Buffering material for hot pressing

Abstract

A heat-pressing cushioning material (10) having a cushioning portion (1) in which the cushioning portion (1) is provided with a woven fabric (5) and a polyimide resin (6) attached to the surface of the fiber constituting the woven fabric (5), and contains a void inside, and the warp yarn and / or the weft yarn of the woven fabric (5) is a bulking and texturing yarn formed of glass fiber. The heat-pressing cushioning material can maintain good cushioning even when repeatedly used for high-temperature pressing of 280°C or higher.

Description

TECHNICAL FIELD

[0001] The present invention relates to a cushioning material for hot pressing. BACKGROUND

[0002] When manufacturing printed circuit boards, IC cards, liquid crystal display boards, ceramic laminated boards, and other precision machine components (hereinafter collectively referred to as "laminated boards") such as copper-clad laminated boards and flexible printed circuit boards, and multi-layer boards, press forming, hot pressing, and the like are performed.

[0003] For example, in the manufacturing of laminated boards such as printed circuit boards, in the press forming, hot pressing, and the like, as shown in FIG. 1, the following method is used: a laminated board material (pressed material) 12, which is the object of pressing, is sandwiched between heating disks 13, 13, which are heating / pressing means, and a certain pressure and heat are applied. In order to obtain a formed product with good precision, in hot pressing, it is necessary to homogenize the heat and pressure applied to the pressed material 12 over the entire surface. For this purpose, hot pressing is performed in a state in which a flat cushioning material 11 is interposed between the heating disks 13 and the pressed material 12. In addition, sometimes a mirror plate is interposed between the cushioning material 11 and the pressed material 12. Figure 7

[0004] As general characteristics required of the cushioning material 11, there are the cushioning property of absorbing the irregularities possessed by the heating disks 13 and the pressed material 12, the in-plane uniformity for homogeneously transferring the temperature and pressure from the heating disks 13 to the pressed material 12 over the entire press surface, the heat transfer property for efficiently transferring heat from the heating disks 13 to the pressed material 12, the heat resistance for withstanding the press temperature, and the like.

[0005] Patent Document 1 discloses a cushioning material 1 for hot pressing, which has a fiber-rubber composite layer, is formed of a woven fabric and rubber impregnated in the woven fabric, and has pores inside.

[0006] Here, the 5th generation mobile communication system (hereinafter referred to as "5G") has advantages such as high capacity (eMBB; enhanced Mobile Broadband), high reliability / low latency communication (URLLC; Ultra-Reliable and Low Latency Communications), and massive machine communication (mMTC; massive Machine Type Communication), and thus is attracting attention. However, for the true commercialization of 5G, high frequency countermeasures for printed circuit boards and the like are urgently needed. That is, with the high frequency of communication based on 5G, there is a demand for printed circuit boards that have excellent semiconductor and electrical characteristics and have small transmission loss.

[0007] ​As the existing substrate material, a glass epoxy resin (FR-4), a polyphenylene ether (PPE) resin, a polyimide (PI) resin, and the like are mainstream, but a fluorine (PTFE) resin, a liquid crystal polymer (LCP), and the like, which have a small transmission loss, are attracting attention.

[0008] Prior art documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2008 / 065969 SUMMARY

[0011] Problems to be solved by the invention

[0012] The existing forming temperature at the time of press forming of a glass epoxy resin, a polyphenylene ether, and the like, is about 250°C or lower. However, when a fluorine, a liquid crystal polymer, and the like are used, press forming needs to be performed at a higher temperature (280°C to 400°C). Therefore, for a press cushioning material, characteristics at a higher temperature than the existing are required to be excellent.

[0013] However, in the press cushioning material disclosed in Patent Document 1, rubber is impregnated, and therefore, at the time of press at a high temperature of 280°C or higher, deterioration, a decrease in properties such as cushioning, or interlayer peeling, and the like, occur at an initial stage.

[0014] An object of the present application is to provide a hot press cushioning material that can maintain good cushioning even when repeatedly used at a high temperature of 280°C or higher.

[0015] Means for solving the problems

[0016] The present inventors and the like researched a material that has both cushioning and heat resistance instead of rubber in order to achieve the above object. The present inventors and the like focused on a resin such as a polyimide resin in the process of selecting a material having excellent heat resistance. However, the hardness of polyimide is 100 in the A hardness scale and 78 in the D hardness scale, and is a material that is harder than a fluorine rubber (A hardness: 50 to 95, D hardness: 20 to 40), and therefore, it was expected that it is not suitable as a cushioning material. The present inventors and the like researched variously in order to use such a hard polyimide resin as a material that constitutes a part of a cushioning material, and as a result, unexpectedly determined that when the polyimide resin is attached to the surface of a fiber that constitutes a woven fabric that uses bulking and texturing yarns formed of glass fibers in warp and / or weft, good cushioning can be imparted, and thus the present application was completed.

[0017] Based on such insight, the gist of the present invention is "a cushioning material for hot pressing having a cushioning portion, the cushioning portion having a woven fabric, and a polyimide resin attached to the surface of a fiber constituting the woven fabric, and containing a void inside, and the warp yarn and / or the weft yarn of the woven fabric being a bulking textured yarn formed of glass fiber."

[0018] Effects of the Invention

[0019] By the present invention, it is possible to provide a cushioning material for hot pressing that can maintain good cushioning even when repeatedly used for high-temperature pressing of 280°C or higher. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A diagram showing the cushioning material for hot pressing 10 of the present embodiment.

[0021] Figure 2 A diagram showing a bulking textured yarn (bulky yarn) la formed of glass fiber.

[0022] Figure 3 A diagram showing a general glass fiber yarn (single yarn or cabled yarn) lb.

[0023] Figure 4 A diagram showing the cushioning material for hot pressing 10a of another embodiment.

