JPH0548178B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing a printed wiring board using mica as a base material. [Prior Art] A printed wiring board is produced by using a laminate with excellent electrical insulation performance as an insulating substrate and laminating metal foil on the surface thereof. The insulating substrate made from this laminate is made by stacking multiple sheets of prepreg made by impregnating a base material such as paper with thermosetting resin varnish and drying it, and then applying heat and pressure to the prepreg. Manufactured by laminated molding. Here, the electrical insulation performance of the insulating substrate is greatly influenced by the resin impregnated into the base material, and is also greatly influenced by the base material itself. Therefore, in addition to conventionally using paper as a base material, glass cloth made of woven or non-woven glass fibers is also used as a base material for insulating boards for printed wiring boards that require particularly high electrical insulation performance. is being carried out. However, in recent years, printed wiring boards have come to be required to have even higher electrical insulation performance due to the high-density packaging of electronic components. The use of mica or mica as a base material has attracted attention. Such mica is provided in the form of small scale-like flakes, and when mica is used as a base material, mica paper is produced by making a slurry in which mica scales are dispersed and aggregating the mica scales. It is conceivable to create a mica paper and use this mica paper as a base material. [Problems to be Solved by the Invention] At present, when preparing a prepreg by impregnating a base material with a thermosetting resin varnish or the like and drying it, currently a long base material is continuously The base material is impregnated with the thermosetting resin varnish by passing it through the thermosetting resin varnish and immersing it in the thermosetting resin varnish while feeding it, and then passing it through a dryer while continuously feeding it and heating it. A common manufacturing method is to dry the thermosetting resin varnish using a drying process, and then cut it into regular lengths.This continuous process increases the productivity of prepreg. We have reached the point where we can improve our performance. However, when using mica paper as a base material, when impregnating the mica paper with thermosetting resin varnish, etc., if the mica paper is immersed in the thermosetting resin varnish, the thermosetting resin will be absorbed into the mica paper. As the resin varnish penetrates, the aggregated mica scales are separated,
This will result in the mica paper not being able to maintain its paper-like form, and tension will be applied to the mica paper while it is immersed in thermosetting resin varnish and sent continuously to the dryer. The mica paper, whose mica scales have been separated by the penetration of the curable resin varnish, cannot withstand this tension and breaks. Therefore, when mica paper is used as a base material, a long mica paper is continuously fed and dipped in thermosetting resin varnish, and then a mica paper impregnated with thermosetting resin varnish is continuously fed. For example, it is not possible to adopt a construction method in which the mica paper is cut into regular lengths and then passed through a dryer. Prepregs have to be made by hand rather than in a continuous process, which involves impregnating them with a resin varnish and then drying the mica paper impregnated with this thermosetting resin varnish one sheet at a time, making it very difficult to produce. This means that they have no choice but to rely on low quality work. [Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and the method for manufacturing a printed wiring board according to the present invention includes slurry in which mica scales are dispersed. By filtering the paper onto the surface of a net and transferring it to the surface of a reinforcing sheet into which the resin liquid is permeated, a mica sheet is created in which mica paper made of mica scales and a reinforcing sheet are laminated. A mica sheet base material prepreg is created by impregnating this mica sheet with a thermosetting resin liquid and drying it, and by stacking a plurality of these mica sheet base material prepregs, the outermost layer of the mica sheet base material prepreg is Layer metal foil on the surface,
This product is characterized by being molded under heat and pressure. In the printed wiring board of the present invention, mica paper in which mica scales are assembled serves as a base material and can form an insulating board,
Due to the excellent electrical insulation properties of mica, it is possible to provide a printed wiring board with good electrical properties, and in the method for manufacturing a printed wiring board of the present invention, a thermosetting resin varnish is applied to mica paper. Even in the impregnated state, mica paper can maintain its shape and tension as paper due to the reinforcing effect of the reinforcing sheet, and when using mica paper as a base material for insulating substrates of printed wiring boards, it is necessary to carry out continuous processes. It is possible to create a prepreg by impregnating a thermosetting resin liquid and drying it. The present invention will be explained in detail below. As mica (mica), either natural mica or synthetic mica can be used, and the types and chemical compositions of mica are shown in Table 1, although they are not particularly limited. These materials can be used alone or in combination.

