JPS643080B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a hard board for printed wiring that has excellent solder resistance and a low dielectric constant. In recent years, printed wiring boards have been increasingly used for internal wiring in various audio equipment, industrial equipment, telephone exchanges, etc. for the purpose of reducing size and weight, simplifying wiring layouts, simplifying wiring work, and improving reliability. I'm getting used to it. A printed wiring board uses a hard board for printed wiring, which is made by pasting metal foil such as copper on one or both sides of an insulating board, and according to the wiring diagram based on the circuit design,
It is manufactured by partially removing the metal foil using a method such as etching to form a predetermined electric circuit. Printed wiring boards are soldered during the wiring process, so they have a high degree of durability, meaning they will not suffer damage such as deformation, peeling of constituent materials, or cracking even when immersed in a solder bath at 250 to 300°C for about 10 to 20 seconds. Solderability is required. Conventionally, as an insulating substrate, a method for manufacturing a hard substrate for printed wiring uses a composite material made by impregnating a nonwoven or woven fabric with a thermosetting resin liquid such as epoxy resin, phenolic resin, or triazine resin. Methods have been adopted, such as pasting the composite with metal foil via an adhesive, or bringing the composite and metal foil into close contact with each other before curing the thermosetting resin liquid, and then curing them together. However, the hard substrate for printed wiring manufactured based on the conventional manufacturing method as described above has poor electrical characteristics,
It is difficult to say that all necessary conditions such as price are satisfied. For example, electrical properties, especially dielectric constant, are important properties that determine the performance of a wiring board, and the smaller the value, the higher the wiring density of the wiring board and the better the crosstalk, but epoxy resin 4.6
-4.8, phenolic resin 4.8-5.0, and triazine resin 4.1-4.2, all of which have dielectric constants exceeding 4. By using a polyolefin resin as the insulating substrate, the dielectric constant can be significantly improved to 2.2 to 3.0, compared to printed wiring boards using conventional resins. However, when a polyolefin resin and a metal foil are brought into close contact with each other by direct heat and pressure, the resulting bonded substrate becomes curved and cannot be put to practical use. The present invention has been made to solve the above-mentioned problems, and its purpose is to prevent the insulating substrate and the metal foil from being bent even when they are heated and pressed into close contact with each other, and to avoid deformation even when immersed in solder. The present invention provides a method for manufacturing a hard substrate for printed wiring with a low dielectric constant that is completely free from damage such as peeling and cracking. The gist of the present invention is to impregnate a nonwoven fabric or a woven fabric with a liquid polybutadiene resin, and then apply a semi-cured composite between two polyolefin resin plates and between at least one of the resin plates and a metal foil. The method of manufacturing a hard substrate for printed wiring is characterized in that the resin plate is sandwiched between the resin plates, heated and pressurized, and then irradiated with an electron beam to crosslink the resin plate. The polyolefin resin plate used in the present invention is a homopolymer of olefin, a copolymer of olefin, a copolymer of olefin and a vinyl compound,
Alternatively, polyolefin resins such as derivatives of these halides can be used as substrates, with compositions prepared by adding processing aids, stabilizers, flame retardants, fillers, etc. to one or more of these polymers as necessary. It has become. In addition, the polyolefin resin may optionally contain a polymer having good compatibility with the liquid polybutadiene resin, in order to improve the adhesion with the composite formed by impregnating a nonwoven fabric or a woven fabric with the liquid polybutadiene resin. For example, it is also possible to incorporate polybutadiene resin. The nonwoven fabric or woven fabric used in the composite according to the present invention is a fibrous cloth-like article having a thickness of 5 to 100 μm and made of insulating and highly heat resistant fibers such as glass fibers. In the present invention, the liquid polybutadiene resin to be impregnated into the non-woven or woven fabric is a low-molecular to medium-molecular weight material such as a butadiene homopolymer, a copolymer with other functional compounds, or a modified product thereof. A liquid polymer that has unsaturated bonds or functional groups in the main chain or side chain of the molecule, and is cured by adding a crosslinking agent such as peroxide or by heating or other means as necessary. It can be cured by To explain in detail the method for forming the composite according to the present invention, for example, a composition obtained by adding a crosslinking aid and, if necessary, auxiliary materials such as a flame retardant and a stabilizer to a liquid polybutadiene resin is diluted with a solvent. It is produced by impregnating a nonwoven fabric or woven fabric with the compound, volatilizing the solvent, drying it, and then semi-curing it by means such as heating if necessary. The above composite is sandwiched between two polyolefin resin plates, at least one of the two resin plates, and a metal foil present on the outer surface of the resin plate. The resin plate may be sandwiched and pressurized to form an insulating substrate, and then the composite may be sandwiched between this insulating substrate and metal foil and heated and pressurized, or the composite may be sandwiched at the same time and then heated and pressurized all at once. Generally, the effect of the present invention does not particularly differ depending on the order of sandwiching. The temperature and pressure conditions for adhering the polyolefin resin plate, composite, and metal foil to each other and bonding them by applying heat and pressure are the temperature at which the polyolefin resin used is melted, and the temperature at which the liquid polybutadiene resin is cured or higher. It is necessary to apply pressure to an extent that does not leave defects such as bubbles at the interface of each material. Irradiation conditions for crosslinking polyolefin resins by electron beam irradiation are determined based on the crosslinking reaction characteristics of the polyolefin resin used, but the irradiation dose of electron beams is usually 0.5 to 60 megarads (Mrad), preferably 5 to 40 megarads. It's Megarad. The present invention will be explained below using examples. however,
It goes without saying that the structure of the substrate, etc. can be changed without being limited to the following embodiments without departing from the characteristics of the manufacturing method based on the present invention. Example 1 Composition 1 shown in Table 1 was used at 150°C x 10
It was pressed for a minute to create a resin plate with a thickness of 0.4 mm. In addition, NISSO is applied to the plain weave glass cloth with a thickness of 30 μm.
