Mold release film and chip packaging method

Abstract

GPA. A chip packaging method is also provided, and in the chip packaging method, the mold release film is used in at least one molding operation for forming a resin material into a package body encapsulating a chip. Therefore, a packaged device with a smooth and burr-free appearance can be obtained.

Description

[Technical Field]

[0001] This invention relates to a release film and its application, and more particularly to a release film for molding, and a wafer packaging method using the release film. [Previous Technology]

[0002] With the rapid development of technology and the continuous expansion of end-user applications, the demand for semiconductor chips is constantly increasing. To ensure that the chips operate normally without being affected by external factors (light, heat, water, gas, physical impact), resin is used for encapsulation. In the chip packaging process, the encapsulating resin is usually molded into a package that encapsulates the chip by transfer molding or compression molding.

[0003] In the molding process, a carrier plate carrying the semiconductor wafer to be packaged is placed in a mold cavity between upper and lower molds, and the mold cavity is filled with encapsulating resin (such as epoxy resin) to seal the wafer. Since the encapsulating resin is adhesive to the mold surface when molten, a release film is often used and laid along the mold surface to avoid direct contact between the resin and the mold surface, thus eliminating the need for cleaning steps to remove resin adhering to the mold surface. Additionally, the release film allows the resin to easily separate from the mold surface after curing.

[0004] However, when the release surface of the release film does not adhere well to the mold surface (or the surface of the substrate on the packaging side), resin may seep out from the gaps, causing uneven packaging, poor packaging appearance (such as burrs), and other defects. In addition, when high-power components are used in advanced processes, heat dissipation components are additionally sealed in the packaging section, and there is also a risk of resin seepage at the heterogeneous interface between the heat dissipation components and the release film. [Summary of the Invention]

[0005] The technical problem to be solved by the present invention is to provide a release film for molding, which can adhere well to the surface of the mold to obtain a packaged device with a smooth and burr-free appearance, in order to overcome the shortcomings of the prior art. On this basis, the present invention further provides a wafer packaging method that uses the release film in at least one molding operation.

[0006] To solve the above-mentioned technical problems, one of the technical solutions adopted by the present invention is to provide a release film for molding, suitable for attaching to the surface of a mold. The release film for molding includes a substrate layer attached to the surface of the mold and a release layer formed on the substrate layer. In the present invention, the thickness ratio of the substrate layer to the release layer is in the range of 1:1 to 100:1; the coefficient of contact friction between the substrate layer and the mold surface is in the range of 0.19 to 0.23; and the composite elastic modulus of the release film for molding is in the range of 4 GPa to 8 GPa.

[0007] In a feasible or preferred embodiment of the present invention, the material of the release layer comprises an acrylic resin, and the material of the substrate layer comprises a polyester resin.

[0008] In a feasible or preferred embodiment of the present invention, the glass transition temperature of the acrylic resin is -60°C to -20°C, and the glass transition temperature of the polyester resin is 60°C to 90°C.

[0009] In a feasible or preferred embodiment of the present invention, the acrylic resin is a copolymer of butyl methacrylate and butyl acrylate, and the polyester resin is polyethylene terephthalate.

[0010] In a feasible or preferred embodiment of the present invention, the total thickness of the release film for molding is 25 μm to 100 μm.

[0011] In a feasible or preferred embodiment of the present invention, the tensile breaking strength of the molding release film in the longitudinal direction is 1000 MPa to 1200 MPa, according to JIS K7127 standard and tested at 175°C.

[0012] In a feasible or preferred embodiment of the present invention, the elongation at break of the molding release film in the longitudinal direction is 200% to 220% according to JIS K7127 standard and tested at 175°C.

[0013] In order to solve the above-mentioned technical problems, another technical solution adopted by the present invention is to provide a wafer packaging method, which includes: providing a mold assembly, including a first mold and a second mold disposed opposite to each other, wherein the first mold has a first mold surface, the second mold has a second mold surface, and a molding cavity is provided between the first mold surface and the second mold surface; placing a carrier plate on which a wafer to be packaged is mounted is placed on the first mold surface and aligned with the molding cavity, and attaching a molding release film as described above to the second mold surface; supplying an encapsulation resin material to the molding cavity; and closing the first mold and the second mold to perform a molding operation, so that the encapsulation resin material is molded into a package encapsulating the wafer.

[0014] In a feasible or preferred embodiment of the present invention, the step of placing the encapsulating resin material in the molding cavity further includes placing a heat sink on the release layer and aligning it with the molding cavity; in the molding operation, the heat sink is attached to the package and positioned to correspond to the wafer.

[0015] In a feasible or preferred embodiment of the present invention, during the molding operation, the encapsulating resin material has a minimum melt viscosity of 34,000 cps at 140°C and a spiral flow length of 160 cm to 200 cm as measured according to ASTM D3123.

