JP2001334542A - Method for manufacturing laminated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated sheet having stable quality (sheet thickness accuracy, elimination of molding voids or the like) and reduced in use energy at a low cost by continuous molding. SOLUTION: In a method for manufacturing the laminated sheet by vertically moving one or a plurality of prepregs each formed by bonding a resin to a sheetlike fiber base material from above to below and superposing a metal foil or film on the single surface or both surfaces of the layer comprising the prepregs and preheating the whole to insert the same in the gap between heating rolls to which cushioning properties are imparted from above to perform the laminate molding thereof, each of the heating rolls to which cushioning properties are imparted is a metal roll having a layer of a material having rubbery elasticity formed on the outer periphery thereof and the material having rubbery elasticity has a rubber Shore hardness of 50-100 and the thickness thereof is preferably 0.5-3.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminated board, and more particularly to a method for continuously producing a laminated board suitable for a printed circuit board used for electric equipment, electronic equipment, communication equipment and the like.

[0002]

2. Description of the Related Art As for printed circuit boards, demands for miniaturization and high functionality are becoming stronger, but price competition is fierce. In particular, a glass cloth base epoxy resin laminate used for printed circuit boards or a glass non-woven fabric is used as an intermediate layer. As for the laminates using glass woven fabric as the surface layer substrate as the base material, reduction of the price is a major issue in any case. In recent years, digitalization has progressed in electrical equipment, electronic equipment, communication equipment, and the like, and a stable impedance on a printed circuit board has been required, and accordingly, a copper-clad laminate, which is a raw material of a printed circuit board, has been required. Sheet thickness accuracy has been required.

In the case of laminating and forming a laminate used for a printed circuit board as described above, a multi-stage batch in which a number of copper foils, prepregs, mirror plates and the like are stacked between hot plates and heated and pressed. Presses are common. However, in such a multi-stage press, since the heat history applied to each laminate during lamination molding differs depending on the position of each laminate in the hot plate, there is a difference in quality such as moldability, warpage, and dimensional change rate. It was difficult to supply products with low quality variation. Furthermore, since the laminated plate is formed at a high pressure of ^{20 to} 100 kg / cm ² , there is a problem that the thickness accuracy is insufficient due to the flow of the resin. In addition, a multi-stage press requires an enormous amount of heat to heat and cool a jig required for forming a laminated plate such as a hot plate, a mirror surface plate, and a cushioning material. The facility is difficult to handle.

Conventionally, horizontal continuous belt presses and the like have been developed as laminates having little quality variation and energy saving equipment. However, pressure unevenness and temperature unevenness when sandwiched between belts or problems due to gravity. Due to the difference in the vertical direction and the angle of entry of the material, there is a difference between the front and back due to the moldability (especially the occurrence of voids) and the adhesive strength of the copper foil. There was a big problem.

[0005]

As described above, in the conventional multi-stage press machine, there is a large variation in the quality such as formability, warpage, dimensional change, and plate thickness due to simultaneous heating of a large number of sheets. There is a problem that an enormous amount of heat is required to heat and cool a device necessary for molding the slab. In addition, in the conventional horizontal continuous press, due to pressure differences due to gravity, temperature variations, tension variations in the material, etc., molding defects (voids), reduced copper foil adhesion, reduced dimensional stability, warpage, etc. There was a problem. The present invention solves the problems of the conventional laminate molding method, eliminates the internal residual stress in the laminate molding, improves the dimensional stability of the laminate, further improves the formability without voids, and achieves energy saving. An object of the present invention is to provide an inexpensive method for manufacturing a laminate.

[0006]

SUMMARY OF THE INVENTION According to the present invention, one or more prepregs in which a resin is adhered to a sheet-like fiber base material are vertically moved from top to bottom, and a metal foil or The present invention relates to a method for producing a laminated plate, comprising laminating and preheating a film, inserting the film between heating rolls having cushioning properties from above, and laminating. Further, the roll imparting cushioning property is preferably a metal roll in which a layer of a material having rubber-like elasticity is formed on the outer periphery, and the material having rubber-like elasticity has a rubber shore hardness of 50 to 100 degrees. The thickness is preferably 0.5 to 3.5 mm.

