Cushioning material for hot pressing

Abstract

A cushioning material (10) for hot pressing, which is provided with a cushioning part (1) that is provided with a woven fabric (5) and a polyimide resin (6) that adheres to the surfaces of fibers constituting the woven fabric (5) and that contains pores therein, and the warp yarns and / or weft yarns of the woven fabric (5) are bulked textured yarns comprising glass fibers. The cushioning material for hot pressing can maintain good cushioning properties even when repeatedly used for high-temperature pressing at 280 DEG C or higher.

Description

[0001] This case is a divisional application of the application with the application date of June 2, 2021, application number 202180040038.X, and invention name "Buffering Material for Hot Pressing". Technical Field

[0002] The invention relates to a cushioning material for hot pressing. Background Art

[0003] Press forming and thermal compression bonding are performed when manufacturing printed circuit boards such as copper-clad laminates, flexible printed circuit boards, and multilayer boards, IC cards, liquid crystal display panels, and precision equipment components such as ceramic laminates (hereinafter collectively referred to as "laminates").

[0004] For example, in the manufacture of laminated boards such as printed circuit boards, during press forming, thermal compression bonding and other processes, Figure 7 As shown, the following method is used: a laminated plate material (pressed material) 12, which is the object to be pressed, is clamped between heating plates 13, 13, which serve as a heating / pressing means, and a certain amount of pressure and heat are applied. In order to obtain a molded product with good precision, it is necessary to uniformly apply heat and pressure to the pressed material 12 over the entire surface during hot pressing. For this purpose, hot pressing is performed with a flat-plate cushioning material 11 inserted between the heating plates 13 and the pressed material 12. In addition, a mirror plate is sometimes inserted between the cushioning material 11 and the pressed material 12.

[0005] Common properties required of the buffer material 11 include buffering properties for absorbing the unevenness of the heating plate 13 and the pressed material 12, in-plane uniformity for uniformly transferring temperature and pressure from the heating plate 13 to the pressed material 12 over the entire pressing surface, heat transfer properties for efficiently transferring heat from the heating plate 13 to the pressed material 12, and heat resistance for withstanding the pressing temperature.

[0006] Patent Document 1 discloses a hot press cushioning material 1 including a fiber-rubber composite material layer, which is formed of a woven fabric and rubber impregnated in the woven fabric and has pores inside.

[0007] The fifth-generation mobile communication system (hereinafter referred to as "5G") is attracting much attention due to its advantages, including high-speed and high-capacity (eMBB; enhanced Mobile Broadband), ultra-reliable and low-latency communications (URLLC; massive Machine Type Communication), and mMTC (massive Machine Type Communication). However, for the full commercialization of 5G, high-frequency support for printed circuit boards and other components is a top priority. Specifically, with the increasing frequency of communications introduced by 5G, communication base stations and various terminals require printed circuit boards with excellent semiconductor and electrical properties and low transmission loss.

[0008] As existing substrate materials, glass epoxy resin (FR-4), polyphenylene ether (PPE) resin, polyimide (PI) resin, etc. are mainstream, but fluorine (PTFE) resin and liquid crystal polymer (LCP) with low transmission loss are attracting attention.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: International Publication No. 2008 / 065969 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] Conventional press molding of substrates such as glass epoxy and polyphenylene ether is performed at temperatures below approximately 250°C. However, when using materials such as fluorine and liquid crystal polymers, press molding requires higher temperatures (280°C to 400°C). Therefore, press cushioning materials must exhibit superior properties even at higher temperatures than currently possible.

[0014] However, the press cushioning material disclosed in Patent Document 1 is impregnated with rubber and therefore deteriorates in the initial stage when used for presses at high temperatures of 280° C. or higher, causing a decrease in physical properties such as cushioning properties and interlayer delamination.

[0015] An object of the present invention is to provide a hot press cushioning material that can maintain excellent cushioning properties even when repeatedly used for high-temperature pressing at 280°C or higher.

[0016] Solutions for solving problems

[0017] In order to achieve the above-mentioned purpose, the present inventors have studied materials that can replace rubber and have both cushioning properties and heat resistance. In the process of selecting materials with excellent heat resistance, the present inventors have focused on resins such as polyimide resins. However, the hardness of polyimide is 100 in durometer A and 78 in durometer D, which is a material harder than fluororubber (durometer A hardness: 50-95, durometer D hardness: 20-40), so it is not expected to be suitable as a cushioning material. The present inventors have conducted various studies to use such a hard polyimide resin as a material constituting a part of a cushioning material. As a result, they unexpectedly determined that when polyimide resin is attached to the surface of fibers constituting a woven fabric using expanded textured yarns formed of glass fibers in the warp and / or weft yarns, good cushioning properties can be imparted, thereby completing the present invention.

[0018] Based on this understanding, the main purpose of the present invention is "a hot press cushioning material having a cushioning portion, the cushioning portion comprising a woven fabric and a polyimide resin attached to the surface of fibers constituting the woven fabric, and containing pores inside, wherein the warp yarn and / or weft yarn of the woven fabric is a bulked and deformed yarn formed of glass fiber."

[0019] Effects of the Invention

[0020] According to the present invention, a hot press cushioning material can be provided which can maintain excellent cushioning properties even when repeatedly used for high-temperature pressing at 280°C or higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing a hot press cushioning material 10 according to this embodiment.

