bonding materials for semiconductor device manufacturing and manufacturing methods for semiconductor devices using them

Abstract

This invention provides an adhesive sheet and a method for manufacturing a semiconductor device using it. Even when subjected to the thermal process accompanying QFN assembly before the peeling step, the adhesive sheet will not peel off from the back of the lead frame and the back of the sealing resin, and can be fully and stably attached to them without sealing resin leakage. Furthermore, it can be easily peeled off during the peeling step without adhesive residue or cracking. The adhesive sheet for semiconductor device manufacturing of this invention comprises a substrate and a thermosetting adhesive layer disposed on one side of the substrate, and is an adhesive sheet for semiconductor device manufacturing that can be peelably attached to the lead frame or wiring substrate of a semiconductor device. In the adhesive sheet of this invention, the aforementioned 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 maleic anhydride groups (c); and a latent curing agent (d).

Description

Technical Field

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

[0002] Background Technology In recent years, IT devices, led by mobile phones, have become increasingly smaller, thinner, and more multifunctional. To meet these demands, the necessity of higher-density mounting technology for semiconductor devices (semiconductor packages) is increasing. Regarding CSP (Chip Size Package) technology that responds to this demand, the QFN method has attracted attention (see Patent Document 1 and Patent Document 2), especially in the manufacture of low-pin semiconductor devices with fewer than 100 pins.

[0003] Regarding the assembly method of a typical QFN package using the QFN method, the following methods are generally known. First, in the attachment step, an adhesive sheet is attached to one side of the lead frame. Next, in the die attach step, semiconductor devices such as IC chips are mounted one by one on the plurality of semiconductor device mounting portions (die pads) already formed on the lead frame. Next, in the wire bonding step, a plurality of leads arranged along the outer periphery of each semiconductor device mounting portion of the lead frame are electrically connected to the semiconductor devices using bonding wires. Finally, in the sealing step, the semiconductor devices mounted on the lead frame are sealed with sealing resin. Next, in the peeling step, the bonding sheet is peeled off from the lead frame, thereby forming a QFN cell with a plurality of QFN packages arranged together. Finally, in the dicing step, the QFN cell is diced along the periphery of each QFN package, thereby manufacturing a plurality of QFN packages.

[0004] The adhesive sheet used for this purpose is required to have the following characteristics: it can be fully and stably attached without peeling off from the back of the lead frame and the back of the sealant before the peeling step, and it can be easily peeled off during the peeling step without any adhesive residue or adhesive sheet breakage on the back of the lead frame and the back of the sealant. In particular, in recent years, in order to reduce the cost of semiconductor devices, lead frames made of copper alloys have been increasingly used. When using adhesive sheets for such copper alloy lead frames, the reason is that copper, which is a transition metal constituting the lead frame, has a catalytic effect on the oxidation and degradation of polymer materials. Therefore, after the tapering step, due to the thermal process accompanying the assembly of the QFN package, the adhesive of the polymer material is prone to oxidation and degradation. When peeling the adhesive sheet from the lead frame, problems such as re-peeling and residual adhesive will easily occur.

[0005] Therefore, the bonding sheets used to date have not adequately met the practical requirements for use in lead frames made of copper alloys. For example, conventional adhesive sheets have the following form: an adhesive layer is deposited on a substrate made of a heat-resistant film, and the adhesive layer contains an acrylonitrile-butadiene copolymer and a dicis-butadiene imide resin (see Patent Document 3). When using such an adhesive sheet, the acrylonitrile-butadiene copolymer in the adhesive layer is easily degraded due to the heat applied during the adhesive bonding process, the wire bonding process, and the resin sealing process. This can lead to problems such as difficulty in peeling during the peeling process, cracking of the adhesive sheet, and residual adhesive. Prior technology documents Patent documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2003-165961 [Patent Document 2] Japanese Patent Application Publication No. 2005-142401 [Patent Document 3] Japanese Patent Application Publication No. 2008-095014 Summary of the Invention

[0007] Invention Summary The problem the invention aims to solve In view of the above-mentioned reasons, the present invention aims to provide an adhesive sheet having the following characteristics: it will not peel off from the back of the lead frame and the back of the sealing resin even after undergoing the thermal process accompanying QFN assembly, even before the peeling step in the assembly method of the QFN package; it can be fully and stably attached to them without sealing resin leakage; and it can be easily peeled off in the peeling step without adhesive residue or cracking. Furthermore, the present invention aims to provide a semiconductor device manufacturing method using this adhesive sheet. The means used in the research project

[0008] The bonding sheet for manufacturing semiconductor devices of the present invention is characterized in that it is peelably attached to the lead frame or wiring substrate of a semiconductor device, and has a substrate and a thermosetting adhesive layer disposed on one side of the substrate, the thermosetting adhesive layer containing a carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the following structural formula (1) (b), a compound containing two or more maleic anhydride groups (c), and a latent curing agent (d).

