JPH0157643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a printed circuit board using a thermoplastic resin as a base material. More specifically, the present invention relates to a method for manufacturing a heat-resistant printed circuit board, which can produce a printed circuit board in which an insulating material substrate made of aromatic polyamide resin or aromatic polyimide resin and copper foil are integrated in the atmosphere. .

[Conventional technology]

Traditionally, rigid printed circuit boards have been made of a thermosetting resin such as glass epoxy resin or epoxy-modified addition polyimide resin, with metal foil such as copper foil integrally molded onto the surface of this base material. There is.

However, glass epoxy resins have poor heat and flame retardant properties, and epoxy-modified addition polyimide resins have drawbacks such as gas generation during chemical reactions and crosslinking, making them unreliable as printed circuit boards for electrical materials. It was hot.

Therefore, it is desirable to use a material with excellent heat resistance and mechanical properties as the base material for printed circuit boards. However, when such a material is used as the base material, metal foil such as copper foil may be coated on the surface of the base material. A problem arises in the integral molding process.

That is, when the thermosetting resin in the prior art is used as a base material, the molding temperature for integrally molding a metal foil such as copper foil on the surface of the base material is at a low temperature of about 150 to 220 °C. The problem of oxidation was not so pronounced.

However, when a material with excellent heat resistance, mechanical properties, etc. is used as a substrate base material, a high molding temperature is required in order to integrally mold the material with metal foil without a chemical reaction. In molding, the problem of oxidation of metal foils such as copper foils becomes noticeable, making it difficult to manufacture desired products.

Such problems can be solved by performing the above-mentioned molding in a non-oxidizing atmosphere such as a nitrogen atmosphere, but it is not always necessary because the atmosphere needs to be constantly adjusted and atmosphere adjustment is expensive. It's hard to say it's a good solution to the problem.

[Purpose of the invention]

In view of the above situation, the present inventors have arrived at the present invention as a result of intensive research. That is, the object of the present invention is to produce printed circuit boards made of aromatic polyamide resin or aromatic polyimide resin as a base material and having excellent heat resistance and mechanical properties at low cost in the atmosphere without oxidizing the copper foil. An object of the present invention is to provide a method for manufacturing a heat-resistant printed circuit board.

[Structure of the invention]

The manufacturing method of the present invention includes a substrate preformed by heating and pressing aromatic polyamide resin powder or aromatic polyimide resin powder, a copper foil, and a substrate having a thickness of 0.1 to 4 mm.
mm polytetrafluoroethylene resin sheets are stacked in this order and inserted into the mold with a slight gap formed between the outer peripheral surface of the substrate and the inner wall of the mold. A polytetrafluoroethylene resin sheet is melt-cast by heating and pressurizing at a temperature of ℃ or above to cover the surface of the copper foil and its outer circumferential surface, thereby forming an integrated molded product of the copper foil on the substrate, which seals the copper foil from the atmosphere. Then, the polytetrafluoroethylene resin is removed from the substrate-copper foil integrated molded product.

The aromatic polyamide resin and aromatic polyimide resin used in the present invention both have a softening point.
It has a temperature of 270℃ or higher, and has the characteristic that no special chemical reactions or crosslinking occur during molding. Examples of the aromatic polyamide resin include polymetaphenylene isophthalamide, and examples of the aromatic polyimide resin include "Polyimide 2080" (trade name) commercially available from Updillon Co., Ltd., with polymetaphenylene isophthalamide being particularly preferred.

Polymetaphenylene isophthalamide has the following characteristics and is optimal as a base material for printed circuit boards.

Electrical characteristics do not change due to humidity.

Excellent high frequency characteristics.

Excellent heat resistance and good solder resistance.

Excellent solvent resistance.

Excellent flame retardancy.

High hardness.

The raw material resin is used in powder form, preferably having a particle size of 60 mesh under.

The purpose of the process of preforming the board is to improve handling in the subsequent integration process with copper foil when starting from powder raw materials, increase productivity, and ensure flatness of the finished product. The powder may be formed into a self-supporting thin plate. Therefore, the molding may be carried out at a temperature below the glass transition point of the resin (270°C in the case of polymetaphenylene isophthalamide), and the powder may be compacted so that it is compacted and has self-supporting properties.
Furthermore, it may be molded into a resin melt molded product at a high temperature.

In the case of compacted powder, specifically, it is carried out at a temperature of 150 to 270°C, and when polymetaphenylene isophthalamide is preformed at 200°C, a molding pressure of 500 Kg/cm ² and a molding time of 5 minutes are sufficient.

If the preformed substrate is not only compacted but also melt-molded, only the resin on the bonding surface with the copper foil needs to be melted during subsequent integration with the copper foil, which can shorten the molding time.

The printed circuit board obtained by the manufacturing method of the present invention is of a rigid type, and is preformed so that the resin molded portion has a thickness of 0.5 to 2 mm.