[0024] Figure 5 A diagram showing the cushioning material for hot pressing 10b of another embodiment.

[0025] Figure 6 A diagram showing the cushioning material for hot pressing 10c of another embodiment.

[0026] Figure 7 A diagram showing a press molding device such as a printed circuit board. DETAILED DESCRIPTION

[0027] Hereinafter, the cushioning material for hot pressing of the present invention will be described in detail with reference to the drawings.

[0028] [Cushioning material for hot pressing 10 of the present embodiment]

[0029] Figure 1 The cushioning material for hot pressing 10 of the present embodiment is shown. As shown in Figure 1 the present embodiment has at least a cushioning portion 1. The cushioning portion 1 is a sheet-shaped cushioning member (cushioning sheet) composed of a woven fabric 5 and a polyimide resin 6 attached to the surface of a fiber constituting the woven fabric 5. The inside of the cushioning portion 1 contains a void 7. In addition, in the cushioning portion 1, the warp yarn 5a and / or the weft yarn 5b of the woven fabric 5 is a bulking textured yarn formed of glass fiber. Figure 1In this embodiment, the warp yarn 5a is a glass fiber twisted yarn, and the weft yarn 5b is a glass fiber texturized yarn.

[0030] The heat-pressing cushioning material 10 of this embodiment has the cushioning portion 1, and thus can maintain good cushioning even when repeatedly used for high-temperature pressing of 280°C or higher.

[0031] Among the fibers constituting the woven fabric 5 of the cushioning portion 1, a texturized yarn formed of glass fiber is used. In the texturized yarn formed of glass fiber, the short fibers constituting the glass yarn are not in a parallel state, but are stretched and concentrated in a state of being entangled and disordered, occupying a large area. In other words, the texturized yarn has a swelling similar to that of wool, and thus the woven fabric using the texturized yarn is different from a general woven fabric, and contains a large number of pores inside.

[0032] The cushioning portion 1 is in the form of a sheet. If the thickness is too small, there is a concern that the cushioning will be poor, and if the thickness is too large, there is a concern that the heat transfer will be poor. Thus, the appropriate thickness of the cushioning portion 1 also depends on the use, and for example, can be set in the range of 0.5 to 5.0 mm. In addition, when the cushioning portion 1 is used in a state of being laminated in two or more layers, the total thickness can be set in the range of 0.5 to 5.0 mm.

[0033] The cushioning portion 1 is formed with polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5. The polyimide resin 6 moderately enters the pores 7 of the texturized yarn and the pores 7 of the weave marks, but does not completely block the pores 7, and thus the pores 7 remain in the cushioning portion 1. Thus, the heat-pressing cushioning material 10 of this embodiment exhibits good cushioning. Furthermore, the texturized yarn is woven in the form of a woven fabric, and thus the precision of the weight per unit area is good, and the in-plane uniformity is excellent, as compared with a nonwoven fabric. In addition, the thickness can be made smaller than that of a nonwoven fabric, and the heat transfer is also excellent.

[0034] Glass fiber has heat resistance and a small change in size due to heat, and thus the heat-pressing cushioning material using the same has good dimensional stability even when repeatedly used for high-temperature pressing of 280°C or higher. The polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5 protects the glass fiber and bonds the junctions of the fibers (in addition to the junctions of the warp and weft yarns, the junctions between the filament fibers constituting the texturized yarn are also included). Thus, the heat-pressing cushioning material 10 of this embodiment can reduce the breakage of the glass fiber when repeatedly used for heat pressing, and can suppress so-called slush overflow of the woven fabric 5, and thus can also maintain good cushioning. That is, the durability is excellent.

[0035] The polyimide resin 6 preferably has a thermal decomposition temperature (5% weight loss temperature) and a glass transition temperature that are higher than the pressing temperature (280°C or higher). For example, a polyimide resin having a thermal decomposition temperature and a glass transition temperature of 400°C or higher is preferably used.

[0036] Figure 2 A bulky yarn 1a formed of glass fibers is shown. Figure 3 A general glass fiber yarn (single yarn or twisted yarn) 1b is shown. As shown in Figure 2 The bulky yarn 1a is different from the single yarn or twisted yarn in that it is not subjected to fiber opening of the single yarn or bulking of the twisted yarn, and is a processed yarn having a bulky shape like a wool yarn. In the bulky yarn 1a, the yarn itself contains a large number of pores, and thus the resin can be moderately impregnated. As the bulked yarn, in addition to the bulky yarn, a staple yarn, a sliver yarn, or the like can be used. The staple yarn is a yarn made by spinning a cotton-like glass staple fiber into a filament shape. The sliver yarn is a yarn made by applying twisting to a bulky staple fiber (sliver) without twisting. As the woven fabric of the bulky yarn 1b using glass fibers, for example, A305, A330, A400, A415, A450, A500, T330, T540, T790, T860, T900 manufactured by Unichika Corporation, KS4010, KS4155, KS4325 manufactured by Nippon Glass Fiber Co., Ltd., or the like are commercially available.

[0037] As the woven fabric 5 of the cushioning portion 1, either one of the warp yarns 5a and the weft yarns 5b can be woven using the bulked yarn 1a, and the other can be woven using the general glass fiber yarn 1b, or both the warp yarns 5a and the weft yarns 5b can be woven using the bulked yarn 1a. When either one of the warp yarns 5a and the weft yarns 5b is woven using the bulked yarn 1a, the other can be constituted of the general glass fiber yarn (single yarn or twisted yarn) 1b. As the woven fabric 5, single weaving or double weaving is preferable. However, in the case of three or more weaving, the thickness becomes too large, the excess resin becomes large, or the heat transfer property decreases. In addition, in order to adhere to the surface of the fiber constituting the woven fabric 5, the impregnation of the polyimide resin 6 impregnated in the woven fabric 5 can sometimes become insufficient. Note that the weight per unit area of the woven fabric can be adjusted by appropriately selecting the yarn count, the fabric density, the weaving method, or the like of the yarn.

