JP2000164767A - Wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which is equipped with a via hole conductor of high connection reliability. SOLUTION: An insulating film that contains organic resin is formed as thick as t, a releasing film 6 and an adhesive layer 7 are formed 0.15 t larger in thickness than t on one surface of the insulating layer, a sheet or a plate 11 which reflects a laser beam is provided on the underside of the insulating film, the insulating film is irradiated with a laser beam through the intermediary of the releasing film 6 and the adhesive layer 7, a via hole is bored by the incident and reflected light of the laser beam, conductive material is filled into the via hole, the releasing film 6 and the adhesive layer 7 are peeled off, and a conductor circuit layer is formed on the surface of the insulating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board such as a package for accommodating a semiconductor device and a method for manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION In recent years,
With the development of portable information terminals and the spread of so-called mobile computing in which a computer is brought in and operated, a small, thin, and high-definition wiring board tends to be required.

Conventionally, as a wiring substrate used for a package for housing a semiconductor element, for example, a ceramic substrate capable of high-density wiring has been widely used. This multilayer ceramic wiring board is composed of an insulating substrate such as alumina, and a wiring conductor made of a high melting point metal such as W or Mo formed on the surface thereof. The semiconductor element is housed in the housing, and the recess is hermetically sealed by a lid.

[0004] However, since the ceramics constituting the insulating substrate of such a ceramic wiring board has a hard and brittle property, it is difficult to use the ceramics in a manufacturing process or a transporting process.
Chipping and cracking of the ceramics are liable to occur, and the hermeticity of the sealing of the semiconductor element may be impaired, resulting in problems such as low production yield. Further, since firing shrinkage is caused by firing at a high temperature, there is also a problem that deformation such as warpage or dimensional variation is likely to occur in the obtained substrate.

Therefore, recently, a fine circuit is formed by etching on the surface of an insulating substrate containing an organic resin to which a copper foil is adhered, and thereafter, this substrate is laminated to form a multilayered printed circuit board, such as copper or the like. A paste containing metal powder is printed on an insulating layer to form a wiring layer, and then laminated, or after lamination, a via hole is formed at a desired position by microdrilling or punching, and a metal is formed in the via wall by plating. There has been proposed a printed wiring board having a multilayer structure by attaching wiring layers and connecting wiring layers.

In such a printed wiring board,
To increase the strength, an insulating substrate in which a spherical or fibrous inorganic material is dispersed in an organic resin has also been proposed. Further, in order to reduce the size of the wiring board, it is required to reduce the diameter of the via-hole conductor, to arrange the via-hole conductor at an arbitrary position, or to make the wiring finer or multilayer.

In response to such demands for printed wiring boards, recently, via holes have been formed in each of the insulating layers, and the via holes have been filled with a conductive paste containing a low-resistance metal powder to form multilayered via hole conductors. A wiring board with wiring has been prototyped.

However, in the method of forming a hole using a microdrill or punching, the diameter of the drill or the punch is at least about 0.15 mm, which is not suitable for required fine processing. In particular, when micro-drilling or punching is used to make holes in an insulating layer in which a fibrous inorganic material is dispersed in an organic resin, if the diameter of the via hole becomes smaller, the drill or punching pins may be used during drilling. There was a problem that it broke in between and broke.

It has also been proposed to form a via hole by irradiating a laser beam. When a via hole is formed by irradiating a laser beam, the diameter of the laser beam can be arbitrarily adjusted by controlling the diameter of the laser beam, which is very advantageous for forming a fine via hole.

However, when irradiating a laser beam, since the laser beam is condensed by an f-θ lens or the like and irradiates the wiring substrate, the shape of the via hole is such that the hole diameter on the surface of the insulating layer on the laser beam incident side is small. It is large and the hole diameter on the emission side is small. That is, a large difference occurs between the diameters of the via holes on both surfaces of the insulating layer. When filling the via hole with a conductive substance, if the hole diameter on the emission side is adjusted to the design value, the hole diameter on the incidence side will be larger than the design value, and in some cases, a short circuit will occur between adjacent via hole conductors. However, there is a problem that a short circuit between circuit patterns may be caused. On the other hand, when the diameter of the hole on the incident side is adjusted to the design value, the diameter of the hole on the emission side is reduced, the contact area with the wiring layer is reduced, and there is a problem that the resistance increases and the conduction is poor.

