JPH10195668A - Production of two-layer flexible substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defectless two-layer flexible substrate free from wiring part defect caused by pin holes and excellent in adhesive property of an under metallic layer to an electroless plated film in a two-layer flexible wired board production by applying dry plating method, electroless plating method and electric copper plating method on the substrate. SOLUTION: The under metallic layer is formed directly on one surface or both surfaces of an insulating material film without interposing an adhesive layer and a copper conductive layer having a prescribed thickness is formed on the under metallic layer. The under metallic layer is composed of a coating layer formed by dry plating method using at least one kind selected from a group composed of nickel, a copper-nickel alloy, chromium and chromium oxide and a copper coating film layer formed on the coating film layer by dry plating method. Next, after a primary electric copper plated film layer is formed on the under metallic layer, an electroless copper plated film layer is formed as an intermediate metallic layer on the primary electric copper plated film layer and the copper conductive layer having 5-18μm thickness is formed on the insulating material film finally by forming a secondary electric copper plated film layer on the intermediate metallic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a two-layer flexible substrate, and more specifically, to a method for manufacturing a copper conductor by employing a dry plating method, an electroless copper plating method and an electrolytic copper plating method on an insulating film. The present invention relates to a method for manufacturing a two-layer flexible substrate which can easily form a conductor layer having higher soundness and higher adhesion when forming a layer.

[0002]

2. Description of the Related Art A substrate used for manufacturing a flexible wiring board is composed of a three-layer flexible substrate in which a copper foil serving as a conductor layer is bonded on an insulating film using an adhesive, and a three-layer flexible substrate is formed on the insulating film. It is roughly classified into a two-layer flexible substrate in which a copper conductor layer is directly formed by a dry plating method or a wet plating method without using an adhesive.

When a three-layer flexible substrate is used, a three-layer flexible wiring board can be manufactured by forming a desired wiring pattern on a substrate by a subtractive method. The two-layer flexible wiring board can be manufactured by forming a desired wiring pattern on a substrate by a subtractive method or an additive method. However, in general, the manufacturing method is simple and can be manufactured at low cost. The use of a three-layer flexible substrate that can be used has been dominant.

[0004] With the recent increase in the density of electronic devices, wiring boards having a narrower wiring width have been required. However, in the case of a three-layer flexible wiring board, when forming a wiring part by etching a copper conductor layer formed on an insulating film of a substrate,
Since the side surface of the wiring portion is etched, so-called side etching occurs, the cross-sectional shape of the wiring portion tends to be a trapezoid with a wide skirt. Therefore, if the etching is performed until the electrical insulation between the wiring portions is secured, the wiring pitch width Becomes too wide, so that 35 μm conventionally used generally is used.
As long as a substrate to which a copper foil having a thickness of m is bonded is used, there is a limit in reducing the pitch of the wiring portion in the wiring board.

For this reason, a thin copper foil bonded substrate having a thickness of 18 μm or less is used in place of the conventional copper foil bonded substrate having a thickness of 35 μm, the width of the skirt spread by side etching is reduced, and the narrow pitch of the wiring portion in the wiring board is reduced. Attempts were made to make it more sophisticated. However, such a thin copper foil has low rigidity, and thus has poor handling properties. Therefore, after bonding a reinforcing material such as an aluminum carrier to the copper foil to increase the rigidity, bonding the copper foil to an insulating film is performed. After that, the aluminum carrier must be removed again, so that the workability is poor.

[0006] Further, such a thin copper foil has problems in manufacturing technology such as an increase in film defects due to variations in film thickness and generation of pinholes and cracks, and further, the thinner the copper foil, the more it becomes. The production becomes difficult, the production price increases, and the cost advantage of the three-layer flexible wiring board is lost. Especially recently,
The demand for a wiring board having a wiring section with a narrow width and a narrow pitch, which cannot be manufactured without using a copper foil having a thickness of 10 μm or less and about several μm, has become stronger, and a three-layer flexible substrate is used. The wiring board has problems not only in terms of technical problems as described above but also in terms of manufacturing cost.