[0009] [Chemical Formula 1]

[0010] In addition, the aforementioned acrylonitrile-butadiene copolymer (a) containing carboxyl groups is preferably an acrylonitrile-butadiene copolymer containing carboxyl groups 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.

[0011] Relative to 100 parts by weight of the aforementioned acrylonitrile-butadiene copolymer (a) containing carboxyl groups, the aforementioned epoxy resin (b), the aforementioned compound containing two or more maleic diimide groups (c), and the aforementioned latent curing agent (d) should preferably total 30 to 300 parts by weight. Furthermore, the aforementioned latent curing agent (d) should preferably be a curing agent whose reaction start temperature with epoxy resin is above 100°C. Furthermore, the method for manufacturing the semiconductor device of the present invention is characterized by comprising the following steps: The attachment step involves attaching the bonding sheet for semiconductor device manufacturing of the present invention onto the lead frame or wiring substrate; The die bonding step involves mounting semiconductor devices on the aforementioned lead frame or wiring substrate; The wire bonding step is to make the aforementioned semiconductor element conductive with the external connection terminal; The sealing step involves sealing the aforementioned semiconductor element with a sealing resin; and The stripping step, which follows the aforementioned sealing step, involves peeling the bonding sheet for semiconductor device manufacturing from the lead frame or wiring substrate. Invention Effects

[0012] According to the present invention, an adhesive sheet can be provided that, even if subjected to the thermal process accompanying QFN assembly before the peeling step, will not peel off from the back of the lead frame and the back of the sealing resin, can be fully and stably attached without leakage of sealing resin, and can be easily peeled off in the peeling step without adhesive residue or breakage. According to the present invention, a method for manufacturing a semiconductor device using the adhesive sheet of the present invention can be further provided. Simple Explanation of the Diagram

[0013] Figure 1 is a top view showing an example of a lead frame used in the semiconductor device manufacturing method of the present invention. Figure 2A is a step diagram illustrating the manufacturing method of the semiconductor device of the present invention. Figure 2B is a step diagram illustrating the manufacturing method of the semiconductor device of the present invention. Figure 2C is a step diagram illustrating the manufacturing method of the semiconductor device of the present invention. Figure 2D is a step diagram illustrating the manufacturing method of the semiconductor device of the present invention. Figure 2E is a step diagram illustrating the manufacturing method of the semiconductor device of the present invention. Figure 2F is a step diagram illustrating the manufacturing method of the semiconductor device of the present invention. Implementation

[0014] Forms used to implement inventions The present invention will now be described in detail below. [Adhesive Sheets for Semiconductor Device Manufacturing] The bonding sheet for semiconductor device manufacturing of the present invention (hereinafter referred to as bonding sheet) comprises a substrate and a thermosetting adhesive layer disposed on one side of the substrate. The bonding sheet of the present invention will be peelably attached to the lead frame or wiring substrate of a semiconductor device. The aforementioned 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 maleic anhydride groups (c), and a latent curing agent (d). The bonding sheet of the present invention is used as a mask tape when assembling a semiconductor device in a QFN manner.

[0015] [Chemical Formula 2]

[0016] The carboxyl-containing acrylonitrile-butadiene copolymer (a) (hereinafter sometimes referred to as component (a)) constituting the adhesive sheet of the present invention functions to maintain an appropriate melt viscosity of the adhesive layer during the initial heating stage, while simultaneously imparting good flexibility and adhesion to the hardened adhesive layer. By including this copolymer, the adhesive sheet of the present invention can form an adhesive layer that exhibits good adhesion to substrates such as heat-resistant films and does not crack. Regarding the carboxyl-containing acrylonitrile-butadiene copolymer (a), conventional materials can be used without limitation, but an acrylonitrile content of 5-50% by mass is preferable, and 10-40% by mass is even better. If the acrylonitrile content is less than the above range, the solubility in solvents and compatibility with other components decrease, and the uniformity of the resulting adhesive layer tends 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 and sealing resin becomes excessive, and when used in the adhesive sheet, there is a possibility that it is difficult to peel off during the peeling step, and the adhesive sheet may crack.