When the insulating layer is composited with fibers, glass cloth, or the like, the hole diameter and shape of the via hole are greatly affected by the density of the composite material in the insulating layer, and a uniform via hole cannot be formed. Filling such a via hole with a conductive substance causes poor filling of the conductive substance or poor contact with the wiring layer in a portion with a small hole diameter, and a short circuit between adjacent via holes if the hole diameter is too large. There was a problem that caused.

Therefore, the present invention improves the dimensional accuracy of via holes formed in an insulating layer, enables fine wiring and is highly reliable, and is suitable for a portable information terminal or a mobile computer. It is intended to provide a manufacturing method.

[0013]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, the present inventor has found that in the step of forming a via hole by irradiating a laser beam, a laser beam of metal or the like is applied to the laser beam emitting side of the insulating layer. Lay a sheet or plate made of a reflective material and reflect the laser light on this sheet or plate to irradiate the reflected light to the back side of the insulating layer,
The present inventors have found that by processing the via hole shape in a drum shape, a highly reliable via hole having no variation in the via hole shape and no contact failure or short circuit failure with the conductive material is formed, and the present invention has been accomplished.

That is, in the wiring board of the present invention, a via hole is formed in an insulating layer containing at least an organic resin, and a conductive substance is filled in the via hole to form a via hole conductor, and the via hole conductor is electrically connected to the via hole conductor. The via hole is formed in a drum shape in a wiring board having a conductive circuit layer formed on the surface of the insulating layer as described above.

Further, in the method for manufacturing a wiring board according to the present invention, a release film and an adhesive layer are provided on at least one surface of an insulating layer containing an organic resin and having a thickness t so that the total thickness of the insulating layer is Forming a sheet having a thickness t of 0.15 t or more, laying a sheet or plate reflecting laser light on the lower surface of the insulating layer, and forming a laser beam on the insulating layer via the release film and the adhesive layer. Irradiating, the step of forming a via hole with the incident light and reflected light of the laser light, the step of filling a conductive substance in the via hole, the step of peeling off the release film and the adhesive layer, A conductor circuit layer is formed on the surface of the insulating layer.

Further, it is desirable that the sheet or plate reflecting the laser beam is made of any one of copper, silver, aluminum and stainless steel.

Further, the thickness of the adhesive layer is 2 to 30.
μm, the total thickness of the release film and the adhesive layer is 1
Desirably, it is 2 to 130 μm.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG. FIG. 1 is a schematic diagram illustrating an example of a wiring board according to the present invention. As shown in FIG.
Via holes 8 are formed in insulating layer 2 containing at least an organic resin.
And a conductive substance is filled in the via hole 8 to form the via hole conductor 4.
A conductive circuit layer 3 is formed on the surface of an insulating layer 2 so as to be electrically connected to the insulating layer 2.

The insulating layer 2 is made of a material containing at least an organic resin, such as an epoxy resin, a triazine resin, a polybutadiene resin, a phenol resin, a fluorine resin, or a polyimide resin. The resin to be used is used. In particular, PPE (polyphenylene ether), BT resin (bismaleimide triazine), epoxy resin, polyimide resin, fluororesin, phenol resin, and polyamide bismaleimide resin are desirable. It is desirable that the thermosetting resin be as follows.

An organic resin obtained by impregnating the above organic resin with glass fiber as a reinforcing material is also preferably used. At this time, the glass fiber is desirably contained as a woven or nonwoven fabric. In particular, in order to form a uniform via hole 8, it is preferable that a part of fibers of the woven fabric is loosened and defibration is performed to make the thickness of the woven fabric uniform. Further, it is desirable that glass fibers be contained in the insulating layer at a ratio of 30 to 70% by volume.

