Cushioning material for hot press and method for manufacturing multilayer board

Abstract

A cushioning material 1 for a hot press has a flat plate shape, and is used for a pin lamination type hot press in which a positioning guide pin 51 is inserted into a through-hole provided in a to-be pressed object and hot pressing is performed. The cushioning material 1 for a hot press includes: a cushioning material body 2 in which a plurality of through-holes 2a for inserting a guide pin 51 are formed in a thickness direction at a prescribed position in the vicinity of an outer edge 2d; and a fixing member 5 which includes a cover member 4 having an outside surface that contacts a side surface of the through hole 2a, and fixes the outside surface of the cover member 4 and the side surface of the through-hole 2a. The cushioning material 1 for a hot press makes it possible to avoid breakage when the guide pin is inserted.

Description

Cushioning material for hot press and method for manufacturing multilayer board

[0001] The present invention relates to a cushioning material for hot press and a method for manufacturing a multilayer board.

[0002] In the manufacture of laminates such as multilayer substrates, copper-clad laminates, printed circuit boards, flexible printed circuit boards, and rigid-flex printed circuit boards, as well as precision instrument parts such as IC cards, liquid crystal display panels, and batteries (hereinafter collectively referred to as "laminates"), materials are subjected to press molding and thermocompression bonding. In these processes, heat-press cushioning materials are used to uniformly transfer heat and pressure to the object being pressed. Examples of heat-press cushioning materials include paper cushioning materials that are disposable after one press, as well as reusable cushioning materials made of composite materials such as heat-resistant fibers, heat-resistant rubber, and heat-resistant resin.

[0003] Among laminates formed by hot pressing, multilayer boards, especially those with densely designed circuits, require high precision in aligning each layer due to the increasing number of layers and the increasing precision of the circuit patterns. Multilayer boards are manufactured by alternately stacking inner-layer printed circuit boards and prepregs in multiple layers, and then layering copper foil (conductors) on the top and bottom layers, followed by heat and pressure treatment. Prepregs are resin sheets made by impregnating glass cloth with a thermosetting resin to create a semi-cured state. During heat and pressure treatment, the semi-cured resin in the prepregs melts and acts as an adhesive. A known manufacturing method for multilayer boards is the pin lamination method, in which guide pins are inserted into holes drilled in the multilayer board material (production intermediate) to precisely align the positions of each layer (see, for example, Patent Document 1). When press-forming or thermocompression-bonding the laminate material (production intermediate) using the pin lamination method, a hot press cushioning material is used to uniformly transmit temperature and pressure. During the heat pressing, cushioning material is placed between the hot platen and the intermediate product, and heat and pressure from the hot platen is applied evenly and at an appropriate speed to each part of the intermediate product, thereby producing a high-quality laminate.

[0004] In the pin lamination method, similar holes are also drilled in the cushion material, and guide pins are inserted into the holes before the cushion material is subjected to heat pressing. The present applicant has proposed the technology described in Patent Document 2 as a heat pressing cushion material used in this pin lamination method.

[0005] JP 2008-282857 A JP 2024-84149 A

[0006] In hot pressing using the pin lamination method, there is a problem in that the resin of the prepreg melted by heat flows along the guide pins and out of the holes through which the guide pins pass. If the outflowing resin adheres and solidifies on the surface, back surface, and inner surface of the holes of the cushioning material, the cushioning properties of the finished cushioning material are reduced, causing uneven pressure and contamination of the manufacturing intermediates. For this reason, in hot pressing using the pin lamination method, paper cushioning material is often used as the hot pressing cushioning material, which is mainly disposable after one press. If the hot pressing cushioning material could be reused, it would be possible to efficiently manufacture multilayer boards with high-resolution circuit patterns, but this has been difficult to use with the pin lamination method.

[0007] Therefore, when using the hot press cushioning material proposed in Patent Document 2, careful insertion of the guide pin allows for repeated use, but some workers may insert the hot press cushioning material carelessly, causing impact on the protective material of the hot press cushioning material or the covering material covering the side of the hole, resulting in the protective material or covering material peeling off or coming loose, which can result in the hot press cushioning material not being reusable.

[0008] An object of the present invention is to provide a hot-press cushioning material for use in pin lamination hot pressing that can be used repeatedly for a long period of time without being damaged when a guide pin is inserted, and to provide a method for manufacturing a multilayer substrate using such a hot-press cushioning material.

[0009] The present invention provides the following hot press cushioning material and method for manufacturing a multilayer substrate.