Accordingly, attention has been paid to a two-layer flexible wiring board using a two-layer flexible substrate capable of forming a copper coating directly on an insulator film without applying an adhesive. The two-layer flexible substrate directly forms a copper conductor layer on an insulator film without an adhesive,
Therefore, there is an advantage that the thickness of the substrate itself can be reduced, and the thickness of the copper conductor film to be applied can be adjusted to an arbitrary thickness. When manufacturing such a two-layer flexible substrate, an electrolytic copper plating method is usually employed as a means for forming a copper conductor layer having a uniform thickness at a low cost on an insulator film. To do so, a thin base metal layer is formed on the insulator film on which the electrolytic copper plating film is applied, and conductivity is imparted to the entire surface,
In general, an electrolytic copper plating process is performed thereon.

In order to obtain a thin base metal layer on an insulator film, it is common to use a dry plating method such as a vacuum deposition method or an ion plating method. In the coating layer obtained by the method, a large number of pinholes having a size of usually several tens μm to several hundreds μm are generated, so that the underlying metal layer often has an exposed portion of the insulator film due to the pinholes. .

Conventionally, in a flexible wiring board of this type, the thickness of a conductive copper film required for wiring is generally 20 times.
Although it was considered that a thickness of about 35 μm was appropriate, when a copper film having such a considerable thickness is to be obtained by an electrolytic copper plating method which is generally performed conventionally, a copper film formed by an electrolytic copper plating method is required. Since the film grows not only in the vertical direction but also in the horizontal direction with respect to the substrate, the defect based on the exposure of the pinhole on the surface of the insulating film is buried in the plating film, and the wiring portion due to the presence of the pinhole is damaged. There were few defects.

However, in order to obtain a flexible wiring board having a wiring section of a narrow pitch as directed in the present invention, as described above, the thickness of the copper film for forming the wiring section is 18 μm or less. Ideally, the thickness should be extremely thin, about 5 μm. Therefore, if an attempt is made to obtain such a thin copper film by the electrolytic copper plating method, the growth amount of the film in the horizontal direction is insufficient, and the above-described pinholes The defect could not be filled, and there was a possibility that a defect might occur in the wiring portion.

[0011] This situation can be solved by, for example, manufacturing a two-layer flexible wiring board by a subtractive method using a two-layer flexible substrate in which a copper conductor layer having a desired thickness is formed on an insulating film on which a base metal layer is formed. To explain the case where the process is performed as an example, the formation of the wiring portion pattern is performed in the following step. (1) A resist layer having a desired wiring portion pattern is provided on the copper conductor layer such that only the wiring portion is masked and the non-wiring portion copper conductor layer is exposed. (2) The exposed copper conductor layer (3) Finally, the resist layer is peeled off. Therefore, using a substrate in which the thickness of the copper conductor layer is extremely thin, for example, 5 μm, the wiring width is 40 μm, and the wiring pitch is 80 μm.
In the case of manufacturing a wiring board having a narrow wiring width and a narrow wiring pitch such as m, among the pinholes formed in the base metal layer of the substrate by dry plating, the coarse ones have a size of several tens μm to 5 to reach the order of several hundred μm
After forming an electrolytic copper plating film with a thickness of about μm,
Since the exposed portion of the insulator film due to the pinhole can hardly be filled, the exposed portion, that is, the missing portion of the conductor layer is applied to the wiring portion, and the wiring portion is missing at the position of the pinhole and becomes a wiring defect, Otherwise, it may cause poor adhesion of the wiring portion.

