Release film

Abstract

The invention provides a mold release film. The mold release film is provided with a mold release layer and a base material layer, the base material layer is a biaxially stretched polybutylene terephthalate film, the mold release film is stretched at an elongation of 10-50% in the longitudinal direction (MD) of the mold release film under the conditions of a temperature of 175 DEG C, a sample width of 15 mm, an initial inter-chuck distance of 50 mm, and a stretching speed of 50 mm / min, and after the stretched state is maintained for 2 minutes, the base material layer is a biaxially stretched polybutylene terephthalate film. When the steel sheet is moved in a direction opposite to the direction of elongation at a speed of 50 mm / min until the stress is zero, the recovery rate (%) obtained on the basis of the value [Delta] La of the elongation length when the steel sheet is elongated from the initial value and the recovery value [Delta] Lb of the elongation from the [Delta] La to the stress is zero is 40-80%. When used in a resin sealing process using a compression molding method, the mold release film does not generate wrinkles or cracks even if stretching occurs during the process, has excellent sealing resin peelability, has excellent recyclability, and has recoverability after being stretched in a high-temperature state.

Description

Technical Field

[0001] This invention relates to a release film used in resin molding using compression molding, and more specifically, to a release film that does not wrinkle or crack and has excellent peelability used in resin sealing of semiconductor chips using compression molding to protect semiconductor components. Background Technology

[0002] In recent years, the packaging technology for protecting and sealing semiconductor components has shifted from sealing components one by one to sealing larger areas in wafer-level packaging (WLP) and panel-level packaging (PLP), and mass production of these technologies is also underway.

[0003] In the packaging processes applied to large-area WLP and PLP, the traditional method involves placing the wafer and the semiconductor chip mounted on the substrate within a mold, injecting resin, and sealing the resin through compression molding. To facilitate easy removal of the molded resin seal from the mold, a release film is placed between the inner surface of the mold and the semiconductor chip, etc., for example, depending on the application, release films such as PTFE, ETFE, PET, FEP, polypropylene, polystyrene, and polyvinylidene chloride are used (Patent Document 1).

[0004] When using these release films in compression molding, the release film disposed on the mold surface is stretched once by vacuum suction and then shrinks when the mold is compressed, resulting in wrinkles in the release film. This problem becomes more pronounced as the area and depth of the mold cavity increase, especially at the periphery of the mold cavity, where wrinkled release films are trapped by the sealed resin, leading to problems such as failure to demold and breakage.

[0005] To address this issue, as a membrane that is less prone to wrinkling during stretching, a release membrane with a specific composition and manufacturing method has been proposed, namely, an ethylene-tetrafluoroethylene (ETFE) copolymer membrane (Patent Document 2), a stretching membrane having a 4-methyl-1-pentene copolymer (PMP) membrane laminated on a release layer and a stretching membrane containing 50% to 100% by mass of polybutylene terephthalate laminated on a support layer (Patent Document 3).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2017-35832

[0009] Patent Document 2: International Publication No. 2018 / 008562

[0010] Patent Document 3: Japanese Patent Application Publication No. 2020-1328 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, the fluoropolymer membrane proposed in Patent Document 2 has the following problems: it is difficult to burn during waste incineration after use, produces toxic gases, has a high environmental impact, and is expensive. In contrast, the release membrane proposed in Patent Document 3 produces almost no toxic gases during incineration, but due to the lamination of membranes of different materials, its recyclability is poor. Furthermore, the thermal properties of the support layer membrane and the release layer PMP membrane differ, causing a portion of the release layer to peel off from the support during compression molding, forming wrinkles, and various problems such as being trapped by the sealing resin.

[0013] The purpose of this invention is to provide a release film for use in a resin sealing process based on compression molding. This release film does not wrinkle or crack even after stretching during the process, exhibits excellent peelability to the sealing resin, excellent recyclability, and resilience after stretching at high temperatures.

[0014] Technical solutions for solving the problem

[0015] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that biaxially stretched polybutylene terephthalate film with a substrate layer and a release layer provided on at least one side of the substrate layer are particularly suitable as release films for use in the resin sealing process in compression molding. After stretching the film by 10% to 50% at a temperature of 175°C and a stretching speed of 50 mm / min and holding it in the same state for 2 minutes, the recovery rate when the film recovers to zero stress in the direction opposite to the stretching direction at a speed of 50 mm / min is 40% or more and 80% or less, thus completing the present invention.

[0016] That is, the present invention relates to a release film using biaxially stretched polybutylene terephthalate as a substrate layer, and the release film described in [1] to [8] below and the resin sealing method of the semiconductor device using the release film described in [9] below may be a mode or aspect of the present invention.

[0017] [1] A release film having a release layer and a substrate layer, wherein,

[0018] The substrate layer is a biaxially stretched polybutylene terephthalate film.

[0019] Under the conditions of temperature 175℃, sample width 15mm, initial chuck distance 50mm, and tensile speed 50mm / min,

[0020] The release film is stretched along its length direction (MD) with an elongation rate of 10% to 50%, held in this stretched state for 2 minutes, and then restored in the opposite direction of the stretching direction at a speed of 50 mm / min until the stress is zero.

[0021] Based on the elongation length value ΔLa from the initial value before elongation to the value at the time of elongation, and the elongation recovery value ΔLb from the elongation length value at the time of elongation to the elongation length value when the stress is 0, the recovery rate (%) obtained according to the following formula (1) is 40% or more and 80% or less.

[0022] Recovery rate (%) = [Elongation recovery value ΔLb / Elongation length value ΔLa] × 100・・・(1)

[0023] [2] In the release film described in [1], the biaxially stretched polybutylene terephthalate film of the substrate layer, under the conditions of a temperature of 175°, a sample width of 15 mm, an initial chuck distance of 50 mm, and a stretching speed of 50 mm / min, has a tensile stress of 10 MPa to 40 MPa when stretched to an elongation of 10% to 50% in all four directions (0° (MD), 45°, 90° (TD), 135°).

[0024] The ratio of the maximum to the minimum tensile stress in the four directions is less than 1.5.

