JPH0462154A - Preparation of electric laminated sheet - Google Patents

Abstract

PURPOSE:To prepare an electric laminated sheet reduced in warpage and twist by a method wherein a cover sheet and/or a metal foil is laminated to a laminate of impregnated base materials and the formed laminated sheet is continuously cured and cut to be subjected to post-curing twice or more. CONSTITUTION:A plurality of base material rows are continuously fed in parallel and individually impreqnated with a curable resin solution generating no reaction byproduct to be laminated and unified. Subsequently, a cover sheet and/or a metal foil is laminated to the formed laminated while the laminated sheet thus formed is continuously cured and subsequently cut into a desired dimension. After cutting, post-curing is performed twice or more to obtain an electric laminated sheet improved in warpage and twist. In this case, as the curable resin, an epoxy resin and an unsaturated resin are used and, as the unsaturated resin, an oligoacrylate resin such as an epoxy acrylate resin or a polyester acrylate resin, a spirane resin and a diallyl phthalate resin are designated other than unsaturated polyester.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an electrical laminate having improved warpage characteristics. Here, the electrical laminate refers to an insulating laminate used as a substrate for various electrical and electronic components, and a metal foil-clad laminate used as a printed circuit board.

JP-A-55-4838, JP-A-56-98136, etc. disclose continuous manufacturing methods for electrical laminates.

This method involves impregnating a plurality of substrates individually with a curable resin liquid while continuously conveying them in parallel, stacking and combining the impregnated substrates, and forming a cover sheet and/or metal foil. It consists of a continuous process such as laminating, curing continuously, and cutting.

In this method, it is common to continuously cure the curable resin liquid impregnated into the base material, and then cut it and perform post-curing. However, due to time and mechanical constraints, it has been difficult to perform sufficient post-curing as originally required. In addition, even if post-curing is performed at a higher temperature, it is not sufficient to completely remove internal strains in the laminate, and there is a risk of thermal deterioration of the resin due to exposure to too high a temperature.
There were problems in implementation.

Japanese Patent Laid-Open No. 61-293853 discloses a method of repeating two or more cycles of heating and cooling during heating and pressing in press molding of a laminate. However, even if the laminate is repeatedly heated and cooled using a press molding machine, it is practically difficult to completely remove the internal strain in the laminate. There was a possibility that new distortion would occur during the cutting process of the ends. Furthermore, in the continuous manufacturing method, it is impossible to perform similar heating and cooling continuously due to equipment limitations.

Therefore, even after cutting and post-curing, laminates obtained by conventional continuous manufacturing methods still exhibit large dimensional changes.
There was a problem with warping and twisting. In particular, large warping and twisting occurred when subjected to a flat thermal history such as a solder dip process or a flow process in the processing process.

An object of the present invention is to manufacture an electrical laminate with small warp and twist in a continuous manufacturing method of electrical laminates.

The present invention is characterized in that a plurality of rows of base materials are continuously conveyed in parallel,
The rows of base materials are individually impregnated with a curable resin liquid that is liquid itself and does not generate reaction by-products upon curing, the impregnated base materials are laminated and combined, a cover sheet and/or metal foil is laminated, and a continuous process is performed. A method for producing an electrical laminate, which includes a step of curing the electrical laminate to a desired size and then cutting it into a desired size, the method includes performing post-curing two or more times after cutting. The present invention provides an improved electrical laminate.

In carrying out the present invention, the techniques disclosed in JP-A-55-4838, JP-A-5698136, etc. can be applied, except that post-curing is performed two or more times. In addition, in the case of continuous curing, the equipment and the like are simple when curing is carried out substantially without pressure, and the improvement effect of the present invention is also remarkable.

These continuous methods use curable resins that are liquid at room temperature and do not generate volatile byproducts during curing. Such curable resins include epoxy resins and unsaturated resins. The unsaturated resin refers to a resin in which the resin before curing contains 87 radically polymerizable double bond unsaturated groups and is cured by a radical polymerization reaction of the unsaturated groups. Unsaturated polyester is a typical example, but other examples include oligoacrylate resins such as epoxy acrylate resins and polyester acrylate resins, spiran resins, and diallyl phthalate resins. Applicant's Japanese Unexamined Patent Publication No. 62-7
The resin composition disclosed in No. 4913 has excellent properties as an electrical laminate and is an example of a resin preferred for use in the present invention.

Curable resins can be rendered flame retardant by containing halogen atoms, particularly bromine, bound to their skeletons.

It can also be achieved by adding an additive type halogenated flame retardant to a resin that does not contain halogen.

A catalyst or polymerization initiator is required for curing of radical polymerizable resins. Organic peroxides are common as polymerization initiators, and a large number of them are known. It is particularly preferable to use those selected from aliphatic peroxyesters alone or in combination.

Specifically, for example, di-t-butyl peroxide, 2
,5-dimethyl-2,5-di(t-butylperoxy)
These include hexane, acetyl peroxide, isobutyryl peroxide, t-butylperoxy-2-ethylhexanoate, and the like.

Aliphatic peroxyesters include, for example, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, t-butylperoxylaurate, etc. say.

As the base material, a paper base material such as kraft paper or linter paper, glass cloth, or nonwoven fabric can be used. Glass cloth is usually made of 5 glass filaments with a thickness of about 9 μm.
It is a general term for cloth in which 0 to 800 yarns are woven vertically and horizontally in various weaving methods such as satin weave, plain weave, open plain weave, and twill weave. As a non-woven fabric, the thickness is 1 to 2.
A long sheet-shaped glass nonwoven fabric (also called glass paper) made by dispersing 0 μm glass fibers in water and using a binder such as acrylic resin, polyvinyl alcohol, epoxy resin, or melamine resin, or paper and glass. There are also glass-mixed paper made of fibers, synthetic fibers such as polyester, and nonwoven fabrics made of rayon, asbestos, rock wool, etc. Part of the nonwoven fabric can also be replaced with paper. In a composite structure in which a nonwoven fabric is used as an intermediate base material layer, one layer or several layers of nonwoven fabric can be used on the inside depending on the thickness of the board.