[0022] Figure 2 FIG. 1 is a diagram showing a bulky yarn 1a formed of glass fiber.

[0023] Figure 3 1b is a diagram showing a typical glass fiber yarn (single yarn or twisted yarn).

[0024] Figure 4 This is a diagram showing a hot press cushioning material 10a according to another embodiment.

[0025] Figure 5 This is a diagram showing a hot press cushioning material 10b according to another embodiment.

[0026] Figure 6 This is a diagram showing a hot press cushioning material 10c according to another embodiment.

[0027] Figure 7 This figure shows a press-forming device for a printed circuit board or the like. DETAILED DESCRIPTION

[0028] Hereinafter, the hot press cushioning material of the present invention will be described in detail with reference to the accompanying drawings.

[0029] [Hot Press Cushioning Material 10 of the Present Embodiment]

[0030] Figure 1 FIG. 1 shows a heat press cushioning material 10 according to this embodiment. Figure 1 As shown, the hot press cushioning material 10 of this embodiment includes at least a cushioning portion 1. The cushioning portion 1 is a sheet-shaped cushioning member (cushion sheet) composed of a woven fabric 5 and a polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5. The cushioning portion 1 includes pores 7. Furthermore, in the cushioning portion 1, the warp yarns 5a and / or the weft yarns 5b of the woven fabric 5 are bulked, textured yarns made of glass fibers. Figure 1 In the drawing, the warp yarn 5a is a twisted yarn of glass fiber, and the weft yarn 5b is a bulked and textured yarn of glass fiber.

[0031] Since the hot press cushioning material 10 of the present embodiment includes such a cushioning portion 1 , it can maintain good cushioning properties even when repeatedly used in high-temperature pressing at 280° C. or higher.

[0032] The fibers that make up the fabric 5 of the cushioning portion 1 are textured yarns made of glass fibers. In textured yarns, the short fibers are not parallel to each other but rather entangled, tangled, and stretched, resulting in a large surface area. In other words, textured yarns exhibit a wool-like expansion. Therefore, unlike conventional fabrics, woven fabrics using textured yarns contain numerous pores.

[0033] The buffer portion 1 is a sheet-like structure. If its thickness is too thin, there is a concern that the cushioning properties may be poor, while if it is too thick, there is a concern that the heat transfer may be poor. Therefore, the appropriate thickness of the buffer portion 1 depends on the intended use; for example, it can be set within the range of 0.5 to 5.0 mm. Furthermore, when two or more layers of the buffer portion 1 are stacked, the total thickness can be set within the range of 0.5 to 5.0 mm.

[0034] The buffer portion 1 is formed by polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5. The polyimide resin 6 moderately penetrates the pores 7 of the bulked yarn and the pores 7 of the weave marks, but does not completely block the pores 7, leaving pores 7 remaining in the buffer portion 1. Consequently, the hot press cushioning material 10 of this embodiment exhibits excellent cushioning properties. Furthermore, the bulked yarn is woven into a woven fabric, resulting in better weight accuracy and superior in-plane uniformity compared to nonwoven fabrics. Furthermore, the woven fabric form allows for a thinner thickness than nonwoven fabrics, resulting in superior heat transfer properties.

[0035] Glass fiber is heat-resistant and exhibits minimal dimensional change due to heat. Therefore, hot-press cushioning materials using glass fiber exhibit excellent dimensional stability even when repeatedly pressed at temperatures exceeding 280°C. The polyimide resin 6 adhered to the surfaces of the fibers that comprise the woven fabric 5 protects the glass fiber and bonds the fiber junctions (not only between the warp and weft yarns, but also between the filaments that comprise the bulked yarn). Therefore, the hot-press cushioning material 10 of this embodiment can reduce breakage of the glass fiber during repeated hot-pressing, suppressing so-called sizing of the woven fabric 5, and thus maintaining excellent cushioning properties. In other words, it exhibits excellent durability.

[0036] The polyimide resin 6 preferably has a thermal decomposition temperature (5% weight loss temperature) and a glass transition temperature 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.

[0037] Figure 2 A bulky yarn 1a formed of glass fibers is shown. Figure 3 Figure 1 shows a typical glass fiber yarn (single yarn or twisted yarn) 1b. Figure 2 As shown, the bulked yarn 1a is different from single yarn or twisted yarn. It does not undergo the fiber opening of single yarn or the expansion of twisted yarn. It is a processed yarn with expansion similar to wool. In the bulked yarn 1a, the yarn itself contains a large number of pores, so it can be moderately impregnated with resin. As expanded and textured yarn, in addition to bulked yarn, staple yarn, sliver yarn, etc. can be used. Staple yarn is made by weaving cotton-like short glass fibers into filaments. Sliver yarn is a yarn made by twisting untwisted bulky short fibers (sliver). As woven fabrics using bulked yarn 1b of glass fiber, for example, A305, A330, A400, A415, A450, A500, T330, T540, T790, T860, and T900 manufactured by Unicharm Co., Ltd. and KS4010, KS4155, and KS4325 manufactured by Nitto Bo Co., Ltd. are commercially available.