[0017] For acrylonitrile-butadiene copolymers containing carboxyl groups, a carboxyl equivalent calculated from the number average molecular weight in the range of 100 to 20,000 is preferable, with 200 to 10,000 being even better. If the carboxyl equivalent is less than the above range, the reactivity with other components becomes too high, and the storage stability of the resulting adhesive layer tends to decrease. On the other hand, if the carboxyl equivalent exceeds the above range, the reactivity with other components is insufficient, and the resulting adhesive layer is prone to becoming a low-B stage. As a result, when used in adhesive sheets, during the initial heating stage, i.e., the adhesive sheet application step and the crystallization curing treatment, the adhesive layer becomes low in viscosity during heating, which easily causes foaming or flow-out in the adhesive layer, and tends to reduce thermal stability. Additionally, the carboxyl equivalent calculated from the number average molecular weight refers to the value obtained by dividing the number average molecular weight (Mn) by the average number of carboxyl groups (functional groups) per molecule, as shown in the following formula. Carboxyl equivalent = Mn / number of functional groups

[0018] Epoxy resin (b) (hereinafter sometimes also referred to as component (b)) and a compound (c) containing two or more maleic diamide groups are responsible for the thermosetting properties of the adhesive layer. By using them together, an adhesive layer with excellent thermal stability and easy peeling during the peeling process can be formed without residue or breakage. In particular, epoxy resin (b) can impart toughness to the adhesive layer, and by including this component in the adhesive layer, residue caused by adhesive layer cracking during the peeling process can be suppressed.

[0019] Compound (c) containing two or more maleic diimide groups (hereinafter sometimes referred to as component (c)) imparts thermal stability to the adhesive layer while also adjusting the adhesion of the adhesive layer. By containing this component, the adhesion of the adhesive sheet can be appropriately controlled, and an adhesive layer that can be easily peeled off in the peeling step can be formed on the substrate surface. In the case of a compound (c) containing two or more maleic diamide groups, compounds that constitute bismaleimide resins may be used, such as those shown in formulas (2-1) to (2-3) below. Among them, compounds shown in formulas (2-1) or (2-3) below are particularly useful from the viewpoint of solvent solubility.

[0020] [Chemical Formula 3]

[0021] The latent curing agent (d) (hereinafter sometimes also referred to as component (d)) can be incorporated into the adhesive layer to adjust the adhesive layer to a lower B-stage state, thus allowing for adhesive application at low temperatures. Furthermore, in processes such as crystallization curing, the adhesive can undergo a rapid curing reaction and exhibit a high modulus of elasticity by heating at a temperature above the reaction initiation temperature of the latent curing agent (d) it contains. Latent curing agents (d) refer to curing agents whose reaction start temperature with epoxy resin is above 100°C. Examples of such latent curing agents include 2-phenyl-4,5-dihydroxymethylimidazole (manufactured by Shikoku Kasei Corporation, trade name: CUREZOL 2PHZ-PW, reaction start temperature: 150°C) and 2-phenyl-4-methyl-5-hydroxymethylimidazole (manufactured by Shikoku Kasei Corporation, trade name: CUREZOL 2P4MHZ-PW, reaction start temperature: 130°C). Here, the reaction start temperature refers to the temperature at which curing heat is observed when the epoxy resin is mixed and heated. It is measured using DSC (differential scanning calorimetry). The content of the latent curing agent (d) is preferably 0.05 to 20 parts by weight relative to 100 parts by weight of the carboxyl-containing acrylonitrile-butadiene copolymer (a), and more preferably 0.1 to 10 parts by weight. If the content of the latent curing agent (d) is within the above range, the adhesive layer can be adjusted to a lower B-stage state, thus allowing for adhesive application at low temperatures and rapid curing of the adhesive layer during steps such as crystallization and curing.

[0022] Furthermore, for each of the components in (a) to (d) above, any one of them may be a substance composed of one compound or a mixture of two or more compounds.

[0023] Regarding the proportions of each component, relative to 100 parts by mass of component (a), the total of components (b), (c), and (d) should preferably be 30 to 300 parts by mass, more preferably 30 to 200 parts by mass. If the total of components (b), (c), and (d) is less than the above range, the reactivity of the adhesive layer decreases, and it is not easy to achieve non-melting and non-dissolving even through heating. Due to the reduced thermal stability, there is a tendency for increased adhesion. On the other hand, if it exceeds the above range, the melt viscosity of the adhesive layer is insufficient in the initial stage of heating. When using the adhesive layer on the bonded sheet, there is a risk of adhesive layer flow and foaming during the crystallization curing process after the adhesive application step.

