JPS6213336A - Manufacture of heat-resistant printed substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 that can manufacture a printed circuit board that integrates a thermoplastic resin insulating material substrate and copper foil with a molding temperature of 270° C. or higher in the atmosphere.

[Prior art] Conventionally, thermosetting resins such as glass epoxy resins and epoxy modified addition polyimide resins have been used as base materials for rigid printed circuit boards, and the molding temperature with metal foils such as copper foils is low. It is carried out at a low temperature of about 150 to 220°C. Therefore, problems such as copper oxidation were not so significant.

However, the above-mentioned glass epoxy resin has poor heat resistance and flame retardancy, and addition type polyimide resin has drawbacks such as gas generation during chemical reactions and crosslinking, making it unreliable as a base material for printed circuit boards for electrical materials. Met.

Therefore, it is desirable to use a material that has excellent heat resistance, mechanical properties, etc. and is suitable as a base material for a printed circuit board, but it is expensive to integrally mold such a material with metal foil without using a chemical reaction. A high molding temperature is required, and therefore, molding in the atmosphere cannot produce the desired product due to problems such as oxidation of the copper foil.

Therefore, in order to eliminate such problems, the above-mentioned molding must be performed in an oxygen-free atmosphere such as a nitrogen atmosphere, and molding methods such as so-called vacuum molding and hot press molding should not be adopted. However, these are expensive molding methods and are not suitable for industrial use.

[Object of the Invention] In view of the above circumstances, 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 provide a heat-resistant printed circuit board that is made of a heat-resistant thermoplastic resin having a molding temperature of 270° C. or higher and that has excellent heat resistance and mechanical properties and can be manufactured at low cost in the atmosphere. An object of the present invention is to provide a method for manufacturing a substrate.

[Structure of the Invention] The manufacturing method of the present invention comprises a substrate preformed by heating and pressing heat-resistant thermoplastic resin powder having a molding temperature of 270° C. or higher, a copper foil, and a polytetrafluoroethylene resin (hereinafter referred to as PTF).
It's called E. ) in this order in a mold, and heat and pressurize the copper foil and the board so that the PTFE melts and spreads to cover the surface of the copper foil and seal the copper foil from the atmosphere. PTFE from the substrate copper foil integrated molded product.
consists of removing.

The thermoplastic resin having a molding temperature of 270°C or higher used in the present invention includes an aromatic polyamide resin such as polymetaphenylene isophthalamide, and an aromatic resin commercially available from Upjohn Co. under the trade name "Polyimide 2080". Among them, polymetaphenylene isophthalamide is particularly preferred.

Polymetaphenylene isophthalamide has the following characteristics and is optimal as a substrate 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.

Here, the resin having a molding temperature of 270° C. or higher means a polymer resin that has a softening point of 270° C. or higher and does not undergo any special chemical reaction or crosslinking during molding.

The raw material resin is used in the form of powder, 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 can 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 can be simply compacted so that it has self-supporting properties, and the resin can be melt-molded at a higher temperature. It may also be molded into objects.

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, the molding pressure is 500 K9 / cm,
A molding time of 5 minutes is sufficient.

If the preformed substrate is not only pressed into powder but also melt-molded, it is only necessary to melt the resin on the bonding surface with the copper foil when integrating the bond 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 the thickness of the resin molded part is 0.5 to 2.
Preform to a size of 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 at a temperature of 300 to 360°C.
The temperature is 330°C. The higher the molding temperature in the integration process, the shorter the molding time, which may be 1 hour at 270°C or 10 minutes at 360°C.

When molding is performed at a molding temperature of 320° C. and a molding pressure of 50 (ly/cII), molding is completed in 10 to 30 minutes.

In the case of polyimide 2080, it takes about 20 minutes at 320°C.

PTFE is used as the resin covering the copper foil, and this resin is most preferred because it has low-temperature flowability, mold shrinkage or good peelability, and high decomposition temperature.

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

The copper foil used may be that normally used for printed circuit boards, and has a thickness of 18-50μ, most commonly 35μ.
That's about it.

[Effects of the Invention] The features of the present invention are obtained through the following mechanism.

A preformed substrate, a copper foil integrated thereon, and a PTFE sheet that has a high decomposition onset temperature and is easily softened by heat are placed on top of the copper foil in this order in a mold, and when heated and pressed, the preformed insulating material is created. Before the PTFE sheet melts, the PTFE sheet is melt-cast and tightly adheres to the surface of the copper foil, and further penetrates into the gap between the mold and the base material, completely sealing the copper foil from the atmosphere.

