WO2025018204A1 - Adhesive sheet for workpieces and method for producing same - Google Patents

Abstract

This adhesive sheet for workpieces comprises: an adhesive layer that is configured so as to be affixed to a workpiece for an electronic device; and a release sheet that is disposed on the adhesive layer and can be removed from the adhesive layer. The release sheet has dust-free paper.

Description

Adhesive sheet for workpiece and method for manufacturing same

The present invention relates to an adhesive sheet for workpieces and a method for manufacturing the same.

When manufacturing electronic devices such as semiconductor devices, the workpiece is first prepared. The workpiece is then processed to form the electronic device.

When manufacturing electronic devices, adhesive sheets are sometimes attached to workpieces for various purposes. With regard to such adhesive sheets, Patent Document 1 (JP Patent Publication No. 2021-40099) discloses a composite sheet for forming a protective film having a specific configuration and which is attached to the back surface of a semiconductor wafer.

In recent years, there has been a demand to reduce carbon dioxide emissions in order to realize a sustainable world. The inventors wondered whether it would be possible to improve the amount of carbon dioxide emissions emitted during the manufacture of adhesive sheets, which are attached to workpieces during the manufacture of electronic devices.

The object of the present invention is to provide a technology that can improve carbon dioxide emissions from work adhesive sheets that are attached to workpieces for electronic devices.

The inventors focused on the release sheet included in the work adhesive sheet. They discovered that carbon dioxide emissions can be reduced by using dust-free paper as such a release sheet, which led to the invention.

In other words, in one embodiment, the adhesive sheet for a workpiece according to the present invention comprises an adhesive layer configured to be attached to a workpiece for an electronic device, and a release sheet disposed on the adhesive layer and capable of being peeled off from the adhesive layer. The release sheet comprises dust-free paper.

The present invention provides a technology that can improve carbon dioxide emissions from work adhesive sheets that are attached to electronic device workpieces.

FIG. 1 is a schematic cross-sectional view showing an adhesive sheet according to an embodiment. FIG. 2 is a schematic diagram showing an example of a method of using the adhesive sheet.

The following describes the adhesive sheet for workpieces according to an embodiment of the present invention.

The adhesive sheet for workpieces according to this embodiment is an adhesive sheet that is attached to workpieces for electronic devices when used. Details will be described later, but a workpiece for an electronic device refers to a workpiece used in the manufacture of an electronic device. In other words, a workpiece for an electronic device is processed to manufacture an electronic device. The adhesive sheet according to this embodiment is attached to a workpiece for an electronic device when used at any stage in the manufacturing process of the electronic device.

In the following description, the "adhesive sheet for work" may simply be referred to as the "adhesive sheet." Also, the "work for electronic device" may simply be referred to as the "work."

(Summary)
Fig. 1 is a schematic cross-sectional view showing an adhesive sheet 1 according to this embodiment. As shown in Fig. 1, the adhesive sheet 1 has an adhesive layer 2, a release sheet 3, and a support film 4. These are laminated in the following order: support film 4, adhesive layer 2, and release sheet 3.

The adhesive layer 2 is configured to be attached to the workpiece. That is, the adhesive layer 2 is attached to the workpiece at some stage in the manufacturing process of the electronic device.

The release sheet 3 is placed on the adhesive layer 2 for the purpose of protecting the adhesive layer 2. The release sheet 3 can be peeled off from the adhesive layer 2. There is no particular limitation on the timing at which the release sheet 3 is peeled off. The release sheet 3 is peeled off from the adhesive layer 2 at any time during the manufacturing process of the electronic device.

The support film 4 is provided to support the adhesive layer 2. The support film 4 is not an essential component. For example, if the adhesive layer 2 is self-supporting, the support film 4 may be omitted. The support film 4 may be laminated inseparably with the adhesive layer 2, or if the adhesive sheet is an adhesive sheet for joining parts or a film for covering the back surface of a workpiece, as described below, the support film 4 may be separable from the adhesive layer 2 and peeled off from the adhesive layer 2 at any time during the manufacturing process of the electronic device. In addition, the core layer 6 and the second adhesive layer 2' may be laminated between the adhesive layer 2 and the support film 4, in that order from the adhesive layer 2 side, so that the adhesive sheet 1 has a so-called double-sided adhesive sheet configuration. In this case, the support film 4 laminated with the second adhesive layer 2' is separable from the second adhesive layer 2' and peeled off from the adhesive layer 2 at any time during the manufacturing process of the electronic device.

Here, in this embodiment, the release sheet 3 has dust-free paper. More specifically, the release sheet 3 is made of dust-free paper. Dust-free paper emits less carbon dioxide than the resin films that are commonly used as the release sheet 3. For example, dust-free paper can be achieved with approximately one-quarter the amount of carbon dioxide emissions compared to polyethylene terephthalate film. According to this embodiment, because dust-free paper is used as the release sheet 3, the carbon dioxide emissions of the entire adhesive sheet 1 can be reduced.

