JPH03110157A - Production of laminated sheet - Google Patents

Abstract

PURPOSE:To produce a laminated sheet with excellent high frequency characteristics in a continuous technique and to improve dimensional stability by laminating prepregs made of a fluororesin porous sheet as a base material in layers while they are continuously transferred, feeding continuously them in a double belt, performing laminate molding thereof, cutting it into a specified dimension, performing aftercuring thereof and thereafter quenching it. CONSTITUTION:A prepreg 1 is prepd. in continuous lengths by using a porous sheet of a fluororesin as a base material. The prepregs 1 are continuously fed through guide rolls 6 and are continuously put in layers by means of laminating rolls 7. While a laminate 5 wherein the prepregs 1 and if necessary, a metal foil 10 are put in layers is continuously transferred, it is preheated and continuously introduced in a double belt 2. The laminate 5 is passed through the double belt 2 and heat-pressed by means of press-heating apparatus 11 between upper and lower endless belts 3 and 4 to obtain a laminated sheet A. The laminated sheet A cut in a specified dimension is introduced in an aftercuring oven to perform aftercuring thereof and the laminated sheet A is quenched just after it is taken out of the aftercuring oven.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a laminated board used as a printed wiring board by a continuous method.

[Prior art 1] Laminated boards are usually prepared by preparing prepreg by impregnating and drying a thermosetting resin using paper or lath cloth as a base material, and cutting this prepreg into predetermined dimensions. Layer multiple sheets of prepreg cut to a fixed size and metal foil such as copper foil if necessary, set this in a press machine with a plate stacked 10 to 14 ffi, and heat and press for a predetermined time using upper and lower heating plates. Manufacture is carried out by multi-stage lamination molding. However, when manufacturing laminates by multi-stage lamination molding like this,
Since it is a batch operation, the work efficiency is poor and there are many problems in productivity. For this purpose, the present applicant has proposed a method of manufacturing a laminate using a continuous method, such as in Japanese Patent Laid-Open No. 189439/1983. In other words, multiple sheets of long prepreg are piled up and continuously fed, and if necessary, a long metal foil is piled up, and this is continuously passed through a double belt and heated and pressurized by the double belt. ,
This allows the laminated plates to be formed continuously. According to this method, since the laminate can be manufactured in a continuous molding operation, the production efficiency is significantly improved compared to multi-stage lamination molding using a patch operation. [Problems to be Solved by the Invention] On the other hand, the frequencies used in the fields of electronics, communications, and computers have been shifted to high frequency regions, and in the laminated boards of printed wiring boards used in such high frequency regions, is required to have a smaller dielectric constant in order to shorten signal propagation delay. For this reason, in order to obtain such a laminate with excellent high frequency characteristics, a resin constituting the laminate, that is, a prepreg resin, which has excellent frequency characteristics, such as a patent application published in 1988-5004, has been developed.
Aromatic polyisocyanates such as No. 34 have been used, but resins with excellent high frequency properties are generally used at high temperatures (250 to 300°C in some cases) for long periods of time (
In some cases, it may be necessary to perform molding for 1 to 2 hours. However, when the prepreg is continuously passed through a double belt and molded under heat and pressure, it is impossible to sustain the molding for a long time at high temperatures. It is not possible to manufacture laminates using the above-mentioned continuous method using double belts, and the current situation is that it is difficult to manufacture laminates with excellent high frequency characteristics using the continuous method. . The present invention has been made in view of the above points, and it is possible to manufacture a laminate with excellent high frequency characteristics by a continuous method,
In addition, it is an object of the present invention to provide a method for manufacturing a laminate that can improve dimensional stability. [Means for solving the ff problem] The method for manufacturing a laminate according to the present invention includes continuously feeding a long prepreg 1 prepared using a porous fluororesin sheet as a base material, and manufacturing a required number of prepregs 1, 1... are piled up, continuously fed into the double belt 2 for laminated molding, cut into predetermined dimensions, after-cured, and rapidly cooled after being exposed to 77 Turkey Air. The present invention will be explained in detail below. The prepreg 1 is prepared as a long prepreg by impregnating a base material with a resin varnish and drying it. In the present invention, a porous sheet of fluororesin (polytetrafluoroethylene) is used as the base material. 