【table】

[Table] This mica is used in the form of pulverized scales, and the particles are preferably adjusted to 50 meshes or less, preferably 100 meshes or less. If the particle size exceeds 50 meshes, the surface of the mica paper produced by aggregating mica scales may become rough. Mica paper can be made by assembling mica scales without using an adhesive, but in the present invention, a reinforcing sheet is laminated on the surface of this mica paper, and the mica paper is used as a reinforcing sheet. It is used as a reinforced mica sheet. The reinforcing sheet should be a fibrous material that has the ability to penetrate the resin liquid so as not to impede the impregnation of the thermosetting resin liquid into the mica paper when the mica sheet is used as a base material for an electrical insulating board. For example, glass cloth made of paper or glass fiber woven cloth or non-woven cloth, cloth made of other natural fibers or synthetic fibers, asbestos cloth, etc. can be used. Furthermore, when reinforcing the mica paper 1 with the reinforcing sheet 2 to create the mica sheet 3, in addition to laminating the reinforcing sheet 2 on one side of the mica paper 1 as shown in FIG. The reinforcing sheet 2 may be laminated on both sides of the mica paper 1 as shown in Figure b, or it may be reinforced by sandwiching the reinforcing sheet 2 between the surfaces of two mica papers 1 and 1 as shown in Figure 2 c. The sheets 2 may be stacked. Furthermore, multiple sheets of mica paper 1
It is also possible to create a multilayered mica sheet 3 by alternately laminating a plurality of reinforcing sheets 2 and mica paper 1, and in short, the combination of mica paper 1 and reinforcing sheet 2 is not limited in any way and is arbitrary. The reinforcing sheet 2 may be of any thickness as long as it has sufficient thickness to reinforce the mica paper 1. Here, when creating the mica sheet 3 by laminating the mica paper 1 and the reinforcing sheet 2,
It is preferable to laminate the mica paper 1 and the reinforcing sheet 2 without using an adhesive. That is, if the mica paper 1 and reinforcing sheet 2 are bonded and laminated using an adhesive, the insulation performance of the electrical insulating board may be affected by the type of adhesive. Therefore, in manufacturing the mica sheet 3, by making an aqueous slurry of mica scales, the mica paper 1 is assembled by assembling the mica scales, and at the same time, it is laminated with the reinforcing sheet 2, thereby eliminating the need for adhesive. It is recommended that the layers be laminated in a uniform manner. FIG. 3 shows an example of a papermaking apparatus. A slurry 15 in which paper pulp or fiber material such as glass fiber is dispersed in water is supplied to a vat 10, and this slurry 15 is filtered on the surface of a circular screen 11. The fibrous material remains on the surface of the circular screen 11 during papermaking, and the fibrous material layer 16 is transferred onto the surface of the endless strip-shaped felt 12. Further, a slurry 17 in which mica scales are dispersed in water is supplied to the vat 13, and this slurry 17 is filtered on the surface of the round screen 14, and the mica scales remain on the surface of the round screen 14 to form paper. The paper-made layer 18 is a paper-made layer 1 of fibrous material attached to the surface of the felt 12.
transferred to the surface of 6. In this way, as shown in FIG. 4, a paper sheet 19 in which a paper layer 16 of fiber material and a paper layer 18 of mica scales are laminated is attached to the surface of the felt 12, and the paper sheet 19 is fed as the felt 12 runs. , and papermaking sheet 1
9 is peeled from the felt 12, dehydrated by pressing with a roll or the like, further dried with a drier or the like, and then rolled up to form the mica paper 1 and fibers in which the paper-formed layer 18 of mica scales has been dried. It is possible to obtain the mica sheet 3 in which the paper-formed layer 16 of the material is laminated with the dried reinforcing sheet 2. In this way, since the mica paper 1 and the reinforcing sheet 2 are laminated during papermaking, the mica paper 1 and the reinforcing sheet 2 can be laminated and integrated without using an adhesive.
This means that it will be possible to manufacture
The apparatus shown in FIG. 3 can produce the mica sheet 3 shown in FIG. By using a pair of vats 13 for supplying a slurry 17 of mica scales, the mica sheet 3 shown in FIG. 2c can be manufactured. In addition, in the apparatus shown in FIG. 3, the mica paper 1 and the reinforcing sheet 2 are laminated at the time of papermaking, but in the apparatus shown in FIG. At the same time, a long reinforcing sheet 2 is supplied, and a circular net 14 is placed in a vat 13 to which a slurry 17 of mica scales is supplied.
