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

Abstract

This invention relates to an adhesive sheet for manufacturing semiconductor devices. The adhesive sheet comprises a substrate and a thermosetting adhesive layer disposed on one surface of the substrate, and is peelably attached to a lead frame or wiring substrate of a semiconductor device. In this adhesive sheet, the adhesive layer contains a carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the following structural formula (1) (b), a compound containing two or more maleimide groups (c), and a reactive siloxane compound (d). Furthermore, this invention provides a method for manufacturing a semiconductor device using the same.

Description

Technical Field

[0001] This invention relates to an adhesive sheet suitable for use as a mask tape when assembling semiconductor devices using the QFN (Quad Flat Non-lead) method, and a method for manufacturing semiconductor devices using the same.

[0002] This application is based on and claims the priority of Japanese Patent Application No. 2017-017490, filed in Japan on February 2, 2017, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, in contrast to the demand for miniaturization, thinning, and multifunctionality of IT devices, especially mobile phones, the demand for further high-density mounting technologies in semiconductor devices (semiconductor packages) has been increasing.

[0004] QFN technology has attracted attention as a CSP (Chip Size Package) technology that meets this requirement (see Patent Document 1 and Patent Document 2), and is widely used, especially in low-pin types with fewer than 100 pins.

[0005] Here, a general assembly method for QFN packaging using the QFN method is known as follows: First, in the mounting process, an adhesive pad is attached to one surface of the lead frame. Next, in the chip bonding process, semiconductor components such as IC chips are mounted on multiple semiconductor component mounting portions (chip pad portions) formed on the lead frame. Next, in the wire bonding process, multiple leads arranged along the outer periphery of each semiconductor component mounting portion of the lead frame and the semiconductor components are electrically connected using bonding wires. Finally, in the sealing process, the semiconductor components mounted on the lead frame are sealed using a sealing resin.

[0006] Next, in the stripping process, by peeling the adhesive tabs from the lead frame, a QFN cell with multiple QFN packages arranged together can be formed. Finally, in the dicing process, by cutting the QFN cell along the outer periphery of each QFN package, multiple QFN packages can be manufactured.

[0007] For adhesive sheets used in this application, the following requirements apply: they must adhere fully and stably without peeling off from the back of the lead frame and the back of the sealant until the peeling process, and they must be easily peeled off during the peeling process without any adhesive residue on the back of the lead frame and / or the back of the sealant, or any defects such as breakage of the adhesive sheet.

[0008] In recent years, in particular, copper alloy leadframes have been used to reduce the cost of semiconductor devices. These copper alloy leadframes also act as catalysts for the oxidative degradation of polymer materials by the transition metal copper. Due to the thermal history accompanying QFN package assembly after the tape coating process, the adhesive is easily oxidized and degraded, leading to re-peeling and residual adhesive during wafer peeling.

[0009] However, the existing adhesive pads are not sufficiently advanced enough to be used in practical applications for lead frames made of copper alloys.

[0010] For example, in existing adhesive sheets, there are adhesive sheets in the form of an adhesive layer containing an acrylonitrile-butadiene copolymer and a bismaleimide resin laminated on a substrate made of a heat-resistant film (see Patent Document 3). However, when using such an adhesive sheet, the following problems arise: due to the heat applied during the chip bonding curing process after the adhesive film coating process, the wire bonding process, and the resin sealing process, the acrylonitrile-butadiene copolymer is prone to deterioration, making it difficult to peel off during the peeling process, or causing the adhesive sheet to break or leave adhesive residue.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2003-165961

[0014] Patent Document 2: Japanese Patent Application Publication No. 2005-142401

[0015] Patent document 3: Japanese Patent Application Publication No. 2008-095014. Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] The present invention was made in view of the above circumstances, and aims to provide an adhesive sheet and a method for manufacturing a semiconductor device using the same, wherein the adhesive sheet, even under the thermal stress associated with QFN assembly prior to the peeling process, can be fully and stably attached without peeling off from the back of the lead frame and the back of the sealing resin, and without leakage of the sealing resin, and can be easily peeled off during the peeling process without adhesive residue or breakage.

[0018] Solution for solving the problem

[0019] The adhesive sheet for manufacturing semiconductor devices of the present invention comprises a substrate and a thermosetting adhesive layer disposed on one surface of the substrate, and is peelably attached to the lead frame or wiring substrate of a semiconductor device. The adhesive sheet for manufacturing semiconductor devices is characterized in that the adhesive layer contains a carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the following structural formula (1) (b), a compound containing two or more maleimide groups (c), and a reactive siloxane compound (d).