The integral molding with the copper foil is performed at a temperature below the decomposition point of the resin, and in the case of polymetaphenylene isophthalamide whose decomposition point is 365°C, it can be performed at a temperature of 270 to 360°C, but preferably 300 to 330°C. In integration, the higher the molding temperature, the shorter the molding time.
Time: 10 minutes at 360℃ is enough. 10~30 when molded at 320℃ molding temperature and 500Kg/ ^cm2 molding pressure
Molding is completed in minutes. 320 for polyimide 2080
It takes about 20 minutes at ℃.

Polytetrafluoroethylene (PTFE) is used as the resin to cover the copper foil, but the resin has low-temperature flowability and
This is the most preferred because of its mold shrinkage, good peelability, and high decomposition temperature.

The PTFE sheet can be melt-cast during integral molding and placed on the copper foil to cover the surface of the copper foil.
In order to ensure the smoothness of the copper foil surface of the product, it is preferable to use a commercially available PTFE skiving sheet with a smooth surface and place it in a thickness range of 0.1 to 4 mm.

If the thickness of the sheet is 0.1 mm or less, even if the PTFE melts, it will not flow into the gap between the mold and the side edge of the base material, and there is a risk that the side edge of the copper foil will oxidize. Further, if the thickness is 4 mm or more, a considerable amount of heat is required to melt the PTFE sheet, which increases the time required for integral molding, which is uneconomical.

The copper foil used may be that normally used for printed circuit boards, and has a thickness of 18 to 50 microns, most commonly around 35 microns.

The above-mentioned substrate preformed by heating and pressing the aromatic polyamide resin powder or aromatic polyimide resin powder, the copper foil, and the PTFE sheet are stacked in this order, and the space between the inner wall of the mold and the outer peripheral surface of the substrate is stacked on top of each other in this order. The copper foil is inserted into a mold with a small gap left between the substrate and the copper foil, and heated and pressed to integrally mold the substrate and the copper foil.

At this time, the gap formed between the inner wall of the mold and the outer peripheral surface of the substrate may be about the clearance required for inserting the substrate into the mold, and is actually about 0.06 mm.

〔Effect of the invention〕

The features of the present invention are obtained through the following mechanism.

Preformed substrate, copper foil integrated on it,
PTFE sheets, which have a high decomposition start temperature and are easily softened by heat, are stacked on top of the copper foil in this order, and these sheets are inserted into the mold with a slight gap formed between the inner wall of the mold and the outer peripheral surface of the substrate. When this is heated and pressurized in the atmosphere, the preformed insulating material melts.
The PTFE sheet is melt-cast and adheres to the copper foil surface,
Further, the PTFE sheet enters the gap between the inner wall of the mold and the outer peripheral surface of the substrate and covers the outer peripheral surface of the copper foil, so that the copper foil is completely sealed from the atmosphere.

Melting of the insulating material then occurs and the molding is complete. Even during the cooling process, the shrinkage rate of PTFE is large, and the molding of the copper foil is completed in a sealed state.

Therefore, after the PTFE melts and flows and the seal is completed, the copper foil is completely sealed from the atmosphere until the molding is completed (sealing effect), and the molding is completed without being oxidized.

PTFE has good mold releasability (non-stick) and can be easily removed after molding, and since the molding temperature for integration is below the decomposition temperature of PTFE, it can be used repeatedly and is economical with almost no loss.

As described above, according to the manufacturing method of the present invention, a printed circuit board having excellent heat resistance and mechanical properties can be manufactured at low cost in the atmosphere.

Hereinafter, the configuration and effects of the present invention will be further explained with reference to Examples.

Example 1 Aromatic polyamide resin (Teijin Co., Ltd.'s Cornex resin powder) with a density of 0.30 g/cm ³ was dried at 140°C for 15 minutes, filled into a mold heated to 150°C, and 150 kg/cm 3 was obtained.
The powder was compacted for 5 minutes at a pressure of cm ² . While pressurizing, the mold temperature was raised to 310° C., molding pressure was maintained at 150 Kg/cm ² and molding was performed for 15 minutes. Then the mold temperature was increased to 150℃
After cooling, the mold was opened to obtain a molded product measuring 50 mm in length, 100 mm in width, and 2 mm in thickness.

The aromatic polyamide resin molded plate thus obtained, a copper foil with a thickness of 25μ (Furukawa Circuit Oil Co., Ltd.)
(commercially available product) and 1.4 mm thick PTFE skiving sheets were stacked in this order and inserted into the mold with a slight gap formed between the inner wall of the mold and the outer peripheral surface of the molded plate. This was molded in the air at a molding temperature of 320° C., a pressure of 400 Kg/cm ² , and a molding temperature holding time of 20 minutes.

After cooling, the product was taken out to obtain a substrate-copper-foil integrated molded product consisting of an aromatic polyamide resin substrate, a copper foil integrally molded on the surface of the substrate, and PTFE that covered and sealed the surface of the copper foil and its outer peripheral surface.

Next, PTFE was removed from the substrate copper foil integral molding to obtain a heat-resistant printed circuit board in which the copper foil was integrally molded on the surface of the aromatic polyamide resin substrate.