When the support film 4 is laminated so as not to be separated from the adhesive layer 2, it is realized by, for example, a resin film (such as a PET film). When the support film 4 can be separated from the adhesive layer 2, the support film 4 may be an adhesive layer supporting adhesive sheet 4' having an adhesive layer for holding the adhesive layer 2, or a second release sheet 3' having the same function as the release sheet 3. When the adhesive sheet 1 has a core material layer 6 and a second adhesive layer 2' and has a so-called double-sided adhesive sheet configuration, the support film 4 is usually a second release sheet 3'. When the adhesive sheet 1 has a second release sheet 3', the second release sheet 3' does not need to have dust-free paper, but from the viewpoint of reducing carbon dioxide emissions in the entire adhesive sheet 1, it is preferable that the second release sheet 3' has dust-free paper like the release sheet 3. In other words, it is preferable that both the release sheet 3 and the second release sheet 3' have dust-free paper.

In addition, adhesive sheets that are applied to workpieces for electronic devices must generate minimal amounts of foreign matter (dust, dirt). By using dust-free paper, such requirements can be met.

The above is an overview of the adhesive sheet 1 according to this embodiment. Next, the details of the adhesive sheet 1 will be described.

(How to use the adhesive sheet)
First, a method of using the adhesive sheet will be described. The method of using the adhesive sheet according to this embodiment includes an exposing step of exposing at least one surface of the adhesive layer as an exposed surface, an attaching step of attaching a workpiece to the exposed surface of the adhesive layer, and a peeling step of peeling the release sheet from the adhesive layer. As described above, the peeling step may be performed at any stage. For example, the exposing step may be realized by the peeling step. That is, at least one surface of the adhesive layer may be exposed by peeling the release sheet from the adhesive layer. On the other hand, the peeling step may be performed after the attaching step. That is, the adhesive layer may be attached to the workpiece with the release sheet, and then the release sheet may be peeled off.

Below, a preferred example of how to use the adhesive sheet is described with reference to Figure 2.

FIG. 2 is a schematic diagram showing an example of a method of using the adhesive sheet 1. As shown in FIG. 2(a), first, the release sheet 3 is peeled off from the adhesive layer 2. This exposes one side of the adhesive layer 2. Next, the workpiece 5 is attached to the exposed surface of the adhesive layer 2. After that, the necessary processing is performed. The above is an example of a method of using the adhesive sheet 1. The adhesive layer 2 may be finally removed from the workpiece 5. On the other hand, the adhesive layer 2 may remain attached to the workpiece 5 as part of the final product. In any case, as in the example shown in FIG. 2, it is preferable to peel off the release sheet 3 before attaching the workpiece 5. Although the generation of foreign matter can be suppressed by using dust-free paper, it is difficult to completely eliminate the generation of foreign matter. If the release sheet 3 is peeled off before attaching the workpiece 5, foreign matter originating from the dust-free paper is less likely to adhere to the workpiece 5.

If the adhesive sheet 1 has the second release sheet 3', the release sheet 3 is peeled off before the workpiece 5 is attached, and the second release sheet 3' is peeled off after the workpiece 5 is attached, so that the adhesive sheet 1 can be easily handled from the time the release sheet 3 is peeled off until the workpiece 5 is attached to the adhesive layer 2. If the second release sheet 3' does not have dust-free paper, the above-mentioned effect that foreign matter originating from the dust-free paper is less likely to adhere to the workpiece 5 can be obtained. On the other hand, if the second release sheet 3' is peeled off before the workpiece 5 is attached, and the release sheet 3 is peeled off after the workpiece 5 is attached, the above-mentioned effect that foreign matter originating from the dust-free paper is less likely to adhere to the workpiece 5 cannot be obtained. However, there is an advantage in that both the release sheet 3 and the second release sheet 3' have dust-free paper, which makes it possible to further reduce carbon dioxide emissions from the adhesive sheet 1 as a whole. In this case, the exposure process (the process of peeling off the second release sheet 3' instead of the release sheet 3 to expose one side of the adhesive layer 2 as an exposed surface for attachment to the workpiece 5) and the peeling process (the process of peeling off the release sheet 3) are carried out separately.

(Workpieces for electronic devices)
Next, the workpiece for electronic devices will be described. As described above, the workpiece for electronic devices is a workpiece for manufacturing electronic devices. Examples of the workpiece for electronic devices include circuit boards and workpieces for semiconductor devices. Examples of the workpiece for semiconductor devices include semiconductor wafers, semiconductor chips, semiconductor packages, and chip encapsulants produced by a fan-out packaging process. Examples of the workpiece for electronic devices include workpieces processed by a processing method similar to the manufacturing process of semiconductor devices (e.g., lithography processing, etc.). For example, it is also possible to use a workpiece for MEMS and a wafer for forming LED chips (sapphire wafer, etc.) as the workpiece for electronic devices. Among these, a workpiece for semiconductor devices or a workpiece processed by a processing method similar to the manufacturing process of semiconductor devices is preferable.