[0020] [Chemical Formula 1]

[0021]

[0022] In addition, component (a) is preferably a carboxyl-containing acrylonitrile-butadiene copolymer with an acrylonitrile content of 5% to 50% by mass and a carboxyl equivalent of 100 to 20,000 calculated from the number average molecular weight.

[0023] The total amount of components (b), (c), and (d) is preferably 30 to 300 parts by mass relative to 100 parts by mass of component (a).

[0024] In addition, the mass ratio of component (c) to component (b) ((c) / (b)) is preferably in the range of 0.1 to 10.

[0025] Furthermore, the ratio of the reactive base number of component (d) to the total number of epoxy groups in component (b) and maleimide base number in component (c) is preferably 0.05 to 1.2.

[0026] Furthermore, the semiconductor device manufacturing method of the present invention is characterized in that it is a method for manufacturing a semiconductor device using the above-described semiconductor device manufacturing adhesive sheet, comprising: an attachment step, wherein the semiconductor device manufacturing adhesive sheet is attached to a lead frame or wiring substrate; a chip bonding step, wherein a semiconductor element is mounted on the lead frame or wiring substrate; a wire bonding step, wherein the semiconductor element and an external connection terminal are connected; a sealing step, wherein the semiconductor element is sealed with a sealing resin; and a peeling step, wherein the semiconductor device manufacturing adhesive sheet is peeled off from the lead frame or wiring substrate after the sealing step.

[0027] Invention Effects

[0028] According to the present invention, an adhesive sheet and a method for manufacturing a semiconductor device using the same are provided. The adhesive sheet can be fully and stably attached to the back of the lead frame and the back of the sealing resin without peeling off before the peeling process, even under the thermal stress associated with QFN assembly, without leakage of the sealing resin. Moreover, it can be easily peeled off during the peeling process without adhesive residue or breakage. Attached Figure Description

[0029] Figure 1 This is a top view illustrating an example of a lead frame used in a method for manufacturing a semiconductor device according to the present invention.

[0030] Figure 2 A process diagram illustrating the manufacturing method of the semiconductor device of the present invention. Detailed Implementation

[0031] The present invention will now be described in detail.

[0032] [Adhesive tape for semiconductor device manufacturing]

[0033] The semiconductor device manufacturing adhesive sheet (hereinafter referred to as the adhesive sheet) of the present invention comprises a substrate and a thermosetting adhesive layer disposed on one surface of the substrate, and is peelably attached to the lead frame or wiring substrate of the semiconductor device. In the adhesive sheet, the adhesive layer contains a carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the following structural formula (1) (b), a compound containing two or more maleimide groups (c), and a reactive siloxane compound (d). The adhesive sheet is used as a mask tape when assembling a semiconductor device by QFN method.

[0034] [Chemical Formula 2]

[0035]

[0036] The carboxyl-containing acrylonitrile-butadiene copolymer (a) plays a role in maintaining the melt viscosity of the adhesive layer at the initial stage of heating, and imparts good flexibility and adhesion to the cured adhesive layer. By containing this component, an adhesive layer with good adhesion to substrates such as heat-resistant films and without cracks can be formed. As the carboxyl-containing acrylonitrile-butadiene copolymer (a), known substances can be used without restriction, preferably substances with an acrylonitrile content of 5% to 50% by mass, more preferably substances with an acrylonitrile content of 10% to 40% by mass. If the acrylonitrile content is lower than the above range, the solubility in solvents or the compatibility with other components decreases, and therefore there is a tendency for the uniformity of the resulting adhesive layer to decrease. On the other hand, if the acrylonitrile content exceeds the above range, the adhesion of the resulting adhesive layer to the lead frame or sealing resin becomes excessive, and when it is used for adhesive sheets, it may be difficult to peel off in the peeling process, or the adhesive sheet may break.

[0037] The carboxyl equivalent of the acrylonitrile-butadiene copolymer containing carboxyl groups, calculated from the number average molecular weight, is preferably in the range of 100 to 20,000, more preferably 200 to 10,000. If the carboxyl equivalent is below the above range, the reactivity with other components is too high, and there is a tendency for the storage stability of the resulting adhesive layer to decrease. On the other hand, if the carboxyl equivalent exceeds the above range, the reactivity with other components is insufficient, and therefore the resulting adhesive layer is prone to being in a low B stage (sub-semi-cured state). As a result, when it is used for adhesive sheets, during the initial heating stage, i.e., during the adhesive sheet attachment process or chip bonding curing treatment, when the adhesive sheet is heated, there is a tendency for the adhesive layer to become low in viscosity, for bubbling or flow-out to easily occur in the adhesive layer, and for the thermal stability of the adhesive layer to decrease.

