufactured by impregnating a thermosetting resin and molding under heat and pressure. (2) In a multilayer printed wiring board having printed wirings on an inner layer and a surface layer via an insulating layer, a use in which a thermosetting resin is impregnated to form the insulating layer.

[0006] The base material for a laminate according to the present invention can be manufactured as follows. That is, a glass fiber and a thermoplastic resin fiber having a softening temperature of 220 ° C. or more, such as a meta-aramid fiber, are mixed and formed into a paper, and the fiber is bonded to form a mixed glass fiber nonwoven fabric. This is a manufacturing method in which the thermoplastic resin fibers are heated and fused at a temperature equal to or higher than the temperature at which the thermoplastic resin fibers soften, and then the thermoplastic resin fibers are mutually fused or the thermoplastic resin fibers are thermally fused to glass fibers. The term “thermal fusion” refers to at least one of a state in which the thermoplastic resin fibers are melted by heating and further fused by compression, and a state in which the thermoplastic resin fibers are softened by heating, deformed by compression, and entangled.

[0007] The prepreg according to the present invention is obtained by impregnating and drying the above-mentioned base material for a laminate with a thermosetting resin. The laminate is obtained by subjecting a layer of the prepreg to heat and pressure. . When a plurality of prepregs are stacked and heated and pressed, at least one prepreg is a prepreg according to the present invention. Here, the laminated board is the following (1) to
The concept of (3) is included in the concept. (1) A laminated plate formed by heating and pressing one or more prepregs. (2) The metal-foil-clad laminate according to the above (1), wherein the metal foil is integrated on the surface by heat and pressure molding. (3) A multilayer printed wiring board having printed wiring on an inner layer and a surface layer via an insulating layer formed by heating and pressing a prepreg.

[0008] The base material for a laminated board according to the present invention is formed of a thermoplastic resin fiber having a softening temperature of 220 ° C or higher or a fusion of the thermoplastic resin fiber to a glass fiber (entanglement) in addition to the resin binder. Is bound.
Even when the resin binder is softened during the formation of the laminate and the binding between the fibers in the portion is loosened, the binding between the fibers by the fusion (entanglement) is maintained without loosening.
As a result, even when the thermosetting resin impregnated in the base material is melted and flows by the heat and pressure during the formation of the laminated board, the binding of the fibers constituting the base material is maintained, and the base material is not impregnated. Uniform deformation is suppressed. Similarly, laminate (metal foil-clad laminate)
Even when the leadless chip component is soldered to the printed wiring board processed by using the surface mounting method, the behavior of the substrate unevenly expanding and contracting is suppressed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A nonwoven fabric made of a thermoplastic resin fiber having a softening temperature of 220 ° C. or higher and glass fiber, wherein the fibers are bound with a resin binder (water-soluble epoxy resin), and the thermoplastic resin fibers or The thermoplastic resin fiber is thermally fused to the glass fiber. Alternatively, the thermoplastic resin fibers deformed by thermal softening or the thermoplastic resin fibers deformed by thermal softening are entangled with glass fibers. The content of the thermoplastic resin fiber is preferably as large as possible from the viewpoint of ensuring the binding between the fibers and suppressing warpage and torsion, and is preferably as small as possible from the viewpoint of the heat resistance of the laminate. The content of the thermoplastic resin fiber is preferably 5 to
30% by weight. Further, the content of the resin binder is 5 to
It should be 15% by weight. 5% by weight resin binder content
Is a content that should be taken into consideration when imparting sufficient strength to the nonwoven fabric when introducing the nonwoven fabric to the heat fusing step, since the smaller the content, the weaker the binding between the fibers. The content of the resin binder of 15% by weight is a content to be taken into consideration, since if it is too large, the fibers will adhere to the heat roll or the nonwoven fabric will break in the heat fusion step using the heat roll. Thermoplastic resin fibers having a softening temperature of 220 ° C. or higher include meta-aramid fibers (for example, m-phenylene isophthalamide fibers), polyester fibers represented by polyethylene terephthalate fibers and polybutylene terephthalate fibers, and nylons represented by 6 and 66. The fibers are not particularly limited as long as they are thermoplastic resin fibers having a softening temperature of 220 ° C. or higher. The thermoplastic resin fibers having a softening temperature of 220 ° C. or higher are preferably undrawn. The term “unstretched” also includes those with a small degree of stretching.
If the thermoplastic resin fiber having a softening temperature of 220 ° C. or higher is not drawn, it can be easily fused or entangled by a hot roll.