[0025] [3] In the release film described in [1], the heat shrinkage rate of the release film after 30 minutes at 175°C is 1.5% or more in both its length direction (MD) and width direction (TD).

[0026] [4] In the release film described in [1], the thickness of the substrate layer is 15 μm or more and 25 μm or less, the thickness of the release layer is 0.1 μm or more and 5 μm or less, and the puncture strength of the release film as determined according to JIS Z 1707 is 9 N or more.

[0027] [5] In the release film described in [1], the release layer is a layer that does not contain silicon and is formed on at least one surface of the substrate layer.

[0028] [6] The release film described in [1] also has an antistatic layer disposed between the release layer and the substrate layer, or the release layer is disposed on one side of the substrate layer and the antistatic layer is disposed on the other side of the substrate layer.

[0029] [7] In the release film described in [1], the release film is a process release film used in a resin sealing process based on compression molding.

[0030] [8] In the release film described in [7], the release film is a process release film used in a resin sealing process based on the compression molding method, and is stretched and compressed in the process.

[0031] [9] A method for sealing a semiconductor device with resin, which uses a release film described in any one of [1] to [8].

[0032] Invention Effects

[0033] The present invention provides a release film that, in a resin sealing process based on compression molding, will not wrinkle or crack even after stretching and compression (expansion), and has excellent peelability to the sealing resin and is resilient after stretching at high temperature.

[0034] In addition, the present invention can provide a method for forming a resin seal of a semiconductor element using the release film. Attached Figure Description

[0035] Figure 1 This is a schematic cross-sectional view illustrating an example of a process for manufacturing a seal (semiconductor element) using the compression molding method of the release film of the present invention.

[0036] Figure 2 A conceptual diagram illustrating the determination of the recovery rate of the release film involved in this invention is shown. Detailed Implementation

[0037] The embodiments of the present invention will now be described in detail. The present invention relates to a release film having a release layer and a substrate layer, wherein the substrate layer is a biaxially stretched polybutylene terephthalate film. The release film is stretched and held under specified conditions as described later, and then, upon release of the stretch, the recovery rate, calculated based on the elongation length of the film at the time of stretching and the recovery value recovered from the elongation length at the time of release, is 40% or more and 80% or less.

[0038] <Substrate layer: Biaxially stretched polybutylene terephthalate film>

[0039] The release film of the present invention uses a biaxially stretched polybutylene terephthalate (PBT) film as the substrate layer. Furthermore, in this specification, PBT will also be referred to as “PBT”, and the biaxially stretched PBT film will also be referred to as “biaxially stretched PBT film”, etc.

[0040] The biaxially stretched PBT film mentioned above is a biaxially stretched film of PBT resin. In this invention, the PBT resin is not particularly limited as long as it is a polyester with butylene terephthalate as the main repeating unit. Specifically, it can be set as: a homopolymer polyester (polybutylene terephthalate) obtained by condensing 1,4-butanediol (glycol component) or its ester derivative, and terephthalic acid or its ester derivative (diacid component) as the main components, or a copolymer polyester with said polybutylene terephthalate as the main component.

[0041] Furthermore, in this invention, to impart the most suitable mechanical strength properties, the polybutylene terephthalate resin described above is preferably a resin with a melting point of 200–250°C and an intrinsic viscosity (IV value) in the range of 0.90 dl / g–1.35 dl / g, and more preferably a resin with a melting point of 215–225°C and an intrinsic viscosity (IV value) in the range of 1.15 dl / g–1.30 dl / g. Moreover, the intrinsic viscosity (IV value) of the polybutylene terephthalate resin is the solution viscosity measured at 30°C using a mixed solvent of phenol and tetrachloroethane (mass ratio 1 / 1).

[0042] Furthermore, the copolymer-type polyesters (copolyesters) listed above that are based on polybutylene terephthalate refer to substances obtained by replacing a portion of the terephthalic acid component, which is a diacid component, with other diacid components such as isophthalic acid, phthalic acid, adipic acid, and sebacic acid, and / or by condensing substances obtained by replacing a portion of the 1,4-butanediol component, which is a glycol component, with other glycol components such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, and cyclohexanediol. As a copolyester, copolyesters with 70% or more terephthalate units are preferably examples.

[0043] Furthermore, in the biaxially stretched PBT film according to the present invention, the polybutylene terephthalate resin used can be mixed with other polyesters such as polyethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate, and polyethylene isophthalate, as well as other resins such as polycarbonate and polyamide, within a range that does not impair physical properties, before undergoing the stretching process described later. Alternatively, the polybutylene terephthalate resin and the other polyesters and other resins can be laminated and then subjected to stretching processing. Two or more of the aforementioned other polyesters and other resins can be used.

[0044] Furthermore, in this invention, a biaxially stretched film composed solely of PBT resin, a biaxially stretched film composed of a mixed resin containing PBT resin, and a biaxially stretched film composed of two or more layers of PBT resin and other resin layers can all be used as biaxially stretched PBT films as the substrate layer of the release film involved in this invention.

[0045] Furthermore, in manufacturing biaxially stretched PBT films, in addition to the polybutylene terephthalate resin (or, depending on the circumstances, other resins mentioned above) used in this invention, additives such as lubricants, anti-blocking agents, inorganic extenders, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, plasticizers, colorants, crystallization inhibitors, and crystallization promoters may be added as needed.

[0046] In addition, for polybutylene terephthalate resin granules used in membrane manufacturing, in order to avoid viscosity reduction caused by hydrolysis during heating and melting, it is preferable to pre-dry them thoroughly before use, preferably with a water content of 0.05% by mass or less, more preferably 0.02% by mass or less before heating and melting.

[0047] When the biaxially stretched polybutylene terephthalate film, which serves as the substrate layer in the release film of the present invention, is stretched to an elongation of 10% to 50% at a temperature of 175°C, a sample width of 15 mm, an initial chuck distance of 50 mm, and a tensile strength of 50 mm / min, the tensile stress in all four directions (0° (MD), 45°, 90°, 135° (TD)) of the film is 10 MPa to 40 MPa. Furthermore, the ratio of the maximum to the minimum tensile stress in the four directions can be 1.5 or less.

