JPH07245456A - High-frequency circuit board - Google Patents

Abstract

PURPOSE:To enable a high-frequency circuit device to be less thermally expanded at heating and less contracted in dimensions on cooling by a method wherein sheets of ultra-high molecular weight polyethylene in which curing resin is dispersed and cured curing resin-impregnated reinforcing layers are alternately laminated, and furthermore metal conductor layers are provided. CONSTITUTION:Ultra-high molecular weight polyethylene porous sheets 11 and prepregs impregnated with uncured curing resin are alternately laminated so as to make reinforcing sheets 13 located outside, and a metal conductor layer 14 is provided to both the outmost sides of a laminate composed of porous sheets 11 and the prepregs. The laminate provided with the conductor layers 14 are thermocompressed so as to enable the uncured hardening resin contained in the prepreg to penetrate into porosities and to be cured. As mentioned above, reinforcing materials are provided not only to the surfaces of a high-frequency circuit board but also inside the circuit board, whereby the ultra-high molecular weight polyethylene porous sheet 11 large in thermal expansion and contraction in dimensions on cooling is restricted in its behaviors by the additionally provided reinforcing materials to make the high-frequency circuit board small in thermal expansion and contraction on cooling. By this setup, a high-frequency circuit board excellent in reliability of through-hole conduction and dimensional stability can be obtained.

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 kHz region to the MHz and GHz regions. Generally, high frequency circuit boards are
In order to improve the signal speed, the relative permittivity ε _r of the substrate is lowered, and the dielectric loss tangent tan δ is further reduced in order to reduce the loss.
Is required, and the relative permittivity ε _r and the dielectric loss tangent t are required.
A glass cloth impregnated with a resin such as polytetrafluoroethylene or polyethylene is used as a dielectric having a low an δ, and a high frequency substrate in which copper foil is laminated is generally used.

A polytetrafluoroethylene-glass cloth substrate obtained by impregnating glass cloth with polytetrafluoroethylene and molding under heat and pressure has a high melting point and low fluidity of polytetrafluoroethylene. There is a problem that it takes 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, the adhesive layer 5 is formed by interposing the porous sheet 1 of ultrahigh molecular weight polyethylene and the metal conductor layer 4 with the layer composed of the reinforcing base material 2 and the curable resin 3 interposed therebetween.
A high-frequency circuit board that has been bonded and integrated with a substrate was proposed (Fig.
reference).

[0005]

However, a high-frequency circuit in which a porous sheet 1 of ultra-high molecular weight polyethylene and a metal conductor layer 4 are bonded and integrated via a layer composed of a reinforcing base material 2 and a curable resin 3 The substrate for use has a problem that it has a large thermal expansion when heated and a large dimensional shrinkage after cooling. The present invention is
It is intended to provide a substrate for a high-frequency circuit, which has a small thermal expansion during heating and a small dimensional contraction after cooling.

[0006]

According to the present invention, a sheet 11 comprising a curable resin dispersed in ultra-high molecular weight polyethylene is used.
Is a laminated body of the cured resin-impregnated reinforcing layer 13 and the metal conductor layer 14 are further provided (see FIG. 1). The high frequency circuit substrate of the present invention comprises a plurality of ultra-high molecular weight polyethylene porous sheets 11 alternately stacked with prepreg impregnated with an uncured curable resin, and the reinforcing sheet 1 on the outside.
3 and the metal conductor layer 14 is provided on the outermost side,
It can be manufactured by heating and pressurizing this to infiltrate the uncured curable resin contained in the prepreg into the pores of the porous sheet to cure it.

The ultra-high molecular weight polyethylene porous sheet is obtained by sintering ultra-high molecular weight polyethylene powder particles, bonding the particles by fusion and molding them into a sheet having a thickness of 0.5 to 5 mm. There is a continuous layer of air between the bonded particles.

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

As a method for producing a porous sheet of ultra-high molecular weight polyethylene, powder particles of ultra-high 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 ultrahigh molecular weight polyethylene is continuously formed 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, which are usually used in the production of printed circuit boards. . As the curable resin to be impregnated, polyester resin, epoxy resin,
Examples of the resin composition include 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 resin, and a crosslinkable monomer. Preferred are polyester resins, epoxy resins, and polyimide resins having relatively low ε _r and tan δ. Epoxy resin is more preferable in terms of cost. The amount of prepreg used is preferably 50 to 200 g / m ² , and the thickness of the reinforcing layer is preferably 30 to 200 μm.

The metal conductor layer is a foil or plate of copper, aluminum, nickel, gold, silver, platinum or the like. Further, instead of the metal foil or the plate, a predetermined circuit may be formed by plating. The thickness of the conductor layer is usually 10 to 50 μm
Is.

The conditions for heating and pressing the ultrahigh molecular weight polyethylene sheet and other constituent materials are usually 130 to 250.
C, applied pressure 2-7, 8 MPa, application time 20-120
The ultrahigh molecular weight polyethylene porous sheet, the prepreg, and the metal conductor are sandwiched between end plates, and heated and pressed under uniform conditions.

