Adhesive sheet for semiconductor device manufacturing and method for manufacturing semiconductor device using same

Abstract

The present invention provides an adhesive sheet that sufficiently and stably adheres to a back surface of a lead frame and a back surface of a sealing resin, and is not separated therefrom before a separation step even when subjected to a thermal history associated with QFN assembly, and is free from leakage of the sealing resin, while being able to be easily separated in the separation step without the occurrence of adhesive residue, namely without leaving some adhesive behind, or without the occurrence of breakage, and a method for producing a semiconductor device, said method using this adhesive sheet. Specifically, provided is an adhesive sheet for semiconductor device production, the adhesive sheet being provided with a base material and a heat curing adhesive layer and being separably bonded to a lead frame or a circuit board of a semiconductor device, wherein the adhesive layer contains a carboxy group-containing acrylonitrile butadiene copolymer (a), an epoxy resin (b), and a compound (c) containing two or more maleimide groups, and has a storage elastic modulus of 1-1.7 MPa at 80°C.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet that is suitable for use as a masking tape when assembling a semiconductor device using the QFN (Quad Flat Non-lead) method, and a method for manufacturing a semiconductor device using the same. This application claims priority based on Japanese Patent Application No. 2021-022422, filed on February 16, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, there has been a growing need for higher density mounting technology in semiconductor devices (semiconductor packages) in response to demands for smaller, thinner, and more multifunctional IT devices, including mobile phones. As a CSP (Chip Size Package) technology that meets this demand, the QFN method has attracted attention (see Patent Documents 1 and 2), and has been widely adopted, particularly for low-pin count types of 100 pins or less.

[0003] Here, the following method is generally known as a typical method for assembling a QFN package using the QFN method. First, in the bonding process, an adhesive sheet is attached to one side of a lead frame. Next, in the die attach process, semiconductor elements such as IC chips are mounted on multiple semiconductor element mounting areas (die pads) formed on the lead frame. Next, in the wire bonding process, multiple leads arranged along the periphery of each semiconductor element mounting area on the lead frame are electrically connected to the semiconductor elements using bonding wires. Next, in the encapsulation process, the semiconductor elements mounted on the lead frame are encapsulated with encapsulating resin. Then, in the peeling process, the adhesive sheet is peeled from the lead frame to form a QFN unit in which multiple QFN packages are arranged. Finally, in the dicing process, the QFN unit is diced along the periphery of each QFN package to produce multiple QFN packages.

[0004] Adhesive sheets used for such applications are required to adhere sufficiently and stably to the back surface of the lead frame and the back surface of the sealing resin without peeling off until the peeling process, and to be easily peeled off during the peeling process without leaving any adhesive residue on the back surface of the lead frame or the back surface of the sealing resin, or causing problems such as tearing of the adhesive sheet. In particular, in recent years, lead frames made of copper alloys have come to be used to reduce the cost of semiconductor devices. Lead frames made of such copper alloys have the catalytic effect of oxidizing and degrading polymer materials, as copper is a transition metal. The thermal history associated with assembling the QFN package after the taping process makes the adhesive susceptible to oxidation and degradation, leading to heavy peeling and adhesive residue when the sheet is peeled off.

[0005] However, the adhesive sheets that have been used in the past have not been sufficiently satisfactory for practical use with lead frames made of copper alloys. For example, some conventional adhesive sheets have a structure in which an adhesive layer containing an acrylonitrile-butadiene copolymer and a bismaleimide resin is laminated onto a substrate made of a heat-resistant film (see Patent Document 3). However, when this is used, the acrylonitrile-butadiene copolymer is prone to degradation due to the heat applied during the die attach cure treatment, wire bonding process, and resin sealing process after the taping process, which causes problems such as difficulty in peeling during the peeling process, tearing of the adhesive sheet, and residue of adhesive. Furthermore, conventional adhesive sheets have the problem that if there are protrusions such as polishing scratches on the lead frame, they cannot conform to the shape of the protrusions, causing air bubbles to form between the adhesive sheet and the lead frame, causing the adhesive sheet to peel off from the lead frame. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-165961 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-142401 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-095014 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above circumstances, and its object is to provide an adhesive sheet that adheres sufficiently and stably to the back surface of the lead frame and the back surface of the sealing resin without peeling off from them even when subjected to the thermal history associated with QFN assembly until the peeling process, and that does not cause leakage of the sealing resin, and yet can be easily peeled off in the peeling process without leaving any adhesive residue or breaking, and a method for manufacturing a semiconductor device using the same. [Means for solving the problem]