[0010] (1) A flat-plate-shaped cushioning material for hot pressing used in pin lamination type hot pressing, in which a guide pin is inserted into a through hole provided in an object to be pressed to perform hot pressing, the cushioning material for hot pressing comprising: a cushioning material body having a plurality of through holes formed in the thickness direction for inserting the guide pins; and a covering member having an outer surface that contacts the side of the through hole, the outer surface of the covering member and the side of the through hole being fixed by a fixing member.

[0011] (2) The hot press cushioning material of (1), wherein the covering member is a porous fluororesin member, and recesses and / or protrusions are formed on the outer surface, and the fixing members are provided on the recesses and / or protrusions.

[0012] (3) The hot press cushioning material according to (1) or (2), wherein the fixing member is one or more selected from fluorine, silicone, acrylic, EPM, EPDM, hydrogenated nitrile, and butyl.

[0013] (4) The hot press cushioning material according to (1) or (2), wherein the fixing member is one or more selected from the group consisting of epoxy, polyimide, polyphenylene ether, phenol, urethane, urea, melamine, unsaturated polyester, and silicone.

[0014] (5) The hot press cushioning material according to any one of (1) to (4), wherein the front and back surfaces of the cushioning material body are provided with a protective material that covers the periphery of the through-hole.

[0015] (6) A method for manufacturing a multilayer substrate, comprising: superposing the hot press cushioning material according to any one of (1) to (5) on a manufacturing intermediate having a laminated structure of a substrate layer, an adhesive layer, and a conductor layer and having a plurality of through holes formed in the thickness direction; and applying pressure and heat from a hot platen of a press machine to the manufacturing intermediate via the hot press cushioning material while the guide pin is inserted through the through holes formed in the manufacturing intermediate and the through holes formed in the hot press cushioning material.

[0016] The hot-press cushioning material of the present invention can prevent damage during guide pin insertion in the pin lamination method, allowing the hot-press cushioning material to be used repeatedly for a long period of time. Furthermore, by using such a hot-press cushioning material, it is possible to efficiently manufacture high-precision multilayer substrates.

[0017] FIG. 1 is a schematic perspective view of a hot-press cushioning pad 1 according to an embodiment of the present invention. FIG. 2 is a plan view showing an enlarged portion of the hot-press cushioning pad 1 according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along the line A-A' in FIG. 2. FIGS. 4A to 4D are schematic diagrams illustrating a method for manufacturing the hot-press cushioning pad 1. FIG. 5 is a schematic diagram showing the periphery of a through-hole in the hot-press cushioning pad 1. FIG. 6A is a schematic diagram illustrating a method for manufacturing a multilayer substrate using a pin lamination method, and FIG. 6B is an enlarged view of a manufacturing intermediate 40 shown in FIG. 6A. FIGS. 7A to 7C are schematic diagrams showing the periphery of a through-hole in the hot-press cushioning pad 1 according to a modified embodiment of the present invention. FIG. 8 is a schematic diagram showing a cushioning pad of a comparative example that does not include a fixing member.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this specification and drawings, substantially identical components are designated by the same reference numerals, and redundant description will be omitted.

[0019] FIG. 1 is a schematic perspective view of a hot press cushion material 1 according to an embodiment of the present invention. FIG. 2 is a plan view showing an enlarged portion of the hot press cushion material 1 according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along the line A-A' in FIG. 2. The hot press cushion material 1 is a flat-plate hot press cushion material used in pin lamination-type hot pressing, in which alignment guide pins 51 provided in a press machine for pressing laminates such as copper-clad laminates, printed circuit boards, flexible printed circuit boards, and rigid-flex printed circuit boards are inserted into through holes provided in the object to be pressed to perform hot pressing. The hot press cushion material 1 (hereinafter also simply referred to as the cushion material) is, for example, a rectangular flat plate.

[0020] The cushion material 1 has a cushion material main body 2 having a plurality of through holes 2a formed therein, a protective material 3 covering the periphery of each through hole 2a, and a covering member 4 and a fixing member 5 that protect the inner diameter side surface of the through holes 2a.

[0021] <Cushioning Material Main Body> The cushioning material main body 2 is a flat plate-shaped member. The cushioning material main body 2 has a main body layer and surface layers provided on the front and back surfaces of the main body layer. The main body layer is, for example, a layer of a fiber-rubber composite material made of woven fabric and rubber impregnated into the woven fabric. The thickness of the main body layer is approximately 0.5 mm to 5 mm. Note that the main body layer does not necessarily have to be a layer of a woven fabric-rubber composite material, and may have a structure that has been conventionally used for main layers. In other words, the main body layer may have a single layer structure or a laminate structure of the same or different layers of any of woven fabric, nonwoven fabric, rubber, and synthetic resin, either singly or as a composite of two or more types.