[0038] It should be noted that the carboxyl equivalent calculated from the number average molecular weight is obtained by dividing the number average molecular weight (Mn) by the number of carboxyl groups (functional groups) per molecule, as expressed by the following formula.

[0039] Carboxyl equivalent = Mn / number of functional groups

[0040] Epoxy resin (b) and a compound (c) containing two or more maleimide groups provide the thermosetting properties of the adhesive layer. By using them together, an adhesive layer with excellent thermal stability can be formed that can be easily peeled off during the peeling process without leaving residue or breaking. In particular, epoxy resin (b) imparts toughness to the adhesive layer, and by containing this component, residue caused by adhesive layer cracking during the peeling process can be suppressed.

[0041] Compound (c) containing two or more maleimide groups imparts thermal stability to the adhesive layer and plays a role in adjusting the adhesive properties of the adhesive layer. By containing this component, the adhesive properties can be moderately controlled, thereby forming an adhesive layer that can be easily peeled off during the peeling process.

[0042] As a specific example of a compound (c) containing two or more maleimide groups, it is preferable to use a compound that constitutes a bismaleimide resin, such as compounds of formulas (2-1) to (2-3), among which compounds of formulas (2-1) or (2-3) are particularly useful in terms of solvent solubility.

[0043] [Chemical Formula 3]

[0044]

[0045] Reactive siloxane compounds (d) are used to improve the compatibility of the components constituting the adhesive layer, while also improving the peelability of the adhesive layer from the sealing resin. By including this component, a uniform adhesive layer can be formed with good compatibility of the components, without defects such as component separation or precipitation. As a result, the adhesive layer exhibits uniform adhesive strength, suppressing defects such as reduced peelability and residual adhesive caused by localized high adhesive strength.

[0046] As the reactive siloxane compound (d), siloxane compounds with reactive groups such as amino-modified, epoxy-modified, carboxyl-modified, and mercapto-modified groups can be used without restriction. Among them, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, aminopropyl-terminated dimethylsiloxane tetramers or octamers, and bis(3-aminophenoxymethyl)tetramethyldisiloxane are preferred in terms of rapid reaction with components (b) and (c). From the viewpoint of reactivity, compounds with reactive groups attached to both ends of the siloxane structure are preferred as the reactive siloxane compound (d), but compounds with single ends or silane coupling agents with one end being reactive and the other end being non-reactive can also be used.

[0047] It should be noted that each of the components in (a) to (d) above can be a substance composed of one compound or a mixture of two or more compounds.

[0048] The ratio of each component is such that, relative to 100 parts by mass of component (a), the total of components (b), (c), and (d) is preferably 30 to 300 parts by mass, more preferably 30 to 200 parts by mass. If the total of components (b), (c), and (d) is lower than the above range, the reactivity of the adhesive layer decreases, making it difficult to remain insoluble and unmelted even upon heating, and there is a tendency for increased adhesion due to decreased thermal stability. On the other hand, if the above range is exceeded, the melt viscosity of the adhesive layer is insufficient at the initial stage of heating, and in adhesive sheets using this adhesive layer, the adhesive layer may flow out or bubble during chip bonding and curing processes after the film coating process.

[0049] Furthermore, the mass ratio of component (c) to component (b) ((c) / (b)) is preferably in the range of 0.1 to 10, and more preferably in the range of 1 to 7. Below this range, the resulting adhesive layer may readily undergo a curing reaction at room temperature and lack storage stability, or the adhesive force may be too strong, making it impossible to peel off or causing the adhesive sheet to break during the peeling process. On the other hand, if the range exceeds the above range, during the manufacture of the adhesive sheet, the adhesion between the adhesive layer and the substrate composed of the heat-resistant film may decrease, or the adhesive layer may bubble, or the resulting adhesive sheet may easily leave adhesive residue.

[0050] Furthermore, the ratio of the reactive group of component (d) to the total number of epoxy groups in component (b) and maleimide groups in component (c) is preferably 0.05 to 1.2, more preferably 0.1 to 0.8. Below this range, the overall reactivity of the adhesive layer decreases, making it difficult to perform the curing reaction in chip bonding and curing processes, resulting in excessively strong adhesion. On the other hand, if the above range is exceeded, the reaction proceeds excessively, easily causing problems such as gelation during adhesive layer preparation, and the adhesion tends to weaken.

