JPH08180757A - Method of forming contact - Google Patents

Abstract

(57) [Summary] [Structure] In the laminated body 4 in which the insulating resin layer 1 and the conductive layer 2 are laminated, and the through hole 3 penetrating the insulating resin layer 1 to reach the conductive layer 2, The surface 1a of the layer 1 and / or the inner surface 1b of the through hole 3 is subjected to ozone treatment and / or irradiation with ultraviolet rays 6. After that, the through holes 3 are filled with a metal substance by plating to form contact portions such as the bumps 7. [Effect] The wettability of the surface 1 a of the insulating resin layer 1 and / or the inner surface 1 b of the through hole 3 to be plated with the plating solution is improved. Bump ungrowing and defective growth due to incomplete filling of the plating solution into the through holes, and contact defects such as bump deformation due to bubbles adhering to the vicinity of the through holes 3 on the surface 1a of the insulating resin layer 1. Since the number of defects is extremely reduced, it is possible to form contact parts such as precise bump plating. In particular, when a large number of contact portions are formed per product, the low yield, which has been a problem in the conventional method, is improved, so that a large economic effect can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a contact portion on a processed film used for an anisotropic conductive film, a circuit board, a film carrier or the like.

[0002]

2. Description of the Related Art In recent years, electronic devices have become more multifunctional and smaller and lighter. In the semiconductor field, wiring circuit patterns have been highly integrated and fine patterns with a large number of pins and a narrow pitch have been adopted. For example, it has been attempted to directly mount a semiconductor element on a circuit board or to mount it on a land portion on an external board via a film carrier, an anisotropic conductive film, etc., but to obtain a more reliable electrical connection. Therefore, it is desired to form a contact portion at the connection portion of the circuit board, the film carrier, and the anisotropic conductive film.

In response to such a demand, for example, Japanese Unexamined Patent Application Publication No.
JP-A-129938 discloses that a through hole is formed by irradiating a laser beam in a thickness direction of an insulating resin film on which a conductive pattern is formed, and a metal substance is filled in the through hole by means such as plating. There is disclosed a method for manufacturing a wiring board having a contact portion formed by protruding the metal substance in a bump shape (hereinafter, such a contact portion is particularly referred to as a "bump").

A method for growing bumps in such fine through holes by plating is known. However, since the insulating resin film is made of an organic substance, it has poor wettability with various plating solutions and generally has a property of repelling water. Further, not only the through holes are fine, but also the conductive portion at the bottom of the through holes is deeper than the surface of the insulating resin film, so it is difficult to fill the plating solution into all the through holes during plating. . If the plating solution is not completely filled in the through holes, the bumps will not grow or the growth of the bumps will be poor. Therefore, a product having such holes with no bump growth or poor growth is a defective product.

Further, if the wettability of the insulating resin film surface with the plating solution is poor, bubbles are likely to adhere to the film surface when the laminated film is immersed in the plating solution. Once such bubbles are attached, they cannot be removed even if the flow rate of the plating solution is increased, so even if the plating solution is completely filled in the through holes and the bumps grow, they will be located near the bubbles. Since the bump grows while avoiding air bubbles, defective defects such as deformation of the bump occur.

[0006] In order to reduce defective or defective growth of bumps such as bump undeformation and contact deformation at the time of plating, for example, methanol which has good wettability with an insulating resin is used before being immersed in a plating solution. A method may be adopted in which these solvents are once allowed to flow into the through-holes, for example, by immersing the solvent in the solvent, and then the solvent inside the through-holes is replaced with water.

However, with this method, the probability of holes in which bumps have not grown or defective growth is reduced, but it cannot be completely eliminated. In addition, the manufacturing process becomes complicated, which also increases the manufacturing cost. Especially in the current situation where the number of bumps per product is increasing, this problem has a large impact on the yield and the manufacturing cost. There is a strong demand for suppression.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and is caused by poor wettability between a plating solution and an insulating resin when forming a contact portion, for example, bump plating. Contact parts such as bumps to eliminate defective defects such as bump undeveloped or poor growth, bump deformation, etc. and obtain processed films such as anisotropic conductive films, circuit boards, film carriers, etc. with high electrical connection reliability The purpose is to provide a method of forming a.