-PB B-1000 (liquid polybutadiene, manufactured by Nippon Soda Co., Ltd., trade name) 100 parts by weight, dicumyl peroxide 2 parts by weight, and methyl ethyl ketone 100 parts by weight
After impregnating with an impregnating solution consisting of parts by weight, methyl ethyl ketone was removed by drying, and heating was performed at 150° C. for 15 minutes to produce a semi-cured composite made of polybutadiene-impregnated glass cloth. The composite is sandwiched between the resin plates to form an insulating base, and the insulating base is further bonded with a 40μ
m copper foils are brought into close contact via the composite,
Heat and pressurize at 50Kg/ ^cm2 for 10 minutes at 150℃,
After cooling, it was taken out and irradiated with a 25 megarad electron beam to obtain a hard substrate for printed wiring with an insulating substrate thickness of 0.8 mm. The obtained substrates were examined for electrical properties, flatness, and the presence or absence of abnormalities by immersing them in a 280°C solder bath for 10 seconds. The results are shown in Table 2. It was found that the substrate obtained in Example 1 had a small dielectric constant of 2.4, sufficient flatness, and excellent solder resistance. Example 2 Using Composition 2 shown in Table 1, a resin plate with a thickness of 0.4 mm was prepared by pressing at 150°C for 10 minutes. Instead of NISSO-PB B-1000 in Example 1, BF-
1000 (epoxidized liquid polybutadiene, trade name, manufactured by Adeka Argus Chemical Co., Ltd.) and under the same conditions as shown in Example 1, a semi-cured composite consisting of glass cloth impregnated with epoxidized liquid polybutadiene was produced. Next, in the same manner as in Example 1, the resin plate/composite body/resin plate/composite body/copper foil structure was closely pressed together, heated and pressed under the same conditions as in Example 1, irradiated with an electron beam, and printed wiring was formed. A rigid substrate for use was obtained. This substrate was also subjected to the same test as in Example 1, and the results shown in Table 2 were obtained. This substrate also had a low dielectric constant of 2.8, and had good flatness and solder resistance. Comparative Example 1 Using Composition 1 shown in Table 1, a resin plate with a thickness of 0.8 mm was prepared under the same conditions as in Example 1. Next, the above resin plate and 40 μm copper foil were brought into close contact with each other via the same semi-cured composite as that prepared in Example 1, and a hard substrate for printed wiring was obtained under the same conditions as in Example 1. The same tests as in Example 1 were also conducted on this substrate, and the results shown in Table 2 were obtained. This board had good electrical properties and solder resistance, but
It is too curved to be used as a hard board for printed wiring. Comparative Examples 2 and 3 Commercially available glass-epoxy hard substrate (Comparative Example 2)
and a glass-triazine hard substrate (Comparative Example 3), the same tests as in Example 1 were conducted, and the results shown in Table 2 were obtained. All have dielectric constants of 4 or more, and are not completely satisfactory as printed wiring boards.

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Claims (1)

[Claims] 1 A composite formed by impregnating a nonwoven fabric or a woven fabric with a liquid polybutadiene resin and semi-curing is present between two polyolefin resin plates, at least one of the two resin plates, and on the outer surface of the resin plate. A method for producing a hard substrate for printed wiring, comprising sandwiching the resin plate between the resin plate and a metal foil, heating and pressurizing the resin plate, and then irradiating the resin plate with an electron beam to crosslink the resin plate.