[0008] The present invention has the following aspects. [1] An adhesive sheet for use in the production of semiconductor devices, comprising a substrate and a thermosetting adhesive layer provided on one surface of the substrate, and adapted to be peelably attached to the lead frame or wiring board of a semiconductor device, wherein the adhesive layer contains a carboxyl group-containing acrylonitrile-butadiene copolymer (a), an epoxy resin (b), and a compound (c) containing two or more maleimide groups, and has a storage modulus at 80°C of 1 MPa to 1.7 MPa. [2] The adhesive sheet for production of semiconductor device according to [1], wherein the component (a) is a carboxyl group-containing acrylonitrile-butadiene copolymer having an acrylonitrile content of 5 to 50% by mass and a carboxyl group equivalent weight calculated from the number average molecular weight of 100 to 20,000. [3] The adhesive sheet for production of semiconductor device according to [1], characterized in that the total of the components (b) and (c) is 20 to 300 parts by mass per 100 parts by mass of the component (a). [4] The adhesive sheet for production of semiconductor device according to [1], wherein the ratio of the amount of glycidyl groups based on the component (b) to the amount of carboxyl groups based on the component (a) is 0.14 to 0.43. [5] A method for manufacturing a semiconductor device using the adhesive sheet for manufacturing a semiconductor device according to [1], a bonding step of bonding an adhesive sheet for manufacturing a semiconductor device to a lead frame or a wiring board; a die-attach step of mounting a semiconductor element on the lead frame or wiring substrate; a wire bonding step of electrically connecting the semiconductor element to an external connection terminal; a sealing step of sealing the semiconductor element with a sealing resin; A method for manufacturing a semiconductor device, comprising, after the sealing step, a peeling step of peeling the adhesive sheet for manufacturing a semiconductor device from the lead frame or the wiring substrate. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an adhesive sheet that adheres sufficiently and stably to the back surface of the lead frame and the back surface of the sealing resin without peeling off from them even when subjected to the thermal history associated with QFN assembly, and that does not cause leakage of the sealing resin, and that can be easily peeled off in the peeling process without leaving any adhesive residue or breaking, and an adhesive sheet that adheres sufficiently even to lead frames that have protrusions such as polishing scratches until the peeling process, and a method for manufacturing a semiconductor device using the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a plan view showing an example of a lead frame used in a method for manufacturing a semiconductor device according to the present invention; [Figure 2] 1A to 1C are process diagrams illustrating a method for manufacturing a semiconductor device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. [Adhesive sheets for semiconductor device manufacturing] The adhesive sheet for semiconductor device production of the present invention (hereinafter referred to as adhesive sheet) comprises a substrate and a thermosetting adhesive layer provided on one side of the substrate, and is an adhesive sheet that is releasably attached to the lead frame or wiring board of a semiconductor device. The adhesive layer contains a carboxyl group-containing acrylonitrile-butadiene copolymer (a), an epoxy resin (b), and a compound (c) containing two or more maleimide groups, and has a storage modulus of 1 MPa to 1.7 MPa at 80°C. The adhesive sheet is used as a masking tape when assembling semiconductor devices using the QFN method.

[0012] The carboxyl group-containing acrylonitrile-butadiene copolymer (a) plays a role in maintaining an appropriate melt viscosity of the adhesive layer during the initial heating period and imparts good flexibility and adhesiveness to the cured adhesive layer. By incorporating this copolymer, it is possible to form an adhesive layer that adheres well to substrates such as heat-resistant films and is free of cracks. Any known carboxyl group-containing acrylonitrile-butadiene copolymer (a) can be used without limitation. However, copolymers with an acrylonitrile content of 5 to 50% by mass are preferred, and those with an acrylonitrile content of 10 to 40% by mass are more preferred. If the acrylonitrile content is below the above range, the solubility in solvents and compatibility with other components decrease, which tends to reduce the uniformity of the resulting adhesive layer. On the other hand, if the acrylonitrile content exceeds the above range, the resulting adhesive layer will have excessive adhesion to lead frames and encapsulating resins. When used in an adhesive sheet, this can lead to difficulty in peeling during the peeling process or the adhesive sheet may break.

