cushioning material

Abstract

The present invention relates to a cushioning material for hot pressing, comprising at least one perfluoroelastomer sheet and at least two fabric sheets, wherein the cushioning material can be used under high temperature and pressure conditions.

Description

Technical Field

[0001] This invention relates to a cushioning material comprising a perfluoroelastomer sheet and a fabric, which can be used as a hot-pressed cushioning material for use under high-temperature pressing conditions. Background Technology

[0002] Laminates, such as printed circuit boards or IC substrates, are manufactured using a hot-pressing process. During the hot-pressing process, a cushioning material is placed between the laminated materials and the hot-pressing plate to ensure uniform lamination of the laminated materials.

[0003] Cushioning materials made of elastomeric sheets laminated with fabrics are known, for example, JP U4 8031033 B, JP5204429 B, and WO 2003537381 A. Common elastomers used as cushioning materials include ethylene-propylene-diene rubber (EPDM), silicone rubber, and fluoroelastomers. These elastomers have limited heat resistance; for example, fluoroelastomers have a maximum heat resistance of 230°C.

[0004] Recently, due to the demand for higher semiconductor and electronic properties, PTFE resin and / or liquid crystal polymer (LCP) have been used in printed circuit board materials. The hot-pressing process temperature of these materials is around 300°C, far exceeding the heat resistance of traditional elastomers. Therefore, instead of elastomers, glass fiber fabrics, aramid fiber fabrics, stainless steel fiber fabrics, and kraft paper are used as cushioning materials for these high-temperature pressing conditions, as disclosed in JP 6790297 B and JP 2019161206 A.

[0005] Furthermore, in the manufacturing process of mounting power semiconductors on an insulating substrate, the pressing temperature is also around 300°C. Silicone elastomers are used as cushioning materials for this application; however, due to the lack of heat resistance to 300°C, silicone elastomers cannot be reused and therefore need to be replaced after each pressing.

[0006] There are currently no elastomeric cushioning materials on the market that can be repeatedly used at this high temperature (300°C) and have excellent cushioning capabilities. Summary of the Invention

[0007] This problem can be solved by cushioning materials with high heat resistance formed from perfluoroelastomer sheets and fabric sheets.

[0008] Therefore, the present invention relates to a cushioning material for hot pressing, comprising at least two fabric sheets and at least one perfluoroelastomer sheet, the fabric sheets being located on the upper and lower sides of the perfluoroelastomer sheet, wherein the perfluoroelastomer sheet is formed of a perfluoroelastomer composition comprising:

[0009] (A) A perfluoroelastomer comprising copolymer units of the following:

[0010] (i) One or more unsaturated perfluorinated olefins;

[0011] (ii) One or more perfluorovinyl ethers selected from the group consisting of: perfluoro(alkylvinyl) ethers, perfluoro(alkoxyvinyl) ethers, and mixtures of perfluoro(alkylvinyl) ethers and perfluoro(alkoxyvinyl) ethers;

[0012] (iii) One or more monomers with curing sites, selected from the group consisting of bromine atoms, iodine atoms and nitrile groups;

[0013] (B) One or more curing agents, and

[0014] (C) Optionally, one or more fillers.

[0015] The present invention further relates to a hot pressing apparatus for manufacturing printed circuit boards comprising PTFE resin and / or liquid crystal polymer, wherein the hot pressing apparatus includes the cushioning material as described above.

[0016] The present invention further relates to a hot pressing apparatus for a manufacturing process of mounting power semiconductors on an insulating substrate, wherein the hot pressing apparatus includes the buffer material as described in claim 1.

[0017] The present invention further relates to a method for manufacturing a cushioning material for hot pressing, the method comprising the following steps:

[0018] (1) Prepare at least one perfluoroelastomer sheet, the perfluoroelastomer sheet being formed from a composition comprising the following:

[0019] (A) A perfluoroelastomer comprising copolymer units of the following:

[0020] (i) One or more unsaturated perfluorinated olefins;

[0021] (ii) One or more perfluorovinyl ethers selected from the group consisting of: perfluoro(alkylvinyl) ethers, perfluoro(alkoxyvinyl) ethers, and mixtures of perfluoro(alkylvinyl) ethers and perfluoro(alkoxyvinyl) ethers; and

[0022] (iii) One or more monomers with curing sites, selected from the group consisting of bromine atoms, iodine atoms and nitrile groups;

[0023] (B) One or more curing agents, and

[0024] (C) Optionally, one or more fillers

[0025] (2) The perfluorinated elastomer sheet is applied between two fabric sheets.