The laminate is manufactured using the above-mentioned glass fiber nonwoven fabric as a base material. First, a prepreg is manufactured by impregnating and drying a glass fiber nonwoven fabric with a thermosetting resin such as an epoxy resin commonly used for an electric insulating laminate. Then, one or a plurality of the pre-legs are stacked and heated and pressed. Usually, a metal foil is superimposed on the surface and molded by heating and pressing to obtain a metal foil-clad laminate. When a plurality of prepregs are stacked and molded, prepregs obtained by impregnating and drying a thermosetting resin in another base material may be combined. The other substrate is, for example, a laminate substrate including a woven or non-woven fabric of glass fiber woven fabric or synthetic resin fiber.

An embodiment of the invention of a mixed nonwoven fabric comprising glass fibers and meta-aramid fibers is as follows. The glass fiber has a fiber diameter of about 9 μm and a fiber length of 9 to 15
mm is desirable. The length of the meta-aramid fiber is preferably longer in order to increase the number of fused or entangled portions. However, in consideration of improving the dispersibility of the fiber during papermaking, the shorter the better, the better. Furthermore, as the meta-aramid fiber, a fibrillated fiber and a non-fibrillated chop fiber can be used. When the chopped fibers are used, the porosity of the formed nonwoven fabric is larger than when the fibrillated fibers are used, so that the nonwoven fabric has good resin impregnating property when manufacturing a laminate. Therefore, the use of chopped meta-aramid fibers is preferred from the viewpoint of improving the moisture-resistant insulation of the laminate. For the fusion of meta-aramid fibers or the fusion of meta-aramid fibers to glass fibers, a thermal fusion method is employed. That is, the formed mixed nonwoven fabric (the fibers are already bound with a resin binder) is passed through a hot roll, and heated at a temperature at which the meta-aramid fiber softens but does not adhere to the hot roll, and is also compressed. Thereby, the meta-aramid fibers or the meta-aramid fibers are thermally fused to the glass fibers. Further, even if the complete heat fusion does not occur, the meta-aramid fibers deformed by the above operation or the meta-aramid fibers deformed by the above operation are entangled with the glass fiber. Heat roll, 280-350 ° C
Is suitable, and a linear pressure setting of 150 to 250 kgf / cm is suitable. The temperature of the hot roll of 280 ° C. is a temperature to be considered when softening and fusing the meta-aramid fiber, and the same 350 ° C. causes the softened or molten meta-aramid fiber to adhere to the hot roll to improve workability. This is the temperature that should be taken into account in preventing the temperature from lowering. When the softened or melted meta-aramid fiber adheres to the heat roll, care must be taken because the nonwoven fabric breaks during the fusing operation, or the fiber adhered to the heat roll causes irregularities on the surface of the nonwoven fabric, resulting in uneven thickness. The compression is performed tangentially between a pair of heat rolls.
The linear pressure is a pressure per roll width of 1 cm. The nonwoven fabric needs to obtain a predetermined amount of heat when passing through the heat roll, and its moving speed is preferably 10 m / min or less, but is not particularly limited.

