Adhesive sheet, precursor of semiconductor device including adhesive sheet, semiconductor device produced using adhesive sheet, and method for producing semiconductor device using adhesive sheet

Abstract

The present invention addresses the problem of providing an adhesive sheet that tends not to allow resin bleeding when bonded to a material which can be of a wide variety, and that is easily peeled after high temperature treatment. The problem is solved by an adhesive sheet comprising a substrate layer with an adhesive layer laminated thereon, the adhesive sheet having a Martens hardness of at least 30 N / mm2 when heat-treated for 15 minutes at 260°C.

Description

Adhesive sheet, precursor of semiconductor device including same, semiconductor device manufactured using same, and method for manufacturing semiconductor device using same

[0001] The present invention relates to an adhesive sheet, a precursor of a semiconductor device containing the same, a semiconductor device manufactured using the same, and a method for manufacturing a semiconductor device using the same.

[0002] In recent years, as electronic devices such as portable personal computers and mobile phones have become smaller and more multifunctional, there has been a need for miniaturization and higher integration of the electronic components that make up the electronic devices, as well as for high-density mounting technology for electronic components. Against this background, surface-mounted semiconductor devices such as CSPs (chip scale packages), which enable high-density mounting, have been attracting attention, replacing peripheral-mounted semiconductor devices such as QFPs (quad flat packages) and SOPs (small outline packages). Among CSPs, QFN (quad flat non-leaded) and DFN (dual flat non-leaded) packages are particularly suitable because they can be manufactured using conventional semiconductor device manufacturing techniques, and are primarily used for low-terminal semiconductor devices with 100 pins or less.

[0003] A method for manufacturing a QFN package includes first attaching an adhesive sheet to one side of a lead frame (adhesion step), mounting a semiconductor element on a die pad formed on the other side of the lead frame (die attach step), electrically connecting the mounted semiconductor element to leads formed on the outer periphery of the die pad with bonding wires (wire bonding step), encapsulating the semiconductor element with encapsulating resin (encapsulation step), peeling off the adhesive sheet (peeling step), and cutting the resulting QFN unit (singulation step). A wire-bonded QFN package can be obtained by this manufacturing method.

[0004] Another method for manufacturing a QFN package (flip-chip QFN) involves first attaching an adhesive sheet to one side of a lead frame (adhesion process), then mounting a semiconductor element on the die pad and leads formed on the other side of the lead frame so that the bumps attach to the pre-printed solder (chip mounting process), then reflowing the solder to melt it (reflow process), cooling it to solidify it and electrically connecting the semiconductor element to the die pad and leads, encapsulating the semiconductor element with encapsulating resin (encapsulation process), peeling the adhesive sheet (peeling process), and cutting the resulting QFN unit (singulation process).This manufacturing method results in a reflow-type (flip-chip type) QFN package.

[0005] 2. Description of the Related Art Conventionally, adhesive sheets for use in the manufacture of semiconductor devices in the manufacturing process of QFN packages have been proposed, for example, as described in Patent Document 1.

[0006] Japanese Patent Application Laid-Open No. 2013-201404

[0007] Even if high temperature (e.g., about 260°C) processing is performed during the manufacturing process of the above-mentioned QFN or DFN package, it is preferable that the adhesive sheet is less likely to cause resin leakage (mold flash) during the sealing process and is releasable during the peeling process.

[0008] Furthermore, there is a demand for adhesive sheets that, when applied to various materials such as ceramic, metal, glass, etc., that adhere closely to the material and are unlikely to create gaps, making it difficult for resin to leak through the gaps, and that can be easily peeled off from the material after being treated at high temperatures, in addition to being used in the manufacture of QFN or DFN packages as described above.

[0009] The present invention aims to solve the above-mentioned problems. Specifically, it aims to provide an adhesive sheet that, when attached to various materials such as ceramic, metal, and glass, adheres closely to the material, making it difficult for gaps to form, thereby preventing resin leakage from the gaps, and that is easily peeled from the material after high-temperature processing. Another object of the present invention is to provide an adhesive sheet for manufacturing semiconductor devices that can be used in the manufacturing process of QFN or DFN packages, which is unlikely to cause resin leakage (mold flash) during the encapsulation process even when processed at high temperatures (e.g., approximately 260°C) during the manufacturing process, and which has releasability during the peeling process. Another object of the present invention is to provide a precursor for a semiconductor device containing the adhesive sheet, a semiconductor device manufactured using the adhesive sheet, and a method for manufacturing a semiconductor device using the adhesive sheet.

