Temporary bonding film

Abstract

A temporary bonding film includes a polyimide core film layer having a first surface and a second surface; a pressure sensitive adhesive layer disposed on the first surface of the polyimide core film layer; an epoxy thermoset adhesive layer disposed on the second surface of the polyimide core film layer; and a laser-releasable elastomeric layer disposed on the epoxy thermoset adhesive layer. In a preferred embodiment, the laser-releasable elastomeric layer comprises carbon black.

Description

[0001] TEMPORARY BONDING FILM Technical Field The present disclosure relates to a temporary bonding film comprising a polyimide core film layer, a pressure sensitive adhesive layer, an epoxy thermoset adhesive layer and a laser-releasable elastomeric layer. Background For wafer and panel level semiconductor packaging processes, temporary bonding films The temporary bonding films are disposed between a substrate to be processed and a supporter in a process of processing the substrate. A thin-film type substrate or a substrate having flexibility may be used. Rigid substrates being easy to distort at high temperatures may also be used. In a process where such a thin-film type substrate is formed or a substrate having flexibility is used, or when using substrates that cannot withstand high temperatures and can be distorted, a process of bonding the substrate to a hard supporter, and then separating the substrate from the hard supporter after processing of the substrate is completed has been suggested. However, it may be difficult to apply the flexible substrate to existing manufacturing equipment, due to its characteristic of being easily bent, and for example, the flexible substrate has difficulty in being conveyed by track equipment or a robot or being received in a cassette. Accordingly, the flexible substrate is bonded to a hard supporter before elements are formed, and the supporter supports the flexible substrate while elements are formed on the flexible substrate, and after the elements are formed on the substrate, the supporter is detached from the flexible substrate. In the process of separating the substrate from the hard supporter after processing the substrate, a wafer or the substrate itself may be destroyed, or a circuit of the wafer and an element of the flexible substrate may be destroyed. To overcome this disadvantage, US 2022 / 0372339 A1 proposes an adhesive film comprising a photothermal conversion layer comprising a light absorbing agent and a pyrolytic resin, a first adhesive layer disposed on the photothermal conversion layer, a base film layer, which is a PI film, disposed on the first adhesive layer, and a second adhesive layer disposed on the base film layer, wherein the first adhesive layer and the second adhesive layer comprise a silicon-based adhesive. The photothermal conversion layer is a laser releasable layer. After a desired semiconductor packaging process is performed, the supporter and the processed sustrate are separated by a laser. A disadvantage of the adhesive film of US 2022 / 0372339 A1 is that it is not easy to perfectly combin a sturdy PI film with a laser releasable layer which is a high molecular weight elastomer with low tack. Separation of layers may occur at high temperatures required for semiconductor processing, even though the layers seem to be tightly bound at room temperature. When the adhesive film is applied to a rapid heating process, or when it is applied to a large-area device, delamination of layers or voids between layers may occur. US 2019 / 0330504 A1 discloses a method for temporary bonding a workpiece and a substrate by an adhesive layer. A bonding step is performed, wherein the substrate and the workpiece are bonded by the adhesive layer. A processing step is performed, wherein the workpiece is processed. A debonding step is performed, wherein the adhesive layer is irradiated with a laser so as to separate the workpiece from the substrate. The adhesive layer is formed by an adhesive, the adhesive includes a polymer and a light absorbing material, wherein the polymer is polyimide or a copolymer of amic acid / imide. As the adhesive is applied on the workpiece or the substrate as a liquid material, it is difficult to apply the adhesive to a large area panel. Since the bonding adhesive and release adhesive are not composed separately, a chemical cleaning step for the adhesive residue is essentially required. US 2013 / 0071658 A1 discloses an adhesive composition comprising an adhesive component and a tetrazole compound. The adhesive composition can be used for an adhesive tape for application in a method for treating a semiconductor wafer. For debonding, the tetrazole releases nitrogen gas in response to UV light. Currently, there is a limit to thermal stability. As used herein, "a", "an", "the", "at least one" and "one or more" are used interchangeably. The term “comprise” shall include also the terms “consist essentially of” and “consists of”. Summary In a first aspect, the present disclosure relates to a temporary bonding film, comprising a polyimide core film layer, having a first surface and a second surface; a pressure sensitive adhesive layer disposed on the first surface of the polyimide core film layer; an epoxy thermoset adhesive layer disposed on the second surface of the polyimide core film layer; and a laser-releasable elastomeric layer disposed on the epoxy thermoset adhesive layer. The temporary bonding film disclosed herein can maintain high adhesion in the process of semiconductor processing, and allows a substrate fixed onto a supporter to be easily detached from the supporter after the semiconductor processing process. The temporary bonding film disclosed herein has a high thermal stability at the temperatures required for semiconductor packaging processes. Depending on the type of substrate that needs to be processed, the process temperature may be up to 250 °C. The temporary bonding film disclosed herein has a good chemical resistance and a good bonding performance and debonding performance. The temporary bonding film disclosed herein has a good resistance to delamination of its layers, and it has a low risk of voids being formed between layers. The temporary bonding film disclosed herein allows the debonding process from the supporter to be performed without damage to the substrate by mechanical stress. When using the temporary bonding film disclosed herein in a process of semiconductor processing, additional processes such as post-curing and surface treatment are not required during the bonding process. After performing the semiconductor processing process, removing of the temporary bonding film is possible by peeling off without chemical cleaning and without leaving a residue. The epoxy thermoset adhesive layer has an excellent adhesive strength to the laser- releasable elastomeric layer and to the polyimide core film layer. The epoxy thermoset adhesive layer has a sufficient adhesion to the laser-releasable elastomeric layer and to the polyimide core film layer even before the epoxy thermoset adhesive is cured. When the temporary bonding film disclosed herein is used in a high temperature process such as a semiconductor processing process, no problems of shrinkage or expansion are experienced. The temporary bonding film disclosed herein can be used for large area semiconductor packaging processes such as large area fan-out panel-level packaging (FOPLP) process. The temporary bonding film disclosed herein can also be used for through silicon vias (TSV) semiconductor processing process with high process temperature. Detailed Description There is still a need for a temporary bonding film which can maintain high adhesion in the process of semiconductor processing, and allows a substrate fixed onto a supporter to be easily detached from the supporter after the semiconductor processing process, and which has a high thermal stability and chemical resistance and a good bonding performance and debonding performance. Disclosed herein is a temporary bonding film, comprising a polyimide core film layer, having a first surface and a second surface; a pressure sensitive adhesive layer disposed on the first surface of the polyimide core film layer; an epoxy thermoset adhesive layer disposed on the second surface of the polyimide core film layer; and a laser-releasable elastomeric layer disposed on the epoxy thermoset adhesive layer. A “temporary bonding film” is an adhesive film that is used temporarily in a process of, e.g., semiconductor packaging, and that is removed after the process is completed. The temporary bonding film may also be referred to as temporary bonding and debonding (TBDB) film. The temporary bonding film is disposed between a substrate to be processed and a supporter in a process of processing the substrate. The process of processing the substrate may be a semiconductor packaging process. The temporary bonding film as disclosed herein is of a film type, and is formed by forming the pressure sensitive adhesive layer and the epoxy thermoset adhesive layer on the first and second surface of the rigid polyimide core film layer, respectively, and bringing the epoxy thermoset adhesive layer and the laser-releasable elastomeric layer into contact with each other. That is, the present disclosure forms one film having a multi-layered