In addition, in a composite structure, in order to improve the dimensional stability in the thickness direction, an inorganic filler is usually used, and the inorganic filler is water-insoluble and insulating. Examples include metal oxides such as silica, alumina, zirconia, titanium dioxide, and zinc white, metal hydroxides such as magnesium hydroxide and aluminum hydroxide, talc, kaolin, mica, wollastonite, and clay minerals. Natural minerals, calcium carbonate, magnesium carbonate,
Examples include insoluble salts such as barium sulfate and calcium phosphate.

The inorganic filler can be filled by dispersing it in an impregnating resin solution in advance, or by impregnating a glass substrate with the inorganic filler directly mixed in, or by impregnating it with a curable resin solution, or by impregnating it with a curable resin solution, or by impregnating it with a curable resin solution, or by impregnating it with a curable resin solution. Although there is a method of impregnating a glass substrate with a resin liquid and then filling the glass substrate with a filler, either method may be used, or they may be used in combination. Generally, the filler is dispersed in the impregnating resin liquid in advance.

In the present invention, the method for continuously curing the substrate impregnated with the curable resin liquid is generally carried out by continuously passing it through a tunnel-type curing furnace.

The temperature conditions, time, etc. for continuous curing can be appropriately determined depending on the required production volume, mechanical ability, amount of catalyst, etc. After passing through a tunnel-type curing furnace, it is cut into predetermined dimensions. Thereafter, post-curing is performed for the purpose of completely terminating the reaction or removing internal strain, and the present invention is characterized in that post-curing is performed two or more times. The conditions for post-curing are: Tg or higher of the resin used;
Preferably, the desired effect can be obtained by leaving it at a temperature 10°C or more higher than Tg for at least 5 minutes at a time, and even better effects can be obtained by leaving it preferably for 10 minutes or more.

In the present invention, it is essential to carry out post-curing at least twice, and it may be carried out three or more times if necessary. However, if the process is repeated three or more times, there is a possibility that the resin will deteriorate due to heat, so it is necessary to pay attention to the properties of the resin.

In addition, the second and subsequent post-curing needs to be performed after the heating performed immediately before is cooled to at least Tg or lower, and preferably after cooling to a temperature 10'C or more lower than Tg, according to the present invention. It is possible to obtain a laminate with small warpage and twist, which is the objective of the method.

The present invention will be explained in detail below with reference to Examples.

Example: One sheet of glass cloth with a thickness of 180 μm and a basis weight of 210 g/rrT was placed in the upper and lower outermost layers, and three sheets of glass paper with a basis weight of 40 g/rrT were placed in the middle, and these base materials were continuously rolled from a roll. Pay out and individually add commercially available unsaturated polyester resin (Takeda Pharmaceutical Polymer 6311.Tg approx. 100
``C) Copper foil with a thickness of 18 μm impregnated with a resin liquid consisting of 90 parts by weight, 10 parts by weight of styrene, 1 part by weight of benzoyl peroxide, and 50 parts by weight of aluminum hydroxide, combined, and coated with an epoxy adhesive. It was laminated on both sides and cured for 30 minutes at 110°C by passing through a tunnel furnace before being cut. It was then post-cured for 150°CIO minutes, cooled to 60"C, and then cured again at 150"C for 10 minutes. After curing, a double-sided copper foil-clad laminate having a thickness of 1.6 mm was obtained.

Comparative Example 1 A double-sided copper foil-clad laminate with a thickness of 1.6 cm was obtained by the same operation as in the example except that post-curing was performed only once at 150° CIO.

Comparative Example 2 A double-sided copper foil-clad laminate with a thickness of 1.6 cm was obtained by the same operation as in the example except that post-curing was performed only once at 180° CIO.

The performance of the laminates of Examples and Comparative Examples is shown in the table below.

(1) Method for evaluating warpage after heating The laminate produced by the above method is cut into a size of 250 x 250, and the copper foil on one side is completely removed by etching. After that, heat treatment was performed at 170°C for 30 minutes, and the side with the remaining copper foil was placed on the glass flat plate facing down.The distance from the four corners of the laminate from the glass flat plate was measured and the maximum value was measured. I asked for

(2) Method for measuring heat shrinkage rate Create a 200 mm x 20 mm long TD sample with full etching on both sides, and 10 nn from each end in the longitudinal direction.
Mark the position. The distance of that mark is 170”C30
The heat shrinkage rate is measured before and after the heat treatment.

Claims (4)

[Claims] (1) While continuously conveying a plurality of substrate rows in parallel, the substrate rows are individually impregnated with a curable resin liquid that is liquid itself and does not generate reaction by-products during curing, and the impregnated base material is In a method for producing electrical laminates, which includes a step of laminating and combining materials, laminating a cover sheet and/or metal foil, curing continuously, and then cutting into desired dimensions, post-curing is performed twice after cutting. A method for manufacturing an electrical laminate, characterized by carrying out the above steps. (2) The method for manufacturing an electrical laminate according to item 1, wherein the curable resin liquid contains as a main component an unsaturated polyester resin, an oligoacrylate resin, or a mixture thereof. (3) The method for producing an electrical laminate according to items 1 and 2, wherein the base material is a glass base material. (4) The method for producing an electrical laminate according to items 1 and 2, wherein the base material used on both outer sides is glass cloth, and the inner side is a nonwoven fabric.