JP2024127113A - Sheet for forming resin film and method for processing workpiece - Google Patents

Abstract

[Problem] To prevent identification errors when confirming that peeling has been performed reliably after peeling a heavy release film 12 from a sheet for resin film formation 10, which is a laminated sheet of a heavy release film 12/resin film forming film 11/light release film 13.
The sheet for resin film formation 10 of the present invention is
A resin film-forming film 11 for forming a resin film;
A heavy-surface release film 12 provided on one surface of the resin film-forming film;
A light-surface release film 13 is provided on the other surface of the resin film-forming film,
When the peel strength of the heavy-side release film 12 from the resin film-formed film 11 is F1 and the peel strength of the light-side release film 13 from the resin film-formed film 11 is F2, the relationship F1>F2 is satisfied,
The heavy-surface release film 12 satisfies either one or both of the following: a light transmittance of 80% or less at 555 nm, and a haze of 4% or more.
[Selected Figure] Figure 1

Description

The present invention relates to a sheet for forming a resin film and a method for processing a workpiece using the same. In particular, the present invention relates to a sheet for forming a resin film that is provided with a resin film-forming film that is suitably used for producing a protective film for protecting a workpiece such as a semiconductor wafer or a workpiece diced piece such as a semiconductor chip obtained by processing the workpiece, or an adhesive film for bonding the workpiece diced piece, and a method for processing a workpiece using the sheet for forming a resin film.

In recent years, semiconductor devices have been manufactured using a mounting method known as flip-chip bonding. In this mounting method, when mounting a semiconductor chip having a circuit surface on which convex electrodes such as bumps are formed, the circuit surface of the semiconductor chip is inverted (face down) and bonded to the chip mounting section. This results in a structure in which the back side of the semiconductor chip, on which no circuit is formed, is exposed.

For this reason, a hard resin film made of an organic material is often formed on the back side of the semiconductor chip to protect the semiconductor chip from shocks during transportation, etc. Such a resin film is called a protective film. The protective film is formed, for example, by attaching a protective film-forming film, which is an example of a resin film-forming film, to the back side of the semiconductor wafer, and then either cured or uncured.

In addition, a semiconductor chip may be attached to the circuit-forming surface of a substrate by a resin film applied to the back surface of the semiconductor chip. The resin film-forming film used to form and adhere such a resin film is called a die bonding film. The semiconductor chip is placed on the substrate via the die bonding film by die bonding. Then, if necessary, one or more additional semiconductor chips are stacked on this semiconductor chip, wire bonding is performed, and the whole is sealed with resin to produce a semiconductor package.

As shown in FIG. 1, Patent Document 1 discloses a three-layer structure protective film forming sheet 10 in which a protective film forming film 11 for generating a protective film is sandwiched between a first release film 12, which is a heavy release film, and a second release film 13, which is a light release film. The protective film forming film 11 is laminated so as to be peelable from the first release film 12 and the second release film 13. The protective film forming sheet of Patent Document 1 satisfies F1>F2, where F1 is the peeling force of the first release film 12 from the protective film forming film 11 and F2 is the peeling force of the second release film 13 from the protective film forming film 11. The protective film forming sheet 10 is usually long and is stored and transported in a roll.

In one mode of use of the resin film forming sheet 10, the light release film 13, which has a small peeling force, is peeled off, and the exposed resin film forming film 11 is attached to the workpiece. After that, a process may be performed in which unnecessary parts of the heavy release film 12 and the resin film forming film 11 are cut off to match the outer peripheral shape of the workpiece. Then, the heavy release film 12 is peeled off from the resin film forming film 11, and the resin film forming film 11 is hardened by a predetermined means to form a protective film, thereby obtaining a workpiece with a protective film. The workpiece with the protective film is diced into individual pieces, and individual workpieces with a protective film on the back surface are obtained. Note that the resin film forming film 11 may be hardened after dicing. For example, when a resin film is used as an adhesive film, it is diced in an unhardened state, and the resin film is hardened as necessary during adhesion.

JP 2022-32571 A

In the process of peeling the heavy release film 12 from the resin film-formed film 11, the peeling of the heavy release film 12 is confirmed by a sensor or visual inspection, but identification errors sometimes occur during this process. That is, even when the heavy release film 12 is not peeled, it is sometimes determined that it has been peeled and transferred to the next process.

The inventors conducted extensive research to prevent such identification errors and have completed this invention.

The aspects of the present invention that solve these problems are as follows.
(1) a resin film-forming film for forming a resin film;
A heavy-surface release film provided on one surface of the resin film-forming film;
A light-surface release film is provided on the other surface of the resin film-forming film,
When the peel strength of the heavy release film from the resin film-formed film is F1 and the peel strength of the light release film from the resin film-formed film is F2, the relationship F1>F2 is satisfied,
The heavy-surface release film is a sheet for resin film formation that satisfies either one or both of the following: a light transmittance of 80% or less at 555 nm; and a haze of 4% or more.
(2) The sheet for resin film formation according to (1), wherein at least one surface of the heavy release film is roughened.
(3) The sheet for resin film formation according to (1), wherein the heavy release film is colored.
(4) The sheet for resin film formation according to (1), wherein the average light reflectance of the contact surface of the resin film-forming film with the heavy release film in the range of 400 to 800 nm is 40% or less.
(5) The sheet for resin film formation according to (1), wherein the arithmetic mean height Sa of the contact surface of the heavy release film with the resin film-forming film is less than 0.03 μm.
(6) A step of peeling off the light-side release film of the sheet for resin film formation according to any one of (1) to (5) above, and attaching the exposed resin film-forming film to a workpiece;
A step of peeling off the heavy release film from the resin film-forming film attached to the workpiece; and
A method for processing a workpiece, comprising a step of confirming the release of a heavy release film.

According to the present invention, peeling of the heavy release film 12 can be confirmed with high accuracy.

FIG. 1 is a schematic cross-sectional view of a sheet for resin film formation according to this embodiment.

First, let us explain the main terms used in this specification.

The workpiece is a plate-like body to which the resin film-forming film according to this embodiment is attached and processed. Examples of the workpiece include wafers and panels. Specifically, examples include semiconductor wafers and semiconductor panels. Examples of the processed workpiece include chips obtained by dicing a wafer. Specifically, examples include semiconductor chips obtained by dicing a semiconductor wafer. In this case, the resin film is formed on the back side of the wafer and the chip.

The "front surface" of a workpiece such as a wafer refers to the surface on which circuits and convex electrodes such as bumps are formed, while the "back surface" refers to the surface on which circuits, electrodes (for example, convex electrodes such as bumps) are not formed.

The resin film is transferred to the workpiece and functions as a film that forms a protective film or adhesive film.

In this specification, for example, "(meth)acrylate" is used as a term to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

A release film is a film that supports a resin film-forming film so that it can be peeled off. The term film is not limited to a specific thickness, and is used to include a sheet. Heavy release films and light release films are distinguished by the peeling force from the resin film-forming film. If the peeling force of a heavy release film from a resin film-forming film is F1 and the peeling force of a light release film from a resin film-forming film is F2, then the relationship F1>F2 is satisfied.

The mass ratios in the descriptions of the resin film-forming film composition and release layer composition are based on the active ingredients (solid content), and do not include the solvent unless otherwise specified.

The present invention will be described below based on specific embodiments.

(1. Resin Film Forming Film)
1, the sheet for resin film formation 10 according to the present embodiment has a resin film-forming film 11 (more specifically, a protective film-forming film 11), a heavy release film 12 provided on one side of the resin film-forming film 11, and a light release film 13 provided on the other side. Such a sheet for resin film formation is usually a long sheet and is wound up in a roll.

Examples of resin films include protective films for protecting the workpiece or individual pieces of the workpiece, and adhesive films for adhering the individual pieces of the workpiece to a substrate, etc.

"Making a protective film" means making the resin film-forming film 11 into a state having sufficient properties to protect the workpiece or individual pieces of the workpiece. Specifically, when the resin film-forming film according to this embodiment is curable, "making a protective film" means making the uncured resin film-forming film into a cured product. In other words, the resin film-forming film that has been made into a protective film is a cured product of the resin film-forming film, and is different from the resin film-forming film.

After the workpiece is placed on the curable resin film-forming film, the resin film can be firmly adhered to the workpiece by curing the resin film-forming film, forming a durable protective film.

When the resin film-forming film 11 does not contain a curable component and is used as a protective film in an uncured state, the resin film-forming film according to this embodiment becomes a protective film when it is attached to a workpiece. In other words, the resin film may be the same as the resin film-forming film.