[0051] In addition to the essential components (a) to (d), reaction promoters such as organic peroxides, imidazoles, and triphenylphosphine can be added to the adhesive layer. These additions can also help maintain the adhesive layer in a favorable B-stage at room temperature.

[0052] Furthermore, to control melt viscosity, improve thermal conductivity, and impart flame retardancy, fillers with an average particle size of 1 μm or less can be added. Examples of fillers include inorganic fillers such as silica, alumina, magnesium oxide, aluminum nitride, boron nitride, titanium oxide, calcium carbonate, and aluminum hydroxide; and organic fillers such as silicone resin and fluororesin. When using fillers, their content is preferably 1% to 40% by mass of the adhesive layer.

[0053] The adhesive sheet of the present invention has the above-mentioned adhesive layer formed on one side of the heat-resistant film, which serves as a substrate.

[0054] In manufacturing this adhesive sheet, firstly, an adhesive coating is prepared, consisting of at least the aforementioned carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the aforementioned structural formula (1) (b), a compound containing two or more maleimide groups (c), a reactive siloxane compound (d), and a solvent. Next, the coating is applied to one side of the heat-resistant film with a thickness preferably of 1 μm to 50 μm, more preferably 3 μm to 20 μm, after drying, 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 can be manufactured by applying the coating to the protective film, drying it to form the adhesive layer, and then providing the heat-resistant film thereon. It should be noted that the protective film is peeled off when the adhesive sheet is used.

[0055] Examples of heat-resistant films include heat-resistant plastic films composed of polyimide, polyphenylene sulfide, polyethersulfone, polyetheretherketone, liquid crystal polymers, polyethylene terephthalate, polyethylene naphthalate, etc.; composite heat-resistant films such as epoxy resin-glass cloth, etc., with polyimide films being particularly preferred.

[0056] The thickness of the polyimide film is preferably from 12.5 μm to 125 μm, more preferably from 25 μm to 50 μm. If it is below the above range, the adhesive sheet tends to be insufficiently tough and difficult to handle; if it exceeds the above range, the coating or peeling process during QFN assembly tends to become difficult.

[0057] As a solvent for adhesive coatings, one or more of the following are preferred: organic solvents such as hydrocarbons, alcohols, ketones, and ethers (tetrahydrofuran, etc.) and water. The amount used should be adjusted appropriately to achieve a suitable coating viscosity. Furthermore, the coating can be in the form of a solution, emulsion, or suspension, and the appropriate form should be selected based on the coating equipment used and environmental conditions.

[0058] Examples of peelable protective films include plastic films such as polyethylene, polypropylene, vinyl chloride, fluorinated resins, and silicone, or films that are made peelable by coating polyethylene terephthalate, polyethylene naphthalate, paper, etc. with silicone.

[0059] [Semiconductor device manufacturing method]

[0060] A method for manufacturing a semiconductor device using the adhesive sheet of the present invention includes: an attachment step, in which an adhesive sheet is attached to a lead frame or a wiring substrate; a chip bonding step, in which a semiconductor element is mounted on the lead frame or the wiring substrate; a wire bonding step, in which the semiconductor element and an external connection terminal are made conductive; a sealing step, in which the semiconductor element is sealed with a sealing resin; and a peeling step, in which the adhesive sheet is peeled off from the lead frame or the wiring substrate after the sealing step.

[0061] The following is for reference Figures 1 to 2 An example of a method for manufacturing a semiconductor device using the adhesive sheet of the present invention will be described. Figure 1 This is a top view of the lead frame as seen from the side where the semiconductor components are mounted. Figure 2 (a) through (f) are examples of the use of Figure 1 The diagram shown illustrates the process of manufacturing a QFN package using a lead frame. Figure 1 A-A' sectional view of the lead frame.

[0062] First, prepare Figure 1 The schematic diagram shows a lead frame 20. The lead frame 20 is formed in a matrix of multiple semiconductor element mounting portions (chip pad portions) 21 that mount semiconductor elements such as IC chips, and multiple leads 22 (external connection terminals) are formed along the outer periphery of each semiconductor element mounting portion 21.

[0063] As the material for the lead frame 20, known materials can be cited, such as copper plates and copper alloy plates, or materials on which a contact electroplating layer is provided, or materials on which a nickel plating layer, a palladium plating layer and a gold plating layer are sequentially provided on the surface of a copper alloy plate.