The thickness of the workpiece for electronic devices is not particularly limited, but in recent years, as electronic devices have become thinner, thinner workpieces for electronic devices have been adopted than before, for example, about 5 to 100 μm, and preferably about 10 to 70 μm. If the adhesive sheet is a backgrind sheet described below, it is preferable that the thickness of the back surface of the workpiece after grinding is within the above range.

(Application)
The adhesive sheet according to the present embodiment may be used by being attached to a workpiece during the manufacture of an electronic device, and its specific use is not particularly limited. For example, the adhesive sheet may be at least one of an adhesive sheet for processing a workpiece, an adhesive sheet for supporting a workpiece, an adhesive sheet for joining components, a film for covering the back surface of a workpiece, a film for reinforcing bumps, and an interlayer insulating material for forming a build-up layer.

The "adhesive sheet for workpiece processing" is an adhesive sheet that is attached to a workpiece when the workpiece is processed. Examples of adhesive sheets for workpiece processing include dicing sheets, back grinding sheets, and sheets for chip sealing processes.

A dicing sheet is a sheet for supporting a workpiece such as a semiconductor wafer when the workpiece is diced. When used as a dicing sheet, the adhesive layer is exposed and then the workpiece is attached to the exposed surface. The workpiece is then diced, thereby forming multiple chips. After dicing, each chip is picked up from the adhesive layer. The workpiece may be diced using mechanical means such as a blade, or the workpiece may be cut using means such as a laser or plasma.

The backgrind sheet is a sheet used to protect the circuit-forming surface of a workpiece (such as a semiconductor wafer) when grinding the back surface (the surface opposite to the circuit-forming surface) of the workpiece having a circuit-forming surface. When used as a backgrind sheet, the adhesive layer is exposed, and then the circuit-forming surface of the workpiece is attached to the exposed surface. The back surface of the workpiece is then ground. If necessary, the adhesive layer is then removed from the workpiece. The backgrind sheet may be used in a method of singulating a workpiece (a so-called pre-dicing method) in which the workpiece is a semiconductor wafer and the semiconductor wafer is singulated into multiple semiconductor chips by grinding along planned division lines that are composed of grooves pre-formed on the circuit-forming surface of the semiconductor wafer or modified regions pre-formed inside the semiconductor wafer. The pre-dicing method is a method suitable for obtaining thin semiconductor chips, and the resulting semiconductor chips tend to be thin.

The chip sealing process sheet is a sheet for obtaining a sealed body in which multiple chips are sealed by fixing multiple chips, which are workpieces, in a predetermined arrangement on the adhesive layer of an adhesive sheet, covering the multiple chips with a sealing material, and hardening the sealing material. The adhesive sheet, which is a chip sealing sheet, may have a configuration of a double-sided adhesive sheet having a core material layer and a second adhesive layer, and the second adhesive layer may be attached to a support substrate such as a glass plate, and the multiple chips, which are the workpieces, may be fixed to the support substrate via the adhesive sheet. In order to facilitate peeling of the workpiece or support substrate from the adhesive sheet, at least one of the adhesive layer, the core material layer, and the second adhesive layer may contain thermally expandable particles, and the adhesive strength of the adhesive sheet to the workpiece or support substrate may be reduced by heating.

The "adhesive sheet for supporting a workpiece" is an adhesive sheet used to support a workpiece (such as a wafer or chip) during temporary storage or transportation. When used as an adhesive sheet for supporting a workpiece, the adhesive layer is exposed and the workpiece is attached, after which the workpiece is temporarily stored or transported. In addition, when the workpiece is multiple chips, an expansion process may be performed in which the spacing between the multiple chips is expanded by stretching the adhesive sheet for supporting a workpiece while the multiple chips are supported in a predetermined arrangement on the adhesive sheet for supporting a workpiece. The adhesive layer is then removed from the workpiece as necessary.

In the above-mentioned adhesive sheets (adhesive sheets for workpiece processing and adhesive sheets for workpiece support), a pressure-sensitive adhesive layer is usually used as the adhesive layer. The adhesive layer is usually supported by a support film. However, as mentioned above, if the adhesive layer is self-supporting, the support film may be omitted.

An "adhesive sheet for joining parts" is a sheet used to join multiple parts. It is preferable that the adhesive sheet for joining parts is a curable adhesive sheet that has a curing property, so that a strong bond can be obtained by temporarily bonding the parts together with the curable adhesive sheet and then curing it. Below, the adhesive sheet for joining parts is explained using a curable adhesive sheet as an example. A curable adhesive sheet usually has a support film in addition to an adhesive layer. The adhesive layer is separable from the support film.