If high protective performance is not required, there is no need to harden the resin film-forming film, so the resin film-forming film may be non-hardening.

In this embodiment, the resin film-forming film is preferably curable. Therefore, the resin film is preferably a cured product. Examples of cured products include a thermoset product and an energy ray cured product. In this embodiment, it is more preferable that the resin film is a thermoset product.

It is also preferable that the resin film-forming film has adhesiveness at room temperature (23°C) or exhibits adhesiveness when heated. This allows the workpiece to be laminated to the resin film-forming film when it is overlaid on the film. This allows reliable positioning before the resin film-forming film is cured.

The resin film-forming film may be composed of one layer (single layer) or may be composed of two or more layers. When the resin film-forming film has multiple layers, these multiple layers may be the same or different from each other, and the combination of layers that make up these multiple layers is not particularly limited.

In this embodiment, the resin film-forming film is preferably one layer (single layer). If the resin film-forming film is composed of multiple layers, there is a risk of delamination occurring due to differences in thermal expansion and contraction between the layers during processes in which temperature changes occur (during reflow processing or when the device is used), but if it is a single layer, this risk can be reduced.

The thickness of the resin film-forming film is not particularly limited, but is preferably 100 μm or less, more preferably 70 μm or less, even more preferably 50 μm or less, and particularly preferably 40 μm or less. Also, it is preferably 5 μm or more, more preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 20 μm or more. When the thickness of the resin film-forming film is within the above range, the workability is excellent when cutting the resin film-forming sheet to fit the work shape, and the protective performance of the obtained resin film is good.

The thickness of the resin film-formed film means the thickness of the entire resin film-formed film. For example, the thickness of a resin film-formed film that is composed of multiple layers means the total thickness of all layers that make up the resin film-formed film.

The following describes the protective film formed by converting the resin film-forming film according to this embodiment into a protective film. A protective film-covered chip, which is an example of a workpiece with a protective film, has a protective film formed on the back side of the chip (the side on which no circuit is formed). A circuit and electrodes are formed on the front side of the chip, and the electrodes are formed so as to be electrically connected to the circuit. The protective film-covered chip is placed so that the side on which the electrodes are formed faces the chip-mounting substrate. Thereafter, the chip is mounted by electrically and mechanically joining the substrate via the electrodes through a specified heating process (reflow process). Examples of the electrodes include bumps and pillar electrodes.

(1.1 Peeling properties of resin film-forming film)
In this embodiment, when the peeling force of the heavy release film 12 from the resin film-forming film 11 is F1 and the peeling force of the light release film from the resin film-forming film is F2, F1>F2, preferably F1>1.2×F2, more preferably F1>1.5×F2, and more preferably F1>2×F2. When the peeling force F1 and the peeling force F2 satisfy the above relationship, the light release film is easily removed, the resin film-forming film is smoothly exposed, and the workpiece can be reliably attached to the resin film-forming film. The upper limit of the peeling force F1 is not particularly limited, but in relation to the peeling force F2, the relationship is preferably F1<10×F2, more preferably F1<7×F2, more preferably F1<5×F2, and particularly preferably F1<3.5×F2. The peeling force F1 and the peeling force F2 satisfy the above relationship. Furthermore, F2 is preferably 30 mN/100 mm or more, more preferably 40 mN/100 mm or more, and even more preferably 50 mN/100 mm or more.

The peeling force F1 is preferably 50 mN/100 mm or more, more preferably 70 mN/100 mm or more, even more preferably 90 mN/100 mm or more, even more preferably 110 mN/100 mm or more, and particularly preferably 130 mN/100 mm or more. By having F1 within the above range, unintentional peeling between the resin film-forming film 11 and the heavy-surface release film 12 can be suppressed.

(1.2 Resin Film-Forming Film Composition)
As long as the resin film-forming film has the above-mentioned physical properties, the composition of the resin film-forming film is not particularly limited. In this embodiment, the composition constituting the resin film-forming film (composition for resin film-forming film) is preferably a resin composition containing at least a polymer component (A), a curable component (B), and a filler (E). The polymer component is a component that can be considered to be formed by a polymerization reaction of a polymerizable compound. In addition, the curable component is a component that can undergo a curing (polymerization) reaction. In the present invention, the polymerization reaction also includes a polycondensation reaction.

In addition, the components contained in the polymer component may also be considered as curable components. In this embodiment, when the composition for a resin film-forming film contains a component that corresponds to both such a polymer component and a curable component, the composition for a resin film-forming film is considered to contain both a polymer component and a curable component.

1.2.1 Polymer Component
The polymer component (A) provides the resin film-forming film with film-forming properties (film-forming properties) while providing appropriate tack, thereby ensuring uniform attachment of the resin film-forming film to the workpiece. The weight-average molecular weight of the polymer component is usually in the range of 50,000 to 2,000,000, preferably 100,000 to 1,500,000, and particularly preferably 200,000 to 1,000,000. If the weight-average molecular weight is too low, the peeling force of the release film tends to increase. On the other hand, if the weight-average molecular weight is too high, the compatibility with other components becomes poor, and as a result, uniform film formation is hindered. Examples of such polymer components include acrylic resins, urethane resins, phenoxy resins, silicone resins, saturated polyester resins, etc., and acrylic resins are particularly preferred.

In this specification, the term "weight average molecular weight" refers to a polystyrene-equivalent value measured by gel permeation chromatography (GPC) unless otherwise specified. Measurements by such a method are carried out, for example, using a high-speed GPC apparatus "HLC-8120GPC" manufactured by Tosoh Corporation, connected in this order to high-speed columns "TSK guard column H _XL -H", "TSK Gel GMH _XL ", and "TSK Gel G2000 H _XL " (all manufactured by Tosoh Corporation), under conditions of a column temperature of 40°C, a liquid delivery rate of 1.0 mL/min, and a differential refractometer as a detector.

Examples of acrylic resins include (meth)acrylic acid ester copolymers consisting of (meth)acrylic acid ester monomers and structural units derived from (meth)acrylic acid derivatives. Here, the (meth)acrylic acid ester monomers are preferably (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 18 carbon atoms, and specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. Examples of (meth)acrylic acid derivatives include (meth)acrylic acid, glycidyl (meth)acrylate, and hydroxyethyl (meth)acrylate.

In this embodiment, it is preferable to introduce a glycidyl group into the acrylic resin using glycidyl methacrylate or the like. This improves the compatibility of the acrylic resin into which the glycidyl group has been introduced with the epoxy resin as the thermosetting component described below, and the glass transition temperature (Tg) of the resin film-forming film after curing increases, improving heat resistance. In this embodiment, it is preferable to introduce a hydroxyl group into the acrylic resin using hydroxyethyl acrylate or the like in order to control the adhesion to the workpiece and the adhesive properties.

The glass transition temperature of the acrylic resin is preferably -70°C to 40°C, more preferably -35°C to 35°C, even more preferably -20°C to 30°C, even more preferably -10°C to 25°C, and particularly preferably -5°C to 20°C. By setting the glass transition temperature of the acrylic resin within the above range, the fluidity of the resin film-forming film and the resin film when heated is suppressed, making it easier to obtain a smooth resin film. If the glass transition temperature is too low, the peeling force of the release film tends to increase. If the glass transition temperature is too high, the compatibility with other components becomes poor, resulting in the prevention of uniform film formation and the peeling force F2 of the light-surface release film tends to decrease excessively.

When an acrylic resin has m types of structural units (m is an integer of 2 or more), the glass transition temperature of the acrylic resin can be calculated as follows. That is, when m types of monomers that derive the structural units in the acrylic resin are each assigned a unique number from 1 to m, and named "monomer m", the glass transition temperature (Tg) of the acrylic resin can be calculated using the Fox formula shown below.

（式中、Ｔｇはアクリル樹脂のガラス転移温度であり；ｍは２以上の整数であり；Ｔｇｋはモノマーｍのホモポリマーのガラス転移温度であり；Ｗｋはアクリル樹脂における、モノマーｍから誘導された構成単位ｍの質量分率であり、ただし、Ｗｋは下記式を満たす。）

(In the formula, Tg is the glass transition temperature of the acrylic resin; m is an integer of 2 or more; Tgk is the glass transition temperature of a homopolymer of monomer m; and Wk is the mass fraction of structural unit m derived from monomer m in the acrylic resin, with the proviso that Wk satisfies the following formula.)

（式中、ｍ及びＷｋは、前記と同じである。）

(In the formula, m and Wk are the same as above.)