Further, in order to increase the strength of the insulating layer 2,
An inorganic filler can be added to the organic resin. As the inorganic filler, SiO ₂ , Al ₂ O ₃ ,
AlN or the like is preferably used. The filler has an average particle diameter of 20 μm or less, particularly 10 μm or less, and optimally 7 μm or less.
An approximately spherical powder of m or less is used. In some cases, the dielectric constant of the insulating layer 2 can be increased by using a filler having a high dielectric constant. Further, the volume ratio of the organic resin and the inorganic filler is set to 85:15 to 15:
The thermal expansion coefficient of the insulating layer 2 can be adjusted by appropriately mixing them at a ratio of 85.

In the wiring board 1 of the present invention, it is important to make the hole diameters of the end faces on both sides of the via hole 8 larger than the center. The condition is that the thickness is 50 μm or more, especially 100 μm.
The via hole 8 having high dimensional accuracy can be formed even in the insulating layer 2 having a diameter of 90 μm or more, and even 150 μm or more.
Even when forming a via hole 8 of not more than m, particularly not more than 80 μm, a via hole with good dimensional accuracy can be formed.

As described above, by increasing the diameter of the via hole at both end surfaces of the via hole 8 from the central portion, the area where the end surface of the via hole 8 contacts the conductive circuit layer 3 is increased, and the short circuit failure of the circuit pattern is reduced. In addition, poor filling of the conductive material is reduced. As a result, the reliability of the wiring circuit is improved, the pitch of the via holes 8 can be reduced, and fine wiring can be achieved.

The via-hole conductor 4 is made of at least one selected from, for example, copper, aluminum, gold, silver and the like.
It is formed from a conductor containing a low-resistance metal powder mainly composed of at least one kind of alloy. As the low-resistance metal, copper or an alloy containing copper is particularly desirable, and the low-resistance metal powder to be filled preferably has an average particle diameter of 0.1 to 10 μm.

In some cases, in addition to the above-mentioned metals, a material obtained by mixing or alloying a high-resistance metal such as a Ni—Cr alloy for adjusting the resistance of the circuit may be used. Further, in order to reduce the resistance, the conductor composition may include a metal having a lower melting point than the low-resistance metal, for example, a low-melting metal such as solder or tin. In addition, a binder and a solvent are added to the via-hole conductor, in addition to the low-resistance metal described above, in order to improve a filling material between metal powders or metal powder.

The conductive circuit layer 3 is formed of a metal foil made of a low-resistance metal such as copper, or a conductor containing a low-resistance metal powder such as copper, aluminum, gold, or silver. On lowering the resistance,
It is desirable to be composed of metal foil.

Further, the insulating layer 2 can be laminated to form a multilayer wiring board. As for the configuration of the multilayer wiring board, it is desirable to use a glass fiber-containing insulating layer from the viewpoint of improving the strength of the board. In this case, an organic resin or an inorganic It is desirable to use a filler-added organic resin.

This is because the glass fiber impregnated organic resin has a water absorption of 0.2% and the water impregnated with aramid fiber has a water absorption of 2 to 3%. When the organic resin is held in a humid atmosphere for a long time, moisture diffuses into the interface between the glass fiber and the resin, and the conductive circuit layer 3 is oxidized. It is desirable to use a resin. The thickness of the outermost layer is 10 to 300.
μm, particularly preferably 40 to 100 μm.

Next, a method of manufacturing a wiring board according to the present invention will be described with reference to FIG.
It will be described based on. First, the adhesive layer 7 is provided on one surface of the prepreg 5 (FIG. 2A) in the uncured state or semi-cured state (B-stage state) of the insulating layer 2 made of the organic resin described above. The film 6 is adhered (FIG. 2B). The reason why the laser processing is performed on the prepreg 5 in the B-stage state is that the resin component in the uncured state is more easily decomposed and the laser processing can be easily performed. In order to enhance the effect of the release film, it is desirable to set the degree of cure of the prepreg 5 such that the decomposition temperature of the prepreg 5 by laser irradiation is lower than the decomposition temperature of the release film by laser irradiation. .

