JP2551196B2 - Transfer sheet for injection molded printed circuit boards - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transfer sheet for efficiently obtaining an injection-molded printed circuit board.

2. Description of the Related Art As a method for obtaining an injection-molded printed wiring board by a transfer method, a method using a transfer sheet on which a laminated circuit unit is printed by using conductive and insulating pastes (JP-A-63-219189) And a method of using a transfer sheet provided with a release layer made of a material that is corroded by a solvent of a conductive ink, a protective layer, and a printed circuit made of a conductive ink (Japanese Patent Laid-Open No. Sho 61-206).
63-257293), as a method of solving the problems of the electrical characteristics, heat resistance and the like of the above method, the present inventors have
There is proposed a method (Japanese Patent Application No. 01-161383) in which a copper foil is laminated on a carrier film with a specific release layer (adhesive), and is formed into a circuit by an etching method.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the case of a transfer sheet using a conductive paste, there is a problem that the heat resistance of the paste itself is low and a circuit flows due to the injected resin.
Even when the transfer sheet using the copper foil circuit described above is used, if the resin used for injection molding has a poor fluidity due to glass fiber or the like, or the type of gate, etc. When the value of γ becomes large, there is a risk that the impact at the time of injection causes peeling between the carrier film and the release layer as illustrated in FIG. 2, resulting in circuit damage. This circuit damage is particularly likely to occur in the peripheral area of the gate. An object of the present invention is to improve the adhesion between a carrier film and a release layer and solve the above problems.

Means for Solving the Problem As a means for preventing peeling between the carrier film and the release layer as described above, the adhesive force is improved by treating the surface of the carrier film for improving the adhesive force or improving the composition of the release layer itself. The method of making it possible is considered.

The latter method is not an appropriate method because there is a risk of deterioration of other properties required for the release layer, for example, deterioration of heat resistance and deterioration of releasability from the copper foil circuit.

Since the former method does not change the release layer characteristics, various treatments for improving the surface adhesive strength were investigated. As a result, it has been found that the object is achieved by roughening the surface of the film. In particular, Rmax when measuring the surface roughness with a surface roughness meter is at least 0.5 μm or more, preferably 1.5 μm.
By using a film having a thickness of m to 5.0 μm, an extremely excellent adhesion can be obtained due to the anchor effect and the like, and by using such a surface roughening treatment film as a transfer sheet, the above-mentioned problems can be solved. They have found things and completed the present invention. If it is less than 0.5 μm, a sufficient anchor effect cannot be obtained, and if it exceeds 5.0 μm, the surface of the film becomes too rough, which is not preferable for forming a transfer film.

The transfer sheet may be formed according to a conventional method, and the outline of the method will be described below.

First, as the carrier film, a plastic film whose surface is in contact with the release layer has a roughness of 0.5 μm is used. PET (polyethylene terephthalate resin), PI (polyimide resin), PC (polycarbonate resin), PES (polyether sulfone resin), PEI (polyetherimide resin), etc. are taken into consideration as the material of the film considering the molding temperature of the molded circuit. Can be selected from the above and used. The film thickness is also arbitrarily selected.

Next, a release agent is applied to the roughened surface of this film using a roller coater or the like, and then dried. As the release agent, a mixture of epoxy resin, amine curing agent, polyvinyl formal resin and the like is preferably used. Next, the roughened surface of the copper foil is placed on the front side, and thermocompression bonding is performed with the carrier film to obtain a laminated sheet.

The copper foil surface of this laminated sheet is patterned with an etching resist by screen printing. A photographic method using a dry film may be used. Next, an unnecessary portion of copper is removed by using an etching solution such as cupric chloride to obtain a copper circuit.

Further, an adhesive such as a polyester-based adhesive or a polyvinyl formal-based adhesive may be laminated and printed by screen printing on the copper circuit in order to have sufficient adhesive strength with the molded product resin.

 The desired transfer sheet is obtained by the above method.

Examples Hereinafter, specific examples will be described.

Example 1. As a carrier film, a surface-roughened film having a thickness of 50 μm was used.
A PET film (matte film NS-50 manufactured by Teijin Ltd.) was used. When the surface freshness was measured by a stylus method (using Surftest 201 manufactured by Mitutoyo Corporation), Rmax was 2.8 μm. Using this carrier film, a transfer sheet was prepared by a conventional method. Using this transfer sheet, set it in a mold with a direct gate of 8 mmΦ, and
Transfer molding was carried out under the molding conditions shown in Table 1 using the resin shown in Table 1, and the state of peeling between the carrier film and the release layer around the gate (damage of the circuit), which is particularly likely to cause peeling, was examined.

The evaluation results are shown in Table 2 together with the evaluation results of Comparative Example 1 (described later).

Comparative Example 1 Using a PET film (manufactured by Teijin Ltd.) having a thickness of 50 μm and not subjected to surface roughening as a carrier film, transfer molding was carried out in the same manner as in Example 1, and the carrier film and the release layer around the gate. The state of peeling was investigated. When the surface roughness of the above film was measured, its Rmax was 0.3 μm.
Met.

* 1 Types of base resin and glass fiber (GF) content Base resin GF content PC (polycarbonate resin): Teijin Chemicals Panlite
GN-3130 30% PPS (Polyphenylene sulfide resin): Toray
Lina A-504 40% PES (Polyethersulfone resin): Mitsui Toatsu Victrex
4101G GL-20 20% PEI (Polyetherimide resin): Engineering
Plastic ULTEM # 2200 20% Effect of the invention Adhesion between the carrier film and the release layer interface according to the invention
By making improvements, even in transfer molding under adverse conditions,
It becomes possible to perform stable and favorable molding.

[Brief description of drawings]

Fig. 1 shows the fixed state of the transfer sheet during molding using a mold, and Fig. 2 is an enlarged view near the gate of the same sheet shown in Fig. 1, which shows the gate when a conventional carrier film is used. It is a figure which shows the state which a pattern peels by the resin pressure etc. which flow in from.

Claims (2)

(57) [Claims] 1. A transfer sheet for an injection-molded printed circuit board, which is formed by laminating a carrier film, a release layer, a copper foil circuit and an adhesive layer, and roughens the surface of the carrier film on the side in contact with the release layer. A transfer sheet for an injection-molded printed circuit board, characterized by using the above-mentioned film. 2. The injection-molded printed circuit board according to claim 1, wherein the surface roughness of the carrier film is 0.5 μm or more when measured with a surface roughness meter. Transfer sheet.