[0026] (3) Hot-press these laminated sheets to bond the fabric sheet and the perfluoroelastomer sheet together, then

[0027] (4) Further heat the hot-pressed laminated sheet to form crosslinks of the perfluoroelastomer. Attached Figure Description

[0028] Figure 1 The graph shows the thickness retention rates of Examples 1 to 3 and Comparative Examples 1 to 4.

[0029] Figure 2 This is the compressive stress curve of the test sample in Example 1.

[0030] Figure 3 This is the compressive stress curve of the test sample in Example 2.

[0031] Figure 4 This is the compressive stress curve of the test sample in Comparative Example 1.

[0032] Figure 5 This is the compressive stress curve of the test sample in Comparative Example 2.

[0033] Figure 6 This is the compressive stress curve of the test sample in Comparative Example 3.

[0034] Figure 7 This is the compressive stress curve of the test sample in Comparative Example 4.

[0035] Figure 8 This is the compressive stress curve of the test sample in Example 3.

[0036] Figure 9A This is a photograph of the surface appearance of the test sample in Example 1 before the compression test.

[0037] Figure 9B This is the surface appearance of the test sample in Example 1 after the compression test. Detailed Implementation

[0038] abbreviation

[0039] The claims and description herein are interpreted using the abbreviations and definitions listed below.

[0040] “h” and “hrs” refer to hours.

[0041] "%" refers to the term percentage.

[0042] “wt%” refers to weight percentage.

[0043] "°C" refers to degrees Celsius.

[0044] "Mole %" means mole percentage.

[0045] "Parts" means parts by weight.

[0046] "phr" means parts per hundred parts of fluoroelastomer (rubber); this measurement term is used and recognized by those skilled in the art. For example, 3 parts of a component per 100 parts of fluoroelastomer is written as 3 phr. In the compositions, methods, and articles described herein, phr is based on 100 parts of fluoroelastomer.

[0047] "g" means gram.

[0048] Buffer material

[0049] (I) Perfluoroelastomer sheet

[0050] The perfluoroelastomer layer is a cured perfluoroelastomer and is formed from a composition comprising: (A) a perfluoroelastomer comprising copolymer units of: (i) an unsaturated perfluorinated olefin, (ii) an unsaturated perfluorinated olefin, typically a perfluoro vinyl ether, and (iii) a cure site monomer; (B) a curing agent and optionally (C) a filler and (D) other components.

[0051] (A) Perfluoroelastomer

[0052] The perfluoroelastomers described herein can comprise at least the following three copolymer units: (i) one or more unsaturated perfluorinated olefins; (ii) one or more unsaturated perfluorinated olefin comonomers that are different from the unsaturated perfluorinated olefin (i) and are selected from the group consisting of perfluoro vinyl ethers, unsaturated perfluorinated olefins, and mixtures of perfluoro vinyl ethers and unsaturated perfluorinated olefins; and (iii) one or more cure site monomers selected from the group consisting of nitrile-containing fluorinated olefins, nitrile-containing fluorinated vinyl ethers, or mixtures thereof.

[0053] Alternatively, the perfluoroelastomer may comprise at least three copolymerizable monomer units: (i) one or more unsaturated perfluorinated olefins in about 25 to 74.9 mol percent; (ii) one or more unsaturated perfluorinated olefin comonomers in about 25 to 74.9 mol percent, which are different from the unsaturated perfluorinated olefin (i) and selected from the group consisting of: perfluorinated vinyl ethers, unsaturated perfluorinated olefins, and mixtures of perfluorinated vinyl ethers and unsaturated perfluorinated olefins; and (iii) one or more curing site monomers in about 0.1 to 10 mol percent, selected from the group consisting of: nitrile-containing fluorinated olefins, nitrile-containing fluorinated vinyl ethers, or mixtures thereof, wherein the molar percentage of each of (i), (ii) and (iii) is based on the total molar percentage of (i), (ii) and (iii) in the perfluoroelastomer.

