JPH07240578A - Manufacture of substrate for high-frequency circuit - Google Patents

Abstract

PURPOSE:To improve the dimensional stability of a substrate for high-frequency circuit by forming it from a porous sheet of ultrahigh molecular weight sandwiched between resin-impregnated reinforcing sheets and hardened by heat under pressure. CONSTITUTION:A reinforcing sheet having a fiber base 2 impregnated with thermosetting resin 3 is attached to each side of a porous sheet 1 of ultrahigh molecular weight polyethylene. This laminate is heated and pressed to cure the resin, is cooled to a room temperature, and is heated to a temperature above Tg point of the resin without applying pressure and then cooled. Then, a metal conductor 4 with an adhesive layer 5 is laminated, heated, and pressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for electronic equipment, and more particularly to a substrate for high frequency circuits suitable for use in a high frequency region.

[0002]

2. Description of the Related Art The frequency of signals used in the recent electronics industry and communication industry has spread from the kilohertz region to the megahertz and gigahertz regions. In general, a high frequency circuit substrate is required to have a low relative dielectric constant ε _r in order to improve the signal speed, and a low dielectric loss tangent tan δ in order to reduce loss. _A glass cloth impregnated with a resin such as polytetrafluoroethylene or polyethylene is used as a dielectric material having a low _r or a low dielectric loss tangent tan δ, and a high frequency substrate in which copper foil is laminated is generally used. There is.

A polytetrafluoroethylene-glass cloth substrate obtained by impregnating glass cloth with polytetrafluoroethylene and molding under heat and pressure is manufactured at high temperature because polytetrafluoroethylene has a high melting point and low fluidity. There is a problem that molding is required for a long time and the cost becomes high. On the other hand, the polyethylene-glass cloth substrate obtained by impregnating glass cloth with polyethylene has a drawback that the heat resistance of solder is poor because the melting point of polyethylene is low.

In order to improve these drawbacks, JP-A-3-
In Japanese Patent Application Laid-Open No. 109791 and Japanese Patent Application Laid-Open No. 3-109792, a porous sheet of ultra-high molecular polyethylene and a resin-impregnated reinforcing layer impregnated with an uncured curable resin are laminated, and heated and pressed to eliminate the porosity. At the same time, a method of manufacturing a substrate for a high frequency circuit has been proposed in which a curable resin is cured, and it has improved the heat resistance and overcomes the problems of molding.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The methods disclosed in Japanese Patent Laid-Open No. 1-109792 and Japanese Patent Laid-Open No. 3-109792 improve the heat resistance of the high-frequency circuit board and the difficulty of molding, but have a problem of large dimensional shrinkage after heating and cooling. . The present invention provides a substrate for a high frequency circuit, which has a small dimensional shrinkage after heating and cooling.

[0006]

According to the present invention, a reinforcing sheet obtained by impregnating an uncured curable resin 3 on a fiber base material 2 is placed on both sides of a porous sheet 1 of ultra high molecular weight polyethylene, and heated and pressed. After curing the uncured curable resin and cooling it to room temperature, it is reheated to a temperature not lower than the Tg point of the cured resin without being pressurized and cooled, and then the attached metal conductor 4 provided with the adhesive layer 5 is provided.
Is laminated and heated and pressed, which is a method for manufacturing a high-frequency circuit substrate (see FIG. 1).

The pores in the ultra high molecular weight polyethylene porous sheet are formed by laminating a reinforcing sheet impregnated with an uncured curable resin (hereinafter sometimes referred to as a prepreg), and heating and pressurizing the reinforcing sheet. Permeates and disappears, and at the same time becomes integrated.

Next, the cured substrate is heated to a temperature not lower than the Tg of the curable resin without being pressed and then cooled. After that, a metal conductor layer with an adhesive is further laminated on both sides and heated and pressed.
The ultra-high-molecular-weight polyethylene porous sheet used in the present invention is obtained by sintering ultra-high-molecular-weight polyethylene powder particles, joining the particles with each other by fusion bonding, and forming a sheet having a thickness of 0.5 to 5 mm. There is a continuous layer of air outside the bonded particles.

Ultrahigh molecular weight polyethylene has an average molecular weight of 1
It is preferably from 1,000,000 to 5,000,000, for example, Hi-Zex Million, Miperon (trade name of Mitsui Petrochemical Industry Co., Ltd.), Suntec (trade name of Asahi Kasei Kogyo Co., Ltd.), H.
OSTALEN, GUR (trade name of Hoechst GmbH in Germany),
HIFLEX, 1000 (trade name of Hercules Company, USA) and the like are suitable.