[0013] The carboxyl group equivalent calculated from the number average molecular weight of the carboxyl group-containing acrylonitrile-butadiene copolymer is preferably in the range of 100 to 20,000, more preferably 200 to 10,000. If the carboxyl group equivalent is below this range, the reactivity with other components will be too high, and the storage stability of the resulting adhesive layer will tend to decrease. On the other hand, if the carboxyl group equivalent exceeds this range, the reactivity with other components will be insufficient, and the resulting adhesive layer will likely exhibit a low B-stage. As a result, when this is used in an adhesive sheet, the viscosity of the adhesive layer will decrease when the adhesive sheet is heated in the initial stage of heating, i.e., during the adhesive sheet attachment process or die attach cure treatment, and the like, the adhesive layer will tend to foam or flow, and the thermal stability will tend to decrease. The carboxyl group equivalent calculated from the number average molecular weight is the number average molecular weight (Mn) divided by the number of carboxyl groups (number of functional groups) per molecule, and is shown by the following formula. Carboxyl group equivalent = Mn / number of functional groups

[0014] The epoxy resin (b) is a compound having two or more epoxy groups in the molecule, and examples thereof include diglycidyl ethers such as bisphenol A, bisphenol F, bisphenol S, resorcinol, dihydroquinaphthalene, and dicyclopentadiene diphenol; alicyclic epoxy resins such as epoxidized phenol novolac, epoxidized cresol novolac, epoxidized cresol novolac, epoxidized trisphenylol methane, and epoxidized tetraphenylol ethane; biphenyl-type epoxy resins; and novolac-type epoxy resins.

[0015] The epoxy resin (b) and the compound (c) containing two or more maleimide groups are responsible for the thermosetting properties of the adhesive layer, and by using them in combination, it is possible to form an adhesive layer that is excellent in thermal stability, can be easily peeled off during the peeling process, and does not leave any adhesive residue or breakage. In particular, the epoxy resin (b) imparts toughness to the adhesive layer, and by including this, it is possible to prevent adhesive residue caused by cracking of the adhesive layer during the peeling process.

[0016] The compound (c) containing two or more maleimide groups imparts thermal stability to the adhesive layer and also acts to adjust the adhesiveness of the adhesive layer. By containing this compound, the adhesiveness can be appropriately controlled, and an adhesive layer can be formed that can be easily peeled off in the peeling step. Specific examples of the compound (c) containing two or more maleimide groups include compounds that constitute bismaleimide resins, such as those represented by the following formulas (1-1) to (1-3). Among these, the compounds represented by the following formulas (1-1) or (1-3) are particularly useful in terms of solubility in solvents.

[0017] [ka]

[0018] Each of the components (a) to (c) may be composed of one type of compound or a mixture of two or more types of compounds.

[0019] The ratio of each of the components is preferably 20 to 300 parts by mass, more preferably 20 to 200 parts by mass, of the total of components (b) and (c) per 100 parts by mass of component (a). If the total of components (b) and (c) is less than the above range, the reactivity of the adhesive layer decreases, making it difficult for the adhesive to become insoluble or infusible even when heated, and the thermal stability decreases, tending to result in stronger adhesive strength. On the other hand, if the total exceeds the above range, the melt viscosity of the adhesive layer at the initial stage of heating is insufficient, and in adhesive sheets using this adhesive layer, the adhesive layer may flow or foam during a die attach cure process after the taping process.

[0020] Furthermore, the mass ratio of component (c) to component (b) ((c) / (b)) is preferably in the range of 0.1 to 10. If the mass ratio is less than this range, the resulting adhesive layer may be prone to undergoing a curing reaction at room temperature, resulting in poor storage stability, or the adhesive strength may be so strong that an adhesive sheet using this may become impossible to peel or break during the peeling step. On the other hand, if the mass ratio exceeds this range, the adhesive strength between the adhesive layer and the substrate made of a heat-resistant film may decrease during the production of the adhesive sheet, the adhesive layer may foam, or the resulting adhesive sheet may be prone to leaving adhesive residue.

[0021] The adhesive layer in the adhesive sheet of the present invention has a storage modulus at 80°C of 1 MPa to 1.7 MPa, and preferably 1.5 MPa to 1.7 MPa. In the adhesive layer of the adhesive sheet of the present invention, a storage modulus of 1 MPa to 1.7 MPa at 80°C can be achieved, for example, by adjusting the contents of components (a), (b), and (c). For example, when component (b) having the same epoxy group equivalent is contained, the storage modulus at 80°C can be increased by increasing the content of epoxy resin (b). The storage modulus of the adhesive layer in the adhesive sheet of the present invention is measured by peeling the adhesive layer from the substrate and measuring the peeled adhesive layer with a dynamic viscoelasticity measuring device at a measurement frequency of 11 Hz and a load of 1.0 gf while increasing the temperature from 25° C. to 150° C. at a rate of 10° C. / min. If the storage modulus of the adhesive layer at 80° C. is 1 MPa to 1.7 MPa, it can be sufficiently adhered even to lead frames having protrusions such as polishing scratches up until the peeling step. The dynamic viscoelasticity measuring device may be a Vibron measuring device (manufactured by Orientec Co., Ltd., RHEOVIBRON DDV-II-EP) or the like.