[0010] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention comprises the following (1) to (10): (1) a substrate layer and an adhesive layer are laminated together, and when heat-treated at 260°C for 15 minutes, the Martens hardness of the adhesive layer is 30 N / mm 2An adhesive sheet as described above. (2) The adhesive sheet as described above in (1), characterized in that the ratio of the Mastens hardness of the adhesive layer after heat treatment at 260°C for 15 minutes to the Martens hardness of the adhesive layer before heat treatment (Mastens hardness after heat treatment at 260°C / Martens hardness before heat treatment) is 25 to 70. (3) The adhesive sheet as described above in (1) or (2), which is releasably attached to a lead frame or wiring substrate of a semiconductor device and used in the manufacturing process of the semiconductor device. (4) The adhesive sheet as described above in any one of (1) to (3), wherein the adhesive layer contains a phenolic antioxidant. (5) The adhesive sheet as described above in any one of (1) to (4), wherein the adhesive layer does not contain a fluororesin. (6) The adhesive sheet as described above in any one of (1) to (5), wherein the adhesive layer does not contain a silicone resin. (7) The adhesive sheet according to any one of (1) to (6) above, wherein the adhesive layer contains 75% by mass or more of unhydrogenated styrene-butadiene-styrene copolymer (SBS). (8) A precursor to a semiconductor device, wherein a semiconductor element is mounted on one main surface of a lead frame or the wiring board of the semiconductor device, the semiconductor element is encapsulated with an encapsulating resin, and the adhesive sheet according to any one of (1) to (7) above is releasably attached to the other main surface of the lead frame or the wiring board of the semiconductor device. (9) A semiconductor device manufactured using the adhesive sheet according to any one of (1) to (7) above. (10) A method for manufacturing a semiconductor device, using the adhesive sheet according to any one of (1) to (7) above.

[0011] According to the present invention, an adhesive sheet can be provided that, when attached to various materials such as ceramic, metal, and glass, adheres closely to the material, making it difficult for gaps to form, thereby preventing resin leakage through the gaps, and that can be easily peeled off from the material after high-temperature treatment. Such an adhesive sheet is an adhesive sheet for manufacturing semiconductor devices that can be used in the manufacturing process of QFN or DFN packages, and is preferably used as an adhesive sheet that is difficult to cause resin leakage (mold flash) during the encapsulation process even when treated at high temperatures (e.g., about 260°C) during the manufacturing process, and that has releasability during the peeling process. Also provided are a precursor for a semiconductor device containing the adhesive sheet, a semiconductor device manufactured using the adhesive sheet, and a method for manufacturing a semiconductor device using the adhesive sheet.

[0012] 2(a) is a schematic cross-sectional view of an adhesive sheet of the present invention cut in a direction perpendicular to its main surface. FIG. 2(b) is a schematic view showing a lead frame that can be included in the precursor of the present invention and the semiconductor device of the present invention, where FIG. 2(a) is a diagram (schematic view) showing the main surface as seen from the side on which a semiconductor element is mounted, and FIG. 2(b) is a cross-sectional view taken along line A-A' in FIG. 2(a). FIG. 2(b) is a diagram for explaining a manufacturing method of the present invention, which is a schematic cross-sectional view of an adhesive sheet or the like of the present invention cut in a direction perpendicular to its main surface. FIG. 2(b) is a diagram for explaining another ... for explaining a step subsequent to the step shown in FIG.

[0013] The present invention is described below. The present invention is a laminate of a substrate layer and an adhesive layer, and when heat-treated at 260°C for 15 minutes, the Martens hardness of the adhesive layer is 30 N / mm 2 The adhesive sheet is as described above. Such an adhesive sheet will be referred to hereinafter as the "adhesive sheet of the present invention." The adhesive sheet of the present invention may be in a state before being subjected to a heat treatment at 260°C for about 15 minutes. In this case, the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes, and the Martens hardness of the adhesive layer is 30 N / mm 2If the adhesive sheet has the above properties, it corresponds to the adhesive sheet of the present invention. The adhesive sheet of the present invention may also be in a state after being subjected to a heat treatment. Even in this case, when further heat treatment is performed at 260°C for 15 minutes, the Martens hardness of the adhesive layer is 30 N / mm 2 If the above conditions are met, the adhesive sheet falls within the scope of the present invention.

[0014] The adhesive sheet of the present invention adheres closely to various members such as ceramic, metal, and glass, making it difficult for gaps to form when applied to the member, thereby making it difficult for resin to leak through the gaps, and it is also possible to provide an adhesive sheet that is easily peeled from the member after treatment at high temperatures. Furthermore, the adhesive sheet of the present invention is preferably used in the manufacturing process of a semiconductor device by being peelably attached to the lead frame or wiring substrate of a semiconductor device.

[0015] The present invention also relates to a precursor of a semiconductor device, in which a semiconductor element is mounted on one main surface of a lead frame or wiring board of the semiconductor device, the semiconductor element is encapsulated with an encapsulating resin, and the adhesive sheet of the present invention is releasably attached to the other main surface of the lead frame or wiring board of the semiconductor device. Such a precursor of a semiconductor device will hereinafter also be referred to as the "precursor of the present invention."

[0016] The present invention also relates to a semiconductor device manufactured using the adhesive sheet of the present invention. Such a semiconductor device will hereinafter also be referred to as the "semiconductor device of the present invention."

[0017] Furthermore, the present invention relates to a method for manufacturing a semiconductor device using the adhesive sheet of the present invention. Such a manufacturing method is also referred to as the "manufacturing method of the present invention" below.