[0024] Furthermore, the mass ratio of component (c) to component (b) ((c) / (b)) should preferably be in the range of 0.1 to 10. If it is less than the above range, the resulting adhesive layer is prone to hardening reaction at room temperature, which may lead to poor storage stability and excessively strong adhesion, making the adhesive sheet unable to be peeled off or break during the peeling step. On the other hand, if it exceeds the above range, the adhesion between the adhesive layer and the substrate composed of heat-resistant film may decrease during the manufacturing of the adhesive sheet, and there is a tendency for the adhesive layer to foam and for the resulting adhesive sheet to easily leave adhesive residue.

[0025] The adhesive layer in the bonding sheet for semiconductor device manufacturing of the present invention may further contain a reactive silicone compound. The reactive silicone compound improves the compatibility of the components constituting the adhesive layer and simultaneously improves the peelability of the adhesive layer from the sealing resin. By incorporating this compound into the adhesive layer, a uniform adhesive layer with good compatibility among the components and no defects such as component separation or precipitation can be formed. As a result, the bonding strength of the adhesive layer becomes more uniform, and defects such as reduced peelability and residual adhesive caused by localized variations in bonding strength can be suppressed.

[0026] Regarding reactive siloxane compounds, siloxane compounds that acquire reactivity through amino-, epoxy-, carboxyl-, or mercapto-modification of reactive groups can be used without limitation. Among these, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, aminopropyl-terminated dimethylsiloxane tetrapolymers or ocomers, and bis(3-aminophenoxymethyl)tetramethyldisiloxane are particularly ideal in terms of their ability to react rapidly with components (b) and (c). As mentioned above, reactive siloxane compounds with reactive groups bonded to both ends of the siloxane structure are ideal from a reactivity point of view, but silane coupling agents with only one end or one end that is reactive and the other non-reactive can also be used.

[0027] In the bonding sheet for semiconductor device manufacturing of the present invention, the ratio of the reactive siloxane compound of the adhesive layer to the total number of epoxy groups in component (b) and maleic anhydride groups in component (c) is preferably 0.05 to 1.2, and more preferably 0.1 to 0.8. If it is less than the above range, the overall reactivity of the adhesive layer decreases, making it difficult to harden through processes such as crystal bonding and curing, resulting in sometimes excessively strong adhesion. On the other hand, if it exceeds the above range, excessive reaction occurs, which can easily lead to problems such as gelation during adhesive layer preparation, and the adhesion tends to weaken.

[0028] In addition to the necessary components (a) to (d), reaction promoters such as organic peroxides and triphenylphosphine can be added to the adhesive layer within a range that does not affect the adhesion of the adhesive layer. By adding these, it is also possible to control the state of the adhesive layer at room temperature in a good B stage. Furthermore, to control melt viscosity, improve thermal conductivity, and impart flame retardancy, fillers with an average particle size of less than 1 μm can be added to the adhesive layer. Examples of fillers include inorganic fillers such as silicon dioxide, alumina, magnesium oxide, aluminum nitride, boron nitride, titanium oxide, calcium carbonate, and aluminum hydroxide, as well as organic fillers such as polysiloxane resin and fluororesin. When using fillers, their content in the adhesive layer should ideally be 1-40% by mass.

[0029] The adhesive sheet of the present invention has the above-mentioned adhesive layer formed on one side of the heat-resistant film of the substrate. In manufacturing this type of adhesive sheet, an adhesive coating consisting of at least the following components is first prepared: the aforementioned carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the aforementioned structural formula (1) (b), a compound containing two or more maleic anhydride groups (c), a latent curing agent (d), and a solvent. Next, the coating is applied to one side of the heat-resistant film, such that the adhesive layer thickness after drying is preferably 1-50 μm, more preferably 3-20 μm, and then dried. Furthermore, to protect the adhesive layer, a peelable protective film is preferably provided on the formed adhesive layer. Alternatively, the coating can be applied to the protective film and dried to form the adhesive layer, and a heat-resistant film can be provided on top of it, thereby manufacturing the adhesive sheet. The protective film is peeled off when the adhesive sheet is used.

[0030] Heat-resistant films can be categorized as heat-resistant plastic films made of polyimide, polyphenylene sulfide, polyether ether, polyether ether ketone, liquid crystal polymers, polyethylene terephthalate, and polyethylene naphthalate, as well as composite heat-resistant films such as epoxy resin-glass cloth, with polyimide being particularly suitable. The thickness of the polyimide film is preferably 12.5~125μm, and more preferably 25~50μm. If it is less than the above range, the sheet tends to become less tough and difficult to handle. If it exceeds the above range, the adhesive application and peeling steps during QFN assembly tend to become difficult.