structure as an adhesive film, rather than directly coating a supporter and a substrate to be processed with a liquid material. In a subsequent process of processing the substrate, the pressure sensitive adhesive layer is bonded to the substrate, and the laser-releasable elastomeric layer is bonded to a hard supporter. The polyimide core film layer has a first surface and a second surface. The polyimide core film layer supports the pressure sensitive adhesive layer disposed on the first surface of the polyimide core film layer and the epoxy thermoset adhesive layer disposed on the second surface of the polyimide core film layer. The polyimide core film layer is a film of a hard material. The polyimide core film layer may make it easy to remove the pressure sensitive adhesive and the epoxy thermoset adhesive remaining on the substrate after the laser-releasable elastomeric layer is separated through laser projection after the processing process of the substrate is finished. The polyimide core film layer has an excellent heat resisting property and a low coefficient of thermal expansion (CTE). Generally, the polyimide core film layer has a CTE value less than or equal to about 25 x 10-6K-1.. The thickness of the polyimide core film layer may be from 25 µm to 100 µm, generally from 40 µm to 80 µm, and more generally from 50 µm to 75 µm. If the thickness of the polyimide core film layer is less than about 25 µm, the polyimide core film layer is so thin that a coating ability in a coating process is reduced and it is difficult to adjust the thickness. In addition, if the thickness of the polyimide core film layer exceeds about 100 µm, the overall thickness of the temporary bonding film becomes thicker and the temporary bonding film becomes rigid, and lamination or adhesion performance on the substrate and the supporter is reduced. On the first surface of the polyimide core film layer, a pressure sensitive adhesive layer is disposed. The pressure sensitive adhesive layer is used to fix the substrate. The pressure sensitive adhesive of the pressure sensitive adhesive layer may comprise a silicone. The silicone may comprise a radical curing silicone-based adhesive, or an addition curing silicone-based adhesive. The silicone-based pressure sensitive adhesive layer has excellent stability at high temperature and has an excellent heat resisting property. In addition, the silicone-based pressure sensitive adhesive layer may be softer than adhesive layers of other materials, for example, acrylic adhesive layers, so that lamination performance is excellent when the silicone-based pressure sensitive adhesive layer bonds a rigid material such as the substrate and the supporter. The silicone-based pressure sensitive adhesive layer allows the removal of the temporary bonding film only with a small force of about 40 gf / 25 mm without leaving a residue on a device such as the substrate at a high temperature higher than or equal to 150 °C. And, it is possible to remove the adhesive film with a force of about 200-300 gf / 25 mm at a temperature from 60 °C to 100 °C. In the case of an acrylic adhesive being used instead of the silicone-based pressure sensitive adhesive layer, cohesion is low at a high temperature and thus it is impossible to remove in this way. The acrylic adhesive leaves residues at a high temperature and the adhesive layer may melt or may be torn. On the second surface of the polyimide core film layer, a layer of an epoxy thermoset adhesive is disposed. The epoxy thermoset adhesive layer is used to bond the polyimide core film layer and the laser-releasable elastomeric layer to each other. If the epoxy thermoset adhesive layer is omitted and the laser-releasable elastomeric layer and the polyimide core film layer are directly bonded to each other, there is a problem that detachment may occur at a temperature high than or equal to about 230 °C. The layer of the epoxy thermoset adhesive can enhance lamination performance of the laser-releasable elastomeric layer and the polyimide core film layer and increase adhesion of the laser-releasable elastomeric layer and the polyimide core film layer at high temperature, thereby enabling a high-temperature process. That is, the epoxy thermoset adhesive layer is a layer that contacts the laser-releasable elastomeric layer and has excellent adhesion. In the case of a silicone adhesive being used instead of an epoxy thermoset adhesive, when the temporary bonding film is used in a rapid heating process, or when the temporary bonding film is applied to a large-area device with high stress, there is a risk of delamination and voids between layers, i.e., between the silicone adhesive and the laser-releasable elastomeric layer. After the substrate and the supporter are separated from each other by division of the laser-releasable elastomeric layer, the substrate bonded with the pressure sensitive adhesive layer is obtained. Accordingly, the pressure sensitive adhesive layer should be easily separated from the substrate by detachment, etc. The pressure sensitive adhesive layer is a film type formed on the polyimide core film layer and is not a photo-curable adhesive that is directly coated on the substrate. The epoxy thermoset adhesive layer comprises an epoxy thermoset adhesive. The epoxy thermoset adhesive comprises an epoxy resin, a curing agent, and a binder. The epoxy thermoset adhesive typically further comprises a solvent, to enable coating of the epoxy thermoset adhesive on the second surface of the polyimide core film layer. The solvent may be an organic solvent, generally a polar organic solvent. The solvent may be selected from the group consisting of isopropyl alcohol, methyl ethyl ketone, ethyl acetate, ethanol, methanol, acetone, and combinations thereof. Minor amounts of aromatic organic solvents such as toluene may be added to polar solvents such as methyl ethyl ketone and ethyl acetate. In some embodiments, the solvent does not comprise an aromatic organic solvent. The boiling point of the solvent may be 50 °C or more and 100 °C or less. The solids content of the epoxy thermoset adhesive, i.e., the content of epoxy resin, curing agent, binder, and other solid components if present, may be from 10 to 25 percent by weight, based on the total weight of the epoxy thermoset adhesive. The epoxy thermoset adhesive may comprise up to 55 percent by weight of the binder, based on the total solids content of the epoxy thermoset adhesive. The epoxy thermoset adhesive may comprise at least 35 percent by weight, generally at least 40 percent by weight of the binder, based on the total solids content of the epoxy thermoset adhesive. Typically, the epoxy thermoset adhesive comprises from about 40 percent by weight to about 50 percent by weight of the curing agent, based on the sum of the weight of the epoxy resin and of the weight of the curing agent. The weight ratio of the sum of the amount of the epoxy resin and the curing agent to the amount of the binder that are comprised in the epoxy thermoset adhesive, i.e., the ratio (weight of epoxy resin plus weight of curing agent) : (weight of binder), may be from 1 : 9 to 9 : 1, generally from 2 : 8 to 8 : 2, more generally from 4 : 6 to 6 : 4. When the weight ratio is too high, i.e., when the amount of epoxy resin and curing agent is too large, and the amount of binder is too low, distortion may occur when the temporary bonding film is used at high temperatures. Conversely, when the weight ratio is too low, i.e., when the amount of epoxy resin and curing agent is too small, and the amount of binder is too high, heat resistance will not be sufficient. The weight ratio of the sum of the amount of the epoxy resin and the curing agent to the amount of the binder that are comprised in the epoxy thermoset adhesive, i.e., the ratio (weight of epoxy resin plus weight of curing agent) : (weight of binder), may also be referred to as the “epoxy ratio”. The epoxy resin that is comprised in the epoxy thermoset adhesive may be selected from the group consisting of phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, dicyclopentadiene (DCPD) novolac epoxy resins, bisphenol F (BPF) epoxy resins, bisphenol A (BPA) epoxy resins, and combinations thereof. Suitable epoxy resins are YDPN-631, YDPN-638, YDPN-641, YDCN-500-4P, YDCN-500- 8P, YDCN-500-80P, YDCN-500-90P, YD-128, YD-170, and YD-8128, available from Kukdo Chemical, South Korea; Epicon N740, Epicon N680, and Epicon N865, available from DIC Corporation, Japan; and KEB-3165, KED-3170, KEB-3180, KE-8120, KF-8100, NK's XD-10002L, XD-1000, XD-1000H, NC-3000, and NC-3000H, available from Kolon Industries, South Korea. The epoxy resin that is comprised in the epoxy thermoset adhesive may comprise a two- functional epoxy resin that has two terminal epoxide functional groups, i.e., one epoxide functional group at each end of the epoxy resin molecule. Examples for two-functional epoxy resins are bisphenol F (BPF) epoxy resins and bisphenol A (BPA) epoxy resins. The epoxy resin that is comprised in the epoxy thermoset adhesive may comprise a polyfunctional epoxy resin. As used herein, a “polyfunctional epoxy resin” is an epoxy resin that comprises at least three epoxide functional groups in the epoxy resin molecule, i.e., one epoxide functional group at each end of the epoxy resin molecule and at least one further epoxy