[0018] The adhesive sheet of the present invention will now be described. The adhesive sheet of the present invention comprises a substrate layer and an adhesive layer, which are laminated together.

[0019] The base layer is required to have heat resistance. For example, when manufacturing a semiconductor device in a QFN or DFN package using an adhesive sheet, the adhesive sheet is exposed to high temperatures of about 150 to 250°C in the chip mounting process (or die attach process), wire bonding process, and sealing process. Also, for example, in the reflow process, the adhesive sheet is exposed to high temperatures of about 260°C.

[0020] A heat-resistant film can be used as the substrate layer. The heat-resistant film preferably has a glass transition temperature of 150°C or higher, more preferably 180°C or higher. The heat-resistant film also preferably has a thermal expansion coefficient of 5 to 50 ppm / °C at 150 to 250°C, more preferably 10 to 30 ppm / °C. When a heat-resistant film is used as the substrate layer, the thermal expansion coefficient of the heat-resistant film increases rapidly above the glass transition temperature (Tg), resulting in a large difference in thermal expansion with, for example, a metal lead frame. In this case, warping may occur in the heat-resistant film and the lead frame when the temperature is returned to room temperature. Furthermore, if warping occurs in the heat-resistant film and the lead frame, for example, the lead frame may not be able to be attached to the positioning pins of the mold during the sealing process, resulting in misalignment.

[0021] Examples of heat-resistant films include films made of polyimide, polyamide, polyethersulfone, polyphenylene sulfide, polyetherketone, polyetheretherketone, triacetylcellulose, polyetherimide, and the like.

[0022] A metal foil can be used as the substrate layer. The metal foil preferably has a thermal expansion coefficient of 5 to 50 ppm / °C at 150 to 250°C, more preferably 10 to 30 ppm / °C. The reason for this is the same as in the case of the heat-resistant film described above.

[0023] Examples of metal foils include foils made of gold, silver, copper, platinum, aluminum, magnesium, titanium, chromium, manganese, iron, cobalt, nickel, zinc, palladium, indium, and tin, alloy foils containing these metals as the main component, and plated foils of these metals.

[0024] The thickness of the substrate layer is determined in consideration of the material, etc. The thickness of the substrate layer is not particularly limited, and may be, for example, 10 to 100 μm, or 15 to 40 μm.

[0025] The adhesive layer has a Martens hardness of 30 N / mm when the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes. 2 or more, 30 to 400 N / mm 2 It is preferable that the strength is 50 to 400 N / mm 2 It has been found that when the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes, an adhesive layer having a Martens hardness in this range is less likely to cause resin leakage (mold flash) in the sealing step, even when treated at high temperatures (e.g., about 260°C) in the manufacturing process of a QFN or DFN package, and also has releasability in the peeling step.

[0026] The Martens hardness of the adhesive layer is measured in the form of an adhesive sheet, and includes the influence of the substrate. The Martens hardness is thought to be determined by a combination of the materials of the adhesive layer and substrate, the presence or absence and amount of hydrogenation, the diblock content, the type and amount of added components, etc. When the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes, the Martens hardness of the adhesive layer is 30 N / mm 2 To achieve the above, the material of the adhesive layer and whether or not hydrogen is added have a large effect, so an appropriate material must be selected.

[0027] The Martens hardness of the adhesive layer before or after heating refers to a value obtained by measurement using a method in accordance with ISO 14577-1. Details of the measurement method will be described later in the section on examples.

[0028] The ratio of the Martens hardness of the adhesive layer after heat treatment at 260°C for 15 minutes to the Martens hardness of the adhesive layer before heat treatment (Mattens hardness after heat treatment at 260°C / Martens hardness before heat treatment) is preferably 25 to 70.

[0029] The adhesive layer contains a resin as a main component. The resin constituting the adhesive layer may be any resin capable of achieving a Martens hardness within the above range when the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes. Examples of resins that may be capable of achieving a Martens hardness within the above range when the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes include unhydrogenated styrene-butadiene-styrene copolymers and polyetheramideimides. The adhesive layer preferably contains 75% by mass or more of unhydrogenated styrene-butadiene-styrene copolymers (SBS) or polyetheramideimides, more preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. In this case, when the adhesive sheet of the present invention is heat-treated at 260°C for 15 minutes, the adhesive layer has a Martens hardness of 30 N / mm 2 It may be more than that.

[0030] The adhesive layer preferably does not contain a fluororesin. In this case, when the adhesive sheet of the present invention is heat-treated at 260° C. for 15 minutes, the adhesive layer has a Martens hardness of 30 N / mm 2 Because it tends to be more than that.

[0031] The adhesive layer preferably does not contain a silicone resin. In this case, when the adhesive sheet of the present invention is heat-treated at 260° C. for 15 minutes, the adhesive layer has a Martens hardness of 30 N / mm 2 Because it tends to be more than that.