[0009]

Therefore, the present inventor has proposed a method of eliminating defects such as bumps not growing due to insufficient wettability of the surface of an insulating resin film and bump deformation when forming bump electrodes by plating. Was repeatedly examined. As a result, it was found that by adding the step of ozone treatment and / or ultraviolet irradiation before bump plating, it is possible to easily prevent defective growth of the bumps and defective growth of the contact portion such as deformation of the bumps, and complete the present invention. Came to do.

That is, according to the present invention, in a laminate having an insulating resin layer and a conductive layer laminated, and having a through hole penetrating the insulating resin layer to reach the conductive layer, the surface of the insulating resin layer is And / or the inner surface of the through hole is treated with ozone and / or
Alternatively, the present invention provides a method for forming a contact portion, which comprises irradiating an ultraviolet ray and then filling the through hole with a metal substance.

The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a laminated body showing a manufacturing process according to the method for forming a contact portion of the present invention, and FIG. 1 (A) is a sectional view of the laminated body before forming the contact portion, and FIG. FIG. 4 is a cross-sectional view of the laminated body after forming the contact portion. In FIG. 1 (A),
The insulating resin layer 1 and the conductive layer 2 are laminated, a through hole 3 penetrating the insulating resin layer 1 in the thickness direction to reach the conductive layer 2 is formed, and a laminated body 4 is formed.

The insulating resin layer 1 in the present invention is not particularly limited in its material as long as it has electrical insulation, but it is preferable that the insulating resin layer 1 has flexibility as well as insulation. , Epoxy resin, urethane resin, polystyrene resin, polyethylene resin,
Thermosetting resins or thermoplastic resins such as polyamide resins, polyimide resins, acrylonitrile-butadiene-styrene (ABS) copolymer resins, polycarbonate resins, silicone resins, fluorine resins, etc.
It can be appropriately selected according to the purpose. Among these resins, a polyimide resin having excellent heat resistance, chemical resistance, and mechanical strength is particularly preferably used.

Although the thickness of the insulating resin layer 1 can be arbitrarily selected, it is usually 5 to 200 μm, preferably the thickness of the insulating resin layer 1 (variation) and the formability of the through holes 3. It is preferable to set it to 10 to 100 μm.

Examples of the method of forming the through holes 3 include mechanical processing, optical processing, chemical etching and the like, but laser processing is preferable from the viewpoints of fine processability, degree of freedom of processing shape, processing accuracy and the like. Specifically, a mask having a hole shape, for example, a circle, a square, or a rhombus is brought into close contact with the surface 1a of the insulating resin layer 1, and an indirect etching method of processing from the top of the mask, a laser beam with a narrowed spot is used as the insulating resin. The surface 1a of the layer 1 is irradiated, or a dry etching method for forming an image of laser light on the surface 1a of the insulating resin layer 1 through a mask is performed. As the laser light to be irradiated, a large irradiation output ultraviolet laser light is preferable, and particularly when dry etching processing using ablation with an ultraviolet laser such as an excimer laser is performed, a high aspect ratio can be obtained and fine processing can be performed. Therefore, it is preferable.

In the through holes 3, the diameter of the through holes 3 is made as large as possible and the pitch between the holes is made as small as possible within a range in which adjacent through holes are not connected to each other, thereby increasing the number of through holes per unit area. It is preferable to reduce the electric resistance of the conductive path. As shown in FIG. 1 (a), it is preferable to set the diameter of the opening 3 a of the through hole 3 to be larger than that of the bottom 3 b, because it becomes easier to irradiate the inner surface 1 b of the through hole 3 with ultraviolet rays. The hole diameter of the opening 3a of
5 to 200 μm, preferably about 8 to 50 μm,
The hole diameter of the bottom portion 3b of the through hole 3 is 3 to 190 μm, preferably about 5 to 45 μm.

The conductive layer 2 is not particularly limited as long as it has conductivity so as to become an electrode (cathode) in electroplating in a manufacturing process described later, and for example, gold, silver,
Single metals such as copper, platinum, lead, tin, nickel, iron, cobalt, indium, rhodium, chromium, tungsten, and ruthenium, or various alloys containing these, for example, solder, nickel-tin, gold-cobalt, etc. Can be mentioned. Further, the conductive layer 2 does not necessarily have to be a single layer, and may have a laminated structure in which two or more layers of each metal described above are laminated.