For Tgk, values listed in the Polymer Data Handbook, Adhesive Handbook, Polymer Handbook, etc. can be used. For example, the Tgk of a homopolymer of methyl acrylate is 10°C, the Tgk of a homopolymer of n-butyl acrylate is -54°C, the Tgk of a homopolymer of methyl methacrylate is 105°C, the Tgk of a homopolymer of 2-hydroxyethyl acrylate is -15°C, the Tgk of a homopolymer of glycidyl methacrylate is 41°C, and the Tgk of a homopolymer of 2-ethylhexyl acrylate is -70°C.

When the total weight of the composition for resin film-forming films is taken as 100 parts by mass, the content of the polymer component is preferably 5 to 80 parts by mass, more preferably 8 to 70 parts by mass, even more preferably 10 to 60 parts by mass, even more preferably 12 to 55 parts by mass, even more preferably 14 to 50 parts by mass, and particularly preferably 15 to 45 parts by mass. By having the content of the polymer component within the above range, the amount of low molecular weight components that increase the peeling force of the release film is limited to an appropriate range, making it easier to design the material for the composition for resin film-forming films.

(1.2.2 Thermosetting component)
The curable component (B) cures the resin film-forming film to form a hard resin film. As the curable component, a thermosetting component, an energy ray curable component, or a mixture thereof can be used. When cured by irradiation with energy rays, the resin film-formed film according to the present embodiment contains a filler and a colorant, which will be described later, and therefore the light transmittance is reduced. If the thickness is too thick, the energy ray curing tends to be insufficient.

On the other hand, thermosetting resin film-forming films can be sufficiently cured by heating even if they are thick, so a resin film with high protective performance can be formed. In addition, multiple resin film-forming films can be heated and thermally cured all at once by using a conventional heating means such as a heating oven.

Therefore, in this embodiment, it is preferable that the curable component is thermosetting. In other words, it is preferable that the resin film-forming film according to this embodiment is thermosetting.

Whether or not a resin film-formed film is thermosetting can be determined as follows. First, a resin film-formed film at room temperature (23°C) is heated to a temperature above room temperature, and then cooled to room temperature to obtain a resin film-formed film after heating and cooling. Next, when the hardness of the resin film-formed film after heating and cooling is compared with the hardness of the resin film-formed film before heating at the same temperature, if the resin film-formed film after heating and cooling is harder, the resin film-formed film is determined to be thermosetting.

As the thermosetting component, for example, epoxy resin, thermosetting polyimide resin, unsaturated polyester resin, and mixtures thereof are preferably used. Thermosetting polyimide resin is a general term for low molecular weight, low viscosity monomers or precursor polymers that form polyimide resins by thermal curing. Non-limiting examples of thermosetting polyimide resins are described in, for example, Sen-i-gakkaishi-journal "Sen-i to Kogyo" (Sen-i to Kogyo), Vol. 50, No. 3 (1994), pp. 106-118.

The epoxy resin as a thermosetting component has the property of forming a three-dimensional network and a strong coating when heated. As such an epoxy resin, various known epoxy resins are used. In this embodiment, the molecular weight (formula weight) of the epoxy resin is preferably 300 or more and less than 50,000, 300 or more and less than 10,000, 300 or more and less than 5,000, or 300 or more and less than 3,000. The epoxy equivalent of the epoxy resin is preferably 50 to 5,000 g/eq, more preferably 100 to 2,000 g/eq, and even more preferably 150 to 1,000 g/eq.

Specific examples of such epoxy resins include glycidyl ethers of phenols such as bisphenol A, bisphenol F, resorcinol, phenyl novolac, and cresol novolac; glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; glycidyl ethers of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; glycidyl or alkyl glycidyl epoxy resins in which active hydrogen bonded to nitrogen atoms such as aniline isocyanurate is substituted with a glycidyl group; and so-called alicyclic epoxides in which epoxy is introduced by, for example, oxidizing the carbon-carbon double bonds in the molecule, such as vinylcyclohexane diepoxide, 3,4-epoxycyclohexylmethyl-3,4-dicyclohexanecarboxylate, and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane. Other epoxy resins having a biphenyl skeleton, dicyclohexadiene skeleton, naphthalene skeleton, and the like can also be used.

When using an epoxy resin that is liquid at room temperature (23°C) among these epoxy resins, the weight of the epoxy resin that is liquid at room temperature is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 1 to 11 parts by mass, when the total weight of the composition for resin film-forming films is 100 parts by mass. If a large amount of such liquid epoxy resin is included, the peeling force of the release film from the resin film-forming film tends to increase.

Epoxy resins that are liquid at room temperature (23°C) (liquid epoxy resins) include, for example, glycidyl ether of bisphenol A (bisphenol A type epoxy resin), glycidyl ether of bisphenol F (bisphenol F type epoxy resin), phenol novolac type epoxy resin, naphthalene type epoxy resin, cyclohexane dimethanol type epoxy resin, and glycidyl amine type epoxy resin, etc., which have small molecular weights.

When a thermosetting component is used as the curing component (B), it is preferable to use a curing agent (C) as an auxiliary in combination. A heat-activated latent epoxy resin curing agent is preferable as a curing agent for epoxy resin. A "heat-activated latent epoxy resin curing agent" is a type of curing agent that does not react easily with epoxy resin at room temperature (23°C) and is activated by heating above a certain temperature and reacts with epoxy resin. Methods for activating a heat-activated latent epoxy resin curing agent include a method of generating active species (anions, cations) through a chemical reaction by heating; a method in which the agent is stably dispersed in epoxy resin near room temperature and becomes compatible and dissolved with epoxy resin at high temperatures to start a curing reaction; a method in which a molecular sieve-encapsulated type curing agent is dissolved at high temperatures to start a curing reaction; and a method using microcapsules.

Among the methods given above, the method in which the compound is stably dispersed in the epoxy resin at room temperature and becomes compatible and soluble in the epoxy resin at high temperatures, initiating the curing reaction, is preferred.

Specific examples of heat-activated latent epoxy resin curing agents include various onium salts, dibasic acid dihydrazide compounds, dicyandiamide, amine adduct curing agents, high melting point active hydrogen compounds such as imidazole compounds, etc. These heat-activated latent epoxy resin curing agents can be used alone or in combination of two or more. In this embodiment, dicyandiamide is particularly preferred.

Phenol resins are also preferred as curing agents for epoxy resins. As phenolic resins, condensates of phenols such as alkylphenols, polyhydric phenols, and naphthol with aldehydes can be used without any particular restrictions. Specifically, phenol novolac resin, o-cresol novolac resin, p-cresol novolac resin, t-butylphenol novolac resin, dicyclopentadiene cresol resin, polyparavinylphenol resin, bisphenol A type novolac resin, or modified products thereof can be used.

The phenolic hydroxyl groups contained in these phenolic resins can easily undergo addition reaction with the epoxy groups of the above epoxy resins when heated, forming a cured product with high impact resistance.

The content of the curing agent (C) is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, even more preferably 0.2 to 15 parts by mass, and particularly preferably 0.3 to 10 parts by mass, relative to 100 parts by mass of the epoxy resin. By setting the content of the curing agent (C) within the above range, the network structure of the resin film becomes dense, making it easier to obtain the performance of protecting the workpiece as a resin film.

When dicyandiamide is used as the curing agent (C), it is preferable to use a curing accelerator (D) in addition. As the curing accelerator, for example, imidazoles (imidazoles in which one or more hydrogen atoms are replaced by groups other than hydrogen atoms) such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole are preferable. Among these, 2-phenyl-4,5-dihydroxymethylimidazole is particularly preferable.

The content of the curing accelerator is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, even more preferably 0.2 to 15 parts by mass, and particularly preferably 0.3 to 10 parts by mass, relative to 100 parts by mass of the epoxy resin. By setting the content of the curing accelerator (D) within the above range, the network structure of the resin film becomes dense, making it easier to obtain the performance of protecting the workpiece as a resin film.

When the total weight of the composition for resin film-forming films is taken as 100 parts by mass, the total content of the thermosetting component and the curing agent is preferably 3 to 80 parts by mass, more preferably 5 to 60 parts by mass, more preferably 7 to 50 parts by mass, even more preferably 9 to 40 parts by mass, and particularly preferably 10 to 30 parts by mass. When the thermosetting component and the curing agent are mixed in such a ratio, the composition exhibits a suitable tack before curing, and application work can be performed stably. In addition, after curing, the composition is likely to have the ability to protect the workpiece as a resin film.