[0038] (Porosity of the cushioning portion 1)

[0039] In order to maintain good properties of the heat-pressing cushioning material 10, the cushioning portion 1 needs to have sufficient porosity 7. However, the porosity of the cushioning portion 1 is sometimes difficult to correctly grasp by a method based on cross-sectional observation or the like. The present inventors and others have conducted intensive studies on a method of evaluating the porosity of the cushioning portion 1, and found that the porosity can be estimated from the results of a test conducted in accordance with the following gist.

[0040] That is, when the thickness of the heat-pressing cushioning material 10 is set to tO, and the thickness of the heat-pressing cushioning material 10 when compressed under the following compression test conditions is set to tl, the amount of porosity per unit volume can be estimated from the calculated value of "(tO-tl)". In addition, among the components constituting the heat-pressing cushioning material 10 (the surface layer portion 2, the adhesive layer portion 3, the adhesive sheet portion 4, and the like described later, in addition to the cushioning portion 1), the majority of the porosity 7 and the portion that deforms by compression are the cushioning portion 1, and thus this "(tO-tl)" can be regarded as the amount of porosity of the cushioning portion 1. Therefore, when the thickness of the cushioning portion 1 excluding other components such as the surface layer portion 2 and the like in the heat-pressing cushioning material 10 is set to t2, the porosity Fn of the cushioning portion 1 can be estimated from the calculated value of "(tO-tl) / t2". That is, when the heat-pressing cushioning material 10 is compressed at a pressure of 10 MPa in a temperature environment of 25°C, the majority of the porosity 7 present in the cushioning portion 1 in the heat-pressing cushioning material 10 collapses, and thus this value is a value depending on the porosity, that is, it can be considered to be an approximate porosity. The thickness tO of the heat-pressing cushioning material 10 can be measured, for example, by a direct-reading thickness gauge, an electron microscope, or the like. The thickness tl of the heat-pressing cushioning material 10 when compressed under the following compression test conditions can be measured by an Instron universal material testing machine (manufactured by Instron Corporation), an Autograph precision universal testing machine (manufactured by Shimadzu Corporation), or the like having a compression function.

[0041] [Compression test conditions for porosity evaluation]

[0042] Pressing pressure: 10 MPa

[0043] Temperature: 25°C

[0044] Pressing speed: 5 mm / minute

[0045] Sample size: 2.5 cm square

[0046] The thickness t2 of the cushion portion 1 used in the hot-pressing cushioning material 10 is set to the thickness of the glass fiber forming the woven fabric 5 of which the warp yarns 5a and / or weft yarns 5b are made of bulked yarns. For the thickness t2 of the cushion portion 1, from the hot-pressing cushioning material 10, along the warp yarns 5a and weft yarns 5b of the woven fabric constituting the cushion portion 1, a sample of a square of about 2.5 cm on each side is observed under an electron microscope at a magnification of 20 to 100 times, and the cross section is observed. The distance h between a line connecting the apex 2 points on the upper edge of the cushion portion 1 at which the fibers (warp yarns 5a or weft yarns 5b) are bent along the cross section of the cushion portion 1 (the line connecting the bent points Al and A2 of the warp yarns 5a in the illustrated example) and a line connecting the apex 2 points on the lower edge (the line connecting the bent points Bl and B2 of the weft yarns 5b in the illustrated example) is measured with a measuring tool. Figure 1 The distance h is shown. Figure 1 Figure 1

[0047] Note that, for the measured value, the measurement is performed at 1 near the center of each side of the sample, and the average of a total of 4 is used. When the cushion portion 1 has a plurality of layers, the thickness of each layer is measured, and the total is used as the thickness t2 of the cushion portion 1.

[0048] Note that the hot-pressing cushioning material 10 is generally a plate-shaped square of one side of 20 cm to 250 cm. In the case of a larger hot-pressing cushioning material, the sample to be measured should be taken from a position that takes into account the deviation in the plane as much as possible. For example, in the case of a hot-pressing cushioning material whose outline inscribes a square of one side of 30 cm or more, the sample (2.5 cm square) is taken at a total of 4 positions near the middle points of straight lines intersecting the four corners and the center of the hot-pressing cushioning material 10, and the porosity is set to the average of a total of 4. In addition, in the case of a hot-pressing cushioning material whose outline inscribes a square of one side of less than 30 cm, the sample (2.5 cm square) is taken at 1 position 5 cm or more away from one end.

[0049] The lower limit of Fn thus measured is preferably 0.20. If it is set to such a range, the pre-hot-pressing cushioning material 10 can be given sufficient cushioning properties. The lower limit of Fn is more preferably 0.25. Fn need only satisfy the hot-pressing cushioning material 10 that has not been used. However, the value of Fn decreases with the number of times it is used. That is, even in the case of a hot-pressing cushioning material 10 that has been used for pressing a plurality of times, if Fn is 0.20 or more, it can maintain good cushioning properties. For example, the Fn of a hot-pressing cushioning material 10 after being subjected to pressing under conditions of 300°C and 10 MPa once is also preferably 0.20 or more.

[0050] ​​However, as shown in the examples, in the case of the heat press buffer material 10 of the present application, even if pressing is performed 100 times under the conditions of a higher temperature of 400°C and a pressure of 4 MPa, the retention rate of the cushioning property is still 79% or more. Therefore, when a used heat press buffer material 10 is obtained, even if the use conditions (pressing temperature, pressure, number of times, etc.) thereof are unknown, when Fn is 0.10 or more, it can be estimated that Fn of the heat press buffer material 10 in an unused state is 0.20 or more.