The thickness of the conductive layer 2 is not particularly limited, but 1
˜200 μm, preferably 5 to 80 μm. A circuit pattern is usually formed on the conductive layer 2. As a method of forming a conductive circuit, a method of directly drawing and forming a target circuit pattern on the other surface 1c of the insulating resin layer 1 (additive method), There is a method (subtractive method) of removing the other part of the conductive layer 2 so as to leave the circuit pattern.

Examples of the former method include drawing a circuit pattern using a film forming method such as sputtering, various vapor depositions, various platings, and the like. As the latter method, the conductive layer 2 is laminated on the other surface 1c side of the insulating resin layer 1, and the resist layer 5 is formed on the surface 2a of the conductive layer 2 so as to cover only the desired circuit pattern shape. Then, the exposed conductive layer 2 may be etched to obtain a desired circuit pattern.

Since it is necessary to insulate the surface 2a of the conductive layer 2 before forming the contact portion by plating,
As shown in (A), a resist layer 5 is provided as insulation protection. The material of the resist layer 5 is not particularly limited as long as it can be insulated.

Next, modification of the surface 1a of the insulating resin layer 1 and / or the inner surface 1b of the through hole 3 by ozone treatment and / or ultraviolet irradiation will be described.

Ultraviolet rays are a type of electromagnetic wave, and the wavelength thereof is shorter than that of visible light, and those having a wavelength range of 100 to 400 nm are called ultraviolet rays. The energy of light depends on its wavelength, and the shorter the wavelength, the higher the energy. In order for an electromagnetic wave to act on a substance, enough energy is required to cause a reaction. The energy of ultraviolet light is much higher than that of infrared light and visible light. The binding energy of organic compounds is close to that of ultraviolet rays, and ultraviolet rays in the short wavelength region are higher than those of many organic compounds. This is the reason why ultraviolet rays can react with many substances in various ways.

When an organic material such as an insulating resin is irradiated with ultraviolet rays, polymer bonds are broken within a range of a depth of several microns from the surface. At the cleavage site, by extracting a hydrogen atom and then introducing an oxygen atom, a highly polar functional group such as a carbonyl group, a carboxyl group, and a hydroxyl group is formed, and as a result, the surface energy increases,
The contact angle of water is reduced and the wettability is improved.

Although there are many kinds of ultraviolet light sources, a low-pressure mercury lamp is preferable because it efficiently emits short-wavelength ultraviolet light effective for reacting with organic substances and has a long life and is practical. Typical ultraviolet wavelengths emitted by a mercury lamp are 365 nm, 254 nm and 185 nm, but a low-pressure mercury lamp is a lamp that emits the 254 nm line and the 185 nm line most efficiently. In the present invention, as long as the lamp emits ultraviolet rays of 185 nm line and / or 254 nm line, it is not limited to the low pressure mercury lamp,
It can be preferably used.

The 185 nm line can decompose oxygen molecules to generate ozone as shown in the following formula. However, ozone has a strong absorption band in the vicinity of 260 nm, so that ozone is decomposed by the 254 nm line and rapidly releases active oxygen atoms (equation).

O ₂ + hν (185 nm) → O + O O ₂ + O → O ₃ O ₃ + hν (254 nm) → O ₂ + O

The active oxygen atom decomposed and generated from ozone has a strong oxidizing power, and reacts with a free radical or an excited state molecule of an organic compound produced by, for example, irradiation with ultraviolet rays to produce CO ₂ or H ₂ It produces a volatile substance such as O or a compound having a highly polar functional group such as a carbonyl group, a carboxyl group, and a hydroxyl group.
Since the amount of organic matter decomposed and removed depends on the ozone concentration and the amount of exposure to ultraviolet rays, it is particularly preferable to use both of them together rather than to perform ultraviolet irradiation or ozone treatment alone.

Regarding the ozone concentration, for the purpose of improving the wettability of the surface 1a of the insulating resin layer 1 and / or the inner surface 1b of the through holes 3, the ozone concentration of ozone generated by ultraviolet rays emitted from a low pressure mercury lamp or the like is used. It is possible to increase the ozone concentration by using an ozone generator or the like to further increase the ozone concentration. The specific ozone concentration in this case is usually 100 to 100.
It is preferable to set it in the range of 0 ppm, preferably 200 to 600 ppm, and more preferably 400 to 500 ppm. If the ozone concentration is less than 100 ppm, the effect is insufficient, while if it exceeds 1000 ppm,
It is uneconomical because the contact angle has already reached the limit of decrease.