[0012]

【Example】

Examples 1 to 7, Conventional Example Glass fiber (fiber diameter: 9 μm, fiber length: 13 mm, manufactured by Nippon Electric Glass) and chopped meta-aramid fiber (fiber diameter:
3 denier, fiber length: 6 mm, softening temperature: 280 ° C, Teijin's “Cornex”, unstretched), and water-soluble epoxy resin (glass transition temperature 110 ° C) as a resin binder
And dried by heating to form a glass fiber nonwoven fabric having a unit weight of 60 g / m ² . Table 1 shows the content of each of the glass fiber, meta-aramid fiber, and resin binder in the nonwoven fabric. This nonwoven fabric is heated with a heat roll (temperature 3
At a temperature of 200 ° C. and a linear pressure of 200 kgf / cm), the meta-aramid fiber was heat-sealed. The laminate substrate thus manufactured is impregnated with a brominated bisphenol A type epoxy resin varnish and dried to prepare a prepreg having a resin adhesion amount of 50% by weight. Was placed and a copper-clad laminate having a thickness of 0.5 mm was obtained by heating and pressing. Table 1 shows the measurement results of the warp, the moisture-proof insulation property, and the solder heat resistance of the copper-clad laminates in Examples 1 to 7 and the conventional example. The measuring method and measuring conditions of each characteristic are as follows. Warpage: A sample is placed on a flat surface, and the amount of lifting from the flat surface is measured at eight points on the four sides of the sample, and the maximum value is defined as the warpage. The warpage after molding of the copper-clad laminate (indicated as “after molding” in the table) was measured at a size of 500 × 500 mm (○: warpage was less than 3 mm, ×: warpage was 3 mm or more, Δ: × was 10%). %Less than). The copper-clad laminate was processed into a printed wiring board, and the warpage (represented as “after heating” in the table) after reflow treatment at a maximum temperature of 230 ° C. for surface mounting of components was measured at a size of 50 × 70 mm (（: Warpage is less than 2 mm, ×: Warpage is 2 mm or more, Δ: × ratio is 10% or less. Moisture resistance insulation properties: The insulation resistance after 6 hours of pressure cooker was measured. Solder heat resistance: The normal sample was floated in a 300 ° C. solder bath to check for abnormalities on the surface (表面: no abnormality, ×: blistering).

[0013]

[Table 1]

[0014]

As described above, since the base material for a laminate according to the present invention is a glass fiber nonwoven fabric, the fibers are firmly bound to each other. In this case, the warp and twist can be suppressed to a small value. As is clear from Table 1, when the content of the thermoplastic resin fiber having a softening temperature of 220 ° C. or more in the glass fiber nonwoven fabric is 10% by weight or more, the effect of suppressing warpage and twist becomes more remarkable. As is clear from Table 1, when the content of the thermoplastic resin fiber having a softening temperature of 220 ° C. or higher in the glass fiber nonwoven fabric is set to 30% by weight or less, the laminate has excellent moisture resistance and solder heat resistance. When the content is 25% by weight or less, solder heat resistance becomes more remarkable.

Claims (7)

[Claims] 1. A mixed nonwoven fabric comprising glass fibers and a thermoplastic resin fiber having a softening temperature of 220 ° C. or higher as main components, wherein the fibers are bound by a resin binder, and the thermoplastic resin fibers or the thermoplastic resin are bonded to each other. A substrate for a laminate, wherein the fibers are fused to glass fibers. 2. The laminated board substrate according to claim 1, wherein the content of the thermoplastic resin fiber having a softening temperature of 220 ° C. or higher is 5 to 30% by weight. 3. The laminate substrate according to claim 1, wherein the content of the thermoplastic resin fiber having a softening temperature of 220 ° C. or higher is 10 to 25% by weight. 4. The substrate for a laminate according to claim 1, wherein the thermoplastic resin fiber having a softening temperature of 220 ° C. or higher is a meta-aramid fiber. 5. A nonwoven fabric made of glass fibers and a thermoplastic resin fiber having a softening temperature of 220 ° C. or higher as a main component, and heated at a temperature not lower than the temperature at which the thermoplastic resin fibers soften. By compressing together,
A method for producing a base material for a laminated board, wherein the thermoplastic resin fibers or the thermoplastic resin fibers are thermally fused to glass fibers. 6. A prepreg obtained by impregnating and drying a thermosetting resin on a sheet-like substrate, wherein the sheet-like substrate is the laminate substrate according to any one of claims 1 to 4. Prepreg to do. 7. A laminate, wherein a prepreg obtained by impregnating and drying a thermosetting resin on a sheet-like base material is heated and pressed, and the prepreg is the prepreg according to claim 6.