JPH06125154A - Manufacture of low-permittivity printed-circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a simple process of manufacturing a mechanically strong, low-cost printed-circuit board having a low permittivity and low dielectric loss. CONSTITUTION:Thermoplastic resin material is mixed with thermoplastic resin compound that includes a curing agent and a foaming agent. The foamed thermoplastic 2a is applied between metal plates 1a, and it is hardened. Alternatively, a thermoplastic prepreg 3a, which is composed of a reinforcing base impregnated with the same resin compound, may be used together with or in place of the foamed thermoplastic 2a. It is preferable that the thermoplastic resin compound has an initial viscosity of 10000-50000cPs, and that the thermoplastic prepreg 3a contains 30-60 pts.wt. of the thermoplastic resin compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a low dielectric constant printed circuit board. INDUSTRIAL APPLICABILITY The present invention is used for manufacturing a computer using a high frequency band, a high frequency transceiver, and the like.

[0002]

2. Description of the Related Art In recent years, along with the development of information and communication technology, the number of computers and high frequency transceivers using a high frequency band has been increasing. Therefore, the printed wiring boards used for manufacturing these have also been desired to have a low dielectric constant and a low dielectric loss, which have excellent high frequency characteristics. by the way,
Examples of conventional general-purpose industrial and consumer printed wiring boards include glass-based epoxy resin laminates and paper-based phenolic resin laminates. However, these wiring boards have a relatively high dielectric constant of 4.8 and a dielectric loss of about 0.015, and are not suitable for parts such as computers and high frequency transceivers that use a high frequency band. On the contrary,
As a printed wiring board having a low dielectric constant and a low dielectric loss, a printed wiring board made of a glass cloth fluororesin material (low dielectric constant: 2.6, dielectric loss: 0.005) is known. Further, as a structure in which the structure of the substrate is changed and the dielectric constant is lowered, a porous fluororesin (Goretex) dielectric is used to form voids in the dielectric (Japanese Patent Laid-Open No. 64-42).
890), a printed circuit board using a thermoplastic resin foam for the dielectric layer (Japanese Patent Laid-Open No. 62-69580), and the like.

[0003]

However, since the substrate made of the above glass cloth fluororesin material uses the fluororesin, it is necessary to raise the temperature to 350 ° C. or higher during the molding process. Further, since the fluororesin has a high coefficient of thermal expansion,
Dimensional stability is poor and molding is difficult. Further, in the substrate using the above porous fluororesin dielectric, the dielectric constant can be suppressed to a low value of 2.0 or less, but since the structure of the void is a continuous structure and the pores are non-uniform, there is a drawback that the water absorption is high. Have Further, in the substrate in which the dielectric layer is a thermoplastic resin foam, there is no reinforcing material in the foam layer and it is made of a thermoplastic resin, so the mechanical strength is low, and in addition, heat resistance and dimensional stability, etc. There is also a problem with the characteristics of.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide a method for easily and inexpensively manufacturing a printed wiring board having a low dielectric constant and low dielectric loss and excellent mechanical strength. And

[0005]

A method of manufacturing a low dielectric constant printed circuit board (hereinafter referred to as "substrate") of the first invention is as follows.
A thermosetting resin composition obtained by mixing a thermosetting resin raw material with at least a curing agent and a foam stabilizer is stirred, and then the foamed thermosetting resin composition is foamed on a metal plate or a metal plate. It is characterized in that the foamed thermosetting resin composition is placed in between and then cured. The above-mentioned "thermosetting resin raw material" is a raw material that is cured by heating to form a substrate, and is usually composed of an oligomer. The type of the resin raw material is not particularly limited as long as the object of the present invention can be achieved, and various thermosetting resin raw materials such as epoxy resin type, polyester resin type and phenol resin type can be selected. For example, examples of the epoxy resin-based thermosetting resin material include epoxy resins such as bisphenol A epoxy resin, phenol novolac type epoxy resin, and brominated epoxy resin.

Examples of the above-mentioned "curing agent" include
Examples thereof include amine curing agents and acid anhydride curing agents. Furthermore, as the above-mentioned “foam stabilizer”, for example, a silicone-based foam stabilizer or a surfactant can be used.
However, it is preferable to select a material according to the properties of the thermosetting resin raw material and the curing agent used. For example, when a phenol novolac type epoxy resin is used as the thermosetting resin raw material and an amine type curing agent is used as the curing agent, it is preferable to select a silicone type foam stabilizer or the like. Further, as these auxiliaries, a curing agent (dicyandiamide, imidazole, etc.) and the like can be used in addition to the above curing agent and the like.

Stirring of the thermosetting resin composition can be carried out, for example, by using a stirrer such as a mixer. Then, as shown in the third aspect of the present invention, the stirring has an initial viscosity of the thermosetting resin composition of 10,000 to 50,000 cps.
It is preferable to carry out the treatment so that the degree becomes moderate. Initial viscosity is 1000
This is because when it is less than 0 cps, the foamability and stability of the thermosetting resin composition are poor, and when it exceeds 50,000 cps, the workability as a composition is poor. The initial viscosity can be adjusted by the rotation speed of the stirrer, stirring time, and the like. With the stirring, the viscosity of the composition increases, and uniform foam is generated, and the foamed thermosetting resin composition becomes stable. The foaming ratio at this time is preferably about 1.5 to 3 times in consideration of the stability of the foam and the cell size of the foam.