When low molecular weight compounds are used as the thermosetting component and curing agent, the tack of the resin film-forming film may increase, and the peeling force of the release film may increase. Therefore, it is desirable to select the type and amount of the thermosetting component and curing agent so as to control the tack to an appropriate value within the above range.

(1.2.3 Energy Ray-Curable Component)
When the curable component (B) is an energy ray-curable component, the energy ray-curable component is preferably uncured and preferably has adhesive properties, and more preferably is uncured and has adhesive properties.

The energy ray curable component is a component that is cured by irradiation with energy rays, and is also a component that imparts film-forming properties, flexibility, etc. to the resin film-forming film.

As the energy ray curable component, for example, a compound having an energy ray curable group is preferable. Examples of such compounds include known compounds.

When a low molecular weight compound is used as the energy ray curable component, the tack of the resin film-forming film may increase, and the peeling force of the release film may increase. Therefore, it is desirable to select the type and amount of the energy ray curable component so as to control the tack to an appropriate value.

(1.2.4 Filler)
By containing the filler (E) in the resin film-formed film, the resin film formed from the resin film-formed film can easily adjust the thermal expansion coefficient, and the thermal expansion coefficient can be made closer to the thermal expansion coefficient of the workpiece. Therefore, the adhesive reliability of the package obtained by using the resin film-forming film is further improved. In addition, since the resin film-forming film contains the filler (E), a hard resin film is obtained, and further, The moisture absorption rate of the film can be reduced, and the adhesive reliability of the package is further improved.

The filler (E) may be either an organic filler or an inorganic filler, but from the viewpoint of shape stability at high temperatures, it is preferable that it is an inorganic filler.

Preferred inorganic fillers include, for example, powders of silica, alumina, talc, calcium carbonate, red iron oxide, silicon carbide, boron nitride, etc.; beads obtained by shaping these inorganic fillers into spherical shapes; surface-modified products of these inorganic fillers; single crystal fibers of these inorganic fillers; glass fibers, etc. Among these, silica and surface-modified silica are preferred. The surface-modified silica is preferably surface-modified with a coupling agent, and more preferably surface-modified with a silane coupling agent.

The average particle size of the filler is preferably 0.02 to 10 μm, more preferably 0.05 to 5 μm, and particularly preferably 0.10 to 3 μm.

By setting the average particle size of the filler to the above value, the composition for resin film-forming films is easy to handle. Therefore, the quality of the composition for resin film-forming films and the resin film-forming films tends to be stable.

In this specification, unless otherwise specified, "average particle size" refers to the particle size (D50) at 50% cumulative value in the particle size distribution curve obtained by the laser diffraction scattering method.

When the total weight of the composition for resin film-forming films is 100 parts by mass, the upper limit of the filler content is preferably less than 80 parts by mass, more preferably less than 70 parts by mass, more preferably less than 60 parts by mass, and particularly preferably less than 55 parts by mass, and the lower limit is preferably 15 parts by mass or more, more preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more.

By setting the filler content to the above value, it is easy to control the peel strength of the release film within an appropriate range. If the filler content is too low, the tack of the resin film-forming film increases, and the peel strength of the release film increases excessively. On the other hand, if the filler content is too high, the shape retention of the resin film-forming film may decrease.

The resin film-forming film may also contain two or more types of fillers. That is, the filler (E) may be a mixture of two or more types of fillers. "Containing two or more types of fillers" may mean that the film contains two or more types of fillers that are different in material or that have two or more types of fillers that have different average particle sizes.

Whether or not a resin film or a resin film-forming film contains two or more types of fillers with different average particle sizes can also be confirmed by observing the cross section of the resin film or the resin film-forming film.

1.2.5 Coupling Agents
The resin film-forming film preferably contains a coupling agent (F). By containing the coupling agent, after the resin film-forming film is cured, the adhesion between the resin film and the workpiece can be improved without impairing the heat resistance of the resin film, and water resistance (moisture and heat resistance) can be improved. As the coupling agent, a silane coupling agent is preferred from the viewpoint of its versatility and cost merit.

Examples of silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-(methacryloxypropyl)trimethoxysilane, γ-aminopropyltrimethoxysilane, N-6-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-6-(aminoethyl)-γ-aminopropylmethyldiethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfane, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane, and imidazolesilane. These can be used alone or in combination of two or more.

Preferred silane coupling agents include oligomeric silane coupling agents having multiple alkoxysilyl groups in one molecule. The oligomeric silane coupling agents are preferred in that they are less likely to volatilize and have multiple alkoxysilyl groups in one molecule, which makes them effective in improving durability. Examples of the oligomeric silane coupling agents include epoxy group-containing oligomeric silane coupling agents "X-41-1053", "X-41-1059A", "X-41-1056" and "X-40-2651" (all manufactured by Shin-Etsu Chemical Co., Ltd.); mercapto group-containing oligomeric silane coupling agents "X-41-1818", "X-41-1810" and "X-41-1805" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

When the total weight of the composition for resin film-forming films is 100 parts by mass, the content of the coupling agent is preferably 0.01 to 20 parts by mass, 0.1 to 10 parts by mass, 0.2 to 5 parts by mass, or 0.3 to 3 parts by mass.

1.2.6 Colorants
The resin film-forming film preferably contains a colorant (G). This conceals the back surface of the workpiece such as a chip, thereby blocking various electromagnetic waves generated in electronic devices and reducing malfunctions of the workpiece such as a chip. In addition, if the resin film-forming film remains on rollers such as tension rollers in a resin film-forming film attachment device or on cutting blades, it can be immediately found by visual inspection. Furthermore, the average light reflectance at 400 to 800 nm of the contact surface of the resin film-forming film 11 with the heavy release film 12 described later can be easily controlled to a desired range.

As the colorant (G), for example, known pigments such as inorganic pigments, organic pigments, and organic dyes can be used. In this embodiment, inorganic pigments are preferred.

Examples of inorganic pigments include carbon black, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (indium tin oxide)-based pigments, and ATO (antimony tin oxide)-based pigments. Of these, it is particularly preferable to use carbon black. Carbon black can block electromagnetic waves over a wide wavelength range.

The amount of colorant (especially carbon black) in the resin film varies depending on the thickness of the resin film. For example, when the thickness of the resin film is 20 μm, the content of the colorant is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 4 parts by mass when the total weight of the composition for the resin film is 100 parts by mass.

The average particle size of the colorant (especially carbon black) is preferably 1 to 500 nm, more preferably 3 to 100 nm, and even more preferably 5 to 50 nm. If the average particle size of the colorant is within the above range, it is easy to control the light reflectance to the desired range.

(1.2.7 Other Additives)
The composition for resin film-forming film may contain other additives, such as a photopolymerization initiator, a crosslinking agent, a plasticizer, an antistatic agent, an antioxidant, a gettering agent, a tackifier, a release agent, etc., within the range that does not impair the effects of the present invention.

However, in this embodiment, the content of the release agent is preferably less than 0.00099 parts by mass when the total weight of the composition for resin film-forming film is 100 parts by mass. If the content of the release agent is too high, the adhesive reliability between the resin film and the workpiece tends to decrease. Examples of release agents include alkyd-based release agents, silicone-based release agents, fluorine-based release agents, unsaturated polyester-based release agents, polyolefin-based release agents, and wax-based release agents.

(1.2.8 Control of peel strength and adhesive strength in resin film-forming film)
As described above, in this embodiment, the peel force F1 of the heavy surface release film 12 from the resin film-forming film 11 and the peel force F2 of the light surface release film 13 from the resin film-forming film 11 satisfy the relationship F1>F2. As described above, such release characteristics can be controlled by the types and blending amounts of each component constituting the resin film-forming film, the types of release agents for the heavy surface release film 12 and the light surface release film 13, and the manufacturing process of the sheet for resin film formation.

When the weight average molecular weight of the polymer component (A) is low, the peel strength tends to increase. When the glass transition temperature of the polymer component (A) is low, the peel strength tends to increase. In addition, when low molecular weight compounds are used as the curable component (B), the curing agent (C), the curing accelerator (D), and the energy ray curable component, the peel strength tends to increase. When the amount of filler (E) is large, the peel strength tends to decrease.

The peeling force can also be controlled by partially curing the resin film-forming film. For example, the peeling force can be reduced by partially curing the curable component (B).

Furthermore, the peeling forces F1 and F2 can be controlled by the peeling treatment of the heavy release film 12 and the light release film 13. They can also be controlled by the manufacturing process of the resin film forming sheet. This will be described later.

