This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2022-0082759, filed on Jul. 5, 2022, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.
Embodiments of the present disclosure relate to a release film and a method for manufacturing the same, and more particularly, to a release film for a mold process used in a mold process of a semiconductor package, and a method for manufacturing the same.
In a mold process of a semiconductor packaging process, semiconductor chips may be sealed with a molding resin. As a molding resin, epoxy molding compound (EMC) is mainly used. The mold process, or molding, is simpler and more productive than any other processing method, and is currently most commonly used in the semiconductor packaging process. Molding resins, such as EMC, are inferior in thermal stability and reliability, compared to ceramic materials, but they are inexpensive and highly productive, so they are currently used in most semiconductor packaging processes. Meanwhile, in a semiconductor packaging process, a molding resin may be injected into a mold to seal semiconductor chips, and in this process, the molding resin may be attached to a surface of the mold, thereby contaminating the mold and causing other semiconductor packages to be defective.
In order to address a problem of the related art, a release film may be attached to a mold so that a molding resin may not directly contact a surface of the mold to prevent contamination.
Embodiments of the present disclosure provide a release film for a mold process, capable of minimizing defects of a semiconductor package in a semiconductor packaging process, and a method for manufacturing the same.
In addition, the problems to be solved by embodiments of the present disclosure are not limited to the problems mentioned above, and other problems and solutions may be clearly understood by those skilled in the art from the following description.
According to embodiments of the present disclosure, a release film for a mold process is provided. The release film includes: a base film; and a plurality of conductive fillers that are in or on the base film, the plurality of conductive fillers including external conductive fillers that are on at least one from among an upper surface and a lower surface of the base film, such that the external conductive fillers provide roughness to the at least one from among the upper surface and the lower surface of the base film, wherein a conductive path is formed between the upper surface and the lower surface of the base film.
According to embodiments of the present disclosure, a release film for a mold process is provided. The release film includes: a base film as a monolayer; and a plurality of conductive fillers, the plurality of conductive fillers including: internal conductive fillers inside the base film; first external conductive fillers on an upper surface of the base film; and second external conductive fillers on a lower surface of the base film, wherein at least a portion of the first external conductive fillers and at least a portion of the second external conductive fillers protrude from the upper surface and the lower surface of the base film, respectively, and wherein the first external conductive fillers on the upper surface are connected to the second external conductive fillers on the lower surface through the internal conductive fillers that are inside the base film.
According to embodiments of the present disclosure, a method for manufacturing a release film is provided. The method includes: preparing a resin for a base film; obtaining a resin-filler mixture by mixing a plurality of conductive fillers with the resin; and obtaining the release film in a form of a thin film using the resin-filler mixture, wherein the release film includes the base film, as a monolayer, and the plurality of conductive fillers, wherein the plurality of conductive fillers are in or on the base film, and the plurality of conductive fillers includes external conductive fillers that are on at least one from among an upper surface and a lower surface of the base film, such that the external conductive fillers provide roughness to the at least one from among the upper surface and the lower surface of the base film, and wherein a conductive path is formed between the upper surface and the lower surface of the base film.
Embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:
Hereinafter, non-limiting example embodiments are described in detail with reference to the accompanying drawings. The same reference numerals are used for the same components in the drawings, and redundant descriptions thereof are omitted.
It will be understood that when an element or layer is referred to as being “over,” “above,” “on,” “below,” “under,” “beneath,” “connected to” or “coupled to” another element or layer, it can be directly over, above, on, below, under, beneath, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly over,” “directly above,” “directly on,” “directly below,” “directly under,” “directly beneath,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present.
Referring to
The base film 110 may be formed based on resins generally used in a release film for a mold process. For example, in the release film 100 of the present embodiment, the base film 110 may include an ethylene tetrafluoroethylene (ETFE) resin, a polyethylene terephthalate (PET) resin, a polybutylene terephthalate (PBT) resin, or a poly tetrafluoroethylene (PTTE) resin. However, a material of the base film 110 is not limited to the above materials. In addition, in the release film 100 of the present embodiment, a thickness D1 of the base film 110 may be about 30 μm to about 150 μm. However, the thickness D1 of the base film 110 is not limited to the above numerical range.