[0051] The upper limit of Fn is not limited. The larger Fn is, the more advantageous it is in terms of the cushioning property, but there is a concern that the heat transfer property will deteriorate, and therefore the upper limit of Fn is preferably set to 0.50. A more preferable upper limit is 0.45. Note that even if Fn of the unused heat press buffer material 10 is greater than 0.50, it can become 0.50 or less after the first pressing.

[0052] Note that, with regard to the above Fn, even when the heat press buffer material 10 is composed only of the cushioning portion 1, the layer other than the cushioning portion 1, such as the adhesive sheet portion 4, the surface layer portion 2, and the adhesive layer portion 3, can be managed with the same criteria. As described above, this is because almost no pores exist in the surface layer portion 2, the adhesive layer portion 3, and the adhesive sheet portion 4, and almost all of the pores present in the heat press buffer material 10 exist in the cushioning portion 1. Therefore, even when the heat press buffer material 10 includes a layer other than the cushioning portion 1, the porosity present in the entire heat press buffer material 10 becomes substantially the same as the porosity present only in the cushioning portion 1. In the present application, a layer that satisfies the conditions such as being formed of a woven fabric 5 of glass fibers of which warp yarns 5a and / or weft yarns 5b are bulking and texturing yarns, having polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5, and including pores 7 is defined as the cushioning portion 1. Therefore, the adhesive sheet portion 4, the adhesive layer portion 3, and the surface layer portion 2 are also regarded as the cushioning portion 1 when they satisfy such conditions. In other words, a layer that does not satisfy the conditions such as being formed of a woven fabric 5 of glass fibers of which warp yarns 5a and / or weft yarns 5b are bulking and texturing yarns, having polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5, and including pores 7 is not the cushioning portion 1.

[0053] [Another Embodiment of Heat Press Buffer Material]

[0054] The heat press buffer material 10 can have at least the cushioning portion 1, and can be composed only of the cushioning portion 1. The cushioning portion 1 of the heat press buffer material 10 can be one layer, or can be multiple layers.

[0055] Figure 4 Another embodiment of the heat press buffer material 10a is shown in FIG. 10. As shown in FIG. 10, the heat press buffer material 10a is composed of the cushioning portion 1, the adhesive sheet portion 4, and the surface layer portion 2. The adhesive sheet portion 4 is disposed between the cushioning portion 1 and the surface layer portion 2. The adhesive sheet portion 4 is composed of a sheet of an adhesive material. The adhesive sheet portion 4 is not necessarily composed of a sheet of an adhesive material, and can be composed of a layer of an adhesive material. The adhesive sheet portion 4 can be composed of a layer of an adhesive material that is not a sheet. Figure 4As shown, in the hot-pressing cushioning material 10a, a surface layer 2 is laminated on the surface of the cushioning portion 1 via an adhesive layer 3. The surface layer 2 is mainly provided to impart mold release properties to the preheating-pressing cushioning material. As the material of the surface layer 2, synthetic resin films, or materials with a mold release resin coated on the surface side of a fabric substrate, can be used. In particular, for resistance to high-temperature pressing, materials with low dimensional stability, no deformation, good adhesion, and good mold release properties during high-temperature use are preferred. Furthermore, the thickness of the surface layer 2 is preferably, for example, 0.1 to 0.5 mm. Additionally, as the adhesive layer 3, the same polyimide resin used in the cushioning portion 1 can be used.

[0056] Figure 5 Another embodiment of the hot-pressing cushioning material 10b is shown. For example... Figure 5 As shown, in the hot-pressing cushioning material 10b, two layers of cushioning portions 1 are stacked using adhesive sheet portions 4. Furthermore, a surface layer 2 is stacked on the upper and lower surfaces of each cushioning portion 1 using adhesive layer portions 3. The cushioning portions 1 are constructed by impregnating a glass fiber fabric with resin; therefore, although their thickness is limited, this configuration of stacking two layers of cushioning portions 1 has the advantage of further increasing the total thickness of the cushioning portions 1. Additionally, the bonding between the cushioning portions 1 can be done using only an adhesive, but in this case, the gaps in the weave of the cushioning portions 1 are filled by the adhesive, sometimes reducing the cushioning performance. Therefore, it is preferable to use adhesive sheet portions 4. It should be noted that the adhesive sheet portion 4 is, for example, a sheet-like adhesive layer formed by coating an adhesive onto a plain-woven fabric composed of ordinary glass fiber filaments 1b. As this adhesive, polyimide resin can be used, similar to the resin used in the cushioning portions 1. To prevent the fibers from cracking from the sides and the fibers from falling off, heat-resistant resin can also be applied to the sides of the manufactured hot-pressing cushioning material.

[0057] Figure 5 The example shown has two layers of buffer 1, but the hot-pressing buffer material may also have three or more layers of buffer 1.

[0058] Figure 6 Another embodiment of the hot-pressing cushioning material 10c is shown. For example... Figure 6As shown, the thermal press buffer material 10c has the heat insulating layer portion 8 laminated between the 2 layers of the buffer portions 1 by the adhesive sheet portion 4. The heat insulating layer portion 8 can maintain sufficient heat resistance and durability at the use temperature (e.g., 280°C or higher) of the thermal press buffer material. In addition, the surface layer portion 2 is laminated on the upper and lower surfaces of each buffer portion 1 by the adhesive layer portion 3. Thereby, the heat insulating property of the thermal press buffer material 10c can be improved. The heat insulating layer portion 8 is, for example, a sheet in which an inorganic binder is impregnated in a base material. As the base material, for example, a woven fabric or a nonwoven fabric formed of inorganic fibers can be used. As the inorganic fibers, for example, glass fibers, ceramic fibers, alumina fibers, silica fibers, and the like can be given. As the inorganic binder, for example, alkylsilane, silica, ceramic, and the like can be given.