[0054] Because a variety of initiators or chain transfer agents are used during polymerization, the perfluoroelastomers described herein can contain any of a variety of end groups. Non-limiting examples of end groups include sulfonates, sulfonic acids, carboxylic esters, carboxylic acids, carboxamides, difluoromethyl, trifluorovinyl, or perfluorinated alkyl groups.

[0055] (i) Unsaturated perfluorinated olefins

[0056] Examples of unsaturated perfluorinated olefins include tetrafluoroethylene (C2F4), hexafluoropropylene, and combinations thereof. The concentration range of unsaturated perfluorinated olefins (i) can be from 25 to 74.9 mol percent of the total number of monomer units in the perfluorinated elastomer.

[0057] (ii) Unsaturated fluorinated olefin comonomers

[0058] Unsaturated perfluorinated olefin comonomer (ii), which is different from unsaturated perfluorinated olefin (i) and is selected from the group consisting of: perfluorinated vinyl ethers, unsaturated perfluorinated olefins, and mixtures of perfluorinated vinyl ethers and unsaturated perfluorinated olefins.

[0059] Examples of perfluorovinyl ethers used in the preparation of perfluoroelastomers include perfluoro(alkylvinyl) ethers (PAVE), perfluoro(alkoxyvinyl) ethers, and mixtures of perfluoro(alkylvinyl) ethers (PAVE) and perfluoro(alkoxyvinyl) ethers. Suitable perfluoro(alkylvinyl) ethers that can be used to prepare the compositions described herein include those shown in formulas (II) to (VI):

[0060] CF2=CFO(R f′ O) n (R f″ O) m R f (II)

[0061] Where R f′ and R f″ It is a different straight-chain or branched perfluoroalkylene group having 2-6 carbon atoms, where m and n are independently 0-10, and R f It is a perfluoroalkyl group having 1-6 carbon atoms.

[0062] Further examples of perfluoro(alkyl vinyl) ethers include compositions having formula (III):

[0063] CF2 = CFO(CF2CFXO) n R f (III),

[0064] Where X is F or CF3, n is 0-5, and R f It is a perfluoroalkyl group having 1-6 carbon atoms. Alternatively, n is 0 or 1, and R f It contains 1-3 carbon atoms. Examples of such perfluorinated (alkyl vinyl) ethers include perfluorinated (methyl vinyl) ethers and perfluorinated (propyl vinyl) ethers.

[0065] Other perfluoro(alkyl vinyl) ether monomers used in the preparation of fluoroelastomers include monomers having formulas (IV), (V), and (VI):

[0066] CF2 = CFO[(CF2)] m CF2CFZO] n R f (IV),

[0067] Where R f It is a perfluoroalkyl group having 1-6 carbon atoms, m = 0 or 1, n = 0-5, and Z = F or CF3;

[0068] CF2 = CFO[(CF2CFCF3O)] n (CF2CF2CF2O) m (CF2) p C x F 2x+1 (V),

[0069] Where m and n = 1-10, p = 0-3, and x = 1-5. Specific embodiments of this type include monomers where n = 0-1, m = 0-1, and x = 1, and...

[0070] CF2=CFOCF2CF(CF3)O(CF2O) m C n F 2n+1 (VI),

[0071] Where n = 1-5, m = 1-3, and where, alternatively, n = 1.

[0072] Examples of perfluoro(alkyl vinyl) ethers include perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluoroethyl vinyl ether. Examples of perfluoro(alkoxy vinyl) ethers include perfluoromethoxy vinyl ether, perfluoropropoxy vinyl ether, and perfluoroethoxy vinyl ether.

[0073] Examples of unsaturated perfluorinated olefins include tetrafluoroethylene (C2F4); hexafluoropropylene; and combinations thereof. Mixtures of perfluorinated vinyl ethers and unsaturated perfluorinated olefins can also be used.

[0074] The concentration of unsaturated perfluorinated olefin comonomers in the fluoroelastomer is in the range of 25 to 74.9 mol percent, alternatively 30 to 65 mol percent, or alternatively 45 to 55 mol percent, based on the total molar percentage of monomer units in the perfluorinated elastomer.

