JPH03142994A - Manufacture of transfer sheet for injection molded printed wiring board - Google Patents

Abstract

PURPOSE:To efficiently manufacture a transfer sheet by thermally press-adhering a copper foil on a mold release layer on a carrier film, pattern-printing etching resist on the obtained laminated film, and etching it. CONSTITUTION:A carrier film 1 made of suitable resin such as PET, P1 film, etc., is coated with mold release agent having suitable adhesive strength to a copper foil to form a mold release layer 3. Then, a laminated film in which the copper foil 3 is thermally press-adhered by using a heat press-adhering roller, etc., is obtained, and adhesive 4 is pattern-printed on the surface of the foil 3 of the obtained film by screen printing, etc. The adhesive to be used which has chemical resistance at etchant and sufficient adhesive strength is selected. It is dipped in etchant such as ferric chloride solution, etc., to remove the unnecessary part of the foil. Thus, a transfer sheet is efficiently obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for efficiently manufacturing a transfer sheet for obtaining an injection molded printed wiring board by transfer.

(Prior art) As a method for obtaining an injection molded printed wiring board by a transfer method, there is a method using a transfer sheet in which a laminated circuit unit is formed by laminated printing using conductive and insulating paste (Japanese Patent Application Laid-Open No. 1983-1983-1). 219189) or a method using a transfer sheet provided with a release layer made of a material that is eroded by the solvent of the conductive ink, a protective layer, and a printed circuit made of the conductive ink (
JP-A No. 63-257293), but also uses the vapor deposition method, in which a metal film is placed on a conductive base film by plating, a pattern is formed with a masking material, and then a metal film is further attached to obtain a metal pattern. , a method for obtaining a metal pattern printed board by etching this (Japanese Patent Application Laid-Open No. 63-274194) has been disclosed.

However, these transfer sheets can be used as circuit conductors.
There are various problems due to the use of conductive paste and metal conductors obtained by vapor deposition.

When using a conductive paste, it is possible to easily create a circuit by printing and drying it, but the conductor resistance is higher than that of metallic copper, and the reliability as a circuit is lacking.

Further, methods for obtaining copper circuits by vapor deposition or the like have no problem with conductor resistance, but it is difficult to obtain a conductor thickness necessary for a printed wiring board.

Another disadvantage is that the obtained metal surface is flat and does not provide an anchor effect in adhesion, resulting in a lack of adhesion to the base material. Economically, there is a problem in that the cost is extremely high.

As a method to solve these circuit conductor problems, a patent application
1-161383, etc., a method of forming a circuit by etching copper foil has been proposed.

(Problems to be Solved by the Invention) In order to obtain a transfer sheet using a copper foil having a cross-sectional structure as shown in FIG. 1 by the conventional subtractive method, the following steps are required.

l) A process of bonding copper foil and a carrier film to make a laminated film, 2) A process of attaching a resist such as PVC resin to the surface of the copper foil, 3) An etching process, 4) A resist peeling process, and 5) An adhesive application process , is.

However, in such a manufacturing method, there is a waste in that it is necessary to go through the steps of attaching a resist agent that is not needed for the final product and peeling off the resist agent. In addition, during the peeling process, the adhesion between the release layer and the copper foil may be broken due to mechanical impact from puffs, etc., causing damage to the circuit.
In the adhesive application process, it is necessary to selectively and accurately overprint on the copper foil circuit, and there is a risk that the adhesive will adhere to the release layer due to printing misalignment, causing failure in peeling of the carrier film after transfer molding. There is.

(Means for Solving the Problems) The present invention was completed as a result of studies to improve these problems and efficiently obtain a transfer sheet.

Next, the technical means of the present invention will be explained. As a means to improve these problems, the present inventors have directly pattern printed adhesive for copper foil without using conventionally used metal resists such as plating with gold or tin, or organic resists such as dry films. By using the adhesive as an etching resist, the process can be greatly simplified.
The inventors discovered that problems such as damage to copper foil circuits and overlapping printing accuracy can be solved, leading to the completion of the present invention.

That is, a suitable resin carrier film such as PET,
A release layer is formed by applying a release agent having appropriate adhesion to copper foil onto a PI film or the like. Such mold release agents include materials having properties such as thermocompression bondability and removability;
For example, a mixture of polyvinyl formal and silicone (a mixture of epoxy resin and polyvinyl formal) may be used.

Next, a laminated film is obtained by heat-pressing with a copper foil using a heat-pressing roller or the like.

A pattern of adhesive is printed on the copper foil surface of the obtained laminated film by screen printing or the like. The adhesive used is
A material is selected that has chemical resistance to etching liquids and sufficient adhesion to the base resin of the intended injection molded article.

