JPH0156665B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a metal flexible printed circuit board, and particularly to a method for producing a metal flexible printed circuit board with excellent withstand voltage characteristics and adhesive properties. [Conventional technology] Recently, metal flexible printed circuit boards (hereinafter referred to as
It is abbreviated as MFPC. ) are emerging. this
MFPC is a product in which metal foil for the base material and metal foil for circuit formation are integrated via an adhesive insulating layer.
For this reason, the adhesive insulating layer of MFPC has flexibility,
It is required to have excellent heat resistance, adhesion, insulation resistance, chemical resistance, voltage resistance, etc. [Problems to be solved by the invention] However, the adhesive insulating layer of conventional MFPC does not satisfy all of these properties at a high level.For example, if the withstand voltage property is high, the adhesion is low. There were advantages and disadvantages to its characteristics. [Object of the invention] This invention was made in view of the above circumstances,
In particular, the object of the present invention is to provide a method for producing an MFPC having an adhesive insulating layer that has good adhesion to metal foil and excellent voltage resistance characteristics. [Structure] The MFPC manufacturing method of the present invention involves applying an adhesive containing thermosetting resin and rubber as main components to each of two metal foils, and applying an adhesive to each of the two metal foils to attach them. The curing reaction progress state of the adhesive layers of the metal foils is made different so that at least one of them is in a gelled state, and then both are bonded together and cured by heating. One of the two metal foils used in the manufacturing method of this invention is the base material of the MFPC, and is generally made of copper, aluminum, iron, silicon steel, iron-aluminum clad, or nickel with a thickness of 7 to 70 μm. Foils such as aluminum clad and amorphous metal are used. Depending on the selection of the metal foil used as the base material, the resulting MFPC can have certain functions. For example, copper and aluminum foil provide good heat dissipation shielding, iron and nickel provide electromagnetic shielding, and silicon steel and amorphous metal provide magnetic permeability, making it possible to manufacture distinctive MFPCs. Further, as the other of the two metal foils for forming a circuit, a foil made of copper, aluminum, nickel, silicon, etc. with a thickness of 7 to 70 μm is used. Then, these two metal foils are pasted and integrated via an adhesive insulating layer made of adhesive to achieve the desired purpose.
Becomes MFPC. As the adhesive forming the adhesive insulating layer, a thermosetting adhesive whose main components are a thermosetting resin and rubber is used, and the thermosetting resin is an epoxy resin,
Phenol resins are used, and rubbers such as nitrile rubber and urethane elastomers are used.
Curing agents such as diaminodiphenyl sulfone (DDS), diaminodiphenylmethane (DDM) and imidazoles can be added to increase heat resistance. Using this adhesive, the two metal foils are bonded together to form an MFPC, and the key point of this invention is to control the progress of the curing reaction of the adhesive at this time. That is, the above adhesive is applied to each adhesive surface of two metal foils, and when it is dried, the heating conditions are adjusted to make the progress of the curing reaction of each adhesive layer different. Both are attached with the agent layer in a gelled state.
Specifically, if you use an adhesive with a gelling time of 10 minutes at 150°C, one adhesive layer
Heat at 150°C for 10 minutes or more, for example 15 minutes, to fully gel. Then, the other adhesive layer is heated at 150° C. for 10 minutes or less, for example, 3 minutes, and is stopped just before gelation. Then, both adhesive layers were combined and heated to 150℃.
A temperature above 170℃ is sufficient, for example 30~
Heat for 60 minutes to fully cure the adhesive. Through such operations, an adhesive insulating layer having high voltage resistance and high adhesiveness can be obtained. In addition, when the adhesive layer is heated and dried, if it is introduced into a vacuum drying oven or the like and dried under reduced pressure, the organic solvent in the adhesive layer is completely removed, leaving voids such as air bubbles in the adhesive insulating layer. Furthermore, the physical properties of the adhesive insulating layer can be improved. The thickness of the adhesive insulating layer is approximately 20 to 100 μm,
If it is less than 20μm, the reliability of the withstand voltage characteristics is low.