As a method for solving the above-mentioned problem, a base metal layer is formed on an insulator film by a dry plating method, and a copper coating layer is further provided as an intermediate metal layer by electroless plating to form an insulator by a pinhole. Methods have been proposed for coating exposed portions of the film. But when using this method. Certainly, the exposed portion of the insulator film due to pinholes can be eliminated to some extent, but on the other hand, the plating solution used for the electroless copper plating process and the alkaline pretreatment solution used to perform this process have already been used. It penetrates between the insulator film and the underlying metal layer from the large and small pinholes that are formed, which inhibits the adhesion of the underlying metal layer and, subsequently, the adhesion of the conductor layer formed by the subsequent copper plating. It was not a sufficient solution because it would cause

[0013]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the production of flexible wiring boards using dry plating, electroless plating and electrolytic copper plating, and provides dry plating on an insulating film. Provided is a method for producing a flexible wiring board which is free from copper conductor portions caused by pinholes generated when forming a base metal layer by processing and has excellent adhesion between the base metal layer and the electroless plating layer. It is the purpose.

[0014]

According to the present invention, in order to achieve the above object, an underlayer metal layer is formed directly on one or both sides of an insulating film without using an adhesive, and a desired metal layer is formed on the underlayer metal layer. In the method for manufacturing a two-layer flexible substrate for forming a copper conductor layer having a thickness of at least one selected from the group consisting of nickel, copper-nickel alloy, chromium, and chromium oxide, And a copper layer formed by a dry plating method further formed on the film layer by a dry plating method, and then a primary electrolytic copper plating film layer is formed on the base metal layer. To form an electroless copper plating film as an intermediate metal layer on the primary copper plating film layer, and finally form a secondary copper electroplating film layer on the intermediate metal layer. Insulation film And it is characterized in the manufacturing method of the two-layer flexible substrate forming a 5~18μm copper conductor layer.

In the present invention, the thickness of the primary electroplated copper coating layer formed on the base metal layer is preferably in the range of 0.3 to 10 μm, particularly preferably 0.5 to 2 μm. Also,
The thickness of the electroless copper plating layer is 0.01 to 1.0 μm.
m, particularly preferably in the range of 0.05 to 0.5 μm, and when forming the electroless copper plating film layer, it is preferable to perform a catalyst application treatment as a pretreatment.

In the present invention, nickel, copper-nickel alloy, chromium, and the like are selected from the two base metal layers formed directly on the insulator film by the dry plating method.
The thickness of the coating layer obtained by dry plating at least one selected from chromium oxides is 50 to 2,000.
0 angstrom, and the thickness of the copper dry plating film layer formed thereon is 200 to 5,0
Preferably, it is 00 Å. In addition, as the dry plating method for forming the base metal layer, it is preferable to employ any one of a vacuum deposition method, a sputtering method, and an ion plating method.

[0017]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention uses at least one selected from the group consisting of nickel, copper-nickel alloy, chromium, and chromium oxide on an insulator film by a dry plating method. 2 of the formed coating layer and a copper coating layer further formed on the coating layer by dry plating.
First, a primary electrolytic copper plating layer having a predetermined thickness is formed on a base metal layer composed of a plurality of layers, and then an electroless copper plating layer is further applied thereon, and finally, a secondary electrolytic copper plating layer is formed. Forming a copper conductor layer having a desired thickness by forming a flexible printed circuit board using a dry plating method and an electroless plating method. By using the method described above, it is possible to obtain a two-layer flexible substrate having few conductor defects due to pinholes generated at the time of forming a dry plating film layer and having high adhesion between the conductor layer and the insulator film. .

In the present invention, the reason why the electrolytic copper plating film layer is formed on the substrate in a primary and secondary manner will be described as follows. That is, the plating film layer usually formed on the insulator film by the dry plating method,
Although there are countless large and small pinholes, most of them are minute pinholes of 1 μm or less which are difficult to observe with an optical microscope, and the rest are coarse pinholes of several μm to several hundred μm. The former minute pinholes have almost no effect on the occurrence of defects in the wiring portion when the wiring board is manufactured, but the latter coarse pinholes form an exposed portion of a remarkable size on the insulating film. If the exposed portion is not covered by the electroless copper plating process, the conductor layer formed in the subsequent electrolytic copper plating process will have a partially missing portion, which will cause a wiring defect in manufacturing a wiring board.