[0031] Regarding the solvents used in adhesive coatings, one or more of the following can be used: organic solvents such as hydrocarbons, alcohols, ketones, ethers (tetrahydrofuran, etc.) and water. The amount used only needs to be adjusted appropriately to achieve the suitable viscosity for the coating. In addition, the coating can be in the form of a solution, emulsion, or suspension, and the appropriate form can be selected according to the coating equipment and environmental conditions used.

[0032] Peel-off protective films include plastic films such as polyethylene, polypropylene, vinyl chloride, fluorinated resins and polysiloxane, as well as products made by coating polyethylene terephthalate, polyethylene naphthalate and paper with polysiloxane to impart peelability.

[0033] [Manufacturing Method of Semiconductor Devices] A method for manufacturing a semiconductor device using the bonding sheet of the present invention comprises the following steps: an attachment step, which involves attaching the bonding sheet to a lead frame or wiring substrate; a die bonding step, which involves mounting a semiconductor element on the lead frame or wiring substrate; a wire bonding step, which involves making the semiconductor element conductive with an external connection terminal; a sealing step, which involves sealing the semiconductor element with a sealing resin; and a peeling step, which involves peeling the bonding sheet from the lead frame or wiring substrate after the sealing step.

[0034] Hereinafter, with reference to Figures 1 and 2, an example of a method for manufacturing a semiconductor device using the bonding sheet of the present invention will be described. Figure 1 is a top view of a lead frame viewed from the side of a semiconductor element; Figures 2A to 2F are step diagrams showing a method for manufacturing a QFN package using the lead frame shown in Figure 1, and are cross-sectional views of the lead frame in Figure 1 along line A-A'.

[0035] First, prepare a lead frame 20 with the schematic structure shown in Figure 1. In the lead frame 20, a plurality of semiconductor element mounting portions (crystal base portions) 21 that mount semiconductor elements such as IC chips are formed in a matrix shape, and a plurality of leads 22 (external connection terminals) are formed along the outer periphery of each semiconductor element mounting portion 21. The material of the lead frame 20 can be conventional, such as copper plate and copper alloy plate, or materials with a base plating, and materials with nickel plating, palladium plating and gold plating layers sequentially applied to the surface of copper alloy plate.

[0036] As shown in Figure 2A, an adhesive sheet 10 is attached to one side (bottom) of the lead frame 20 by means of an adhesive layer (not shown) against the lead frame 20 (attachment step). Methods for attaching the adhesive sheet 10 to the lead frame 20 include lamination and pressure methods; from a production standpoint, the lamination method, which allows for continuous adhesive application, is preferable. The temperature of the adhesive sheet 10 in this step can range from room temperature (5~35℃) to 150℃, with 60~120℃ being more preferable. If the attachment is performed at a temperature higher than 150℃, the lead frame is prone to warping. If the lead frame 20 warps during this step, positioning of the die bonding and wire bonding steps will become difficult, making it hard to transport to the heating furnace, which may reduce the productivity of the QFN package.

[0037] As shown in Figure 2B, on the side of the semiconductor device mounting portion 21 of the lead frame 20 where the bonding sheet 10 is not attached, a semiconductor device 30, such as an IC chip, is mounted using a die-attach agent (not shown). At this time, warpage of the lead frame 20 is suppressed, making positioning easier. Next, the semiconductor device 30 is correctly placed in the predetermined position. Then, the die-attach agent is hardened by heating to approximately 100-200°C, fixing the semiconductor device 30 and mounting it on the semiconductor device mounting portion 21 (die-attach agent hardening treatment; the above is the die-attachment step). At this time, the adhesive layer of the bonding sheet 10 hardens and adheres to the lead frame.

[0038] If venting components generated from the bonding sheet 10 and die bonder adhere to the lead frame 20 and semiconductor device 30, poor wire bonding can easily occur during the wire bonding step, leading to a decrease in yield. Therefore, after the die bonder step and before the wire bonding step, a plasma treatment (plasma cleaning step) is performed on the lead frame 20 and semiconductor device 30. The plasma treatment can be performed as follows: in an argon atmosphere or a mixture of argon and hydrogen, the lead frame 20 (hereinafter sometimes referred to as a semi-finished product) with the bonding sheet 10 attached and the semiconductor device 30 mounted is irradiated with plasma. The plasma irradiation output power during the plasma treatment can be set to, for example, 150~600W. Furthermore, the plasma treatment time can be set to, for example, 0.1~15 minutes.