By forming a paper layer 18 of mica scales and transferring the paper layer 18 of mica scales onto the surface of the reinforcing sheet 2, and thus laminating the paper layer 18 of mica scales on the surface of the reinforcing sheet 2, The laminated sheet 20 prepared as shown in Figure 6 is dehydrated by pressing with a roll or the like, further dried with a drier or the like, and then wound up, thereby drying the paper-formed layer 18 of mica scales. It is possible to obtain a mica sheet 3 in which a mica paper 1 and a reinforcing sheet 2 are laminated. Even in this case, since the mica paper 1 and the reinforcing sheet 2 are laminated during papermaking, the mica paper 1 and the reinforcing sheet 2 are laminated and integrated without using an adhesive. This means that it will be possible to manufacture In the device shown in Figure 5, the second
The mica sheet 3 shown in FIG. Then, the mica sheet 3 shown in Fig. 2b was added to the felt 1.
2, a reinforcing sheet 2 is laminated on the surface of the reinforcing sheet 2, and a paper layer 18 of mica scales is further attached to the surface of the reinforcing sheet 2. By laminating them, the mica sheets 3 shown in FIG. 2c can be obtained. Although FIGS. 3 and 5 show a circular wire-type papermaking apparatus, by changing the batts 10 and 13 to special homers and the circular wires 11 and 14 to Fourdrinier, the Fourdrinier-type papermaking apparatus can be modified. You can also use When manufacturing a printed wiring board using the mica sheet 3 manufactured by laminating the mica paper 1 and the reinforcing sheet 2 as described above as a base material, the prepreg 5 is first formed using the mica sheet 3. create. FIG. 7 shows an example of an apparatus for producing prepreg 5. First, while continuously feeding out a long mica sheet 3, a thermosetting resin liquid 4 is
The thermosetting resin liquid 4 is impregnated into the mica sheet 3 by passing it through and immersing it in the mica sheet 3. Here, as the thermosetting resin liquid 4, epoxy resin, phenol resin,
Any thermosetting resin varnish, such as urea resin, melamine resin, unsaturated polyester resin, polyimide resin, bismaleimide/triazine resin, or phenol/aralkyl resin, can be used alone or in combination of two or more. Then, when the mica sheet 3 is immersed in the thermosetting resin liquid 4,
The thermosetting resin liquid 4 is directly poured into the mica paper 1.
Alternatively, the mica paper 1 is penetrated and impregnated through the reinforcing sheet 2 formed to be liquid-permeable. Although the agglomeration force of the mica scales is weakened, the mica paper 1 has an increased aggregation force of the mica scales due to the lamination of the reinforcing sheet 2, and the mica paper 1 is strengthened by the penetration of the thermosetting resin liquid 4. There is no fear that the paper form will not be retained. The mica sheet 3 impregnated with the thermosetting resin liquid 4 in this manner is continuously fed and introduced into a dryer 21 such as an oven. The mica sheet 3 impregnated with the thermosetting resin liquid 4 is dried in a dryer 21.
Tension is applied to the mica sheet 3 when the mica sheet 3 is sent to the paper, but the mica paper 1 whose agglomeration force of the mica scales is weakened by being impregnated with the thermosetting resin liquid 4 is as described above. It is reinforced by the reinforcing sheet 2, and this tension can be received by the reinforcing sheet 2, so that it is possible to prevent the mica paper 1 from tearing and causing damage to the mica sheet 3. Then, the mica sheet 3 is heated by passing it through the dryer 21, and the thermosetting resin impregnated in the mica sheet 3 is dried and semi-cured, thereby obtaining the prepreg 5 using the mica sheet 3 as a base material. can. This prepreg 5 is further cut into predetermined dimensions by a cutting device 22. Next, a prepreg 5 having the mica sheet 3 formed to a predetermined size as a base material is prepared as shown in FIG. 1a.