However, like dry desmear, the opening 3a and the bottom 3b of the through hole 3 are formed by laser processing or the like.
When there is a large amount of the decomposed product adhering to and removed by etching, it is necessary to increase the ozone concentration by using an ozone generator that generates ozone using oxygen gas as a raw material. The specific ozone concentration in this case is usually 2000 to 100.
The concentration is set to 00 ppm, preferably 3000 to 6000 ppm, and more preferably 4500 to 5500 ppm. If the ozone concentration is less than 2000 ppm, a decrease in the amount of decomposition products is observed, but it cannot be completely removed. On the other hand, even if the ozone concentration exceeds 10000 ppm, the decomposition products have already been completely removed, which is uneconomical. Is.

For the purpose of improving the wettability of the surface 1a of the insulating resin layer 1, the ambient temperature is usually room temperature or higher, preferably 15 to 45 ° C., more preferably 20 to.
When the temperature is set to 30 ° C. and the purpose is to remove adhered decomposed substances by etching, it is usually 70 to 170 ° C., preferably 90 to
The temperature is set to 150 ° C, more preferably 100 to 120 ° C.

The present invention applies the modifying action of the organic substance by the ozone treatment and / or the ultraviolet irradiation to the pretreatment for forming the contact portion with the plating solution. Unlike the conventional modification with a liquid, the active oxygen of the active substance is a gas, and the ultraviolet rays on the other hand are light, so that the insulating resin layer 1
It is effective for improving the wettability and removing the decomposed products by laser processing or the like with respect to any fine through-holes formed in the.

Next, a method of forming a contact portion with a plating solution will be described. The surface 1a of the insulative resin layer 1 of the laminate 4 which has been protected by the resist is irradiated with ultraviolet rays 6 at an intensity of 1 to 5 mW / cm ² , preferably ² to 3 mW / cm ² .
The irradiation time is usually 5 to 30 minutes, preferably 10 to 20 minutes. However, when the purpose is to remove adhered decomposition products by etching, the intensity of the ultraviolet rays 6 is usually 20 to 80 mW / cm.
² , preferably 30 to 70 mW / cm ² , more preferably 40 to 50 mW / cm ² , and the irradiation time is usually 5 to 3
It is set to 0 minutes, preferably 10 to 20 minutes.

Since it is sufficient to set the ozone concentration in the range of 1000 ppm or less as long as it is a modification treatment for improving the wettability, an ozonizer is not particularly required, and ozone naturally generated by ultraviolet irradiation is used. Will be done. It takes about 5 minutes after the lamp is turned on for the ozone concentration to reach 100 ppm or more, although there is a difference depending on the device.

After irradiation, the contact angle of the surface 1a of the insulating resin layer 1 decreases, but the contact angle gradually returns if the standing time is long, so it is preferable to perform plating as soon as possible.

The material of the plating solution is not particularly limited as long as it is a conductive metal, and the same material as that of the conductive layer 2 can be used. In the present invention, various metal plating can be used. In electroplating, the conductive layer 2 is connected to an electrode, the laminate 4 is immersed in a plating bath, and the conductive layer 2 is used as a cathode to conduct electricity. The current density at this time varies depending on the metal to be plated, but when plating nickel, for example,
Set to ³ to 8 A / dm ² . By energizing, the through hole 3 is filled with a metal substance to form a contact portion.

In the present invention, the contact portion is an electrical contact,
It is a conductor portion provided on the surface 1a of the insulating resin layer 1 for the purpose of connection. The aspect of the contact portion as a whole does not matter whether or not there is a protrusion from the surface 1a of the insulating resin layer 1, and the shape of the contact surface of the contact portion is a convex shape depending on the protruding state of the member to be contacted, It may be flat or concave. Therefore, the cross-sectional shape of the contact portion when cut in a plane parallel to the surface 1a of the insulating resin layer 1 is not limited, and all polygons, circles, ellipses, a part of each of these shapes, The shape of the contact point can be any three-dimensional shape such as the end or side of a polygonal column or a cylinder, a cone (stand), a pyramid (stand), or a part of a sphere, depending on the combination of these cross-sectional shapes. Is possible. However, as shown in FIG. 1B, it is preferable that the contact portion is a mushroom-shaped (bump-shaped) bump 7 from the viewpoint of electrical reliability. The height of the bump 7 can be freely set according to the purpose and use.