An example of a curable adhesive sheet is a die attachment film. For example, when used as a die attachment film, at least one side of the adhesive layer is first exposed. Specifically, one side of the adhesive layer is exposed by peeling off one of the release sheet and the support film. Next, a workpiece (such as a semiconductor chip or a semiconductor wafer) is attached to the exposed side of the adhesive layer. After that, the other side of the adhesive layer is exposed. That is, the other side of the support film and the release sheet is peeled off to expose the other side. Next, the other side of the adhesive layer is attached to a substrate. The adhesive layer is then cured. This allows the workpiece to be bonded to the substrate via the adhesive layer.

Another example of a curable adhesive sheet is a non-conductive adhesive film (NCF) that is interposed between the bump-forming surface of a face-down type semiconductor chip and a substrate or the like to bond them together. For example, when used as an NCF, at least one surface of the adhesive layer is first exposed. Specifically, one of the release sheet and the support film is peeled off to expose one surface of the adhesive layer. Next, the bump-forming surface of the face-down type semiconductor chip wafer, which is the workpiece, is attached to the exposed surface of the adhesive layer. The attachment may be performed using a vacuum laminator or the like. Then, the other surface of the adhesive layer is exposed. That is, the other surface is exposed by peeling off the other of the support film and the release sheet. Next, the laminate of the adhesive sheet and the semiconductor wafer is diced to obtain a semiconductor chip with an NCF, and the other surface of the adhesive layer is attached to the substrate. The adhesive layer is then cured. This allows the workpiece to be bonded to the substrate via the adhesive layer.

Thermal conductive material-containing sintering film can also be used as a component bonding sheet. The adhesive layer of the thermal conductive material-containing sintering film contains a thermal conductive material such as metal particles or boron nitride, preferably in the form of particles dispersed in the resin. Thermal conductive material-containing sintering film is usually used to fix power semiconductors. Specifically, one side of the adhesive layer is exposed by peeling off one of the release sheet and the support film. Then, a work (power semiconductor chip, power semiconductor wafer, etc.) is attached to the exposed side of the adhesive layer. Then, the other side of the adhesive layer is exposed. That is, the other side of the support film and the release sheet is peeled off to expose the other side. Then, the other side of the adhesive layer is attached to another member such as a substrate. Then, the adhesive layer is sintered, and the work and the other member are bonded by the layer made of a sintered body of the thermal conductive material. The layer made of a sintered body of the thermal conductive material functions as a thermal conduction path for the heat generated from the power semiconductor.

A "film for covering the back surface of a workpiece" is a film for providing a covering layer of an adhesive layer on the back surface of a workpiece (such as a semiconductor wafer or semiconductor chip) that has a circuit-forming surface. Therefore, it is only attached to the workpiece as an adherend, and is not used to join the workpiece to other components. The back surface of the workpiece referred to here is the surface facing the opposite side to the circuit-forming surface. Examples of films for covering the back surface of a workpiece include protective sheets (called chip back surface protective tape) that are attached to the back surface of face-down type semiconductor chips, and sheets (called anti-warping sheets) that are attached to the back surface of an encapsulant that contains a semiconductor chip to prevent warping. The covering layer may be provided directly on the back surface of the workpiece, or may be provided via another layer.

For example, when used as a chip backside protection tape, after the adhesive layer is exposed, the backside of a semiconductor wafer is attached to the adhesive layer as a workpiece. The adhesive layer is then cured to form a coating layer. The semiconductor wafer is then diced using a dicing sheet as necessary, and divided into multiple semiconductor chips. This results in semiconductor chips whose backsides are protected by a coating layer. Each semiconductor chip is then picked up and mounted face-down on another substrate. If a support film is present on the adhesive sheet, the support film is removed at an appropriate time, for example after curing. The surface of the adhesive layer opposite the workpiece is left open, and does not adhere to other substrates.

For example, when used as an anti-warping sheet, after the adhesive layer is exposed, the back surface of a semiconductor chip is attached to the exposed surface as a workpiece. Next, an encapsulating resin is supplied onto the adhesive layer so as to encapsulate the semiconductor chip. Next, the adhesive layer and encapsulating resin are cured. This results in an encapsulated body with reduced warping.

The "bump reinforcing film" is a film for forming a reinforcing film on the bump-forming surface of a semiconductor wafer by attaching a curable reinforcing film-forming film to the bump-forming surface and curing the film for the purpose of reinforcing the bumps and the bumps. For example, when used as a bump reinforcing film, first, at least one side of the adhesive layer is exposed. Specifically, one side of the adhesive layer is exposed by peeling off one of the release sheet and the support film. Next, the bump-forming surface of the workpiece, a semiconductor wafer on which bumps are formed, is attached to the exposed surface of the adhesive layer. The attachment may be performed using a vacuum laminator or the like. After that, the other side of the adhesive layer is exposed. That is, the other side is exposed by peeling off the other of the support film and the release sheet. Next, the adhesive layer is cured. This allows a reinforcing film to be formed on the bump-forming surface of the workpiece.