The obtained molded plate had no change in color tone, no oxidation of the copper foil was observed, and the solder heat resistance was good with no change in appearance even after contact at a temperature of 300°C for 10 seconds.

The peeling force was measured using an Instron according to JISC6481 and was found to be 1.0 Kg/cm. Also,
The bending strength according to ASTMD790 was 1500 Kg/cm ² .

Example 2 Aromatic polyamide resin having a density of 0.30 g/cm ³ (Teijin Co., Ltd. Cornex resin powder) was filled into a mold heated to 200° C., and compacted for 5 minutes at a pressure of 500 Kg/cm ² .

The aromatic polyamide resin molded plate obtained in this way, a copper foil with a thickness of 25μ (Furukawa Circuit Oil Co., Ltd.)
1.4 mm thick PTFE skiving sheets were stacked in this order and inserted into the mold with a slight gap formed between the inner wall of the mold and the outer peripheral surface of the molded plate. This was molded in the air at a molding temperature of 320° C., a pressure of 500 Kg/cm ² , and a molding temperature holding time of 20 minutes.

After cooling, the product was taken out to obtain a substrate-copper-foil integrated molded product consisting of an aromatic polyamide resin substrate, a copper foil integrally molded on the surface of the substrate, and PTFE that covered and sealed the surface of the copper foil and its outer peripheral surface.

Next, PTFE was removed from the substrate copper foil integral molding to obtain a heat-resistant printed circuit board in which the copper foil was integrally molded on the surface of the aromatic polyamide resin substrate.

The resulting molded plate had no change in color tone, no oxidation of the copper foil was observed, and the solder heat resistance was good with no change in appearance even after contact at a temperature of 300°C for 10 seconds.

The peeling force was measured using an Instron according to JISC6481 and was found to be 1.1 Kg/cm.

Example 3 Under the same conditions as in Example 1, a printed circuit board having an aromatic polyamide resin molded plate as the center layer and integrated copper foil on both sides was manufactured by heating and pressing once.

That is, the PTFE sheet, copper foil, aromatic polyamide resin molded plate, copper foil, and PTFE sheet are stacked in this order, and a small gap is formed between the inner wall of the mold and the outer peripheral surface of the molded plate. It was inserted into the inside and molded under heat and pressure.

A printed circuit board having the same physical properties as the printed circuit board obtained in Example 1 was obtained regarding the copper foil on both sides and the substrate.

Example 4 "Polyimide 2080" resin powder was dried at 140℃ for 15 minutes, filled into a mold heated to 150℃, and 150Kg/
The powder was compacted at a pressure of ^cm2 . While pressurizing, adjust the mold temperature.
Raise the temperature to 350℃ and keep the molding pressure at 500Kg/ ^cm2 .
Mold for 20 minutes. Next, after cooling the mold temperature to 150°C, the mold was opened to obtain a molded product measuring 50 mm in length and 100 mm in width.

A printed circuit board was manufactured under the same conditions and method as in Example 1 using the thus obtained thermoplastic polyimide resin molded product.

The obtained molded plate had no change in color tone, no oxidation of the copper foil was observed, and the soldering heat resistance was good with no abnormality at a temperature of 300° C. for 15 seconds.

The peeling force was measured using an Instron according to JISC6481 and was found to be 0.8 Kg/cm. Also,
The bending strength according to ASTMD790 was 1400 Kg/cm ² .

From the above examples, it can be seen that according to the manufacturing method of the present invention, the copper foil does not oxidize and has excellent heat resistance in the atmosphere.
It has been found that it is possible to produce printed circuit boards with mechanical properties.

Claims (1)

[Claims] 1. A substrate preformed by heating and pressing aromatic polyamide resin powder or aromatic polyimide resin powder, copper foil, and a polytetrafluoroethylene resin sheet with a thickness of 0.1 to 4 mm in this order. While stacking the substrates, a small gap is formed between the outer circumferential surface of the substrate and the inner wall of the mold, and the substrate is inserted into the mold, heated and pressurized in the atmosphere at a temperature of 270℃ or higher to form polytetrafluorocarbon. An ethylene resin sheet is melt-cast to cover the copper foil surface and its outer circumferential surface to form a substrate copper foil integral molding that seals the copper foil from the atmosphere, and then a polyethylene resin sheet is formed from the substrate copper foil integral molding. A method of manufacturing a heat-resistant printed circuit board comprising removing tetrafluoroethylene resin. 2. The method according to claim 1, wherein the aromatic polyamide resin is polymetaphenylene isophthalamide. 3. The method according to claim 1 or 2, wherein the copper foil has a thickness of 18 to 50 μm. 4. Claims 1 to 3, characterized in that the preforming is performed at a temperature below the glass transition point of the resin, and the resin compact is used for subsequent integral molding.
The method described in section. 5. The method according to claims 1 to 3, wherein the preforming is performed at a temperature higher than the glass transition point of the resin, and the resin melt-molded product is used for later integral molding.