[0032] The adhesive layer contains a resin as a main component and may further contain additives. Examples of additives include curing aids, catalysts, curing agents, antioxidants, and silane coupling agents. The content of the additives in the adhesive layer is preferably 25% by mass or less, more preferably 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0033] The adhesive layer preferably contains a phenolic antioxidant, and the content of the phenolic antioxidant in the adhesive layer is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0034] The thickness of the adhesive layer is not particularly limited, and may be, for example, 2 to 20 μm, or 2 to 8 μm.

[0035] The adhesive layer can be produced by, for example, a casting method in which raw materials constituting each component of the adhesive layer are dissolved and / or dispersed in a known solvent (aromatic, ketone, or aprotic polar organic solvent, tetrahydrofuran, etc.), and the resulting solution is applied to the surface of the base layer and dried to form the adhesive layer. Alternatively, a lamination method can be used in which the above-mentioned solution is once applied to a release film, dried, and then transferred onto the base layer.

[0036] The adhesive sheet of the present invention may be in a long shape, and may be wound around a core to form a reel.

[0037] The adhesive sheet of the present invention includes a substrate layer and an adhesive layer, which are laminated together, but may also have another layer laminated thereon. For example, the substrate layer, adhesive layer, and protective layer may be laminated in this order. That is, a protective layer may be attached to the surface of the adhesive layer that is not in contact with the substrate layer. Adhesive layers may also be laminated on the front and back surfaces of the substrate layer, and the laminate may be laminated in this order: protective layer, adhesive layer, substrate layer, adhesive layer, and protective layer. The protective layer may be, for example, a film. The protective layer may also be peelable from the adhesive layer, and may be peeled off immediately before attachment to, for example, a lead frame or wiring board. In this case, damage to the adhesive layer is prevented between the production and use of the adhesive sheet of the present invention. The protective layer may be any layer that has releasability, such as a film of polyester, polyethylene, polypropylene, polyethylene terephthalate, etc., or a film whose surface has been treated with a silicone resin or a fluorine compound for release.

[0038] Next, the adhesive sheet of the present invention, the precursor of the present invention, the semiconductor device of the present invention, and the manufacturing method of the present invention will be described using the drawings. The embodiments shown in the following drawings are diagrams (schematic diagrams) showing examples of the adhesive sheet of the present invention, the precursor of the present invention, the semiconductor device of the present invention, and the manufacturing method of the present invention. The adhesive sheet of the present invention, the precursor of the present invention, the semiconductor device of the present invention, and the manufacturing method of the present invention are not limited to the embodiments shown in the drawings.

[0039] 1 is a schematic cross-sectional view of an adhesive sheet of the present invention cut in a direction perpendicular to the main surface thereof. As shown in Fig. 1, an adhesive sheet 10 of the present invention has a base layer 3 and an adhesive layer 1, which are laminated together.

[0040] FIG. 2 is a schematic diagram showing a lead frame 20 that can be included in the precursor of the present invention and the semiconductor device of the present invention. FIG. 2(a) is a diagram (schematic diagram) showing the main surface as seen from the side on which a semiconductor element is mounted, and FIG. 2(b) is a cross-sectional view taken along line A-A' in FIG. 2(a). As described with reference to FIG. 2 and FIGS. 3, 4, and 5 (described later), the adhesive sheet 10 of the present invention can be used in the manufacturing process of a semiconductor device. Specifically, during the manufacturing process, it is releasably attached to the lead frame or wiring board of the semiconductor device. The lead frame 20 is a metal plate on which a conductor pattern is formed by etching, pressing, or the like. The lead frame 20 of the embodiment shown in FIG. 2 has a matrix of multiple die pad portions 21 on which semiconductor elements such as IC chips are mounted, and numerous lead portions 22 formed along the periphery of each die pad portion 21. Materials for the lead frame 20 include conventionally known materials, such as a copper plate having a nickel-plated layer, a palladium-plated layer, and a gold-plated layer formed in that order on the surface of the copper plate.

[0041] The precursor and the semiconductor device of the present invention may include a wiring board instead of the lead frame. The wiring board is an electrically insulating substrate having a conductor pattern made of a conductive material formed on at least the surface thereof.

[0042] Next, the manufacturing method of the present invention will be described with reference to Figure 3. The manufacturing method of the present invention preferably includes the following steps: bonding step, die attach step, wire bonding step, encapsulation step, peeling step, and singulation step. By this manufacturing method of the present invention, a wire-bonded QFN or DFN package can be obtained. Figure 3 shows an example of obtaining a QFN package, but a DFN package can also be obtained in the same way.

[0043] As shown in FIG. 3( a), the manufacturing method of the present invention preferably first performs an attachment step in which the adhesive sheet 10 of the present invention shown in FIG. 1 is attached to one main surface of the lead frame 20 shown in FIG. 2( b). The adhesive sheet 10 of the present invention is attached so that the adhesive layer 1 is in close contact with the main surface of the lead frame 20. The method for attaching the adhesive sheet 10 of the present invention to the lead frame 20 is not particularly limited, but a lamination method is preferred. The temperature when attaching the adhesive sheet 10 of the present invention to the lead frame 20 may be room temperature (5 to 35°C). In other words, even when the adhesive sheet 10 of the present invention is attached to the lead frame 20 at room temperature, warping of the lead frame 20 can be suppressed. This results in high productivity. When attaching the adhesive sheet 10 of the present invention to the lead frame 20, the adhesive sheet 10 of the present invention may be heated to 50 to 260°C.