functional group in the epoxy resin molecule. The term “epoxide group” refers to a functional and highly reactive group comprised of two carbons and an oxygen in a ring formation, also known as oxirane group. The polyfunctional epoxy resin may comprise three epoxide functional groups in the epoxy resin molecule, or four epoxide functional groups in the epoxy resin molecule, or five (or more) epoxide functional groups in the epoxy resin molecule. Combinations of epoxy resin molecules having different numbers of epoxy functional groups are also possible. Generally, the polyfunctional epoxy resin comprises three epoxide groups in the epoxy resin molecule. The epoxy resin that is comprised in the epoxy thermoset adhesive may also comprise a combination of several two-functional and / or polyfunctional epoxy resins, such as a combination of a two-functional epoxy resin and a polyfunctional epoxy resin comprising three epoxide groups, or a combination of a polyfunctional epoxy resin comprising three epoxide groups and a polyfunctional epoxy resin comprising four epoxide groups. By curing of the polyfunctional epoxy resin, highly cross-linked polymers are formed from the epoxy resin molecules due to the high functionality. Examples for polyfunctional epoxy resins are novolac resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, and dicyclopentadiene (DCPD) novolac epoxy resins. Without wishing to be bound by theory, the use of a polyfunctional epoxy resin helps improve the coating and adhesion performance of the epoxy thermoset adhesive and reduces the film shrinkage at high temperature after coating. The softening point of the epoxy resin may be at most 70 °C, generally at most 65 °C. Using an epoxy resin with a softening point of at most 70 °C helps to provide a high tackiness at room temperature. If the softening point of resin is at most 70 °C, the tackiness at room temperature is high and an excellent adhesion to the polyimide core film layer is provided. The softening point of the epoxy resin can be seen as the temperature of the starting point for the solid phase of the epoxy resin to become sticky. The softening point of the epoxy resin may be measured by a VST (Vicat Softening Temperature) equipment. When the temperature of a sample of epoxy resin is raised, the resin is softened slowly, and the temperature when it penetrates through a flattened needle with a tip of 1 mm² by about 1mm can be defined as the softening point. For two-functional epoxy resins, i.e., for epoxy resins comprising only two terminal epoxide functional groups, a liquid epoxy resin with a softening point lower than room temperature (23 °C) can be used. For two-functional epoxy resins, the curing profile should be set slowly to ensure uniform surface roughness of the epoxy thermoset adhesive after curing. The curing agent for use herein is selected from the group consisting of amine-based curing agents, phenol-based curing agents, anhydride curing agents, peroxide curing agents, imidazole curing agents, and combinations thereof. Generally, the curing agent is a phenol-based curing agent. It is also possible to use curing catalysts such as imidazole curing catalysts in addition to the curing agent. As an example, phenol may be used as curing agent and small amounts of imidazole as curing catalyst may be added. Suitable curing agents are dicyandiamide (DICY), phenol novolac resins, xylok type phenolic resins, imidazole, organic peroxides, and combinations of these. Generally, phenol novolac resins, xylok type phenolic resins, imidazole and combinations thereof may be used. For example, PN-23, MY-24, and AH-154, available from Ajinomoto, Japan; MEH-7800SS, MEH-78004S, and MEH-7800S, available from Meiwa Corporation, Japan; KPH-F3060, KPH-F3065, KPH-F3075, KPH-F2001, KPH- F2002, and KPH-F2003, available from Kolon Industries, South Korea; 2PHZ-PW, 2PZ-CN, 2PZ-OK, 2MA-OK, 2E4MZ, and 2E4MZ-CN, available from Shikoku Chemical Corporation, Japan; and biphenyl peroxide, available from Hansol Chemical, South Korea. The onset point of curing of the epoxy thermoset adhesive used herein may be at least 70 °C and at most 180 °C, or at least 140 °C and at most 160 °C. For example, the onset point of curing may be 70 °C, or 80 °C, or 100 °C, or 120 °C, or 140 °C, or 170 °C. The onset point of curing may be measured by differential scanning calorimetry (DSC). The peak point of curing may be at least 80 °C and at most 170 °C. If the onset point is below 120 °C, the temporary bonding film may shrink due to rapid curing and the roughness of the coating surface deteriorates during application and drying on the polyimide core film layer. On the other hand, if the on-set point is higher than 180 °C, curing may not be achieved as expected, which may cause deterioration of other properties such as heat resistance and adhesion. In addition, if the peak point is too high, sufficient curing may not be achieved as desired, which may lead to a decrease in heat resistance and adhesive strength. The binder that is comprised in the epoxy thermoset adhesive may comprise at least one of a rubber-based elastomer and an acrylic-based elastomer. The acrylic-based elastomer may comprise an acrylic polymer made by polymerization of at least one acrylic monomer selected from the group consisting of ethyl acrylate, butyl acrylate, glycidyl methacrylate, acrylic acid, acrylonitrile, and combinations thereof. For example, the acrylic-based elastomer may comprise a combination of ethyl acrylate, butyl acrylate and glycidyl methacrylate. Suitable acrylic-based elastomers are, for example, SG-80H, SG-P3, SG-708-6, and WS-023, available from Nagase & Co., Ltd., Japan; CS- 200, available from Negami Chemical Industrial Co., Ltd., Japan; and KNB-35N, KNB- 35H, KNB-40M, and KNB-40H, available from Kumho Petrochemical Co., Ltd., South Korea. The molecular weight (Mw) of the acrylic polymer may be from 300,000 to 1.2 million, generally from 500,000 to 1 million. When the molecular weight is too low, the thermal resistance is insufficient, and when it is too high, it is difficult to apply and manufacture the film. The acrylic polymer that is comprised in the acrylic-based elastomer may comprise polar functional groups, i.e., the acrylic polymer includes polar functional groups in the polymer backbone. The polar functional groups may be selected from the group consisting of nitrile groups, carboxyl groups, hydroxyl groups, glycidyl groups, amine groups, and combinations thereof. Generally, the polar functional groups are carboxyl groups and / or hydroxyl groups, and the acrylic polymer may comprise at least 1 mg KOH / g polymer of polar functional groups. More generally, the polar functional groups are carboxyl groups and / or hydroxyl groups, and the acrylic polymer comprises between 1 and 25 mg KOH / g polymer of polar functional groups. The polar functional groups may be carboxy groups and / or hydroxyl groups, and the acrylic polymer may comprise between 10 and 25 mg KOH / g polymer, or between 15 and 25 mg KOH / g polymer of polar functional groups. The amount of the polar functional groups may be measured by an acid-base titration. When the amount of the polar functional groups in the acrylic polymer is below 1 mg KOH / g polymer, the adhesion or tackiness to the polyimide core film layer can be significantly reduced. The binder that is comprised in the epoxy thermoset adhesive may have a glass transition temperature at least -20 °C and at most 60 °C. If the glass transition temperature is above 60 °C, adhesiveness and coating properties are lowered, and if it is below -20 °C, problems arise in thermal stability and film formation. The thickness of the epoxy thermoset adhesive layer may be from 10 to 45 µm. If the thickness is below 10 µm, the adhesive force may be reduced, and if the thickness is above 45 µm, the uniformity of the surface is decreased during the coating and voids may occur when the solvent is dried. Generally, the thickness is in the range of 20 to 40 µm. The thickness of the pressure sensitive adhesive layer may be from 20 µm to 100 µm, generally, from 30 µm to 75 µm, more generally, from 50 µm to 75 µm. A higher thickness of the pressure sensitive adhesive layer may be advantageous for thermal stability. The thicker the pressure sensitive adhesive layer, the higher the adhesion. If the thickness is below 20 µm, the adhesion is too low and can cause delamination during high temperature processes, and when removed, the resin may tear and leave a residue. The temporary bonding film disclosed herein comprises a laser-releasable elastomeric layer disposed on the epoxy thermoset adhesive layer. The laser-releasable elastomeric layer is divided when radiant energy such as a laser is projected, so that the substrate can be separated from the supporter without damaging the substrate or an element or a circuit on the substrate. The laser-releasable elastomeric layer may include a light absorbing agent and a pyrolytic resin. Radiant energy applied to the laser-releasable elastomeric layer in the form of a laser is absorbed by the light absorbing agent and is converted into thermal energy. The generated thermal energy abruptly increases a temperature of the laser-releasable elastomeric layer, and the temperature reaches a pyrolysis temperature of the pyrolytic resin (organic component) in the