JPH0148142B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a copper-clad laminate useful as a highly reliable printed circuit board. So-called copper-clad laminates, in which copper foil is laminated on one or both sides of an insulating substrate via an adhesive layer, are widely used for wiring circuits in electronic devices, but conventional ones have poor electrical properties, adhesive strength, and heat resistance. For these reasons, it has had the disadvantage of not being able to fully meet the recent demands for higher density and higher performance of equipment. In other words, conventional copper-clad laminates generally use electrolytic foil as the copper foil, and after forming an oxide layer on the surface to be laminated by a method such as anodization, a butyral roof enol-based or epoxy-based It was formed by applying and drying an adhesive such as paper, and then stacking it on a prepreg board such as paper-phenol, glass-epoxy, glass-polyester, etc. and heating it under pressure. Tensioned laminates have major drawbacks such as partial delamination of circuits when high-temperature soldering is used and wiring density is limited due to thermal considerations. Due to their presence, when the laminate is used in audio equipment, there have been various problems such as a decrease in response in high frequency bands and an increase in attenuation in the audible frequency range. The inventors of the present invention have conducted intensive research based on the recognition of the above problems, and have found that by using a thermosetting composition mainly composed of a fluorine-containing polymer as an adhesive, the above problems can be solved. We have come to the knowledge that it is possible to manufacture copper-clad laminates in which this problem is eliminated. The present invention has thus been completed based on the above findings, and provides a copper-clad laminate having an adhesive layer between an insulating substrate and a copper foil, in which the adhesive layer contains an addition polymer system having a curing site. The present invention provides a novel copper-clad laminate characterized by being made of a heat-cured product of a composition containing a fluoropolymer as a main component. In the present invention, insulating substrates include not only general substrates such as paper-phenol, glass-epoxy, and glass-polyester, which have been widely used in the past, but also substrates made of various fluorocarbon resins with excellent heat resistance and electrical properties. can also be preferably adopted. Various fluororesins can be used, including polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropene copolymer, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, and tetrafluoroethylene-hexafluoropropene copolymer. ethylene-hexafluoropropene-perfluoro(alkyl vinyl ether) copolymer,
Preferred examples include tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene, and chlorotrifluoroethylene-ethylene copolymer from the viewpoint of dielectric properties. When using an insulating substrate made of fluorine-based resin as described above, its surface may be treated by chemical methods such as defluorination reaction with an alkali metal, oxidation reaction during electrical discharge or flame treatment, sandblasting, or embossing. In a preferred embodiment, the adhesive is treated by a physical method such as direct surface roughening, etc., to improve its affinity with the adhesive before use. In the present invention, the copper foil is not particularly limited, and in addition to electrolytic foil that has been widely used conventionally, rolled foil can also be used. Although ordinary tough pitch copper may be used as the copper material, oxygen-free copper rolled foil is preferably used when applied to audio equipment. In addition, as a means of improving the affinity with the adhesive on the copper foil surface, methods such as ordinary anodic oxidation treatment may be sufficient depending on the application, but if the presence of an oxide layer is disliked, the adhesive A method of high speed brushing of the copper foil in an inert dry gas atmosphere immediately before application is preferred. In the present invention, it is important to use a thermosetting composition mainly consisting of an addition polymer type fluorine-containing polymer having a curing site as an adhesive between the insulating substrate and the copper foil. Even if the composition is a fluorine-containing polymer with excellent heat resistance and electrical properties, if a thermoplastic one is selected with a high melting point to prevent peeling when immersed in a solder bath, it will require high temperatures during the bonding operation. This has disadvantages such as limiting the material of the insulating substrate and increasing undesirable oxidation of the copper foil.Also, room-temperature curable adhesives have problems with the adhesive itself or the adhesive-coated copper foil. There are drawbacks such as shortened usage time and impaired workability, both of which are undesirable. In the present invention, the addition polymer-based fluorine-containing polymer having a curing site is an addition polymer or an addition copolymer of a fluorine-containing unsaturated compound,
Hydroxyl group, epoxy group, carboxyl group,