[0075] (iii) Monomer at the curing site

[0076] The perfluoroelastomer (A) further comprises a copolymer unit of one or more curing site monomers containing at least one nitrile substituent. Alternatively, the curing site monomer is selected from the group consisting of nitrile-containing fluorinated olefins and nitrile-containing fluorinated vinyl ethers (iii). The amount of such curing site monomer is typically from 0.1 to 10 mol percent based on the total molar percentage of polymerizable monomer units used to prepare the fluoroelastomer, and alternatively between 0.3 and 1.5 mol percent. While more than one type of curing site monomer may be present, the curing site monomer contains at least one nitrile substituent. Useful nitrile-containing curing site monomers include those having formulas (VII) - (XI):

[0077] CF2 = CF - O(CF2) n -CN (VII)

[0078] Where n = 2-12, or alternatively 2-6;

[0079] CF2 = CF - O[CF2 - CFCF3 - O] n -CF2-CFCF3-CN (VIII),

[0080] Where n = 0-4, or alternatively 0-2;

[0081] CF2 = CF - [OCF2CFCF3] x -O-(CF2) n -CN (IX),

[0082] Where x = 1-2 and n = 1-4; and

[0083] CF2 = CF - O - (CF2) n -O-CF(CF3)CN (X),

[0084] Where n = 2-4.

[0085] Monomers having formula (IX) are used as curing site monomers. In particular, curing site monomers include perfluorinated polyethers having nitrile and trifluorovinyl ether groups. Alternatively, the curing site monomer is perfluorinated (8-cyano-5-methyl-3,6-dioxa-1-octene) (8-CNVE) and is represented by formula (XI):

[0086] CF2=CFOCF2CF(CF3)OCF2CF2CN (XI)

[0087] B) Curing agent

[0088] The composition comprises at least one curing agent (B). The perfluoroelastomer used in the compositions of the present invention can be crosslinked with any known curing agent for perfluoroelastomers, such as, but not limited to, combinations of polyhydroxy compounds such as organic peroxides and multifunctional auxiliaries (US Patent Nos. 4,214,060; 4,983,680), organotin compounds (US Patent Nos. 5,789,489), bis(aminophenols) such as diaminobisphenol AF (US Patent No. 6,211,319 B1), aromatic tetraamines such as 3,3'-diaminobenzidine, 2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane, and ammonia-generating compounds such as urea, as well as other compounds disclosed in US Patent Nos. 6,281,296 and WO 01 / 27194.

[0089] One type of curing agent that can be used is an ammonia-generating compound that decomposes at a curing temperature to produce ammonia. Examples of such ammonia-generating compounds include dicyandiamide, aldehyde-ammonia condensation products (including acetaldehyde-ammonia); and other compounds such as hexamethylenetetramine; carbamates, such as tert-butyl carbamate, benzyl carbamate, and HCF2CF2CH(CH3)OCONH2; urea; urea hydrochloride; thiourea; amides, such as phthalamide; metal ammonia complexes, such as copper(II) tetraamine sulfate hydrate; ammonia-Lewis acid adducts; formamides, such as oxaline; biuret; and unsubstituted amidines, such as formamine, formamine hydrochloride, and formamine acetate. Typically, such ammonia-generating compounds decompose and produce ammonia between 40°C and 330°C, or alternatively between 90°C and 220°C.

[0090] The amount of curing agent necessarily depends on the degree of crosslinking and the type and concentration of the reactive portion, but an example of curing agent level should be about 0.1 to 7 parts of compound per 100 parts of perfluoroelastomer, or alternatively about 1 to 5 parts of compound per 100 parts of perfluoroelastomer.

[0091] C) Packing

[0092] The compositions described herein may additionally contain fillers. Various fillers can be used, including both organic and inorganic fillers.

[0093] Examples of such fillers include carbon black, glass fiber, metal oxides such as alumina (Al₂O₃) or titanium dioxide (TiO₂), and anhydrous silica such as acidic silica or fumed silica. Examples of titanium dioxide include Ti-Pure™ R-101 and Pigment White 6, available from Chemours. Examples of barium sulfate include Blanc Fixe, available from Solvay Chemicals, and Huberbrite® from Huber Engineering Materials. Examples of such silica include anhydrous silica available under the trademark Aerosil® from Degussa Aktiengesellschaft (Frankfurt, Germany). A particularly useful type is Aerosil® 200 silica. Other suitable silicas include Reolosil® silicas, such as Reolosil® QS13, Reolosil® QS102, and Reolosil® QS30, available from Tokuyama KK Co., Ltd. (Tokyo, Japan). The amount of silica ranges from 1 to 25 phr, and alternatively, not exceeding 1 to 7 phr.