7#, resin porous sheet is a sheet of 77 resin made porous by providing many small pores with an average particle size of about 1μ or less, for example, the one commercially available from Nitto Denko Corporation. Can be used. Because this sheet is porous with small pores, it can be dipped in thermosetting resin varnish in the same way as paper or glass cloth, allowing the thermosetting resin varnish to penetrate well, making it more durable than conventional paper. Prepreg 1 can be easily prepared using the same method as when using glass cloth as a base material. In addition, in the present invention, the fluororesin porous sheet is impregnated (any resin can be used, but thermosetting resins such as epoxy resins are particularly preferred. Prepreg 1 is unwound from a roll and a predetermined number of sheets are continuously fed through idle roll 6, and each prepreg 1 is continuously overlapped by stacking roll 7.Meanwhile, metal M10 such as copper foil is also It is formed into a long length and wound into a roll, which is then unwound and superimposed on the outer surface of the outermost layer of the above-mentioned superimposed prepreg 1. When producing a double-sided metal foil-clad laminate, two sheets of Metal M10 is used to overlap the outer layer of prepreg 1, and when producing a single-sided metal foil-clad laminate, metal 9i10 is applied only to the outermost layer of one side, and the outermost layer of the other A film such as a fluororesin film that can withstand temperatures of 150°C or more and has high high frequency properties is layered on top of the film.Metal i10 is a film coated with adhesive or a combination of aluminum carrier and ultra-thin copper foil. Any material such as a combination of foils can be used. In this way, while continuously feeding the laminate 5 in which a plurality of prepregs 1 and, if necessary, metal ?i10 are stacked, this After preheating the laminate 5 to melt the resin contained in the prepreg 1, the laminate 5 is continuously applied to a double belt 2 composed of upper and lower endless belts 3.4 that are continuously driven by a drum 9. Preheating is preferably carried out by dielectrically heating the laminate 5 under no pressure or under contact pressure by passing the laminate 5 between the upper and lower high-frequency application electrodes 8, 8. Dielectric heating increases the heating temperature. is higher inside the prepreg 1 rather than at the surface, and when heating externally using electric heat, the surface is high (heated and the curing reaction of the resin on the surface of the prepreg 1 progresses quickly). This prevents air bubbles from being removed from the prepreg 1 even when pressurized by the double belt 2, and it is possible to reduce the occurrence of voids in the laminate. In order to pressurize the laminate 5 between the upper and lower endless bells 3 and 4 through the belt 2, a pressurizing and heating device 11.11 such as a heating plate is disposed within each endless belt 3, 4. The laminate 5 can be heated and pressurized by this pressurizing/heating device 11, and the resin of the prepreg 1 is cured and the plurality of prepregs 1 and metal foils 10 are cured.
This is a method for laminating and bonding. Pressure is 20kg/am2
It is carried out at a low pressure of ~30 kg/c+a2 or less, and in some cases it is carried out at a contact pressure. The laminated body thus laminated is continuously drawn out as the double belt 2 is driven, and is guided to the idle roller 12 and cut with 13 cuts to form a metal foil of a fixed size. It is possible to obtain a laminate A with a high tension. When performing laminated molding using the continuous method as described above,
The 77-base resin porous sheet that serves as the base material of prepreg 1 is
Fluorine, the material? , 41 resin has a low dielectric constant and excellent high frequency properties, so it has high high frequency properties, so there is no need to use a resin with excellent high frequency properties as the impregnating resin, and epoxy resin It is also possible to manufacture the laminate A with high high frequency characteristics even by using materials commonly used for laminates, such as the following. This eliminates the need for long-term molding at high temperatures, which is required when using resin with high high-frequency characteristics, and allows lamination with high high-frequency characteristics by using the conventional continuous method using double belts 2. This makes it possible to manufacture plate A. However, in the continuous construction method using double belt 2, heating can only be performed for a short time with low pressure (at least contact pressure in some cases), so the curing of the resin may be insufficient due to insufficient heat, and the laminate A The dimensional stability is not as good as that produced by multi-stage lamination molding, and there is a risk of significant deformation such as warping. Therefore, in the present invention, the laminate A that has been continuously formed using the double belt 2 and then cut into a predetermined size is introduced into an after-cure furnace to perform after-curing. I try to quickly cool it down immediately after taking it out of the furnace. By performing after-curing, the dimensional stability of laminate A can be improved by compensating for the lack of heat in one of the resins in laminate A, and furthermore, by rapidly cooling after after-curing, the crystallinity of the resin in laminate A can be increased. Therefore, the dimensional stability of the laminate A can be further improved. In performing after-cure, the heating temperature is preferably set to a temperature approximately 10 to 50° C. lower than the heating temperature by the double belt 2, and the heating time is preferably about the same as the forming time by the double belt 2. Further, it is preferable to rapidly cool the laminate A after the after-cure by immersing it in water (at a room temperature of about 25°C), and it is preferable to take it out of the water after it has been cooled to 60°C or less. preferable. [Examples] The present invention will be specifically explained below using Examples. (520 parts by weight of a brominated epoxy resin with an epoxy equivalent of 520, 9 parts by weight of dicyandiamide, 2-ethyl-4-