[0044] Following the bonding step, the manufacturing method of the present invention preferably performs a die-attach step in which a semiconductor element 30 is mounted on a die pad portion 21 formed on the other main surface of the lead frame 20. As shown in FIG. 3(b), the semiconductor element 30 is mounted via a die-attach adhesive (not shown) on the side of the die pad portion 21 of the lead frame 20 to which the adhesive sheet 10 of the present invention is not attached. At this time, it is preferable that warping of the lead frame 20 is suppressed, as this facilitates positioning. In this case, the semiconductor element 30 is accurately mounted in a predetermined position. The lead frame 20 is then heated to approximately 100 to 200°C to harden the die-attach adhesive, and the semiconductor element 30 is fixed and mounted on the die pad portion 21.

[0045] Although a wire bonding process may be performed following the die attachment process, it is preferable to perform a plasma cleaning process beforehand. During the manufacturing process, outgassing components may be generated from the adhesive sheet 10 of the present invention, the die attachment adhesive, etc. If outgassing components are generated and adhere to the lead frame 20 or the semiconductor element 30, this may result in poor wire bonding and reduced yield during the wire bonding process. The plasma cleaning process may be, for example, a process in which the lead frame 20, to which the adhesive sheet 10 of the present invention has been attached and to which the semiconductor element 30 has been mounted, is plasma-treated 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 preferably, for example, 150 to 600 W. Furthermore, the plasma treatment time is preferably, for example, 0.01 to 5 minutes.

[0046] In the manufacturing method of the present invention, following the die attach step or the plasma cleaning step, it is preferable to carry out a wire bonding step in which the mounted semiconductor element 30 is electrically connected by a bonding wire to the lead portions 22 formed on the outer periphery of the die pad portion 21. As shown in Figure 3(c), the wire bonding step is a step in which the semiconductor element 30 is electrically connected to the lead portions 22 of the lead frame 20 by a bonding wire 31 such as a gold wire. This step is preferably carried out for 5 to 30 minutes while the lead frame 20, on which the adhesive sheet 10 of the present invention is attached and on which the semiconductor element 30 is mounted, as shown in Figure 3(b), is heated on a heater block to about 150 to 250°C.

[0047] Following the wire bonding step, the manufacturing method of the present invention preferably includes an encapsulation step in which the semiconductor element 30 is encapsulated with an encapsulating resin. As shown in FIG. 3(d), the lead frame 20, to which the adhesive sheet 10 of the present invention is attached, the semiconductor element 30 is mounted, and wire-bonded, as shown in FIG. 3(c), is placed in a mold, and an encapsulating resin (mold material) is injected and filled into the mold. For example, the mold is heated to 100-200°C and a pressure of 5-10 GPa is applied to fill and seal the resin. During this injection, the adhesive sheet 10 of the present invention is difficult to peel from the lead frame 20, thereby suppressing mold flash. After filling the mold with a predetermined amount of encapsulating resin 40, the semiconductor element 30 can be encapsulated with the encapsulating resin 40 by maintaining the mold at a predetermined pressure. The encapsulating resin is not particularly limited, and conventionally known resins can be used. For example, a mixture of epoxy resin and inorganic filler can be used as the encapsulating resin.

[0048] The embodiment shown in FIG. 3(d) corresponds to the precursor of the present invention.

[0049] In the manufacturing method of the present invention, a peeling step is preferably carried out following the encapsulation step, in which the adhesive sheet is peeled off. As shown in Figure 3(e), by peeling the adhesive sheet 10 of the present invention from the encapsulation resin 40 and the lead frame 20, a QFN unit 60 in which a plurality of QFN packages 50 are arranged can be obtained. At this time, the adhesive sheet 10 of the present invention can be peeled off from the lead frame 20 and the encapsulation resin 40 with almost no adhesive residue remaining.

[0050] The temperature (peeling temperature) at which the adhesive sheet 10 of the present invention is peeled from the lead frame 20 and the sealing resin 40 may be between 0 and 250° C., or may be between 20 and 220° C. From the viewpoint of productivity, it is desirable that the sheet be peelable at room temperature.

[0051] After the peeling step, a step of removing the adhesive layer (residual glue) remaining on the surfaces of the lead frame 20 and the sealing resin 40 may be performed. Specific examples include a method of removing the adhesive by mechanical brushing or a method of removing the adhesive by using a solvent (N-methyl-2-pyrrolidone, dimethylacetamide, etc.). However, in the manufacturing method of the present invention, residual glue is unlikely to occur, and therefore such a step is often not necessary.

[0052] In the manufacturing method of the present invention, following the peeling step, a singulation step is preferably performed to cut the QFN units 60. As shown in FIG. 3( f), the QFN units 60 are cut along the periphery of each QFN package 50 to obtain a plurality of QFN packages 50.