For reference, a release film of a comparative embodiment may generally have a multi-layer structure. In the case of the release film, an extrusion method may be used to give roughness to the film. For example, in the extrusion method, roughness may be given to the release film through a roll-to-roll (R2R) process. However, for the extrusion method, only expensive ETFE, PET, and PBT resins are available. In addition, there is a casting method as a film manufacturing method, and the casting method may use a relatively inexpensive PTFE resin. However, in the case of the casting method, although roughness may be given through coating, a multi-step process is required, which may lead to an increase in manufacturing cost. Because there is no process for giving roughness thereto, the casting method cannot be used for manufacturing a release film.
In the case of a multilayer release film according to a comparative embodiment, an antistatic layer (AS) layer for electrostatic discharge (ESD) prevention may be required. Therefore, because a process for coating the AS layer on the base film has to be performed, this may be disadvantageous in terms of cost and time. In addition, because there is no strong bond, such as covalent bonding between the AS layer and the base film, peeling may frequently occur between the AS layer and the base film during the mold process, which may interfere with continuous workability of the mold process. Furthermore, adhesion of the AS layer to the surface of the mold may cause a defect in the release film and also contaminate the surface of the mold.
However, in the case of the release film 100 of the present embodiment, because roughness is formed by the conductive filler 120, a separate roughness giving process is unnecessary, and therefore, both an injection method and the casting method may be used. As a result, the release film 100 of the present embodiment may use an inexpensive PTFE resin as the base film 110. In relation to the manufacturing of the release film 100 of the present embodiment, the injection method and the casting method are described in more detail below with reference to
Because the release film 100 of the present embodiment has a single-layer structure, cost and time may be reduced by skipping an AS layer coating process. In addition, due to the single-layer structure of the release film 100 of the present embodiment, the peeling between the AS layer and the base film may be solved, thereby improving continuous workability of the mold process.
Meanwhile, a material of the base film 110 is described in terms of curing as follows. That is, the base film 110 may be formed of an ultraviolet (UV)-curable resin. Here, the UV-curable resin may refer to a resin that may be UV-cured. The UV-curable resin may include, for example, at least one selected from urethane acrylate, polyester acrylate, polyether, acrylic acrylate, epoxy acrylate, and fluorinated acrylate. Moreover, the base film 110 may further include a thermosetting resin in the ultraviolet curable resin. In the case of such a base film 110, double curing may be performed by UV rays and heat, and accordingly, a curing speed may increase.
The base film 110 may be formed of a thermosetting resin. Here, the thermosetting resin may refer to a resin that may be cured by heat. The thermosetting resin may include, for example, at least one selected from an epoxy resin, a vinyl resin, and an allyl resin. The thermosetting resin may undergo a crosslinking reaction by a curing agent under high temperature conditions, and thus, a curing reaction may proceed.
The epoxy resin may include, for example, a bisphenol F epoxy resin, a cresol novolac epoxy resin, a phenol novolac epoxy resin, a biphenyl epoxy resin, a stilbene epoxy resin, a hydroquinone epoxy resin, a naphthalene epoxy resin, a tetraphenylolethane epoxy resin, a DPP epoxy resin, a trishydroxyphenylmethane epoxy resin, a dicyclopentadienephenol type epoxy resin, and the like, but is not limited thereto. In addition, the vinyl resin may include, for example, a resin having a 1,2-vinyl group, a cis 1,4-vinyl group, and a trans 1,4-vinyl group in a molecule, but is not limited thereto.
The conductive filler 120 may be spread and distributed throughout the base film 110. In other words, the conductive filler 120 may be spread and distributed on an upper surface St and a lower surface Sb of the base film 110 and throughout the inside of the base film 110. As shown in
In the release film 100 of the present embodiment, the conductive filler 120 may be disposed to have a protruding structure on the lower surface Sb of the base film 110. In addition, the conductive filler 120 may include an external conductive filler 120out located in a protruding structure on the lower surface Sb of the base film 110 and an internal conductive filler 120in located inside the base film 110. The release film 100 of the present embodiment may give roughness to the surface of the molding resin by transferring roughness formed on the lower surface Sb of the base film 110 to the surface of the molding resin in the mold process. As such, because the release film 100 of the present embodiment gives roughness to the surface of the molding resin during the mold process, defects, such as chip transparency, in a semiconductor package sealed with the molding resin may be prevented. A process of transferring the roughness of the lower surface Sb of the base film 110 to the surface of the molding resin to give roughness to the molding resin is described in more detail with reference to
When the conductive filler 120 protrudes from both the upper surface St and the lower surface Sb of the base film 110, there is no need to clearly distinguish between the upper surface St and the lower surface Sb of the base film 110. A case in which the conductive filler 120 protrudes from both the upper surface St and the lower surface Sb of the base film 110 is described in detail below with reference to
The conductive filler 120 may have various shapes to form roughness on the upper surface St and/or the lower surface Sb of the base film 110. For example, as shown in
As can be seen from
For the ESD preventing function, the conductive filler 120, as the term itself indicates, may be conductive. The conductive filler 120 may be divided into a metal-based filler and a carbon-based filler. The metal-based filler may include, for example, a metal filler and a metal oxide filler having conductivity. In addition, the carbon-based filler may include carbon black (CB), carbon fiber (CF), carbon nanotube (CNT), and the like. However, the material of the conductive filler 120 is not limited to the materials described above.