(2. Sheet for resin film formation)
Before use, the resin film-forming film is stored in the form of a three-layered resin film-forming sheet 10 in which the resin film-forming film 11 is sandwiched between two release films (heavy release film 12 and light release film 13) as shown in Fig. 1. The release film is peeled off when the resin film-forming film is used. The resin film-forming sheet is usually long and is stored and transported in a roll shape.

The heavy release film and the light release film may be composed of one layer (single layer) or two or more layers of the substrate, and the surface of the substrate may be subjected to a release treatment in order to control the release property. That is, the surface of the substrate may be modified, or a layer of a material different from the substrate may be formed on the surface of the substrate. In this embodiment, the heavy release film and the light release film preferably have a substrate and a release agent layer. By having a release agent layer, it is easy to control the physical properties of the surface on which the release agent layer is formed in the heavy release film and the light release film. In this embodiment, a coating agent containing a composition for the release agent layer described later is applied to one surface of the substrate, and the coating film is then dried and cured to form a release agent layer. This results in the heavy release film and the light release film.

(2.1 Heavy-Surface Release Film 12)
The thickness of the heavy-side release film 12 is not particularly limited, but is preferably 30 to 100 μm, more preferably 40 to 80 μm, and even more preferably 45 to 70 μm, and is preferably thicker than the thickness of the light-side release film 13 described below.

By having the thickness of the heavy release film 12 within the above range, the sheet for forming the resin film can be cut to fit the shape of the workpiece with excellent workability.

The thickness of the heavy release film 12 refers to the thickness of the entire heavy release film. For example, the thickness of a heavy release film made up of multiple layers refers to the total thickness of all layers that make up the heavy release film.

Examples of the substrate of the heavy release film 12 include resin films and paper. Examples of the resin of the resin film include polyethylene terephthalate, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polybutylene terephthalate, polyurethane, ethylene-vinyl acetate copolymer, ionomer resin, ethylene (meth)acrylic acid copolymer, polystyrene, polycarbonate, fluororesin, low density polyethylene, linear low density polyethylene, and triacetyl cellulose. Examples of the paper include fine paper, coated paper, glassine paper, and laminated paper. These may be used alone or in combination of two or more types. Among these, polyethylene terephthalate film is preferred from the viewpoints of low cost and rigidity.

At least one surface of the heavy-surface release film 12 (the surface to be laminated with the resin film-forming film 11) may be subjected to a release treatment using a release agent layer composition. The thickness of the release agent layer is preferably 30 nm or more and 200 nm or less, and more preferably 50 nm or more and 180 nm or less.

The heavy release film 12 can be easily obtained by subjecting one surface of the above-mentioned substrate to a release treatment. The release agent layer composition used in such a release treatment is preferably, for example, an alkyd-based release agent, a silicone-based release agent, a fluorine-based release agent, an unsaturated polyester-based release agent, a polyolefin-based release agent, or a wax-based release agent. Of these, a silicone-based release agent is preferred, and it is particularly preferred to include a silicone-based release agent and a heavy release additive.

As a silicone-based release agent, a silicone release agent containing silicone having dimethylpolysiloxane as the basic skeleton can be used.

The silicone may be any of addition reaction type, condensation reaction type, and energy ray curing type such as ultraviolet curing type and electron beam curing type, but addition reaction type silicone is preferable. Addition reaction type silicone has high reactivity and excellent productivity, and has the advantages of small change in release force after production and no cure shrinkage compared to condensation reaction type.

Specific examples of addition reaction type silicones include organopolysiloxanes that have two or more alkenyl groups with 2 to 10 carbon atoms, such as vinyl groups, allyl groups, propenyl groups, and hexenyl groups, at the ends and/or side chains of the molecule.

When the total weight of the release layer composition (excluding the catalyst described below) is taken as 100 parts by mass, the content of silicone consisting of dimethylpolysiloxane is preferably less than 100 parts by mass, more preferably less than 90 parts by mass, even more preferably less than 80 parts by mass, and particularly preferably less than 70 parts by mass.

When using such addition reaction type silicones, it is preferable to use a crosslinker and a catalyst in combination.

Examples of crosslinking agents include organopolysiloxanes that have at least two hydrogen atoms bonded to silicon atoms in each molecule.

Specific examples of crosslinking agents include dimethylhydrogensiloxane-methylhydrogensiloxane copolymers endblocked with dimethylhydrogensiloxane, trimethylsiloxy group endblocked dimethylsiloxane-methylhydrogensiloxane copolymers, trimethylsiloxy group endblocked methylhydrogenpolysiloxane, poly(hydrogensilsesquioxane), etc.

Catalysts include fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, platinum group metal compounds such as palladium and rhodium, etc.

By using such a catalyst, the curing reaction of the release agent layer composition can proceed more efficiently.

When the total weight of the release agent layer composition (excluding the catalyst) is taken as 100 parts by mass, the content of the silicone-based release agent is preferably 30 to 100 parts by mass, and more preferably 50 to 100 parts by mass, from the viewpoint of keeping the release force F1 within an appropriate range.

The heavy release additive is used to increase the peeling force F1 of the heavy release film 12 from the resin film-forming film 11. Examples of heavy release additives include silicone resins and organosilanes such as silane coupling agents, and among these, it is preferable to use silicone resins.

As the silicone resin, for example, it is preferable to use an MQ resin containing an M unit, which is a monofunctional siloxane unit [R ₃ SiO _1/2 ], and a Q unit, which is a tetrafunctional siloxane unit [SiO _4/2 ]. The three R in the M unit each independently represents a hydrogen atom, a hydroxyl group, or an organic group. From the viewpoint of easily suppressing silicone migration, it is preferable that one or more of the three R in the M unit is a hydroxyl group or a vinyl group, and more preferably a vinyl group.

When the total weight of the release agent layer composition (excluding the catalyst) is taken as 100 parts by mass, the content of the heavy release additive is preferably 0 to 50 parts by mass, more preferably 5 to 45 parts by mass, and particularly preferably 10 to 40 parts by mass.

From the viewpoint of adjusting the viscosity and improving the applicability to the substrate, the composition for the release agent layer is preferably used as a coating agent containing a diluting solvent together with the various active ingredients described above. In this specification, the term "active ingredient" refers to the components contained in the coating agent containing the target composition, excluding the diluting solvent.

Examples of dilution solvents include organic solvents such as aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and heptane. These dilution solvents may be used alone or in combination of two or more.

The active ingredient (solid content) concentration of the coating agent containing the release layer composition is preferably 0.3 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 0.5 to 3% by mass.

The release agent layer composition may contain additives that are commonly used in release agent layers, as long as the effects of the present invention are not impaired. Such additives include pigments, dyes, dispersants, and the like.

(2.2 Light-sided release film 13)
The thickness of the light-side release film 13 is not particularly limited, but from the viewpoint of facilitating release, it is preferably equal to or less than the thickness of the heavy-side release film 12, and more preferably thinner than the heavy-side release film 12. Therefore, the thickness of the light-side release film 13 is preferably 10 to 75 μm, more preferably 18 to 60 μm, and even more preferably 24 to 45 μm.

The material of the substrate used in the light-surface release film 13 is the same as that of the heavy-surface release film 12. The composition for the release agent layer of the light-surface release film 13 can be selected from the materials exemplified for the heavy-surface release film 12, so long as the relationship between F1 and F2 above is satisfied. However, when the release force is controlled by the composition of the release agent layer composition, it is preferable that the material exemplified as the heavy release additive is contained in a smaller amount than in the heavy-surface release film 12, or is not contained at all.

In addition, silicone oil can be added to the release agent layer composition to keep the release force low, so silicone oil may be used to adjust the release force.

(2.3 Control of the release force in the release film)
The peel forces F1 and F2 are controlled by the following various factors in addition to the composition of the resin film-formed film.
The type of resin material that constitutes the main component of the release agent layer composition (silicone-based, fluorine-based, long-chain alkyl-based, etc.)
The molecular weight of the resin material constituting the main component of the composition for the release agent layer The crosslinking density of the composition for the release agent layer (this crosslinking density is also affected by the type of crosslinking agent, the content thereof before the crosslinking reaction proceeds, the density of functional groups reacting with the crosslinking agent, etc.)
Additive components contained in the composition for the release agent layer (specific examples include low molecular weight substances that do not crosslink and/or are difficult to crosslink).
-Thickness of the release agent layer -Surface roughness of the surface of the release agent layer bonded to the resin film-coated film -Thickness of the resin film as the substrate -Temperature when the release film and the resin film-coated film are bonded together -Pressure when the release film and the resin film-coated film are bonded together -Roller speed when the release film and the resin film-coated film are bonded together

When the resin film substrate is thin, it can be peeled off with a small peeling force, but when it is thick, the peeling force tends to increase. When one side of a release film is roughened and a resin film-forming film is formed on the roughened surface, the peeling force of the release film tends to increase, that is, it becomes a heavy-surface release film. In addition, when a coating agent containing a composition for a resin film-forming film described below is applied to a first release film, and after drying as necessary, a second release film is laminated, the peeling force of the first release film tends to increase and the peeling force of the second release film tends to decrease.