0.5 parts by weight of methyl imiguzole was added and dissolved in a solvent to obtain an epoxy resin varnish. this)
The del time of the varnish at 160°C was 10 minutes. Then, using a polytetrafluoroethylene porous sheet (thickness 50μ, porosity 85%, average pore diameter 0.6μ) manufactured by Nitto Denko Corporation as a base material, the resin was impregnated with the above epoxy resin varnish and dried. Content is 50% by weight, 1
A prepreg with a del time of 180 seconds at 60°C was obtained. Next, using this prepreg, a laminate was manufactured using the continuous construction method shown in FIG. That is, prepreg 1
Copper foils with a thickness of 0.035 mm were placed on top and bottom of the 0 sheets, and the temperature at the center of the laminate was raised to 120 to 125 using a high frequency dielectric heating device with an oscillation frequency of 13.56 MHz.
℃, the prepreg resin is melted and introduced into a double belt rotating at a speed of 0.1 m/min, and the double belt is heated for 20 minutes at a pressure of 25 kg/0 m2 and a temperature of 170 ℃. Laminate molding was carried out by passing through the laminate, and the laminate was further cut into a size of 1 m x 1 m to obtain a laminate plate with copper cladding on both sides. Next, the laminate immediately after being cut in this way was placed in an after-cure oven at 150° C. for 20 minutes to perform after-curing. Put it in the after cure furnace like this 2
After 0 minutes had elapsed, the laminate was taken out of the after-cure furnace and placed directly in *25°C water for quenching, and when the laminate had cooled to 60°C, it was taken out of the water. Comparative Example 1 was obtained by molding a double-sided copper-clad laminate using the continuous method using double belts in the same manner as in the above example, and leaving it at room temperature for 17 days to cool without applying Turkish air. A double-sided copper-clad laminate was formed using a continuous method using double belts in the same manner as in the above example, and after-cured in the same manner as in the example.The laminate taken out from the after-cure furnace was heated at room temperature. Comparative Example 2
And so. 205g/m of the epoxy resin varnish used in the above example
By impregnating it into glass cloth and drying it, the resin content is 45% by weight and the del time at 160℃ is 180℃.
prepreg was obtained. This prepreg was cut into a fixed size of 1 m x 1 spear, and 8 sheets were stacked on top of each other, and copper foil with a thickness of 0.035 a + m was layered on top and bottom, and this was layered with a thickness of 1 m.
．． A laminate plate with double-sided copper cladding was obtained by sandwiching it between 5e+m stainless steel plates and between hot plates of a multistage hydraulic press, heating and pressing at 170° C. for 25 minutes to perform multistage lamination molding. Regarding the laminates of the above Examples and Comparative Examples 1 to 3 (in %, J
Dielectric constant was measured based on IS C6481. In addition, in order to measure dimensional stability, the maximum amount of warp deformation in the diagonal line of each laminate was measured. These results are shown in the table below. As seen in the results in the table, the dielectric constant of Example 3, which used a porous fluororesin sheet as the prepreg base material, was lower than that of Comparative Example 3, which used plus cloth as the base material. It is confirmed that it has excellent high frequency characteristics. *By performing after-curing and rapid cooling, the dimensional stability of the example shown in Example 1 was significantly improved compared to that of Comparative Example 1, which did not perform after-curing. It is confirmed that the dimensional stability can be improved compared to that of Comparative Example 2, which does not. [Effects of the Invention] As described above, in the present invention, a long prepreg prepared using a porous fluororesin sheet as a base material is continuously fed, a required number of prepregs are overlapped, and the prepreg is stacked with a double belt. Since the porous sheet of 77 resin, which is the base material of the prepreg, has a low dielectric constant and excellent high frequency properties, the resin used as the impregnating resin has excellent high frequency properties. Even if you use materials commonly used for laminates, such as epoxy resin, you can create laminates with high high frequency characteristics! ! It is possible to manufacture laminates with high high frequency characteristics using the conventional continuous method that requires long-term molding at high temperatures. Moreover, after curing the laminated molding and cutting it to the specified size, we performed after-curing and rapidly cooled it, so the after-cure compensates for the lack of heat in the resin inside the laminate, and the rapid cooling prevents the crystallization of the resin inside the laminate. It is possible to increase the dimensional stability of the laminate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the apparatus used in the present invention, in which 1 is a prepreg, 2 is a double belt, and A is a laminate.

Claims (1)

[Claims] (1) Continuously feed a long prepreg prepared using a porous fluororesin sheet as a base material, stack the required number of prepregs, and then feed them continuously through a double belt to form a layered sheet to form a predetermined size. A method for manufacturing a laminate, which comprises performing after-curing after cutting and rapidly cooling after the after-curing.