[0094] Other types of fillers include micronized powders or fluorinated additives. Micronized powders are typically partially crystalline polymers. Micronized powders include finely separated, easily dispersible fluoropolymers that are solid at the highest temperatures used in the manufacture and curing of the compositions described herein. The term "solid" refers to a fluoropolymer with a crystallization melt temperature higher than the processing temperature of the compositions described herein.

[0095] Microparticles that can be used in these compositions include, but are not limited to, microparticles based on a group of polymers known as tetrafluoroethylene (TFE) polymers. This group includes polytetrafluoroethylene (PTFE) and copolymers of TFE.

[0096] D) Other ingredients

[0097] Additives typically used in compounding, such as stabilizers, plasticizers, lubricants, and processing aids, can be incorporated into the compositions described herein, provided they possess sufficient stability for the intended use conditions. In particular, low-temperature performance can be enhanced by incorporating perfluoropolyethers.

[0098] A copolymerizable modifying monomer is used to prevent the microparticles from melting or softening during the processing of fluoroelastomer A containing microparticles. This modifying monomer can be, for example, hexafluoropropylene (HFP), perfluoro(propyl vinyl) ether (PPVE), perfluorobutylethylene, trichlorofluoroethylene, or another monomer with side groups introduced into the polymer molecule.

[0099] In these compositions, the tetrafluoroethylene polymers used as additives include copolymers of TFE having sufficient concentrations of copolymer units of one or more monomers to lower the melting point below that of PTFE. Such copolymers generally have a melting point between 0.5 and 60 × 10⁻⁶. 3 Melt viscosities are within the Pa·s range, but viscosities outside this range are also known. Perfluoroolefins and perfluoro(alkyl vinyl) ethers are preferred comonomers. Hexafluoropropylene and perfluoro(propyl vinyl) ethers are most preferred. Examples of TFE copolymers include TFE / hexafluoropropylene copolymers and TFE / perfluoro(propyl vinyl) ether copolymers, provided they meet the limitations on melt temperature relative to the processing temperature of the perfluoroelastomer. If the particle size is acceptable, these copolymers can be used in powder form separated from the polymerization medium, or they can be started from larger feedstocks and ground to a suitable particle size.

[0100] The amounts of such other components in these compositions range from about 0.01 to 100 phr, and alternatively from about 0.1 to 50 phr.

[0101] The compositions described herein can be prepared by mixing a perfluoroelastomer (A), a curing agent (B), and optionally a filler (C) and any other component (D) until homogeneous to form a perfluoroelastomer sheet. Rubber compounding processes such as a two-roll rubber mixer, an internal mixer (e.g., a Banbury mixer), or an extruder can be used to mix the compositions. The compositions can then be formed into sheets using calendering rolls or any other equipment.

[0102] (II) Fabric sheets

[0103] The cushioning material of this invention comprises a fabric sheet. Any known fabric can be used, provided its heat resistance exceeds 300°C. Examples of such fabrics include: meta-aramid fiber fabrics, para-aramid fiber fabrics, glass fiber fabrics, carbon fiber fabrics, ceramic fiber fabrics, polybenzobisoxazole fiber fabrics, and metal fiber fabrics. Meta-aramid fiber fabrics and glass fiber fabrics are preferred.

[0104] Both woven and non-woven fabrics can be used. For woven fabrics, any type of fabric can be used, such as plain weave, twill weave, and satin weave. Multi-woven fabrics can also be used.

[0105] The thickness of the fabric is, for example, 0.01 to 5 mm, or alternatively 0.1 to 2 mm, or alternatively 0.2 to 1 mm.