[0064] like Figure 2 As shown in (a), an adhesive sheet 10 is attached to one surface (lower surface) of the lead frame 20 in a manner that the adhesive layer (not shown) abuts against the lead frame 20 (attachment process). Methods for attaching the adhesive sheet 10 to the lead frame 20 include lamination and pressing; from a production point of view, lamination, which allows for continuous adhesive film application, is preferred. The temperature of the adhesive sheet 10 in this process ranges from, for example, room temperature (5°C to 35°C) to 150°C, and more preferably from 60°C to 120°C. If attachment is performed at a temperature higher than 150°C, the lead frame is prone to warping.

[0065] If the lead frame 20 warps during this process, positioning in the chip bonding or wire bonding process becomes difficult, making it hard to transport to the furnace and potentially reducing the productivity of the QFN package.

[0066] like Figure 2 As shown in (b), on the side of the semiconductor component mounting section 21 of the lead frame 20 where the adhesive sheet 10 is not attached, a semiconductor component 30, such as an IC chip, is mounted using a chip adhesive (not shown). At this time, warping of the lead frame 20 is suppressed, making it easier to position. Furthermore, the semiconductor component 30 is accurately positioned according to the specified location. Then, the chip adhesive is cured by heating to approximately 100°C to 200°C, fixing the semiconductor component 30 and mounting it on the semiconductor component mounting section 21 (chip adhesive curing process. This is the chip bonding process). At this time, the adhesive layer of the adhesive sheet 10 cures and adheres to the lead frame.

[0067] If exhaust components from the adhesive pad 10 or chip adhesive adhere to the lead frame 20 or semiconductor element 30, poor wire bonding can easily occur during the wire bonding process, leading to a decrease in yield. Therefore, after the chip bonding process and before the wire bonding process, plasma treatment (plasma cleaning process) is performed on the lead frame 20 or semiconductor element 30. For example, a plasma treatment method can be used to irradiate the lead frame 20 (hereinafter sometimes referred to as a semi-finished product) with the adhesive pad 10 attached and the semiconductor element 30 mounted under it with plasma in an atmosphere such as argon or a mixture of argon and hydrogen. The plasma irradiation output during plasma treatment is, for example, 150W to 600W. Furthermore, the plasma treatment time is, for example, 0.1 minutes to 15 minutes.

[0068] like Figure 2As shown in (c), the semiconductor element 30 and the leads 22 (external connection terminals) of the lead frame 20 are electrically connected by bonding leads 31, such as gold leads, copper leads, and palladium-coated copper leads (wire bonding process). This process is performed while the semi-finished product is heated to approximately 150°C to 250°C on a heating block. The heating time in this process is, for example, 5 minutes to 60 minutes.

[0069] If the semi-finished product is heated during the wire bonding process, the fluorine additive in the adhesive layer will transfer to the surface of the adhesive layer, thus making it easy to peel the adhesive sheet 10 off from the lead frame 20 and the sealing resin 40 during the peeling process described later.

[0070] like Figure 2 As shown in (d), Figure 2 (c) The semi-finished product shown is placed in a mold, and a sealing resin (molding material) is injected into the mold. After filling the mold with any amount, the mold is maintained at any pressure, thereby sealing the semiconductor element 30 with the sealing resin 40 (sealing process). As the sealing resin, a known resin is used, such as a mixture of epoxy resin and inorganic fillers.

[0071] like Figure 2 As shown in (e), by peeling the adhesive sheet 10 from the sealing resin 40 and the lead frame 20, a QFN unit 60 with a plurality of QFN packages 50 arranged is obtained (peeling process).

[0072] like Figure 2 As shown in (f), multiple QFN packages 50 are obtained by cutting QFN units 60 along the outer periphery of each QFN package 50 (cutting process).

[0073] It should be noted that, in the above embodiments, the manufacturing method of a QFN package using a lead frame was described as an example, but the present invention is not limited thereto, and can also be applied to manufacturing methods of semiconductor devices other than those using QFN packages using lead frames, and manufacturing methods of semiconductor devices using wiring substrates.

[0074] In the adhesive sheet of the present invention, the adhesive layer is crosslinked with the carboxyl groups of a carboxyl-containing acrylonitrile-butadiene copolymer (a) and the glycidyl groups of epoxy resin (b) to form a B-stage state (semi-cured state), thereby enabling a lower glass transition temperature (10°C to 50°C). The adhesive sheet with an adhesive layer having a lower glass transition temperature can undergo a continuous coating process using a roller laminator or similar equipment under relatively low heating conditions, specifically at 60°C to 150°C, resulting in excellent productivity.