For reference, CB is a black, fine carbon powder. CB is similar to graphite, and carbon particles may have a size of about 1 nm to about 500 nm. Such CB may be mixed with thermosetting and thermoplastic resins for color, coloration, or other functional purposes, and may be produced in various types by combining particle size, an agglomerated structure, and surface chemical properties.
CF is a material that is lighter than steel and is ten times stronger than steel. CF may be used as an alternative material in most industries where iron is used. In particular, CF may be utilized in the manufacture of hydrogen fuel tanks that may withstand high pressure.
CNT is a new material in the form of a cylinder in which hexagons made of six carbons are connected to each other to form a tube. CNT is a material having excellent strength, modulus of elasticity, abrasion resistance, and excellent electrical and thermal conductivity, and is a material that may be either electrically conductive or a semiconductor depending on an angle at which CNT is rolled or a length of a tube diameter. Because CNT has excellent physical properties and chemical stability, CNT may be used to make a resin with strong electrical conductivity.
In addition, CNT may manifest excellent conductivity even by a very small amount, compared to CB and CF. Due to these characteristics of CNT, CNT has been widely used in aircrafts, automobile wear-resisting materials, lightweight materials, aerospace, and sports and leisure products, and have become prominent as a material leading the future.
The release film 100 of the present embodiment may prevent the molding resin from directly contacting the mold during the mold process of the semiconductor packaging process, thereby preventing contamination of the mold. In addition, the release film 100 of the present embodiment may have roughness on the lower surface Sb of the base film 110 due to the plurality of the conductive filler 120 arranged in a protruding structure on the lower surface Sb of the base film 110. The roughness on the lower surface Sb of the base film 110 may be transferred to the surface of the molding resin during the mold process. Accordingly, the molding resin may have roughness on a surface thereof, and thus, defects, such as chip transparency of the semiconductor package sealed with the molding resin, may be prevented. Furthermore, the release film 100 of the present embodiment may have the conductive path provided between the upper surface St and the lower surface Sb of the base film 110 through the conductive filler 120 provided on the upper surface St and the lower surface Sb and distributed inside thereof. Accordingly, the release film 100 of the present embodiment may prevent ESD during the mold process and effectively prevent ESD defects of a semiconductor package.
Referring to
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For reference, chip transparency may occur as a thickness of the molding resin is reduced in the mold process due to a reduction in weight, thickness, length, and size of the semiconductor package. However, in the release film 100 of the present embodiment, by giving roughness to the surface of the molding resin 200a in the mold process, diffused reflection of light may occur on the surface of the molding resin 200a, and accordingly, the chip transparency may be removed.
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Up to this point, various shapes of the conductive filler included in the base film 110 of the release film 100 of the present embodiment have been described. However, in the release film 100 of the present embodiment, the shape of the conductive filler included in the base film 110 is not limited to the shapes described above. For example, the conductive filler is not limited to a sphere, a hemisphere, or an elliptical sphere which is solid, and may have a polyhedral shape, such as a triangular pyramid, triangular prism, or quadrangular prism which is solid. In addition, the conductive filler may have a shape without an open hole, while having a hollow shell shape. Meanwhile, the conductive filler may have a size of several tens to several hundreds of nm. However, the size of the conductive filler is not limited to the numerical range mentioned above.
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Up to this point, a method for manufacturing the conductive filler 120b of
Meanwhile, in the release film 100 of the present embodiment, the method for manufacturing the conductive filler is not limited to the template method. For example, in the release film 100 of the present embodiment, the conductive filler may be manufactured through a spraying method. For reference, the spraying method may refer to a method for making a conductive filler by forming a filler precursor in a gaseous form and then curing the filler precursor through a spraying process. The conductive filler formed by the spraying method may be hollow or solid depending on properties of the material and synthesis conditions (e.g., solvent, temperature, time, etc.).
