JPS6052939B2 - metal foil laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved metal foil laminate consisting essentially of an unsaturated polyester resin, a base material based on cellulose fibers, and a metal foil.

Conventionally, various configurations of metal foil-clad laminates have been put into practical use for use in printed circuit boards, but in particular, those using paper whose main component is cellulose fiber as a base material are those using phenolic resin. Generally, a laminate is made of paper and paper or epoxy resin and paper, and metal foil is pasted on one or both sides of the laminate, and the material of the laminate is basically unsaturated polyester resin. Metal foil-clad laminates made of paper and paper have not been commercially put to practical use at all. 1. As is well known, unsaturated polyester resins usually contain liquid crosslinking vinyl monomers such as styrene monomers, which makes it difficult to form non-adhesive prepregs, making it difficult to form a non-stick prepreg. Difficult to adapt. In addition to these manufacturing difficulties, unsaturated polyester resins have poor wettability with cellulose fibers and typically have a higher viscosity than phenolic resin varnishes or epoxy resin varnishes. 3. The bonding strength between the cured unsaturated polyester resin and the cellulose fibers may not be sufficient, resulting in poor moisture resistance and mechanical properties. This is thought to be due to reasons such as unstable mechanical strength and punching workability. Regarding No. 1, a method for obtaining a non-adhesive prepreg is disclosed, for example, in Japanese Patent Publication No. 48-297 or Japanese Patent Application Laid-Open No. 52-92288.

Regarding 2, there is a method of adjusting the viscosity by mixing solvents, such as when using phenol resin or epoxy resin. A method of direct co-immersion production without using a solvent by optimizing the specific gravity and impregnation method is disclosed.

Regarding 3, a method for manufacturing reinforced plastics that is pretreated with melamine resin is disclosed in Japanese Patent Publication No. 13781, but there are no practical examples of its application to metal foil-covered laminates intended for use in printed circuit boards. Not known.

In view of the above circumstances, the present invention was achieved as a result of intensive research aimed at obtaining an improved metal foil-clad laminate whose main constituent materials are unsaturated polyester resin, paper, and metal foil.

That is, the present invention provides a metal foil-clad laminate basically consisting of an unsaturated polyester resin, paper mainly composed of cellulose fibers, and metal foil, in which (a) the surface of the cellulose fibers constituting the base material is substantially (b) Composite fibers made of the melamine resin and cellulose are bonded by an unsaturated polyester resin present as a matrix to form a laminate. This is a metal foil-clad laminate.

Such a metal foil-clad laminate has a structure in which melamine resin is interposed at the interface between the unsaturated polyester resin and the cellulose fibers, resulting in a strong bond between the unsaturated polyester resin and the cellulose fibers; According to the publication, when used as a printed circuit board, 1) the bending strength is improved, and 2) the undesirable whitening that often occurs due to peeling of the unsaturated polyester resin and cellulose fibers during punching is improved. In particular, when exposed to a humid environment 1, moisture resistance and water resistance are improved, and damage to the adhesive interface of the metal foil at molten solder temperature is slight, improving soldering heat resistance and reliability. do.

3. When exposed to a humid environment, the moisture resistance and water resistance are improved, and the deterioration of the peel strength of the metal foil is improved.

4. It was also found that the excellent electrical insulation properties of unsaturated polyester resin can be effectively exhibited.

The base material mainly composed of cellulose fibers used in the present invention is preferably linter paper, cotton paper, kraft paper, etc., and may be either bleached paper or unbleached paper, or cotton cloth or monofilament paper. .

Preferred paper density is 0.3g/al to 0.7g/Clt
Generally speaking, it is around 0.5f/CIL. Any well-known melamine resin can be used to coat cellulose fibers, which are the main component of paper, but methylolmelamine is preferred. Also, patent application No. 54-121180 (Japanese Unexamined Patent Publication No. 56-4
The present invention is not limited to the use of a condensate or a mixture of a melamine resin and a third component as disclosed in Japanese Patent Application No. 3329). The melamine resin as used in the present invention includes condensates and mixtures with such a third component. If the melamine resin that substantially covers the cellulose fibers is excessive, it impairs the impregnating properties of the unsaturated polyester resin, which is an inconvenience in manufacturing. Preferably, the amount is on average 5 to 3 percent by weight.

When the amount is less than 5% by weight on average, the cellulose fibers tend to be partially covered with the melamine resin, increasing the difficulty in manufacturing. In practice, such a weight ratio is determined, for example, by weighing a 10 Crri paper test piece. A good method for coating cellulose fibers is to impregnate paper with a solution and dry it, but it is also possible to coat cellulose fibers in advance and then process them into a sheet. Metal foil can be bonded without using a special adhesive by adopting a manufacturing method such as laminating it together before the unsaturated polyester resin has finished curing, forming a metal foil-covered laminate. However, it is preferable to attach them using an adhesive. It has been found that epoxy resin-based adhesives are particularly suitable. An epoxy resin adhesive in which the curing agent is a polyamide resin has appropriate flexibility and is therefore advantageous in ensuring the peel strength of the metal foil.

Further, when bonding metal foils together using an adhesive, there is a preferable thickness of the adhesive layer.

In general, a metal foil-clad laminate has a thickness of 0.7 TIr! n~2.
``Something of a certain degree is often used. The thickness of the laminate in the present invention is 0.7Tn to 2.0W! t, and the thickness of the adhesive layer is 11,100 to 20 times the thickness of the laminate.
It has been found that a range of 1100 is preferable. Metal foils are commercially available for use in printed circuit laminates. For example, 1 oz/Ft2 electrolytic copper foil is good. If the thickness of the adhesive layer is less than 1/100 of the thickness of the laminate, it will not be able to absorb the thermal shock caused by the soldering temperature, resulting in a decrease in soldering heat resistance, a decrease in surface insulation properties, and the like. If the value exceeds 201,100, the adhesive layer is too thick and mechanical strength becomes a problem when comparing products of the same thickness. The unsaturated polyester resin constituting the metal foil-clad laminate according to the present invention may be either liquid or solid at room temperature, but one that is liquid at room temperature is particularly preferred.