laser-releasable elastomeric layer, causing pyrolysis of the resin. A gas generated by the pyrolysis forms an opening layer (such as a space) in the laser-releasable elastomeric layer and divides the laser-releasable elastomeric layer into two portions, and accordingly, the supporter and the substrate are separated. The light absorbing agent may absorb radiant energy and may convert the radiant energy into thermal energy. In addition, the light absorbing agent functions to block light and can prevent the substrate from being damaged by a laser, etc. Although the light absorbing agent changes dependently on a wavelength of the laser, examples of a usable light absorbing agent include carbon black, graphite powder, ultra- fine metal powder such as iron, aluminum, copper, nickel, cobalt, manganese, chrome, zinc, and tellurium, metallic oxide powder such as black titanium oxide, and dye and pigment such as aromatic diamino-based metal complex, aliphatic diamine-based metal complex, aromatic dithiol-based metal complex, mercaptophenol-based metal complex, squarylium-based compound, a cyanine-based dye, methine-based dye, napthoquinone- based dye and anthraquinone-based dye. The light absorbing agent may be in the form of a film including a vapor-deposited metal film. From among the light absorbing agents, carbon black is in particular useful since carbon black noticeably reduces a force necessary for separating the substrate from the supporter after projection, and accelerates separation. A particle size of the light absorbing agent in the laser-releasable elastomeric layer may be about 20 nm to about 2000 nm, generally, may be about 50 nm to about 1000 nm, and more generally, may be about 100 nm to about 350 nm. If the particle size of the light absorbing agent is less than about 20 nm, it may be difficult to disperse, and a larger amount of light absorbing agent may not be loaded because a surface area increases as a particle size is smaller, and there is a limit to a loading content. In addition, if the particle size of the light absorbing agent exceeds about 2000 nm, laser blocking performance may be reduced, and performance of dividing the laser- releasable elastomeric layer by a laser may be reduced. In addition, as a particle size of the light absorbing agent increases, a film forming ability may be reduced, and dispersion stability after dispersion may be reduced. A content of the light absorbing agent in the laser-releasable elastomeric layer may be about 5 percent by weight to about 80 percent by weight, based on the total weight of the laser-releasable elastomeric layer, generally, may be about 10 percent by weight to about 60 percent by weight, and more generally, may be about 20 percent by weight to about 50 percent by weight, based on the total weight of the laser-releasable elastomeric layer. If the content of the light absorbing agent is less than about 5 percent by weight, it is difficult to separate by a laser. In addition, if the content of the light absorbing agent exceeds about 80 percent by weight, a portion of the laser-releasable elastomeric layer separated by the laser remains on the surface of the epoxy thermoset adhesive layer after the laser-releasable elastomeric layer is separated by the laser, and in this case, adhesion may be very low due to a high content of carbon. In this case, there is a problem that in a process of removing the epoxy thermoset adhesive layer, the polyimide core film layer, and the pressure sensitive adhesive layer by removal tape, the portion of the laser-releasable elastomeric layer is not well attached to the removal tape and is difficult to remove. In addition, as the content of the light absorbing agent increases, adhesion of the surface of the laser-releasable elastomeric layer becomes lower and it is difficult to laminate on the supporter and dispersion of the light absorbing agent is not uniform. The pyrolytic resin in the laser-releasable elastomeric layer may include an acrylic resin. The acrylic resin typically is an acrylic-based elastomer. Generally, the acrylic resin includes a monomer selected from the group consisting of methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), ethyl acrylate (EA), butyl acrylate (BA), acrolonitrile (AN), and a combination thereof. Generally, the monomer may be selected from a combination of three or more of methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), ethyl acrylate (EA), butyl acrylate (BA), and acrylonitrile (AN). Such an acrylic resin may have an appropriate molecular weight, Tg, a heat-resisting property, and a functional group. A content of the acrylic resin may be about 5 percent by weight to about 80 percent by weight, based on the total weight of the laser-releasable elastomeric layer, generally, may be about 15 percent by weight to about 60 percent by weight, and more generally, may be about 40 percent by weight to about 60 percent by weight, based on the total weight of the laser-releasable elastomeric layer. If the content of the acrylic resin is less than about 5 percent by weight, a film forming ability is reduced and it is difficult to adjust a thickness of the laser-releasable elastomeric layer, and it is difficult to laminate on the supporter since adhesion of the surface of the laser-releasable elastomeric layer is very low. In addition, if the content of the acrylic resin exceeds about 80 percent by weight, a great physical force is required when the laser- releasable elastomeric layer is divided after laser projection, and it may be difficult to separate the substrate and the supporter, and the substrate and an element or a circuit formed on the substrate may be damaged. The pyrolytic resin in the laser-releasable elastomeric layer has a –COOH or –OH functional group. Generally, the pyrolytic resin includes an acrylic resin having the –COOH or –OH functional group. The laser-releasable elastomeric layer including the pyrolytic resin having the –COOH or –OH functional group is not a pressure-sensitive adhesive type. The laser-releasable elastomeric layer has the –COOH or –OH functional group, such that the laser-releasable elastomeric layer can be bonded with the supporter by hydrogen bonding, and, for example, may be hydrogen-bonded with a silanol group on a glass surface of the supporter formed with glass. In this case, the hydrogen bonding provides initial adhesion to bond the laser-releasable elastomeric layer to the supporter, and stickiness between the laser-releasable elastomeric layer and the supporter may greatly increase due to heat generated in a process after the bonding process. The –COOH or –OH functional group may have an acid value greter than or equal to about 1 mg KOH / g, generally, greater than or equal to about 5 mg KOH / g. The lamination performance of the laser-releasable elastomeric layer is based on the –COOH or –OH functional group, and, if the acid value of the –COOH or –OH functional group is lower than about 1 mg KOH / g, the lamination performance is reduced. An upper limit of the acid value of the –COOH or –OH does not bring about a problem. However, due to a chemical structure, the acid value may generally have about 1 mg KOH / g to about 50 mg KOH / g, more generally, about 1 mg KOH / g to about 30 mg KOH / g, and most generally, about 10 mg KOH / g to about 20 mg KOH / g. The laser-releasable elastomeric layer may further include an inorganic filler. The inorganic filler functions to prevent the laser-releasable elastomeric layer from being re- bonded after the laser-releasable elastomeric layer is divided due to the opening layer formed as a result of pyrolysis of the pyrolytic resin. Accordingly, when the laser- releasable elastomeric layer is separated by projecting a laser after the substrate is processed, a physical force required to separate the substrate and the supporter may be additionally reduced. The inorganic filler may be selected from the group consisting of SiO2, Al2O3, TiO2and a combination thereof. Generally, the inorganic filler may comprise at least one of titania or silica. In particular, in the case of TiO2, there is an additional light blocking effect on the substrate. The inorganic filler may comprise at least one of alumina-coated titania or silica. The particle size of the inorganic filler in the laser-releasable elastomeric layer may be about 20 nm to about 2000 nm, generally, may be about 50 nm to about 1000 nm, and mor generally, may be about 100 nm to about 350 nm. If the particle size of the inorganic filler is less than about 20 nm, it is not easy to disperse the inorganic filler wehen the film is made, and there is a limit to an amount to be loaded. In addition, if the particle size of the inorganic filler exceeds about 2000 nm, the film forming ability is reduced and dispersion persistance after dispersion may be reduced. The content of the inorganic filler in the laser-releasable elastomeric layer may be about 4 percent by weight to about 60 percent by weight, based on the total weight of the laser- releasable elastomeric layer, generally, may be about 5 percent by weight to about 50 percent by weight, and more generally, may be about 5 percent by weight to about 30 percent by weight, based on the total weight of the laser-releasable elastomeric layer. If the content of the inorganic filler is less than about 4 percent by weight, adhesion