[0048] In the vacuum suction of the mold or the heat adsorption mechanism used when making the release film, in order to adsorb the mold without wrinkles and to have conformity, the tensile stress in the four directions is more preferably in the range of 12 MPa to 35 MPa. In addition, for the ratio of the maximum to the minimum tensile stress in the four directions, the more complex and large the shape of the compression molding mold is, the more isotropic conformity is required, and it is more preferable to have a small ratio, that is, less than 1.2.

[0049] The biaxially stretched polybutylene terephthalate film is obtained by extruding the polybutylene terephthalate resin into a film using an extruder and then stretching the resulting film.

[0050] The following is an example of a method for manufacturing a biaxially stretched polybutylene terephthalate film used in the substrate layer of the release film of the present invention.

[0051] First, the polybutylene terephthalate resin is melt-blended using an extruder set to a specified temperature (e.g., 210–280 °C).

[0052] Next, film formation is performed, but the film formation method is not particularly limited. For example, in the case of film formation with a T-die, sheet-like molten resin is immersed in a water bath to directly cool both the inside and outside with water. On the other hand, in the case of annular film formation, molten tubular film is formed by extruding from an annular die mounted downwards on the extruder.

[0053] Next, the film is introduced into a cooling mandrel connected to an annular die head. Cooling water introduced from each nozzle of the cooling mandrel directly contacts the inner side of the molten tubular film to cool it. Simultaneously, cooling water also flows from an external cooling tank used in conjunction with the cooling mandrel, directly contacting the outer side of the molten tubular film to cool it. The temperature of both the internal and external water is preferably below 30°C, and from the viewpoint of rapid film formation, it is particularly preferred to be below 20°C. If the temperature exceeds 30°C, it can lead to whitening of the unstretched film or poor appearance of the unstretched film due to boiling of the cooling water, and sometimes stretching gradually becomes difficult.

[0054] Furthermore, in order to stably manufacture biaxially stretched polybutylene terephthalate (PBPT) films, it is necessary to suppress the crystallization of the unstretched film (also known as the unstretched preform) before stretching. As mentioned above, when forming a film by cooling the PBPT melt extruded from an extruder, the cooling rate must be at least within the crystallization temperature range of the PBPT. Therefore, the cooling rate of the unstretched film becomes a crucial factor. This cooling rate is 200°C / second or higher, preferably 250°C / second or higher, and particularly preferably 350°C / second or higher. When the cooling rate is below 200°C / second, the resulting unstretched film exhibits higher crystallinity, and its stretchability may decrease.

[0055] As for the film formation method of unstretched film, there is no particular limitation as long as the cooling rate of the unstretched film is met, but from the viewpoint of rapid cooling film formation, the above-mentioned direct internal and external water cooling method is particularly preferred.

[0056] There are no particular limitations on the method for biaxial stretching the unstretched film. For example, a suitable method can be selected from simultaneous biaxial stretching using a tubular film method or a tenter frame method, or sequential biaxial stretching using alternating longitudinal and transverse stretching. From the viewpoint of balancing the longitudinal and transverse strengths of the resulting biaxially stretched polybutylene terephthalate film, simultaneous biaxial stretching based on the tubular film method is particularly preferred.

[0057] Regarding the stretch ratio, considering factors such as tensile stability, the strength properties of the resulting biaxially stretched polybutylene terephthalate (PET) film, and thickness uniformity, the length direction (hereinafter also referred to as "MD") and width direction (hereinafter also referred to as "TD") are preferably in the range of 2.7 to 4.0 times, respectively. When the stretch ratio is less than 2.7 times, the tensile strength and impact strength of the resulting biaxially stretched PET film may be insufficient, and therefore it is not preferred. Furthermore, when the stretch ratio exceeds 4.0 times, excessive strain on the molecular chains occurs due to stretching, leading to frequent breakage and fracture during the stretching process, potentially resulting in unstable production.

[0058] The stretching temperature is preferably in the range of 40°C to 80°C, and particularly preferably 45°C to 65°C. Unstretched films manufactured at the aforementioned high cooling rates have low crystallinity, thus allowing for stable stretching at relatively low temperatures. At high-temperature stretching above 80°C, the stretching bubbles become violently swayed, resulting in large stretching unevenness, which may prevent the production of films with good thickness accuracy. On the other hand, at stretching temperatures below 40°C, excessive stretching orientation crystallization occurs due to low-temperature stretching, leading to film whitening, etc., and depending on the situation, the stretching bubbles may rupture, making further stretching difficult.

[0059] By performing such biaxial stretching, biaxially stretched polybutylene terephthalate films with low anisotropy can be obtained.

[0060] The obtained biaxially stretched polybutylene terephthalate (PET) film can be heat-treated for any duration in a heat treatment apparatus consisting of a hot roller, a tenter frame, or a combination thereof, at a temperature of, for example, 180–240°C, particularly preferably 190–210°C. This process yields a PET film with excellent thermal dimensional stability. At heat treatment temperatures above 240°C, excessive bending occurs, and anisotropy in the width direction may increase. Conversely, at heat treatment temperatures below 180°C, the thermal dimensional stability of the film decreases significantly, potentially causing problems in the hot-pressing process.

[0061] Furthermore, to improve adhesion to the release layer, the obtained biaxially stretched polybutylene terephthalate film can be treated with easy-adhesion processes such as corona discharge, plasma, or ultraviolet light, or applied using online or offline easy-adhesion coatings. Moreover, to follow the contours of the mold during compression molding, provide venting during adsorption, and control release properties, embossing can be used to create contours on the surface.

[0062] In the release film of the present invention, the thickness of the substrate layer (biaxially stretched polybutylene terephthalate film) can be appropriately designed within a range that does not impair the effects of the present invention, and is typically 10 to 50 μm, taking into account conveyability, winding properties, etc. From the viewpoint of more reliably preventing breakage during use, it is preferable to set it to 15 μm or more. In addition, from the viewpoint of making it easier to follow the contours of the mold and reducing the environmental impact during manufacturing and disposal, it is preferable to set it to 25 μm or less.