If the surface of the release film that is bonded to the resin film-forming film is smoothed, a heavy release film and a light release film can be obtained by formulating a composition for the release agent layer without being affected by the manufacturing process described above. When controlling the release force of the heavy release film by formulating a composition for the release agent layer, the arithmetic mean height Sa of the contact surface of the heavy release film with the resin film-forming film (the release treatment surface of the heavy release film) is preferably 1 μm or less, more preferably 0.2 μm or less, even more preferably 0.1 μm or less, and particularly preferably less than 0.03 μm. The arithmetic mean height Sa of the release treatment surface of the heavy release film 12 can be controlled, for example, by the film-forming method of the resin film that is the substrate (specifically, the stretching method, the temperature and surface roughness of the cooling roll), the surface treatment of the substrate after film formation, the thickness of the release agent layer, etc.

The arithmetic mean height of the surface is one of the surface roughness parameters defined in ISO 25178, and is the average of the absolute values of the peak height and valley depth on the measured surface. In this specification, the arithmetic mean height Sa is the surface roughness obtained by using a rectangular area of 1.0 mm x 1.0 mm as the measured surface. The method for measuring the arithmetic mean height Sa in this invention will be described in detail in the Examples below.

(2.4 Control of Identification of Double-Sided Release Film)
An object of the present invention is to improve the accuracy of confirming the peeling of a heavy release film 12 when processing a workpiece such as a semiconductor wafer using a sheet for resin film formation.

To achieve this objective, the present invention is characterized in that the heavy release film 12 has a light transmittance of 80% or less at 555 nm or a haze of 4% or more. The heavy release film may simultaneously satisfy the light transmittance and haze. When the heavy release film 12 satisfies the light transmittance and/or haze, the heavy release film 12 becomes highly identifiable, and it can be reliably determined by a sensor or visual inspection whether the heavy release film 12 has been peeled off, allowing smooth processing of the workpiece.

From this perspective, the light transmittance of the heavy-surface release film 12 at 555 nm is preferably 70% or less, more preferably 60% or less, and particularly preferably 50% or less. By being below the upper limit, it is possible to further improve the distinguishability. There is no particular restriction on the lower limit of the light transmittance, but there is no need to reduce the light transmittance excessively, and it is preferably 1% or more, more preferably 10% or more, and particularly preferably 30% or more. The light transmittance in the present invention is measured as described in the examples below.

From the viewpoint of controlling the light transmittance of the heavy release film 12 within the above range, it is preferable that the heavy release film 12 is colored. The heavy release film 12 may be colored by coloring the substrate itself, but it is simple to provide a colored layer containing a pigment or dye on one side of the heavy release film 12. The pigments and dyes used are not particularly limited, but examples include white pigments (NX-501 White, manufactured by Dainichi Seika Chemicals Co., Ltd.), black pigments (Multilac A903 Black, manufactured by Toyo Ink Co., Ltd.), and red pigments (NX-031 Red, manufactured by Dainichi Seika Chemicals Co., Ltd.). The amount of these pigments and dyes used is not particularly limited as long as the light transmittance of the heavy release film 12 can be controlled within the above range. When the above pigments are used, the pigments may be blended in an amount of about 1 to 40 parts by mass per 100 parts by mass of the solid content of the colored layer. The thickness of the colored layer is not particularly limited, but from the viewpoint of not affecting the releasability of the heavy release film 12, it is preferable that the thickness is about 10 to 500 nm. It is preferable to provide the above-mentioned colored layer on one side of the heavy-surface release film 12 and a release agent layer on the other side. In addition, a pigment or dye may be blended into the composition for the release agent layer to color the release agent layer.

Similarly, from the viewpoint of improving the distinguishability of the heavy release film 12, the haze of the heavy release film 12 is preferably 6% or more, more preferably 10% or more, and particularly preferably 20% or more. There is no particular upper limit to the haze, but there is no need to increase the haze excessively, and the haze is preferably 70% or less, more preferably 60% or less, and particularly preferably 55% or less. The haze in the present invention is measured using a haze meter as described in the examples below.

From the viewpoint of controlling the haze of the heavy release film 12 within the above range, it is preferable that at least one surface of the heavy release film 12 is roughened. The roughening treatment may be performed on both surfaces of the heavy release film 12. The method for roughening the heavy release film 12 is not particularly limited, but for example, the surface of the base material used for the heavy release film 12 is roughened by sandblasting or polishing with sandpaper. The release treatment may be performed on the surface opposite to the roughened surface, or the release treatment may be performed on the roughened surface. The degree of roughening is not particularly limited as long as the haze of the heavy release film 12 can be controlled within the above range.

(2.5 Control of the identifiability of resin film-formed film)
As described above, the present invention improves the accuracy of confirmation of the peeling of the heavy release film 12 by controlling the light transmittance and/or haze of the heavy release film 12. Furthermore, from the viewpoint of improving the accuracy of confirmation that the resin film-forming film remains in accordance with the shape of a workpiece on a light-reflective or glossy workpiece, typically a ground wafer, after the heavy release film 12 is peeled off, or from the viewpoint of improving the accuracy of confirmation that the resin film-forming film remains on a metal cutting blade or the like, which has light reflectivity or gloss, it is preferable that the average light reflectance of the resin film-forming film 11 at 400 to 800 nm on the contact surface with the heavy release film 12 is 40% or less.

When the heavy release film 12 is peeled off from the resin film-forming film 11, the surface of the resin film-forming film 11 that was in contact with the heavy release film 12 is exposed. If this exposed surface can be confirmed, it can be confirmed that the heavy release film 12 has been peeled off. For this reason, in order to confirm the surface of the resin film-forming film 11 after the heavy release film is peeled off with a sensor or by visual inspection, the average light reflectance at 400 to 800 nm on the surface of the resin film-forming film 11 is preferably 40% or less, more preferably 32% or less, more preferably 25% or less, even more preferably 18% or less, and particularly preferably 10% or less. In addition, the lower limit of the average light reflectance is not particularly limited, but from the viewpoint of easier material design of the composition for the resin film-forming film, it is preferably 0.1% or more, more preferably 1% or more, more preferably 2% or more, and particularly preferably 3% or more. The light reflectance in the present invention is measured using an integrating sphere as described in the examples below. The average light reflectance of the surface of the resin film-forming film 11 at 400 to 800 nm can be controlled, for example, by adjusting the material type, particle size, and content of the colorant and filler contained in the resin film-forming film.

(3. Manufacturing method of sheet for resin film formation)
The method for producing the resin film-forming film is not particularly limited. The film is produced using the above-mentioned composition for resin film-forming film, or a composition obtained by diluting the composition for resin film-forming film with a solvent (these two compositions are referred to as "coating agent containing a composition for resin film-forming film" in this specification). Examples of dilution solvents include organic solvents such as aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and heptane. These dilution solvents may be used alone or in combination of two or more. The coating agent is prepared by mixing the components constituting the composition for resin film-forming film by a known method.

The obtained coating agent is applied to the release surface of the heavy release film 12 using a coating machine such as a roll coater, knife coater, roll knife coater, air knife coater, die coater, bar coater, gravure coater, curtain coater, etc., and dried as necessary. Then, a light release film 13 is laminated on the exposed surface of the resin film-forming film 11 to obtain the sheet for resin film formation 10 according to this embodiment. The sheet for resin film formation 10 is preferably a roll body wound in a roll shape as a long sheet that has been cut and has the same width of the heavy release film, the resin film-forming film, and the light release film, and has not yet been punched. The order of lamination is not particularly limited, and the coating agent may be applied to the light release film. Alternatively, the coating agent may be applied to another resin film, dried as necessary, and the obtained resin film-forming film may be transferred to the heavy release film or the light release film. Furthermore, after laminating these films, they may be heated and pressed by a heat roller or the like. From the viewpoint of workability during manufacturing, it is also possible to apply the adhesive to the release surface of the heavy release film 12 and dry it as necessary, and then laminate a release film for process use on the exposed surface of the resin film-forming film 11, after which the release film for process use is peeled off and a light release film 13 is applied.