[0022] Furthermore, the adhesive layer in the adhesive sheet of the present invention preferably has a glycidyl group amount / carboxyl group amount ratio of 0.14 to 0.43, and more preferably 0.21 to 0.43. If the glycidyl group amount / carboxyl group amount ratio is within the above range, the adhesive layer can be sufficiently adhered even to lead frames having protrusions such as polishing scratches, right up to the peeling step. The amount of glycidyl groups can be calculated by dividing the content of component (b) by the epoxy group equivalent, and the amount of carboxyl groups can be calculated by dividing the content of component (a) by the carboxyl group equivalent.

[0023] The adhesive layer in the adhesive sheet of the present invention may contain a reactive siloxane compound. The reactive siloxane compound enhances the compatibility of the components constituting the adhesive layer and improves the releasability of the adhesive layer from the encapsulating resin. By containing this compound, the components are well compatible with each other, and a uniform adhesive layer can be formed without problems such as component separation or precipitation. As a result, the adhesive layer has uniform adhesive strength, and problems such as reduced releasability and adhesive residue caused by partially high adhesive strength can be suppressed. As the reactive siloxane compound, siloxane compounds that have been rendered reactive by reactive groups such as amino-modified, epoxy-modified, carboxyl-modified, and mercapto-modified can be used without limitation. Among these, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, aminopropyl-terminated dimethylsiloxane tetramer or octamer, and bis(3-aminophenoxymethyl)tetramethyldisiloxane are preferred because they react quickly with components (b) and (c). As the reactive siloxane compound, those with reactive groups bonded to both ends of the siloxane structure are preferred from the standpoint of reactivity, but those with reactive groups bonded to one end or silane coupling agents with one end reactive and the other non-reactive can also be used.

[0024] In the adhesive layer of the adhesive sheet of the present invention, the ratio of the number of reactive groups in the reactive siloxane compound to the sum of the number of epoxy groups in component (b) and the number of maleimide groups in component (c) is preferably 0.05 to 1.2, more preferably 0.1 to 0.8. If the ratio is below this range, the reactivity of the adhesive layer as a whole decreases, making it difficult for the curing reaction to proceed during die-attach cure treatment or the like, which can result in excessively strong adhesive strength. On the other hand, if the ratio exceeds this range, the reaction may proceed excessively, which can easily cause problems such as gelation during preparation of the adhesive layer and weaken the adhesive strength.

[0025] In addition to the essential components (a) to (c), the adhesive layer may contain reaction accelerators such as organic peroxides, imidazoles, triphenylphosphine, etc. Addition of these accelerators makes it possible to control the state of the adhesive layer at room temperature to a good B-stage. Furthermore, a filler having an average particle size of 1 μm or less may be added for purposes such as controlling melt viscosity, improving thermal conductivity, and imparting flame retardancy. Examples of fillers include inorganic fillers such as silica, alumina, magnesia, aluminum nitride, boron nitride, titanium oxide, calcium carbonate, and aluminum hydroxide, and organic fillers such as silicone resin and fluororesin. When a filler is used, its content in the adhesive layer is preferably 1 to 40% by mass.

[0026] The adhesive sheet of the present invention comprises a heat-resistant film substrate having the above-described adhesive layer formed on one side thereof. To produce such an adhesive sheet, first prepare an adhesive coating material comprising at least the aforementioned carboxyl group-containing acrylonitrile-butadiene copolymer (a), epoxy resin (b), compound (c) containing two or more maleimide groups, and optionally a reactive siloxane compound and a solvent. This coating material is then applied to one side of a heat-resistant film so that the thickness of the adhesive layer after drying is preferably 1 to 50 μm, more preferably 3 to 20 μm, and then dried. Furthermore, to protect the adhesive layer, it is preferable to further provide a peelable protective film on the formed adhesive layer. In this case, the adhesive sheet may be produced by applying the coating material to the protective film, drying it to form an adhesive layer, and then providing a heat-resistant film on top of that. The protective film is peeled off when the adhesive sheet is used.