[0075] Furthermore, the adhesive layer in the adhesive sheet of the present invention, with a lower glass transition temperature (10°C to 50°C), can achieve a high elastic modulus when heated. In recent years, products using low-cost copper wires or palladium-coated copper wires for bonding, replacing conventional gold wires, have become increasingly popular in order to reduce costs in the wire bonding process. Since copper wires or palladium-coated copper wires are metals with higher elasticity than gold, they require processing under higher loads than conventional gold wires to achieve stable shapes.

[0076] If such a large load is applied to the leadframe, and the adhesive layer in the adhesive sheet attached to the lower part of the leadframe has a low elastic modulus, the adhesive layer will deform and the resin will be sealed in this deformed state. This results in leakage of the sealing resin from the deformed adhesive layer portion. Furthermore, when the adhesive sheet is peeled off from the leadframe, the adhesive layer breaks off from the deformed adhesive layer portion, leaving adhesive residue on the leadframe surface. In addition, during wire bonding, if the adhesive has a low elastic modulus, deformation of the adhesive makes it difficult to transfer the lead load, easily leading to poor wire bonding. The adhesive layer in the adhesive sheet of the present invention has a high elastic modulus as described above, therefore, even when using copper leads or palladium-coated copper leads for wire bonding, problems such as poor wire bonding, sealing resin leakage, or adhesive layer residue are less likely to occur.

[0077] Furthermore, since the adhesive layer in the adhesive sheet of the present invention has a compound (c) containing two or more maleimide groups, the curing of the adhesive layer can be appropriately controlled during the drying process when the adhesive sheet is manufactured, thereby enabling the adhesive layer to be in a high B stage (deep semi-cured) state. Therefore, the adhesion strength to the lead frame is suppressed, and as a result, the leakage of sealing resin, adhesive residue on the lead frame, and breakage of the adhesive layer during peeling can be suppressed.

[0078] Example

[0079] The present invention will be specifically illustrated below with examples.

[0080] [Examples 1 to 6 and Comparative Examples 1 to 4]

[0081] (Composition of adhesive coatings)

[0082] Adhesive coatings were prepared by mixing components (a) to (d) and other components with tetrahydrofuran (THF) as a solvent at the mass ratios shown in Table 1.

[0083] Next, the adhesive coating was applied to one side of a 25μm thick polyimide film (manufactured by Toray DuPont, trade name Kapton100EN) with a dried adhesive layer thickness of 5μm, and then dried in a hot air circulating oven set at 180°C to obtain an adhesive sheet.

[0084] It should be noted that the details of each ingredient used are as follows.

[0085] • Carboxyl-containing acrylonitrile-butadiene copolymer: Carboxyl equivalent of 1500 (calculated from number average molecular weight), acrylonitrile content of 27% by mass

[0086] Acrylonitrile-butadiene copolymer: Acrylonitrile content 27% by mass

[0087] • Epoxy resin with structural formula (1): molecular weight 630, functional group equivalent 210 g / eq

[0088] Bisphenol A diphenyl ether bismaleimide: molecular weight 570, functional group equivalent 285 g / eq

[0089] ·1,3-Bis(3-aminopropyl)tetramethyldisiloxane: Molecular weight 248, functional group equivalent 62 g / eq

[0090] [Table 1]

[0091]

[0092] For the adhesive sheets obtained as described above, the following were conducted: (1) peel strength to lead frame material, (2) thermal properties after chip bonding process, (3) peel strength to sealing resin material and presence or absence of adhesive residue after sheet peeling, and (4) presence or absence of sealing resin leakage in the test piece after resin sealing process.

[0093] (1) Peel strength of lead frame material

[0094] (i) Preparation of test subjects

[0095] The adhesive sheets obtained in each example were cut to a width of 50mm and a length of 60mm, and then bonded to a test lead frame (surface impact plated, 8×8 matrix array, package size 5mm×5mm, 32 pins) made of copper alloy with an external dimension of 57.5mm×53.5mm using a roller laminator as the test subject. The lamination conditions at this time were a temperature of 80℃, a pressure of 4N / cm, and a lamination speed of 1m / min.