In the present invention, the sheet-like fiber base material includes glass fiber base materials such as glass cloth, glass non-woven cloth and glass paper, as well as woven and non-woven fabrics made of paper, synthetic fibers, etc., metal fibers and carbon fibers. And woven fabrics, nonwoven fabrics, mats and the like made of mineral fibers, etc., and these base materials may be used alone or in combination.

[0008] The resin adhered to the sheet-like fiber base material for producing the prepreg is generally a thermosetting resin, such as an epoxy resin, a polyimide resin, a phenol resin, a melamine resin or a modification thereof. A resin is preferably used, but other resins such as a thermoplastic resin and a natural resin are also used, but are not limited thereto. The form of the resin when the resin is adhered to the base material is usually a varnish dissolved in a liquid, particularly a solvent, but may be a powdery resin or a state in which a solid resin is heated and melted. In the case of a thermosetting resin, a curing agent and a curing accelerator are added as necessary.

Further, a filler, a coloring agent, and a reinforcing material can be compounded in the resin. When an inorganic filler is added as the filler, characteristics such as tracking resistance, heat resistance, and a decrease in coefficient of thermal expansion can be imparted. Such inorganic fillers include aluminum hydroxide, magnesium hydroxide, calcium carbonate, talc, wollastonite, alumina, silica, unfired clay, fired clay, barium sulfate and the like.

Next, the obtained resin is uniformly applied on a sheet-like fiber base material. The amount of the resin adhered at this time varies depending on the fiber material, properties, and weight (per unit area) of the sheet-like fiber base material, but is usually 40 to 40% of the weight of the sheet-like fiber base material.
It is about 60%. However, in the case of adhering to both surfaces of the base material, it is preferable that approximately half the amount of the adhering amount be adhered to one surface. The method for adhering the resin to the sheet-like fiber substrate is not particularly limited, as long as the resin adheres well, such as a method of dipping the substrate in a resin varnish, an application method using various coaters, or a spraying method using a spray. Further, especially when the resin is solvent-free, the sheet-like fiber base material may be pre-heated. In this case, when the resin is applied to the sheet-like fiber base material, the base material is horizontal. May also be vertical. Therefore, it can be attached to the upper or lower surface of the sheet-like fiber substrate or the vertical surface by coating. The prepreg is obtained by the subsequent heating.

The prepreg obtained as described above is usually wound once by a winder or the like and then unwound or, as it is, one or a plurality of prepregs are moved vertically from above to below. A metal foil or a film such as a copper foil is laminated on one or both sides. Next, after these are preheated, the laminate is formed into a laminate by inserting from above into between the heating rolls provided with cushioning properties. In the roll forming of the present invention, it is possible to use a cut prepreg, but it is preferable to form continuously. In this case, the molding is performed through one or a plurality of pairs of rolls.

The present invention is characterized in that a roll provided with cushioning properties is used as a heating roll for forming a laminate. As a method of imparting cushioning properties to the roll, preferably, a material having rubber-like elasticity (hereinafter, referred to as an elastic material) is formed as a surface layer on the outer periphery of the metal roll to a predetermined thickness. The elastic material usually has a rubber Shore hardness of 50 to 100 degrees, preferably 70 to 90 degrees. The thickness is adjusted to 0.5 to 3.5 mm. The resilient material is formed on both pairs of rolls. If the rubber shore hardness of the elastic material is less than 50 degrees, it is too soft and deforms during molding, causing a variation in the thickness of the laminate,
If it exceeds 100 degrees, it is hard and cannot provide sufficient cushioning properties. Within the range of 70 to 90 degrees, the generation of voids during molding is effectively suppressed, and the thickness accuracy of the laminated plate is also improved. As such an elastic material, various rubber elastic bodies can be specifically used, but silicone rubber is preferable in terms of heat resistance. If the thickness of the elastic material is less than 0.5 mm, sufficient cushioning properties cannot be imparted,
If it exceeds 3.5 mm, deformation occurs during molding, which causes a variation in the thickness of the laminate.