[0038] The woven fabric 5 serving as the buffer portion 1 can be woven using a bulked yarn 1a for either the warp yarn 5a or the weft yarn 5b and a conventional glass fiber yarn 1b for the other, or both the warp yarn 5a and the weft yarn 5b can be woven using a bulked yarn 1a. When a bulked yarn 1a is used for either the warp yarn 5a or the weft yarn 5b, the other can be made of conventional glass fiber yarn (single yarn or twisted yarn) 1b. The woven fabric 5 is preferably single-woven or double-woven. However, if there are more than three weaves, the fabric will become too thick, the overflow will become larger, or the heat transfer will decrease. In addition, in order to adhere to the surface of the fibers constituting the woven fabric 5, the penetration of the polyimide resin 6 impregnated in the woven fabric 5 may sometimes become insufficient. It should be noted that the unit area weight accuracy and porosity of the woven fabric can be adjusted by appropriately selecting the yarn weave count, fabric density, weaving method, etc.

[0039] (Porosity of Buffer Section 1)

[0040] To maintain the favorable properties of the hot press cushioning material 10, the cushioning portion 1 must have sufficient pores 7. However, the porosity of the cushioning portion 1 is sometimes difficult to accurately determine using methods such as cross-sectional observation. The present inventors have conducted extensive research on methods for evaluating the porosity of the cushioning portion 1 and have discovered that it can be estimated based on the results of experiments conducted using the following principles.

[0041] Specifically, assuming the thickness of the hot press cushioning material 10 is t0 and the thickness of the hot press cushioning material 10 when compressed under the following press test conditions is t1, the porosity per unit volume can be estimated from the calculated value of "(t0 - t1)." Furthermore, since the components constituting the hot press cushioning material 10 (excluding the cushioning portion 1, the surface layer portion 2, the adhesive layer portion 3, the adhesive sheet portion 4, etc., described later) contain the pores 7 and are the majority subject to compression deformation, the "(t0 - t1)" can be considered the porosity of the cushioning portion 1. Therefore, assuming the thickness of the cushioning portion 1 in the hot press cushioning material 10, excluding other components such as the surface layer portion 2, is t2, the porosity Fn of the cushioning portion 1 can be estimated from the calculated value of "(t0 - t1) / t2." That is, when the hot pressing buffer material 10 is compressed at a temperature of 25°C and a pressure of 10 MPa, most of the pores 7 present in the buffer portion 1 in the hot pressing buffer material 10 will collapse, so this value depends on the porosity, that is, it can be considered as an approximate porosity. The thickness t0 of the hot pressing buffer material 10 can be measured, for example, by a direct-reading thickness gauge, an electron microscope, etc. The thickness t1 when the hot pressing buffer material 10 is compressed according to the following compression test conditions can be measured by a testing machine with a compression function, such as an Instron universal material testing machine (manufactured by Instron Corporation) or an Autograph precision universal testing machine (manufactured by Shimadzu Corporation).

[0042] [Porosity evaluation compression test conditions]

[0043] Pressurization pressure: 10MPa

[0044] Temperature: 25℃

[0045] Pressurization speed: 5mm / min

[0046] Sample size: 2.5cm square

[0047] The thickness t2 of the buffer portion 1 used in the hot press buffer material 10 is set to the thickness of the woven fabric 5 formed of glass fibers composed of bulked and textured yarns constituting the warp yarns 5a and / or the weft yarns 5b. The thickness t2 of the buffer portion 1 is determined by observing the cross section of a sample collected from the hot press buffer material 10 along the warp yarns 5a and weft yarns 5b of the woven fabric constituting the buffer portion 1 at 20 to 100 times magnification using an electron microscope, and measuring the thickness of a line connecting two vertices of the upper side of the buffer portion 1 located along the fibers (warp yarns 5a or weft yarns 5b) bent along the cross section of the buffer portion 1 using a measuring tool. Figure 1 In the example shown, the line connecting the bending points A1 and A2 of the warp yarn 5a) and the line connecting the two vertices located on the lower side ( Figure 1 In the example shown, the distance ( Figure 1 h) shown.

[0048] The measurement values ​​were taken at one point near the center of each side of the sample, and the average value of the four points was used. When the buffer portion 1 has multiple layers, the thickness of each layer was measured, and the total was taken as the thickness t2 of the buffer portion 1.

[0049] It should be noted that the hot press cushioning material 10 is usually in the shape of a square plate with a side of 20 cm to 250 cm. In the case of a larger hot press cushioning material, the measurement sample should be collected from a position that takes into account the deviation within the surface as much as possible. For example, in the case of a hot press cushioning material with a side length of a square inscribed in its outline of more than 30 cm, the collection position of the measurement sample (2.5 cm square) is set to a total of 4 places near the midpoint of the straight line intersecting the 4 corners of the hot press cushioning material 10 with the center, and the porosity is set to the average value of the total 4 places. In addition, in the case of a hot press cushioning material with a side length of a square inscribed in its outline of less than 30 cm, the collection position of the measurement sample (2.5 cm square) is set to 1 position more than 5 cm away from one end.

[0050] The lower limit of Fn measured in this way is preferably set to 0.20. If it is set to such a range, sufficient cushioning properties can be given to the pre-heat pressing cushioning material 10. The lower limit of Fn is more preferably set to 0.25. Fn at least satisfies the unused heat pressing cushioning material 10. However, the value of Fn decreases with the number of times it is used. That is, even if it is a heat pressing cushioning material 10 that is used for pressing multiple times, if its Fn is 0.20 or more, good cushioning properties can be maintained. For example, the Fn of the heat pressing cushioning material 10 after one pressing under the conditions of 300°C and 10 MPa is also preferably 0.20 or more.