[0059] Figure 6 In the example shown, an example having 2 layers of the buffer portions 1 and 1 layer of the heat insulating layer portion 8 is shown, but the thermal press buffer material can have 3 or more layers of the buffer portions 1. In addition, the heat insulating layer portion 8 can be formed by laminating a plurality of heat insulating layer portions 8 by the adhesive layer portion 3 or the adhesive sheet portion 4. The thickness of the heat insulating layer portion 8 can be set in the range of 0.8 to 15 mm, for example, depending on the required heat insulating property. Note that from the viewpoint of durability and manufacturability, it is sometimes disadvantageous to be formed of a thick heat insulating layer, and therefore in the case of a thick heat insulating layer portion 8, it is preferable to use one in which a relatively thin (e.g., about 1.0 mm) heat insulating layer is laminated 2 or more layers by the adhesive layer portion 3 or the adhesive sheet portion 4. At this time, the total thickness can be set in the range of 0.8 to 15 mm.

[0060] Note that when the heat insulating layer portion 8 contains pores, the same as the buffer portion 1, the thermal press buffer material assumes the cushioning property. That is, the heat insulating layer portion 8 has sufficient heat resistance and durability at the use temperature (e.g., 280°C or higher), and therefore the same as the buffer portion 1, sufficient cushioning property can be maintained even when repeatedly used for high-temperature pressing. Also, in the thermal press buffer material having the heat insulating layer portion 8 containing such pores, when the thickness of the thermal press buffer material 10 is set to t0, and the thickness when the thermal press buffer material 10 is compressed under the pressing test conditions described below is set to t1, (t0-t1) can be regarded as the total pore amount of the buffer portion 1 and the heat insulating layer portion 8. Also, when the total thickness of the buffer portion 1 and the heat insulating layer portion 8 is set to t2', the total porosity Fn' of the buffer portion 1 and the heat insulating layer portion 8 can be estimated from the calculated value of "(t0-t1) / t2'". When the heat insulating layer portion 8 does not contain pores, the same as the example described above, "(t0-t1)" can be regarded as the pore amount of the buffer portion 1, and therefore for the thermal press buffer material having such a heat insulating layer portion 8, Fn can be evaluated by the above.

[0061] [Manufacturing method of the thermal press buffer material of the embodiment]

[0062] First, a woven fabric of bulking and texturing yarns (bulking glass yarns) formed of glass fibers is prepared. The weaving method of the woven fabric is not limited, and for example, plain weave, twill weave, or other known weaves can be used.

[0063] Next, polyimide resin is attached to at least the surface of the fibers constituting the woven fabric. For example, a polyimide resin varnish having a concentration of 2 to 10% is applied to the woven fabric, and dried at a temperature of 150 to 250°C for 3 to 10 minutes, whereby the polyimide resin is attached to the surface of the fibers constituting the woven fabric, and thus a cushioning portion (cushioning sheet) 1 can be produced. At this time, the amount of resin attached can be, for example, 20 to 200 g / m2. 2 The amount of resin attached can be adjusted by rolling using a resin roll, a rubber roll, a metal roll, or the like, at a pressure of 0.1 to 5 kg / cm2. 2

[0064] For applying the polyimide resin varnish, it is preferable to use one adjusted so as to have a solid content concentration of 2 to 10% and a viscosity of about 20 to 100 mPa-s by dilution with a solvent NMP (N-methyl-2-pyrrolidone). Alternatively, a polyamic acid solution, which is a precursor of polyimide, can be used.

[0065] In the woven fabric obtained in this way, in which the polyimide resin is attached to the surface of the fibers, the fibers are in a state of being fixed and covered, and thus the shape and the pores of the bulking and texturing yarns (bulking yarns) can be maintained even in use at high temperatures. Therefore, good cushioning properties can be ensured even when repeatedly used.

[0066] When the heat-pressing cushioning material has a surface layer portion (surface layer sheet) 2, for example, a surface layer portion 2 obtained by applying polyimide resin to one side of a sheet as a base material, drying it, and then applying polyimide resin to the other side and drying it can be used.

[0067] When the heat-pressing cushioning material has a sheet-adhering portion (sheet-adhering sheet) 4, for example, a sheet-adhering portion 4 obtained by applying resin to both sides of a sheet as a base material and drying it can be used. The resin is, for example, polyimide resin. The sheet-adhering portion 4 can also be produced by applying a polyimide resin varnish (40 to 60 μm thick) to a PET film, semi-drying it, and then peeling it from the PET film to make it into a film shape.

[0068] The cushioning portion 1 and a plurality of sheets are laminated (for example, the surface layer sheet 2, the cushioning sheet 1, the sheet-adhering sheet 4, the cushioning sheet 1, and the surface layer sheet 2 are laminated), and integrated by heat-pressing.

[0069] When the heat-pressing cushioning material has a heat-insulating layer portion 8, for example, a heat-insulating layer portion 8 obtained by preparing a glass woven fabric and attaching an alkylsilane adhesive to the woven fabric material can be used. ​

[0070] For the heat-pressing buffer material based on the present application, in the manufacture of a laminated board such as a printed circuit board, when performing press forming and heat-pressing, the same method as in the past can be used. That is, heat-pressing is performed with the heat-pressing buffer material 11 interposed between the heated platen 13 and the material to be pressed 12, whereby the heat and pressure applied to the material to be pressed 12 can be homogenized over the entire surface. Figure 7

[0071] Example 1

[0072] Hereinafter, the results of investigating various properties of the buffer materials of the production examples and comparative examples will be shown. Note that Examples 1 to 4 and Comparative Example 1 have a configuration including a surface sheet and an adhesive sheet, and Comparative Examples 2 to 14 do not include a surface sheet, an adhesive sheet, etc., and are configured only by a buffer sheet.

