JPH04169232A - Continuous manufacturing method of flexible printed wiring board - Google Patents

Abstract

PURPOSE:To improve outside appearance of products and prevent losses of resins by a method wherein, when foils or air shielding films are applied to the opposite sides of a substrate impregnated with radical curing resin composition, they are passed through rolls provided with a resin flow prevention means. CONSTITUTION:Radical curing resin compositions are in liquid form at ambient temperature and can be cured without producing volatile by-products. These compositions are radical polymerization resins, crosslinking monomers and compositions containing catalysts. Base materials are aromatic polyamide fibers and glass fibers. Air shielding films are polyester films and polyimide films. Metal foils of electrolytic copper or rolled copper are preferable. Curing resin liquid is impregnated into a long base material of reel 1 by means of a coater 3. The air shielding films and/or metal foils of reels 4, 5 are stacked on the base material by means of a roll 6 provided with a resin flow prevention means 14, which material is sent to a heating furnace 7, where the thickness thereof is adjusted by a roll 13 before it is gelatinized. Cured laminated plate 11 is wound up by a winding machine 9. The air shielding films from the reel 4 are separated from products and wound up by a winding machine 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously manufacturing a substrate for a flexible wiring board. The term "substrate for flexible wiring board" as used herein means a substrate having metal foil on one or both surfaces thereof, and an unclad board having no metal foil on either surface.

'- and its mouth Patent Applications Hei 1-251546 and Kai-Hei 1-31 filed by the applicant
7133 uses an aromatic polyamide fiber nonwoven fabric as a base material, impregnates it with a radical curable resin composition that is liquid at room temperature and can be cured without producing volatile byproducts, and laminates metal foil if necessary. A method for continuously manufacturing a substrate for a flexible wiring board, which comprises heating and curing, is disclosed. By this method, a board with excellent solder heat resistance, flexibility, dimensional stability, and electrical performance can be manufactured at relatively low cost. In this method, the thickness of the product substrate can be controlled by impregnating the substrate with some excess resin composition, adjusting the clearance between the laminating rolls when laminating the metal foil and/or air barrier film, and reducing the excess. A method has been adopted in which the resin is removed and the coating is compressed to a predetermined thickness. According to this method, the removed resin adheres to the metal foil and/or air barrier film or conveyance roll, damaging the appearance of the product, and the removed resin composition cannot be recovered and reused due to bond life. In some cases, resin is likely to be wasted. For applications where low prices are required, such as printed wiring boards used in consumer electrical and electronic equipment, it is desirable to eliminate this waste of resin and further improve cost performance.

Therefore, the present invention impregnates a substrate continuously supplied with a radical-curable resin composition that is liquid at room temperature and can be cured without producing volatile by-products. A method for continuously producing a substrate for a flexible wiring board, which comprises coating both sides of a metal foil and/or an air-blocking film, and heating and curing the coated material in a constant state equipped with a means for preventing resin outflow. The method is characterized in that the thickness is controlled by passing the film between two rolls having a clearance of .

A radical-curing resin composition that is liquid at room temperature and can be cured without producing volatile by-products when pressed and rubbed on the skin is composed of a radical polymerizable resin, a crosslinking monomer, and a catalyst (polymerization initiator). This is a liquid resin composition containing (side).

As the radical curable resin, oligoacrylate resins such as unsaturated polyester resins, vinyl ester resins, urethane acrylate resins, and polyester acrylate resins are used. Unsaturated polyester resins include unsaturated dibasic acids such as maleic anhydride, fumaric acid, and maleic acid; saturated dibasic acids such as succinic acid, adipic acid, azelaic acid, phthalic anhydride, isophthalic acid, and terephthalic acid; ethylene glycol, diethylene glycol,
It is synthesized using glycols such as propylene glycol, dipropylene glycol, and polypropylene glycol as raw materials. Vinyl ester resins are synthesized by ring-opening addition reaction of acrylic acid or methacrylic acid to the epoxy groups of epoxy resins. As the urethane acrylate resin, polyether polyol, polyester polyol, terminal hydroxyl polybutadiene, etc. are used as the polyol component, and diisocyanates such as isophorone diisocyanate and tetramethylxylylene diisocyanate, hydroxyethyl acrylate,
Those synthesized by reacting unsaturated alcohols such as hydroxyethyl methacrylate are used. The polyester acrylate used has a structure in which the oligomer is partially a polyester and has an acryloyl or methacryloyl group at the molecular end or side chain.