(4. Workpiece machining method)
In the sheet 10 for resin film formation according to the present embodiment, the resin film forming film 11 may be punched into a predetermined shape (precut), but as described below, the film may not be punched before application and may be cut to fit the outer peripheral shape of the work after application to the work. The latter method will be described in detail below.

First, as shown in FIG. 1, a sheet 10 for forming a resin film that has not been punched is prepared. The light release film 13 of the sheet 10 for forming a resin film is peeled off. When removing the light release film 13 from the resin film forming film 11, satisfying the relationship F1>F2 makes it easier to remove the light release film 13, and the resin film forming film 11 can be reliably left on the heavy release film 12.

As an example of a method for processing a workpiece according to this embodiment, a method for manufacturing a chip with a protective film obtained by processing a wafer to which a resin film-forming film is attached will be described. For this reason, hereinafter, the resin film-forming film may be referred to as a "protective film-forming film."

The method for manufacturing a chip with a protective film includes at least the following steps 1 to 5.
Step 1: A step of peeling off the light-surface release film 13 from the protective film-forming sheet 10 and attaching the protective film-forming film 11 to the back surface of the wafer. Step 2: A step of cutting the protective film-forming film 11 and the heavy-surface release film 12 to match the outer peripheral shape of the wafer. Step 3: A step of converting the attached protective film-forming film into a protective film. Step 4: A step of peeling off the heavy-surface release film 12 from the protective film or protective film-forming film. Step 5: A step of singulating the wafer having the protective film or protective film-forming film on the back surface to obtain a plurality of chips with the protective film or protective film-forming film.

In step 1, the light release film 13 of the protective film forming sheet 10 is peeled off to expose the protective film forming film 11, and the exposed protective film forming film 11 is attached to the back surface of the wafer. The light release film 13 has a smaller peeling force than the heavy release film 12, so the light release film 13 can be peeled off smoothly. When attaching the protective film forming film 11 to the wafer, thermocompression bonding may be performed.

Then, the attached protective film-forming film 11 and heavy-surface release film 12 are cut to match the outer peripheral shape of the wafer (step 2), to obtain a wafer with a protective film-forming film. Note that if the protective film-forming film 11 is non-curable, the protective film-forming film will become a protective film at the end of step 1, but for convenience, it will be referred to as the "protective film-forming film" here.

In step 3, the protective film-forming film is made into a protective film. If the protective film-forming film 11 is thermosetting, the protective film-forming film 11 can be heated at a predetermined temperature for an appropriate time. If the protective film-forming film 11 is energy ray curable, an energy ray-transmitting film can be used as the heavy-surface release film 12, and energy rays can be applied from the heavy-surface release film 12 side. If the protective film-forming film 11 is non-curable, it is made into a protective film at the end of step 1.

The protective film-forming film 11 may be cured before peeling off the heavy release film 12 (step 4) or after peeling off the heavy release film 12, provided that the curing is performed after steps 1 and 2. The protective film-forming film 11 may also be cured after the dicing step (step 5) described below, in which case the chip with the protective film-forming film attached may be picked up from the dicing sheet and the protective film-forming film 11 may then be cured.

Next, the double-sided release film 12 is peeled off from the protective film or protective film-forming film 11 (step 4). For example, in step 4, one or more wafers with the protective film or protective film-forming film with the double-sided release film 12 are arranged in a straight line so that the wafers do not overlap each other, and each double-sided release film 12 is attached to a long adhesive tape called a peeling tape, and then the adhesive tape with the double-sided release film is moved in a direction away from the protective film or protective film-forming film 11, thereby peeling off the double-sided release film 12. In the present invention, the light transmittance and/or haze of the double-sided release film 12 are controlled within a specific range, so that the peeling of the double-sided release film 12 can be confirmed with high accuracy. Therefore, the transfer to the next step can be performed smoothly and reliably.

Then, the wafer with the protective film or protective film-forming film is transferred onto a known dicing sheet, and the wafer with the protective film or protective film-forming film is diced to obtain chips having the protective film or protective film-forming film (step 5). Thereafter, the dicing sheet is expanded in the planar direction as necessary, and the chip with the protective film or protective film-forming film is picked up from the dicing sheet by a suction collet or the like. The picked-up chip with the protective film or protective film-forming film may be transported to the next process, or may be temporarily stored in a tray, tape, or the like and transported to the next process after a predetermined period of time. The chip with the protective film or protective film-forming film transported to the next process may be mounted on a substrate according to conventional methods.

(5. Modifications)
In the above, the case where a protective film is formed using a resin film-forming film has been described, but as described above, an adhesive film may be formed using a resin film-forming film. In this case, the resin film-forming film functions as a die bonding film. The die bonding film is composed of a film-like adhesive. The film-like adhesive may have a known composition and physical properties.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and may be modified in various ways within the scope of the present invention.

The invention will be described in more detail below using examples, but the invention is not limited to these examples.

(Preparation of resin film forming sheet)
[Heavy release film]
A colored layer was formed or a surface roughening treatment was performed on one side of a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical, product name: Diafoil (registered trademark) T-100, thickness: 50 μm) by the method described in the table below, and a release treatment was performed with a release agent layer composition described below, to obtain heavy surface release films Nos. 1 to 9 and 14.

In addition, one side of a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical, product name: Diafoil (registered trademark) T-100, thickness: 50 μm) was subjected to a release treatment with a release agent layer composition described below to obtain heavy release film No. 13. Furthermore, in heavy release film Nos. 10 to 12, a roughening treatment was applied to the side opposite to the release treatment side in heavy release film No. 13.

DPHA: Dipentaerythritol hexaacrylate Irg. 184: Irgacure 184
MEK: methyl ethyl ketone

<Composition for Release Agent Layer>
The following release agent layer composition was prepared.

The above raw materials were added to a mixed solvent of toluene and methyl ethyl ketone (toluene/methyl ethyl ketone = 1/1 (mass ratio)) in the mixing ratio (solid content equivalent) shown in Table 2 to adjust the total solid content to 2 mass%, and a coating agent containing a release agent layer composition was prepared. The coating agent was applied to the PET film on which the above-mentioned colored layer was formed or which was subjected to the roughening treatment so that the film thickness after drying would be 0.15 μm, and then heated and dried to form a release agent layer on the PET film, and heavy surface release films Nos. 1 to 9 and 14 were produced.

In addition, a coating agent containing the same release agent layer composition was prepared and applied to the above-mentioned PET film so that the film thickness after drying would be 0.15 μm, followed by heating and drying to form a release agent layer on the PET film, producing heavy surface release film No. 13.

Separately, a coating agent containing the same release agent layer composition was prepared and applied to the above-mentioned PET film so that the film thickness after drying would be 0.15 μm, followed by heating and drying to form a release agent layer on the PET film, and the side opposite the release treatment surface was roughened to produce heavy surface release films Nos. 10 to 12.

[Lightweight release film]
A coating agent containing the above-mentioned composition for release agent layer was applied to a PET film (manufactured by Mitsubishi Chemical, product name: Diafoil (registered trademark) T-100, thickness: 38 μm) so that the film thickness after drying would be 0.15 μm, and then heated and dried to form a release agent layer on the PET film, thereby producing a light-surface release film. Note that the release agent layer of the light-surface release film is the same as that of the heavy-surface release film, but the thickness of the PET film is thin, and furthermore, since a coating agent containing the composition for resin film-forming film was applied to the heavy-surface release film and dried, and then the light-surface release film was attached, it has lighter releasability than the heavy-surface release film.

[Coating agent containing composition for resin film-forming film]
The following components were mixed in the compounding ratio (solid content equivalent) shown in Table 3, and diluted with methyl ethyl ketone to a solid content concentration of 50 mass % to prepare a coating agent containing a composition for a resin film-forming film.

(A) Polymer component: A copolymer obtained by copolymerizing 87 parts by mass of methyl acrylate and 13 parts by mass of 2-hydroxyethyl acrylate (weight average molecular weight: 450,000, glass transition temperature: 6°C)
(B) Curable component (thermosetting component)
(B-1) Bisphenol A type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828, epoxy equivalent 184 to 194 g/eq)
(B-2) Dicyclopentadiene type epoxy resin (manufactured by DIC Corporation, Epicron HP-7200, epoxy equivalent 254 to 264 g/eq)
(C) Curing agent: Dicyandiamide (DICY7, manufactured by Mitsubishi Chemical Corporation)
(D) Curing accelerator: 2-phenyl-4,5-dihydroxymethylimidazole (Curesol 2PHZ, manufactured by Shikoku Chemical Industry Co., Ltd.)
(E) Filler: Epoxy group-modified spherical silica filler (manufactured by Admatechs Co., Ltd., SC2050MA, average particle size 0.5 μm)
(F) Silane coupling agent: Shin-Etsu Chemical Co., Ltd., X-41-1056
(G) Colorant (G-1) Organic black pigment (6377 Black, manufactured by Dainichiseika Color & Chemicals Co., Ltd.)
(G-2) Titanium oxide-based white pigment (NX-501 White, manufactured by Dainichiseika Chemicals Co., Ltd.)