[0022] The surface layers provided on the front and back surfaces of the main body layer are provided mainly to impart mold releasability to the cushioning material main body 2. The surface layers have, for example, a core layer formed from a woven or nonwoven fabric of a heat-resistant fiber material, a surface resin layer covering the entire surface of the core layer, and a back rubber layer covering the entire back surface of the core layer and adhered to the main body layer.

[0023] The surface resin layer described above is a thin film that shows the irregularities of the fibers in the core layer, and of the surface layers, it forms the outer surface of the cushion material 1. Because the irregularities of the fibers in the core layer are visible in the surface resin layer, the cushion material is prevented from adhering closely to the heating plate 52 and stainless steel plate 55 described below. The material for the surface resin layer, i.e., the surface layer 2b and back surface of the cushion material main body 2, is not particularly limited as long as it is a resin that has mold releasability, but fluororesin or highly heat-resistant polyimide resin is preferred.

[0024] In the cushion material body 2 having the above-described configuration, guide pins 51 for alignment are inserted into the multiple through holes 2a. The cross section of the guide pin 51 is circular or oval, for example, and its maximum outer diameter is 3 mm to 15 mm. The inner diameter of the through holes 2a is 5 mm to 20 mm, for example. The planar shape of the through holes 2a is circular or oval, for example, and the specific shape is not limited. The multiple through holes 2a are formed in the thickness direction T at predetermined positions near the outer edge 2d of the cushion material body 2. In this case, the "predetermined positions" are, for example, within a range of several mm to 10 cm from the outer edge 2d. The predetermined positions at which the through holes 2a are formed are positions determined for each product to be heat-pressed using the pin lamination method, and correspond to the positions at which the guide pins 51 are installed.

[0025] <Covering Member and Fixing Member> The covering member 4 is a porous fluororesin material, and recesses and / or protrusions are formed on the outer surface of the covering member 4. For example, if the covering member 4 is cylindrical, the recesses and protrusions are formed in a recessed shape (e.g., an obtuse angle, acute angle, rectangular, or rounded shape on the inner periphery) around the center of the outer surface in the thickness direction (the same direction as the thickness direction of the cushioning material 1). A guide pin 51 is inserted into a hole surrounded by the inner edge of the covering member 4. The porous fluororesin material is a material that does not deform when heated but deforms when pressurized. Therefore, it can deform in accordance with the deformation in the thickness direction T of the cushioning material 1 when pressed in a press machine. In other words, pressure differences are less likely to occur around the holes in the covering member 4 through which the guide pins 51 are inserted, enabling repeated, uniform transfer of heat and pressure to the object being pressed.

[0026] The fixing member 5 is made of a rubber material or a thermosetting resin material. Examples of rubber materials include one or more selected from fluorine, silicone, acrylic, ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), hydrogenated nitrile, and butyl. Examples of thermosetting resin materials include one or more selected from epoxy, polyimide, polyphenylene ether, phenol, urethane, urea, melamine, unsaturated polyester, and silicone. When high heat resistance is required, a highly heat-resistant polyimide resin is preferred.

[0027] If the fixing member 5 is made of a rubber material, its elasticity allows it to flexibly deform in response to the pressure applied by the press, making it less likely to cause pressure differences around the holes in the covering member 4 through which the guide pins are inserted, and making it possible to repeatedly and uniformly transmit heat and pressure to the object being pressed. On the other hand, if the fixing member 5 is made of a thermosetting resin material, the covering member and the cushioning material main body 2 can be firmly and firmly bonded together. As a result, even if the guide pins impact the covering member 4, it will not easily break or come off.

[0028] <Protective material> The protective material 3 is provided to prevent the molten resin from directly adhering to the cushion material main body 2 when, during pin lamination type hot pressing, the resin of the intermediate manufacturing product, which is the object to be pressed, melts due to heat and flows out between the guide pin 51 and the side surface of the through hole of the cushion material 1 (the inner diameter side surface of the covering member 4). This prevents the molten resin from adhering and solidifying during hot pressing, and prevents contamination of the intermediate manufacturing product.

[0029] One protective material 3 is provided on the front and back surfaces of the cushion material body 2 for each through hole 2a. The protective material 3 covers the periphery of the front surface 2b and back surface of the through hole 2a of the cushion material body 2. The range in which the protective material 3 covers the periphery of the through hole 2a on the front surface 2b and back surface of the cushion material body 2 is determined depending on the temperature and pressure during hot pressing, the material of the prepreg used in the manufacturing intermediate, and other factors. The protective material 3 covers at least the area from which the resin may flow out, thereby preventing the molten resin from coming into direct contact with the front surface 2b and back surface of the cushion material body 2.