[0039] As shown in Figure 2C, the semiconductor element 30 is electrically connected to the leads 22 (external connection terminals) of the lead frame 20 using bonding wires 31 made of gold wire, copper wire, palladium-copper coated wire, etc. (wire bonding step). This step is performed while heating the semi-finished product to approximately 150-250°C on a heater block. The heating time for this step can be set to, for example, 5-60 minutes. During the wire bonding process, if the semi-finished product is heated, and the adhesive layer contains fluorine additives, the fluorine additives will transfer to the surface of the adhesive layer. Therefore, in the subsequent peeling process, the adhesive sheet 10 will become easier to peel off from the lead frame 20 and the sealing resin 40.

[0040] As shown in Figure 2D, the semi-finished product shown in Figure 2C is placed in a mold, and a sealing resin (mold material) is injected into and filled into the mold. After filling the mold with any amount, the interior of the mold is maintained under any pressure to seal the semiconductor element 30 with the sealing resin 40 (sealing step). The sealing resin can be a conventional material, such as a mixture of epoxy resin and inorganic filler. As shown in Figure 2E, the bonding sheet 10 is peeled off from the sealing resin 40 and the lead frame 20 to obtain a QFN unit 60 with a plurality of QFN packages 50 arranged thereon (peeling step).

[0041] As shown in Figure 2F, the QFN unit 60 is cut along the outer periphery of each QFN package 50 to obtain a plurality of QFN packages 50 (cutting step).

[0042] Furthermore, the above embodiment is described using a QFN package manufacturing method with a lead frame as an example, but the present invention is not limited thereto, and can also be applied to semiconductor device manufacturing methods other than QFN packages with lead frames and semiconductor device manufacturing methods using wiring substrates.

[0043] In the adhesive sheet of this invention, the adhesive layer is formed by crosslinking the carboxyl groups of a carboxyl-containing acrylonitrile-butadiene copolymer (a) with the glycidyl groups of epoxy resin (b) to present a B-stage state (semi-cured state), thereby achieving a low glass transition temperature (10°C to 50°C). The adhesive sheet with the low glass transition temperature adhesive layer can be continuously laminated under relatively low heating conditions, specifically at 60 to 150°C using a roll laminator or similar equipment, resulting in excellent productivity.

[0044] Furthermore, the adhesive layer in the bonding sheet of this invention, with a low glass transition temperature (-30°C to 50°C), exhibits a high modulus of elasticity upon heating. In recent years, products using low-cost copper or palladium-coated copper wire for bonding, replacing conventional gold wire, have become increasingly popular to reduce the cost of wire bonding. Copper or palladium-coated copper wire is a metal with higher elasticity than gold, and requires processing under higher loads than conventional gold wire to achieve stable shapes. If such a large load is applied to the leadframe, and the adhesive layer of the bonding sheet attached to the lower part of the leadframe has a low modulus of elasticity, the adhesive layer will deform, and resin sealing will occur while the adhesive layer is deformed. This will result in sealant leakage from the deformed adhesive layer. Furthermore, when the bonding sheet is peeled off from the leadframe, the adhesive layer will break from the deformed portion, leading to adhesive residue on the leadframe surface. Moreover, if the adhesive has a low modulus of elasticity during wire bonding, it will deform, making it difficult to transfer the wire load and easily causing poor wire bonding. In the bonding sheet of this invention, the adhesive layer has a high modulus of elasticity as described above. Therefore, even when using copper wire or palladium-coated copper wire for wire bonding, problems such as poor wire bonding, sealant leakage, and adhesive residue are less likely to occur.

[0045] Furthermore, in the adhesive sheet of the present invention, the adhesive layer has a compound (c) containing two or more maleic diamide groups. Therefore, during the drying process when manufacturing the adhesive sheet, the hardening of the adhesive layer can be appropriately controlled to make the adhesive layer into a high B stage state, thereby suppressing the increase of the bonding strength to the lead frame. As a result, it can suppress the leakage of sealing resin, the adhesive residue in the lead frame, and the breakage of the adhesive layer during peeling. Example

[0046] The following examples illustrate the invention in detail. [Examples 1-4 and Comparative Examples 1-3] (Composition of adhesive coating) According to the mass ratio shown in Table 1, components (a) to (d), other components, and tetrahydrofuran (THF) solvent are mixed to prepare the adhesive coating. Next, the adhesive was applied to one side of a 25μm thick polyimide film (manufactured by DU PONT-TORAY CO., LTD., trade name Kapton 100EN) with an adhesive layer thickness of 5μm after the coating was dried, and then dried in a hot air circulating oven set at 80°C to obtain an adhesive sheet. Additionally, details of the ingredients used are as follows.

