JPS63281496A - Printed wiring board - Google Patents

Abstract

PURPOSE:To increase mechanical strength, by a method wherein a prepreg for an intermediate layer is formed by impregnating a nonwoven fabric whose main component is alumina with a specified thermosetting resin composition, and prepregs for an upper layer and a lower layer are set by impregnating a glass woven fabric with thermosetting resin having an excellent adhesive property to glass woven fabric. CONSTITUTION:A resin composition 2a containing epoxidized polybutadiene and brominated phenolic novolac type epoxy, and a thermosetting resin composition 2b having excellent adhesive property to glass woven fabric are mixed and solved in a soluvent together with hardener and promotor for hardening, to set varnish (a) and (b). A nonwoven fabric 3 whose main component is alumina is impregnated with the varnish (a), and an inorganic fibrous woven fabric 4 is impregnated with the varnish (b), to make prepregs A and B. A laminated layer 5 is formed, by using the prepreg A and the prepreg B for an intermediate layer, and an upper and lower layers, respectively. Copper foils 6 are piled on the upper and lower surfaces, and subjected to thermocompression bonding. For the resin composition 2b, various well-known resins, e.g., epoxy resin, polyimide resin, etc., are used. Thereby, dielectric characteristics are increased as compared with G-10 grade (NEMA specification), and a boilproof property and cloth adhesive property are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a printed wiring board used in various electronic devices and the like.

(Prior art) Printed wiring boards such as IC boards used in various electronic devices are manufactured by impregnating a thermosetting resin composition into a base material such as an inorganic tIk#I woven or nonwoven fabric. B-
Generally, a stage prepreg is prepared, and a metal foil is layered on the surface of a laminate made by laminating the prepreg, followed by hot-pressure molding.

By the way, printed wiring boards such as microwave IC boards that handle signals in the high frequency range have stable mechanical properties and low dielectric loss in order to increase the signal propagation speed. It is necessary that the dielectric loss tangent is small, and that the material has high thermal conductivity and good heat dissipation in order to prevent deterioration of the electrical characteristics of the substrate due to temperature rise.

In order to meet the above requirements, various improvements have been made in the structure, material, etc. of the base material and the thermosetting resin composition that constitute the printed wiring board.

That is, usually in printed wiring boards, the base material is a glass woven fabric or a non-woven fabric, and the thermosetting resin composition is an epoxy resin, a diallyl phthalate resin, a polymaleimide resin, a polyincyanate resin, a polyester resin, or one or two of these. Although it is manufactured as a mixture of the above,
The printed wiring board has a fairly high dielectric constant, therefore a large dielectric loss, and a low thermal conductivity, so it cannot be used with microwave I.
This was disadvantageous as a C substrate.

Therefore, the present inventors have developed a printed wiring board in which the base material is made of alumina-based woven fabric or non-woven fabric, for example, and the alumina content is increased to reduce dielectric loss and improve thermal conductivity. (Utility Application No. 61-50532).

Furthermore, as the thermosetting resin composition, the present inventors have proposed a thermosetting resin composition containing polybutadiene or a derivative thereof, such as a thermosetting resin composition consisting of epoxidized polybutadiene and brominated phenol novolak type epoxy. The thermosetting resin composition has a characteristic suitable as a material for microwave IC substrates, in that it has a small dielectric constant and a small dielectric loss tangent, and thus has a small dielectric loss.

However, the thermosetting resin composition containing epoxidized polybutadiene and brominated phenol novolac type epoxy has a higher viscosity in the B-stage than epoxy resin, and the surface of the resulting prepreg becomes sticky. Workability such as winding and laminating becomes worse.

In such cases, it is advantageous to use an inorganic fibrous nonwoven fabric as the base material. The nonwoven fabric tends to incorporate the impregnated resin into its interior, and the tackiness of the surface of the obtained prepreg due to the coating of the highly viscous resin can be reduced.

(Problems to be Solved by the Invention) - As explained above, by using an inorganic fibrous nonwoven fabric as a base material, it is possible to select a resin composition with a high content of highly viscous resin, such as epoxy resin. Impregnating a nonwoven fabric mainly composed of alumina with a material containing brominated polybutadiene and brominated phenol novolak type epoxy,
A printed wiring board with high dielectric properties can be obtained.

In particular, printed wiring boards such as microwave IC boards that handle high frequency signals are required to have high mechanical strength in addition to excellent dielectric properties. However, when using the above-mentioned nonwoven fabric mainly composed of alumina, the mechanical strength of the resulting printed wiring board is low because the nonwoven fabric has low strength as a reinforcing material. The substrate may be damaged, and it is difficult to make a particularly large substrate.

The present invention was made in view of the current situation, and provides a printed wiring board using a resin composition made of epoxidized polybutadiene and brominated phenol novolac type epoxy, and a base material made of a nonwoven fabric whose main component is alumina. The purpose is to solve the above-mentioned problems without any disadvantage.

(Means for Solving the Problems) As a means for solving the above problems, the prepreg constituting the intermediate layer of the laminate is made of a nonwoven fabric mainly composed of alumina, epoxidized polybutadiene and brominated phenol novolak type epoxy. The prepregs forming the upper and lower layers of the laminate are prepared by impregnating a thermosetting resin composition containing:
It is prepared by impregnating a glass woven fabric with a thermosetting resin composition that has good adhesion to the glass woven fabric.

(Function) According to the above means, prepregs made of glass woven fabric with high mechanical strength are arranged on the upper and lower layers of the laminate, so that the printed wiring board fabricated from non-woven fabric mainly composed of alumina can be manufactured. It is possible to improve the target strength.