[0053] The embodiment shown in FIG. 3(f) corresponds to the semiconductor device of the present invention.

[0054] Next, another manufacturing method of the present invention will be described with reference to Figures 4 and 5. The manufacturing method of the present invention preferably includes the following steps: bonding step, solder printing step, chip mounting step, reflow step, flux cleaning step, sealing step, peeling step, and singulation step. A reflow-type QFN or DFN package can be obtained by this manufacturing method. Figures 4 and 5 show an example of obtaining a QFN package, but a DFN package can also be obtained in the same way.

[0055] When a QFN package is obtained by the reflow method, adhesive sheet 10 of the present invention is exposed to a high temperature of about 260° C. Even when exposed to a high temperature of about 260° C., adhesive sheet 10 of the present invention is unlikely to cause resin leakage (mold flash) during the sealing process, and is releasable during the peeling process. Furthermore, in the attachment process, the adhesive sheet of the present invention may be able to be attached to a lead frame at room temperature.

[0056] As shown in FIG. 4( a), the manufacturing method of the present invention preferably first performs an attachment step in which the adhesive sheet 10 of the present invention shown in FIG. 1 is attached to one main surface of the lead frame 20 shown in FIG. 2( b). The adhesive sheet 10 of the present invention is attached so that the adhesive layer 1 is in close contact with the main surface of the lead frame 20. The method for attaching the adhesive sheet 10 of the present invention to the lead frame 20 is not particularly limited, but a lamination method is preferred. The adhesive sheet 10 of the present invention may be attached to the lead frame 20 at room temperature (5 to 35°C). In other words, even when the adhesive sheet 10 of the present invention is attached to the lead frame 20 at room temperature, warping of the lead frame 20 can be suppressed. This results in high productivity. When attaching the adhesive sheet 10 of the present invention to the lead frame 20, the adhesive sheet 10 of the present invention may be heated to 50 to 260°C.

[0057] Following the bonding step, in the manufacturing method of the present invention, a solder printing step is preferably performed in which solder 25 is printed on the die pad portion 21 and lead portions 22 formed on the other main surface of the lead frame 20. The solder is preferably lead-free solder. As shown in FIG. 4(b), the solder 25 is printed on the side of the die pad portion 21 and lead portions 22 to which the adhesive sheet 10 of the present invention is not attached. The method for printing the solder is not particularly limited and may be, for example, a conventionally known method. Specifically, printing can be performed using, for example, a metal mask.

[0058] Following the solder printing step, the manufacturing method of the present invention preferably performs a chip mounting step in which a semiconductor element 35 is mounted on the die pad portion 21 formed on the other main surface of the lead frame 20. Here, as shown in FIG. 4( c), the semiconductor element 35 has bumps 37 extending from one main surface. The bumps 37 may be, for example, Cu pillars. The semiconductor element 35 is then mounted on the die pad portion 21 and lead portions 22 of the lead frame 20 so that the bumps 37 attach to the solder 25 previously printed thereon.

[0059] In the manufacturing method of the present invention, following the chip mounting step, a reflow step is preferably performed to melt the solder 25. As shown in FIG. 4(d), the solder 25 is melted by reflow and then solidified by cooling or allowing it to cool, physically fixing and electrically connecting the semiconductor element 35 to the die pad portion 21 and the lead portion 22 via the bumps 37. The reflow method is not particularly limited and may be, for example, a conventionally known method. Specifically, reflow can be performed using, for example, a commercially available hot air circulation reflow oven. In this case, the maximum temperature when lead-free solder is used for bonding can reach approximately 260°C.

[0060] The reflow process may be followed by a sealing process, but a defluxing process may be performed before that. The method for defluxing is not particularly limited, and may be, for example, a conventionally known method. Specifically, defluxing can be performed using commercially available devices such as spray cleaning, submerged jet cleaning, and ultrasonic cleaning.

[0061] In the manufacturing method of the present invention, following the reflow process or the flux cleaning process, it is preferable to perform an encapsulation process in which the semiconductor element 35 is encapsulated with encapsulating resin 40. As shown in FIG. 5(a), the lead frame 20 with the adhesive sheet 10 of the present invention attached and the semiconductor element 35 mounted thereon, as shown in FIG. 4(d), is placed in a mold, and the encapsulating resin (mold material) is injected into the mold to fill it. For example, the mold is heated to 100-200°C and a pressure of 5-10 GPa is applied to inject and encapsulate the resin. During this injection, the adhesive sheet 10 of the present invention is difficult to peel from the lead frame 20, thereby suppressing mold flash. After filling the mold with a predetermined amount of encapsulating resin 40, the semiconductor element 35 can be encapsulated with the encapsulating resin 40 by maintaining the mold at a predetermined pressure. The encapsulating resin is not particularly limited, and conventionally known resins can be used. For example, a mixture of epoxy resin and inorganic filler can be used as the encapsulating resin.

[0062] The embodiment shown in FIG. 5(a) corresponds to the precursor of the present invention.