[0051] However, as shown in the Examples, the hot press cushioning material 10 of the present invention maintains a cushioning property retention rate of 79% or higher even after 100 cycles of pressing at a relatively high temperature of 400°C and 4 MPa. Therefore, even if the usage conditions (pressing temperature, pressure, number of presses, etc.) are unknown when obtaining a used hot press cushioning material 10, if Fn is in the range of 0.10 or higher, it can be estimated that the Fn of the hot press cushioning material 10 in its unused state is 0.20 or higher.

[0052] There is no upper limit for Fn. A larger Fn is more advantageous in terms of cushioning properties, but there is concern about deterioration in heat transfer properties, so the upper limit of Fn is preferably set to 0.50. A more preferred upper limit is 0.45. It should be noted that even if the Fn of the unused hot press cushioning material 10 is greater than 0.50, it can be reduced to 0.50 or less after the first pressing.

[0053] It should be noted that, even when the hot press cushioning material 10 consists solely of the cushioning portion 1, layers other than the cushioning portion 1, such as the adhesive sheet portion 4 and the surface portion 2, which is included on the surface via the adhesive layer portion 3, can be managed using the same criteria. As described above, this is because the surface portion 2, adhesive layer portion 3, and adhesive sheet portion 4 contain almost no pores, while the majority of the pores present in the hot press cushioning material 10 are present in the cushioning portion 1. Therefore, even when the hot press cushioning material 10 includes layers other than the cushioning portion 1, the porosity present in the entire hot press cushioning material 10 is substantially the same as the porosity present only in the cushioning portion 1. In the present invention, a layer that satisfies the following conditions: a woven fabric 5 formed of glass fibers whose warp yarns 5a and / or weft yarns 5b are used as a base material, a polyimide resin 6 is attached to the surface of the fibers constituting the woven fabric 5, and the layer contains pores 7 is defined as the cushioning portion 1. Therefore, the adhesive sheet portion 4, adhesive layer portion 3, and surface layer portion 2 are also considered to be the buffer portion 1 when they meet these conditions. In other words, a layer that does not meet the following conditions, such as having a woven fabric 5 as a base material formed of glass fibers whose warp yarns 5a and / or weft yarns 5b are bulked and textured yarns, having a polyimide resin 6 attached to the surface of the fibers constituting the woven fabric 5, and having pores 7, is not a buffer portion 1.

[0054] [Hot Press Cushioning Material According to Another Embodiment]

[0055] The hot press cushioning material 10 only needs to include the cushioning portion 1, and may include only the cushioning portion 1. The cushioning portion 1 of the hot press cushioning material 10 may be a single layer or multiple layers.

[0056] Figure 4 FIG. 1 shows another embodiment of a heat press cushioning material 10a. Figure 4 As shown, in the hot pressing cushioning material 10a, a surface layer portion 2 is laminated on the surface of the buffer portion 1 via an adhesive layer portion 3. The surface layer portion 2 is provided mainly to impart releasability to the hot pressing cushioning material. As the material of the surface layer portion 2, a synthetic resin film or a substrate formed of a woven fabric coated with a releasable resin on the surface side thereof can be used. In particular, in order to withstand high temperature pressing, it is preferred to use a material that has little dimensional stability, no deformation, good adhesion, and good releasability even when used at high temperatures. In addition, the thickness of the surface layer portion 2 is preferably set to, for example, 0.1 to 0.5 mm. In addition, as the adhesive layer portion 3, a polyimide resin similar to the resin used in the cushioning portion 1 can be used.

[0057] Figure 5 FIG. 1 shows another embodiment of a heat press cushioning material 10b. Figure 5 As shown, in the hot press cushioning material 10b, two layers of cushioning sections 1 are stacked with the aid of an adhesive sheet 4. Furthermore, a surface layer 2 is stacked on the upper and lower surfaces of each cushioning section 1 with the aid of an adhesive layer 3. The cushioning section 1 is formed by impregnating a woven fabric made of glass fiber with resin, so although its thickness is limited, stacking two layers of cushioning sections 1 in this manner has the advantage of further increasing the total thickness of the cushioning section 1. Furthermore, the cushioning sections 1 can be bonded together using only an adhesive, but in this case, the gaps between the weave marks of the cushioning sections 1 are filled with the adhesive, which may reduce the cushioning properties. Therefore, it is preferable to use an adhesive sheet 4. It should be noted that the adhesive sheet 4 is, for example, a sheet-like adhesive layer formed by applying an adhesive to a plain woven fabric made of conventional glass fiber yarns 1b. As the adhesive, a polyimide resin can be used, similar to the resin used in the cushioning section 1. In order to prevent the fibers from cracking from the side and the fluff from falling off, the sides of the manufactured hot press cushioning material may be coated with a heat-resistant resin.

[0058] Figure 5 In the example shown, the example including two layers of the buffer portion 1 is shown, but the hot press buffer material may include three or more layers of the buffer portion 1 .