[0030] The protective material 3 has a protective material hole 3a formed therein through which the guide pin 51 passes. The inner diameter of the protective material hole 3a is larger than the outer diameter of the guide pin 51. The protective material 3 is composed of a release sheet 3b and a bonding agent 3c made of an adhesive or pressure-sensitive adhesive. For example, by forming the release sheet 3b from a fluororesin and the bonding member 3c from a fluororubber, and subjecting the fluororubber to plasma treatment or corona treatment, it is possible to improve bonding to the cushion material body 2 while maintaining releasability from the hot platen of a heat press machine or a stainless steel plate, and from the molten resin of the prepreg. Furthermore, by forming the release sheet 3b from silicone, it is possible to further improve releasability. Note that if the bonding agent 3c is made of fluororubber, which requires vulcanization, it will be firmly bonded to the cushion material body 2 by vulcanization. On the other hand, if the bonding agent 3c is made of an adhesive such as silicone, it can be easily replaced in the event of peeling because vulcanization is not required.

[0031] It is preferable that each protective material 3 has the same configuration to increase its versatility as a protective seal. The thickness of the protective material 3 is 0.01 mm to 0.50 mm, and preferably approximately 0.03 mm to 0.20 mm. By making the protective material 3 an appropriate thickness depending on the material, the protective material 3 can be made less likely to tear and can ensure appropriate flexibility. It is preferable to use a material for the protective material 3 that has higher releasability against the resin that melts, adheres, and then hardens than the releasability of the front surface 2b and back surface 2b of the cushion material main body 2.

[0032] In this embodiment, the protective material 3 is composed of a release sheet 3b that forms the outer surface, and a joining member 3c that attaches the release sheet 3b to the cushion material body 2. The thickness of the protective material 3 is preferably thin enough not to impair the function of applying pressure from the hot platen evenly to the object to be pressed during pressing.

[0033] The release sheet 3b is formed of a material that has excellent releasability against the resin that has melted, adhered to it, and solidified. The releasability of the release sheet 3b is the releasability of the protective material 3. As an index for specifying the releasability, wettability, which measures the contact angle of a liquid droplet, can be used.

[0034] In this embodiment, the contact angle of a liquid droplet on the release sheet 3b (protective material 3) is larger than the contact angle of a liquid droplet on the front surface 2b and back surface 2b of the cushion material main body 2. The contact angle of a liquid droplet is measured using a water droplet. It can be said that the larger the contact angle, the higher the hydrophobicity. In other words, the larger the contact angle, the better the releasability. The contact angle of the release sheet 3b is larger than the contact angle of the cushion material main body 2, and is therefore highly hydrophobic. As a result, the resin that has melted and adhered to the protective material 3 and hardened can be peeled off more easily than the resin that has adhered to the cushion material main body 2 and hardened.

[0035] The wettability can be evaluated, for example, by a test method conforming to JIS (Japanese Industrial Standards) R 3257 (Test method for wettability of substrate glass surfaces). Examples of objects for evaluating wettability include: (1) the cushion material 1 itself; (2) any single protective material 3 placed on a smooth surface; or (3) any single release sheet 3b of the protective material 3 placed on a smooth surface. When the cushion material 1 itself in (1) above is the object for evaluation, the cushion material 1 may be in a new state, or may be in a used state after being heat-pressed a certain number of times.

[0036] The release sheet 3b is preferably selected from the group consisting of fluorine, silicone, polyimide, polyamide, PPS (polyphenylene sulfide), PET (polyethylene terephthalate), polyurethane, polypropylene, and polyethylene. Examples of fluororesins include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), and FEP (perfluoroethylene propene copolymer). Examples of silicone resins include methyl silicone, phenyl silicone, methyl phenyl silicone, and modified silicone. Using these materials for the release sheet 3b can improve the releasability of the resin that melts, adheres, and hardens. While a resin with releasability is used for the surface resin layer of the cushion material body 2, selecting a material for the release sheet 3b of the protective material 3 that has a larger droplet contact angle than the surface resin layer of the cushion material body 2 makes it easier to peel off the resin that melts, adheres, and hardens on the protective material 3 than the resin that adheres to the cushion material body 2.