on the surface separated after the separation process by laser projection is strong, and the laser- releasable elastomeric layer may be re-bonded as time is elapsed. In addition, if the content of the inorganic filler exceeds about 60 percent by weight, the adhesion of the laser-releasable elastomeric layer is very low and it is difficult to laminate on the supporter, and the film forming ability is reduced and dispersion is not uniform. The laser-releasable elastomeric layer may further include a dispersing agent. A content of the dispersing agent may be about 0.1 percent by weight to about 10 percent by weight, based on the total weight of the laser-releasable elastomeric layer, generally, may be about 0.1 percent by weight to about 7 percent by weight, and more generally, may be about 0.1 percent by weight to about 5 percent by weight, based on the total weight of the laser-releasable elastomeric layer. If the content of the dispersing agent is less than about 0.1 percent by weight, dispersion of the light absorbing agent and the inorganic filler in the laser-releasable elastomeric layer may be reduced, and dispersion persistence after dispersion may also be reduced. In addition, if the content of the dispersing agent exceeds about 10 percent by weight, the heat resisting property of the laser-releasable elastomeric layer may be reduced. The thickness of the laser-releasable elastomeric layer may be about 1 µm to about 30 µm, generally, may be about 3 µm to about 20 µm, and more generally, may be about 5 µm to about 15 µm. If the thickness of the laser-releasable elastomeric layer is less than about 1 µm, an upper adhesive layer may directly influence the material, and laser blocking performance by the light absorbing agent may be reduced. In addition, if the thickness of the laser-releasable elastomeric layer exceeds about 30 µm, many adhesive residues may remain on the supporter after laser projection. The laser-releasable elastomeric layer may have adhesion of 150 gf / 25 mm to 3200 gf / 25mm with respect to the supporter. The temporary bonding film disclosed herein may further comprise a first liner disposed on the pressure sensitive adhesive layer opposite the polyimide core film layer. The temporary bonding film disclosed herein may further comprise a second liner disposed on the laser-releasable elastomeric layer opposite the epoxy thermoset adhesive layer. The first liner and the second liner sever to support and to protect the laser-releasable elastomeric layer and the pressure sensitive adhesive layer, respectively. The first liner and the second liner may be removed when the temporary bonding film is used. The first liner and the second liner may be silicone-coated or fluorinated polyethylene terephthalate (PET), but it is not limited thereto and any material to support and protect the adhesive film can be used. The temporary bonding film disclosed herein may be produced by a process comprising providing a polyimide core film layer, having a first surface and a second surface; casting of a laser-releasable elastomeric layer; coating a pressure sensitive adhesive layer on the first surface of the polyimide core film layer; coating an epoxy thermoset adhesive layer on the second surface of the polyimide core film layer; laminating the laser-releasable elastomeric layer on the layer of the epoxy thermoset adhesive, thereby obtaining the temporary bonding film. All the specific details of the polyimide core film layer, of the laser-releasable elastomeric layer, of the pressure sensitive adhesive layer, and of the epoxy thermoset adhesive layer as described above in the context of the temporary bonding film apply here as well. All casting, coating and laminating steps of the process for producing the temporary bonding film may be performed as a continuous roll-to-roll process. However, the process for producing the temporary bonding film disclosed herein is not limited to a continuous roll-to-roll process, and any method that can laminate a plurality of layers of an adhesive film can be applied. Coating a pressure sensitive adhesive layer on the first surface of the polyimide core film layer comprises applying a pressure sensitive adhesive on the first surface of the polyimide core film layer and drying it. Coating the epoxy thermoset adhesive layer on the second surface of the polyimide core film layer comprises mixing of the epoxy resin, the curing agent and the binder and applying the obtained adhesive mixture as a layer on the second surface of the polyimide core film layer. After applying the layer of the adhesive mixture on the second surface of the polyimide core film layer, the layer of the adhesive mixture is dried and cured at a temperature of from 120 °C to 170 °C, generally at about 145 °C. After curing and drying the applied adhesive, the prepared laser-releasable elastomeric layer is laminated on it. Laminating the laser-releasable elastomeric layer on the epoxy thermoset adhesive layer may be performed by using a heating roll at a temperature of from 50 °C to 100 °C, generally at about 80 °C. The first surface of the polyimide core film layer may be treated with a primer before coating the pressure sensitive adhesive layer on the first surface, i.e., a primer layer may be disposed on the first surface of the polyimide core film layer. The primer treatment may increase the adhesion of the polyimide core film layer to the pressure sensitive adhesive layer. The primer layer may include an addition curing resin, a platinum catalyst, and a cross- linking agent. The primer layer may be cured at a temperature higher than or equal to about 140 °C. The thickness of the primer layer may be from 50 nm to 500 nm, generally from 50 nm to 300 nm, more generally from 100 nm to 300 nm. The second surface of the polyimide core film layer may be surface treated, for example by a Corona treatment, an atmospheric plasma treatment, or a wet treatment using KOH aqueous solution (0.1 - 3M). Combinations of these surface treatments may also be applied. By the surface treatment, the adhesion of the polyimide core film layer to the epoxy thermoset adhesive layer may be increased. The process of producing the temporary bonding film disclosed herein may further comprise chemically stabilizing the temporary bonding film. The step of chemically stabilizing the temporary bonding film is performed after laminating the laser-releasable elastomeric layer on the epoxy thermoset adhesive layer. By the step of chemically stabilizing the temporary bonding film, all four film layers of the four-layered film are chemically stabilized. The step of chemically stabilizing the temporary bonding film may be performed by aging for a certain period of time at 45 °C. Typically, the step of chemically stabilizing the temporary bonding film is performed for about 12 hours to 24 hours. The step of chemically stabilizing the temporary bonding film may help avoiding cracks which may occur due to shrinkage by rapid curing when the temporary bonding film is introduced into a process accompanied by some rapid temperature rise. Furthermore, for the pressure sensitive adhesive layer, the step of chemically stabilizing the temporary bonding film may help avoiding residues which might be not desired in high temperature processes. After coating the pressure sensitive adhesive layer on the first surface of the polyimide core film layer, the pressure sensitive adhesive layer may be protected by a liner disposed on the pressure sensitive adhesive layer opposite the polyimide core film layer. The liner may be, for example, a PET liner. The PET liner may be silicone-coated or fluorinated. After laminating the laser-releasable elastomeric layer on the epoxy thermoset adhesive layer, the laser-releasable elastomeric layer may be protected by a liner disposed on the laser-releasable elastomeric layer opposite the epoxy thermoset adhesive layer. The liner may be, for example, a PET liner. The PET liner may be silicone-coated or fluorinated. Examples Test methods Observation of defects occurring during coating Coating performance of the epoxy thermoset adhesive on the polyimide core film layer was evaluated by visual inspection of issues and defects occurring during coating. Adhesion testing Adhesion / tackiness of the epoxy thermoset adhesive layer to the laser-releasable elastomeric layer and to the polyimide core film layer was tested. The adhesion was verified through a 180° peel off test. First, the laser-releasable elastomeric layer side of the prepared sample of temporary bonding film was laminated to a glass specimen with a temperature of 70 °C. Then the sample was gripped and peeled forcibly, and the fracture tendency of the temporary bonding film was observed. For all samples, the delamination occurred at the interface between the epoxy thermoset adhesive layer and the polyimide core film layer. Adhesion was evaluated before and after curing. Thermal stability testing Thermal stability was evaluated by a 230 °C oven test and a 180 °C hotplate test. After bonding two glass sheets by the prepared temporary bonding film sample, the delamination or void generated during the high temperature process was visually observed. The 230 °C oven test is an evaluation method that simulates the curing process of the passivation layer during the redistribution layer (RDL) build-up. The