[0059] Figure 6 FIG. 1 shows another embodiment of a heat press cushioning material 10c. Figure 6As shown, in the hot pressing buffer material 10c, an insulating layer portion 8 is laminated between two layers of buffer portions 1 with the aid of an adhesive sheet portion 4. The insulating layer portion 8 can maintain sufficient heat resistance and durability at the operating temperature of the hot pressing buffer material (for example, above 280°C). In addition, a surface layer portion 2 is laminated on the upper and lower surfaces of each buffer portion 1 with the aid of an adhesive layer portion 3. In this way, the thermal insulation of the hot pressing buffer material 10c can be improved. The insulating layer portion 8 is, for example, a sheet-like object in which an inorganic binder is impregnated in a base material. As a base material, for example, a woven fabric or non-woven fabric formed of inorganic fibers can also be used. Examples of the inorganic fibers include glass fibers, ceramic fibers, alumina fibers, silica fibers, and the like. Examples of the inorganic binder include alkyl silanes, silica, and ceramics.

[0060] Figure 6 In the example shown, an example with two layers of buffer portions 1 and one layer of heat-insulating layer portion 8 is shown, but the hot pressing buffer material may also have three or more layers of buffer portions 1. In addition, the heat-insulating layer portion 8 may also be formed by stacking a plurality of heat-insulating layer portions 8 with the aid of an adhesive layer portion 3 or an 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 performance. It should be noted that from the viewpoint of durability and manufacturability, it is sometimes disadvantageous to consist of a thick heat-insulating layer. Therefore, in the case of a thick heat-insulating layer portion 8, it is preferred to use a relatively thin (for example, about 1.0 mm) heat-insulating layer stacked in two or more layers with the aid of an adhesive layer portion 3 or an adhesive sheet portion 4. In this case, the total thickness can be set in the range of 0.8 to 15 mm.

[0061] It should be noted that when the heat-insulating layer portion 8 contains pores, it assumes the cushioning properties of the hot press cushioning material, similar to the buffer portion 1. That is, the heat-insulating layer portion 8 has sufficient heat resistance and durability at the operating temperature (for example, above 280°C), so, like the buffer portion 1, it can maintain sufficient cushioning properties even when repeatedly used for high-temperature pressing. Moreover, in the hot press cushioning material having the heat-insulating layer portion 8 containing such pores, when the thickness of the hot press cushioning material 10 is set to t0 and the thickness of the hot press cushioning material 10 when compressed according to the following pressing test conditions is set to t1, (t0-t1) can be regarded as the total pore volume of the buffer portion 1 and the heat-insulating layer portion 8. Furthermore, 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 based on the calculated value of "(t0-t1) / t2′". When the heat insulating layer 8 does not contain pores, similarly to the above example, "(t0-t1)" can be regarded as the pore amount of the buffer portion 1. Therefore, the hot press buffer material including such a heat insulating layer 8 can be evaluated by the above-mentioned Fn.

[0062] [Method for Manufacturing a Hot Press Cushioning Material According to an Embodiment]

[0063] First, a woven fabric is prepared in which the warp and / or weft yarns are bulked yarns (bulked glass yarns) formed of glass fibers. The weaving method of the woven fabric is not limited, and for example, a plain weave, a twill weave, or other known weaves can be used.

[0064] Next, a 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. This allows the polyimide resin to adhere to the surface of the fibers constituting the woven fabric, thereby producing the buffer portion (buffer sheet) 1. At this time, the amount of resin attached can be, for example, 20 to 200 g / m2. 2 The amount of resin adhesion can be adjusted by using a resin roller, rubber roller, metal roller, etc. with a pressure of 0.1 to 5 kg / cm 2 Rolling is performed to adjust.

[0065] For coating, it is preferable to use a polyimide resin varnish diluted with NMP (N-methyl-2-pyrrolidone) to adjust the solid content concentration to 2-10% and the viscosity to about 20-100 mPa·s. Alternatively, a polyamic acid solution, which is a polyimide precursor, can be used.

[0066] In the resulting woven fabric with the polyimide resin attached to the fiber surface, the fibers are fixed and covered, maintaining the shape and porosity of the bulked yarn even during high-temperature use. This ensures excellent cushioning properties even with repeated use.

[0067] When the hot press cushioning material has a surface layer portion (surface sheet) 2, for example, a surface layer portion 2 obtained by coating a polyimide resin on one side of a sheet serving as a base material, drying it, and then coating a polyimide resin on the other side and drying it can be used.

[0068] When the hot press cushioning material has an adhesive sheet portion (adhesive sheet) 4, for example, a sheet obtained by coating a resin on both sides of a sheet serving as a base material and drying the resin can be used. The resin is, for example, a polyimide resin. The adhesive sheet portion 4 can also be produced by coating a polyimide resin varnish on a PET film.

[0069] (thickness 40 to 60 μm), and after semi-drying, peeling from the PET film to form a film.

[0070] The cushioning portion 1 and a plurality of sheet-like objects are stacked (for example, the surface sheet 2, the cushioning sheet 1, the adhesive sheet 4, the cushioning sheet 1, and the surface sheet 2 are stacked), and are integrated by heat pressing.

[0071] When the hot press cushioning material has the heat insulating layer portion 8 , for example, the heat insulating layer portion 8 may be formed by preparing a glass woven fabric and attaching an alkylsilane adhesive to the woven fabric.

[0072] The hot press cushioning material according to the present invention can be used in the same manner as before when performing press forming and hot pressing in the manufacture of laminated boards such as printed circuit boards. Figure 7 Specifically, hot pressing is performed with the hot pressing cushioning material 11 interposed between the heating plate 13 and the material to be pressed 12, thereby making the heat and pressure applied to the material to be pressed 12 uniform over the entire surface.