[0037] The joining member 3c is provided to join the release sheet 3b to the surface of the cushion material body 2, and is preferably made of a material that has excellent adhesion to the surface and can withstand the temperature of the heat press (for example, about 190°C to 230°C). The joining member 3c is made of an adhesive or pressure-sensitive adhesive. Examples of materials that can be used for the joining member 3c include one or a mixture of two or more selected from the group consisting of fluororubber, silicone rubber, acrylic rubber, ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), hydrogenated nitrile rubber, and butyl rubber.

[0038] When the release sheet 3b is made of a fluororesin and the bonding member 3c is made of a fluororubber, or when the release sheet 3b is made of a fluororesin and the adhesive layer is made of silicone rubber, these are preferable because they adhere after melting and have good releasability from the hardened resin, have high heat resistance, and provide sufficient adhesive strength to the cushion material body 2. The protective material 3 and the cushion material body 2 are joined together by, for example, pressure-sensitive adhesive or vulcanization adhesion.

[0039] With the above-described configuration, the cushion material body 2 is completely covered around the through-hole 2a by the protective material 3 and the covering member 4, and the molten resin during pressing is prevented from reaching the opposite surface through the through-hole of the cushion material body 2. Even if the resin does reach the surface and adhere to it, it can be easily peeled off because a material with high releasability is used, allowing the cushion material 1 to be used repeatedly.

[0040] The above is the overall configuration of the cushioning material 1. Next, a method for manufacturing the cushioning material 1 will be described.

[0041] <Method of manufacturing a hot-press cushioning material> Figures 4(A) to 4(D) are schematic diagrams illustrating a method of manufacturing the cushioning material 1. Figure 4(A) is a side view of the covering member material 45. Figure 4(B) is a side view of the covering member material 45 with the fixing member 5 fitted therein. Figure 4(C) is a side view of the covering member material 45 with the fixing member 5 fitted therein, inserted into the cushioning material body 2. Figure 4(D) is a diagram showing the state after the semi-finished product of Figure 4(C) has been heat-treated. Note that in Figures 4(B) to (D), the fixing member 5 is shown semi-transparent. Figures 4(C) and 4(D) also show cross sections of the cushioning material body 2.

[0042] When manufacturing the cushion material 1, first, a plurality of through holes 2a in the thickness direction are formed at predetermined positions near the outer edge of the cushion material body 2 by punching or the like. Next, as shown in FIG. 4(A), a cover member material 45 of a size that can be inserted into the through holes 2a is prepared. This cover member material 45 has a shape with an outer surface that contacts the side of the through hole 2a, is columnar, and is thicker than the cushion material body 2, and the central portion of the outer surface in the thickness direction is formed in a concave shape all around. If the shape of the inner surface of the through hole 2a is circular, the shape of the outer surface of the cover member material 45 should also be circular, and if the shape of the inner surface of the through hole 2a is oval, the shape of the outer surface of the cover member material 45 should also be oval. If the shapes are the same, when the fixing member 5, described later, foams upon heating, a force is applied uniformly all around, facilitating bonding of the cover member material 45 and the cushion material body 2.

[0043] Next, as shown in Fig. 4(B), the fixing member 5 is fitted into the recessed portion 4V formed in the covering member material 45. The fixing member 5 is fitted evenly around the entire periphery of the covering member material 45. Next, as shown in Fig. 4(C), the covering member 4 with the fixing member 5 fitted therein is inserted into the through-hole 2a of the cushion material body 2.

[0044] 4(D), pressure is applied from above and below and heat treatment is performed in a heating furnace oven so that the thickness of the covering member material 45 becomes the same as that of the cushion material body 2. The fixing member 5 foams due to the heat, and the fixing member completely fills the recessed portion 4V formed in the covering member material 45 and adheres to the side surface of the through-hole 2a of the cushion material body 2, thereby fixing the covering member material 45 to the cushion material body 2.

[0045] FIG. 5 is a schematic diagram showing the periphery of the through hole of the cushion material 1. Note that in this schematic diagram, the protective material hole 3a and the through hole 46 are shown as cut end surfaces passing through the central axes of the respective holes. In the region outside the inner surface of each hole, the protective material 3, the covering member 4, and the fixing member 5 are shown in side views, and the cushion material main body 2 is shown in cross section. The fixing member 5 is shown semi-transparent. As shown in FIG. 5, the protective material 3 is attached to the periphery of the through hole 2a, and the protective material 3 and the covering member material 45 are punched out to form the protective material hole 3a into which the guide pin 51 is inserted and the cylindrical covering member 4 having the through hole 46. This hot-press cushion material has an inner surface having a shape substantially the same as the outer peripheral shape of the cross section of the guide pin 51, and the outer surface of the covering member 4 is fixed to the side of the through hole 2a of the cushion material main body 2 by the fixing member 5.