[0106] Examples of commercially available aramid fiber fabrics include Nomex NX-2232, NX-2239, and NX-2245 meta-aramid fiber fabrics available from TEIKOKU SEN-ICo., Ltd.; and CO1200, CO1500, CO1600, CO1700, CO1910, CO2016, CO3501, CO3500, CO3942, CO5261, and CO5252 from TEIJIN FRONTIER CO., LTD. Examples of commercially available fiberglass fabrics include KS4010, S4155, and KS4325 from Nitto Boseki Co., Ltd.; NGC330, NGC450, NGC850, NGC1000, and NGC2000 from Nihon Glass Fiber Industrial Co., Ltd.; TOMBO No. 8400, TOMBO No. 8400H, and TOMBO No. 8400R from Nichias Corporation; TR7610N, TR9010N, and TR1610N from Maeda Glass Co., Ltd.; and Chubu Kogyo Co., Ltd. The CGC-850, CGC-1000, CGC-1200 and CGC-2000 are available from Ltd.

[0107] (III) Methods for preparing buffer materials

[0108] Two fabric sheets are placed on the plate-like surfaces of a perfluoroelastomer sheet, and the laminated sheets are then hot-pressed for 5 to 30 minutes at 120°C to 250°C, for example, under 1 to 100 tons of pressure. The pressure, temperature, and time are varied but sufficient to bond the fabric and perfluoroelastomer sheets. Partial crosslinking can occur during the hot-pressing step. Additional heating (post-curing) can be performed using an oven at, for example, 180°C to 350°C, or alternatively 250°C to 310°C, under air or nitrogen for 4 to 30 hours to ensure that the curing agent crosslinks with the monomers at the curing sites.

[0109] The cushioning material of this invention can be single-layered or multi-layered. 'Single-layered' means that the cushioning material comprises one perfluoroelastomer sheet and two fabric sheets, i.e., one perfluoroelastomer sheet sandwiched between two fabric sheets. 'Multi-layered' means that the cushioning material comprises at least two perfluoroelastomer sheets, and each of these perfluoroelastomer sheets is sandwiched between fabric sheets, i.e., two or more perfluoroelastomer sheets and fabric sheets are stacked alternately (one after another).

[0110] The resulting cushioning material can be used at higher temperatures than conventional cushioning materials. Therefore, this cushioning material can be used in hot-pressing equipment for printed circuit boards containing PTFE resin and / or liquid crystal polymer (LCP). The hot-pressing process temperature for this material is around 300°C, significantly higher than the heat resistance of conventional elastomers.

[0111] Furthermore, this buffer material can be used in hot-pressing equipment during the manufacturing process of mounting power semiconductors on an insulating substrate. Because the buffer material of this invention has high heat resistance, it can be reused in this hot-pressing process. Example

[0112] Material

[0113] FFKM Sheet: A perfluoroelastomer composition containing tetrafluoroethylene (TFE), perfluoro(methyl vinyl) ether (PMVE), a monomer containing nitrile curing sites, carbon black and a curing agent are mixed by a two-roll rubber mixer and formed into a sheet (300 square millimeters, 0.55-0.60 mm thickness) by calendering rolls.

[0114] Aromatic polyamide sheet: Nomex® fiber fabric NX-2245 from Teikoku Fibers Co., Ltd. (plain weave, 0.37 thickness, 45 threads / inch density, and 20 / 2 cotton count).

[0115] Fiberglass sheet: KS4325 (twill weave, 0.85mm thickness, 48 ​​threads / inch density) from Nittobog Co., Ltd.

[0116] FKM Sheet 1: A Solvay Tecnoflon® FOR 5351 / U grade fluoroelastomer composition (containing 72 wt.% polymer units with curing agent, 2 wt.% magnesium oxide units, 4 wt.% calcium hydroxide units and 22 wt.% carbon black units) is mixed using a two-roll rubber mixer and formed into a sheet (125 square millimeters, 0.5 mm thickness) using a pressing device.

[0117] FKM Sheet 2 (Commercial FKM / Fabric Material): A commercially available cushioning material product, KINYO-Board R225 from Kinyosha Co., Ltd.

[0118] Analytical methods

[0119] Compression test:

[0120] 1. Place the test sample in a tensile testing machine with compression clamps (Shimadzu Autograph AGS-5KNG).

[0121] 2. Compress the test sample at 1 mm / min at room temperature until a surface pressure of 3.5 MPa is reached. After reaching a surface pressure of 3.5 MPa, release the compression at 1 mm / min until a surface pressure of 0 MPa is reached.

[0122] 3. Heat the test sample and tensile testing machine to the target temperature and continue heating for 1 hour.