In the present invention, by giving a cushioning property to the roll by a method of forming a layer of an elastic material on the outer periphery of the roll, the generation of voids during molding can be suppressed,
The reason why the accuracy of the thickness of the laminated plate is improved is as follows. That is, the increase in pressure applied to the prepreg during molding is relatively slow due to the elastic material, and voids in the prepreg can escape, and the entrapment decreases,
Then, it is considered that the pressure on the prepreg becomes more uniform due to the cushioning property, the thickness of the prepreg based on the base material is maintained, and the thickness accuracy of the laminated plate is improved.
For the temperature of the heating roll, the applicable range is 100
280 ° C., for example, 110 for epoxy resin
-180 ° C, and preferably 150-240 ° C for polyimide resin.

Further, in the present invention, before laminating between the heating rolls provided with cushioning properties, the prepreg is laminated with a metal foil or film and then preheated to carry out subsequent heating rolls provided with cushioning properties. Insufficient amount of heat from the heating roll at the time of forming by molding can be compensated, and defective forming (particularly, void) can be further prevented. Since the melting of the resin reaches the minimum melt viscosity at that temperature in about 30 seconds to 60 seconds after the start of heating, contact with the heating roll alone tends to cause an insufficient melting state. Therefore, by preheating the prepreg, roll forming can be performed in a stable state. Here, it is preferable that the preheating temperature is higher by 20 to 50 ° C. than the roll temperature. 2
If the temperature is lower than 0 ° C., the molten state of the resin becomes insufficient, which may cause molding failure.
Since the viscosity increases due to the reaction of the resin, molding failure tends to occur. The temperature of the preheating is, for example, usually about 130 to 180 ° C. for an epoxy resin and usually about 170 to 240 ° C. for a polyimide resin.

Hereinafter, the method for producing a laminate of the present invention will be described.
A typical example of the laminating process will be described for each process sequentially with reference to the drawings. (Supply of prepreg) The prepreg 2 is unwound from the prepreg supply unit 1 and supplied to the heating roll while being transferred from above to below. (Metal foil supply) The metal foil 4 is unwound from the metal foil supply unit 3 and supplied to both sides (or one side) of the prepreg. (Preheating) The metal foil 4 is superimposed on the prepreg 2 and preheated by a preheater 8 such as a far infrared heater. (Forming by Heating Roll) Laminate forming is performed by passing between one or more pairs of heating rolls 5 provided with cushioning properties from above. (Cutting or Winding) The formed laminated plate is cut to a required length by a cutting machine 6 or wound around a winding machine 7. (Aftercure) Next, aftercure is performed in a heating and drying oven at 200 to 280 ° C.

[0016]

The present invention will be described below with reference to examples and comparative examples.

Example 1 100 parts by weight of an epoxy resin (brominated epoxy resin Ep5048 manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: 675), 5 parts by weight of a curing agent (dicyandiamide), and a curing accelerator (2-ethyl- 1 part by weight of 4-methylimidazole) and 100 parts by weight of methylcellosolve were mixed to obtain a varnish. 100 g /
m ² glass cloth is immersed and the resin content is 100
After impregnation so that g / m ^{2 was} adhered, the resultant was dried with a dryer at 170 ° C. for 3 minutes, and the obtained prepreg was wound around a winder.

A pair of rolls having a heat-resistant silicone rubber layer having a rubber shore hardness of 80 to 85 degrees and a thickness of 2 mm on the surface were used as the rolls provided with cushioning properties.
The above-mentioned prepreg was vertically transferred from above to below as shown in FIG. 1 and copper foil having a thickness of 18 μm was supplied to both sides thereof.
Preheated to ° C. Subsequently, heat and pressure molding was performed by passing the space between the rolls (gap: 0.1 mm) heated to 140 ° C. from above. Thereafter, after-curing was performed at 180 ° C. for 60 minutes to produce a double-sided copper-clad laminate having a thickness of 0.1 mm.