[0073] (Example 1)

[0074] As the woven fabric material, a double twill weave bulk glass woven fabric was prepared in which the warp yarns were made of 2 twisted glass yarns (yarn count 67.5 tex) (non-bulk processed yarn having a single fiber diameter of 5 μm and a single fiber count of 2400), and the weft yarns were made of 4 twisted glass yarns (yarn count 67.5 tex) that had been bulk processed (bulked yarn having a single fiber diameter of 5 μm and a single fiber count of 4800). In addition, as the resin material, a polyimide resin varnish (concentration 5%) having a thermal decomposition temperature of 512°C and a glass transition temperature of 400°C or higher was prepared. After the polyimide resin varnish was impregnated in the glass woven fabric, it was dried at 200°C for 5 minutes, and a buffer sheet having a polyimide resin attached at a rate of 1.7 mass% with respect to the woven fabric material was prepared.

[0075] On the other hand, as the surface sheet, a flat-woven glass woven fabric was prepared in which the polyimide resin varnish was applied to one side (the surface side) and dried, and then the polyimide resin varnish was applied to the opposite side (the adhesive layer) and dried. In addition, as the adhesive sheet, a flat-woven glass woven fabric was prepared in which the polyimide resin varnish was applied to both sides (the adhesive layers) and dried.

[0076] The obtained surface sheet, buffer sheet, adhesive sheet, buffer sheet, and surface sheet were sequentially laminated, and press forming was performed at 10 MPa x 190°C for 60 minutes of heating + 10 minutes of cooling, after which heat treatment was performed at 300°C for 5 hours, and a sample of a heat-pressing buffer material was obtained.

[0077] (Example 2)

[0078] A buffer sheet was prepared in which the resin attachment amount of Example 1 was changed to 3.4 mass%, and a sample of a heat-pressing buffer material having the same configuration as Example 1 was obtained. ​

[0079] (Example 3)

[0080] Using a cushion sheet in which the resin adhesion amount of the resin of Example 1 was changed to 8.8 mass%, a sample of a hot-pressing cushion material having the same constitution as that of Example 1 was obtained.

[0081] (Example 4)

[0082] Using a cushion sheet in which the resin adhesion amount of the resin of Example 1 was changed to 13.2 mass%, a sample of a hot-pressing cushion material having the same constitution as that of Example 1 was obtained.

[0083] (Comparative Example 1)

[0084] A cushion sheet in which 10.5 mass% of fluororubber was impregnated in the same bulk glass cloth as that of Example 1 was prepared. In addition, a sample of a hot-pressing cushion material having the same constitution as that of Example 1 was obtained, in which fluororubber varnish was attached to the surface sheet and the adhesive sheet instead of the polyimide resin varnish as the adhesive layer of Example 1.

[0085] (Comparative Example 2)

[0086] A polyimide resin (the same as that of Example 1) was attached to a twill weave cloth having a fabric density of 34 warps / 2.5 cm and 22 wefts / 2.5 cm, using a yarn in which 4 glass yarns (yarn count 67.5 tex) were twisted (yarn which was not bulk processed), and drying at 230°C for 5 hours, to prepare a cushion sheet having a thickness of 0.75 mm and a resin adhesion amount of 2.8 mass% relative to the mass of the base material. Three of the cushion sheets were overlaid to obtain a sample of a hot-pressing cushion material.

[0087] (Comparative Example 3),

[0088] A polyimide resin (the same as that of Example 1) was attached to a satin weave cloth having a fabric density of 45 warps / 2.5 cm and 30 wefts / 2.5 cm, using a yarn in which 4 glass yarns (yarn count 67.5 tex) were twisted (yarn which was not bulk processed), and drying at 230°C for 5 hours, to prepare a cushion sheet having a thickness of 1.10 mm and a resin adhesion amount of 3.1 mass% relative to the mass of the base material. Two of the cushion sheets were overlaid to obtain a sample of a hot-pressing cushion material.

[0089] (Comparative Example 4)

[0090] A woven fabric (thickness 2.40 mm) of 3 / 1 twill weave having a fabric density of 93 warp threads / 2.5 cm and 66 weft threads / 2.5 cm was prepared using a 2-ply poly-m-phenylene isophthamide short fiber yarn (yarn count 59.1 tex, cotton yarn count: 10 yarn count) for the warp and a 3-ply poly-m-phenylene isophthamide short fiber yarn (yarn count 59.1 tex, cotton yarn count: 10 yarn count) for the weft. A sample of the hot-pressing cushion material composed of one sheet of this cushion sheet was obtained.

[0091] (Comparative Example 5)

[0092] A poly-m-phenylene isophthamide resin (concentration 10%) was impregnated into the woven fabric of Comparative Example 4, dried at 230°C for 5 hours, and a cushion sheet having a thickness of 2.40 mm and a resin adhesion amount of 3.3 mass% relative to the mass of the base material was prepared. A sample of the hot-pressing cushion material composed of one sheet of this cushion sheet was obtained.

[0093] (Comparative Example 6)

[0094] A polyimide resin (the same as the polyimide resin of Example 1) was impregnated into the woven fabric of Comparative Example 4, dried at 230°C for 5 hours, and a cushion sheet having a thickness of 2.40 mm and a resin adhesion amount of 3.1 mass% relative to the mass of the base material was prepared. A sample of the hot-pressing cushion material composed of one sheet of this cushion sheet was obtained.