[0063] <Mold Release Layer>

[0064] The release layer constituting the release film of the present invention can be appropriately designed, to the extent that it does not impair the effects of the present invention, in conjunction with the compression-molded resin to which the release film is applied.

[0065] Furthermore, epoxy resins are primarily used as resins in compression molding for sealing electronic components such as semiconductor elements. Release agent components with good release properties relative to epoxy resins include silicone resins, fluorinated resins, olefin resins, acrylic resins, and melamine resins, which can be used individually or in combination in the release layer involved in this invention.

[0066] In particular, when using release films to seal electronic components such as semiconductor elements, it is preferable to select release agent components that do not contain silicon, considering the possibility of insulation failure or other malfunctions in the electronic components. Furthermore, to prevent cracking of the release layer during mold following, it is preferable to select a material with an elongation of 10% or more, and more preferably a material with an elongation of 50% or more. Additionally, to increase elongation, soft resins, polyurethane-based resins, etc., can be added to the release agent components for the release layer, within a range that does not impair the effects of the present invention.

[0067] The thickness of the release layer of the release film of the present invention can be appropriately designed within a range that does not impair the effect of the present invention. Considering processability, recyclability, etc., it can be set to 0.1 μm to 5 μm. In order to obtain more reliable release properties, it is preferable to set the thickness of the release layer to 0.3 μm or more, and in order to suppress the occurrence of cracks when following the mold, it is preferable to set it to 2 μm or less.

[0068] Furthermore, when manufacturing the release film, the release layer only needs to be provided on the surface in contact with the aforementioned sealing resin, etc. For example, it can be provided on at least one surface of the substrate layer, or on both surfaces of the substrate layer. Alternatively, other layers can be provided between the release layer and the substrate layer.

[0069] Furthermore, without compromising the effectiveness of the present invention, organic or inorganic particles may be added to the release layer to impart release properties, conveyability, and designability. Additionally, antistatic agents and conductive agents that suppress static electricity generation may also be added.

[0070] <Method for manufacturing release film>

[0071] The release film of the present invention can be manufactured by forming a release agent constituting the release layer on the aforementioned biaxially stretched polybutylene terephthalate film, which serves as the substrate layer, using known wet coating or dry coating methods. Examples of wet coating methods include reverse roller coating, dip coating, Mayer rod coating, doctor blade coating, nozzle coating, mold coating, spray coating, curtain coating, screen printing, and gravure coating. Examples of dry coating methods include vacuum evaporation, sputtering, and ion plating, where the raw material is heated and evaporated in a vacuum. The method for curing and fixing the release layer is not particularly limited and can be achieved using high-temperature heating, ultraviolet irradiation, electron beam irradiation, plasma irradiation, etc.

[0072] <Mold Release Film: Recovery Rate>

[0073] The release film of the present invention is characterized by having a predetermined recovery rate. By having this predetermined recovery rate, even when the release film of the present invention is used in a resin sealing process using compression molding, wrinkles and cracks can be suppressed even after the film undergoes elongation / compression during the process. Furthermore, the encroachment of the film into the sealing resin can be suppressed.

[0074] The recovery rate involved in this invention is defined and measured as follows.

[0075] First, under conditions of 175°C, a sample width of 15 mm, an initial chuck distance of 50 mm, and a stretching speed of 50 mm / min, the release film is stretched along its length (MD) with an elongation of 10% to 50%. At this time, one end of the sample is fixed, and the other end is stretched along its length. This stretched state is then maintained for 2 minutes. After holding, the other end is moved (recovered) at a speed of 50 mm / min in the opposite direction to the stretching direction until the stress on the other end during stretching becomes zero.

[0076] During this series of operations, the recovery rate (%) is calculated according to the following formula (1), based on the elongation length value ΔLa from the initial value before elongation to the value at elongation, and the elongation recovery value ΔLb from the elongation length value at elongation to the elongation length value when the stress is 0.

[0077] Recovery rate (%) = [Elongation recovery value ΔLb / Elongation length value ΔLa] × 100 ・・・ (1)

[0078] The recovery rate is more preferably 50% or higher and 75% or lower.

[0079] exist Figure 2 The diagram shows a conceptual representation of the recovery rate measurement involved in this invention. Figure 2 As shown, a sample with an initial value of ΔL0 (50 mm) is stretched and held to an elongation of x% under the conditions described above, starting from the initial value ΔL0 and ending at the elongation of x%. The elongation length from the initial value ΔL0 to the length reached at the elongation of x% is then ΔLa. Furthermore, the ratio of the initial value ΔL0 to the elongation length ΔLa is the elongation of x% (elongation of x (%) = (ΔLa / ΔL0) × 100).

[0080] After maintaining the state with an elongation of x% for 2 minutes, the specimen is restored to its original state under the conditions described above, so that the load (stress) on the tensile portion becomes 0. Then, the elongation recovery value ΔLb is measured from the elongation length value ΔLa when the elongation reaches the elongation of x% to the elongation length value when the stress is 0.

[0081] Then, using the above ΔLa and ΔLb, calculate the recovery rate according to the above formula (1). If the elongation value ΔLa = the elongation recovery value ΔLb, the recovery rate is 100%; if the elongation recovery value ΔLb = 0, the recovery rate is 0%.

[0082] <Mold Release Film: Heat Shrinkage Rate>

[0083] The release film of the present invention has a thermal shrinkage rate of 1.0% or more, more preferably 1.5% or more, and even more preferably 2.0% or more, in both its length direction (MD) and width direction (TD) after 30 minutes at a temperature of 175°C. By producing a film with a thermal shrinkage rate of 1.0% or more, the film exhibits good conformability to the uneven shape of the mold used for compression molding, and wrinkles of the film on the mold surface can be suppressed.

[0084] The thermal shrinkage rate can be calculated, for example, as follows: a sample membrane that will be the object is cut into quadrilaterals of 100 mm in the MD and TD directions, and then treated (stored) at 175°C for 30 minutes. The lengths in each direction before and after treatment are measured and calculated according to the following formula (2).