As a method for producing a porous sheet of ultrahigh molecular weight polyethylene, powder particles of ultrahigh molecular weight polyethylene prepared by mixing a filler on a base material such as a film or a metal belt are supplied, and the powder particles are fed by a roll or a bar. There is a method in which a porous sheet of ultra-high molecular weight polyethylene is continuously molded by shaping the particles into a uniform thickness, passing them through a heating furnace, and heating and sintering the particles. To make the surface of the porous sheet of ultra high molecular weight polyethylene smooth, the ultra high molecular weight polyethylene powder has an average particle size of 0.001 to 0.1 m.
Particularly preferred is m.

Examples of the prepreg include glass cloth, glass non-woven cloth, plastic fiber woven cloth, and non-woven cloth reinforcing material impregnated with a curable resin varnish and dried, which are usually used in the production of printed circuit boards. . As the curable resin to be impregnated, polyester resin, epoxy resin,
Examples thereof include a resin composition of a phenol resin, a melamine resin, a diallyl phthalate resin, a polyimide resin, a bismaleimide / triazine resin, a polyphenylene oxide resin or a polyphenylene sulfide PPS resin, and a crosslinkable monomer. Among these resins, polyester resins, epoxy resins, and polyimide resins having relatively low ε _r and tan δ are preferable. Epoxy resin is more preferable in terms of cost. The amount of prepreg used is 50 to 200 g / m ^2.
Is preferable, and the thickness of the reinforcing layer is preferably 30 to 200 μm.

The metal of the adhesive-attached metal conductor is a foil or plate of copper, aluminum, nickel, gold, silver, platinum or the like.
The adhesive is an epoxy resin or polyester resin adhesive, and a copper foil with an adhesive for a copper-clad laminate is preferred.

Conditions for heating and pressing the porous sheet of ultra high molecular weight polyethylene and the prepreg are usually 130 to
250 ° C., applied pressure 2 to 7.8 MPa, applied time 20 to
It is carried out for 120 minutes, and the ultrahigh molecular weight polyethylene porous sheet, the prepreg and the release film are sandwiched between the end plates and heated and pressed under uniform conditions. After cooling, peel off the release film,
A porous sheet of ultrahigh molecular weight polyethylene and a prepreg are cured to obtain an integrated substrate.

By heating the obtained substrate at a temperature not lower than the Tg point of the curable resin for 15 to 30 minutes, the strain caused by heating and pressing is eliminated. Next, an epoxy resin-based or polyester resin-based copper foil with an adhesive for a copper-clad laminate is laminated on both sides of a substrate without distortion, and the temperature is 130 to 180 ° C., the applied pressure is 2 to 7 and 8 MPa, and the application time is It is heated and pressed for 20 to 120 minutes to be integrated.

[0015]

In the present invention, the distortion of the substrate formed by heating and pressing the ultrahigh molecular weight polyethylene porous sheet and the prepreg can be removed by heating the substrate to a temperature not lower than the Tg point of the curable resin. it can. Therefore,
The size of the strain-free substrate will not shrink even if it is heated and cooled again.

[0016]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto. A porous polyethylene sheet was produced from Miperon XM220 (trade name of ultra high molecular weight polyethylene manufactured by Mitsui Petrochemical Co., Ltd.) as a raw material as described below. Miperon XM220 has an average particle size of 0.03 mm and a melting point of 13
6 ° C, bulk density 0.4 g / cm ³ , true density 0.94 / cm
^{Is 3} . 100 parts by weight of Miperon XM220 and dechlorane plus-25 (1, 2, 3, 4, 7, 8, 9, 1
0,13,13,14,14-dodecachloro-1,4,4
4a, 5, 6, 6a, 7, 10, 10a, 11, 12,
12a-dodecahydro-1,4,7,10-dimethanodibenzono (a, e) cyclooctenone, a trade name of US Occidental Chemical Company, chlorine content 65% by weight, average particle size 0.003 mm, bulk density 0.67 g / cm ³ , true density 1.9 g / cm ³ , and 100 parts by weight are mixed by a mixer and shaped into a 1.3 mm thickness on a stainless belt, and heated in a heating furnace at 180 ° C. for 15 minutes. Heat sintering was performed to obtain a filler-mixed resin porous sheet having an apparent density of 0.55 g / cm ³ .

