JPH0329574B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for manufacturing perforated laminates. [Background Art] In recent years, electronic devices have become lighter, thinner, shorter, and smaller.In particular, extremely thin devices such as IC cards are now required. It has become necessary to embed electronic components 6 such as IC chips inside. The printed wiring board 5 is formed by providing a circuit 8 on the surface of a laminate 7 serving as an insulating layer, and in the case of the one shown in FIG. The electronic component 6 is mounted by embedding the electronic component 6 and connecting the electronic component 6 and the circuit 8 with a lead wire 10. In order to obtain the printed wiring board 5 provided with the recesses 9 as described above, conventionally, the recesses 9 are formed in the laminated board 7 of the printed wiring board 5 by mechanical counterboring. However, this method requires a high degree of precision and is extremely inefficient, resulting in poor yield. Therefore, when manufacturing a laminate by laminating and molding multiple sheets of prepreg and metal foil, holes are made in the prepreg in advance so that the recesses 9 as described above are formed at the same time as the laminate is manufactured. It is being considered to make it In other words, holes are made in a predetermined size and shape in a predetermined position in each of multiple sheets of prepreg, and with the holes matching, the prepregs are stacked, and then a metal foil such as copper foil is layered, and this is heated and pressed. By doing so, a metal foil-clad laminate in which a recess 9 for embedding the electronic component 6 is formed using a hole provided in the prepreg is obtained. However, this method has a problem in that if the melt viscosity of the resin of the prepreg is low, the resin of the prepreg flows into the holes during hot-press molding, making it difficult to form the desired recesses 9. Therefore, prepreg that has been impregnated and dried with a resin with a high melt viscosity is used. However, if the melt viscosity of the resin in the prepreg is high, the flow of the resin during heating and pressure molding will be poor, and the resin will be contained in the prepreg. This has caused a problem in that the gas components cannot be sufficiently removed and remain as voids in the laminate, making it impossible to obtain a laminate with sufficient performance. [Object of the Invention] The present invention has been made in view of the above points, and is aimed at preventing resin from flowing into the holes when manufacturing a perforated laminate using prepreg with holes. It is an object of the present invention to provide a method for manufacturing a laminate that can prevent the occurrence of voids. [Disclosure of the Invention] According to the method for manufacturing a laminate according to the present invention, holes 2 are provided in the prepreg 1, and the holes 2 are filled with a releasable filler 3, and the prepreg 1 is heated in a reduced pressure atmosphere. The present invention is characterized by pressure molding, and the present invention will be explained in detail below. The prepreg 1 is formed by impregnating a base material with a thermosetting resin varnish and heating and drying it, and the base material may include inorganic fibers such as glass fiber cloth, glass nonwoven fabric, Tetron cloth, and paper. Organic fibers such as base materials and mixed base materials of inorganic fibers and organic fibers in any ratio can be used, and as thermosetting resins, epoxy resins, polyimide resins,
Polyester resins, phenolic resins, modified resins of these resins, etc. can be used. Here, the resin in the B stage state after being impregnated into the prepreg 1 and dried is transferred to the holes provided in the prepreg 1.
In order to reduce the flow during forming into the laminate and ensure the thickness accuracy of the laminate, the melt viscosity is
It is preferable to set it in the range of 300 to 5000 poise (measurement temperature 120℃), especially the lower limit of melt viscosity is 1000 poise.
It is preferable to set it to poise. Holes 2 of a predetermined shape and size are provided at predetermined positions in the prepreg 1 formed as described above. The holes 2 can be punched or cut out by punching or other suitable means. Then, one or more sheets of the prepreg 1 are stacked, the holes 2 are filled with the releasable filler 3, and then a metal foil 4 such as copper foil is stacked as shown in FIGS. 1a and 1b, and then heated. By pressing, it is used for lamination molding. When a plurality of prepregs 1 are stacked here, the prepregs 1 are stacked so that the holes 2 of each prepreg 1 match. The releasable filler 3 is one that has releasability with respect to the resin of the prepreg 1, such as Teflon (tetrafluoroethylene resin).