[0085] Heat shrinkage rate (%) = [(length before treatment - length after treatment) / length before treatment] × 100・・・(2)

[0086] <Mold release film: puncture strength>

[0087] The puncture strength of the release film of the present invention, as measured according to JIS Z 1707, can be 7N or more, for example, 9N or more, and more preferably 10N or more. By producing a film with a puncture strength of 7N or more, the release film is less prone to pore formation during transport in a compression molding apparatus, and can reliably adhere to and follow the unevenness of the mold through vacuum suction, resulting in less loss during manufacturing.

[0088] The release film of the present invention may also include other layers besides the release layer, such as an antistatic layer, without compromising the effects of the present invention. The antistatic layer suppresses the release film from becoming charged, prevents the adsorption of dust and other particles generated by the cutting of the sealing resin material, and prevents damage to electronic components due to electrostatic discharge during compression molding.

[0089] An antistatic layer may be disposed between the release layer and the substrate layer, for example. In addition, if the release layer is disposed on one side of the substrate layer, the antistatic layer may be disposed on the other side of the substrate layer.

[0090] In one embodiment, the release film of the present invention has a release layer that does not contain silicon components, exhibits excellent mold conformability at high temperatures, recovery during compression, and release properties, and also has heat resistance. Therefore, it is particularly suitable as a release film for compression molding, for example, in processes where resin is used to seal electronic components such as semiconductor elements.

[0091] That is, the release film of the present invention can be used as a process release film in a resin sealing process based on compression molding. In addition, the release film of the present invention is a process release film used in a resin sealing process based on compression molding and is stretched and compressed in the process.

[0092] <Resin Seal Formation Method>

[0093] The release film described above can be used when sealing materials such as semiconductors with resin.

[0094] A resin seal forming method for performing resin sealing based on compression molding using the release film involved in the present invention is configured to include, for example, the following steps (i) to (iv), but is not limited to these steps.

[0095] (i) The process of arranging the release film in such a way as to cover the opening of the recess of a mold having a recess;

[0096] (ii) The process of stretching the configured release film so that it follows the inner surface of the recess of the mold;

[0097] (iii) The process of filling the release film following the recess with sealing resin material, and the process of placing the sealed surface of the body to be sealed at a predetermined position in the recess of the mold (iii) in such a way as to face the sealing resin material on the release film;

[0098] (iv) A process of forming a resin seal on the sealed surface by compressing the sealing resin material.

[0099] <Manufacturing Method of Sealing Body>

[0100] Furthermore, the release film involved in this invention can be used in methods for manufacturing hermetically sealed bodies such as semiconductors.

[0101] A method for manufacturing a seal (semiconductor, etc.) by compression molding is configured to include, for example, the following steps (a) to (f), but is not limited to these steps.

[0102] (a) A process in which the release film according to the present invention is arranged in a lower mold having a lower mold and an upper mold having a recess formed by the bottom surface that is movable vertically, such that the release film covers the opening of the recess of the lower mold.

[0103] (b) The process of stretching the configured release film by vacuum suction to make it follow the inner surface of the recess of the mold;

[0104] (c) The process of filling the release film following the recess with a sealing resin material;

[0105] (d) The process of placing a sealed body with a sealed surface between an upper mold and a lower mold such that the sealed surface is opposite to the sealing resin material on the release film, and then closing the upper mold and the lower mold.

[0106] (e) A process of moving the bottom surface of the lower mold to compress the stretched release film while compressing the sealing resin material to form a resin sealing part on the sealed surface.

[0107] (f) The process of opening the upper mold and the lower mold and removing the sealing body.

[0108] The release film involved in this invention can, for example, be used after... Figure 1 The schematic cross-sectional views of processes (A) to (D) show the process used in the manufacturing method of the seal (e.g., a semiconductor device). Furthermore, this manufacturing method is not limited to those including... Figure 1 The process shown is as follows.

[0109] Figure 1(A) is a schematic diagram showing the process of arranging a release film in such a way that it covers the opening (cavity) of the recess of the lower mold of the compression molding mold.

[0110] exist Figure 1 In (A), the compression molding die consists of an upper die 2 and a lower die 3. The lower die 3 consists of a lower side die 3-1 and a lower bottom die 3-2 that is movable vertically. In addition, a semiconductor element 4 (the sealed body) is provided on the lower surface of the upper die 2. At this time, the semiconductor element 4 is provided in such a way that the lower bottom die 3-2 is opposite to the sealed surface 4a of the semiconductor element 4 (the sealed body).

[0111] Then, a release film 1 is provided so as to cover the opening 3b of the recess 3a of the lower mold 3.

[0112] Figure 1 (B) is a schematic diagram illustrating the following steps: stretching the mold release film by vacuum suction to make it follow the inner surface of the recess of the mold; and filling the mold release film following the recess with a sealing resin material.

[0113] exist Figure 1 In (B), the suction device (not shown) is used to draw the contents of the container. Figure 1 In (A), the release film 1 faces towards Figure 1 The material is stretched downwards to follow the inner surface of the recess 3a of the lower mold 3. Here, the stretched release film is used as release film 1a. At this time, the lower bottom mold 3-2 is heated while suction is being applied, so that the lower surface of the stretched release film 1a following the mold becomes molten, allowing it to adhere (adhere) tightly to the lower bottom mold 3-2. Then, a sealant resin material 5, before curing, is placed and filled onto the stretched release film 1a.

[0114] In addition, Figure 1 In (B), the upper mold 2 is shown facing... Figure 1 The process of moving (descending) to the lower side is shown, and the process of mold closing is illustrated by the upper mold 2 and the lower mold 3 (lower side mold 3-1) being connected through the release film 1a.

[0115] Figure 1 (C) is a schematic diagram illustrating the following process: placing a sealed body having a sealed surface between an upper mold and a lower mold such that the sealed surface is opposite to the sealing resin material on the release film, and closing the upper mold and the lower mold; and moving the bottom surface of the lower mold to compress the stretched release film while compressing the sealing resin material to form a resin sealing portion on the sealed surface.