In addition, woven glass fabric has poor wettability with a thermosetting resin composition consisting of epoxidized polybutadiene and brominated phenol novolac type epoxy, and in the present invention, the base material has adhesive properties with the woven glass fabric such as epoxy resin. Since the prepreg is prepared by impregnating the prepreg with a resin of good quality, disadvantages such as peeling of the glass woven fabric and whitening after boiling will not occur.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

The attached figure is a perspective view showing a printed wiring board according to the present invention.

As shown in the drawing, the printed circuit board l is made of a resin composition 2a containing epoxidized polybutadiene and brominated phenol novolac type epoxy, and a thermosetting resin composition 2b having good adhesion to glass woven fabric. Copper foils 6, 6 are laminated on the surface of a laminate 5 in which a nonwoven fabric 3 containing alumina as a main component is laminated, and an inorganic fiber woven fabric 4 is laminated in upper and lower layers.

To form this printed wiring board l, first, varnishes a and b are prepared by mixing and dissolving the thermosetting resin compositions 2a and 2b together with a curing agent, a curing accelerator, etc. in a solvent, and the varnish a is mixed with alumina. Prepreg A and B
Create.

Next, a laminate 5 is formed using a prepreg A having a non-woven fabric 3 as a base material as an intermediate layer and a prepreg B having a woven fabric 4 as a base material as a second lower layer. Layer 6 and 6 and apply thermocompression bonding.

Examples of the nonwoven fabric 3 include ceramic paper containing short fibers of alumina-silica as a main component.

Further, when using the resin composition 2a, by setting the average fiber diameter of the nonwoven fabric containing alumina as a main component to 6 g+n or less, a completely non-tacky prepreg can be prepared.

As the resin composition 2b, various known thermosetting resins such as epoxy resins and polyimide resins can be used.

Here, prepreg A was prepared by using ceramic paper as the nonwoven fabric 3 and glass cloth (JIS EPI8) as the woven fabric 4 on the cloth prepared with the composition shown in the table below.
, B was prepared, a printed wiring board 1 was produced, and the dielectric loss tangent, dielectric constant, cross adhesive strength, and boiling resistance were measured, and the results are also shown in the table.

In addition, as a comparative example, using the same varnish as prepreg A, ceramic paper and glass cloth (JIS EP
The properties of a printed wiring board using prepreg C1D prepared by impregnating it with 18) are also shown in the table.

The dielectric constant and dielectric loss tangent shall be measured in accordance with JIS C6481. In addition, the cross adhesive strength was measured using a tensile tester [
DC3-2000, manufactured by Shimadzu Corporation] indicates the minimum load per unit width when one surface layer of the base glass woven fabric 4 is peeled off in the right angle direction. Here, a laminate 5 on which the copper foil 6 of the obtained printed wiring board 1 was etched was cut into a width of 10 mm ± 0.5 and cut into a width of 10 mm ± 0.5. The measurements were taken by peeling it off in the same direction.

In addition, the boiling resistance is 50mmX in distilled water at a temperature of 100℃.
After immersing a 50 mm sample, it was left to stand at room temperature for 24 hours, and then evaluated by examining changes in appearance, and the time indicated is the immersion time.

As is clear from the table, the printed wiring board l of this example is, for example, G-10 grade [National Electrical Manufacturers Association (NE
MA) standard] printed wiring board dielectric constant (normal state 4.8
．． Excellent dielectric properties were obtained compared to the dielectric loss tangent (normal condition: 0.020, 0.022 after boiling), and the boiling resistance and cross adhesion were improved compared to the comparative example. Excellent.

(Effects of the Invention) As explained above, according to the present invention, the intermediate layer includes a prepreg in which a nonwoven fabric mainly composed of alumina is impregnated with a thermosetting resin composition consisting of epoxidized polybutadiene and brominated phenol novolak type epoxy. For the upper and lower layers, a laminate is formed using a prepreg made of glass woven fabric impregnated with a thermosetting resin composition that has good adhesion to the glass woven fabric, and a metal foil is layered on the laminate and heat-pressed to form printed wiring. The mechanical strength of the wiring substrate is increased compared to conventional printed wiring boards using only non-woven fabric, and large-sized printed wiring boards can also be formed. In addition, a nonwoven fabric with an average fiber diameter of 6 pm or less is used, and the resulting prepreg has no viscosity.
By impregnating a glass woven fabric with a non-viscous resin, for example, an epoxy resin, a non-viscous prepreg can also be obtained, and the workability of the laminate can be improved.

[Brief explanation of the drawing]

The accompanying drawing is a perspective view of a printed wiring board according to the present invention. In the figure, 1 is a printed wiring board, 2a is a resin composition consisting of epoxidized polybutadiene and brominated phenol novolak type epoxy, 2b is a resin composition that has good adhesion to glass woven fabric, 3 is a nonwoven fabric, and 4 is a woven fabric. , 5 is a laminate, and 6 is a copper foil.

Claims (3)

[Claims] (1) In a printed wiring board in which metal foil is layered on a laminate made of prepreg prepared by impregnating an inorganic fibrous base material with a thermosetting resin composition and then thermocompression molded, the intermediate layer of the laminate is formed. The prepregs forming the upper and lower layers of the laminate are prepared by impregnating a nonwoven fabric mainly composed of alumina with a thermosetting resin fiber composition containing epoxidized polybutadiene and brominated phenol novolac type epoxy, and the prepregs forming the upper and lower layers of the laminate are made of glass. A printed wiring board characterized in that it is prepared by impregnating a woven fabric with a thermosetting resin composition that has good adhesion to the woven glass fabric. (2) Claim 1, characterized in that the nonwoven fabric containing alumina as a main component has an average fiber diameter of 6 μm or less.
Printed wiring board as described in section. (3) The printed wiring board according to claim 1 or 2, wherein the thermosetting resin impregnated into the glass woven fabric is an epoxy resin.