[0073] Example 1

[0074] The following describes the results of manufacturing cushioning materials for Examples and Comparative Examples and examining their various physical properties. Note that Examples 1 to 4 and Comparative Example 1 include a topsheet and an adhesive sheet, while Comparative Examples 2 to 14 do not include a topsheet, adhesive sheet, or the like, but consist solely of a cushioning sheet.

[0075] (Example 1)

[0076] As the woven fabric material, a double twill bulked glass woven fabric was prepared, with two glass yarns (yarn count 67.5 tex) twisted together as the warp (unbulked yarn with a single fiber diameter of 5 μm and a single fiber count of 2400) and four glass yarns (yarn count 67.5 tex) twisted together as the weft (bulked textured yarn with a single fiber diameter of 5 μm and a single fiber count of 4800). Furthermore, as the resin material, a polyimide resin varnish (5% concentration) with a thermal decomposition temperature of 512°C and a glass transition temperature of 400°C or higher was prepared. This polyimide resin varnish was impregnated into the glass woven fabric and then dried at 200°C for 5 minutes to prepare a cushioning sheet with 1.7% by mass of the polyimide resin attached to the woven fabric.

[0077] On the other hand, a surface sheet was prepared by coating a polyimide resin varnish on one side (the front side) of a plain woven glass fabric, drying it, and then coating the polyimide resin varnish on the opposite side (the adhesive layer) and drying it. Furthermore, an adhesive sheet was prepared by coating a polyimide resin varnish on both sides (the adhesive layers) of a plain woven glass fabric and drying it.

[0078] The obtained surface sheet, buffer sheet, adhesive sheet, buffer sheet, and surface sheet were stacked in sequence and pressed under the conditions of 10 MPa×190°C, heating for 60 minutes + cooling for 10 minutes, and then heat treated at 300°C×5 hours to obtain a sample of the hot pressing buffer material.

[0079] (Example 2)

[0080] A sample of a hot press cushioning material having the same structure as that of Example 1 was obtained by using a cushioning sheet in which the resin adhesion amount of Example 1 was changed to 3.4% by mass.

[0081] (Example 3)

[0082] A sample of a hot press cushioning material having the same structure as that of Example 1 was obtained by using a cushioning sheet in which the resin adhesion amount of Example 1 was changed to 8.8% by mass.

[0083] (Example 4)

[0084] A sample of a hot press cushioning material having the same structure as that of Example 1 was obtained by using a cushioning sheet in which the resin adhesion amount of Example 1 was changed to 13.2% by mass.

[0085] (Comparative Example 1)

[0086] A cushioning sheet was prepared in which the same bulky glass woven fabric as in Example 1 was impregnated with 10.5% by mass of fluororubber. Furthermore, a sample of a hot press cushioning material having the same structure as in Example 1 was prepared in which a fluororubber varnish was applied to the surface sheet and the adhesive sheet instead of the polyimide resin varnish serving as the adhesive layer in Example 1.

[0087] (Comparative Example 2)

[0088] A twill weave fabric with a weft density of 22 strands / 2.5 cm and a twill weave density of 22 strands / 2.5 cm was prepared by applying a polyimide resin (the same as that in Example 1) to a twill weave fabric with a weft density of 22 strands / 2.5 cm and a weft density of 34 strands / 2.5 cm. The fabric was dried at 230°C for 5 hours to prepare a 0.75 mm thick cushion sheet with a resin deposition rate of 2.8% by mass relative to the mass of the substrate. Three of these cushion sheets were stacked to obtain a sample of a hot press cushioning material.

[0089] (Comparative Example 3),

[0090] A polyimide resin (the same as that used in Example 1) was applied to a satin weave fabric with a weft density of 30 yarns / 2.5 cm and a warp density of 45 warps / 2.5 cm, using a 67.5 tex yarn count (untextured yarn) twisted with four glass yarns (67.5 tex) for the warp and 4 tex yarns (untextured yarn) for the weft. The fabric was dried at 230°C for 5 hours to prepare a 1.10 mm thick cushioning sheet with a resin deposition rate of 3.1% by mass relative to the base material mass. Two of these cushioning sheets were stacked to produce a sample of a hot press cushioning material.

[0091] (Comparative Example 4)

[0092] A cushion sheet was prepared using two poly(m-phenylene isophthalamide) staple yarns (59.1 tex, 10-weave cotton yarn) twisted together as the warp yarn and three poly(m-phenylene isophthalamide) staple yarns (59.1 tex, 10-weave cotton yarn) twisted together as the weft yarn. The fabric had a weft density of 93 warps / 2.5 cm and 66 wefts / 2.5 cm, resulting in a triple twill weave (2.40 mm thick). A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0093] (Comparative Example 5)

[0094] The woven fabric of Comparative Example 4 was impregnated with poly(m-phenylene isophthalamide) resin (10% concentration) and dried at 230°C for 5 hours to prepare a 2.40 mm thick cushion sheet with a resin deposition ratio of 3.3% by mass relative to the mass of the substrate. A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0095] (Comparative Example 6)

[0096] The woven fabric of Comparative Example 4 was impregnated with a polyimide resin (the same as that used in Example 1) and dried at 230°C for 5 hours to prepare a 2.40 mm thick cushion sheet with a resin deposition ratio of 3.1% by mass relative to the mass of the substrate. A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0097] (Comparative Example 7)