[0116] exist Figure 1 In (C), the upper mold 2 and the lower side mold 3-1 are joined together through the release film 1a. After the upper and lower molds are closed, the lower bottom mold 3-2 faces towards... Figure 1 Move upwards. Through this movement, in... Figure 1 In (B), the stretched release film 1a is compressed to become a shrunken release film 1b, and the sealing resin material 5 is compressed and formed, that is, the sealing resin material 5 is cured, forming a resin sealing part 6 (i.e., sealed with resin) on the sealed surface 4a of the semiconductor element (sealed body) 4. In addition, the sealing resin material 5 is molten by heating the lower bottom mold 3-2, compressed and formed (compression sealing) and cured to become the resin sealing part 6.

[0117] Figure 1 (D) shows the following state: After the sealing surface 4a of the semiconductor element (sealed body) 4 is sealed by the sealing resin material 5 to form the resin sealing part 6, the lower bottom mold 3-2 is oriented towards Figure 1 The (D) moves downward (descends) and causes the upper mold 2 to rise to open the mold. At this time, the release film 1c is usually peeled off from the resin sealing part 6 formed on the semiconductor element (sealed body) 4.

[0118] In the above Figure 1 In the series of processes shown, the release film is from... Figure 1 The state of the release film 1 of (A) becomes to follow Figure 1 The state of the mold 1a is stretched in the form of the recess 3a of the mold (B).

[0119] Then, through the action of the mold, from Figure 1 In (B), the depth of the recess 3a in the mold is stretched to the state of the release film 1a. Figure 1 The demolding film 1b is compressed to a depth of about 1 / 2 to 1 / 3 of the depth of the recess 3a of the mold in (C). That is, the stretched demolding film 1a becomes a demolding film 1b that has shrunk by about 50% to 70%.

[0120] In this invention, by producing a release film with a recovery rate of 40% or more as defined above, during compression molding, the film located at... Figure 1 The release film 1b-1 portion on the side of the recess 3a of the mold shown in (C) is less prone to wrinkling. If the recovery rate of the release film is low, for example, if there is film residue in the release film 1b-1 portion, wrinkles are easily formed, and the wrinkled portion of the release film is easily bitten into the sealing resin material 5. In the case of the sealing resin material causing the release film to be bitten into, when the release film is bitten into the sealing resin material, Figure 1When the mold shown in (D) is opened, the release film is difficult to peel off from the resin seal 6. In cases of deep penetration, the release film may rupture, and the release film may remain inside the resin seal 6. Therefore, in order to achieve good release properties and prevent defects caused by penetration, it is preferable that the recovery rate of the release film is 50% or more.

[0121] However, if the recovery rate of the release film exceeds 80%, then during compression molding ( Figure 1 In the case of (C) state, excessive shrinkage of the release film may result in excessive lifting from the inner surface of the recess in the lower mold. To prevent this, from the viewpoint of obtaining a sealing resin thickness that meets the design, the upper limit of the recovery rate can be set to 80% or less. Furthermore, for better sealing, a recovery rate of 70% or less is more preferable.

[0122] [Example]

[0123] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to the following examples.

[0124] <Example 1>

[0125] Polybutylene terephthalate resin granules (same type, melting point = 224℃, IV value = 1.26 dl / g) were dried in a hot air dryer at 140℃ for 5 hours. The dried resin granules were then melt-blended in an extruder under barrel and die temperatures ranging from 210 to 260℃, and the molten tubular film was extruded downwards through an annular die. Next, the film was folded by a folding roller through the outer diameter of a cooling mandrel and then stretched into a film at a speed of 1.2 m / min using a traction clamping roller. The unstretched film formed under the above conditions was fed to a low-speed clamping roller in an atmosphere at 20℃ and subjected to simultaneous biaxial stretching in both directions using a tubular film method. The stretch ratios were MD = 3.1x, TD = 3.2x, and the stretching temperature was 60℃. Next, the biaxially stretched film was placed into a hot roller heat treatment device, followed by a tenter frame heat treatment device, and heat-treated at 210°C to obtain a biaxially stretched polybutylene terephthalate film. The thickness of the biaxially stretched polybutylene terephthalate film was 25 μm.

[0126] Next, using the biaxially stretched polybutylene terephthalate film as a substrate layer, the following release agent composition 1 was coated on one side using a gravure roller with a line count of 180 and a gravure coating machine. The mixture was then heated and dried at 120°C to form a release layer, resulting in the release film of Example 1. The thickness of the release layer was 0.5 μm.

[0127] (Mold release agent composition 1)

[0128] • Melamine-based mold release agent (ARACOAT (registered trademark) RL900, manufactured by Arakawa Chemical Industry Co., Ltd.) 5 parts by weight

[0129] • Crosslinking agent (ARACOAT RA2000 manufactured by Arakawa Chemical Industry Co., Ltd., a registered trademark) 1 part by weight

[0130] • Solvent: 200 parts by weight of methyl ethyl ketone

[0131] <Example 2>

[0132] Except for changing the melt-blending extrusion amount and setting the thickness of the biaxially stretched polybutylene terephthalate film to 15 μm, the same procedure as in Example 1 was followed to obtain the release film of Example 2.

[0133] <Example 3>

[0134] Except for changing the gravure roller to a gravure roller with wire number 110 when applying the release agent composition 1, and setting the thickness of the release layer to 4.0 μm, the operation was carried out in the same manner as in Example 1 to obtain the release film of Example 3.

[0135] <Comparative Example 1>

[0136] Except for changing the melt-blending extrusion amount and setting the thickness of the biaxially stretched polybutylene terephthalate film to 10 μm, the same procedure as in Example 1 was performed to obtain the release film of Comparative Example 1.

[0137] <Comparative Example 2>

[0138] The pretreatment and extrusion temperature of the polybutylene terephthalate (PPT) granules were the same as in Example 1, except that instead of a ring die, PPT was extruded from a T die and cooled to obtain an unstretched PPT film with a thickness of 50 μm. Using this unstretched PPT as the substrate layer, and in the same manner as in Example 1, a release agent was applied to obtain the release film of Comparative Example 2.

[0139] <Comparative Example 3>

[0140] Except for changing the substrate layer to a 25μm biaxially stretched polyethylene terephthalate film (trade name: Lumirror (registered trademark) T60, manufactured by Toray Industries, Inc.), the same operation as in Example 1 was performed to obtain the release film of Comparative Example 3.