Since the drying process is usually required to form the resist layer 5 for insulating the surface 2a of the conductive layer 2, the exposed surface of the conductive layer 2 at the bottom 3b of the through hole 3 is required. 2b is oxidized. When the oxide film is formed on the exposed surface 2b of the conductive layer 2, the current flow becomes poor, resulting in bump non-growth or poor growth. Therefore, it is necessary to perform a pretreatment for the purpose of removing the oxide film immediately before plating. The pretreatment agent for removing the oxide film is not particularly limited as long as it can remove the oxide film, for example, if the removal of copper oxide, a soft etching agent [Ebara Eugelite Co.,
PB-228 (100 g / L) / sulfuric acid (10 mL / L)
Is preferably used. When removing the oxide film, ultrasonic vibration is preferably used together, and the laminate 4 is immersed for 1 to 3 minutes to activate the exposed surface 2b of the conductive layer 2 at the bottom 3b of the through hole 3.

Finally, the resist layer 5 for insulation protection is peeled off from the conductive layer 2 to obtain the laminated body 4 having the bumps 7 as contact portions.

[0038]

According to the method of forming a contact portion of the present invention, the surface of the insulating resin layer and / or the inner surface of the through hole formed in the insulating resin layer is subjected to ozone treatment and / or ultraviolet irradiation. The surface of the insulating resin layer and / or the inner surface of the through hole to be plated has improved wettability with the plating solution.
Therefore, the bumps do not grow because the plating solution is not completely filled in the through holes, the bumps do not grow well due to insufficient filling of the plating solution into the through holes, and bubbles during the plating process may cause bubbles in the insulating resin layer. The defect defect of the contact portion such as the bump deformation due to the adhesion to the vicinity of the through hole on the surface is eliminated, so that the yield is greatly improved.

[0039]

The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Example 1] A two-layer laminated body in which a copper layer (35 µm thick) made of a copper foil, which is a conductive layer, is formed on one surface of a polyimide film (26 µm thick) which is an insulating resin layer. I made a film. KrF with an oscillation wavelength of 248 nm is passed through the shielding mask on the surface of the polyimide film.
Dry etching was performed by irradiating an excimer laser beam, and 9900 fine through holes having a diameter of 30 μm were formed only in the polyimide film.

A black polyimide decomposed product was attached to the periphery of the opening and the bottom of the through hole. This decomposed product contains carbon as a main component and acts as a conductor during plating. Therefore, when electrolytic plating, especially when forming bumps, unless the decomposed product is completely removed, it directly leads to defective bump shape. . Generally, as a method for removing these decomposed products, a wet desmear method using potassium permanganate is known. However, when the pores are fine as in this example, all the pores are easily affected by the liquid flow. It is difficult to uniformly remove the attached decomposition products of.

Then, as an application of the method of the present invention, dry desmear using ultraviolet rays and ozone was performed, and the attached polyimide decomposed substance could be removed. Specifically, using a high-power type deep UV application device (manufactured by Nippon Battery Co., Ltd., photo surface modification device DUV150-1), the polyimide surface of the two-layer film was irradiated with UV light at an intensity of about 40 mW / cm ² for 20 minutes. At this time, the ozone concentration in the atmosphere is about 400.
It was 0 ppm and the ambient temperature was 100 ° C. Regarding the dry desmear conditions, when the temperature is room temperature, the ozone concentration is less than 2000 ppm, or the irradiation time is less than 10 minutes, a decrease in the amount of decomposed products is observed, but it cannot be completely removed. could not.

After the treatment, when the shape of the through hole was observed,
The diameter of the through hole on the surface of the polyimide is 30.
μmφ, the diameter at the interface between the polyimide and the copper layer (bottom of the through hole) was 20 μmφ, and the depth of the hole was 26 μm. The contact angle with water on the surface of the polyimide was 74 ° before the treatment and 26 ° after the treatment.

A vinyl chloride-based ink resist was applied to the surface of the copper layer of the two-layer film thus obtained,
It was cured at 0 ° C. for 30 minutes for insulation. The contact angle after heating and drying had risen to 65 ° C.