As the unsaturated polyester resin liquid, those having a molecular structure that is generally well known can be used, and this is mixed with a crosslinking monomer.

Furthermore, a general-purpose organic peroxide is added as a curing catalyst, and a curing accelerator is added as necessary during curing.

When curing an unsaturated polyester resin liquid, a curing catalyst (polymerization initiator) is usually added and an organic peroxide is generally used. When organic peroxides selected from aliphatic peroxides, particularly preferably aliphatic peroxyesters, are used alone or in combination, electrical laminates with significantly reduced odor can be produced. . However, the present invention is not limited to these, and it is of course possible to use known curing catalysts such as light-sensitive curing catalysts and radiation-sensitive curing catalysts, together with peroxide or alone.

In addition, it is preferable that the glass transition temperature of the cured product is about 20 to 80° C. from the viewpoint of low-temperature punchability.

For example, a liquid at room temperature with a viscosity of 0.1 to 15 poise is used, which is advantageous because it can be directly impregnated onto the substrate and does not require a drying step. Moreover, in the present invention in which cellulose fibers are coated with a melamine resin, wettability is improved and good impregnating properties are ensured, which is preferable from this point of view. The weight ratio of unsaturated polyester resin in the laminate is generally about 30 to 80%,
Approximately 50 to 70% is suitable.

In the present invention, the unsaturated polyester resin includes, for example, vinyl ester resin.

Further, if the unsaturated polyester resin present as a matrix is sufficiently present between a plurality of base materials to separate the base materials from each other and prevent them from coming into contact with each other, favorable results can be obtained in terms of electrical properties and the like. The present invention will be described in further detail with reference to Examples below.

Example Commercially available kraft paper (MKP-150 manufactured by Tomogawa Paper Industries) having a weight of 150y/771' and a density of about 0.5 was (
) Cut the pieces into pieces of 30cm x 30mm, gently immerse them in a suspension treatment solution consisting of 100 parts by weight of water, 15 parts by weight of methylolmelamine, and 2 parts by weight of oleic acid monoglyceride, and let them stand for a while. Thereafter, it was gently pulled up, squeezed between squeezing rolls, and dried at 130°C twice.

This product was observed using a stereoscopic microscope and a scanning electron microscope, and it was confirmed that the surface of the cellulose fibers was uniformly coated with the melamine resin. This product had a weight increase of 12.8% compared to the paper weight. Six sheets of paper in which the surface of cellulose fibers was coated with melamine resin were prepared, and the glass transition temperature of the commercially available cured product was 6.
Six sheets were impregnated with unsaturated polyester resin at 0°C, and then epoxy resin (Epicoat 828 (Shell Chemical Co., Ltd., 10 parts) and ■-125 (7 parts), manufactured by Henkel Japan) was applied to this material in advance. Electrolytic copper foil coated uniformly to a thickness of 60 pm (T7 manufactured by Fukuda Metals, 1 oz/F)
t2) and heat-cured to obtain a copper foil-clad laminate with a thickness of about 1.6 mm.

The weight ratio of the unsaturated polyester resin in the laminate excluding the copper foil and adhesive layer was 60%. This product showed the characteristics shown in the table below.

Incidentally, as an example of a preferable manufacturing method for manufacturing the metal foil-clad laminate of the present invention, a continuous manufacturing method is as follows.

A large number of base materials impregnated with an unsaturated polyester resin liquid that is liquid at room temperature are conveyed continuously, and then they are stacked, and the metal foil to be bonded is laminated on one or both sides at the same time or later, but the metal foil is not laminated. The surface is appropriately covered with a cover sheet such as a plastic sheet or a metal sheet, and the pressure is applied under substantially no pressure or at a low pressure that does not cause excessive flow of the impregnated resin liquid (preferably 10k9/Clt or less, more preferably 5k9/Clt or less). Clt or less) and transported to a thermosetting furnace for curing.

Claims (1)

[Scope of Claims] 1. A metal foil-clad laminate basically consisting of an unsaturated polyester resin, a base material mainly composed of cellulose fibers, and metal foil, in which (a) the surface of the cellulose fibers constituting the base material is A metal foil-clad laminate that is substantially coated with a melamine resin, and (b) composite fibers made of the melamine resin and cellulose are bonded by an unsaturated polyester resin present as a matrix. . 2 The ratio of the melamine resin coating the cellulose fibers is on average 5 to 30% of the weight of the cellulose fibers.
The metal foil-clad laminate according to claim 1, which is a weight percentage. 3. The metal foil-clad laminate according to claims 1 and 2, wherein the metal foils are laminated together using an epoxy resin adhesive. 4. The metal foil-clad laminate according to claim 3, wherein the curing agent of the epoxy resin adhesive is a polyamide resin. 5. The laminate according to any one of claims 1 to 4, wherein the thickness of the laminate is within the range of 0.7 to 2.0 mm. 6 The thickness of the adhesive layer is 1/100 to 2 of the thickness of the laminate
Claims 3 to 5 within the range of 0/100
The metal foil-clad laminate according to any one of Items 1 to 1. 7. The metal foil-clad laminate according to any one of claims 1 to 6, wherein the metal foil is an electrolytic copper foil.