It can be formed from silicone or silicone, and can be used in the form of powder or granules in addition to sheet form. When the releasable filler 3 is formed into a sheet shape,
Its size is +0 mm to -2.0 mm, preferably +0 mm to -1.0 mm of the size of hole 2 provided in prepreg 1.
, the thickness is the depth of hole 2 (total depth of hole 2 when molding multiple sheets of prepreg 1) +
It is best to set it to 0.5 mm to -0 mm, preferably +0.1 mm to -0 mm, and when the releasable filler 3 is in the form of powder or granules, it is set to +10% to -0 of the volume of the hole 2.
It is advisable to use a volume of 0%, preferably +5% to -0%. Further, lamination molding is performed under reduced pressure atmosphere conditions, and for example, by installing a lamination molding apparatus in a reduced pressure chamber, lamination molding can be performed under reduced pressure atmosphere conditions. The decompression conditions are
It is preferable to set the vacuum state to 150 Torr or less, preferably 100 Torr or less. By heating and pressing a laminate of prepreg 1 and metal foil 4 to form it as described above, a metal foil-clad laminate in which recesses 9 for embedding electronic components 6 are formed with holes 2 is obtained. By processing this metal foil by etching or the like to form a circuit 8, a printed wiring board 5 as shown in FIG. 2 can be completed. Here, since the hot-press molding is performed under a reduced pressure atmosphere, even if the melt viscosity of the resin of the prepreg 1 is high, the gas components in the prepreg 1 are degassed, and there is no fear that voids will occur in the laminate. Therefore, it is possible to perform molding using the prepreg 1 whose resin has a high melt viscosity without the resin flowing into the holes 2 provided in the prepreg 1. Furthermore, since the holes 2 are filled with the releasable filler 3 filled in the holes 2, the molten resin of the prepreg 1 is also prevented from flowing into the holes 2. Can be done. Mold releasable filler 3
Of course, it is removed after molding. As described above, since the forming is carried out under a reduced pressure atmosphere, the metal foil 4 overlaid on the prepreg 1 is likely to be dented and deformed by being sucked inward at the hole 2. By filling the holes 2 with the releasable filler 3, this fear is eliminated. In addition to providing the holes 2 in the prepreg 1, the holes 2 are also provided in the metal foil 4 or in the inner layer material in the case of a multilayer laminate with three or more layers, and these holes 2 are filled with a releasable filler 3. Molding can be performed by Next, the present invention will be further explained by examples. Example 1 By impregnating 200 g/m ² of glass cloth with a hardening agent-containing epoxy resin varnish and drying it,
A prepreg of g/m ² was prepared. This prepreg had a resin melt viscosity of 1200 poise (prepreg A). As shown in FIG. 3, holes each having a diameter of 10 mm were formed in nine locations in this prepreg by punching. Two sheets of this prepreg are stacked to a thickness of 10 mm in diameter.
A 0.3 mm Teflon sheet (mold releasable filler 3 in Figure 1) is inserted into the hole of the prepreg as shown in Figure 1 a and b, and a copper foil with a thickness of 0.070 mm is layered on one side, and the other side is The laminate was sandwiched between metal plates and molded at a pressure of 50 Kg/cm ² and a temperature of 170°C under a reduced pressure atmosphere of 50 Torr.
Heat and pressure molding is performed for 100 minutes, and the thickness
A 0.4 mm copper clad laminate was obtained. Example 2 By impregnating 200 g/m ² of glass cloth with a curing agent-containing epoxy resin varnish and drying it,
A prepreg of g/m ² was prepared. This prepreg had a resin melt viscosity of 800 poise (prepreg B). Using this prepreg, a copper-clad laminate having a thickness of 0.4 mm was obtained in the same manner as in Example 1 except for the above. Example 3 By impregnating 200 g/m ² of glass cloth with a curing agent-containing epoxy resin varnish and drying it,
A prepreg of g/m ² was prepared. This prepreg had a resin melt viscosity of 500 poise (prepreg C). Using this prepreg, a copper-clad laminate having a thickness of 0.4 mm was obtained in the same manner as in Example 1 except for the above. Comparative Example 1 Prepreg A was used and the thickness was changed in the same manner as in Example 1 except that the heating and pressure molding was performed in a normal pressure atmosphere.