The metal plate-like body is not limited to a metal foil (copper foil, aluminum foil, silver foil, etc.), but includes a metal plate (copper plate, aluminum plate, silver plate, etc.). Also, its shape,
The thickness is not particularly limited as long as the object of the present invention can be achieved. In addition, the above-mentioned "disposing the composition on the metal plate-shaped body or between the metal plate-shaped bodies" means disposing the composition on the metal plate-shaped body to have a two-layer structure, or the composition being a metal plate-shaped body. In addition to the case of arranging them between them to form a three-layer structure, it also includes the case of forming a structure in which such a composition and a metal plate-like body are repeatedly laminated.

Further, as shown in the second aspect of the present invention, for the purpose of further improving the mechanical strength of the substrate, thermosetting is used in place of the foamed thermosetting resin composition or together with the foamed thermosetting resin composition. Resin prepreg can be used.
Incidentally, this thermosetting resin prepreg is a foam thermosetting resin composition, a glass woven cloth, a glass nonwoven cloth, an organic fiber woven cloth,
Not limited to a sheet-like material impregnated with a reinforcing base material such as an organic fiber nonwoven fabric, SMC in which a glass thermosetting resin composition is mixed with glass short fibers or organic short fibers, or long fibers are randomly oriented ( It may be a sheet-shaped product produced by making a fibrous product impregnated with the foamed thermosetting resin composition by a sheet molding compound method, or a bundle of the fibrous products. The amount of the foamed thermosetting resin composition impregnated into the reinforcing substrate is 30 to 30 when the whole thermosetting resin prepreg is 100 parts by weight, as shown in the fourth invention.
It is preferable to use 60 parts by weight. This is because if it is less than 30 parts by weight, the strength becomes low, and if it exceeds 60 parts by weight, it becomes difficult to obtain a low dielectric constant, which is not preferable.

As described above, this thermosetting resin prepreg is also placed on a metal plate or the like, like the foaming thermosetting resin composition. Furthermore, the foamed thermosetting resin composition and / or another thermosetting resin prepreg may be appropriately laminated and arranged between the thermosetting resin prepreg and the metal plate. The method for curing the foamed thermosetting resin composition is not particularly limited as long as the object of the present invention can be achieved. For example, by heating the thermosetting resin in the laminate comprising the foamed thermosetting resin composition (thermosetting resin prepreg) and the metal plate to start the curing reaction, and then by hot pressing as post-curing. Examples thereof include a method of completing the curing reaction. In this case, it takes about several hours (about 3 hours) to start the curing reaction, and the hot pressing is performed at a temperature of 150 to 170 ° C. and a pressure of 5 to 10 kgf.
/ Cm ² , and the pressing time is preferably about 30 to 90 minutes.

[0011]

In the substrate manufactured by using the present invention, the dielectric layer is 1
Since it is composed of a resin having uniform and fine voids (single cells) of about 5 μm, it has a low dielectric constant [dielectric constant;
When there is no reinforcing material, it is about 2.0 to 2.5, and when a reinforcing material (glass woven fabric) is used, it is 2.5 to 3.0], which results in low dielectric loss and low water absorption. Further, since this substrate is made of a thermosetting resin, it has good heat resistance and dimensional stability. Further, by using the thermosetting resin prepreg, it is possible to further improve various characteristics such as mechanical strength, heat resistance and dimensional stability of the substrate.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples. (1) Preparation of Substrate Example 1 As a thermosetting resin raw material, a phenol novolac type epoxy resin raw material (trade name "DEN438", manufactured by Dow Chemical Co., Ltd.) was prepared.
17 parts by weight of meta-xylenediamine (manufactured by Mitsubishi Gas Chemical Co., Inc.) as a curing agent with respect to parts by weight (hereinafter referred to as “part”).
As a foam stabilizer, a silicone-based foam stabilizer (trade name "L-56
14 ", manufactured by Union Carbide Co., Ltd.) was mixed in a ratio of 10 parts to prepare a thermosetting resin composition.

Then, the resin composition is mixed with a mixer (AC
M-5; manufactured by Aikosha Co., Ltd.) and stirred for 5 minutes under the condition of a rotation speed of 450 rpm, and mechanically foamed to prepare a foamed thermosetting resin composition. The expansion ratio at this time is 2.0.
Met. Further, the foamed thermosetting resin composition was cast onto a copper foil (thickness: 35 μm, manufactured by Nikko Ghoulfill Co., Ltd.), and a copper foil was further laminated thereon (three-layer structure).
And Then, this laminated product was subjected to a cooling press under the conditions of a pressing temperature of 10 ° C., a pressing pressure of 10 kgf / cm ² , and a pressing time of 3 hours, and the molding process was started. During this time, the epoxy resin raw material in the laminate started to generate heat and started the curing reaction. After that, press temperature 1 on this laminated product.
Under the conditions of 60 ° C., a pressing pressure of 5 kgf / cm ² , and a pressing time of 3 hours, hot pressing is performed to post-cure the epoxy resin raw material to complete the curing reaction of the resin raw material, and as shown in FIG. A substrate of Example 1 including the copper foil layer 1 and the foamed resin layer 2 was prepared.