The "interlayer insulating material for forming a build-up layer" is a film-like material used to form one build-up layer that constitutes a multilayer wiring board. For example, when used as an interlayer insulating material for forming a build-up layer, first, at least one surface of the adhesive layer is exposed. Specifically, one of the release sheet and the support film is peeled off to expose one surface of the adhesive layer. Then, a circuit board, which is a workpiece, is attached to the exposed surface of the adhesive layer. At this time, a lamination process in which heat and pressure are applied to the adhesive layer may be performed through the other of the release sheet and support film that have not yet been peeled off. Then, the other surface of the adhesive layer is exposed. That is, the other surface is exposed by peeling off the other of the support film and the release sheet. Next, the adhesive layer is cured. As a result, a build-up layer is formed on the circuit board. The formed build-up layer may be subjected to a drilling process in which holes are drilled in the build-up layer, a roughening process in which the build-up layer is roughened, a plating process in which a conductor layer is formed by plating on the roughened surface of the build-up layer, and a circuit formation process in which a circuit is formed on the conductor layer.

Preferably, the adhesive sheet is at least one selected from the group consisting of a dicing sheet, a backgrind sheet, a die attachment film, a chip backside protective tape, and an anti-warping sheet. Note that these uses may be combined. For example, the adhesive sheet may have the functions of both a die attachment film and a dicing sheet.

In the case of adhesive sheets for workpiece processing and adhesive sheets for workpiece support, the adhesive layer 2 is ultimately removed from the workpiece 5, whereas in adhesive sheets for component bonding, films for covering the back surface of a workpiece, films for reinforcing bumps, and interlayer insulating materials for forming build-up boards, the adhesive layer 2 remains attached to the workpiece 5 as part of the final product. Among these, adhesive sheets for workpiece processing and adhesive sheets for workpiece support, from which the adhesive layer 2 is ultimately removed from the workpiece 5, are used in large quantities as indirect materials in the manufacturing process of electronic devices, and there is a strong demand for reducing carbon dioxide emissions.

(Form of adhesive sheet)
Next, the form in which the adhesive sheet is provided will be described. The form of the adhesive sheet is not particularly limited. For example, the adhesive sheet may be provided in a form in which a long sheet is wound around a core material (hereinafter, sometimes referred to as a roll form). Alternatively, the adhesive sheet may be provided in a form in which a plurality of individual sheets are stacked (hereinafter, sometimes referred to as an individual sheet stack form).

(Adhesive Layer)
Next, the adhesive layer will be described. For example, a resin layer is used as the adhesive layer. The specific structure of the adhesive layer is appropriately selected depending on the application. The adhesive layer 2 may be composed of a single layer, or may have a structure in which multiple layers are laminated.

In a preferred embodiment, the adhesive layer is photocurable.

For example, when used in applications where a workpiece is peeled off from the adhesive layer, photocuring can make it easier to peel off the workpiece. For example, when the adhesive sheet is a pressure-sensitive adhesive sheet such as a dicing sheet or a backgrind sheet, the adhesive layer is first attached to the workpiece. Then, after the workpiece is processed, the adhesive layer is irradiated with light and a curing reaction is carried out. The adhesive strength between the adhesive layer and the workpiece is reduced by the curing. Therefore, the workpiece can be easily peeled off from the adhesive layer. In order to impart photocurability to the adhesive layer, it is usually preferable that the adhesive layer contains a photocurable compound. In addition, in this case, it is preferable that the adhesive layer contains a photopolymerization initiator. Examples of photocurable compounds include compounds having a group containing an unsaturated carbon bond, such as a methacryloyl group or an acryloyl group, and such compounds are preferably used in combination with a photoradical polymerization initiator. In addition, an adhesive layer using a compound having a cyclic ether group, such as an epoxy resin, and a photocationic polymerization initiator may be used as a photocurable adhesive layer. From the viewpoint of quickly progressing the photocuring reaction, it is preferable that the adhesive layer contains a compound having a group containing an unsaturated carbon bond and a photoradical polymerization initiator. Examples of compounds having a group containing an unsaturated carbon bond include compounds having two or more methacryloyl groups or acryloyl groups in one molecule, such as tricyclodecane dimethanol diacrylate, and examples of photoradical polymerization initiators include intramolecular cleavage type radical polymerization initiators such as α-hydroxyalkylphenone.

The adhesive layer may also contain heat-expanding particles to facilitate peeling. If heat-expanding particles are included, the adhesive strength between the adhesive layer and the object to be peeled off (the workpiece or the supporting substrate) can be reduced by heating, making peeling easier.