When forming the glass fiber impregnated prepreg 5, a solvent such as toluene, butyl acetate, methyl ethyl ketone, isopropyl alcohol, or methanol is added to the above-mentioned organic resin to prepare an organic resin slurry having a viscosity of 100 to 3000 poise. I do. A woven or non-woven fabric of, for example, E glass or S glass is immersed in the produced organic resin slurry to impregnate the glass with the organic resin. afterwards,
Heat and dry at 40-100 ° C for 0.5-5 hours. Also,
It is desirable that the glass fibers in the prepreg 5 have high dispersibility in order to prevent the hole shape from becoming non-uniform due to different decomposition and evaporation temperatures of the glass fiber and the resin during laser processing. Further, a commercially available prepreg may be used for the prepreg 5.

When the prepreg 5 is formed from an organic resin sheet containing an inorganic filler, the organic resin or a composition comprising the organic resin and the inorganic filler is sufficiently mixed by means such as a kneader or a three-roll machine. This is formed into a sheet by a rolling method, an extrusion method, an injection method, a doctor blade method or the like, and then the organic resin is semi-cured. For semi-curing, if the organic resin is a thermoplastic resin, cool the mixture mixed under heating, and if it is a thermosetting resin, heat it to a temperature lower than the temperature sufficient for complete curing. Good.

As the release film 6, a film that can be formed into a sheet, such as PET, polyethylene, polycarbonate, and acrylic, can be used. In particular, PET and polyethylene can be suitably used.

The adhesive layer 7 may be an ordinary adhesive such as an acrylic or epoxy adhesive, or a type of adhesive that loses its tackiness when irradiated with ultraviolet light. Further, the thickness of the adhesive layer 7 is desirably 2 to 30 μm. This is because if the adhesive layer 7 is absent or thinner than 2 μm, the adhesion between the insulating layer 2 and the release film 6 deteriorates. This is because deterioration and deformation (smear) occur in the peripheral part of the irradiation part. Further, the thickness of the adhesive layer 7 is 30
When the thickness is greater than or equal to μm, the adhesive layer 7 partially remains on the insulating layer 2 when the release film 6 is peeled from the insulating layer 2, and the adhesive layer 7 remaining when the resin is cured remains as carbon, and This is because, when the substrate is multilayered, it causes lamination failure.

The total thickness of the release film 6 and the adhesive layer 7 is desirably 12 to 130 μm. 12μ thick
If the thickness is less than m, the effect of the release film is not sufficiently exhibited during laser processing.
If the thickness is larger than m, it is difficult to form holes in the release films 6 and 7. In order to improve the productivity, the total thickness of the release film 6 and the adhesive layer 7 is preferably 100 μm or less, more preferably 50 μm or less.

Next, the prepreg 5 to which the release film 6 has been adhered has a diameter of 0.05 to
A via hole 8 of about 0.3 mm is formed (FIG. 2).
(C)). At the time of performing the laser processing, as shown in FIG. 3, a hole 10 which is about 1 to 6 times larger than the via hole is previously formed in the sample support 9, and the position where the via hole 8 is formed is directly above the hole 10. The prepreg 5 is placed. A sheet or plate 11 made of a material that reflects laser light is laid under the support 9. By reflecting the laser beam that has passed through the via hole formed by the reflecting plate 11, the backside of the prepreg 5 is also processed, and the hole diameter on the backside is 0.8 to 1.0 times that of the front side. A drum-shaped via hole 8 having a concave central portion can be formed.

The sheet or plate 11 for reflecting the laser beam is desirably one of copper, aluminum, stainless steel, silver, gold and the like. Stainless steel can be suitably used.

As a laser used for forming the via hole 8, a known laser such as a carbon dioxide laser, a YAG laser, or an excimer laser can be used. In particular, when reflected by a metal, the reflected light passes through the insulating layer 2. A carbon dioxide laser having sufficient energy to be processed is preferable.

Next, as shown in FIG. 5D, the via holes 8 thus formed are filled with a conductive paste to form via-hole conductors 4. The conductor paste is prepared by adding 0.1 to 5 parts by weight of an organic resin such as epoxy or cellulose, and a solvent such as butyl acetate, isopropyl alcohol, octanol, terpineol, toluene, or xylene to 100 parts by weight of the low-resistance metal powder described above. It is desirable that the composition be 4 to 10 parts by weight. In some cases, after filling the via-hole conductor 4, a heat treatment may be performed at 60 to 140 ° C. to decompose and volatilize and remove the solvent and resin components in the paste.