[0027] Examples of heat-resistant films include heat-resistant plastic films made of polyimide, polyphenylene sulfide, polyether sulfone, polyether ether ketone, liquid crystal polymer, polyethylene terephthalate, polyethylene naphthalate, etc., and composite heat-resistant films such as epoxy resin-glass cloth, with polyimide films being particularly preferred. The thickness of the polyimide film is preferably 12.5 to 125 μm, more preferably 25 to 50 μm. If the thickness is less than this range, the adhesive sheet tends to lack stiffness and become difficult to handle, while if the thickness exceeds this range, the taping and peeling steps during QFN assembly tend to be difficult to handle.

[0028] The solvent used in the adhesive coating material can be one or more of organic solvents such as hydrocarbons, alcohols, ketones, and ethers (e.g., tetrahydrofuran), water, etc., and the amount used can be adjusted appropriately to achieve an appropriate viscosity for the coating material. The coating material may be in the form of a solution, emulsion, or suspension, and can be selected appropriately depending on the coating device used and environmental conditions, etc.

[0029] Examples of peelable protective films include plastic films such as polyethylene, polypropylene, vinyl chloride, fluorine-based resins, and silicone, as well as polyethylene terephthalate, polyethylene naphthalate, and paper that have been given peelability by coating with silicone or the like.

[0030] [Method of manufacturing a semiconductor device] The method for manufacturing a semiconductor device using the adhesive sheet of the present invention comprises an attachment step of attaching the adhesive sheet to a lead frame or wiring board, a die attach step of mounting a semiconductor element on the lead frame or wiring board, a wire bonding step of establishing electrical continuity between the semiconductor element and an external connection terminal, an encapsulation step of encapsulating the semiconductor element with an encapsulating resin, and a peeling step of peeling the adhesive sheet from the lead frame or wiring board after the encapsulation step.

[0031] An example of a method for manufacturing a semiconductor device using an adhesive sheet of the present invention will now be described with reference to Figures 1 and 2. Figure 1 is a plan view of a lead frame seen from the side on which a semiconductor element is mounted, and Figures 2(a) to 2(f) are process diagrams showing a method for manufacturing a QFN package using the lead frame shown in Figure 1, and are cross-sectional views taken along the line A-A' of the lead frame in Figure 1.

[0032] First, a lead frame 20 having the general configuration shown in Fig. 1 is prepared. The lead frame 20 has a plurality of semiconductor element mounting portions (die pad portions) 21, on which semiconductor elements such as IC chips are mounted, formed in a matrix, and a large number of leads 22 (external connection terminals) formed along the periphery of each semiconductor element mounting portion 21. Examples of materials for the lead frame 20 include conventionally known materials, such as copper plates and copper alloy plates, or copper alloy plates with strike plating, and copper alloy plates with a nickel plating layer, a palladium plating layer, and a gold plating layer formed in this order on the surface thereof.

[0033] As shown in FIG. 2(a), the adhesive sheet 10 is attached to one surface (lower surface) of the lead frame 20 so that the adhesive layer (not shown) abuts against the lead frame 20 (attaching step). Methods for attaching the adhesive sheet 10 to the lead frame 20 include lamination and pressing, but from the viewpoint of productivity, the lamination method is preferred because it allows the taping step to be performed continuously. The temperature of the adhesive sheet 10 in this step is, for example, from room temperature (5 to 35°C) to 150°C, and 60 to 120°C is more preferable. If the adhesive sheet is attached at a temperature higher than 150°C, warping of the lead frame is likely to occur. If the lead frame 20 warps in this process, it may become difficult to position it in the die attach process or wire bonding process, or to transport it to a heating furnace, which may reduce the productivity of the QFN package.

[0034] As shown in FIG. 2(b), a semiconductor element 30 such as an IC chip is placed via a die attach adhesive (not shown) on the side of the semiconductor element mounting portion 21 of the lead frame 20 where the adhesive sheet 10 is not attached. At this time, the lead frame 20 is easily positioned because warping is suppressed. The semiconductor element 30 is then accurately placed in the predetermined position. Thereafter, the die attach adhesive is cured by heating to approximately 100 to 200°C, and the semiconductor element 30 is fixedly mounted on the semiconductor element mounting portion 21 (die attach adhesive curing process; this is the die attach process). At this time, the adhesive layer of the adhesive sheet 10 hardens and is adhered to the lead frame.