[0046] Fig. 6(A) is a schematic diagram for explaining a method for manufacturing a multilayer substrate by the pin lamination method, and Fig. 6(B) is an enlarged view of a manufacturing intermediate product 40 of Fig. 6(A) . Referring to Fig. 6(A) and Fig. 6(B), a multilayer substrate is manufactured by hot pressing the manufacturing intermediate product 40 of the multilayer substrate, which is the object to be pressed, with a hot press machine.

[0047] The heat press machine has a pair of upper and lower heating plates 52, 52. The manufacturing intermediate 40 is configured by laminating a substrate layer 41, an adhesive layer 42, and a conductor layer 43. The substrate layer 41 is a printed circuit board, which serves as the inner layer. The adhesive layer 42 is, for example, a prepreg made by impregnating glass cloth with a thermosetting resin and semi-curing it. In FIG. 6(A), multiple manufacturing intermediates 40 are stacked in multiple layers, sandwiched between stainless steel plates 55. A pair of cushioning materials 1 is layered above and below the multiple manufacturing intermediates 40 and the stainless steel plates 55. These are then sandwiched between a pair of jigs 54, 54, and the entire assembly is placed between the heating plates 52, 52. Guide pins 51 are used to align each stack. While FIG. 6(A) shows an example in which multiple manufacturing intermediates 40 are heat-pressed together, a single manufacturing intermediate 40 may be the target of a single heat-press.

[0048] Holes for passing guide pins 51 for alignment are formed in multiple locations (e.g., four corners) in the thickness direction at predetermined positions near the outer edges of the cushioning material 1, stainless steel plate 55, and intermediate product 40. Between the upper and lower jigs 54, 54, the guide pins 51 are passed through the alignment holes formed in each of the cushioning material 1, stainless steel plate 55, and intermediate product 40. Accurate passing of the guide pins 51 through each component is required. The tips of the guide pins 51 are often rounded, but it is necessary to prevent the tips from impacting the through holes of each component. The cushioning material 1 is configured to be impact-resistant by the cover member 4, fixing member 5, and protective member 3. Both ends of the guide pin 51 fit into holes formed in the upper and lower jigs 54 and 54.

[0049] A pair of upper and lower heating plates 52, 52 sandwich a pair of upper and lower jigs 54, 54, and apply pressure and heat. Pressure is applied using a hydraulic cylinder or the like (not shown), and heating is applied by a heater provided on each heating plate 52. Pressure and heat from the heating plates 52, 52 are applied to each manufacturing intermediate 40 via the upper and lower jigs 54, 54, the upper and lower cushion materials 1, 1, and the stainless steel plate 55. As a result, the substrate layer 41, adhesive layer 42, and conductor layer 43 of the manufacturing intermediate 40 are integrated by the molten resin of the prepreg forming the adhesive layer 42, and the manufacturing intermediate 40 becomes a multilayer substrate. At this time, some of the molten resin from the adhesive layer 42 may reach the cushion material 1 through the guide pin 51 and the protective material hole 3a and the through hole 46 of the cover member 4 to the protective layer 3. However, because the protective material 3 has good releasability, resin adhering to the protective material 3 can be easily removed by hand or the like. Therefore, the cushioning material 1 can be repeatedly used in the press molding of multilayer substrates.

[0050] As described above, in this embodiment, the protective material 3 and the cover member 4 cover the front and side surfaces of the through-hole 2a of the cushion material body 2. As a result, even if an impact is received when inserting the guide pin 51 into the cushion material 1, the protective material 3 is not damaged because the cover member 4 is firmly bonded to the cushion material body 2 by the fixing member 5. Furthermore, when the intermediate product 40, which is the object to be pressed, is hot-pressed using the pin lamination method, resin flowing down the guide pin 51 from the intermediate product 40 is prevented from adhering to and solidifying on the cushion material body 2. Therefore, even after hot-pressing, resin from the intermediate product 40 does not soak into the cushion material body 2, thereby preventing performance degradation and damage to the cushion material body 2. This allows the cushion material 1 to be repeatedly used in the hot-pressing process of the intermediate product 40 several tens to several hundreds of times. <Modifications>

[0051] 7(A) to 7(C) are schematic diagrams showing the area around the through-hole of the hot press cushion pad 1 in a modified embodiment of the present invention. In these schematic diagrams, the protective material hole and the through-hole of the covering member are shown as cut end surfaces passing through the center axis of each hole. In the area outside the inner surface of each hole, the protective material 3, covering members 4a, 4b, and 4c, and fixing member 5 are shown in side views, and the cushion material main body 2 is shown in cross section. The fixing member 5 is shown semi-transparently. In FIG. 7(A), the outer diameter side surface of the covering member 4a has two acute-angled shapes toward the inner periphery. These two irregularities firmly secure the covering member 4a to the through-hole 2a via the foamed fixing member 5. In FIG. 7(B), the outer diameter side surface of the covering member 4b has one rectangular irregularity. In FIG. 7(C), the outer diameter side surface of the covering member 4c has two rectangular irregularities.