[0047] • Acrylonitrile-butadiene copolymer containing carboxyl groups: Carboxyl equivalent of 1500 (calculated from number average molecular weight), acrylonitrile content of 27% by mass. • Epoxy resin with structural formula (1): molecular weight 630, functional group equivalent 210 g / eq Bisphenol A diphenyl ether dicis-butene diimidide: molecular weight 570, functional group equivalent 285 g / eq ·2-Phenylon-4,5-Dihydroxymethylimidazolium (manufactured by Shikoku Chemical Industry Co., Ltd., trade name: CUREZOL 2PHZ-PW, reaction start temperature: 150℃) ·2-Phenylacetyl-4-methyl-5-hydroxymethylimidazolium (manufactured by Shikoku Chemical Industry Co., Ltd., trade name: CUREZOL 2P4MHZ-PW, reaction start temperature: 130℃) ·2-Ethyl-4-methylimidazol (manufactured by Shikoku Chemical Industry Co., Ltd., trade name: CUREZOL 2E4MZ, reaction start temperature: 90℃) ·2-Undecylimidazole (manufactured by Shikoku Chemical Industry Co., Ltd., trade name: CUREZOL C11Z, reaction start temperature: 90℃)

[0048] [Table 1]

[0049] Subsequent measurements and evaluations were conducted on the adhesive sheets obtained in the above-described embodiments and comparative examples, and the results are shown in Table 2.

[0050] (1) Peel strength of Cu plate Attached object: Copper plate (Furukawa type 125μm 64) Next, the sheet dimensions are: 10mm width × 50mm length. Processing: Using a roll laminator, the resulting adhesive sheets obtained in each example were attached to the substrate to form the test specimen. The lamination conditions at this time were: temperature 80°C, pressure 4 N / cm, and lamination speed 0.5 m / min. Storage: The bonded sheets processed as described above are stored under the following two conditions, and the peel strength of each bonded sheet after storage is measured and evaluated. <Condition 1> The bonded sheet processed as described above was stored in a constant temperature bath set at 60°C for 120 hours. <Condition 2> After the above-processed adhesive sheet was stored in a constant temperature bath set at 60°C for 120 hours, it was further stored in a constant temperature bath set at 40°C for 1 week. Measurement: The 90° peel strength of the test specimen was measured using a universal tensile testing machine at room temperature. The copper plate was fixed, and the bonded sheet was stretched vertically for measurement. The stretching speed was set to 50 mm / min. Evaluation: Considering the mass production feasibility of layered adhesive bonding, a peel strength of 15 gf / cm or higher is practically considered a problem-free adhesive strength. Let 15 gf / cm or higher be designated A, and less than 15 gf / cm be designated X.

[0051] (2) Elastic modulus after heating Processing: On one side of a 38 μm thick polyethylene terephthalate (PET) film that has undergone demolding treatment, the aforementioned adhesive coatings are applied to a 5 μm thick adhesive layer after drying, and then dried to obtain an adhesive sheet. Next, a crystallization curing treatment is performed, and the adhesive sheet is heated at 175°C for 60 minutes in a ventilated oven. Measurement: After heating, the adhesive layer in the bonded sheet was peeled off from the PET film, and the tensile storage modulus was determined using a DMA (Dynamic Mechanical Analyzer). The DMA was performed using a VIBRON measuring instrument (manufactured by ORIENTEC CORPORATION, RHEOVIBRONDDV-II-EP) at a frequency of 11 Hz, a heating rate of 10 °C / min, and a load of 1.0 gf. Evaluation: The temperature applied during the wire bonding process is expected to be 200°C. Wires with a tensile storage modulus of elasticity of 6 MPa or higher are classified as A, and those with a tensile storage modulus of elasticity of less than 6 MPa at 200°C are classified as X.

[0052] (4) Peel strength of the test specimen after the resin sealing step, and presence or absence of adhesive residue after tape peeling. Processing and testing methods: (i) Preparation and heat treatment of the test specimen After cutting the adhesive sheet with an adhesive layer on the polyimide film obtained in each example into a width of 50mm × length of 60mm, the following (a)~(d) are carried out in sequence, anticipating the actual thermal process accompanying QFN assembly. (a) The adhesive sheets obtained in each example were cut to a width of 50 mm × a length of 60 mm, and then attached to a 57.5 mm × 53.5 mm copper alloy test lead frame (surface undercoating, 8 × 8 array arrangement, package size 5 mm × 5 mm, 32 pins) with dimensions of 50 mm × 100 mm, using a roll laminator. At this time, the lamination conditions were set as follows: temperature 80 °C, pressure 4 N / cm, and lamination speed 0.5 m / min. (b) Heat the copper alloy test lead frame with the adhesive sheet attached in a ventilated oven at 175°C for 60 minutes. This is the treatment to be performed for the intended crystal bonding and curing process. (c) Plasma irradiation treatment: Yield Engineering Systems, Inc. 1000P, Ar gas type, treatment 450W / 60 seconds. (d) 200℃ / 30 minutes heating: This process is performed for the intended wire bonding steps and is carried out using a hot plate. Next, on the exposed copper surface of the substrate that has undergone heat treatment (a) to (d), a sealing resin is deposited using a molding machine at 175°C for 3 minutes (resin sealing step). The sealing resin used is epoxy molding resin (EME-G631BQ) manufactured by Sumitomo Bakelite Co., Ltd.