[0013]

In the present invention, the reinforcing base material is provided not only on the surface layer of the high-frequency circuit substrate but also inside the substrate, so that the behavior of the ultra-high molecular weight polyethylene porous sheet layer having a large degree of thermal expansion and dimensional contraction after cooling is large. The newly provided reinforcing base material restrains. Good thermal conductivity and dimensional stability can be obtained because thermal expansion and dimensional contraction after cooling are reduced.

[0014]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto. Example 1 A porous polyethylene sheet was produced from Miperon XM220 (trade name of ultra-high molecular weight polyethylene manufactured by Mitsui Petrochemical Industry Co., Ltd.) as a raw material as described below.
Miperon XM220 has an average particle diameter of 0.03 mm, a melting point of 136 ° C., a bulk density of 0.4 g / cm ³ , and a true density of 0.94 /.
It is cm ³ . 100 parts by weight of Miperon XM220, dechlorane plus-25 (1, 2, 3, 4, 7, 8, 9,
10,13,14,14-dodecachloro-1,4,4
a, 5, 6, 6a, 7, 10, 10a, 11, 12, 1
2a-dodecahydro-1,4,7,10-dimethanodibenzono (a, e) cyclooctenone, a trade name of Oxydental Chemical Co., USA, chlorine content 65% by weight, average particle diameter 0.003 mm, bulk density 0 0.67 g / cm ³ , true density 1.9 g / cm ³ ) 100 parts by weight are mixed by a mixer and shaped into a thickness of 0.6 mm on a stainless belt,
The mixture was heated and sintered in a heating furnace at 180 ° C. for 15 minutes to obtain a filler-mixed resin porous sheet having an apparent density of 0.55 g / cm ³ .

Alternately with these two sheets, a glass cloth having a thickness of 50 μm was coated with brominated bisphenol A type epoxy resin (Tg
(130 ° C) Impregnated with 3 sheets of prepreg (resin content 60% by weight), 35 μm electrolytic copper foil (Furukawa Circuit Foil Co., Ltd.) is further laminated on the outermost side, and a stainless steel end plate is used at 175 ° C. 9 at 2 MPa
It was heated and pressed for 0 minutes to obtain a substrate for high frequency circuit.

Comparative Example 1.3 mm on a stainless belt as in the example.
It was shaped into a thickness to obtain a filler-mixed resin porous sheet having an apparent density of 0.55 g / cm ³ . The same prepreg used in the examples was overlaid on both sides of this sheet, 35 μm of electrolytic copper foil was further overlaid on the outermost side, and heated and pressed in the same manner as in the example to obtain a substrate for a high frequency circuit.

JIS C50 is used for the above high frequency circuit substrate.
Drilled in conformity with the test pattern according to No. 12, and using electroless copper plating solution CUST (trade name of Hitachi Chemical Co., Ltd.), after plating with a thickness of 0.5 μm, copper sulfate electroplating with a thickness of 30 μm Then, a sample plated with through holes was obtained. For this sample,
Immerse it in oil at 260 ° C for 10 seconds and put it in water at room temperature for 10 seconds.
A thermal shock test was conducted in which the operation of soaking for one second was one cycle.

Further, the copper foils of the substrates obtained in Examples and Comparative Examples were removed by etching, and a thermomechanical analyzer TM manufactured by DuPont was used.
The amount of thermal expansion (the amount of displacement per unit thickness) in the thickness direction from room temperature to 260 ° C. was measured by A. ε _r , tan
δ was measured by a 12 GHz cavity resonator method.

The substrates obtained in the examples and the comparative examples are 330 mm ×
After cutting into 250 mm, drilling reference holes from the four corners to the inside of 10 mm, measuring the distance between the holes, etching away the copper foil, heating at 140 ° C. for 20 minutes, cooling 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. The result of the thermal shock test is the number of cycles until the conduction resistance between the through holes changes by 20% or more. Comparing the example and the comparative example, ε _r and tan δ slightly increase by 1.5 times due to thermal shock,
It can be seen that the dimensional change rate is halved.

[0020]

[Table 1] ──────────────────────────────── Examples Examples Comparative Examples ─────────── ────────────────────── Thermal shock test (number of cycles) 60 40 Thermal expansion (%) 10 12 ε _r 2.75 2.65 tan δ (× 10 ^-4 ) 75 65 Dimensional change rate (%) 0.05 0.12 ─────────────────────────────────

[0021]

According to the present invention, since the reinforcing base material is provided not only in the surface layer of the substrate but also in the substrate, the thermal expansion of the substrate and the dimensional contraction after cooling are reduced. Thus, it is possible to obtain a high-frequency circuit board having good dimensional stability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a high-frequency circuit board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a conventional high-frequency circuit board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Porous sheet of ultra-high molecular weight polyethylene 2 Reinforcing base material 3 Curable resin 4 Metal conductor layer 5 Adhesive layer 11 Sheet in which curable resin is dispersed in ultra-high molecular weight polyethylene 13 Cured curable resin impregnated reinforcing layer 14 Metal conductor layer

Claims (1)

[Claims] 1. A plurality of sheets in which a curable resin is dispersed in ultra-high molecular weight polyethylene are alternately laminated with a cured curable resin-impregnated reinforcing layer, and a metal conductor layer is further provided. Characteristic high frequency circuit board.