[0096] (ii) Determination of peel strength

[0097] For the test specimens described above, the 90° peel strength was determined using a universal tensile testing machine. It should be noted that the test was conducted by fixing the lead frame and stretching the adhesive sheet vertically. The tensile speed was 50 mm / min. The results are shown in Table 2.

[0098] (2) Thermal properties after chip bonding process

[0099] In the adhesive sheets obtained in each example, an adhesive sheet was made by using a 25 μm thick polyimide film as a 38 μm thick polyethylene terephthalate (PET) film that had undergone a demolding treatment. Assuming that chip bonding and curing treatment was performed, the film was heated at 175°C for 1 hour using a ventilated oven.

[0100] The adhesive layer was removed from the heated adhesive sheet from the PET film, and the tensile storage modulus was determined using a DMA (Dynamic Mechanical Analyzer). As a DMA, measurements were performed using a Vibron measuring instrument (Orientec, RHEOVIBRON DDV-II-EP) at a frequency of 11 Hz, a heating rate of 10 °C / min, and a load of 1.0 gf. The results for the tensile storage modulus at 180 °C, assuming the temperatures involved in the wire bonding process, are shown in Table 2.

[0101] (3) Peel strength of the test specimen after resin sealing process and presence or absence of adhesive residue after peeling.

[0102] (i) Preparation and heat treatment of test specimens

[0103] Assuming that the adhesive sheet obtained in each example is subject to the thermal history of the actual QFN assembly, the following (a) to (d) were performed sequentially.

[0104] (a) The adhesive sheets obtained in each example were cut to a width of 50 mm × a length of 60 mm and bonded to a test lead frame (surface contact plating, 8 × 8 matrix arrangement, package size 5 mm × 5 mm, 32 pins) made of copper alloy with an external dimension of 57.5 mm × 53.5 mm using a roller laminator. The lamination conditions at this time were a temperature of 80°C, a pressure of 4 N / cm, and a lamination speed of 1 m / min.

[0105] (b) The copper alloy test lead frame with the adhesive pad attached was heated to 175°C for 1 hour using a ventilated oven. This is a process assuming chip bonding and curing.

[0106] (c) Plasma irradiation treatment: 450W / 60 seconds was applied using a 1000P plasma manufactured by Yield Engineering, with Ar gas.

[0107] (d) Heating to 200°C for 30 minutes: This is a process that assumes the wire bonding process is performed using a hot plate.

[0108] Next, on the exposed copper surface opposite to the surface of the adhesive sheet to which the heat-treated (a) to (d) adhered, a sealing resin is laminated using a molding machine at 175°C for 3 minutes (resin sealing process). Epoxy molding resin (EME-G631BQ) manufactured by Sumitomo Bakelite Co., Ltd. was used as the sealing resin.

[0109] (ii) Determination of peel strength and presence or absence of adhesive residue after peeling.

[0110] For the test specimens after the resin sealing process described above, the 90° peel strength was determined using a universal tensile testing machine. It should be noted that the test specimens were fixed and the corner portions of the adhesive sheet were stretched vertically for the measurement. The stretching speed was 300 mm / min. Furthermore, the presence or absence of adhesive residue after peeling was confirmed using an optical microscope (Keyence VHX-500 digital microscope) at 100x magnification. The results are shown in Table 2.

[0111] (4) Whether there is any leakage of sealing resin in the test specimen after the resin sealing process.

[0112] For the test specimens after the above resin sealing process, the presence or absence of sealing resin leakage was confirmed using an optical microscope (Keyence VHX-500 digital microscope) at 100x magnification. The results are shown in Table 2.

[0113] It should be noted that the marks in the judgment column of Table 2 represent the following content.

[0114] (1) Determination of peel strength of lead frame material

[0115] ○: Peel strength is above 10gf / 50mm.

[0116] △: Peel strength is above 5gf / 50mm and less than 10gf / 50mm.

[0117] ×: Peel strength less than 5gf / 50mm.

[0118] (2) Thermal properties after chip bonding process

[0119] ○: The tensile energy storage elastic modulus at 180℃ is above 10MPa.

[0120] △: The tensile energy storage elastic modulus at 180℃ is greater than 1MPa and less than 10MPa.

[0121] ×: Tensile energy storage elastic modulus at 180℃ is less than 1MPa

[0122] (3) Peel strength of the test specimen after resin sealing process and presence or absence of adhesive residue after peeling.

[0123] ○: Peel strength is less than 1000gf / 50mm, the peeled adhesive is not broken, and there is no adhesive residue on the lead frame material surface and the sealing resin surface.