[0063] In the manufacturing method of the present invention, a peeling step is preferably carried out following the encapsulation step, in which the adhesive sheet is peeled off. As shown in Figure 5(b), by peeling the adhesive sheet 10 of the present invention from the encapsulation resin 40 and the lead frame 20, a QFN unit 60 in which a plurality of QFN packages 50 are arranged can be obtained. At this time, the adhesive sheet 10 of the present invention can be peeled off from the lead frame 20 and the encapsulation resin 40 with almost no adhesive residue remaining.

[0064] The temperature (peeling temperature) when peeling the adhesive sheet 10 of the present invention from the lead frame 20 and the sealing resin 40 may be between 0 and 250°C, or may be between 20 and 220°C.

[0065] After the peeling step, a step of removing the adhesive layer (residual glue) remaining on the surfaces of the lead frame 20 and the sealing resin 40 may be performed. Specific examples include a method of removing the adhesive by mechanical brushing or a method of removing the adhesive by using a solvent (N-methyl-2-pyrrolidone, dimethylacetamide, etc.). However, in the manufacturing method of the present invention, residual glue is unlikely to occur, and therefore such a step is often not necessary.

[0066] In the manufacturing method of the present invention, following the peeling step, a singulation step is preferably performed to cut the QFN units 60. As shown in FIG. 5C, the QFN units 60 are cut along the periphery of each QFN package 50 to obtain a plurality of QFN packages 50.

[0067] The embodiment shown in FIG. 5C corresponds to the semiconductor device of the present invention.

[0068] The present invention will be described below using examples, but the present invention is not limited to these examples.

[0069] The types and amounts (parts by mass) of raw materials used in each example and comparative example are shown in Table 1. The details of each raw material in Table 1 are as follows. SBS (1): styrene-butadiene-styrene copolymer, styrene-butadiene weight ratio 18 / 82, diblock content 60% SBS (2): styrene-butadiene-styrene copolymer, styrene-butadiene weight ratio 23 / 77, diblock content 16% SEBS (1): styrene-ethylenebutylene-styrene copolymer, styrene-ethylenebutylene weight ratio 30 / 70 SEBS (2): maleic anhydride-modified styrene-ethylenebutylene-styrene copolymer, styrene-ethylenebutylene weight ratio 20 / 80, acid value 10 mg CH3ONa / g Silicon: addition type silicone adhesive SD-4587L (Dow Toray Industries, Inc.) Acrylic: carboxy group-containing acrylic acid ester copolymer resin SG-280TEA (Nagase ChemteX Corporation) Curing aid (1): bismaleimide BMI-80 (K.I. Chemical Co., Ltd.) Curing aid (2): Oligophenylene ether OPE-2st (Mitsubishi Gas Chemical Company, Inc.) Curing aid (3): Iron(III) acetylacetonate (Tokyo Chemical Industry Co., Ltd.) Catalyst: Platinum catalyst SRX212 (Dow Toray Industries, Inc.) Curing agent: Epoxy curing agent TETRAD-X (Mitsubishi Gas Chemical Company, Inc.) Antioxidant: Phenolic antioxidant IRGANOX1010 (BASF Japan Ltd.)

[0070] In each example and comparative example, an adhesive coating solution was prepared by dissolving and dispersing each raw material in an appropriate amount of THF (tetrahydrofuran) at the mass ratio shown in Table 1. Next, a polyimide resin film (manufactured by DuPont-Toray Co., Ltd., product name: Kapton 100EN, thickness 25 μm, glass transition temperature 300°C or higher, thermal expansion coefficient 15 ppm / °C) was prepared as a substrate layer. The adhesive coating solution was then applied to the surface of this substrate layer so that the thickness after drying was 5 μm. After application of the adhesive coating solution, the substrate was dried at 200°C for 3 minutes to form an adhesive layer on the surface of the substrate layer, thereby obtaining an adhesive sheet in each example and comparative example. The obtained adhesive sheet was measured for Martens hardness, resin leakage number, and post-molding peel strength before and after heat treatment at 260°C / 15 minutes using the methods described below.

[0071] The method for measuring Martens hardness before and after heat treatment will be described. First, the adhesive sheet was subjected to heat treatment by holding it in a hot air circulating oven set at 260°C for 15 minutes. Next, each adhesive sheet before and after heat treatment was cut into approximately 2 cm squares, and an instant adhesive was applied to the main surface of the base layer of the adhesive sheet, and the sheet was attached to a glass plate with a thickness of approximately 1 mm. The glass substrate with each adhesive sheet attached was then left in an atmosphere of 23°C and 50% RH for 24 hours. Next, the Martens hardness was measured using the main surface of the adhesive layer of each adhesive sheet as the measurement surface. Martens hardness was measured using an Elionix ENT-NEXUS nanoindenter according to a method compliant with ISO 14577-1 under the following measurement conditions. Measurements were performed at 20 different locations on the surface of the adhesive layer. The 20 Martens hardness data obtained were then arranged in descending order, and the five largest and five smallest data were excluded to obtain the average value of the remaining 10 data.