[0016] In general, the release film for molding provided by the present invention can control the thickness ratio of the substrate layer to the release layer in the range of 1:1 to 100:1, control the contact friction coefficient between the substrate layer and the mold surface in the range of 0.19 to 0.23, and control the composite elastic modulus of the release film in the range of 4GPa to 8GPa, so that the release film can adapt to the concave and convex shape of the mold surface during the molding operation and completely adhere to the mold surface without dead corners or adhesion gaps, thereby achieving stable and reliable performance.

[0017] Furthermore, the release film of the present invention is easy to deform with the shape of the mold surface, and the degree of matching between it and the mold surface is sufficient to form a good seal, thereby preventing the encapsulation resin material from leaking out of the mold during the molding operation, and ensuring the good appearance and performance of the encapsulated device.

[0018] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention.

Implementation Method

[0019] The following specific embodiments illustrate the implementation of the "release film for molding and wafer packaging method" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. Furthermore, the accompanying drawings of this invention are for simple illustration only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention.

[0020] It should be understood that although terms such as “first,” “second,” and “third” may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term “or” as used herein may, as appropriate, include any combination of one or more of the associated listed items.

[0021] [Release film for molding]

[0022] Please refer to FIG1, which shows a release film 1 for molding according to an embodiment of the present invention. As shown in FIG1, the release film 1 of the present invention includes a substrate layer 11 and a release layer 12 deposited on the substrate layer 11. The release film 1 of the present invention can be used for molding of various resins, such as, but not limited to, compression molding of epoxy resin or polysiloxane resin. Furthermore, the release film 1 of the present invention is adapted to be attached to a mold surface to prevent encapsulating resin material from adhering to the mold surface and to allow the encapsulated body formed by the encapsulating resin material to be easily separated from the mold surface.

[0023] It is worth noting that by controlling the composite elastic modulus of the release film 1, the thickness ratio of the substrate layer 11 to the release layer 12, and the contact friction coefficient between the substrate layer 11 and the mold surface, the present invention enables the release film 1 to adapt to the concave and convex shapes of the mold surface during the molding operation and to completely adhere to the mold surface without dead corners or adhesion gaps, thereby achieving stable and reliable performance.

[0024] In this invention, the thickness ratio of the substrate layer 11 to the release layer 12 is in the range of 1:1 to 100:1, for example, 90:1, 80:1, 70:1, 60:1, 50:1, 40:1, 30:1, 20:1, 10:1 or lower; the contact friction coefficient between the substrate layer 11 and the mold surface is in the range of 0.19 to 0.23; the composite elastic modulus of the release film 1 is in the range of 4 GPa to 8 GPa, and the composite elastic modulus of the release film 1 includes the elastic modulus of the elastic deformation of the substrate layer 11 and the elastic deformation of the release layer 12.

[0025] The tensile breaking strength of the release film 1 of the present invention in the longitudinal direction is 1000 MPa to 1200 MPa, as tested at 175°C according to JIS K7127 standard. Furthermore, the elongation at break of the release film 1 of the present invention in the longitudinal direction is 200% to 220%, as tested at 175°C according to JIS K7127 standard.

[0026] The total thickness of the release film 1 of the present invention can be from 25 μm to 100 μm, preferably from 38 μm to 75 μm, and more preferably from 40 μm to 65 μm. Therefore, the followability of the release film 1 to the mold surface can be improved, that is, the release film 1 can more easily deform with the shape of the mold surface.

[0027] The substrate layer 11 may be formed of a material whose main component is polyester resin. For example, based on a total weight of 100 wt% of the material forming the substrate layer 11, the content of polyester resin may be 50 wt% or more, 75 wt% or more, or 90 wt% or more; the polyester resin may be a homopolymer resin or a copolymer resin. In practical applications, the substrate layer 11 may be a uniaxially or biaxially extended polyester substrate layer, and preferably a biaxially extended polyester substrate layer.

[0028] As needed, an appropriate amount of particles (such as inorganic or organic particles) can be mixed into the material forming the substrate layer 11 to control the coefficient of contact friction between the substrate layer 11 and the mold surface within the aforementioned range. There are no particular restrictions on the type, shape, and size of the particles used, and they can be selected according to actual needs. For example, spherical silicon dioxide with an average particle size of less than 5 μm can be selected.

[0029] Representative examples of homopolymer resins include polyethylene terephthalate (PET) and polybutanediol terephthalate (PBT). Representative examples of copolymer resins include copolymers of terephthalic acid, ethylene glycol, and other comonomers; the comonomers may be dicarboxylic acid components or diol components. The dicarboxylic acid component may be selected from one or more of the following dicarboxylic acids: isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid. The diol component may be selected from one or more of the following diols: ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, and neopentyl glycol. However, the present invention is not limited to the examples mentioned above.