According to an experiment conducted by the present inventors,
Since the standard of the allowable limit of the loss of the wiring portion in the wiring board is about 1/4 to 1/3 of the wiring width, for example, the wiring width of 4
In a 0 μm wiring board, the conductor layer formed on the substrate has 1
It has been proved that when there are a large number of partially missing portions due to pinholes having a size of more than 0 μm, a wiring board manufactured from the substrate is likely to be defective.

In addition, the presence of minute pinholes among the above-mentioned pinholes also means that an electroless plating solution or a pre-treatment liquid is used to pass the underlying metal through the holes of the minute pinholes in the subsequent electroless copper plating treatment. It penetrates between the layer and the insulator film and causes the adhesion of the underlying metal layer to be hindered. Therefore, the adhesion strength of the wiring portion in the manufactured wiring board is usually regarded as a practical standard in this type of wiring board.
It was found that the value was lower than kgf / cm, which was not preferable. Therefore, in the present invention, by performing primary electrolytic copper plating on the underlying metal layer, the formed copper plating film layer is used to fill the fine pinholes of the underlying metal layer, and the electroless copper plating in the next step is performed. In the process, the permeation of the electroless plating solution or the pretreatment solution from the fine pinholes into the insulator film is suppressed, and thereby the adhesion of the base metal layer to the insulator film is ensured.

In this case, the reason why the thickness of the primary electrolytic copper plating layer is limited to the range of 0.3 to 10 μm is as follows. Since the surface of the insulator film is largely exposed in the coarse pinhole portion, no copper plating film is formed on the insulator film having no conductivity even when the electrolytic copper plating process is performed. As a result, the thickness of the portion where the primary electrolytic copper plating film is formed is obtained by adding the thickness of the primary electrolytic copper plating film layer to the thickness of the underlying metal layer, and the exposed portion of the insulator film due to the coarse pinholes and the primary electrolytic copper plating A step is generated between the portion where the coating layer is formed and the portion where the coating layer is formed. Since this step does not change even after the formation of the secondary electrolytic copper plating film in the final step, if the thickness of the primary electrolytic copper plating film exceeds 10 μm, the level difference on the surface of the obtained two-layer flexible substrate is extremely large. It becomes too difficult, which hinders the processing of the wiring portion in the subsequent wiring portion forming step. Also, if the thickness of the primary electrolytic copper plating film layer is less than 0.3 μm, the fine pinholes cannot be filled sufficiently, so that the plating solution or the like easily penetrates during the electroless copper plating treatment, and Either case is not preferable because there is a fear that the adhesion of the layer may be reduced.

Incidentally, the thickness of the primary electrolytic copper plating film layer may be set to such a thickness as to fill the holes of the minute pinholes and to prevent the penetration of the plating solution. The thickness is determined in consideration of the thickness of the final conductor layer obtained by performing the subsequent electrolytic copper plating treatment and the size of the wiring width and the wiring pitch of the wiring portion formed on the wiring board. For example, when the thickness of the conductor layer finally formed on the substrate is about 5 μm, and the wiring width of the wiring board manufactured by this is about 40 μm and the wiring pitch is about 80 μm, the adhesion of the underlying metal layer on the substrate is In order to substantially eliminate the difference in level while ensuring the performance, it is ideal that the thickness of the primary electrolytic copper plating layer is set in the range of 0.5 to 2 μm.

Next, an electroless copper plating process is performed. The electroless copper plating film is formed on the entire surface of the substrate by covering the exposed surface of the insulator film by the coarse pinholes by forming an electroless copper plating film layer on the entire surface of the substrate. This is performed so that the secondary electrolytic copper plating process in the next step can be performed over the entire surface of the substrate without being affected by the pinhole. In performing the electroless copper plating treatment, it is preferable to perform a catalyst imparting treatment on the substrate in advance using a known catalyst imparting agent. Thereafter, by performing a secondary electrolytic copper plating treatment, the thickness is easily reduced to 5 to 1 mm.
A thin, sound two-layer flexible substrate having a conductor layer of about 8 μm can be obtained.