[0052] Cushioning materials equipped with a covering member and a fixing member were prepared as Examples 1 and 2, and a cushioning material equipped with a covering member but without a fixing member was prepared as a comparative example. The configurations of Examples 1 and 2 and the comparative example are as follows. FIG. 8 is a schematic diagram showing a cushioning material of the comparative example equipped with no fixing member. Note that in this schematic diagram, the protective material holes and the through-holes of the covering member are shown as cut end surfaces passing through the central axes of the respective holes. In the region outside the inner surface of each hole, the protective material 3 and the covering member 4n are shown in side views, and the cushioning material main body 2 is shown in cross-sectional views.

[0053] Example 1 Cushion material body: A cushion material manufactured by Yamauchi Corporation (YOM04VGR: 30 cm square, 4 mm thick) was prepared, and through-holes (inner diameter 12 mm) for inserting guide pins were drilled near the outer edge of this cushion material. The through-holes were drilled in a total of eight places, at the four corners and the centers of the four sides of the cushion material. Covering member material: Fluorine resin porous member (GORE Hyper Sheet Gasket (thickness 6.5 mm, outer diameter 12 mm) A recess approximately 1 mm deep was created around the entire side surface. The recess was shaped so that the center in the thickness direction of the outer surface was recessed by approximately 1 mm, and tapered outward (top and bottom in the thickness direction). Fixing member: A ring-shaped foamed fluororubber (outer diameter 12 mm, inner diameter 10 mm) was fitted into the recessed portion of the fluororesin porous member. The fluororesin porous member with the fitted ring-shaped foamed fluororubber was inserted into the through-hole of the cushion material body and pressurized to a thickness of 4 mm of the cushion material. Next, it was heated in a heating oven at 180°C for 1 hour. The heat treatment caused the ring-shaped foamed fluororubber to foam, completely filling the recessed portion created in the fluororesin porous member with rubber, and it further adhered to the side of the through-hole of the cushion material body, fixing the fluororesin porous member to the cushion material body. Protective material: After heating, two protective stickers (0.10 mm thick fluororesin (PTFE) tape, manufactured by Chukoh Chemical Industry Co., Ltd., ASF118AFR) with a silicone adhesive applied to one side were prepared and attached to the front and back surfaces of the cushioning material body. Next, a hole with an inner diameter of 8 mm was drilled in the porous fluororesin member with the fluororesin (PTFE) tape attached.

[0054] <Example 2> Cushion material body: A cushion material manufactured by Yamauchi Corporation (YOM04VGR: 30 cm square, 4 mm thick) was prepared, and through-holes (inner diameter 12 mm) for inserting guide pins were drilled near the outer edge of this cushion material. The through-holes were drilled in a total of eight places, at the four corners and the centers of the four sides of the cushion material. Covering member material: A recess approximately 1 mm deep was created around the entire side of a fluororesin porous member (GORE Hypersheet Gasket (thickness 6.5 mm, outer diameter 12 mm). The recess was shaped so that the centre in the thickness direction of the outer surface was recessed by approximately 1 mm, and tapered towards the outside (top and bottom in the thickness direction). Fixing member: The recessed portion of the fluororesin porous member was filled with epoxy resin varnish. The fluororesin porous member filled with epoxy resin varnish was inserted into the hole in the cushion material body and pressurized to a thickness of 4 mm for the cushion material. Next, it was heated in a heating oven at 180°C for 1 hour. The heat treatment caused the epoxy resin varnish to penetrate into the side surfaces of the through holes in the cushion material body and harden. This anchored the recessed portion created in the fluororesin porous member to the side surfaces of the through holes in the cushion material body, fixing the fluororesin porous member to the cushion material body. Protective material: A covering member equipped with a fixing member was fitted into the cushion material body and heated, and then two sheets of fluororesin (PTFE) tape (ASF118AFR, thickness 0.10 mm, manufactured by Chukoh Chemical Industry Co., Ltd.) with a silicone adhesive applied to one side were prepared as protective seals and attached to the front and back surfaces of the cushion material body. Next, a hole with an inner diameter of 8 mm was drilled in the fluororesin porous member with the fluororesin (PTFE) tape attached.