[0123] 4. Compress the test sample at the target temperature at a speed of 1 mm / min until a surface pressure of 3.5 MPa is reached, and then maintain the pressure at 3.5 MPa for 40 minutes.

[0124] 5. Release the compression at a rate of 1 mm / min until the surface pressure reaches 0 MPa.

[0125] After 6.5 minutes, repeat steps 4 and 5 above, and compress the sample for a total of 5 cycles.

[0126] 7. Remove the sample from the tensile testing machine and keep it at room temperature for 30 minutes. Then measure the thickness of the sample.

[0127] 8. Allow the tensile testing machine to cool to room temperature.

[0128] 9. Repeat steps 1 through 8, and compress the sample for a total of 20 cycles.

[0129] Thickness variation

[0130] The thickness of the test samples was measured before compression and after 5, 10, 15, and 20 compression cycles. Thickness retention was also calculated.

[0131] Size change

[0132] The dimensions of the test specimens in the vertical and width directions were measured before the compression test and after 20 compression test cycles. The dimensional increase rate (%) was also calculated to examine dimensional changes after the compression test.

[0133] Surface pressure change

[0134] During compression testing, the surface pressure was measured under compression at room temperature. The slope values ​​from 1.5 MPa to 3.5 MPa were calculated before compression and after 20 compression cycles.

[0135] Examples 1 and 2

[0136] FFKM sheets were cut into 125 mm² pieces, and aramid sheets were cut into 150 mm² pieces. Three aramid sheets and two FFKM sheets were stacked alternately. The stacked sheets were then heated at 170°C for 7 minutes at 40 tons using a pressing machine (PAN STONE HYDRAULIC INDUS.CO., LTD, model: PV-250-APCD), followed by heating in an oven at 305°C for 10 hours. Test samples were cut into 30 mm² pieces to prepare FFKM cushioning material test samples. The thickness of these test samples was 2.04 to 2.05 mm.

[0137] The compression test for Example 1 was conducted at 280°C, and the compression test for Example 2 was conducted at 300°C.

[0138] Compare Examples 1 and 2

[0139] FKM sheet 1 was cut into 125 mm² pieces, and aramid sheet 150 mm² pieces were cut. Three aramid sheets and two FKM sheets were stacked alternately. The stacked sheets were then heated at 170°C for 10 minutes at 40 tons using a pressing machine (Panyu Pressing Industry Co., Ltd., model: PV-250-A-PCD), followed by heating in an oven at 250°C for 8 hours. Test samples were cut into 30 mm² pieces to prepare FKM cushioning material test samples. The thickness of these test samples was 2.02 mm. Compression tests of the test samples in Comparative Example 1 were conducted at 280°C, and compression tests of the test samples in Comparative Example 2 were conducted at 300°C.

[0140] Compare Examples 3 and 4

[0141] FKM sheet 2 was cut into 30 square millimeter pieces to prepare FKM cushioning material test samples. The thickness of FKM sheet 2 was 2.30 mm. The compression test of the test sample in Comparative Example 3 was carried out at 280°C, and the compression test of the test sample in Comparative Example 4 was carried out at 300°C.

[0142] Compression test results:

[0143] Example 1: Surface appearance (photograph) of the test sample. Figure 9A and 9B As shown.

[0144] The dimensional variations are shown in Table 1, while the thickness variations are shown in Table 2.

[0145] Table 1

[0146]

[0147] Table 2

[0148]

[0149] FFKM sheets show almost no increase in size and maintain their original shape and dimensions. In contrast, FKM sheets (FKM sheet 1 and FKM sheet 2) increase in size and change shape, especially at 300°C. After 20 compression test cycles, the thickness of the FFKM sheet changes by 85% or more. Conversely, the thickness of the FKM sheet decreases after the compression test, and the thickness change is less than 85%. Therefore, FFKM sheets maintain a better thickness retention rate compared to FKM sheets.

[0150] The slope values ​​from 1.5 MPa to 3.5 MPa are shown in Table 3. The compressive stress curves for each test sample are shown below. Figures 1 to 7 As shown.

[0151] Table 3

[0152]

[0153] Due to mechanical factors and variations in the shape of each sample, data from the initial compression phase are expected to vary considerably. Data from compression to a certain extent (e.g., exceeding 1.5 MPa) are considered highly reliable, and then slope values ​​ranging from 1.5 MPa to 3.5 MPa are calculated.