[0035] If outgassing components generated from the adhesive sheet 10, die attach adhesive, etc. adhere to the lead frame 20 or semiconductor element 30, poor wire bonding is likely to occur during the wire bonding process, resulting in a decrease in yield. Therefore, after the die attach process and before the wire bonding process, the lead frame 20 and semiconductor element 30 are subjected to plasma treatment (plasma cleaning process). Examples of plasma treatment include a method in which the lead frame 20 (hereinafter sometimes referred to as a work in progress) on which the adhesive sheet 10 is attached and the semiconductor element 30 is mounted is irradiated with plasma in an atmosphere of argon gas or a mixed gas of argon gas and hydrogen gas. The plasma irradiation power in the plasma treatment is, for example, 150 to 600 W. The plasma treatment time is, for example, 0.1 to 15 minutes.

[0036] As shown in Fig. 2(c), the semiconductor element 30 and the leads 22 (external connection terminals) of the lead frame 20 are electrically connected by bonding wires 31 such as gold wires, copper wires, or palladium-coated copper wires (wire bonding process). This process is carried out while the work-in-progress is heated on a heater block to about 150 to 250°C. The heating time in this process is, for example, 5 to 60 minutes. When the work-in-progress is heated during the wire bonding process, if a fluorine additive is contained in the adhesive layer, the fluorine additive will migrate to the surface of the adhesive layer, making it easier to peel the adhesive sheet 10 from the lead frame 20 and the sealing resin 40 in the peeling process described below.

[0037] As shown in Fig. 2(d), the work-in-process shown in Fig. 2(c) is placed in a mold, and a sealing resin (mold material) is injected and filled into the mold. After a desired amount has been filled into the mold, the interior of the mold is maintained at a desired pressure, thereby sealing the semiconductor element 30 with the sealing resin 40 (sealing step). As the sealing resin, a conventionally known material can be used, such as a mixture of epoxy resin and inorganic filler. As shown in FIG. 2(e), the adhesive sheet 10 is peeled off from the sealing resin 40 and the lead frame 20 to obtain a QFN unit 60 in which a plurality of QFN packages 50 are arranged (peeling step).

[0038] As shown in FIG. 2(f), the QFN unit 60 is diced along the periphery of each QFN package 50 to obtain a plurality of QFN packages 50 (dicing step).

[0039] In the above-described embodiment, a method for manufacturing a QFN package using a lead frame has been described as an example, but the present invention is not limited to this and can also be applied to methods for manufacturing semiconductor devices other than QFN packages using a lead frame, and methods for manufacturing semiconductor devices using wiring substrates.

[0040] The adhesive layer in the adhesive sheet of the present invention can have a low glass transition temperature (-30°C to 50°C) by crosslinking the carboxyl groups of the carboxyl group-containing acrylonitrile-butadiene copolymer (a) with the glycidyl groups of the epoxy resin (b) to achieve a B-stage state (semi-cured state). Adhesive sheets having adhesive layers with low glass transition temperatures can be continuously taped using a roll laminator or the like under relatively low heating conditions, specifically at room temperature (5°C to 35°C) to 150°C, resulting in excellent productivity.

[0041] Furthermore, the adhesive layer of the adhesive sheet of the present invention, which has a low glass transition temperature (-30°C to 50°C), exhibits high elastic modulus characteristics when heated. In recent years, with the aim of reducing costs in the wire bonding process, products bonded with low-cost copper wire or palladium-coated copper wire instead of conventional gold wire have begun to become popular. Because copper wire or palladium-coated copper wire is a metal with higher elasticity than gold, it requires processing with a higher load than conventional gold wire to create a stable shape. When such a large load is applied to the lead frame, if the adhesive layer in the adhesive sheet attached to the lower part of the lead frame has a low elastic modulus, the adhesive layer will deform and the resin will be sealed in the deformed state. This will cause leakage of the sealing resin from the deformed adhesive layer. Furthermore, when peeling the adhesive sheet from the lead frame, the adhesive layer will break from the deformed adhesive layer, causing the adhesive to remain on the surface of the lead frame. In addition, if the adhesive has a low elastic modulus during wire bonding, the adhesive will deform, making it difficult to transmit the wire load and more likely to cause wire bonding defects. Because the adhesive layer in the adhesive sheet of the present invention has the above-mentioned high elastic modulus, even when wire bonding is performed using copper wire or palladium-coated copper wire, problems such as wire bonding defects, leakage of the sealing resin, and residual adhesive layer are less likely to occur. [Example]