By stacking the required number of prepreg sheets as shown in FIG. Then, the resin in the prepreg 5 melts and hardens, and a plurality of mica sheets 3 are laminated and bonded to obtain a laminate as an integrated insulating substrate 7, and the melted and hardened resin in the prepreg 5 becomes an adhesive. A printed wiring board A in which a metal foil 6 is laminated on the surface of an insulating substrate 7 can be obtained as shown in FIG. 1b. By overlaying metal foils 6, 6 on both outermost layers of prepreg 5, a double-sided metal foil clad printed wiring board A can be obtained, and by overlaying metal foil 6 on the outermost layer of one side of prepreg 5. Therefore, a printed wiring board A having one side covered with metal foil can be obtained. Here, several examples of combinations of the mica paper 1 and the reinforcing sheet 2 in the mica sheet 3 are shown below.
As shown in Figures a, b, and c, Figure 1a is the second
Prepreg 5 based on mica sheet 3 in figure a
A plurality of sheets are laminated using a chisel. In addition, as shown in FIG. 8a, it is possible to laminate a plurality of prepregs using only the mica sheet 3 of FIG. 2b as a base material, and as shown in FIG. It is also possible to laminate a plurality of prepregs 5 using only the mica sheet 3 as a base material. Furthermore, in addition to using only the prepregs 5 of the same type of mica sheet 3 as shown above, prepregs 5 of different types of mica sheets 3 can also be used in combination. 9a shows the use of the prepregs 5 of the mica sheets 3 of FIGS. 2a and 2b in combination, and FIG. 9b shows the use of the prepregs 5 of the mica sheets 3 of FIGS. 2a and 2c. FIG. 9c shows that the prepregs 5 of the respective mica sheets 3 are used in combination, and FIG. 9c shows that the prepregs 5 of the respective mica sheets 3 of FIGS. 2b and 2c are used in combination. Furthermore, as shown in FIG. 9d, the prepregs 5 of the mica sheets 3 of a, b, and c of FIG. 2 can be used in combination, respectively. In the combination shown in FIG. 9, the prepregs 5 of different types of mica sheets 3 can be laminated alternately or randomly, or in any desired manner. Since the printed wiring boards A formed as described above are formed using the mica sheet 3 as a base material, they can have high electrical insulation properties. Furthermore, mica has a scale plate-like form, and in the mica paper 1 in the mica sheet 3, this mica is in a layered state, so that the mica paper 1 becomes in-plane isotropic and molded. There is no warping or twisting afterward, and it has excellent dimensional stability.
It is possible to reduce warping and twisting in the printed wiring board A, and improve dimensional stability. In addition, mica has low hardness,
Post-processing of the printed wiring board A becomes easier, and for example, heat generation during drilling of through-holes can be suppressed to a small level, the occurrence of smear can be reduced, and the reliability of through-holes can be improved. It is. [Example] Next, the present invention will be specifically explained using Examples. Examples 1 to 6 Manufacture of mica sheets A slurry 15 containing 25 kg of kraft pulp in 1,000 ml of water was supplied to the vat 10 of the apparatus shown in Fig. 3, and mica scales (muscovite, particle size of 200 mesh Particle size is below 10~150μ)
2 kg of slurry 17 is supplied to the vat 13 of the apparatus shown in FIG. 3, and paper layers 16 and 18 made from each slurry 15 and 17 are deposited on the surface of the felt 12 in a laminated state as shown in FIG. A paper sheet 19 on which the paper layers 16 and 18 are laminated
By drying it using a dryer at 100℃,
Fig. 2a shows the mica paper 1 having the weight shown in Table 2 and the paper as the reinforcing sheet 2 being laminated and integrated;
Mica sheets 3 having layer configurations b and c were obtained (mica sheets No. 1, No. 2, and No. 3). Further, in the apparatus shown in FIG. 5, a glass paper made of glass fibers is supplied as a long reinforcing sheet 2 along the surface of the felt 12, and a slurry 17 of mica scales similar to that described above is supplied. In the vat 13, a paper layer of mica scales is formed on the circular screen 14, transferred to the surface of the reinforcing sheet 2, and dried, so that the mica paper 1 and the glass paper as the reinforcing sheet 2 have the weight shown in Table 2. A mica sheet 3 having the layer structure shown in FIG. 2a in which the and the like were integrally laminated was obtained (mica sheet No. 4). Production of prepreg The resin varnish shown in Table 3 was applied to the mica sheet 3 thus obtained using the apparatus shown in Fig. 7 to a resin content of 55.
%, further heat-dried under the conditions shown in Table 3, and cut into predetermined dimensions to obtain mica sheet base material prepreg 5 using mica sheet 3 as a base material (prepreg No. 1). ~No.7).