[0141] <Comparative Example 4>

[0142] Except for changing the melt-blending extrusion amount and setting the thickness of the biaxially stretched polybutylene terephthalate film to 15 μm, the operation was carried out in the same manner as in Example 1 to obtain a biaxially stretched polybutylene terephthalate film that serves as the substrate layer.

[0143] In addition, except that polybutylene terephthalate was replaced with polymethylpentene, the same procedure was performed as in Comparative Example 2 to obtain an unstretched polymethylpentene film with a thickness of 50 μm, which was used as a release layer.

[0144] Next, the substrate layer and the release layer are dry laminated to obtain the release film of Comparative Example 4.

[0145] <Comparative Example 5>

[0146] No release layer is formed. The biaxially stretched polybutylene terephthalate film (thickness 25 μm) obtained in Example 1 is used as the release film for Comparative Example 5.

[0147] <Comparative Example 6>

[0148] No release layer is formed. The biaxially stretched polybutylene terephthalate film (15 μm thick) obtained in Example 2 is used as the release film for Comparative Example 6.

[0149] For the release films prepared in Examples 1 to 3 and Comparative Examples 1 to 6, the recovery rate, thermal shrinkage rate, tensile strength (substrate layer) at high temperature, and puncture strength of the release films were measured using the following methods. Additionally, a compression molding-based forming test was performed. Furthermore, the results for the recovery rate, thermal shrinkage rate, tensile strength, and puncture strength of the release films were the average values ​​of three tests. The results are shown in Table 1.

[0150] <Evaluation Items>

[0151] (1) Recovery rate of the release film

[0152] For the membrane recovery rate at high temperatures, a tensile testing machine with a constant temperature bath (TENSILON RTM-100 manufactured by ORIENTEC CORPORATION) was used.

[0153] Each release film of Examples 1-3 and Comparative Examples 1-4 was cut into 150 mm and 15 mm wide pieces along its length direction as test samples. These samples were stretched by 10% or 50% along their length direction under conditions of a chuck distance of 50 mm, an atmosphere temperature of 175°C, and a stretching speed of 50 mm / min (this stretching was taken as the stretching length value ΔLa [mm]). After maintaining this stretched state for 2 minutes, the chuck was restored in the opposite direction of the stretching at a speed of 50 mm / min. The displacement (recovery) when the stress applied to the chuck became 0 (load 0) was measured and taken as the elongation recovery value ΔLb [mm]. The recovery rate was calculated according to the following formula (1) based on ΔLa and ΔLb.

[0154] Membrane recovery rate (%) = [Elongation recovery value ΔLb / Elongation length value ΔLa] × 100・・・ (1)

[0155] (2) Heat shrinkage rate of release film

[0156] Each release film from Examples 1-3 and Comparative Examples 1-6 was cut into 100mm × 100mm pieces along the length direction (MD) × width direction (TD) to serve as samples for heat shrinkage rate determination. These samples were treated (stored) at 175°C for 30 minutes, and the lengths of MD and TD before and after treatment were measured. The heat shrinkage rates in the MD and TD directions were calculated according to the following formula (2).

[0157] Heat shrinkage rate (%) = [(length before treatment - length after treatment) / length before treatment] × 100・・・(2)

[0158] (3) Tensile strength at high temperature (substrate layer)

[0159] For tensile strength at high temperatures, a tensile testing machine with a constant temperature bath (TENSILE RTM-100 manufactured by ORIENTEC CORPORATION) was used.

[0160] For the film of the substrate layer used in the above embodiments and comparative examples, a sample with a width of 15 mm was cut out as a test sample. Under the conditions of a chuck distance of 50 mm, an atmosphere temperature of 175 °C, and a tensile speed of 50 mm / min, the loads at 10% or 50% elongation were read in four directions: 0° (MD) direction, 45° direction, 90° (TD) direction, and 135° direction. The tensile stress (MPa) was calculated by dividing the cross-sectional area (thickness × 15 mm) of the sample before the test.

[0161] In addition, the abbreviation for the film of the substrate layer is as follows.

[0162] • OPBT25 • • • Example 1, Example 3, Comparative Example 5

[0163] • OPBT15 • • • Example 2, Comparative Example 4, Comparative Example 6

[0164] •OPBT10 •••Comparative Example 1

[0165] • CPBT50 • Comparative Example 2

[0166] • PET25 • Comparative Example 3

[0167] (4) Puncture strength (release film)

[0168] For puncture strength, a Tensilon universal testing machine (TENSILON RTG-1210 manufactured by A&D Corporation) was used at 23°C and 50%RH. The circular needle at the tip (diameter 1 mm φ, R = 0.5 mm) was punctured into the release film of Examples 1-3 or Comparative Examples 1-6 at a puncture speed of 50 mm / min, and the strength (N) when the needle penetrated was measured.

[0169] (5) Forming test based on compression forming

[0170] A sealing resin was formed on an evaluation substrate using a compression molding machine manufactured by TOWA Corporation.

[0171] Rollers of the release films from Examples 1-3 or Comparative Examples 1-6 were mounted on a molding machine and conveyed to cover the recess of a lower mold heated at 175°C (adjusted to a length of 220mm × width of 54mm and a depth of 3.0mm) with the substrate layer of each release film facing the inner surface of the recess. The release film was then vacuum-suctioned to follow and adhere to the recess of the lower mold. Granular sealing resin (epoxy thermosetting resin, manufactured by Sumitomo Bakelite Co., Ltd.) was then applied to the release film on the recess of the lower mold (release layer side), and the sealing resin was melted by the heat (175°C) of the lower mold. Then, the upper mold, on which the evaluation substrate was mounted, was lowered and joined with the lower mold. The bottom of the recess of the lower mold was raised to make the thickness of the package 1.0mm. Compression molding was performed at a mold temperature of 175°C, a sealing time of 2 minutes, and a torque of 96kN to seal the evaluation substrate.

[0172] After the sealing resin has cured, each mold is opened, and the evaluation substrate with the sealing resin is separated from the release film.