A 0.4 mm copper clad laminate was obtained. Comparative Example 2 Prepreg B was used, and the thickness was
A 0.4 mm copper clad laminate was obtained. Comparative Example 3 Prepreg C was used, and the thickness was
A 0.4 mm copper clad laminate was obtained. Comparative Example 4 A copper-clad laminate with a thickness of 0.4 mm was obtained in the same manner as in Example 1, except that prepreg A was used and hot pressure molding was performed without inserting a Teflon sheet into the holes of the prepreg. Comparative Example 5 A copper-clad laminate with a thickness of 0.4 mm was obtained in the same manner as in Example 1, except that prepreg B was used and hot-pressure molding was performed without inserting a Teflon sheet into the holes of the prepreg. Comparative Example 6 A copper-clad laminate with a thickness of 0.4 mm was obtained in the same manner as in Example 1, except that prepreg C was used and hot-pressure molding was performed without inserting a Teflon sheet into the holes of the prepreg. The conditions of Examples 1 to 3 and Comparative Examples 1 to 6 are summarized in Table 1. In addition, regarding the copper-clad laminates obtained in Examples 1 to 3 and Comparative Examples 1 to 6, moldability, variation in plate thickness (R), flow of resin into holes,
The appearance of the copper foil in each hole was measured. The results are shown in Table 2. In Table 2, "formability" is evaluated based on whether or not voids are generated in the laminate, with "○" indicating no voids and "△" indicating some voids. Cases in which a large number of occurrences occurred are marked with an "x". In addition, "plate thickness variation" was expressed as the difference between the maximum thickness and the minimum thickness measured by measuring the plate thickness with a micrometer. “Resin flow into the hole” and “Copper foil appearance at the hole”
This was done by visual observation and is illustrated in FIGS. 4 and 5. In FIG. 4, the resin that has flowed into the hole 2 is indicated by the reference numeral 11. Furthermore, in "Appearance of copper foil at hole area", "OK" means that no dent deformation occurred in the copper foil at the hole area.

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[Table] As shown in Table 2, it was confirmed that each example in which molding was performed under a reduced pressure atmosphere was able to reduce the occurrence of voids even if the melt viscosity of the prepreg resin was high (comparison). (See Examples 1 to 3 for comparison), and each example in which molding was performed with a Teflon sheet inserted into the hole of the prepreg, can reduce the flow of resin into the hole and prevent the copper foil from forming in the hole. It is confirmed that the occurrence of dent deformation can be prevented (see Comparative Examples 4 to 6 for comparison). Furthermore, in order to completely prevent the resin from flowing into the holes, it is confirmed that it is desirable to use a resin with a melt viscosity of 1000 poise or more as the prepreg. [Effects of the Invention] As described above, in the present invention, holes are provided in the prepreg, and the holes are filled with a releasable filler, and then the prepreg is heated and pressure molded in a reduced pressure atmosphere. Therefore, even if the prepreg resin has a high melt viscosity, the gas components in the prepreg will be degassed in a reduced pressure atmosphere, and there is no risk of voids forming in the laminate. It is possible to perform molding without resin flowing into the holes.
Moreover, the pores are filled with the releasable filler 3, and the resin can be prevented from flowing into the pores by the releasable filler 3. As a result, When producing a perforated laminate using a prepreg with holes, molding can be carried out without fear of resin flowing into the holes or generation of voids.

[Brief explanation of drawings]

1A and 1B are a partially cutaway perspective view and a partially cutaway sectional view of an embodiment of the present invention, FIG. 2 is a partially cutaway sectional view showing a printed wiring board in which electronic components are embedded, and FIG. Reduced plan view of prepreg with holes, 4th
Figures a to i are partial plan views showing the state of "resin flow into the hole" in Table 2, and Figures a, b, and c show the state of "copper foil appearance at the hole" in Table 2. FIG. 1 is a prepreg, 2 is a hole, and 3 is a releasable filler.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a laminate, which comprises providing holes in the prepreg and heating and press-molding the prepreg in a reduced pressure atmosphere with the holes filled with a releasable filler. 2. The method for manufacturing a laminate according to claim 1, wherein the prepreg has a resin having a melt viscosity of 1000 poise or more.