Examples include those containing hardening sites such as acid amide groups, ester groups, unsaturated bonds, active hydrogen, and halogens. As such a fluorine-containing polymer, a solvent-soluble one can be preferably employed from the viewpoint of ease of operation in the adhesive coating process and ease of controlling the thickness. From the viewpoint of ease of use, addition polymer systems such as copolymers of fluoroolefin and hydrocarbon vinyl ethers can be preferably employed. The fluoroolefin-vinyl ether copolymer that can be suitably used in the present invention contains 30 to 70 mol% and 70 to 30 mol% of units based on fluoroolefin and vinyl ether, respectively, and contains 30 to 30 mol% of units based on fluoroolefin and vinyl ether in tetrahydrofuran in an uncured state. ℃
Preferred fluoroolefin components include tetrafluoroethylene and chlorotrifluoroethylene, and preferred vinyl ether components have a carbon number of about 2 to 8. Examples include alkyl vinyl ethers containing a linear, branched or cyclic alkyl group. In addition, as the comonomer that provides the curing site in such a copolymer, functional group-containing vinyl ethers such as hydroxyalkyl vinyl ether or glycidyl vinyl ether can be preferably employed. The above copolymers are produced by causing a copolymerization reaction by applying a polymerization initiator or a polymerization initiation source such as ionizing radiation to a monomer mixture of a predetermined ratio in the presence or absence of a polymerization medium. Therefore, it can be manufactured. In the present invention, in addition to the fluorine-containing polymer, a curing agent, a curing aid, a curing catalyst, etc. may be appropriately blended into the composition based on the fluorine-containing polymer depending on the form of the cured site. can. For example, for fluorine-containing polymers whose curing sites are hydroxyl groups, curing agents such as melamine curing agents, urea resin curing agents, polybasic acid curing agents, etc. used in ordinary thermosetting acrylic paints are used as curing agents. It is valid as Here, the melamine curing agent is
Examples include butylated melamine, methylated melamine, epoxy-modified melamine, and 0 to 6 depending on the application.
Various degrees of modification can be used, and the degree of self-condensation can also be selected as appropriate. As urea resin,
Examples include methylated urea and butylated urea. Useful polybasic acid curing agents include long-chain aliphatic dicarboxylic acids, aromatic polycarboxylic acids or their anhydrides, and blocked polyvalent isocyanates. When using a melamine or urea curing agent, curing can be accelerated by adding an acidic catalyst. As another example, when the curing site of the fluorine-containing polymer is an epoxy group, amines, carboxylic acids, phenols, alcohols, etc. are effective as curing agents. Aromatic diols are useful as curing aids. The copper-clad laminate of the present invention can be produced by applying a composition mainly composed of a fluorine-containing polymer as described above, preferably in the form of a solution, to the surface to be bonded to at least one of a copper foil and an insulating substrate. In the case of a mold, it can be manufactured by volatilizing the solvent and then bonding the two together under heat. In this case, it is preferable to apply the adhesive to the copper foil from the viewpoint of simplifying the process. In addition to the fluorine-containing polymer, curing agent, etc., the above composition also contains conventional adhesive components such as butyral-phenol or epoxy adhesives, colorants, viscosity modifiers, fillers, stabilizers, or dispersants. It is also possible to appropriately mix agents and the like. The copper-clad laminate thus obtained has excellent heat resistance and is useful as a highly reliable printed circuit board, and has extremely high utility value in the electronics industry. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 and Comparative Example 1 The molar ratio of chlorotrifluoroethylene/ethyl vinyl ether/cyclohexyl vinyl ether/hydroxybutyl vinyl ether was 51/
100 parts by weight of a quaternary copolymer of 23/17/9 was added to a methylated melamine curing agent (Cymel manufactured by Mitsui Toatsu Co., Ltd.).
325) and 0.5 parts by weight of para-toluenesulfonic acid were dissolved in a mixed solvent consisting of 126 parts by weight of xylene and 126 parts by weight of n-butanol to prepare an adhesive solution. The above adhesive is anodized on one side and has a thickness of 35μm.
The solution was applied uniformly to an electrolytic copper foil to a dry thickness of 25 μm, and the solvent was evaporated by heating at 100°C for 10 minutes. Next, the adhesive-coated copper foil was laminated on a paper-based epoxy insulating substrate with a thickness of 1.6 mm, heated and pressed at 170°C for 40 minutes at a pressure of 50 kg/cm ² , and then cooled to obtain a copper-clad laminate. Ta. JISC6481− of the copper-clad laminate thus obtained
Peel strength according to 1976, at 260℃ solder bath surface
The peel strength after floating for 20 seconds and the heat resistance test results were evaluated using a commonly used butyral-phenol adhesive (8 parts by weight of polyvinyl butyral and 1 part by weight of resol, 15 parts by weight of methanol, and 15 parts by weight of acetone). In comparison with those of the copper-clad laminate (Comparative Example 1) prepared using
Shown in the table.