Alternatively, if the adhesive sheet is a curable adhesive sheet such as a die attachment film, and it is expected that the support film will be peeled off from the adhesive layer, the photocuring reaction can make it easier to peel the support film off from the adhesive layer. Note that if the adhesive layer of the die attachment film is photocurable, the adhesive layer generally also contains a thermosetting compound in order to obtain adhesive strength after die bonding.

Alternatively, if the adhesive sheet is a film for covering the back surface of a workpiece, after attaching the adhesive sheet to the workpiece, it is possible to obtain a hard covering layer by irradiating it with light to harden the adhesive layer.

As described above, the adhesive layer may be configured to have photocurability depending on the application. However, when the adhesive layer has photocurability, the adhesive layer needs to be light-shielded during storage to prevent unintended photocuring reactions from proceeding. In this regard, according to the present embodiment, dust-free paper is used as the release sheet. Dust-free paper has light-shielding properties. Therefore, the adhesive sheet according to the present embodiment is also preferable from the viewpoint of light-shielding properties. Whether the adhesive sheet is in the form of a roll or a laminated sheet, the dust-free paper in the outermost layer suppresses the incidence of light into the adhesive layer. For example, according to the present embodiment, the adhesive sheet can be stored without using a light-shielding packaging material. Alternatively, even if a light-shielding packaging material is used, it may take time from unpacking to use. According to the present embodiment, exposure to light between unpacking and use can be prevented, and unintended curing can be more reliably prevented. When the adhesive layer contains a compound having a group containing an unsaturated carbon bond and a photoradical polymerization initiator, the photocuring reaction is likely to proceed, so there is a high need to prevent unintended photocuring reactions from proceeding.

The thickness of the adhesive layer is set according to the application and is not particularly limited. For example, the thickness of the adhesive layer is 1 μm to 1000 μm.
When used as a dicing sheet, the adhesive layer has a thickness of, for example, 3 to 50 μm.
When used as a backgrind sheet, the thickness of the adhesive layer is, for example, 3 to 500 μm. When the backgrind sheet is attached to the bump-formed surface of a workpiece on which bumps are formed, a third adhesive layer 2" for burying the bumps may be formed between the adhesive layer 2 and the support film 4. In this case, it is preferable that the total thickness of the adhesive layer 2 and the third adhesive layer 2" is within the above range.
When used as a sheet for chip sealing process, the thickness of the adhesive layer is, for example, 2 to 300 μm. When the sheet for chip sealing process has a configuration of a double-sided adhesive sheet having a core layer 6 and a second adhesive layer 3′, the thickness of the second adhesive layer 3′ is, for example, 2 to 300 μm.
When used as an adhesive sheet for supporting a workpiece during temporary storage or transport of the workpiece, the thickness of the adhesive layer is, for example, 3 to 50 μm.
When used as a die attachment film, the adhesive layer has a thickness of, for example, 3 to 200 μm.
When used as an NCF, the thickness of the adhesive layer is, for example, 5 to 150 μm.
When used as a thermally conductive material-containing film for firing, the thickness of the adhesive layer is, for example, 30 to 200 μm.
When used as a protective sheet (chip back surface protective tape) to be attached to the back surface of a face-down type semiconductor chip, the adhesive layer has a thickness of, for example, 5 to 200 μm.
When used as a sheet (called an anti-warping sheet) to be attached to the back surface of an encapsulant containing a semiconductor chip to prevent warping, the adhesive layer has a thickness of, for example, 5 to 200 μm.
When used as a bump reinforcing film, the adhesive layer has a thickness of, for example, 1 to 200 μm.
When used as an interlayer insulating material for forming a build-up layer, the adhesive layer has a thickness of, for example, 3 to 100 μm.

(dust-free paper)
Next, the dust-free paper will be described. Dust-free paper is paper that generates less dust than regular paper.

For example, dust-free paper that generates 2,000 or less floating dust particles of 0.3 μm or more per cubic foot in any of the dust generation tests according to the following rubbing, crumpling, and tearing tests can be used.
Rubbing: Prepare two A5 size test pieces (rectangles with long sides of 210 mm and short sides of 148 mm), overlap the front and back of the test paper, and rub them together for 200 seconds, three times every 10 seconds.
Kneading: An A5 size (rectangle with long sides of 210 mm and short sides of 148 mm) test piece is kneaded by hand for 200 seconds at a rate of once every 15 seconds.
- Tear and knead: An A5 size (rectangle with long sides of 210 mm and short sides of 148 mm) test piece is torn at four points once every 5 seconds, and then kneaded for 180 seconds in the same manner as in the kneading test.
The test is carried out in a clean bench, and the number of floating dust particles is measured using a light scattering particle counter. For example, a particle counter manufactured by Rion Co., Ltd. may be used as such a particle counter. The number of floating dust particles of 0.3 μm or more generated in the above dust generation test is preferably 1,000 or less particles per cubic foot, and more preferably 300 or less particles per cubic foot.