(Comparative Example 1) A prepreg prepared and wound in the same manner as in Example 1 was transported almost vertically downward from above as shown in FIG. 1 and copper foil having a thickness of 18 μm was supplied to both sides thereof. And a pair of metal rolls (gap of 0.1 mm) heated to 150 ° C., and heated and pressed by passing from above. Thereafter, after-curing was performed at 180 ° C. for 60 minutes to produce a double-sided copper-clad laminate having a thickness of 0.1 mm.

(Comparative Example 2) A prepreg produced and wound in the same manner as in Example 1 was cut into a predetermined length, and copper foil having a thickness of 18 µm was superposed on the upper and lower surfaces thereof and placed between mirror plates. , 10 sets of these were stacked, and the temperature was 165 ° C and the pressure was 8k.
g / cm ² for 90 minutes under pressure
Was prepared.

With respect to each of the copper-clad laminates obtained as described above, evaluation of formability (observation of voids), variations in thickness and various properties were measured. Table 1 shows the results.

[Table 1]

(Measurement method) Formability: The copper foil was removed by etching, and voids on the surface and voids between strands were visually observed. 2. Laminate thickness: Cut out to a size of 500 × 600 mm, the thickness was measured at 42 locations with a micrometer, and the average value, standard deviation, and the difference (R) between the maximum value and the minimum value were determined. 3. Moisture-absorbing solder heat resistance: 50 × 50 mm test pieces (three test pieces each) are subjected to (1) boiling water treatment for 2 hours and (2) 121 ° C. pressure cooker treatment for 1 hour, and then to 260 ° C. solder. It was immersed in a bath for 30 seconds and observed for blisters. ○: When all three have no blister,
X: When blisters occur in 1 to 3 pieces. Copper foil peel strength: Measured according to JIS C6481. 5. Insulation resistance: Measured according to JIS C6481. The test piece was previously subjected to a moisture absorption treatment (96 ° C., 20 ° C., 65% humidity).

According to the results shown in Table 1, the copper-clad laminate obtained in Example 1 has almost no voids and has good moldability.
It can be seen that the thickness accuracy is also excellent. Other characteristics of the laminate are also equal to or higher than those of the conventional multi-stage press system.

[0024]

According to the method of the present invention, a metal foil or a film is overlapped while a prepreg is moved in a vertical direction, and a preheating step is carried out. It is characterized by being laminated and formed. Therefore, the molding equipment is reduced in size, and the fuel used is thereby reduced, so that it is possible to achieve a reduction in energy costs, a reduction in air pollution due to exhaust gas from the heat source equipment, and resource saving. Also,
During the production of laminates, the prepreg is moved vertically, so there is no effect of gravity compared to conventional continuous molding by lateral movement, so the tension of the prepreg becomes uniform and the warpage of the laminate is extremely reduced. Since the pre-heating is performed after the prepreg and the metal foil are superimposed and then formed by the heating roll for imparting cushioning property, it is possible to eliminate voids and achieve extremely stable thickness accuracy and obtain a high-quality laminated board. Can be. Further, since the laminated plate can be cut to an arbitrary length by roll forming, a portion of the end material such as an ear which has conventionally occurred is reduced, and the yield is improved. Thus, it is excellent in terms of cost reduction of raw materials, equipment, and processes, and is suitable as an industrial method for manufacturing a laminated board.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a manufacturing process of a laminate according to the present invention.

[Description of Signs] 1 Pre-preg supply unit 2 Pre-preg 3 Metal foil supply unit 4 Metal foil 5 Heating roll 6 Cutting machine 7 Winding machine 8 Preheating machine

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Claims (3)

[Claims] 1. One or more prepregs having a resin adhered to a sheet-like fiber base material are vertically moved from above to below, and a metal foil or film is overlapped on one or both sides thereof and preheated, A method for producing a laminated plate, comprising inserting a heating roll provided with cushioning properties from above and laminating the same. 2. The method for producing a laminate according to claim 1, wherein the roll provided with cushioning properties is a metal roll having a layer of a material having rubber-like elasticity formed on the outer periphery. 3. A material having rubber-like elasticity has a rubber shore hardness of 50 to 100 degrees and a thickness of 0.5 to 3.5.
3. The method for producing a laminate according to claim 2, wherein