[0030] In one preferred embodiment, the substrate layer 11 is formed of polyethylene terephthalate having a glass transition temperature of 60°C to 90°C, which helps to improve the fit between the release film 1 and the mold surface to form a good seal, thereby preventing the encapsulation resin material from leaking out of the mold during the molding operation and ensuring the good appearance and performance of the encapsulated device.

[0031] The release layer 12 may be formed using a material whose main component is acrylic resin. For example, based on a total weight of 100 wt% of the material forming the substrate layer 11, the content of acrylic resin may be 50 wt% or more, 75 wt% or more, or 90 wt% or more; the acrylic resin may be a homopolymer resin or a copolymer resin. In practical applications, the material forming the release layer 12 may be coated onto one side of the substrate layer 11, and then cured by heating, but the present invention is not limited thereto.

[0032] The molecular weight of the acrylic resin can be from 500,000 to 1,500,000, preferably from 80,000 to 120,000, and even more preferably from 90,000 to 110,000. The monomer components constituting the acrylic resin may include acrylate monomers and / or methacrylate monomers. The acrylate monomers may be selected from one or more of the following monomers: methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, 2-hexyl acrylate, etc. The methacrylate monomers may be selected from one or more of the following monomers: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, etc. However, the present invention is not limited to the examples given above.

[0033] In one preferred embodiment, the acrylic resin is a butyl methacrylate-butyl acrylate copolymer (poly(BMA-co-BA)), which has a glass transition temperature of -60°C to -20°C. It should be noted that poly(BMA-co-BA) does not readily react with encapsulating resins such as epoxy resin, and due to its low Tg, the hardness of the coating is reduced during the encapsulation process, thereby allowing for tight adhesion to the carrier, the wafer to be encapsulated, and the mold, preventing encapsulating resin leakage. Therefore, the release layer 12 exhibits good performance in terms of release properties, adhesion, and heat resistance.

[0034] [Wafer Packaging Method]

[0035] Please refer to Figure 2, which illustrates the implementation steps of a wafer packaging method according to an embodiment of the present invention. The wafer packaging method of the present invention uses the release film described in the first embodiment in at least one molding operation to mold an encapsulating resin material into a package covering the wafer to be packaged.

[0036] As shown in FIG2, the wafer packaging method of the present invention includes: step S1, providing a molding die, which includes a first mold surface, a second mold surface and a molding cavity located between the first mold surface and the second mold surface, which are disposed opposite to each other; step S2, placing a carrier plate on which a wafer to be packaged is mounted on the first mold surface and aligning it with the molding cavity, and attaching a release film to the second mold surface; step S3, supplying a packaging resin material to the molding cavity; and step S4, closing the first mold and the second mold to perform a molding operation, so that the packaging resin material is molded into a package covering the wafer.

[0037] As shown in Figure 3, the molding die 2 includes a first die 21 and a second die 22 disposed opposite to each other; the first die 21 is, for example, an upper die, and the second die 22 is, for example, a lower die. The molding die 2 can be mounted on a packaging machine (not shown). When the first die 21 and the second die 22 are closed or opened, the second die 22 can be kept stationary while the first die 21 can be moved to approach or move away from the second die 22; or, the first die 21 can be kept stationary while the second die 22 can be moved to approach or move away from the first die 21. In addition, the first die 21 has a first die surface 210, the second die 22 has a second die surface 220, and a molding cavity 200 is provided between the first die surface 210 and the second die surface 220.

[0038] In practical applications, the encapsulating resin material M can be supplied to the molding cavity 200 when the first mold 21 and the second mold 22 are closed or open. The encapsulating resin material M can be a liquid or granular resin material, and the encapsulating resin material M can be placed on the release film 1, but the present invention is not limited thereto. In addition, the molding operation conditions may include: molding temperature (mold temperature) of 160°C to 190°C; molding pressure of 5 MPa to 12 MPa; and molding time of 5 minutes to 15 minutes. With the presence of the release film 1, contact between the encapsulating resin material M and the molded part can be avoided, and the molded part can be easily removed from the molding mold 2.

[0039] As shown in Figure 3, to meet the heat dissipation requirements of the chip 4, a heat sink 6 (such as a heat sink plate) can be directly integrated onto the molded part of the encapsulation resin material M during encapsulation. Furthermore, between steps S2 and S3, the heat sink 6 can be placed on the release layer 12 and aligned with the molding cavity 200, so that during the molding operation, the heat sink 6 can be bonded to a package 5 formed by the encapsulation resin material M and its position corresponds to the chip 4. It is worth noting that, to prevent the encapsulation resin material M from seeping between the heat sink 6 and the release layer 12, the minimum melt viscosity of the encapsulation resin material M before thermosetting at 140°C is 34000 cps, and the spiral flow length measured according to ASTM D3123 is 160 cm to 200 cm.