If the thickness exceeds 100 μm, the coating process becomes difficult and air bubbles tend to form, which is inconvenient. [Function] In such a manufacturing method, when the metal foils are attached, the reaction progress state of the adhesive of each foil is different, and one of the foils has already completed gelation.
The adhesive layer does not fluidize during heating for final curing, and the thickness of the adhesive insulating layer does not become uneven. Furthermore, since the thickness of each coating is approximately 1/2 of the total thickness, the solvent in the adhesive evaporates well, and voids due to residual solvent are less likely to occur. Furthermore, since the adhesive layer is divided into two layers, the thickness of each layer is reduced, and the internal strain of the adhesive layer that occurs during dry gelation is reduced. Due to these factors, the obtained MFPC has good withstand voltage characteristics and high adhesiveness. Experimental Example 1 An adhesive having the following composition was prepared. Bisphere A type epoxy resin 150 parts by weight Phenol resin (resol) 200 parts by weight Nitrile rubber 150 parts by weight DDS 10 parts by weight Imidazole 0.1 parts by weight Solvent (methyl ethyl ketone) 600 parts by weight This adhesive was applied to a 35 μm thick electrolytic copper foil.
It was heated at 150°C for 15 minutes to form an adhesive layer with a thickness of about 20 μm. On the other hand, this adhesive was applied to a 50 μm thick aluminum foil (99.5% purity) and heated at 150° C. for 3 minutes to form an adhesive layer about 20 μm thick. The gel time of this adhesive was 10 minutes at 150°C. Next, bond the copper foil and aluminum foil together.
Heat and pressure treatment at 170℃ for 60 minutes at a pressure of 70Kg/ ^cm2 ,
Got MFPC. Let this MFPC be Sample 1. For comparison, the above adhesive was applied to a similar copper foil and heated at 150°C for 3 minutes to form an adhesive layer with a thickness of approximately 40 μm. A similar aluminum foil was laminated to this copper foil and heated at 170°C. MFPC was obtained by heat-pressure treatment at a pressure of 70 Kg/cm ² for 60 minutes. This is called sample 2. Experimental Example 2 An adhesive having the following composition was prepared. Bisphenol A type epoxy resin 210 parts by weight Nitrile rubber 250 parts by weight DDS 50 parts by weight Imidazole 5 parts by weight Solvent (methyl ethyl ketone) 350 parts by weight This adhesive was applied to a rolled steel foil with a thickness of 35 μm.
It was heated at 170°C for 15 minutes to form an adhesive layer with a thickness of about 30 μm. In addition, the same adhesive was applied to silicon steel foil with a thickness of about 50 μm, and it was heated at 170°C for 3 minutes to create a thickness of about 20 μm.
An adhesive layer was formed. Paste the two foils together,
MFPC was obtained by heating at 170°C for 60 minutes. This is called sample 3. The gel time of the above adhesive is 170
℃ for 10 minutes. For comparison, the above adhesive was applied to a similar rolled steel foil and heated at 170°C for 3 minutes to form an adhesive layer with a thickness of about 50 μm, and a silicon steel foil was bonded to this.
MFPC was obtained by heating at 170°C for 60 minutes. This is called sample 4. The characteristics shown in Table 1 were measured and evaluated for Samples 1 to 4 obtained as described above.

〔Effect of the invention〕

As explained above, according to the MFPC manufacturing method of the present invention, the thickness of the adhesive insulating layer is uniform, and there are almost no defects such as voids or internal distortion inside the layer, and therefore the obtained MFPC is high. It has voltage resistance characteristics and good adhesiveness.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a metal flexible printed circuit board in which two sheets of metal foil are each coated with an adhesive mainly composed of thermosetting resin and rubber, and both metal foils are bonded together. A method for producing a metal flexible printed circuit board, characterized in that the curing reaction progress state of the adhesive layer of the foil is made different so that at least one of the foils is in a gelled state, and then both are bonded together and cured by heating.