As the crosslinking monomer, styrene is used as -a, but α-methylstyrene, vinyltoluene, p-methylstyrene, chlorostyrene, bromostyrene, divinylbenzene C1-CIO alkyl methacrylate, CI-C
Monomers such as OO alkyl acrylate, hydroxyalkyl acrylate, hydroxyalkyl methacrylate, diallyl phthalate, triallyl cyanurate, glycidyl acrylate, glycidyl methacrylate and their mixtures with styrene can also be used.

The blending amount of the crosslinking monomer is 10 to 70% by weight in the composition,
Preferably it is 20 to 60% by weight.

As the catalyst, organic peroxides such as peroxyketals, peroxyesters, and dialkyl peroxides are used in an amount of 0.5 to 2.0 parts per 100 parts of the resin composition.

As the base material, nonwoven fabrics such as aromatic polyamide fibers, glass fibers, carbon fibers, liquid crystal polymer fibers, and polyimide fibers can be selected. Usually thickness 30-200μ, apparent density 0.3-0.7g/C11Y, more preferably 0
．． 4 to 0.6 g/aaO is used. It is also preferable to perform silane coupling agent treatment, other resin treatment, etc. prior to resin impregnation.

A nonwoven fabric containing aromatic polyamide as a main component is particularly preferred, and in this case, the aromatic polyamide includes polyparaphenylene terephthalamide, polymetaphenylene isophthalamide, and the like.

A material having a high content of para-aromatic polyamide such as polyparaphenylene terephthalamide is preferable from the viewpoint of dimensional stability and heat resistance.

The film-like air barrier is preferably a film having surface smoothness in terms of product performance, such as polyester film, polyimide film, cellophane film, release-treated film thereof, silicone release paper, and the like.

As the metal foil, electrolytic copper foil, rolled copper foil, electrolytic aluminum foil, etc. are preferable. A flexible laminate using these metal foils can be used as a flexible printed circuit board.

FIG. 1 is a process explanatory diagram showing a typical embodiment of the present invention.

The long base material unwound from the reel 1 is passed through a dryer 2 and dried as required. Excessive moisture contained in the base material reduces the soldering heat resistance required of the metal-clad laminate, and often causes blistering during soldering, which is undesirable. Furthermore, when heated to harden the resin, voids may be generated due to the generation of water vapor. The base material stored in the atmosphere is desirably dried under drying conditions of about 110°C x 10 minutes.

After drying, the base material is continuously and quantitatively impregnated with a radical curable resin liquid by a resin impregnation coater 3.

In order to achieve good impregnation and impregnation rate, it is preferable to appropriately select the viscosity of the resin liquid and the apparent density of the base material. Generally, the lower the viscosity of the resin liquid, the higher the impregnating property. The viscosity can be lowered by increasing the proportion of liquid monomer in the resin liquid and lowering the molecular weight of the radical-curing resin.
An excessive decrease in viscosity is undesirable because it impairs the heat resistance, mechanical strength, and flexibility of the resulting product. Using a base material with a low density also improves impregnability, but lowering the density more than necessary impairs the mechanical properties, dimensional stability, and processability of the product. In the present invention, the viscosity of the resin liquid at 25°C is 0.5 to 3.
0 void and the density of the base material is 0.3 to 0.1 g/d
The desired result is obtained when . More preferably, the viscosity of the resin liquid is 2 to 20 voids, and the density of the base material is 0.4.
~0.6g/cffll. In addition, the impregnation method may be a method such as immersing the base material in the resin liquid, but it takes time to remove air bubbles, etc., and in the present invention, which is aimed at a continuous production method, it is necessary to ensure a good impregnated state. It is preferable to impregnate the resin liquid from one side of the base material.

Next, the metal foil and the air barrier and/or the metal foil fed out from the reels 4 and 5 are laminated onto the impregnated base material using a laminating roll 6.

The uncured laminate 10 is sequentially introduced into the heating furnace 7.

It is preferable that the heating furnace 7 is normally heated to 70°C to 150°C. Curing conditions vary depending on the amount and type of catalyst used, and the type and amount must be set in consideration of the pot life and curing characteristics of the resin liquid.

Thickness accuracy can be improved by adjusting the thickness by passing the resin through the gap between two or more rolls 13 in which the clearance in the curing furnace can be maintained constant just before the resin completely gels.