The coating agent containing the prepared resin film-forming film composition was applied to the release-treated surface of the heavy release film and dried at 100°C for 2 minutes to form a resin film-forming film with a thickness of 25 μm. Next, a light release film was attached to the resin film-forming film to obtain a resin film-forming sheet, which is a laminate of heavy release film/resin film-forming film/light release film. The attachment conditions were a temperature of 60°C, a pressure of 0.4 MPa, and a speed of 1 m/min. In this state, it was left to stand for 48 hours in an environment of 23°C and relative humidity of 50%.

Then, the resin film forming sheet was cut to a width of 220 mm and wound up to a length of 50 meters into a roll.

The following measurements and evaluations were carried out using the obtained resin film forming sheet.

[Peeling force F1 of heavy release film from resin film-formed film]
The light release film was peeled off from the obtained resin film forming sheet. The good adhesive surface of a 25 μm thick good adhesive PET (PET25A-4100, manufactured by Toyobo Co., Ltd.) was attached to the surface of the resin film forming film exposed by peeling by thermal lamination (70° C., 1 m/min) to prepare a laminate sample. The laminate sample was cut into a width of 100 mm to prepare a measurement sample. The back surface of the heavy release film of the measurement sample was fixed to a hard support plate with double-sided tape.

Using a universal tensile tester (Shimadzu Corporation, product name "Autograph (registered trademark) AG-IS"), the resin film/good adhesion PET composite (integrated) was peeled from the heavy release film at a peel angle of 180° and a peel speed of 1 m/min in an environment of 23°C and 50% relative humidity, and the load at that time was measured. The measurement distance was a total of 100 mm, and the average of the measured values over 80 mm excluding the first 10 mm and the last 10 mm was converted to the unit mN/100 mm and defined as the peel force F1. The results are shown in Table 4.

[Peeling force F2 of light release film from resin film-formed film]
The obtained sheet for resin film formation was cut into a width of 100 mm to prepare a measurement sample. The back surface of the heavy release film of the measurement sample was fixed to a hard support plate with double-sided tape.

Using a universal tensile tester (Shimadzu Corporation, product name "Autograph (registered trademark) AG-IS"), the light release film was peeled off from the measurement sample, and the load at that time was measured under the same conditions as for the measurement of F1 above, and this was taken as the peel force F2. The results are shown in Table 4.

[Method for evaluating the light transmittance of heavy release films]
The double-sided release film peeled off from the resin film forming sheet was placed in a sample holder of a UV-Vis spectrophotometer (Shimadzu Corporation's "UV-VIS-NIR SPECTROPHOTOMETER UV-3600"). The transmittance was measured in the wavelength range of 190 to 1200 nm in direct light receiving mode without using an integrating sphere. The light transmittance at 555 nm is shown in Table 4.

[Method for evaluating haze of heavy release film]
The haze of the heavy release film peeled off from the sheet for resin film formation was measured using a haze meter ("NDH-2000" manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136. The results are shown in Table 4.

[Method for evaluating the average light reflectance in the range of 400 to 800 nm]
The light release film was peeled off from the resin film forming sheet, and the surface of the resin film forming film was attached to a colorless, transparent, unroughened soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd., thickness 1.1 mm) (attaching conditions: lamination roller temperature 50°C, pressure 0.3 MPa, speed 1 m/min), and the heavy release film was peeled off.

The exposed resin film surface was measured using a UV-Vis spectrophotometer (Shimadzu Corporation's "UV-VIS-NIR SPECTROPHOTOMETER UV-3600") under the following conditions, in the wavelength range of 400 to 800 nm, using the SCE method to measure the amount of diffuse reflected light excluding specular reflected light (regular reflected light) at 1 nm intervals. In addition, the amount of diffuse reflected light was also measured using the same method for a barium sulfate reference plate. A Shimadzu Corporation "Large Sample Chamber MPC-3100" was used as the sample holder, and a Shimadzu Corporation "Integrating Sphere Accessory ISR-3100" was used as the integrating sphere.

Then, the ratio of the measured value of the resin film to the measured value of the reference plate ([measured light amount of the resin film]/[measured light amount of the reference plate] x 100), i.e., the relative reflectance of the resin film was calculated for every 1 nm. The relative reflectance values for every 1 nm in the wavelength range of 400 to 800 nm were added up, and the average light reflectance in the range of 400 to 800 nm was calculated by dividing the total by the number of added relative reflectance values (i.e., 800-400+1=401). The results are shown in Table 4.

[Evaluation method for arithmetic mean height Sa of peeling treatment surface]
The heavy release film peeled off from the laminate (resin film forming sheet) was measured for arithmetic mean height Sa in accordance with ISO 25178. More specifically, Sa was measured as follows.

That is, using a scanning white light interference microscope (Hitachi High-Tech Science Corporation, "VS-1550"), the release-treated surface of the heavy release film to be measured was observed in multiple field mode at a magnification of 50x. At this time, an area with a length of 0.36 mm in the X-axis direction and a length of 0.27 mm in the Y-axis direction was set in the observation field, and a total of 12 cells were observed by observing three columns in the X-axis direction and four rows in the Y-axis direction. The images of the 12 cells were then synthesized to create a single image of 1.0 mm x 1.0 mm, and Sa was measured for the entire area of this single synthesized image. The results are shown in Table 4.

[Testing to confirm peeling of heavy-duty release film using a sensor]
The exposed resin film-forming film obtained by peeling off the light release film from the resin film-forming sheet was attached to a silicon mirror wafer with a diameter of 200 mm (attachment conditions: lamination roller temperature 60° C., pressure 0.3 MPa, speed 1 m/min). Then, the resin film-forming film and the heavy release film were cut into a circle according to the shape of the wafer with a steel cutting blade. Next, a long adhesive tape (peeling tape) with a width of 20 mm was attached to the opposite side of the heavy release film from the resin film-forming film, and the heavy release film was peeled off from the resin film-forming film. The peeled circular heavy release film with a diameter of 200 mm was passed through a transmission sensor of FU-12 manufactured by Keyence Corporation at a traveling speed of 80 mm/sec, and a test was performed to see whether the operation of the heavy release film before, during and after the passage (i.e., whether the heavy release film was peeled off and passed through the sensor) could be immediately and correctly confirmed. The results are shown in Table 4. If peeling of the heavy release film could be confirmed, it was rated as "possible", and if not, it was rated as "not possible".

As shown in Table 4, the heavy release film used in the resin film forming sheet of the present invention is highly identifiable, and its release can be reliably confirmed.

10... Sheet for forming resin film (this embodiment)
11: Resin film-forming film 12: Heavy release film 13: Light release film

Claims (6)

A resin film-forming film for forming a resin film;
A heavy-surface release film provided on one surface of the resin film-forming film;
A light-surface release film is provided on the other surface of the resin film-forming film,
When the peel strength of the heavy release film from the resin film-formed film is F1 and the peel strength of the light release film from the resin film-formed film is F2, the relationship F1>F2 is satisfied,
The heavy-surface release film is a sheet for resin film formation that satisfies either one or both of the following: a light transmittance of 80% or less at 555 nm; and a haze of 4% or more. The sheet for forming a resin film according to claim 1, wherein at least one surface of the heavy release film is roughened. The sheet for forming a resin film according to claim 1, wherein the heavy release film is colored. The sheet for resin film formation according to claim 1, wherein the average light reflectance of the contact surface of the resin film-forming film with the heavy release film is 40% or less at 400 to 800 nm. The sheet for resin film formation according to claim 1, wherein the arithmetic mean height Sa of the contact surface of the heavy release film with the resin film-forming film is less than 0.03 μm. A process of peeling off the light-side release film of the sheet for resin film formation according to any one of claims 1 to 5 and attaching the exposed resin film-forming film to a workpiece;
A step of peeling off the heavy release film from the resin film-forming film attached to the workpiece; and
A method for processing a workpiece, comprising a step of confirming the peeling of a heavy release film.

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