[0095] (Comparative Example 7)

[0096] A woven fabric (thickness 2.60 mm) of 4 / 1 twill weave having a fabric density of 109 warp threads / 2.5 cm and 85 weft threads / 2.5 cm was prepared using a 2-ply poly-m-phenylene isophthamide short fiber yarn (yarn count 59.1 tex, cotton yarn count: 10 yarn count) for the warp and a 3-ply poly-m-phenylene isophthamide short fiber yarn (yarn count 59.1 tex, cotton yarn count: 10 yarn count) for the weft. A sample of the hot-pressing cushion material composed of one sheet of this cushion sheet was obtained.

[0097] (Comparative Example 8)

[0098] A poly-m-phenylene isophthamide resin (concentration 10%) was impregnated into the woven fabric of Comparative Example 7, dried at 230°C for 5 hours, and a cushion sheet having a thickness of 2.60 mm and a resin adhesion amount of 3.3 mass% relative to the mass of the base material was prepared. A sample of the hot-pressing cushion material composed of one sheet of this cushion sheet was obtained.

[0099] (Comparative Example 9)

[0100] The polyimide resin (the same as the polyimide resin of Example 1) was impregnated in the woven fabric of Comparative Example 7, dried at 230°C for 5 hours, and a cushion sheet having a thickness of 2.60 mm was prepared so that the resin adhesion amount would be 3.0 mass% relative to the mass of the base material. A sample of the cushion material for hot pressing was obtained from one sheet of this cushion sheet.

[0101] (Comparative Example 10)

[0102] A woven fabric was prepared in which the warp yarns were composed of 2 poly-p-phenylene-benzobisoxazole short fiber yarns (yarn count: 29.5 tex, cotton yarn count: 20 yarn count) and the weft yarns were composed of 2 poly-p-phenylene-benzobisoxazole short fiber yarns (yarn count: 29.5 tex, cotton yarn count: 20 yarn count), and the fabric density was set to 68 warp yarns / 2.5 cm and 60 weft yarns / 2.5 cm. A cushion sheet having a thickness of 0.52 mm was prepared. A sample of the cushion material for hot pressing was obtained by stacking 4 of these cushion sheets.

[0103] (Comparative Example 11)

[0104] The polyimide resin (the same as the polyimide resin of Example 1) was impregnated in the woven fabric of Comparative Example 10, dried at 230°C for 5 hours, and a cushion sheet was prepared so that the resin adhesion amount would be 3.3 mass% relative to the mass of the base material. A sample of the cushion material for hot pressing was obtained by stacking 4 of these cushion sheets.

[0105] (Comparative Example 12)

[0106] A cushion sheet was prepared from a nonwoven fabric having a thickness of 4.5 mm formed by needle punching a web of 3 layers of poly-p-phenylene-benzobisoxazole fiber (fiber: Zylon manufactured by Toyobo Co., Ltd.) and a base fabric of 2 layers of glass cloth cold yarn. A sample of the cushion material for hot pressing was obtained from one sheet of this cushion sheet. Note that the weight per unit area was set to 1350 g / m 2 (the web: 1180 g / m 2 , the base fabric: 170 g / m 2 ).

[0107] (Comparative Example 13)

[0108] A cushion sheet was prepared from a nonwoven fabric having a thickness of 5.0 mm formed by needle punching a web of SUS fiber. A sample of the cushion material for hot pressing was obtained from one sheet of this cushion sheet.

[0109] (Comparative Example 14)

[0110] The polyimide resin (the same as that of Example 1) was impregnated in the nonwoven fabric of Comparative Example 13, dried at 230°C for 5 hours, and a buffer sheet having a thickness of 5.0 mm and a resin adhesion amount of 3.4 mass% relative to the mass of the base material was prepared. A sample of a heat-pressing buffer material composed of one sheet of this buffer sheet was obtained.

[0111] The base materials of the various buffer sheets are shown in Table 1. The conditions of the various buffer sheets are shown in Table 2.

[0112] [Table 1]

[0113] Table 1

[0114]

[0115] *1: 1 tex 1000 m weight of 1 g yarn

[0116] *2: 1 yarn count 1 pound (453 g) weight of 840 yards (768 m) yarn

[0117] *3: Number of times per 1 m

[0118] [Table 2]

[0119] Table 2

[0120]

[0121] The various heat-pressing buffer materials were subjected to a press durability test in accordance with the following contents, and the changes in thickness and cushioning before and after the test were measured. The results are shown in Tables 3 to 8.

[0122] [Press durability test conditions]

[0123] Pressing pressure: 4.0 MPa

[0124] Temperature: 400°C, 300°C, 280°C

[0125] Heating time: 70 minutes (ramp from 25°C to the specified temperature over 30 minutes, and maintain for 40 minutes)

[0126] Cooling time: 30 minutes (water cooling)

[0127] Open time: 1 minute

[0128] Sample size: 200 mm square

[0129] Press: Compact Press MHPC-VF-450-450-1-80 (manufactured by Nippon Steel & Sumikin Stainless Steel Co., Ltd.)

[0130] (Evaluation method for thickness)

[0131] For each sample, the thickness before pressing and the thickness (mm) after pressing for 1 time, 10 times, 50 times, and 100 times were measured using a direct-reading thickness meter.

[0132] (Evaluation method of cushioning)

[0133] For each sample, the cushioning before pressing and after pressing for 1 time, 10 times, 50 times, and 100 times was evaluated. For the cushioning, the following pressure test was performed for each sample, and the compression cushioning was calculated from the difference (μm) between the thickness before pressure and the thickness under pressure.

[0134] Pressure pressure: 4.0 MPa

[0135] Pressure temperature: 400°C, 300°C, 280°C

[0136] Preheating: 0.05 kgf / cm 2 x 2 minutes

[0137] Pressure speed: 1 mm / minute

[0138] Sample size:

[0139] Sample collection position: position 1 at 5 cm or more from one end of the sample for durability test

[0140] Test device: Instron universal material testing machine 5565 type (manufactured by Instron Japan Company Limited)

[0141] [Porosity evaluation pressing test conditions]

[0142] For each sample, the porosity Fn of the cushioning portion before pressing and after pressing for 1 time, 10 times, 50 times, and 100 times was calculated. Note that in this comparative experiment, the size of the sample for durability test was as small as 200 mm square, and therefore the sample collection position for porosity Fn evaluation was only position 1 at 5 cm or more from one end.

