JP2003136554A - Method for manufacturing laminated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated sheet being used for a base sheet for a printed- wiring board and the like and with excellent thickness accuracy with good productivity. SOLUTION: When sheet-like prepregs impregnated with a thermosetting resin are placed between mirror plates and they are heated and pressed between heating platens to mold the laminated sheet, by heating the mirror plates in advance before molding is started, temperature difference between the prepreg at the nearest position to the heating platens and the prepreg at the most separated position to the heating platens is made small to improve accuracy of thickness of the laminated sheet obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminated board used for a printed wiring board substrate and the like, and more particularly to a method for manufacturing a laminated board capable of obtaining a product excellent in thickness accuracy with high productivity. .

[0002]

2. Description of the Related Art Laminates used in printed wiring board substrates are manufactured by impregnating a sheet-shaped base material with a thermosetting resin, and then sandwiching a prepreg that has been cured to the B stage between mirror-finished plates. It is manufactured by heating and pressurizing at.

In the above process, a copper foil is placed on one side or both sides of the prepreg to form a copper clad laminate for a printed wiring board, and a release film or the like is used instead of the copper foil to form an insulating plate.

By the way, in recent years, the operating frequency of electronic parts such as a CPU (central processing unit) has increased with the progress of information processing and information communication equipment, and the matching of the characteristic impedance between the electronic parts and the printed wiring board has been achieved. It has become an important issue. In order to stabilize the matching of the characteristic impedance, it is necessary to provide a laminated plate having excellent thickness accuracy.

[0005]

Conventionally, in the case of producing a laminated plate, if the number of moldings between the hot plates is increased to increase the productivity of the laminated plate per unit time, the thickness accuracy is excellent. It was difficult to get things.

[0006] The reason is that, in order to increase the productivity of the laminated plate per unit time, when a larger number of laminated plates are formed, the prepreg at the position closest to the hot platen and the position farthest from the hot platen rises. The difference in temperature rate becomes larger, and the melt viscosity and gelation time of the resin forming the prepreg greatly differ depending on the position from the heating plate. For this reason, the difference in fluidity of the resin during heating / pressurizing becomes larger,
As a result, there arises a problem that the variation in the thickness of the laminated plate becomes larger.

The variation in the thickness of the laminated plates due to the difference in the temperature rising rate increases as the number of laminated plates to be formed increases.

For this reason, conventionally, methods such as stepwise raising the heating temperature so as not to generate scrapes and voids, and stepwise raising the molding pressure in accordance with the melt viscosity of the prepreg resin have been adopted. However, with such a method, it was not possible to obtain a laminate having good productivity and excellent thickness accuracy.

[0009] Therefore, the present invention has a technical object to obtain a laminate having excellent thickness accuracy with high productivity.

[0010]

In order to solve the above-mentioned problems, according to the present invention, a sheet-like prepreg impregnated with a thermosetting resin is sandwiched between mirror surface plates, and then heated and pressed between hot plates. In the method for producing a laminated plate to be molded, a means of heating the mirror-finished plate in advance before the start of molding is adopted.

Since the prepreg and the mirror surface plate are heated by heat conduction from the hot platen, the temperature increase rate of the prepreg closest to the hot platen is high, and the temperature increase rate of the prepreg farthest from the hot platen is high. Become slow. Therefore, the melt viscosity of the prepreg closest to the hot platen is higher than that of the prepreg far from the hot platen, because the temperature starts to rise in a short time after heating and pressurization, so the prepreg resin is hardened. Before the melt viscosity increases due to the reaction, the melt viscosity decreases due to the temperature increase of the prepreg. That is, the melt viscosity of the prepreg near the hot platen tends to be lower than that of the prepreg away from the hot platen. Therefore, if appropriate heating / pressurizing conditions are set for the prepreg closest to the hot platen, the melt viscosity of the prepreg farthest from the hot platen will be higher than the appropriate melt viscosity. The fluidity of the resin under pressure decreases, and scratches and voids occur. On the other hand, in contrast to the above, when appropriate heating and pressurizing conditions are set for the prepreg at the position farthest from the hot platen, the melt viscosity of the prepreg closest to the hot platen becomes too low and the prepreg resin There is a drawback that the fluidity becomes large and the thickness accuracy of the laminated plate is poor.

The present invention solves this technical problem by heating the mirror surface plate to a predetermined temperature in advance before the start of molding, as described above. That is, if the mirror surface plate is preheated to a predetermined temperature before the start of molding, the temperature of the prepreg increases due to heat conduction from the mirror surface plate, and as a result, the prepreg closest to the hot plate and the hot plate have the highest temperature. It is possible to reduce the temperature difference between the prepregs at distant positions, and as a result, it is possible to produce a laminated plate having excellent thickness accuracy.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a sheet-like prepreg impregnated with a thermosetting resin is used as a matte, non-woven fabric, or woven fabric base material of inorganic or organic fiber such as glass fiber, paper, aramid, or polyester. , Epoxy resin, phenol resin, melamine resin, unsaturated polyester resin, polyimide resin, etc.
What was hardened to the stage can be used. The material of the mirror surface plate is not particularly limited to metals such as stainless steel, aluminum and iron, and fiber reinforced plastics, but materials having a large thermal conductivity can efficiently conduct heat from the hot platen. The present invention is advantageous in terms of thickness accuracy. Usually, stainless steel, which has high hardness, is hard to be scratched, and has excellent durability, can be used. The thickness of the mirror surface plate is not particularly limited, but since the prepreg is sandwiched by using a preheated mirror surface plate, during the step after sandwiching, that is, in general, press molding is a multi-stage press in which multiple hot plates are simultaneously molded. Therefore, it is necessary to use a thick mirror surface plate in order to prevent the temperature drop due to heat dissipation, because the process time of other steps is required.
It is preferable to obtain a laminated plate having excellent thickness accuracy, and one having a thickness of about 1 to 10 mm is usually used. In this way, the material and thickness of the mirror plate can be appropriately selected.