RDL process is a semiconductor packaging process. The 180 °C hotplate test is an evaluation method that simulates the metal deposition process of the fan-out process during the RDL build- up. For the 230 °C oven test (glass to wafer bonding), samples were prepared by bonding a glass carrier (disc with diameter 12 inches) and an EMC (epoxy molding compound) molded wafer (round wafer (disc) with diameter 12 inches) to a temporary bonding film sample. The glass carrier was bonded to the laser-releasable elastomeric layer side of the temporary bonding film, and the EMC molded wafer was bonded to the pressure-sensitive adhesive layer side of the temporary bonding film. The prepared samples (of the temporary bonding film bonded to the glass carrier and the EMC molded wafer) were placed in an oven at room temperature (23 °C), and the oven was heated up to 230 °C, with a ramp-up being adjusted so that the temperature raised in 1 hour and 30 minutes from room temperature (23 °C) to 230 °C. The prepared samples were kept for 2 hours at 230 °C to simulate aging. The aged samples were slowly cooled down to 100 °C, and then the samples were taken out of the oven. Afterwards, the state of the samples was observed. Generally, EMC molded wafers cause large warpage at high temperatures, which means that delamination may occur if the temporary bonding film does not have strong adhesion and excellent thermal stability. For the 180 °C hotplate test (glass to glass bonding), samples of the temporary bonding film were bonded with a glass carrier (disc with diameter 8 inches) on each side, i.e., one of the two glass carriers was bonded to the pressure sensitive adhesive layer side of the temporary bonding film, the other one of the two glass carriers was bonded to the laser- releasable elastomeric layer side of the temporary bonding film. The prepared samples (of the temporary bonding film bonded to the two glass carriers) were placed directly on a 180 °C hotplate (with the side of the laser-releasable elastomeric layer) without ramp-up and were kept at 180 °C for 30 minutes, thereby simulating an aging process. The samples were observed during this time to see if changes or defects such as void delamination occur. Materials Used in the Examples Material Description Novolac epoxy resin, available from Kukdo Chemical Co., YDCN-500-4P Ltd., South Korea Novolac epoxy resin, available from Kukdo Chemical Co., YDCN-500-8P Ltd., South Korea Epoxy resin, available from Kukdo Chemical Co., Ltd., YD-128 South Korea Epoxy resin, available from Kukdo Chemical Co., Ltd., YD-170 South Korea Curing agent, novolac phenolic resin, available from Kolon KPH-F2001 Industries, South Korea Curing agent, novolac phenolic resin, available from Kolon KPH-F3060 Industries, South Korea Curing catalyst, available from Shikoku Chemicals 2PHZ-PW Corporation, Japan Curing catalyst, imidazole, available from Shikoku 2E4MI Chemicals Corporation, Japan Binder, acrylonitrile-butadiene rubber (NBR), available from KNB-40H Kumho Petrochemical Co., Ltd., South Korea Binder, acrylonitrile-butadiene rubber (NBR), available from KNB-40M Kumho Petrochemical Co., Ltd., South Korea Binder, acrylic elastomer resin, available from Nagase SG-P3 Chemtex Corporation, Japan Binder, acrylic elastomer resin, available from Nagase SG-708-6 Chemtex Corporation, Japan Examples 1 to 16 (EX1 to EX16) For Examples 1 to 16, temporary bonding films were prepared according to the procedures of Manufacturing Examples 1 to 7 as described hereinafter. Manufacturing Example 1 - Manufacturing of laser-releasable elastomeric layer mixture A pre-mix carbon solution is prepared as follows: To 100 g of organic solvent (95 wt.-% polar solvent (ethyl acetate / methyl ethyl ketone 50:50), 5 wt.-% aromatic solvent (toluene)), 6.66 g of carbon black from Cabot Corporation, USA, with a particle size of 250 nm and 2.53 g of alumina-coated titania powder (Huntsman) with a particle size of 250 nmare added. Then, 3 g of a polymeric type dispersant (HypermerTM KD6 supplied by CrodaInternational Plc, UK) is added and mixed for 10 minutes using a stirrer. For dispersion, a milling machine is used for more than 30 minutes. In order to control heat generation during milling, a cooler is used so that the temperature can be managed below 40 °C. As a milling machine, all kinds of machines such as nano mill, basket mill, Horn type sonication equipment that can disperse in nm are applicable. Then, 20 g of the acrylic elastomer resin SG-708-6 (supplied by Nagase Chemtex Corporation) is added to the pre- mix carbon solution and dispersed again using a mill for 30 to 45 minutes. Manufacturing Example 2 - Casting of laser-releasable elastomeric layer The mixture of Manufacturing Example 1 is applied onto a 50 µm PET liner then the solvent is dried for 2 min at 90 °C to complete the laser-releasable film layer so that it has a thickness of 5 to 15 µm after drying. Manufacturing Example 3 - Manufacturing of pressure sensitive (silicone) adhesive mixture 2.28 g of a biphenyl-based peroxide curing agent is added to 80 g of an aromatic polar solvent (95 wt.-% of toluene, 5 wt.-% of xylene) followed by stirring to completely dissolve the curing agent. After dissolution is complete, add 100 g of condensation reaction type silicone adhesive (DowsilTMQ2-7406 from Dow Chemical) and stir for 20 minutes. After the stirring is completed, the degassing process is performed for 30 minutes. Manufacturing Example 4 - Coating of pressure sensitive adhesive layer on first surface of PI core film The mixture of Manufacturing Example 3 is applied on a 25 µm polyimide film (supplied by PI Advanced Materials Co., Ltd., South Korea) so that the thickness becomes 50 µm after drying. After application, it is dried and cured at 185 °C for 3 minutes to complete the adhesive coating. Comma roll has been used for coating. Slot die / lip die can also be used for coating. Before coating the polyimide film with the mixture of Manufacturing Example 3, primer coating has been applied on the polyimide film. Manufacturing Example 5 - Manufacturing of epoxy thermoset adhesive mixture 30 g of epoxy resin, 20 g of solid curing agent, and 100 g of organic solvent (95 wt.-% polar solvent (methyl ethyl ketone or ethyl acetate), 5 wt.-% aromatic solvent (toluene)) are mixed for 20 minutes at room temperature (23 °C). After adding 50 g of binder to the prepared solution, stir at 10 rpm for 30 minutes. For Example 1, epoxy resin, curing agent and binder as can be seen from Table 1 were used. For Examples 2 to 16, epoxy resin, curing agent and binder as can be seen from Table 1 were used, and the process for Manufacturing Example 5 as described for Example 1 was followed with the quantities of epoxy resin, curing agent and binder as shown in Table 1. To provide coating properties, the solids content of the epoxy thermoset adhesive mixture was adjusted to 10% to 25% for all examples. As a solvent for dilution, methyl ethyl ketone or ethyl acetate was used, with small amounts of toluene added (5 wt.-%, based on total weight of solvent). All resin contents including binder as shown in Table 1 are based on solids content. Manufacturing Example 6 - Coating of epoxy thermoset adhesive layer on second surface of PI core film, and combining with laser-releasable elastomeric layer The mixture of Manufacturing Example 5 is coated on the polyimide side of the prepared polyimide / silicone adhesive tape of Manufacturing Example 4. After coating, the sample is dried and cured for 2 minutes at 145 °C. Target thickness after drying is 20 µm. After coating of the epoxy thermoset adhesive layer, the laser-releasable elastomeric layer as prepared in Manufacturing Example 2 is combined on the epoxy thermoset adhesive layer through a lamination process using a heating roll at 80 °C. Manufacturing Example 7 - Aging All film layers, including the epoxy thermoset adhesive layer, can be chemically stabilized by aging for 17 hours at 45 °C after coating. If the aging is not performed, there is no significant difference in the adhesion of the epoxy thermoset adhesive layer to the polyimide core film layer, but when it is introduced into a process accompanied by some rapid temperature rise, cracks may occur due to shrinkage by rapid curing. In the case of silicone pressure sensitive adhesive, if aging is not performed, there may be issues such as residue in high temperature processes. Table 1: Unless otherwise noted or readily apparent from the context, all parts, percentages, ratios, etc. in the Examples are by weight. EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 EX10 EX11 EX12 EX13 EX14 EX15 EX16 YDCN- 500-4P30 30 30 30 36 25 30 30 30 30 30 0 0 0 15 0Epoxy resin YDCN- [wt.-500-8P0 0 0 0 0 0 0 0 0 0 0 30 0 0 0 0%] YD-128 0 0 0 0 0 0 0 0 0 0 0 0 30 0 15 0 YD-170 0 0 0 0 0 0 0 0 0 0 0 0 0 30 0 0 KPH- F200120 20 20 20 24 15 20 20 0 0 0 20 20 20 20 0Curing agent KPH-0 0 0 0 0 0 0.-F300 20 20 20 0 0 0 0 0[wt60%] 2PHZ- PW 0 0 0 0 0 0 0.1 0 0 0.1 0 0.1 0.1 0.1 0.1 0 (catalyst) 2E4MI (catalyst)0 0 0 0 0 0 0 0.1 0 0 0.1 0 0 0 0 0KNB- 40H50 0 0 0 40 60 50 50 50 50 50 50 50 50 50 0Binder [wt.- KNB- %]40M0 50 0 0 0 0 0 0 0 0 0 0 0 0 0 0SG-P3 0 0 50 0 0 0 0 0 0 0 0 0 0 0 0 0 SG-708- 60 0 0 50 0 0 0 0 0 0 0 0 0 0 0 100Epoxyratio1:1 1:1 1:1 1:1 6:4 4:6 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 1:1 0