Next, as shown in FIG. 4E, the release film 6 and the adhesive layer 7 are peeled from the prepreg 5.
At this time, the conductor embedded in the release film 6 and the adhesive layer 7 also peels off together with the release film 6 and the adhesive layer 7.

Next, as shown in FIG. 2F, a conductive circuit layer 3 is formed on the surface of the prepreg 5. Conductor circuit layer 3
To form a resist, after attaching a metal foil such as copper to the insulating layer 12 with an adhesive, a resist of a circuit pattern is formed, and unnecessary metal is removed by etching with an acid or the like.
There is a method of attaching a metal foil punched in advance. As another method, a conductor paste is formed on the surface of the insulating layer 12 by screen printing or a photoresist method on a circuit pattern, dried, and then pressed to embed the wiring circuit on the insulating layer surface and adhere to the prepreg 5. Can be formed. In particular, the wiring circuit is plated on a film, glass, or metal plate, a metal foil is formed, the circuit pattern is formed by etching the metal circuit, and the wiring circuit is transferred onto the prepreg 5 while being pressed, so that the wiring circuit is formed on the surface of the insulating layer. It can be formed by embedding. This method is especially useful for multi-layer
This is effective in that lamination failure due to the conductor circuit layer during lamination can be prevented.

Finally, as shown in FIG.
Heat at a curing temperature of about 300 ° C. to completely cure the organic resin of the insulating layer. In the case of a multilayer wiring board,
After the desired number of prepregs 5 in the step (e) are aligned, the layers may be laminated and cured. At this time, as a method of laminating the prepreg 5, as described above, it is preferable that the inner layer is a prepreg containing a glass resin and the outermost layer is a prepreg containing an organic resin or an inorganic filler. Since the inner layer and the outermost layer of the insulating substrate are both bonded in a semi-cured state and are simultaneously cured, the outermost layer containing no glass does not peel off from the inner layer, and a multilayer wiring board is produced. can do.

[0042]

EXAMPLE A glass woven fabric was impregnated with a slurry (solvent toluene) containing a PPE (polyphenylene ether) resin (glass transition point of 165 to 185 ° C. as measured by coefficient of thermal expansion), dried, and dried to a thickness shown in Table 1. A glass fiber impregnated prepreg was prepared. The content ratio was 50% by volume of PPE resin and 50% by volume of glass woven fabric. On one side of this prepreg, an acrylic pressure-sensitive adhesive layer having a thickness shown in Table 1 (thickness t)
The PET film (thickness t1) was bonded via 2).

In order to process the prepreg with a laser via, a 1 mm thick copper foil is laid on the table of the apparatus, an acrylic plate having a thickness of 3 mm is placed on the copper foil, and a hole of 100 μmφ is formed in the same pattern as the prepreg is processed. Was opened.

Then, a prepreg was placed on the acrylic plate, and a carbon dioxide laser was used for the prepreg.
After forming a via hole of 70 μm under the laser irradiation conditions shown in (1) and filling the hole with a copper paste containing copper powder plated with silver to form a via hole conductor, the PET film and the acrylic adhesive layer were peeled off.

On the other hand, polyethylene terephthalate (PE)
T) An adhesive was applied to the surface of a transfer sheet made of a resin to impart tackiness, and a copper foil having a thickness of 12 μm and a surface roughness of 0.8 μm was adhered to one surface. Thereafter, a photoresist was applied and exposed and developed, and then immersed in a ferric chloride solution to remove non-pattern portions by etching to form a conductor circuit layer. The produced conductor circuit layer has a line width of 30 μm.
m, and the distance between the wirings was 30 μm.

Then, a transfer sheet having a wiring pattern formed on the surface of the prepreg was overlapped and pressed, and only the transfer sheet was peeled off to transfer the conductive circuit layer, and the conductive circuit layer was embedded in the prepreg surface.

The obtained prepreg was heated at 200 ° C. for 1 hour under a load of 20 kg / cm ² and completely cured to produce a wiring board.