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

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

The gap between the mold and the base material is necessary for inserting the base material into the mold, and may be about a clearance, and is actually about 0.06 m.

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

As described above, according to the manufacturing method of the present invention, excellent heat resistance,
, it is possible to manufacture printed circuit boards having mechanical properties at low cost in the atmosphere.

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

Example 1 Aromatic polyamide resin with a density of 0.30'J/7 (Teijin Co., Ltd.'s Cornex resin powder) was dried at 140°C for 15 minutes, filled into a mold heated to 150°C, and 150Kg/C
! The powder was compacted for 5 minutes at a pressure of i. While pressurizing, the mold temperature was raised to 310° C., and molding was carried out for 15 minutes while maintaining the molding pressure at 150 kg/d.

Next, after cooling the mold temperature to 150℃, the mold was opened and
A molded product with a width of 0 m+, a width of '100#I, and a thickness of 2i* was obtained.

The aromatic polyamide resin molded plate thus obtained, a copper foil with a thickness of 35 μm (commercially available from Furukawa Circuit Foil 4), and a P-'r FE skiving sheet with a thickness of 1.4 ln were placed in a mold in this order. superimposed on the molding temperature 32
Molding was carried out at 0°C, at a pressure of 400 kg/aA, and at a molding temperature holding time of 20 minutes.

After cooling, it was taken out and the PTFE sheet was removed to obtain an integrally molded copper foil resin molded board.

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/cs.

In addition, the bending strength according to ASTM D790 is 1500K.
g/d.

Round 11 Z Aromatic polyamide resin (Teijin Co., Ltd.'s Cornex resin powder) having a density of 0.30 g/cIj was filled into a mold heated to 200° C., and compacted for 5 minutes at a pressure of 500 Kg/ci.

The aromatic polyamide resin compact obtained in this way, a copper foil with a thickness of 35 μm (commercially available from Furukawa Circuit Foil Kan), and a PTFE skiving sheet with a thickness of 1.41 μm were filled in a mold in this order. Molding temperature 320℃, pressure 500/
(Molded at y/ri, molding temperature held for 20 minutes.

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.

When the peeling force was measured using an Instron according to J15C6481, it was 1.1 to 9/as.

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, a PTFE sheet, copper foil, aromatic polyamide resin molded plate, copper foil, and PTFE sheet were filled in this order into a mold, 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 2080J resin powder was dried at 140°C for 15 minutes, filled into a mold heated to 150°C, and
The powder was compacted at a pressure of m. While pressurizing, set the mold temperature to 350℃.
The temperature was raised to .degree. C., and the molding pressure was maintained at 500 kg/C1i for 20 minutes. Next is money! lf! After cooling the temperature to 150℃, open the mold and make it 50# in length, 100# in width, and 2m thick.
A molded product with a rating of + was obtained.

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 solder 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 KU/as.

In addition, the bending strength according to ASTM D790 is 1400.
It was Kg/ci.

From the above examples, it was found that according to the manufacturing method of the present invention, a printed circuit board having excellent heat resistance and mechanical properties in the atmosphere can be manufactured without oxidizing the copper foil.

Claims (7)

[Claims] (1) A substrate preformed by heating and pressing heat-resistant thermoplastic resin powder having a molding temperature of 270°C or higher, and a copper foil;
The polytetrafluoroethylene resin and polytetrafluoroethylene resin are layered in this order in a mold, and the polytetrafluoroethylene resin is melted and cast during heating and pressure, covering the surface of the copper foil and sealing the copper foil from the atmosphere. A method for manufacturing a heat-resistant printed circuit board, which comprises pressing to integrate the copper foil and the board, and then removing polytetrafluoroethylene resin from the integrated molded product of the board and copper foil. (2) The method according to claim 1, wherein the heat-resistant thermoplastic resin is an aromatic polyamide resin. (3) Claim 1, characterized in that the heat-resistant thermoplastic resin is polymetaphenylene isophthalamide.
or the method described in Section 2. (4) The method according to claim 1, wherein the heat-resistant thermoplastic resin is an aromatic polyimide resin. (5) The method according to any one of claims 1 to 4, wherein the copper foil has a thickness of 18 to 50 μm. (6) The method according to any one of claims 1 to 5, 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. (7) The method according to any one of claims 1 to 6, wherein the preforming is carried out at a temperature higher than the glass transition point of the resin, and the resin melt-molded product is used for subsequent integral molding.