[0124] △: The peel strength is above 1000gf / 50mm, the peeled adhesive is not broken, and there is no adhesive residue on the surface of the lead frame material and the sealing resin.

[0125] ×: Meets the condition of observing at least one of the following: adhesive patch breakage or adhesive residue on the lead frame material surface and sealing resin surface.

[0126] (4) Whether there is any leakage of sealing resin in the test specimen after the resin sealing process.

[0127] ○: On the surface of the test lead frame material after the adhesive pad has been peeled off and the resin has been sealed, there was no leakage of the sealing resin.

[0128] ×: The sealing resin leaked on the surface of the test lead frame material after the adhesive pads had been peeled off and the resin sealing had been completed.

[0129] [Table 2]

[0130]

[0131] As can be seen from Table 2 above, the adhesive sheets of Examples 1 to 6 have a peel strength of 5gf / 50mm or more on the copper alloy test lead frame, and have excellent adhesion to the lead frame material.

[0132] Furthermore, it was confirmed that the adhesive sheets of Examples 1 to 6 have a tensile energy storage modulus of 10 MPa or more at 180°C, and possess the characteristic of being able to sufficiently withstand the deformation of the adhesive layer caused by the load during the wire bonding process. In addition, the adhesive sheets of Examples 1 to 6 have the following excellent characteristics: the sealing resin will not leak, the substrate and adhesive layer of the adhesive sheet will not crack, and no adhesive residue will remain on the surface of the lead frame material or the sealing resin.

[0133] In contrast, it was confirmed that the tensile storage modulus of the adhesive sheets in Comparative Examples 1, 2, and 4 at 180°C was less than 10 MPa, making it difficult to withstand the deformation of the adhesive layer caused by the load during the wire bonding process. Furthermore, the adhesive sheets of Comparative Examples 1 to 4 broke when peeled from the sealing resin material, and even in areas where peeling was possible, adhesive residue remained on the surface of the lead frame material and the peeling sealing resin.

[0134] Industrial applications

[0135] The adhesive sheet of the present invention is suitable for use as a mask tape when assembling semiconductor devices using the QFN (Quad Flat Non-lead) method. According to the present invention, the adhesive sheet adheres fully and stably without peeling off from the back of the lead frame and the back of the sealing resin, even under the heat generated during QFN assembly, until the peeling process, without leakage of the sealing resin. Furthermore, it can be easily peeled off during the peeling process without adhesive residue or breakage. In addition, the adhesive sheet of the present invention is suitable for the manufacture of semiconductor devices.

[0136] Explanation of reference numerals in the attached figures

[0137] 10 Adhesive sheet for semiconductor device manufacturing; 20 Lead frame; 30 Semiconductor element; 31 Bonding wire; 40 Sealing resin; 50 QFN package.

Claims

1. An adhesive sheet for manufacturing a semiconductor device, the adhesive sheet comprising a substrate and a thermosetting adhesive layer disposed on one surface of the substrate, and being peelably attached to a lead frame or wiring substrate of a semiconductor device, characterized in that... The adhesive layer contains a carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the following structural formula (1) (b), a compound containing two or more maleimide groups (c), a reactive siloxane compound (d), and fluorine additives. [Chemical Formula 1] The glass transition temperature of the adhesive layer is between 10°C and 50°C. The component (a) is a carboxyl-containing acrylonitrile-butadiene copolymer with an acrylonitrile content of 5% to 50% by mass and a carboxyl equivalent of 100 to 20,000 calculated from the number average molecular weight. Relative to 100 parts by weight of component (a), the total of components (b), (c), and (d) is 30 to 300 parts by weight. (c) The mass ratio of component (c) to component (b) is in the range of 0.1 to 10. The ratio of the reactive base number of component (d) to the sum of the number of epoxy groups in component (b) and the number of maleimide groups in component (c) is from 0.05 to 1.

2.

2. A method for manufacturing a semiconductor device, characterized in that, The manufacturing method uses the adhesive sheet for manufacturing semiconductor devices according to claim 1, and the manufacturing method comprises: The bonding process is used to attach adhesive sheets for semiconductor device manufacturing to lead frames or wiring substrates. Chip bonding process, used to mount semiconductor components on the lead frame or wiring substrate; The wire bonding process is used to make the semiconductor element and the external connection terminal conductive; A sealing process is performed to seal the semiconductor element with a sealing resin; as well as A stripping process is used to peel off the adhesive sheet for semiconductor device manufacturing from the lead frame or wiring substrate after the sealing process.

Images