For the obtained wiring board, the presence or absence of deformation or alteration and the measurement of the hole diameter d1 on one end face side and the hole diameter d2 (d1 ≧ d2) on the other end face side of the via hole are checked using a stereo microscope. went. Table 1 shows the results.

[0049]

[Table 1]

As is clear from the results of Table 1, when a via hole is formed in a mortar shape without using a reflector, a connection failure occurs, but as in the present invention, a via hole is formed using a reflector. In the drum-shaped one, a via hole with high connection reliability was formed to the extent that smear was slightly generated.

[0051]

As described above in detail, according to the wiring board of the present invention, since the via holes are formed in a drum shape, the via holes having a uniform shape can be formed, and the filling of the conductive material with the wiring layer and the formation of the wiring layer can be prevented. Can be prevented, and a short circuit between adjacent via holes can be prevented.

According to the method of manufacturing a wiring board of the present invention, the via hole is formed by the incident light and the reflected light of the laser beam on the insulating layer via the release film and the adhesive layer. Can be formed accurately and easily, and a via hole with high connection reliability can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a wiring board of the present invention.

FIG. 2 is a diagram illustrating a method for manufacturing a wiring board according to the present invention.

FIG. 3 is a diagram illustrating a method of supporting porcelain when forming a via hole in a wiring board according to the present invention.

[Explanation of symbols]

1: wiring board, 2: insulating layer, 3: conductor circuit layer, 4: via hole conductor, 5: prepreg, 6: release film,
7: adhesive layer, 8: via hole, 9: support, 10: hole,
11: reflector, 12: transfer sheet

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[Procedure amendment]

[Submission Date] September 17, 1999 (1999.9.1)
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

That is, according to the wiring board of the present invention, a via hole is formed in an insulating layer containing at least an organic resin, and a conductive material containing a low-resistance metal powder is filled in the via hole to form a via-hole conductor. In a wiring board having a conductor circuit layer formed on the surface of the insulating layer so as to be electrically connected to a conductor, the via hole is formed in a drum shape, and the wiring circuit layer is formed by being embedded in the surface of the insulating layer. It is characterized by becoming.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

Further, in the method for manufacturing a wiring board according to the present invention, a release film and an adhesive layer are formed on one surface of an uncured or semi-cured insulating layer having a thickness t containing at least an organic resin. The total thickness is 0.1 of the thickness t of the insulating layer.
A step of forming so as to be 5t or more, and irradiating the insulating layer with laser light via the release film and the adhesive layer by laying a sheet or plate reflecting laser light on the lower surface of the insulating layer, A step of forming a via hole with the incident light and the reflected light of the laser light, and a step of filling a conductive paste containing a low-resistance metal powder in the via hole,
The method is characterized in that a step of peeling off the release film and the adhesive layer and a step of embedding a conductor circuit layer in the surface of the insulating layer on the surface of the insulating layer by a transfer method.

Claims (4)

[Claims] 1. A via hole is formed in an insulating layer containing at least an organic resin, and a conductive substance is filled in the via hole to form a via hole conductor, and the insulating layer is electrically connected to the via hole conductor. A wiring board, wherein the via hole is formed in a drum shape on a wiring board having a conductive circuit layer formed on a surface thereof. 2. A release film and an adhesive layer are formed on at least one surface of an insulating layer containing an organic resin and having a thickness t such that the total thickness thereof is 0.15 t or more of the thickness t of the insulating layer. Forming and irradiating the insulating layer with laser light via the release film and the adhesive layer by laying a sheet or plate reflecting laser light on the lower surface of the insulating layer, and the incident light of the laser light Forming a via hole with reflected light, filling the via hole with a conductive material, removing the release film and the adhesive layer, and forming a conductive circuit layer on the surface of the insulating layer. And a method for manufacturing a wiring board. 3. The method according to claim 2, wherein the sheet or plate that reflects the laser light is made of one of copper, silver, aluminum, and stainless steel. 4. The thickness of the adhesive layer is 2 to 30 μm, and the total thickness of the release film and the adhesive layer is 12 to 130.
The method of claim 2, wherein the thickness is μm.