As the material for the dust-free paper, paper having a plant fiber layer and impregnated with an impregnating resin can be used. The impregnation with the impregnating resin prevents the fibers from scattering, realizing the function of the dust-free paper. Furthermore, dust-free paper using plant fibers is more suitable because it produces particularly low carbon dioxide emissions. Examples of plant fibers include pulp, and such plant fibers are generally composed of polysaccharides such as cellulose and have a structure rich in hydrophilic groups such as hydroxyl groups, so that they have relatively low electrical resistance and can prevent the release sheet from becoming charged. As the impregnating resin, a water-based binder that has the potential to further reduce carbon dioxide emissions is preferable, and an example of such a water-based binder is a combination of an acrylic resin and an ethylene vinyl acetate copolymer.

As mentioned above, the use of dust-free paper can reduce the carbon dioxide emissions of the entire adhesive sheet. In addition, dust-free paper is also preferable in terms of preventing blocking and reducing the amount of static electricity. For example, when the adhesive sheet is provided in a rolled form, the release sheet comes into contact with the member of the adjacent layer (for example, the support film, or, if there is no support film, the adhesive layer of the adjacent layer) on the side opposite the adhesive layer. Here, when in use, the release sheet is unwound while being peeled off from the member of the adjacent layer. At this time, blocking and peeling static electricity may occur. However, dust-free paper has a moderate unevenness on its surface. Therefore, the contact area between the dust-free paper and the member of the adjacent layer that is to be peeled off is relatively small. As a result, blocking is prevented. In addition, peeling static electricity during unwinding is also suppressed. The arithmetic mean roughness Ra of the surface of dust-free paper is usually about 0.5 to 5 μm.

In addition, when the dust-free paper has a plant fiber layer impregnated with an impregnating resin, it is preferable that the impregnating resin contains an antistatic agent. If an antistatic agent is contained, peeling static electricity can be further suppressed. If a resin film is used as the release sheet, it is necessary to form an antistatic coating layer on the resin film to impart antistatic functionality. In contrast, according to this embodiment, by adding an antistatic agent to the impregnating resin, it is possible to easily impart antistatic functionality to the dust-free paper used as a release sheet.

It is preferable that a release layer is provided as the outermost layer on the release surface (the surface in contact with the adhesive layer) of the dust-free paper. The release layer allows the release sheet to be easily peeled off from the adhesive layer laminated on the release sheet. The release agent may be at least one selected from the group consisting of silicone-based release agents, alkyd-based release agents, polyolefin-based release agents, and urethane-based release agents. The thickness of the release layer is usually about 0.01 μm to 1 μm, and preferably 0.01 μm to 0.2 μm.

It is also preferable that a smoothing layer is provided on the release surface of the dust-free paper. As described above, the surface of dust-free paper has a moderate amount of unevenness. However, if the release surface has unevenness, the unevenness will be transferred to the adhesive layer, and the smoothness of the adhesive layer surface will be lost. Therefore, in applications where a uniform thickness of the adhesive layer is required due to reasons such as the thinness of the workpiece (for example, applications in which it is attached to a workpiece for a semiconductor device or a MEMS workpiece), it is preferable that a smoothing layer is provided on the release surface.

The smoothing layer can be formed, for example, by coating the surface of the dust-free paper with a resin. The resin to be coated may contain, for example, an energy ray-curable compound, and may be cured by irradiating energy rays after application. Examples of energy rays include electron beams and ultraviolet rays. Alternatively, the smoothing layer can be realized by laminating a resin film (for example, a thin polyethylene film with a thickness of 5 μm or less) on the surface of the dust-free paper. The surface of the smoothing layer usually has an arithmetic mean roughness Ra of less than 500 nm. The arithmetic mean roughness Ra of the surface of the smoothing layer is preferably 3 to 300 nm, and more preferably 5 to 200 nm. Furthermore, when the release surface of the dust-free paper has both a smoothing layer and a release layer, the arithmetic mean roughness Ra of the surface of the release layer is preferably 1 to 200 nm, and more preferably 3 to 100 nm.

In addition, when the adhesive sheet is used for applications such as an interlayer insulating material for forming build-up layers, the adhesive layer may contain high-boiling point solvents such as naphtha. Therefore, to prevent the dust-free paper from absorbing such solvents and changing its quality, a solvent-resistant layer may be provided on the release surface of the dust-free paper. The solvent-resistant layer can be provided by coating the surface of the dust-free paper with a resin, in the same way as the smoothing layer, and the smoothing layer may also serve as the solvent-resistant layer.

The thickness of the dust-free paper is not particularly limited, but is, for example, 30 to 300 μm, and preferably 50 to 200 μm.

(Production method)
The method for producing the adhesive sheet is not particularly limited, but a preferred example of the method for producing the adhesive sheet will be described below.