Referring to
The first external conductive filler 120out1 may be disposed on the lower surface Sb of the base film 110 in a structure in which at least a portion thereof protrudes. The second external conductive filler 120out2 may be disposed on the upper surface St of the base film 110 in a structure in which at least a portion thereof protrudes. The internal conductive filler 120in may be evenly distributed throughout the inside of the base film 110. In addition, the first external conductive filler 120out1 may be connected to the second external conductive filler 120out2 by the internal conductive filler 120in. Accordingly, the base film 110 may include a conductive path by the conductive filler 120′ between the upper surface St and the lower surface Sb thereof. The release film 100a of the present embodiment may effectively prevent ESD in a mold process.
Meanwhile, as described above, the first external conductive filler 120out1 on the lower surface Sb of the base film 110 may form roughness on the lower surface Sb of the base film 110. In addition, the roughness on the lower surface Sb of the base film 110 may be transferred to the surface of the molding resin in the mold process to prevent chip transparency defects in the semiconductor package sealed with the molding resin.
The second external conductive filler 120out2 on the upper surface St of the base film 110 may also form roughness on the upper surface St of the base film 110. However, because the upper surface St of the base film 110 is attached to an inner surface of a mold, roughness on the upper surface St of the base film 110 does not have a function of transferring and giving roughness to the molding resin, but contributes to increasing a peeling effect. In other words, when the release film 100a is separated from the mold, peeling may easily take place due to the roughness formed on the upper surface St of the base film 110.
As a result, the release film 100a of the present embodiment may prevent ESD defects in the mold process during semiconductor package manufacturing, and may solve a chip transparency in a finally released product in the form of a package. For reference, ESD defects may result from a decrease in bandwidth of a semiconductor device and thinning of an ESD protection circuit, and the chip transparency may be attributed to the lightness and thinness of the semiconductor package. The ESD defects may be solved by giving the release film conductive properties. In addition, the chip transparency of the semiconductor package may be solved by providing roughness to the surface of the molding resin constituting the outer shape of the semiconductor package. The release film 100a of the present embodiment provides conductive properties to the release film 100a through the conductive filler 120′, thereby preventing ESD defects in the mold process. In addition, roughness may be formed on the lower surface Sb of the base film 110 through the conductive filler 120′ and transferred and given to the surface of the molding resin in the mold process, thereby preventing chip transparency defects in the semiconductor package.
The release film 100a of the present embodiment may include the conductive filler 120′ in the base film 110 for antistatic properties, that is, an ESD prevention function, while having a single layer shape. In addition, because the conductive filler 120′ has a hollow shape, the roughness of the release film 100a may increase. The conductive filler 120′ may have the various structures as those described above with reference to
The release film 100a of the present embodiment may also be manufactured by an extrusion method or a casting method depending on the type of resin. In the case of the extrusion method, for example, ETFE resin, PET resin, PBT resin, and the like may be used. In the extrusion method, the release film may be manufactured by melting a resin for the base film, adding a conductive filler thereto and mixed, and then extruding the mixture. Meanwhile, in the case of the casting method, for example, a PTFE resin may be used. In the casting method, the release film may be manufactured by mixing a resin for a base film with a conductive filler in a solvent and then performing a film casting process thereon.
In the release film 100a of the present embodiment, surface resistance may be about 104 Ω/sq to about 1012 Ω/sq. In the unit of surface resistance, “sq” is an abbreviation of square, which may refer to cm2. However, the surface resistance of the release film 100a is not limited to the above numerical range. In addition, in the release film 100a of the present embodiment, surface roughness may be about 0.5 μm to about 10 μm. Here, the surface roughness may be a value based on average roughness. However, the surface roughness of the release film 100a is not limited to the above numerical range.
Referring to
Meanwhile, the release film 100b of the present embodiment may not include an internal conductive filler. Accordingly, although not shown, a separate conductive path structure may be included between the upper surface St and the lower surface Sb of the base film 110. For example, a plurality of metal wires passing through the base film 110 may be disposed in the base film 110. In addition, ends of each of the metal wires may be exposed from the upper surface St and the lower surface Stb of the base film 110.