The conditions required for such an adhesive are as follows: First, it must be of lot melt type.

Second, it has chemical resistance.

Thirdly, it must be suitable for printing.

Regarding printability, some additives may be added to improve printability. Examples of such adhesives include the following commercially available products. Namely, polyester-based products include Toyobo's Vylon, Toagosei's Aronmelt, and Toshi-based Kemit; polyvinyl formal products include Denka Formal, made by Denki Kagaku; polyvinyl butyral products include Denka Butyral, also made by Denki Kagaku; and polyamide-based products include Fuji Kasei's Tomide and Ethylene. - Examples of vinyl acetate copolymer systems include Sumitate manufactured by Sumitomo Chemical, and examples of polyacrylic acid ester systems include ThreeBond manufactured by ThreeBond. Thermoplastic polyester resin adhesives, polyvinyl formal resin adhesives, and the like are preferably used. In order to obtain good chemical resistance to etching solutions and adhesion to the base resin, the printing film thickness should be 5 to 1.
00 μm, preferably 20 to 50 μm.

If the film thickness is too thin, sufficient chemical resistance will not be ensured, resulting in poor etching. Moreover, if it is too thick, there is a risk that the circuit accuracy will decrease due to liquid dripping during printing, etc. Next, chloride chloride
Immerse it in an etching solution such as iron solution to remove unnecessary parts of the copper foil. Further, the desired transfer sheet is obtained by sufficiently carrying out acid washing with a diluted hydrochloric acid solution, washing with water, etc., and drying.

By the manufacturing method described above, it is possible to efficiently obtain a transfer sheet in which the copper foil circuit is not damaged and the adhesive is selectively adhered to the circuit copper foil with high precision.

Next, a method for obtaining a molded body using the obtained transfer sheet will be explained.

The transfer sheet is supplied into the cavity of an injection mold consisting of a fixed side and a movable side so that the carrier film is on the surface side of the molded body, and the mold is clamped.

Next, the base resin is injected to form a molded body, and at the same time, the circuit on the transfer sheet is transferred to the surface of the molded body. When the molded product is taken out from the mold after cooling, the carrier film and release layer of the transfer sheet are peeled off from the molded product, and an injection molded product with a circuit conductor is obtained.

Base resins include general-purpose plastics such as ABS resin, polycarbonate (PC), and polybutyl terephthalate (PBT), which are generally used for electrical insulation purposes, and polyether sulfone for applications that require particularly heat resistance. Super engineered plastics such as (PES) and polyetherimide (PEI) are used.

Depending on the application, a filler such as glass fiber may be mixed into the base resin.

(Example) 1) A release agent containing an epoxy resin, polyvinyl formal, and an amine curing agent was applied onto a PET film (50 μm) at 20 g/m2 using a roller coater.
Dry. Furthermore, this film and electrolytic copper foil (35 μm)
were pressed together with a hot pressing roller (roller temperature: 200° C.) with the roughened surface of the copper foil facing the front side to obtain a laminated film. After degreasing the copper foil surface of the laminated film with isopropyl alcohol, a pattern is printed using screen printing with a chloroform/toluene solution of thermoplastic polyester resin (Vylon 300, manufactured by Toyobo Co., Ltd.) whose viscosity has been adjusted to an appropriate level. did. The printed film thickness was 35 μm. It was etched by immersing it in a ferric chloride solution. After completion of etching, washing with water, acid washing, washing with water and finally drying with hot air at 110°C gave a transfer sheet having a copper foil circuit.

The obtained transfer sheet was in good condition, with no defects in the circuit due to etching or corrosion of the circuit due to penetration of the etching solution.

In addition, the obtained transfer sheet was placed in the cavity of an injection mold, and injection molding was performed using ABS resin, and the peel strength of the circuit of the obtained molded product was measured.
It showed a good value of 1.68 kg/an.

(Effects of the Invention) According to the present invention, it is possible to omit the steps of resist agent application, etching, resist agent peeling, and adhesive printing, which are employed in conventional etching methods. Moreover, the problems of 4° in accuracy and reliability in processes such as carrier film peeling and printing can be solved all at once.

[Brief explanation of the drawing]

FIG. 1 shows a cross section of a transfer sheet with a copper foil circuit. 1 is a carrier film, 2 is a release layer, 3 is a circuit copper foil, 4
indicates adhesive.

Claims (2)

[Claims] (1) A transfer for injection molded printed wiring boards characterized by forming a release layer on a carrier film, then heat-pressing it with copper foil, printing an etching resist pattern on the obtained laminated film, and further etching it. Method of manufacturing sheets. (2) The method for producing a transfer sheet for an injection molded printed wiring board according to claim 1, wherein the etching resist is a thermoplastic resin adhesive.