[Table] Example 2 and Comparative Example 2 Rolled oxygen-free copper foil (thickness: 35 μm) subjected to high-speed multi-step brushing in a dry inert gas atmosphere as a copper foil
After brushing the copper foil, apply the adhesive using
A copper-clad laminate was obtained by carrying out the same operation as above except that it was carried out within 25 seconds. The characteristics of the thus obtained copper-clad laminate are shown in Table 2 in comparison with a copper-clad laminate (Comparative Example 2) prepared in the same manner as Comparative Example 1 except that the type of copper foil and the surface treatment method were changed. .

[Table] Examples 3 and 4 Example 1 except for changing the curing agent and curing conditions
A similar adhesive was prepared and various copper-clad laminates were created. The peel strength (JISC6481) of the obtained laminate is shown in Table 3 together with the curing conditions.
In the heat resistance test, there were no abnormalities at 180°C for 60 minutes.

【table】

[Table] Example 5 Two sheets of rolled oxygen-free copper foil on which an uncured adhesive layer was formed in the same manner as in Example 2 were placed on a polytetra foil treated with sodium on both sides, with the adhesive layer facing inside. Layered with fluoroethylene sheets (1mm thick) in between and heated at 180℃ under a pressure of 20Kg/ ^cm2 .
After heating and pressurizing for 20 minutes, the product was cooled to obtain a double-sided copper foil laminate. The peel strength of the thus obtained laminate according to JISC6481-1976 was 1.5 kg, and the frequency was 100 MHz.
The dielectric constant was 2.18. Example 6 100 parts by weight of a terpolymer containing chlorotrifluoroethylene/cyclohexyl vinyl ether/glycidyl vinyl ether in a molar ratio of 52/10/38 was dissolved in 250 parts by weight of xylene along with 1 part by weight of dimethylcyclohexylamine hydrochloride. Using an adhesive solution prepared by
A copper-clad laminate having a peel strength of 2.8 kg was obtained in the same manner as in Example 1 except that the peeling time was 20 minutes.

Claims (1)

[Scope of Claims] 1. A copper-clad laminate having an adhesive layer between an insulating substrate and a copper foil, wherein the adhesive layer has a composition mainly composed of an addition polymer-based fluorine-containing polymer having a curing site. 1. A copper-clad laminate for printed circuit boards, characterized by being made of a heat-cured material. 2. The copper-clad laminate for a printed circuit board according to claim 1, wherein the copper foil is an oxygen-free rolled copper foil. 3. The copper-clad laminate for a printed circuit board according to claim 1, wherein the addition polymer-based fluorine-containing polymer having a curing site is solvent-soluble. 4. Copper for printed circuit boards according to claim 1, wherein the curing site is at least one selected from hydroxyl groups, epoxy groups, carbonyl groups, acid amide groups, ester groups, unsaturated bonds, active hydrogen, and halogens. Tension laminate.