[0055] Comparative Example: Cushioning material body: A cushioning material manufactured by Yamauchi Corporation (YOM04VGR: 30 cm square, 4 mm thick) was prepared, and through-holes (inner diameter 12 mm) for inserting guide pins were drilled near the outer edge of this cushioning material. Through-holes were drilled in a total of eight locations: the four corners of the cushioning material and the centers of its four sides. Covering material: A fluororesin porous material (GORE Hyper Sheet Gasket (thickness 6.5 mm, outer diameter 12 mm)) was inserted into the through-hole in the cushioning material body, and the cushioning material was compressed to a thickness of 4 mm. Protective material: Two sheets of fluororesin (PTFE) tape (manufactured by Chukoh Chemical Industry Co., Ltd., ASF118AFR, thickness 0.10 mm) with a silicone adhesive coated on one side were prepared as protective stickers and attached to the front and back of the cushioning material body, respectively. Next, a hole with an inner diameter of 8 mm was drilled in the fluororesin porous material to which the fluororesin (PTFE) tape had been attached.

[0056] <Test Method> A guide pin was intentionally inserted and removed roughly into and from the through-holes in the cushioning materials of Examples 1 and 2 and the Comparative Example, simulating the actions of an inexperienced operator.

[0057]

[0058] Test evaluation results: The protective material was evaluated as ◯ when it was in good condition, △ when the protective material peeled off, and × when the protective material peeled off and / or the fluororesin porous material covering material came off.

[0059] In Examples 1 and 2, the cover member was fixed to the cushioning material body with a fixing member, and as a result, the cushioning material was rated as "Good" even after 200 insertions and removals of the guide pin, demonstrating that the cushioning material can withstand repeated use. On the other hand, in the comparative example, a fixing member was not used, and only a cover member was fitted and a protective material was attached, so after approximately 50 insertions and removals of the guide pin, the protective material peeled off and / or the fluororesin porous material covering member came off. From these results, it was possible to obtain a reusable hot press cushioning material in which the protective material does not break even when subjected to excessive impact when inserting the guide pin using the pin lamination method.

[0060] The present invention can be applied to a hot-press cushioning material and a method for manufacturing a multilayer substrate using the hot-press cushioning material.

[0061] REFERENCE SIGNS LIST 1 Hot press cushioning material 2 Cushioning material body 2a Through hole 2b Surface of cushioning material body 2d Outer edge 3 Protective material 3a Hole in protective material 4 Covering member 45 Covering member material 46 Through hole 5 Fixing member 40 Manufacturing intermediate (object to be pressed) 51 Guide pin

Claims

1. A flat-plate cushioning material for hot pressing used in pin lamination type hot pressing, in which guide pins are inserted into through holes provided in an object to be pressed to perform hot pressing, comprising: a cushioning material body having a plurality of through holes formed in the thickness direction for inserting the guide pins; and a covering member having an outer surface that contacts the side surfaces of the through holes, wherein the outer surface of the covering member and the side surfaces of the through holes are fixed by a fixing member.

2. The hot press cushioning material according to claim 1, wherein the covering member is a porous fluororesin member, the outer surface of which is formed with recesses and / or protrusions, and the fixing member is provided on the recesses and / or protrusions.

3. The hot press cushioning material according to claim 2, wherein the rubber material used for the fixing member is one or more selected from the group consisting of fluorine, silicone, acrylic, EPM, EPDM, hydrogenated nitrile, and butyl.

4. The hot press cushioning material according to claim 2, wherein the resin material used for the fixing member is one or more selected from the group consisting of epoxy, polyimide, polyphenylene ether, phenol, urethane, urea, melamine, unsaturated polyester, and silicone.

5. A hot press cushioning material according to any one of claims 1 to 4, wherein the front and back surfaces of the cushioning material body are provided with protective material that covers the periphery of the through-hole.

6. A method for manufacturing a multilayer substrate, comprising: overlaying the heat-press cushioning material according to any one of claims 1 to 5 on a manufacturing intermediate having a laminated structure of substrate layers, adhesive layers, and conductor layers and having a plurality of through holes formed in the thickness direction; and applying pressure and heat from the hot platens of a press machine to the manufacturing intermediate via the heat-press cushioning material, with the guide pins passing through the through holes formed in the manufacturing intermediate and the through holes formed in the heat-press cushioning material.

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