【table】

[Table] Manufacture of copper-clad printed wiring board Six sheets of the obtained prepreg 5 are stacked in the layer configuration shown in Table 4, and electrolytic copper foil 6 with a thickness of 35 μm is stacked on the outer surface of both outer layers of the prepreg 5. Heat and pressure molding was carried out under the conditions shown in Table 4 to obtain double-sided copper-clad printed wiring boards with a thickness of 1.6 mm (Examples 1 to 6). Comparative Example 1 Using kraft paper with a weight of 164 g/m ² as the base material,
This was impregnated with the phenolic resin varnish shown in Table 3 and dried to produce a paper base prepreg with a thickness of 0.26 mm. Six sheets of this paper-based prepreg are stacked, and electrolytic copper foil with a thickness of 35μ is stacked on the outer surface of both outer layers of this paper-based prepreg.
A double-sided copper-clad printed wiring board was obtained by molding in the same manner as in Example 1 shown in Table 4. Comparative Example 2 Commercially available glass cloth (WE18K manufactured by Nittobo Co., Ltd.
-ZB) was used as a base material, and was impregnated with the epoxy resin varnish shown in Table 3 and dried to create a glass base prepreg with a thickness of 0.27 mm. Six sheets of this glass base material prepreg are stacked, and electrolytic copper foil with a thickness of 35 μm is stacked on the outer surface of both outer layers of this glass base material prepreg, and then molded in the same manner as Example 2 in Table 4, and double-sided copper-clad printed wiring is formed. I got the board. Comparative Example 3 Commercially available glass cloth (WE18K manufactured by Nittobo Co., Ltd.
-ZB) was used as a base material, and this was impregnated with the polyimide resin varnish shown in Table 3 and dried to create a glass base material prepreg with a thickness of 0.27 mm. Six sheets of this glass base material prepreg are stacked, and electrolytic copper foil with a thickness of 35 μm is stacked on the outer surface of both outer layers of this glass base material prepreg, and is molded in the same manner as Example 5 in Table 4, and double-sided copper-clad printed wiring is formed. I got the board. Table 5 shows the results of measuring various properties of the copper-clad printed wiring boards obtained in Examples 1 to 6 and Comparative Examples 1 to 3.