[0002] Table 2: ◎: Excellent / ⃝: Good / Δ: Small defects are observed / X: Defects are observed as a whole 5 EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 EX10 EX11 EX12 EX13 EX14 EX15 EX156 Coatingperformance⃝ Δ ◎ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ⃝ ◎Adhesion to L◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎beforeTHCcuring [gf / 25 mm] to PI 230 60 150 450 180 480 300 450 250 400 500 235 1,280 1,050 1,000 300 to AdhesionLTHC◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎after curing [gf / 25 mm] to PI 1,750 1,650 2,030 1,800 2,000 1,500 2,220 2,000 1,850 2,230 2,000 1,950 4,200 3,150 3,120 350 230 °C oven ⃝ ⃝ ⃝ ⃝ ⃝ Δ ◎ ◎ ⃝ ◎ ◎ ◎ ◎ ◎ ◎ X Thermal test stability 180 °C hotplate Δ Δ ⃝ Δ Δ X ⃝ ⃝ Δ ◎ ⃝ ◎ ⃝ ⃝ ◎ X test

[0003] Comparative Examples 1 and 2 (CEX1 and CEX2) For Comparative Example 1, a temporary bonding film was prepared by applying silicone pressure sensitive adhesive as an inter-adhesive, i.e., instead of the epoxy thermoset adhesive. For Comparative Example 2, a temporary bonding film was prepared by coating a laser-releasable elastomeric layer directly on the back of the polyimide core film without inter-adhesive, i.e., without an epoxy thermoset adhesive layer. For Comparative Examples 1 and 2, the process and formulation of the silicone pressure sensitive adhesive coated on the polyimide core film are the same as in the examples above. In addition, formation of the laser-releasable elastomeric layer is the same. However, in the case of CEX1, addition curing type silicone pressure sensitive adhesive is coated on the back side (polyimide side) of the pre-manufactured silicone / polyimide film with a thickness of 30 µm, and then the laser-releasable elastomeric layer is laminated, i.e., the addition curing type silicone pressure sensitive adhesive is used as an inter-adhesive between the polyimide core film layer and the laser-releasable elastomeric layer, instead of using the epoxy thermoset adhesive layer as an inter-adhesive. In the case of Comparative Example 2, the laser-releasable elastomeric layer mixture is directly coated on the back side (polyimide side) of the pre-made silicone / polyimide film. The thickness of the laser-releasable elastomeric layer is 10 µm after drying, and the drying temperature is 90 °C. Test results (coating performance, adhesion, thermal stability) for Examples 1 to 16 and Comparative Examples 1 and 2 Coating performance of the epoxy thermoset adhesive on the polyimide core film layer, and adhesion before and after curing of the epoxy thermoset adhesive layer to the polyimide core film layer and to the laser-releasable elastomeric layer were investigated for all examples and comparative examples, with the test methods described above. Thermal stability was investigated for all examples, with the test methods described above. Test results for the examples are shown in Table 2. The coating properties of all examples and of Comparative Example 1, including the coating properties of the epoxy thermoset adhesive, were good or excellent (see Table 2; results for CEX1 not shown in Table 2). Comparative Example 2, without inter-adhesive between the polyimide core film layer and the laser-releasable elastomeric layer, showed the most incomplete coating properties (results for CEX2 not shown in Table 2). The bonding performance of the epoxy thermoset adhesive layer to the polyimide core film layer was evaluated before and after curing of the epoxy thermoset adhesive layer. After curing, all examples showed sufficient bonding strength with the exception of Example 16. In particular, when a liquid epoxy was used, the epoxy thermoset adhesive layer exhibited high adhesion to the polyimide core film layer (Examples 13, 14 and 15). When comparing the results of the examples without added curing catalyst before curing (Examples 1 to 6), Example 4 (with a binder resin having a high functional group (-- COOH, --OH) content of 20 mg KOH / g) and Example 6 (with high binder content) showed a high bonding strength. When comparing Examples 1, 7 and 8, the catalyst-free sample (Example 1) shows lower adhesion both before and after curing compared to the samples with added curing catalyst (Examples 7 and 8). The bonding performance of the epoxy thermoset adhesive layer to the laser-releasable elastomeric layer was excellent for all examples, before curing as well as after curing. Without wishing to be bound by theory, this can be explained because the binder of the laser-releasable elastomeric layer and the binder of the epoxy thermoset adhesive layer is based on a polar acrylic-based elastomer. As acrylic binders of the same nature are used, the adhesion is very high when attached to each other. As the peeling force between the epoxy thermoset adhesive layer and the laser-releasable elastomeric layer is very high, the two layers could not be separated and the peel-off value could not be measured. The thermal stability was evaluated with a 230 °C oven test and with a 180 °C hotplate test. These tests were carried out as described above in the test methods section. Excellent results with respect to thermal stability were obtained for Examples 10, 12 and 15 (see Table 2) which had an onset point of curing in the range of 150 - 170 °C. The results for thermal stability for Examples 10, 12 and 15 were better than for examples with an onset point of curing in the range of 80 - 100 °C (Examples 8 and 11). For comparison, the onset point of curing of the examples without added catalyst (Examples 1 to 6) was 200 °C or higher. On the other hand, the results of the thermal stability tests for the sample with no epoxy resin included (Example 16) did not meet expectations (see Table 2; defects are observed as a whole in the 230 °C oven test and the 180 °C hotplate test). Examples 16 is a reference example, Examples 1 to 15 are examples according to the present disclosure. And, the results of the thermal stability tests for Examples 1 to 6, without added curing catalyst and with low curing degree, were worse than the results of the thermal stability tests for examples with added curing catalyst (see Tables 1 and 2). Comparative evaluation of thermal stability for Example 10 (EX10) and Comparative Examples 1 and 2 (CEX1 and CEX2) Thermal stability of Example 10 and Comparative Examples 1 and 2 was evaluated by two methods: a 180 °C hotplate test and a 230 °C oven test. The 180 °C hotplate test is an evaluation method that simulates the metal deposition process of the fan-out process during the redistribution layer (RDL) build-up. The RDL process is a semiconductor packaging process. In other words, the 180 °C hotplate test is an evaluation method to simulate the sputtering process during the semiconductor process. The 230 °C oven test is an evaluation method that simulates the curing process of the passivation layer during the redistribution layer (RDL) build-up, i.e., the oven test is an evaluation method to simulate the passivation curing process during the semiconductor process. The oven test with heat as a whole and the hot plate test with heat only on one side can be seen as different methods for testing thermal stability and thermal shock performance. Both tests need to be passed by the temporary bonding film as disclosed herein. For the 180 °C hotplate test (glass to glass bonding), samples were prepared by bonding two glass carries to a temporary bonding film sample prepared as described above for Example 10 and Comparative Examples 1 and 2. The 180 °C hotplate test was performed as described above in the test methods section (thermal stability testing). For Comparative Example 1, with a silicone pressure-sensitive adhesive being used as an inter-adhesive instead of the epoxy thermoset adhesive, it could be observed that wrinkles are formed between the layers of the temporary bonding film due to melting of the inter- adhesive (i.e., “defects are observed as a whole”). For Example 10, with an epoxy thermoset adhesive being used as an inter-adhesive between the polyimide core film layer and the laser-releasable elastomeric layer, no defects could be observed (i.e., “excellent” for the 180 °C hotplate test). Also for Comparative Example 2, with the laser-releasable elastomeric layer being combined to the polyimide core film layer without inter-adhesive, no defects could be observed (i.e., “excellent” for the 180 °C hotplate test). For the 230 °C oven test (glass to wafer bonding), samples were prepared by bonding a glass carrier and an EMC (epoxy molding compound) molded wafer to a temporary bonding film sample prepared as described above for Example 10 and Comparative Examples 1 and 2. The 230 °C oven test was performed as described above in the test methods section (thermal stability testing). For Example 10 and Comparative Example 1, i.e., for the samples prepared with inter- adhesive, the prepared samples were able to withstand the warpage of the EMC molded wafer even under high temperature (230 °C), corresponding to an evaluation of “excellent” for the 230 °C oven test. For Comparative Example 2, with the laser-releasable elastomeric layer being coated directly on the polyimide core film layer without inter- adhesive, it was observed that delamination occurred, and the prepared sample was not able to withstand bending of the EMC molded wafer at high temperature, corresponding to an evaluation of “defects are observed as a whole” for the 230 °C oven test. The Examples and Comparative Examples and the thermal stability tests show that the temporary bonding film as disclosed herein is able to withstand both high-temperature hotplate and oven processes, and still not loses the properties of flexible films such as adhesive and mechanical properties. For multi-layered temporary bonding films for high-temperature semiconductor packaging process, a high heat-resistant silicone adhesive layer, a polyimide core film layer, and a laser-releasable elastomeric layer are required. However, bonding between the polyimide core film layer and the laser-releasable elastomeric layer is a key element that determines the heat resistance of the entire temporary bonding film. For the temporary bonding film disclosed herein, an effective bonding method has been found for bonding the dissimilar film materials of the polyimide core film layer and the laser-releasable elastomeric layer.