[0053] (ii) Determination of peel strength and presence or absence of adhesive residue after tape peeling. For the test specimens after the above resin sealing step, the 90° peel strength was measured at room temperature using a universal tensile testing machine. Alternatively, the test specimen was fixed, and the corner portion of the bonded sheet was stretched vertically for measurement. The stretching speed was 300 mm / min. Furthermore, the presence of adhesive residue after tape peeling was confirmed using an optical microscope (KEYENCE CORPORATION VHX-500 digital microscope) at 100x magnification. evaluate: A: The peel strength is less than 1000gf / 50mm, the peeled sheet is not broken, and there is no adhesive residue on the surface of the lead frame and the sealing resin. B: The peel strength is above 1000gf / 50mm, the peeled sheet is not broken, and there is no adhesive residue on the surface of the lead frame and the sealing resin. X: The following conditions are observed: the adhesive sheet is broken or adhesive residue is observed on the surface of the lead frame material and the sealing resin, which meets at least one of the above conditions.

[0054] [Table 2]

[0055] As can be clearly seen from Table 2 above, the adhesive sheets of Examples 1 to 4 are practically sound in terms of peel strength against Cu plates, elastic modulus after heating, peel strength against test subjects after resin sealing, and the presence or absence of adhesive residue after tape peeling. In contrast, the adhesive sheets of Comparative Examples 1 and 2 have low adhesion strength to Cu plates and are prone to resin leakage. Furthermore, the adhesive sheet of Comparative Example 3 has a low modulus of elasticity after heating and is prone to poor wire bonding in copper wire bonding. Moreover, in the peel strength evaluation of the test specimen after the resin sealing step, it was firmly bonded to the copper alloy test lead frame, but the adhesive sheet cracked. Industrial availability

[0056] The bonding sheet for semiconductor device manufacturing of the present invention is suitable for use in QFN package assembly methods utilizing the QFN method. By using it in semiconductor device manufacturing methods, the bonding sheet can be easily peeled off during the peeling step of the QFN assembly process, and no adhesive residue will be generated on the bonding sheet, nor will the bonding sheet break.

[0057] 10: Adhesive sheets for semiconductor device manufacturing 20: Lead Frame 21: Crystal base 22: Lead wire 30: Semiconductor components 31: Joint line 40: Sealing resin 50: QFN package 60: QFN unit A-A': section line

Claims

1. An adhesive sheet for manufacturing semiconductor devices, which will be peelably attached to the lead frame or wiring substrate of a semiconductor device, characterized in that it comprises: a substrate; and a thermosetting adhesive layer disposed on one side of the substrate, and containing a carboxyl-containing acrylonitrile-butadiene copolymer (a), an epoxy resin having the following structural formula (1) (b), a compound containing two or more maleic anhydride groups (c), and a latent curing agent (d), wherein the latent curing agent (d) is an imidazole-based curing agent with a reaction start temperature of 100°C or higher with the epoxy resin; [Chemical Formula 1] wherein, The aforementioned carboxyl-containing acrylonitrile-butadiene copolymer (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 mass of the aforementioned carboxyl-containing acrylonitrile-butadiene copolymer (a), the aforementioned epoxy resin (b), the aforementioned compound containing two or more maleic diimide groups (c), and the aforementioned latent curing agent (d) total 30 to 300 parts by mass; and the mass ratio ((c) / (b)) of the aforementioned epoxy resin (b) to the aforementioned compound containing two or more maleic diimide groups (c) is 0.1 to 10.

2. A method for manufacturing a semiconductor device, characterized by comprising the following steps: an attachment step, wherein a bonding sheet for manufacturing a semiconductor device as claimed in claim 1 is attached to a lead frame or wiring substrate; a die bonding step, wherein a semiconductor element is mounted on the lead frame or wiring substrate; a wire bonding step, wherein the semiconductor element is made conductive to an external connection terminal; a sealing step, wherein the semiconductor element is sealed with a sealing resin; and a peeling step, wherein after the sealing step, the bonding sheet for manufacturing a semiconductor device is peeled off from the lead frame or wiring substrate.

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