【table】

【table】

【table】

[Table] As shown in Table 5, for each example using mica sheet as the base material, comparisons with paper and glass base materials can be seen in the volume resistivity and surface resistivity items. It is confirmed that the electrical insulation properties are significantly improved compared to the example. Furthermore, as can be seen in the items of dielectric constant and dielectric loss tangent related to high frequency characteristics, it is confirmed that the characteristics of each example are improved over those of each comparative example. Furthermore, it is confirmed that each Example is superior to each Comparative Example in terms of water absorption. [Effects of the Invention] As described above, the present invention applies a thermosetting resin liquid to a mica sheet formed by laminating a reinforcing sheet into which a resin liquid is permeated on the surface of a mica paper in which mica scales are assembled. A mica sheet base prepreg is created by impregnating and drying, and multiple sheets of this mica sheet base prepreg are stacked, and a metal foil is overlaid on the surface of the outermost layer of the mica sheet base prepreg, which is then heated and pressed. Because it is moldable, mica paper can be used as a base material for electrical insulation boards after being reinforced with a reinforcing sheet, and the excellent electrical insulation performance of mica in mica paper allows for good electrical insulation. It is possible to obtain a printed wiring board with excellent characteristics, and in mica paper, the agglomeration strength of mica scales is increased by laminating reinforcing sheets, and the mica sheet can be used as the base of the insulating substrate of the printed wiring board. When used as a material, even when impregnated with a thermosetting resin liquid, mica paper does not have the risk of losing its paper form due to the penetration of the thermosetting resin liquid, and also has a high resistance to the penetration of the thermosetting resin liquid. The reduction in tension in the mica paper caused by this can be reinforced with a reinforcing sheet, and as a result, when creating prepreg using the mica sheet as a base material, impregnation with thermosetting resin liquid and drying can be performed in a series of continuous steps. This means that printed wiring boards with excellent electrical properties can be manufactured with high productivity using mica as a base material. Moreover, the mica sheet, which is made by laminating a reinforcing sheet on mica paper, is not impregnated with resin in advance, but instead it is possible to select the type of thermosetting resin and impregnate it into the mica sheet depending on the application and desired performance. Using this method, a mica sheet base material prepreg can be created, and a variety of printed wiring boards with different impregnated resins can be manufactured using one type of mica sheet. In addition, mica scales were assembled by filtering a slurry in which mica scales were dispersed onto the surface of a circular screen and transferring it to the surface of a reinforcing sheet into which resin liquid was permeated. Since a mica sheet is created by laminating mica paper and a reinforcing sheet, mica paper can be created without the need to use a resin binder using the round net method, and the mica paper and reinforcing sheet can be laminated. It is now possible to create a mica sheet that does not contain resin in advance, and by impregnating this mica sheet with a selected type of thermosetting resin depending on the application and desired performance, it is possible to create a mica sheet base prepreg. This makes it possible to manufacture various types of printed wiring boards with different impregnated resins using a type of mica sheet.

[Brief explanation of the drawing]

Figures 1a and b are cross-sectional views of each step in the manufacturing of printed wiring boards, Figures 2a, b, and c are front views of various aspects of the mica sheet in the same manner as above, and Figure 3 is a diagram of the equipment for manufacturing the mica sheet. FIG. 4 is a partial schematic diagram showing one example, and FIG. 4 is a cross-sectional view of a state in which a paper sheet is made from felt. FIG. Fig. 6 is a cross-sectional view of the laminated sheet, Fig. 7 is a schematic diagram showing an apparatus for manufacturing prepreg, Fig. 8 a, b is a cross-sectional view of each step of manufacturing a printed wiring board, and Fig. 9 a, b, c. , d are cross-sectional views showing combinations of prepregs obtained from mica sheets of various embodiments. 1 is a mica paper, 2 is a reinforcing sheet, 3 is a mica sheet, 4 is a thermosetting resin liquid, 5 is a prepreg, and 6 is a metal foil.

Claims (1)

[Claims] 1. Mica scales are dispersed by filtering a slurry in which mica scales are dispersed onto the surface of a circular screen to form a paper, and transferring this to the surface of a reinforcing sheet into which resin liquid is permeated. A mica sheet is created by laminating the assembled mica paper and a reinforcing sheet, and this mica sheet is impregnated with a thermosetting resin liquid and dried to create a mica sheet base material prepreg. A method for manufacturing a printed wiring board, comprising stacking a plurality of prepregs, stacking a metal foil on the surface of the outermost layer of the mica sheet base prepreg, and molding this under heat and pressure. 2. The method of manufacturing a printed wiring board according to claim 1, wherein the mica sheet is created by laminating a reinforcing sheet on one side of mica paper. 3. The method of manufacturing a printed wiring board according to claim 1, wherein the mica sheet is created by laminating reinforcing sheets on both sides of the mica paper. 4. The method of manufacturing a printed wiring board according to claim 1, wherein the mica sheet is created by laminating a reinforcing sheet between two mica papers.