[0098] A cushion sheet (2.60 mm thick) was prepared using two poly(m-phenylene isophthalamide) staple yarns (59.1 tex, 10-weave cotton yarn) twisted together as the warp yarn and three poly(m-phenylene isophthalamide) staple yarns (59.1 tex, 10-weave cotton yarn) twisted together as the weft yarn. The weft density was 109 warps / 2.5 cm and 85 wefts / 2.5 cm, resulting in a 4-fold twill weave. A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0099] (Comparative Example 8)

[0100] The woven fabric of Comparative Example 7 was impregnated with poly(m-phenylene isophthalamide) resin (10% concentration) and dried at 230°C for 5 hours to prepare a 2.60 mm thick cushion sheet with a resin deposition ratio of 3.3% by mass relative to the mass of the substrate. A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0101] (Comparative Example 9)

[0102] The woven fabric of Comparative Example 7 was impregnated with a polyimide resin (the same as that used in Example 1) and dried at 230°C for 5 hours to prepare a 2.60 mm thick cushion sheet with a resin deposition ratio of 3.0% by mass relative to the mass of the substrate. A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0103] (Comparative Example 10)

[0104] The warp yarn was made of two twisted poly(p-benzoxazole) staple yarns (yarn count 29.5 tex, cotton yarn count: 20 yarn count), and the weft yarn was made of two twisted poly(p-benzoxazole) staple yarns (yarn count 29.5 tex, cotton yarn count: 20 yarn count). A 0.52 mm thick cushioning sheet was prepared, with a twill weave density of 68 warps / 2.5 cm and 60 wefts / 2.5 cm. Four of these cushioning sheets were stacked to produce a sample of a pressure cushioning material.

[0105] (Comparative Example 11)

[0106] The woven fabric of Comparative Example 10 was impregnated with a polyimide resin (the same as that of Example 1) and dried at 230°C for 5 hours to prepare a cushioning sheet having a resin deposition ratio of 3.3% by mass relative to the mass of the substrate. Four of these cushioning sheets were stacked to obtain a sample of a pressure-absorbing cushioning material.

[0107] (Comparative Example 12)

[0108] Three layers of polyparabenzoxazole fiber (Zylon manufactured by Toyobo Co., Ltd.) were alternately laminated with two layers of glass cloth cold yarn base fabric to prepare a cushioning sheet made of a 4.5 mm thick nonwoven fabric. A sample of a hot press cushioning material consisting of one sheet of this cushioning sheet was obtained. The weight per unit area was set to 1350 g / m 2 (Net: 1180g / m 2 , Base fabric: 170g / m 2 ).

[0109] (Comparative Example 13)

[0110] A cushioning sheet made of a nonwoven fabric having a thickness of 5.0 mm, obtained by needle-punching a mesh formed of SUS fibers, was prepared, and a sample of a hot press cushioning material consisting of one sheet of this cushioning sheet was obtained.

[0111] (Comparative Example 14)

[0112] The nonwoven fabric of Comparative Example 13 was impregnated with a polyimide resin (the same as that used in Example 1) and dried at 230°C for 5 hours to prepare a 5.0 mm thick cushion sheet with a resin deposition ratio of 3.4% by mass relative to the mass of the substrate. A sample of a hot press cushioning material consisting of one sheet of this cushion sheet was obtained.

[0113] Table 1 shows the base materials of various buffer sheets. Table 2 shows the conditions of various buffer sheets.

[0114] [Table 1]

[0115] Table 1

[0116]

[0117] ※1: 1tex 1000m of yarn weighs 1g

[0118] ※2: 1 yarn count 1 pound (453g) weighs 840 yards (768m) of yarn

[0119] ※3: Number of times per 1m

[0120] [Table 2]

[0121] Table 2

[0122]

[0123] The following press durability test was conducted on various hot press cushioning materials, and the changes in thickness and cushioning properties before and after the test were measured. The results are shown in Tables 3 to 8.

[0124] [Pressing durability test conditions]

[0125] Pressurization pressure: 4.0MPa

[0126] Temperature: 400℃, 300℃, 280℃

[0127] Heating time: 70 minutes (heating from 25°C to the specified temperature within 30 minutes, maintaining this state for 40 minutes)

[0128] Cooling time: 30 minutes (water cooling)

[0129] Opening time: 1 minute

[0130] Sample size: 200mm square

[0131] Press: Compact Press MHPC-VF-450-450-1-80 (manufactured by Nippon Steel Works, Ltd.)

[0132] (Thickness Evaluation Method)

[0133] For each sample, the thickness before pressing and the thickness (mm) after pressing once, 10 times, 50 times, and 100 times were measured using a direct-reading thickness gauge.

[0134] (Evaluation method of cushioning properties)

[0135] The cushioning properties of each sample were evaluated before pressing and after 1, 10, 50, and 100 press cycles. The following pressurization test was performed on each sample, and the compression cushioning properties were determined from the difference in thickness (μm) before and after pressing.

[0136] Pressurization pressure: 4.0MPa

[0137] Pressing temperature: 400℃, 300℃, 280℃

[0138] Preheating: 0.05kgf / cm 2 ×2 minutes

[0139] Pressurization speed: 1mm / min

[0140] Sample size:

[0141] Sample collection location: One location at least 5 cm from one end of the durability test sample

[0142] Test equipment: Instron universal testing machine model 5565 (manufactured by Instron Japan Company Limited)

[0143] [Porosity evaluation compression test conditions]

[0144] For each sample, the porosity Fn of the buffer portion was determined before pressing, and after pressing once, 10 times, 50 times, and 100 times. It should be noted that in this comparative experiment, the durability test samples were as small as 200 mm square, so the porosity Fn evaluation sample was collected only from a single location, at least 5 cm from one end.