Although it is effective to use two or more sets of rolls, it is preferable to install two or more sets of rolls in succession to greatly improve the thickness accuracy. However, when such a roll is provided, it is important to install it at a position immediately before gelation. The thickness is substantially determined by this clearance, and it is preferable that this clearance is narrower than the clearance of the laminating roll 6 by 5 to 30 μm. Next, the cured laminate 11 is continuously taken up by a take-up machine 8 and wound up by a product wind-up machine 9. If the reel 4 is a film air barrier,
At step 8, it is peeled off from the product and wound up by a winder 12. Curing may be completed at this stage, but it may be cured to a state where it can be rolled up, and then after-cured for an appropriate period of time.

According to the present invention, as shown in FIG.
is equipped with resin outflow prevention means 14. The resin outflow prevention means has an arcuate side complementary to the outer circumferential surface of the laminating roll 6 (a wedge-shaped plate member is used), and a metal foil and/or air-blocking film coating that is in contact with the outer circumference of the upper and lower rolls of the roll 6 is used. These wedge-shaped plate members are provided on both sides of the impregnated base material in contact with both ends of the surface side thereof, and are opposed to each other in parallel with both edges of the impregnated base material. The resin liquid accumulated between the rolls is prevented from flowing out laterally beyond the wedge-shaped plate member, and is prevented from adhering to the edges of the metal foil or air barrier film, or even between the roll 6 and the metal foil or air barrier film. This prevents the resin from entering the gaps between the parts and contaminating the metal foil and air-blocking film on the surface of the coated impregnated base material, as well as contaminating peripheral equipment.In addition, the supplied resin liquid is used without wasting it. Helps reduce costs.

Furthermore, as shown in Figure 2, a small amount of resin is dripped onto the metal foil or air barrier film from between the two rolls in contact with the coated surface of the metal foil or air barrier film on the lower side before being coated. By providing a receiving flat plate or bent plate 15 in combination with 14, it is possible to prevent the resin from flowing downward on the foil or film and contaminating the back side of the metal foil or air-blocking film or contaminating peripheral devices. .

Also, as shown in FIG. 3, in contact with the upper part of the impregnated base material 17,
In addition, a pair of half-wedge-shaped plate members 16 having arcuate sides complementary to the roll outer peripheral surface provided in contact with the metal foil or air-blocking film in contact with the upper roll are attached to the inside of the wedge-shaped plate member 14. By installing the rollers parallel to each other and facing each other, the resin liquid accumulated on the impregnated base material in front of the roll 6 is prevented from flowing out to the side beyond the width of the impregnated base material, and the amount of resin supply rain is kept to the necessary minimum. This makes it possible to approach the limit, which helps reduce costs.

Although the invention has been described with particular embodiments, those skilled in the art will recognize that variations and modifications will occur within the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of the present invention, and FIGS. 2 and 3 are front views of the resin outflow prevention means. 1, base material 2, dryer 3, coater for resin impregnation 4, film air barrier or metal foil 5, metal foil or film air barrier 6, laminating roll 7, curing furnace 8, take-up machine 9, product roll Take-up machine 10, uncured laminate 11, cured laminate 12, film air barrier winder 13, two parallel rolls 14, 15.16. Resin outflow prevention means 17, impregnated base material

Claims (4)

[Claims] (1) A continuously supplied base material is impregnated with a radical curable resin composition that is liquid at room temperature and can be cured without producing volatile by-products, and metal foil and/or A method for continuously manufacturing a substrate for a flexible wiring board, which comprises coating an air-blocking film and continuously curing it by heating in that state, wherein both sides of an impregnated base material are coated with metal foil and/or an air-blocking film. The method described above is characterized in that the thickness of the resin is controlled by passing the resin between two rolls having a certain clearance and equipped with resin outflow prevention means. (2) The resin outflow prevention means is comprised of a pair of wedge-shaped plate members having arcuate sides complementary to the outer peripheral surface of the roll, which are provided in contact with both ends of the metal foil and/or air-blocking film to be coated. The method of item 1. (3) A flat or bent plate that is placed in contact with the coated surface of the metal foil or air barrier film on the lower side before being coated to catch a small amount of resin that flows down from between the two rolls onto the metal foil or air barrier film. The second one that holds the processed plate at the same time.
Section method. (4) 1 having an arcuate side complementary to the roll outer peripheral surface that is in contact with the upper part of both ends of the impregnated base material before being coated and in contact with the metal foil or air-blocking film that is in contact with the upper roll. 3. The method of claim 2, wherein a pair of half-wedge plate members are inside the wedge plate member of claim 2.