Referring to
Next, a resin-filler mixture is generated (S130). The resin-filler mixture refers to a state in which a resin for a base film is mixed with a conductive filler, and may be in a fluid state. For example, in the case of manufacturing a release film by using an extrusion method, the resin-filler mixture may be in a state in which a conductive filler is mixed with a resin for a base film in a melted state. In addition, in the case of manufacturing a release film by using the casting method, the resin-filler mixture may be in a state in which a resin for a base film is mixed with a conductive filler in a solvent.
After the resin-filler mixture is formed, a release film in the form of a thin film is generated by using the resin-filler mixture (S150). The release film in the form of a thin film may have a form in which the conductive filler 120, the conductive filler 120′, or the conductive filler 120″ are included in the base film 110, like the release film 100, the release film 100a, or the release film 100b of
Meanwhile, in the method for manufacturing a release film of the present embodiment, the release film in the form of a thin film may be produced through an extrusion method. A process of manufacturing a release film through the extrusion method is described in more detail in with reference to
In the method for manufacturing a release film of the present embodiment, while the release film is manufactured to have a single-layer structure through the process described above, roughness and a conductive path may be provided to the single-layer release film. Accordingly, in the method for manufacturing a release film of the present embodiment, a separate process of giving roughness may not be necessary, and also, a coating process of an AS layer may be unnecessary. As a result, because the method for manufacturing a release film of the present embodiment is advantageous in terms of cost and time, manufacturing cost of the release film may be significantly reduced. In addition, because the release film according to the method for manufacturing a release film of the present embodiment does not have an AS layer, peeling between the base film and the AS layer in the mold process, the defect of the release film due to the AS layer, and contamination of the mold may be fundamentally solved.
Referring to
Next, a conductive filler is mixed with the fluid resin (S133). The conductive filler may be a metal-based filler or a carbon-based filler. The metal-based filler may include, for example, a metal filler and a metal oxide filler having conductivity. Meanwhile, the carbon-based filler may include carbon black (CB), carbon fiber (CF), carbon nanotube (CNT), and the like. However, the material of the conductive filler is not limited to the materials described above. In this manner, the resin-filler mixture may be produced by mixing the conductive filler with the fluid resin in a molten state.
Referring to
The injection unit 1100 is a portion into which the resin-filler mixture R-Fcom. is injected, and may have a structure in which an upper portion thereof is wide and a lower portion thereof is narrow, similar to a funnel. However, a structure of the injection unit 1100 is not limited thereto. The body unit 1200 is a portion through which the resin-filler mixture R-Fcom. flows, and a screw-type rotating body is disposed therein, so that the resin-filler mixture R-Fcom. may move from the injection unit 1100 to the laminator unit 1300 according to rotation of the rotating body.
The laminator unit 1300 may also be referred to as a T-die, and may correspond to a portion in which the resin-filler mixture R-Fcom. is pulled out as an initial film 100′ in the form of a thin film. A long and narrow exit hole is provided in a lower portion of the laminator unit 1300, and as the resin-filler mixture R-Fcom. is ejected through the exit hole by a compression force, the initial film 100′ in the form of a thin film may be formed. Meanwhile, the initial film 100′ in the form of a thin film ejected through the laminator unit 1300 may be completed as the final release film (e.g., the release film 100, the release film 100a, or the release film 100b) through a curing process.
Referring to
Referring to the resin-filler mixture generating operation (S130) of
Referring to
In the dispensing section (Dispensing), the resin-filler mixture R-Fcom. may be dispensed onto a conveyor belt C.B. through a dispenser. The conveyor belt C.B. may be, for example, a stainless steel belt. The resin-filler mixture R-Fcom. may be spread thinly and widely on the conveyor belt C.B. through rotation of the conveyor belt C.B.
In the coating/drying section (Coating/Drying), the solvent may be removed from the resin-filler mixture R-Fcom. through drying. In
Thereafter, in the winding section (Winding), the release film (e.g., the release film 100, the release film 100a, or the release film 100b) may be wound on a roll, such as a mother roll M.R. The release film (e.g., the release film 100, the release film 100a, or the release film 100b) wound on the mother roll M.R. may be cut and used by a required amount in a subsequent mold process.
While non-limiting example embodiments of the present disclosure have been particularly shown and described, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure.
Number | Date | Country | Kind |
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10-2022-0082759 | Jul 2022 | KR | national |