A glass cloth having a thickness of 50 μm was coated on both sides of this sheet with a brominated bisphenol A type epoxy resin (Tg13).
(0 ° C.) through a prepreg impregnated with (resin content of 60% by weight), a triacetate film having a thickness of 38 μm is laminated, and a stainless steel end plate is used, and after heating and pressing for 90 minutes at 175 ° C. and 2 MPa, The triacetate film was peeled off by cooling while applying pressure. Then at 140 ° C for 3
It was heated in a heating furnace for 0 minutes and cooled to room temperature. After that, 40g of epoxy resin adhesive is applied to electrolytic copper foil with a thickness of 35 μm.
/ M ² Coated copper foil with epoxy resin adhesive for copper-clad laminates is laminated on both sides and a stainless steel end plate is used.
It is heated and pressurized for 30 minutes under the conditions of 5 ° C. and 2 MPa, and the thickness is 0.
A 9 mm high frequency circuit substrate was obtained.

Comparative Example 1 A filler-mixed resin porous sheet was obtained in the same manner as in the Example.
Electrolytic copper foil having a thickness of 35 μm was laminated on both sides of this sheet through the same prepreg as in the example, and a stainless steel end plate was used, and heated and pressed for 90 minutes under the conditions of 175 ° C. and 2 MPa to obtain a thickness of 0.9 mm. A high frequency circuit substrate of was obtained.

Comparative Example 2 The substrate prepared in Comparative Example 1 was heated in a heating furnace at 140 ° C. for 30 minutes and cooled to room temperature to obtain a high frequency circuit substrate having a thickness of 0.9 mm. For the substrates of Examples and Comparative Examples 1 and 2, ε
_{The r} , tan δ, the dimensional change rate, and the warpage characteristics were examined. ε _r , t
An δ was measured by a cavity resonator method at 12 GHz after removing the copper foil by etching.

As for the sled, a sample cut into 330 mm × 250 mm was allowed to stand still on a surface plate, and the portion where the sag from the surface plate was the largest was measured. Dimensional change rate is 330mm x 250
In the sample cut into mm, the reference holes were drilled inward from the four corners by 10 mm, the distance between the holes was measured, and then the copper foil was removed by etching, heated at 140 ° C. for 20 minutes, and cooled to room temperature. The interhole distance was measured again, the shrinkage amount of the interhole distance (the displacement amount per unit length) was measured, and the dimensional change rate was calculated.
The results are shown in Table 1.

[0021]

[Table 1] ────────────────────────────── Example Comparative Example 1 Comparative Example 2 ──────── ────────────────────── ε _r 2.75 2.65 2.65 tan δ (× 10 ^-4 ) 70 65 65 65 Dimensional change rate (%) 0 .04 0.12 0.05 Warp (mm) 1.0 2.3 6.8 ────────────────────────────── ─

[0022]

According to the present invention, the strain generated in the substrate by heating and pressurizing the porous sheet of ultra-high molecular weight polyethylene and the prepreg of the curable resin is reduced by the T of the curable resin.
To obtain a high-frequency circuit board with good dimensional stability, in which dimensional shrinkage is reduced even when the copper foil with adhesive is removed by heating it to a temperature of point g or higher and then bonded by heating and pressurizing. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a high-frequency circuit substrate of the present invention.

[Explanation of symbols]

 1 Porous Sheet of Ultra High Molecular Weight Polyethylene 2 Fiber Substrate 3 Curable Resin 4 Metal Conductor 5 Adhesive Layer

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

The object of the invention is to be Solved by Hei 3 -10979
The methods disclosed in Japanese Patent Laid-Open No. 1-109792 and Japanese Patent Laid-Open No. 3-109792 improve the heat resistance of the high-frequency circuit board and the difficulty of molding, but have a problem of large dimensional shrinkage after heating and cooling. . The present invention provides a substrate for a high frequency circuit, which has a small dimensional shrinkage after heating and cooling.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B32B 27/32 Z 8115-4F H05K 1/03 J 7011-4E

Claims (1)

[Claims] 1. A reinforcing sheet in which an uncured curable resin is impregnated in a fiber substrate is placed on both sides of a porous sheet of ultra-high molecular weight polyethylene, and the uncured curable resin is cured by heating and pressing at room temperature. After cooling, the substrate is reheated to a temperature not lower than the Tg point of the cured resin without being pressed and cooled, and then a metal conductor with an adhesive is laminated and heated and pressed to produce a substrate for high frequency circuit. Method.