Example 2 First, a foamed thermosetting resin composition similar to that of Example 1 was impregnated into a glass fiber non-woven fabric (trade name "EPM4050", manufactured by Japan Vilene Co., Ltd.) to prepare a thermosetting resin prepreg. . Then, the foamed thermosetting resin composition was used as the product No. It was poured onto a copper foil similar to that of No. 1, and the thermosetting resin prepreg was placed on the copper foil. Then, the foamed thermosetting resin composition was poured onto the prepreg, and a copper foil was further laminated thereon to form a laminated product (five-layer structure). This laminated product was subjected to cooling press and hot pressing under the same conditions as in Example 1 to post-cure the epoxy resin raw material in the laminated product, and the copper foil layer 1 as shown in FIG.
A substrate of Example 2 including a, the foamed resin layer 2a, and the prepreg layer 3a was prepared. Comparative Example The same thermosetting resin composition as in Example 1 was not foamed,
A substrate according to a comparative example was prepared in the same manner as in Example 1 except that it was cast on a copper foil.

(2) Performance Test and Evaluation The dielectric constant (ε, 1 MHz), dielectric loss tangent (tan δ), volume resistivity (Ω · cm), glass transition temperature (Tg, ° C) and The cell size (μm) of the dielectric layer was measured. The measurement of the dielectric constant and the measurement of the dielectric loss tangent are performed according to JISC 6481.
"TR-10C type dielectric loss measuring instrument (trade name, manufactured by Ando Electric Co., Ltd.)" was used. In addition, the measurement of the volume resistivity is performed according to JIS C 6481, “YHP4329A”.
(Trade name, manufactured by Yokogawa Hewlett-Packard Co.) ". Further, the cell size of the dielectric layer was measured using a scanning microscope (trade name "JXA-6100P", manufactured by JEOL Ltd.). The results of the above test (measurement) are shown in Table 1.

[0016]

[Table 1]

According to the above performance tests, in the comparative example in which the thermosetting resin composition which is not foamed is used as it is, the dielectric loss tangent (dielectric loss) is suppressed to be low, but the dielectric constant shows a high value. , Not suitable for high frequency substrates. On the other hand, Example 1 using the foamed thermosetting resin composition
Since the resin of the dielectric layer has uniform and fine voids (single bubbles) of about 1 to 2 μm, both the dielectric constant and the dielectric loss tangent showed low values. In addition, the volume resistivity and the glass transition temperature both showed good values, indicating that they were excellent in dimensional stability and thermal stability. Furthermore, in Example 2 in which the thermosetting resin prepreg was used together with the thermosetting resin composition, the dielectric constant showed a value slightly higher than that of Example 1, but a sufficient value as a substrate for high frequency. . Also,
Since the second embodiment has a predetermined prepreg, the mechanical strength, heat resistance, and dimensional stability are further improved. The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application.

[0018]

According to the manufacturing method of the present invention, it is possible to manufacture a printed wiring board having a low dielectric constant and a low dielectric loss and excellent mechanical strength. Further, according to the manufacturing method of the present invention, it is possible to easily obtain a target substrate having a low dielectric constant and a low dielectric loss even if a relatively inexpensive resin raw material (for example, an epoxy resin raw material) is used.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a printed wiring board according to a first embodiment.

FIG. 2 is a vertical sectional view of a printed wiring board according to a second embodiment.

[Explanation of symbols]

 1; Copper foil layer, 2; Foamed resin layer, 3a; Flip prep layer

Claims (4)

[Claims] 1. A thermosetting resin composition in which a thermosetting resin raw material is mixed with at least a curing agent and a foam stabilizer, and then the foamed thermosetting resin composition is foamed on a metal plate. Alternatively, a method for producing a low dielectric constant printed circuit board is characterized in that it is arranged between metal plate-like bodies and then the foamed thermosetting resin composition is cured. 2. A thermosetting resin composition in which a thermosetting resin raw material is mixed with at least a curing agent and a foam stabilizer, and then foamed, and the foamed thermosetting resin composition and the foamed thermosetting resin. At least the thermosetting resin prepreg of the thermosetting resin prepreg in which the reinforcing resin composition is impregnated into the reinforcing substrate is disposed on or between the metal plate-like bodies,
Next, a method for producing a low dielectric constant printed circuit board, which comprises curing the thermosetting resin composition. 3. The initial viscosity of the thermosetting resin composition is
The method for producing a low dielectric constant printed circuit board according to claim 1 or 2, wherein the production rate is 10,000 to 50,000 cps. 4. The content of the thermosetting resin composition in the thermosetting resin prepreg is 30 to 60 parts by weight based on 100 parts by weight of the entire thermosetting resin prepreg. Manufacturing method of low dielectric constant printed circuit board.