[0154] The slope value of FFKM sheet remains almost unchanged from 1.5 MPa to 3.5 MPa, while the slope value of FKM sheet increases. This means that FKM sheet hardens and loses its cushioning ability at 280°C and 300°C.

[0155] Example 3

[0156] Glass fiber sheets were used instead of the aramid sheets in Example 2. The same procedure as in Example 2 was performed: three glass fiber sheets and two FFKM sheets were alternately stacked, and the stacked sheets were then pressed at 170°C for 7 minutes under 40 tons of pressure, followed by heating in an oven at 305°C for 10 hours. A pressing device (Panyu Pressing Industry Co., Ltd.), model: PV-250-APCD, was used. The thickness of the test samples ranged from 3.78 to 3.88 mm.

[0157] Compression tests were conducted at 300°C.

[0158] Table 4

[0159]

[0160] Similar to Examples 1-2, surface pressure was measured during the compression test, and the slope value was calculated. The results are shown in Table 5.

[0161] Table 5

[0162] .

Claims

1. A cushioning material for hot pressing, comprising at least two fabric sheets and at least one perfluoroelastomer sheet, the fabric sheets being located on the upper and lower sides of the perfluoroelastomer sheet, wherein the perfluoroelastomer sheet is formed from a perfluoroelastomer composition comprising: (A) A perfluoroelastomer, said perfluoroelastomer comprising copolymer units of the following: (i) One or more unsaturated perfluorinated olefins; (ii) One or more perfluorovinyl ethers selected from the group consisting of: perfluoro(alkylvinyl) ethers, perfluoro(alkoxyvinyl) ethers, and mixtures of perfluoro(alkylvinyl) ethers and perfluoro(alkoxyvinyl) ethers; (iii) One or more monomers with curing sites, selected from the group consisting of bromine atoms, iodine atoms and nitrile groups; (B) One or more curing agents, and (C) Optionally, one or more fillers may be used.

2. The cushioning material for hot pressing as described in claim 1, wherein, The fabric sheet is an aramid fiber sheet or a glass fiber sheet.

3. The cushioning material for hot pressing as described in claim 1, wherein, The cushioning material comprises at least three fabric sheets and at least two perfluoroelastomer sheets, wherein the fabric sheets and the perfluoroelastomer sheets are stacked alternately.

4. The cushioning material for hot pressing as described in claim 1, wherein, The thickness of the cushioning material is 0.5 to 10.0 mm.

5. The hot-pressing cushioning material as claimed in claim 1, wherein the thickness of the hot-pressing cushioning material is defined as T0, and the thickness of the cushioning material after undergoing 20 compression test cycles at 300°C and 3.5 MPa for 40 minutes is defined as T... 20 At that time, T 20 / T0 is greater than 0.

85.

6. A hot pressing apparatus for manufacturing printed circuit boards comprising PTFE resin and / or liquid crystal polymer, wherein the hot pressing apparatus comprises the cushioning material as claimed in claim 1.

7. A hot pressing apparatus for a manufacturing process of mounting power semiconductors on an insulating substrate, wherein the hot pressing apparatus includes the cushioning material as claimed in claim 1.

8. A method for manufacturing a cushioning material for hot pressing, the method comprising the following steps: (1) Prepare at least one perfluoroelastomer sheet, said perfluoroelastomer sheet being formed from a composition comprising the following: (A) A perfluoroelastomer, said perfluoroelastomer comprising copolymer units of the following: (i) One or more unsaturated perfluorinated olefins; (ii) One or more perfluorovinyl ethers selected from the group consisting of: perfluoro(alkylvinyl) ethers, perfluoro(alkoxyvinyl) ethers, and mixtures of perfluoro(alkylvinyl) ethers and perfluoro(alkoxyvinyl) ethers; and (iii) One or more monomers with curing sites, selected from the group consisting of bromine atoms, iodine atoms and nitrile groups; (B) One or more curing agents, and (C) Optionally, one or more fillers, (2) The perfluoroelastomer sheet is applied between two fabric sheets. (3) Hot-press these laminated sheets to bond the fabric sheet and the perfluoroelastomer sheet together, then (4) Further heat the hot-pressed laminated sheet to form crosslinks of the perfluoroelastomer.

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