[0042] The present invention will be specifically described below with reference to examples. [Examples 1 to 6 and Comparative Examples 1 to 3] (Adhesive paint composition) Components (a) to (c) and other components were mixed in the mass ratios shown in Table 1 with tetrahydrofuran (THF) as a solvent to prepare an adhesive coating material. Next, this adhesive coating was applied to one side of a 25 μm thick polyimide film (manufactured by Toray DuPont Co., Ltd., product name Kapton 100EN) so that the adhesive layer would be 5 μm thick after drying, and then dried in a hot air circulating oven to obtain an adhesive sheet. The details of each component used are as follows:

[0043] Carboxyl group-containing acrylonitrile-butadiene copolymer: Carboxyl group equivalent calculated from number average molecular weight: 1500, acrylonitrile content: 27% by mass Epoxy resin A: molecular weight 630, epoxy group equivalent weight 210g / eq Epoxy resin B: molecular weight 950, epoxy group equivalent weight 475g / eq Epoxy resin C: molecular weight 1850, epoxy group equivalent weight 925g / eq Bisphenol A diphenyl ether bismaleimide: molecular weight 570, functional group equivalent weight 285g / eq 1,3-bis(3-aminopropyl)tetramethyldisiloxane: molecular weight 248, functional group equivalent weight 62g / eq

[0044] [Table 1]

[0045] The adhesive sheets of the examples obtained as described above were subjected to the following measurements and evaluations, and the results are shown in Table 2. (1) Peel strength against Cu plate Substrate: Copper plate (Furukawa 125 μm 64 type) Adhesive sheet size: Width 10mm x Length 50mm Processing: Using a roll laminator, the adhesive sheet obtained in each example was attached to the adherend to prepare a test specimen. The lamination conditions were a temperature of 80°C, a pressure of 4 N / cm, and a pressing speed of 1 m / min. Measurement: Using a universal tensile tester, the 90° peel strength of the heated specimen was measured at room temperature. The copper plate was fixed and the adhesive sheet was pulled vertically. The pulling speed was 50 mm / min. Evaluation: A peel strength of 15 gf / cm or more is an adhesive strength that does not pose a problem in practice. 15 gf / cm or more was rated as ◯, and less than 15 gf / cm was rated as x.

[0046] (2) Peel strength of the test specimen after the resin sealing process, and presence or absence of adhesive residue after peeling off the tape Processing and measuring method: (i) Preparation of specimens and heat treatment The adhesive sheet having an adhesive layer on a polyimide film obtained in each example was cut to a width of 50 mm and a length of 60 mm. After that, assuming the thermal history involved in assembling an actual QFN, the following steps (a) to (d) were first carried out in sequence. (a) The adhesive sheet obtained in each example was cut to a width of 50 mm and a length of 60 mm, and this was attached to a copper alloy test lead frame (surface strike plating, 8x8 matrix arrangement, package size 5mm x 5mm, 32 pins) with external dimensions of 50mm x 100mm using a roll laminator. The lamination conditions were a temperature of 80°C, pressure of 4N / cm, and compression speed of 0.5m / min. (b) A copper alloy test lead frame with an adhesive sheet attached was heated in a ventilated oven at 175°C for 60 minutes, which is a process intended for die attach cure processing. (c) Plasma irradiation treatment: Treatment was carried out using a 1000P manufactured by Yield Engineering Co., Ltd., using Ar as the gas species, at 450 W for 60 seconds. (d) Heating at 200°C for 30 minutes: This is a treatment simulating a wire bonding process, and heating was performed using a hot plate. Next, a molding resin was laminated on the exposed copper surface of the adherend that had undergone the heat treatments (a) to (d), opposite the surface to which the adhesive sheet had been attached, at 175°C for 3 minutes using a mold press (resin sealing process). Epoxy molding resin (EME-G631BQ) manufactured by Sumitomo Bakelite Co., Ltd. was used as the molding resin.

[0047] (ii) Peel strength measurement and presence or absence of adhesive residue after peeling the tape The 90° peel strength of the test specimens after the resin encapsulation process described above was measured at room temperature using a universal tensile tester. The test specimen was fixed and the corner of the adhesive sheet was pulled vertically. The tensile speed was 300 mm / min. The presence or absence of adhesive residue after tape peeling was confirmed using an optical microscope (Keyence VHX-500 Digital Microscope) at 100x magnification. Evaluation: ◯: Peel strength is less than 1000 gf / 50 mm, the peeled adhesive sheet is not broken, and no adhesive remains on the surface of the lead frame material or the surface of the sealing resin. △: Peel strength is 1000 gf / 50 mm or more, the peeled adhesive sheet is not broken, and no adhesive remains on the surface of the lead frame material or the surface of the sealing resin. ×: At least one of the following occurred: breakage of the adhesive sheet was observed, or adhesive residue was observed on the surface of the lead frame material and on the surface of the sealing resin.