[0072] The Martens hardness measurement conditions were as follows: Measurement mode: Load / unload test Indenter: Berkovich high load unit Measurement temperature: 30°C Load end load: 0.5 mN Maximum load hold: 5000 msec The Martens hardness measurement results are shown in Table 1. Table 1 also shows the ratio of the Martens hardness of the adhesive layer after heat treatment at 260°C to the Martens hardness of the adhesive layer before heat treatment (Mastens hardness after heat treatment at 260°C / Martens hardness before heat treatment).

[0073] The method for measuring the number of resin leaks will be described. First, the adhesive sheets obtained in the examples and comparative examples were cut into 50 mm wide strips. A QFN etching lead frame (CDA194-Cu lead frame, 4 blocks x 64 pieces (total 256 pieces) matrix arrangement, package size 5.0 mm x 5.0 mm, 32 pins) with external dimensions of 200 mm x 60 mm x 0.2 mm thick was also prepared. The cut strip-shaped adhesive sheet was then attached to the QFN etching lead frame by lamination so that the adhesive layer was attached. The resulting product (QFN etching lead frame with adhesive sheet attached) was called a laminate. Note that the adhesive layer of the strip-cut adhesive sheet was prevented from overlapping the guide hole. Lead-free cream solder was printed on the connection portion of the lead frame using a metal mask, and a dummy chip was temporarily fixed.

[0074] Next, the laminates of each example and comparative example were subjected to a 15-minute heat treatment at 260°C. This heat treatment corresponds to three lead-free solder reflows. Next, to simulate a flux cleaning process, the heat-treated laminates were cleaned, rinsed, and dried using Arakawa Chemical's ST-100SX flux cleaner under manufacturer-recommended conditions. Next, the laminates were resin-encapsulated using transfer molding (mold molding) with an epoxy-based molding compound (Sumitomo Bakelite EME-G631BQ) at a heating temperature of 180°C, a pressure of 10 MPa, and a processing time of 3 minutes to obtain precursors. The appearance of 256 semiconductor devices contained in the resulting precursors was then inspected, and the number of semiconductor devices with encapsulating resin attached to the external connection portion of the leads (the surface of the leads facing the adhesive sheet) was counted. Excluding those with encapsulating resin attached to the external connection portion of the leads due to external foreign matter, the remaining devices were determined to have resin leakage. The results are shown in Table 1.

[0075] Next, the method for measuring the post-molding peel strength will be described. Using a tensile tester, the adhesive sheet was peeled from the lead frame of the precursor. The average peel strength was then calculated. This measurement was performed under conditions of room temperature and humidity, 90-degree peeling, and a peel speed of 50 mm / min. The results are shown in Table 1.

[0076] Next, the resin leakage count was measured by the same procedure except that the "heat treatment at 260°C for 15 minutes" in the measurement of the resin leakage count was changed to "heat treatment at 260°C for 30 minutes." The resulting precursor was also measured for post-molding peel strength using the same measurement method as above. The results are shown in Table 1.

[0077]

[0078] This application claims priority based on Japanese Patent Application No. 2024-107710, filed July 3, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0079] REFERENCE SIGNS LIST 1 adhesive layer 3 substrate layer 10 adhesive sheet of the present invention 20 lead frame 21 die pad portion 22 lead portion 25 solder 30 semiconductor element 35 semiconductor element 31 bonding wire 37 bump 40 sealing resin 50 QFN package 60 QFN unit

Claims

A base material layer and an adhesive layer are laminated together, When heat-treated at 260°C for 15 minutes, the adhesive layer has a Martens hardness of 30 N / mm 2 That's all. Adhesive sheet.

2. The adhesive sheet according to claim 1, wherein the ratio of the Mastens hardness of the adhesive layer after heat treatment at 260°C for 15 minutes to the Martens hardness of the adhesive layer before heat treatment (Mastens hardness after heat treatment at 260°C / Martens hardness before heat treatment) is 25 to 70.

3. The adhesive sheet according to claim 1, which is releasably attached to a lead frame or a wiring board of a semiconductor device and is used in the manufacturing process of the semiconductor device. 　 The adhesive sheet according to any one of claims 1 to 3, wherein the adhesive layer contains a phenolic antioxidant. 　 The adhesive sheet according to any one of claims 1 to 4, wherein the adhesive layer does not contain a fluororesin. 　 The adhesive sheet according to any one of claims 1 to 5, wherein the adhesive layer does not contain a silicone resin. 　 The adhesive sheet according to any one of claims 1 to 6, wherein the adhesive layer contains 75% by mass or more of unhydrogenated styrene-butadiene-styrene copolymer (SBS). 　 A precursor of a semiconductor device, in which a semiconductor element is mounted on one main surface of a lead frame or the wiring board of the semiconductor device, the semiconductor element is sealed with a sealing resin, and the adhesive sheet according to any one of claims 1 to 7 is releasably attached to the other main surface of the lead frame or the wiring board of the semiconductor device. 　 A semiconductor device manufactured using the adhesive sheet according to any one of claims 1 to 7. 　 A method for manufacturing a semiconductor device using the adhesive sheet according to any one of claims 1 to 7.

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