[0173] (Demolding properties)

[0174] The demolding properties of the substrate used in the above molding test were evaluated from each demolding film using the following evaluation criteria.

[0175] 〇: After compression molding, when the mold is opened, the release film will naturally peel off.

[0176] ×: After compression molding, the release film did not peel off naturally when the mold was opened.

[0177] (Breakage during compression molding)

[0178] The following evaluation criteria were used to evaluate the rupture occurrence of each release film during the above molding tests.

[0179] 〇: After compression molding, when the mold is opened, there is no rupture of the release film at the periphery of the mold cavity.

[0180] ×: After compression molding, when the mold is opened, the release film breaks at the periphery of the mold cavity.

[0181] (Clamping and wrinkling during compression molding)

[0182] The occurrence of wrinkles and other defects in each release film during the above forming tests was evaluated using the following evaluation criteria.

[0183] 〇: There were no traces of release film being inserted into the side of the periphery of the resin seal, and no wrinkle patterns were observed on the surface of other resin seals.

[0184] △: There are traces of mold release film inserted into the side of the periphery of the resin seal, but no wrinkle pattern was observed on the surface of other resin seals.

[0185] ×: There are traces of mold release film stuck in the side of the periphery of the resin seal, and wrinkled patterns are also observed on the surface of other resin seals.

[0186] [Table 1]

[0187]

[0188] [Table 2]

[0189]

[0190] As shown in Tables 1 and 2, the release film of the present invention, which has a recovery rate of more than 40% and less than 80% after being stretched by 10% to 50% at 175°C, obviously does not have the cracks and wrinkles that occur during compression molding, and excellent release properties were found (Examples 1 to 3).

[0191] On the other hand, the release film of Comparative Example 1, which used a biaxially stretched polybutylene terephthalate film with a substrate thickness of 10 μm, was of poor quality and cracked during compression molding. This was attributed to the thin substrate layer, resulting in low strength at a molding temperature of 175°C.

[0192] In addition, as shown in Comparative Examples 2 and 3, release films with low recovery rates are prone to cracking and trapping, which is a poor result.

[0193] Furthermore, during compression molding, the release film of Comparative Example 4 developed wrinkles on the flat portion of the mold. These wrinkles were transferred to the sealing resin, forming a wrinkle pattern on the surface of the sealing resin. As a result, the appearance quality of the molded product (evaluation substrate) was compromised. The reason for this is believed to be the difference in thermal shrinkage between the release layer film and the substrate layer film (the thermal shrinkage rate (at 175°C) of the polymethylpentene in the release layer is 1% elongation in the MD direction and 1% shrinkage in the TD direction, while the thermal shrinkage rate (at 175°C) of the biaxially stretched PBT film in the substrate layer is more than 3% shrinkage in the MD direction and more than 1% shrinkage in the TD direction).

[0194] Furthermore, in Comparative Examples 5 and 6, which only had a biaxially stretched polybutylene terephthalate film without forming a release layer, the release films did not peel off naturally when the mold was opened after compression molding, and did not meet the evaluation of cracking and wrinkling. As a result, they were deemed unqualified as release films.

[0195] Industrial availability

[0196] According to the present invention, it is possible to provide a release film that does not produce wrinkles, has excellent peelability and recyclability, and is resilient after stretching at high temperatures, for use in compression molding processes.

[0197] Explanation of reference numerals in the attached figures

[0198] 1. Release film

[0199] 2. Upper mold

[0200] 3. Lower mold (3-1 Lower side mold, 3-2 Lower bottom mold)

[0201] 3a Recess, 3b Opening

[0202] 4. Semiconductor components (sealed bodies)

[0203] 4a Sealed surface

[0204] 5. Sealing resin material

[0205] 6. Resin sealing part

Claims

1. A release film having a release layer and a substrate layer, The substrate layer is a biaxially stretched polybutylene terephthalate film. Under the conditions of temperature 175℃, sample width 15mm, initial chuck distance 50mm, and tensile speed 50mm / min, The release film is stretched along its length direction (MD) with an elongation rate of 10% to 50%, held in this stretched state for 2 minutes, and then restored to zero stress at a speed of 50 mm / min in the opposite direction of stretching. Based on the elongation length value ΔLa from the initial value before elongation to the value at the time of elongation, and the elongation recovery value ΔLb from the elongation length value at the time of elongation to the elongation length value when the stress is 0, the recovery rate (%) obtained according to the following formula (1) is 40% or more and 80% or less. Recovery rate (%) = [Elongation recovery value ΔLb / Elongation length value ΔLa] × 100・・・(1) 2. The release film according to claim 1, wherein, The biaxially stretched polybutylene terephthalate film of the substrate layer exhibits tensile stresses of 10 MPa to 40 MPa in all four directions (0° (MD), 45°, 90° (TD), 135°) under the conditions of a temperature of 175°C, a sample width of 15 mm, an initial chuck distance of 50 mm, and a stretching speed of 50 mm / min, when elongated to an elongation of 10% to 50%. The ratio of the maximum to the minimum tensile stress in the four directions is less than 1.

5.

3. The release film according to claim 1, wherein, The release film has a heat shrinkage rate of more than 1.5% in both its length direction (MD) and width direction (TD) after 30 minutes at 175°C.

4. The release film according to claim 1, wherein, The thickness of the substrate layer is 15 μm or more and 25 μm or less. The thickness of the release layer is greater than 0.1 μm and less than 5 μm. The puncture strength of the release film, as determined by JIS Z 1707, is 9N or higher.

5. The release film according to claim 1, wherein, The release layer is a layer that does not contain silicon and is formed on at least one surface of the substrate layer.

6. The release film according to claim 1, wherein, The release film also has an antistatic layer, which is disposed between the release layer and the substrate layer, or the release layer is disposed on one side of the substrate layer and the antistatic layer is disposed on the other side of the substrate layer.

7. The release film according to claim 1, wherein, The release film is a process release film used in a resin sealing process based on compression molding.

8. The release film according to claim 7, wherein, The release film is a process release film used in a resin sealing process based on the compression molding method, and is stretched and compressed in the process.

9. A method for sealing a semiconductor element with resin, using the release film according to any one of claims 1 to 8.

Images