[0048] (3) Thermal characteristics after the die attach process Processing: In the adhesive sheets obtained in each example, the 25 μm thick polyimide film was replaced with a 38 μm thick polyethylene terephthalate film (PET film) that had been subjected to release treatment, and this was heated at 175°C for 1 hour in a ventilated oven to simulate die attach cure processing. Measurement: After heating, the adhesive layer of the adhesive sheet was removed from the PET film, and the storage modulus was measured using a DMA (Dynamic Mechanical Analyzer). Measurements were carried out using a Vibron measuring instrument (RHEOVIBRON DDV-II-EP, manufactured by Orientec Co., Ltd.) as the DMA at a frequency of 11 Hz, a temperature rise rate of 10° C. / min, and a load of 1.0 gf. Evaluation: A storage modulus of 5 MPa or more at 200° C., the temperature assumed to be applied during the wire bonding process, was evaluated as ◯.

[0049] (4) Tracking ability Processing: The adhesive sheet obtained in each example was cut to a width of 50 mm and a length of 60 mm, and this was attached using a roll laminator to a copper alloy test lead frame (surface strike plating, 8 x 8 matrix arrangement, package size 5 mm x 5 mm, 32 pins) with external dimensions of 50 mm x 100 mm. The lamination conditions were a temperature of 80°C, pressure of 4 N / cm, and a compression speed of 1 m / min. Evaluation: The adhesive tape adhered to the above-mentioned test lead frame was visually inspected for conformity between the lead frame and the adhesive layer. ○: No air bubbles are generated between the lead frame and the adhesive layer ×: Air bubbles are generated between the lead frame and the adhesive layer

[0050] [Table 2]

[0051] As is clear from Table 2 above, the adhesive sheets of Examples 1 to 6 were found to be satisfactory for practical use in all evaluations, including conformability, peel strength against Cu plate, thermal properties after the die attach process, peel strength against test specimens after the resin sealing process, and the presence or absence of adhesive residue after tape peeling. In contrast, the adhesive sheet of Comparative Example 1 had problems in the evaluation of peel strength, the adhesive sheet of Comparative Example 2 had problems in the evaluation of conformability, and the adhesive sheet of Comparative Example 3 had problems in the evaluation of thermal properties after the die attach process. [Explanation of symbols]

[0052] 10. Adhesive sheet for semiconductor device manufacturing 20 Lead Frame 30 Semiconductor elements 31 Bonding wire 40 Sealing resin 50 QFN package

Claims

1. An adhesive sheet for use in the production of semiconductor devices, comprising a substrate and a thermosetting adhesive layer provided on one surface of the substrate, the adhesive sheet being releasably attached to a lead frame or wiring board of a semiconductor device, wherein the adhesive layer contains a carboxyl group-containing acrylonitrile-butadiene copolymer (a), an epoxy resin (b), and a compound (c) containing two or more maleimide groups, and has a storage modulus at 80°C of 1 MPa to 1.7 MPa; The component (a) is a carboxyl group-containing acrylonitrile-butadiene copolymer having an acrylonitrile content of 5 to 50 mass% and a carboxyl group equivalent weight calculated from the number average molecular weight of 100 to 20,000, the total amount of the component (b) and the component (c) is 20 to 300 parts by mass relative to 100 parts by mass of the component (a); the mass ratio of the component (c) to the component (b) ((b) / (c)) is in the range of 0.1 to 10; An adhesive sheet for production of semiconductor device, wherein the ratio of the amount of glycidyl groups based on the component (b) to the amount of carboxyl groups based on the component (a) is 0.14 to 0.

43.

2. A method for manufacturing a semiconductor device using the adhesive sheet for manufacturing a semiconductor device according to claim 1, comprising: a bonding step of bonding an adhesive sheet for manufacturing a semiconductor device to a lead frame or a wiring board; a die-attach step of mounting a semiconductor element on the lead frame or wiring substrate; a wire bonding step of electrically connecting the semiconductor element to an external connection terminal; a sealing step of sealing the semiconductor element with a sealing resin; A method for manufacturing a semiconductor device, comprising, after the sealing step, a peeling step of peeling the adhesive sheet for manufacturing a semiconductor device from the lead frame or the wiring substrate.

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