[0145] Pressurization pressure: 10MPa

[0146] Temperature: 25℃

[0147] Pressurization speed: 5mm / min

[0148] Sample size: 25mm square

[0149] Sample collection location: One location at least 5 cm from one end of the durability test sample

[0150] Test equipment: Autograph precision universal testing machine AG-X (manufactured by Shimadzu Corporation)

[0151] (Porosity Evaluation Method)

[0152] For Examples 1 to 4 and Comparative Example 1, fabrics using bulky glass as buffer sheets, the thickness t0 of the samples before compression, the thickness t2 of the buffer section 1, and the thickness t1 during compression were measured under the above-described conditions. Note that the thickness t0 of the samples before compression was measured at a single point near the center of the sample using a direct-reading thickness gauge, while the thickness t1 during compression was measured using an Autograph precision universal testing machine based on the porosity evaluation compression test conditions described above. Furthermore, the thickness t2 of the buffer section 1 was measured by observing the cross section of the sample at 50x magnification using an electron microscope (Keyence VHX series). The distance between a line connecting the two vertices of the upper side of the buffer sheet and a line connecting the two vertices of the lower side of the fiber (warp or weft) bent along the buffer sheet's cross section was measured using a measuring tool. If the buffer sheet has multiple layers, the total thickness is defined as the thickness t2 of the buffer section 1. The thickness t2 was averaged at a single point near the center of each side of the sample (a total of four points).

[0153] [Table 3]

[0154] Table 3

[0155]

[0156] Test temperature: 400℃

[0157] [Table 4]

[0158] Table 4

[0159]

[0160] Test temperature: 400℃

[0161] [Table 5]

[0162] Table 5

[0163]

[0164] Test temperature: 300℃

[0165] [Table 6]

[0166] Table 6

[0167]

[0168] Test temperature: 300℃

[0169] [Table 7]

[0170] Table 7

[0171]

[0172] Test temperature: 280℃

[0173] [Table 8]

[0174] Table 8

[0175]

[0176] Test temperature: 280℃

[0177] As shown in Tables 2 to 8, Examples 1 to 4 that meet the conditions of the present invention have good cushioning properties at any test temperature. That is, Examples 1 to 4 maintain high porosity at any test temperature even after 100 pressings, and have good durability and cushioning properties. On the other hand, in Comparative Examples 1 to 14, the thickness and cushioning properties are extremely reduced even after a single test. In particular, in the 400°C test, the fluororubber in Comparative Example 1 is carbonized, and the polyisophthalamide fibers in Comparative Examples 4 to 9 are also carbonized and degraded, and do not have sufficient heat resistance. In addition, in Comparative Examples 13 and 14, the thickness and cushioning properties are significantly reduced in the durability test, so stable cushioning properties cannot be obtained during repeated use.

[0178] In addition, the meanings of A to G in "Evaluation" in Tables 3 to 8 are as follows.

[0179] AGood

[0180] B presses once and the cushioning property decreases.

[0181] C: The rubber is carbonized. In addition, the surface layer peels off and cannot maintain its shape.

[0182] D Pressing once significantly reduces thickness and cushioning properties.

[0183] E suppresses carbonization degradation once.

[0184] F cracked after 10 presses. In addition, the thickness and cushioning properties were significantly reduced.

[0185] G thickness and cushioning properties are significantly reduced.

[0186] H press cracks after 50 cycles. Thickness and cushioning properties are significantly reduced.

[0187] Industrial applicability

[0188] According to the present invention, it is possible to provide a hot press cushioning material that can maintain excellent cushioning properties even when repeatedly used for high-temperature pressing at 280°C or higher.

[0189] Description of Reference Numerals

[0190] 1 buffer part

[0191] 2 Surface

[0192] 3 Adhesive layer

[0193] 4 Adhesive sheet

[0194] 5. Weaving

[0195] 5a Warp

[0196] 5b Weft

[0197] 6Polyimide resin

[0198] 7 pores

[0199] 11. Cushioning materials

[0200] 12 Pressed materials

[0201] 13.13 Heating plate

[0202] 14 Mirror Panel

Claims

1. A hot press cushioning material having a cushioning portion, The buffer portion includes a woven fabric and a polyimide resin attached to the surface of fibers constituting the woven fabric, and has pores inside. The warp yarn and / or weft yarn of the woven fabric is a bulked and textured yarn formed of glass fiber. The polyimide resin has a thermal decomposition temperature and a glass transition temperature greater than a pressing temperature.

2. The hot press cushioning material according to claim 1, wherein When the thickness of the hot press cushioning material is t0, the thickness of the hot press cushioning material when compressed at 25°C and 10.0 MPa is t1, and the thickness of the buffer portion is t2, Fn obtained from the following formula (1) is 0.20 or more. Fn=(t0-t1) / t2···(1).

3. The hot press cushioning material according to claim 2, wherein After one press cycle under the conditions of 4.0 MPa pressure, heating from 25°C to 300°C over 30 minutes, maintaining the temperature for 40 minutes, and then water cooling for 30 minutes, the Fn obtained according to (1) is 0.20 or more.

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