[0040] As shown in FIG4, the packaged device obtained by the wafer packaging method of the present invention may include a carrier plate 3, a wafer 4, a package body 5, and a heat sink 6. The wafer 4 is mounted on the carrier plate 3, the package body 5 is formed on the carrier plate 3 and encapsulates the wafer 4, and the heat sink 6 is integrated with the package body 5.

[0041] [Beneficial Effects of the Embodiments]

[0042] The release film for molding provided by the present invention can control the thickness ratio of the substrate layer to the release layer within the range of 1:1 to 100:1, control the contact friction coefficient between the substrate layer and the mold surface within the range of 0.19 to 0.23, and control the composite elastic modulus of the release film within the range of 4GPa to 8GPa, so that the release film can adapt to the concave and convex shape of the mold surface during the molding operation and completely adhere to the mold surface without dead corners or adhesion gaps, thereby achieving stable and reliable performance.

[0043] Furthermore, the release film of the present invention is easy to deform with the shape of the mold surface, and the degree of matching between it and the mold surface is sufficient to form a good seal, thereby preventing the encapsulation resin material from leaking out of the mold during the molding operation, and ensuring the good appearance and performance of the encapsulated device.

[0044] Furthermore, the release film of the present invention has excellent tensile properties, including tensile strength at break in the length direction, which is 1000 MPa to 1200 MPa according to JIS K7127 standard and tested at 175°C, and tensile elongation at break in the length direction, which is 200% to 220% according to JIS K7127 standard and tested at 175°C. Therefore, the release film of the present invention can be reused in molding operations more than twice, and does not break after multiple uses, maintaining stable performance, thereby reducing packaging costs.

[0045] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention. [Simplified Explanation of the Diagram]

[0046] Figure 1 is a schematic diagram of the release film for molding according to the present invention.

[0047] Figure 2 is a flowchart of the wafer packaging method of the present invention.

[0048] Figure 3 is a schematic diagram of the molding operation of the wafer packaging method of the present invention.

[0049] Figure 4 is a schematic diagram of the packaged device obtained by the wafer packaging method of the present invention.

Claims

1. A release film for molding, suitable for attachment to a mold surface, the release film comprising a substrate layer attached to the mold surface and a release layer formed on the substrate layer, the release layer being made of an acrylic resin having a glass transition temperature of -60°C to -20°C, and the substrate layer being made of a polyester resin having a glass transition temperature of 60°C to 90°C; wherein, The thickness ratio of the substrate layer to the release layer is in the range of 1:1 to 100:1; wherein the coefficient of friction between the substrate layer and the mold surface is in the range of 0.19 to 0.23; wherein the composite elastic modulus of the release film for molding is in the range of 4 GPa to 8 GPa.

2. The release film for molding as described in claim 1, wherein, The acrylic resin is a copolymer of butyl methacrylate and butyl acrylate, and the polyester resin is polyethylene terephthalate.

3. The release film for molding as described in claim 1, wherein, The total thickness of the release film used for molding is 25 μm to 100 μm.

4. The release film for molding as described in claim 1, wherein, The tensile breaking strength of the molded release film in the longitudinal direction is 1000 MPa to 1200 MPa, as measured by JIS K7127 and tested at 175°C.

5. The release film for molding as described in claim 1, wherein, The elongation at break of the molded release film in the longitudinal direction is 200% to 220% according to JIS K7127 standard and tested at 175°C.

6. A wafer packaging method, comprising: A mold assembly is provided, comprising a first mold and a second mold disposed opposite to each other, wherein the first mold has a first mold surface, the second mold has a second mold surface, and a molding cavity is provided between the first mold surface and the second mold surface; a carrier plate on which a wafer to be encapsulated is mounted is placed on the first mold surface and aligned with the molding cavity, and a molding release film as described in claim 1 is attached to the second mold surface; an encapsulation resin material is supplied to the molding cavity; and the first mold and the second mold are closed to perform a molding operation to form the encapsulation resin material into an encapsulation body encapsulating the wafer.

7. The wafer packaging method as described in claim 6, wherein, The step of placing the encapsulating resin material into the molding cavity further includes placing a heat sink on the release layer and aligning it with the molding cavity; in the molding operation, the heat sink is attached to the package and positioned to correspond to the wafer.

8. The wafer packaging method as described in claim 7, wherein, In this molding operation, the encapsulating resin material has a minimum melt viscosity of 34,000 cps at 140°C and a spiral flow length of 160 cm to 200 cm as measured according to ASTM D3123.

Images