The method of heating the mirror surface plate can be performed by using hot water, steam, an infrared heater or the like, and is not particularly limited, but usually, in the previous step of sandwiching the sheet prepreg between the mirror surface plates, Is washed with water in order to remove minute foreign matters attached to the surface of the mirror plate, it is possible to heat the mirror plate by raising the temperature of this water. The temperature for heating the mirror surface plate is not particularly limited, but closer to the molding temperature (usually 130 to 180 ° C.) is more effective in improving the thickness accuracy of the laminated plate, but after the prepreg is sandwiched between the mirror surface plates, heating If it takes a long time to pressurize, the temperature for heating the mirror surface plate should be appropriately selected in consideration of the effect of the curing reaction of the prepreg during this time. Usually, the heating temperature of the mirror plate is 50 to 80 ° C. The heating temperature of the mirror surface plate is usually set to a temperature equal to or lower than the softening point of the prepreg resin in order to suppress the wrinkling of the copper foil.

[0015]

[Examples and Comparative Examples] [Example 1] Bisphenol A
A glass woven fabric (210 g / m ² ) was prepared by mixing 2 parts by weight of dicyandiamide as a curing agent and 1 part by weight of imidazole as a curing accelerator with 100 parts by weight of a type epoxy resin and having a solid content of 50% by weight. Impregnated and prepreg A having a resin adhesion amount of 42% was prepared. Eight prepregs A were superposed, 18 μm thick copper foil was superposed on both sides, and this composition was superposed alternately with a 2 mm-thick stainless specular plate heated to 50 ° C., and 20 sets were pressed. Inserted between the plates, hot plate temperature 160 ℃, molding pressure 4.9M
It was heated and pressure molded at Pa for 120 minutes. The thickness of all the 20 laminated plates obtained was measured at positions including the central portion and the peripheral portion. The results are shown in Table 1.

[Example 2] A laminated plate was obtained in the same manner as in Example 1 except that the temperature of the stainless specular plate was changed to 80 ° C, and the thickness was measured in the same manner as in Example 1. .
The results are shown in Table 1.

Comparative Example 1 The temperature of the mirror plate was set to 20 ° C. (room temperature), the number of laminated plates was set to 10, and the heating plate temperature was held at 140 ° C. for 60 minutes and then at 160 ° C. for 80 minutes. . Further, the pressure condition was maintained at 3.3 MPa for 30 minutes, and then the laminated plate was molded and pressed in the same manner as in Example 1 except that the pressure was 4.9 MPa, and the thickness was measured in the same manner as in Example 1. The results are shown in Table 1. In Comparative Example 1, as a result of various examinations on the setting conditions of the hot platen temperature and the pressure conditions, the described conditions of Comparative Example 1 show that, when the specular plate is not heated, no scratches and voids are generated and the thickness accuracy is improved. It was confirmed that the best laminated plate could be obtained.

[Comparative Example 2] A laminated plate was molded in the same manner as in Example 1 except that the temperature of the mirror plate was set to 20 ° C (room temperature).
Pressurization was performed and the thickness was measured as in Example 1. The results are shown in Table 1. As for the thickness accuracy of the obtained laminated plate, the difference between the maximum value and the minimum value of the measured thickness values was the thickness accuracy in both the examples and the comparative examples.

[0019]

[Table 1]

From the results shown in Table 1, when the hot platen temperature setting conditions and pressure conditions in the pressing step are the same, by heating the mirror-finished plate in advance before the start of molding, the laminated plate having excellent thickness accuracy can be obtained. It was confirmed that you can get.

[0021]

As described above, according to the present invention, a laminate having excellent thickness accuracy can be obtained with high productivity.

Claims (4)

[Claims] 1. A method for manufacturing a laminated plate, comprising: sandwiching a sheet-like prepreg impregnated with a thermosetting resin between a pair of mirror surface plates to heat and press between hot plates to form a laminated plate; A method for producing a laminated plate, which comprises heating the face plate in advance. 2. The method for producing a laminated plate according to claim 1, wherein the heating temperature of the mirror plate is 50 to 80 ° C. 3. The laminate according to claim 1, wherein the mirror surface plate is heated by raising the temperature of water in the mirror surface plate washing step of the previous step of sandwiching the sheet-like prepreg between a pair of mirror surface plates. Method of manufacturing a plate. 4. The method for producing a laminated plate according to claim 1, wherein a stainless plate having a thickness of 1 to 10 mm is used as the mirror plate.