First, dust-free paper is prepared as a release sheet. Then, a composition in which the release agent is diluted with a solvent is applied onto the prepared dust-free paper, and the composition is dried by heating to volatilize the solvent, thereby obtaining a release layer. Furthermore, an adhesive composition containing a substance that will be a precursor of the adhesive layer is applied onto the release layer. After application, the adhesive composition is dried by heating. For example, the composition in which the release agent is diluted with a solvent or the adhesive composition is dried in an oven. This forms an adhesive layer. Thereafter, a support film is attached to the adhesive layer as necessary, and an adhesive sheet according to this embodiment is obtained.

The above-mentioned manufacturing method is preferable in terms of productivity, etc. If a resin film is used as the release sheet, the resin film may shrink due to heat when the adhesive composition is heated and dried. On the other hand, dust-free paper generally has higher heat resistance than resin film. For example, when dust-free paper having a plant fiber layer such as pulp is used as the release sheet, dust-free paper with high heat resistance is obtained. Therefore, by using dust-free paper with high heat resistance as the release sheet, it is possible to prevent the release sheet from shrinking when the adhesive composition is heated and dried. This makes it possible to suppress wrinkles and make it easier to obtain an adhesive sheet of the desired width. In addition, it becomes possible to dry the adhesive composition at a higher temperature, which improves the productivity of the adhesive sheet.

(Additional Note)
The present invention has been described above using the embodiments. Representative configurations of the present invention will be summarized below as supplementary notes.

(Appendix 1)
An adhesive sheet for a workpiece comprising an adhesive layer configured to be affixed to a workpiece for an electronic device, and a release sheet disposed on the adhesive layer and removable from the adhesive layer, the release sheet having dust-free paper.
(Appendix 2)
The adhesive sheet for a workpiece according to claim 1, which is at least one selected from the group consisting of an adhesive sheet for joining components, a film for covering the rear surface of a workpiece, a film for reinforcing bumps, and an interlayer insulating material for forming a build-up layer;
Adhesive sheet for work.
(Appendix 3)
3. An adhesive sheet for a workpiece according to claim 1 or 2, wherein the adhesive layer has photocuring properties.
(Appendix 4)
An adhesive sheet for a workpiece according to any one of claims 1 to 3, wherein the dust-free paper has a release surface facing the adhesive layer and has a smoothing layer provided on the release surface.
(Appendix 5)
5. An adhesive sheet for a workpiece according to any one of claims 1 to 4, wherein the dust-free paper has a plant fiber layer impregnated with a resin.
(Appendix 6)
6. An adhesive sheet for a workpiece according to claim 5, wherein the resin contains an antistatic agent.
(Appendix 7)
3. An adhesive sheet for a workpiece according to claim 1 or 2, wherein the release sheet is configured to be peeled off before the adhesive layer is attached to the workpiece for an electronic device.
(Appendix 8)
A method for producing an adhesive sheet for a workpiece according to any one of Appendices 1 to 7, comprising the steps of: preparing dust-free paper; applying an adhesive composition containing a substance that is a precursor of an adhesive layer onto the dust-free paper; and, after the application step, drying the adhesive composition by heating to form an adhesive layer.

REFERENCE SIGNS LIST 1 Work adhesive sheet 2 Adhesive layer 3 Release sheet 4 Support film 5 Work for electronic device

Claims (8)

An adhesive layer configured to be attached to a workpiece for an electronic device;
a release sheet disposed on the adhesive layer and releasable from the adhesive layer;
Equipped with
The release sheet comprises dust-free paper.
Adhesive sheet for work. The adhesive sheet for a workpiece according to claim 1,
At least one selected from the group consisting of an adhesive sheet for processing a workpiece, an adhesive sheet for supporting a workpiece, an adhesive sheet for joining components, a film for covering the back surface of a workpiece, a film for reinforcing bumps, and an interlayer insulating material for forming a build-up layer;
Adhesive sheet for work. The adhesive sheet for workpieces according to claim 1 or 2,
The adhesive layer has photocuring properties.
Adhesive sheet for work. The adhesive sheet for workpieces according to claim 1 or 2,
The dust-free paper has a release surface facing the adhesive layer, and further has a smoothing layer provided on the release surface.
Adhesive sheet for work. The adhesive sheet for workpieces according to claim 1 or 2,
The dust-free paper has a plant fiber layer impregnated with a resin.
Adhesive sheet for work. The adhesive sheet for a workpiece according to claim 5,
The resin contains an antistatic agent.
Adhesive sheet for work. The adhesive sheet for workpieces according to claim 1 or 2,
The release sheet is configured to be peeled off before the adhesive layer is attached to the electronic device workpiece.
Adhesive sheet for work. A method for producing the adhesive sheet for workpieces according to claim 1 or 2, comprising the steps of:
preparing the dust-free paper;
applying an adhesive composition onto the dust-free paper, the adhesive composition including a precursor material for the adhesive layer;
a step of drying the adhesive composition by heating after the applying step to form the adhesive layer;
Equipped with
Manufacturing method.

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