[0143] Pressure pressure: 10 MPa

[0144] Temperature: 25°C

[0145] Pressure speed: 5 mm / minute

[0146] Sample size: 25 mm square

[0147] Sample collection position: position 1 at 5 cm or more from one end of the sample for durability test

[0148] Test device: Autograph precision universal testing machine AG-X (manufactured by Shimadzu Corporation)

[0149] (Porosity evaluation method)

[0150] For Embodiments 1 to 4 and Comparative Example 1 of the woven fabric using the bulk glass as the buffer sheet, the thickness t0 of the sample before compression, the thickness t2 of the buffer portion 1, and the thickness t1 at the time of compression under the above conditions were measured. Note that for the thickness t0 of the sample before compression, one point near the center of the sample was measured using a direct-reading thickness gauge, and for the thickness t1 at the time of compression, the distance between the lines connecting the two points on the top of the buffer sheet at the vertices of the fiber (warp or weft) located along the cross section of the buffer sheet was measured using an Autograph precision universal testing machine based on the porosity evaluation compression test conditions. In addition, for the thickness t2 of the buffer portion 1, the cross section of the sample was observed at a magnification of 50 times using an electron microscope (Keyence VHX series), and the distance between the lines connecting the two points at the vertices located on the lower side was measured using a measuring tool. When the buffer sheet had multiple layers, the total thickness was set as the thickness t2 of the buffer portion 1. For the thickness t2, the average of the four points (total of four points) on each side of the sample was taken.

[0151] [Table 3]

[0152] Table 3

[0153]

[0154] Test temperature: 400°C

[0155] [Table 4]

[0156] Table 4

[0157]

[0158] Test temperature: 400°C

[0159] [Table 5]

[0160] Table 5

[0161]

[0162] Test temperature: 300°C

[0163] [Table 6]

[0164] Table 6

[0165]

[0166] Test temperature: 300°C

[0167] [Table 7]

[0168] Table 7

[0169]

[0170] Test temperature: 280°C

[0171] [Table 8]

[0172] Table 8

[0173]

[0174] Test temperature: 280°C

[0175] As shown in Tables 2 to 8, in Examples 1 to 4 satisfying the conditions of the present application, good cushioning properties were exhibited at any of the test temperatures. That is, Examples 1 to 4 maintained high porosity even in 100 times of pressing at any of the test temperatures, and had good durability and cushioning properties. On the other hand, in Comparative Examples 1 to 14, the thickness and the cushioning properties were extremely reduced even in one test. In particular, in the test at 400°C, the fluororubber carbonized in Comparative Example 1, and the poly-m-phenylene isophthamide fibers also carbonized and deteriorated in Comparative Examples 4 to 9, and did not have sufficient heat resistance. In addition, in Comparative Examples 13 and 14, the thickness and the cushioning properties were significantly reduced in the durability test, and thus stable cushioning properties could not be obtained in repeated use.

[0176] Note that the meanings of A to G in "Evaluation" in Tables 3 to 8 are as described below.

[0177] A Good

[0178] B The cushioning properties were reduced in one pressing.

[0179] C The rubber carbonized. In addition, the surface layer peeled, and the shape could not be maintained.

[0180] D The thickness and the cushioning properties were significantly reduced in one pressing.

[0181] E Carbonization deteriorated in one pressing.

[0182] F Cracks were generated in 10 times of pressing. In addition, the thickness and the cushioning properties were significantly reduced.

[0183] G The thickness and the cushioning properties were significantly reduced.

[0184] H Cracks were generated in 50 times of pressing. The thickness and the cushioning properties were significantly reduced.

[0185] Industrial Applicability

[0186] By the present application, it is possible to provide a cushioning material for hot pressing which can maintain good cushioning properties even when repeatedly used in high-temperature pressing at 280°C or higher.

[0187] Explanation of Reference Numerals

[0188] 1 Cushioning portion

[0189] 2 surface layer portion

[0190] 3 adhesive layer portion

[0191] 4 adhesive sheet portion

[0192] 5 woven fabric

[0193] 5a warp yarn

[0194] 5b weft yarn

[0195] 6 polyimide resin

[0196] 7 void

[0197] 11 cushioning material

[0198] 12 pressed material

[0199] 13, 13 heating disc

[0200] 14 mirror panel

Claims

1. A cushioning material for hot pressing, having a cushioning portion, the cushioning portion comprising a woven fabric, and a polyimide resin adhered to the surface of a fiber constituting the woven fabric, the cushioning portion not containing rubber and containing a void inside, the warp yarn and / or weft yarn of the woven fabric being bulking deformed yarn formed of glass fiber, and the glass transition temperature of the polyimide resin being 280°C or higher.

2. The cushioning material for hot pressing according to claim 1, wherein Fn calculated according to the following (1) is 0.20 or higher when the thickness of the cushioning material for hot pressing is set to tO, the thickness of the cushioning material for hot pressing when compressed under conditions of 25°C and 10.0 MPa is set to tl, and the thickness of the cushioning portion is set to t2, Fn = (tO - tl) / t2 (1).

3. The cushioning material for hot pressing according to claim 2, wherein Fn calculated according to the (1) is also 0.20 or higher after pressing once under conditions of 4.0 MPa of pressure, temperature increase from 25°C to 300°C over 30 minutes, maintaining the state for 40 minutes, and then water cooling over 30 minutes. ​ ​

Images