Next, an ultraviolet-ozone cleaning machine (manufactured by Nippon Battery Co., Ltd., portable type optical surface modification device DUV-25 × 4A)
185n on the polyimide surface of the two-layer film using
m and 254 nm ultraviolet rays were radiated for 10 minutes to make an ozone atmosphere. The ozone concentration at this time is about 500 pp
It was m.

The contact angle with water after the treatment was lowered to 28 °. The lower the contact angle, the better the wettability with water, and as a result, the bump ungrowing and the growth failure and the bump deformation decrease, but the wettability can be maintained for a limited period of time in an air atmosphere for 24 hours. After that the contact angle rises to 48 ° C. Therefore, by performing bump plating as soon as possible after the irradiation of ultraviolet rays, the effects of the present invention can be fully utilized. In the present example, the standing time from the irradiation of ultraviolet rays to the plating was 30 minutes.

Since the copper surface at the bottom of the through hole was oxidized due to the above-described ink resist drying step, a pretreatment for removing the copper oxide film was performed immediately before plating. If the pretreatment agent can remove copper oxide,
Although not particularly limited, in the present embodiment, a soft etching agent [PB-228 (manufactured by Ebara-Udylite Co., 100 g /
L) / sulfuric acid (10 mL / L) mixed solution], the two-layer film was immersed for 1 minute while also using ultrasonic vibration to activate the exposed copper layer at the bottom of the through hole.

After washing this with pure water, the copper layer was connected to an electrode and immersed in a nickel bath at 60 ° C., and the copper layer was used as a negative electrode to grow nickel plating in the through hole. The current density was set to 5 A / dm ² , and the plating treatment was terminated when nickel was projected from the polyimide film surface by 20 μm.

Finally, the coated resist layer is peeled off,
A two-layer film with nickel bumps was obtained. When all the bumps of this two-layer film were observed with a microscope, there was no bump missing or bump defect defect.

Comparative Example 1 The same operation as in Example 1 was carried out except that the ultraviolet irradiation in the ozone atmosphere immediately before bump plating in Example 1 was omitted. As a result, 9
Bumps did not grow in 84 of the 900 holes.

Comparative Example 2 Example 1 was repeated except that the ultraviolet irradiation in the ozone atmosphere immediately before bump plating was omitted and the conventional methanol substitution method was used instead.
The same operation was carried out. As a result, bumps did not grow in three of the 9,900 holes.

[0052]

According to the method of forming the contact portion of the present invention, the surface of the insulating resin layer and / or the inner surface of the through hole formed in the insulating resin layer is subjected to ozone treatment and / or ultraviolet irradiation. Therefore, the wettability with the plating solution is improved on the surface of the insulating resin layer and / or the inner surface of the through hole to be plated. Therefore, the bumps do not grow because the plating solution is not completely filled in the through holes, the bumps do not grow well due to insufficient filling of the plating solution into the through holes, and bubbles during the plating process may cause bubbles in the insulating resin layer. Since defective defects of the contact portion such as bump deformation due to the adhesion to the vicinity of the through hole on the surface are extremely reduced, the contact portion can be precisely formed by bump plating. In particular, when a large number of contact portions are formed per product, the low yield, which has been a problem in the conventional method, is improved, so that a large economic effect can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a laminated body showing a manufacturing process according to a method of forming a contact portion of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating resin layer 1a Surface 1b Inner surface 2 Conductive layer 3 Through hole 4 Laminated body 6 Ultraviolet ray 7 Bump (contact part)

Claims (4)

[Claims] 1. A laminate in which an insulating resin layer and a conductive layer are laminated, and which has a through hole penetrating the insulating resin layer and reaching the conductive layer, the surface of the insulating resin layer and / or the A method of forming a contact portion, which comprises subjecting an inner surface of a through hole to ozone treatment and / or ultraviolet irradiation, and then filling the through hole with a metal substance. 2. The method according to claim 1, wherein the ultraviolet irradiation is performed in the presence of ozone. 3. The method according to claim 1, which comprises irradiating with ultraviolet rays having a wavelength of 185 nm and / or 254 nm. 4. The method according to claim 1, wherein the ozone concentration is 100 to 1000 ppm or 2000 to 10000 ppm.