Claims

What is claimed is:

1. A temporary bonding film, comprising: a polyimide core film layer, having a first surface and a second surface; a pressure sensitive adhesive layer disposed on the first surface of the polyimide core film layer; an epoxy thermoset adhesive layer disposed on the second surface of the polyimide core film layer; and a laser-releasable elastomeric layer disposed on the epoxy thermoset adhesive layer.

2. The temporary bonding film of claim 1, wherein the epoxy thermoset adhesive layer comprises an epoxy thermoset adhesive comprising an epoxy resin, a curing agent, and a binder.

3. The temporary bonding film of claim 2, wherein the epoxy thermoset adhesive comprises at most 55 percent by weight of the binder, based on the total solids content of the epoxy thermoset adhesive.

4. The temporary bonding film of claim 2, wherein the weight ratio of the sum of the amount of the epoxy resin and the curing agent to the amount of the binder is from 1 : 9 to 9 :

1.

5. The temporary bonding film of claim 2, wherein the epoxy resin comprises a polyfunctional epoxy resin.

6. The temporary bonding film of claim 2, wherein the softening point of the epoxy resin is at most 70 °C.

7. The temporary bonding film of claim 2, wherein the curing agent is selected from the group consisting of amine-based curing agents, phenol-based curing agents, anhydride curing agents, peroxide curing agents, imidazole curing agents, and combinations thereof.

8. The temporary bonding film of claim 1, wherein the onset point of curing of the epoxy thermoset adhesive is at least 120 °C and at most 180 °C.

9. The temporary bonding film of claim 2, wherein the binder of the epoxy thermoset adhesive comprises at least one of a rubber-based elastomer and an acrylic- based elastomer.

10. The temporary bonding film of claim 2, wherein the binder of the epoxy thermoset adhesive comprises an acrylic-based elastomer, and wherein the acrylic-based elastomer comprises an acrylic polymer made by polymerization of at least one acrylic monomer selected from the group consisting of ethyl acrylate, butyl acrylate, glycidyl methacrylate, acrylic acid, acrylonitrile, and combinations thereof.

11. The temporary bonding film of claim 10, wherein the acrylic polymer comprises polar functional groups, and wherein the polar functional groups are selected from the group consisting of nitrile groups, carboxyl groups, hydroxyl groups, glycidyl groups, amine groups, and combinations thereof.

12. The temporary bonding film of claim 11, wherein the polar functional groups are carboxyl groups and / or hydroxyl groups, and wherein the acrylic polymer comprises at least 1 mg KOH / g polymer of polar functional groups.

13. The temporary bonding film of claim 12, and wherein the acrylic polymer comprises between 1 and 25 mg KOH / g polymer of polar functional groups.

14. The temporary bonding film of claim 2, wherein the binder has a glass transition temperature at least -20 °C and at most 60 °C.

15. The temporary bonding film of claim 1, wherein the thickness of the epoxy thermoset adhesive layer is from 10 to 45 µm.

16. The temporary bonding film of claim 1, wherein the pressure sensitive adhesive comprises a silicone.

17. The temporary bonding film of claim 1, wherein the laser-releasable elastomeric layer comprises an acrylic-based elastomer.

18. The temporary bonding film of claim 1, wherein the laser-releasable elastomeric layer comprises carbon black.

19. The temporary bonding film of claim 1, wherein the laser-releasable elastomeric layer comprises an inorganic filler.

20. The temporary bonding film of claim 19, wherein the inorganic filler comprises at least one of titania or silica.

21. The temporary bonding film of claim 19, wherein the inorganic filler comprises at least one of alumina-coated titania or silica.

22. The temporary bonding film of claim 1, further comprising a first liner disposed on the pressure sensitive adhesive layer opposite the polyimide core film layer.

23. The temporary bonding film of claim 1, further comprising a second liner disposed on the laser-releasable elastomeric layer opposite the epoxy thermoset adhesive layer.