In the present invention, the catalytic metal species used in the catalyst application treatment performed in the electroless copper plating treatment may be any one which is more noble in potential than the complexed metal ion species contained in the electroless plating solution. For example, gold, platinum, silver, palladium and the like can be used. However, in consideration of simplicity, palladium-based catalyst-imparting agents that are widely commercially available as catalyst-imparting agents, for example, palladium-tin acidic solutions,
An alkaline palladium complex solution or an acidic palladium solution containing no tin is suitable. The method of applying the catalyst is not particularly limited, and a sensitizing activation method, a catalyst accelerator method, or the like generally used for applying this type of catalyst may be appropriately selected depending on the situation.

The pretreatment for the catalyst application treatment is as follows:
Although not particularly limited, it is desirable to perform a cleaning treatment such as degreasing in order to increase the adhesion between the base metal layer and the insulator film and between the base metal layer and the electroless plating film.
However, it is necessary to strictly avoid processing under such conditions that the copper coating layer formed on the second layer of the base metal layer and the copper coating layer formed by the primary electroplating process are dissolved by this pretreatment.

In addition, the electroless plating solution used in the present invention is a reduced deposition type in which metal ions contained therein have autocatalytic properties and are reduced by a reducing agent such as hydrazine, sodium phosphinate, formalin or the like to deposit metals. Any material may be used as long as the object of the present invention is to make the exposed portion of the insulator film exposed by the pinholes formed in the base metal layer a good conductor. An electroless copper plating solution having a good workability and relatively good workability is optimal.

The thickness of the plating film formed by the electroless copper plating solution is set to such a level that a defect can be repaired by pinholes on the substrate surface and that the plating film is not dissolved by the electrolytic copper plating solution during the electrolytic copper plating treatment. If it is good,
It is preferably in the range of 0.01 to 1.0 μm.

The substrate on which the electroless copper plating film is formed as described above is subjected to a secondary electrolytic copper plating process so that a conductor layer having a desired thickness is finally formed, so that the substrate can be formed at the time of forming the base metal. It is possible to obtain a two-layer flexible substrate that is not affected by various generated pinholes and is sound and has a high degree of adhesion of the conductor layer. The copper electroplating treatment performed in the present invention may employ various conditions in the conventional copper electroplating for both primary and secondary.

In the present invention, the underlying metal layer directly formed on the insulator film is obtained by dry plating at least one selected from the group consisting of nickel, copper-nickel alloy, chromium and chromium oxide. First coating layer
The second layer is formed by forming a copper dry plating layer as a second layer on the second layer. The reason why the underlayer metal layer is formed in two layers is that the above-mentioned adverse effects due to the pinholes are suppressed as much as possible by shifting the locations where pinholes are generated by the dry plating process. Nickel having relatively good adhesion to a synthetic resin as a constituent material of an insulator film,
By providing a dry plating film layer of chromium and these compounds and the like, and disposing a highly conductive copper coating layer on the surface layer of the second layer, both the adhesion and the electrical conductivity of the underlying metal layer are improved, This is to make the performed primary copper electrolytic treatment easier.

The thickness of each dry plating film formed as a base metal layer is 50 to 2,000 angstroms for the first dry plating film layer of nickel, copper-nickel alloy, chromium, chromium oxide or the like. Preferably, the second copper dry plating layer is 200-200.
Preferably, it is 5,000 angstroms. When the thickness of the first dry plating film layer is less than 50 angstroms, there is a problem in long-term adhesion of the underlying metal layer even after each of the subsequent processing steps, and when it exceeds 2,000 angstroms. This is because it becomes difficult to remove nickel, chromium, and the like when processing the wiring portion. When the thickness of the second copper dry plating film layer is less than 200 angstroms, it is difficult to perform a satisfactory primary copper electroplating process because the effect of reducing defects due to pinholes is small and it is difficult. If the thickness exceeds angstrom, cracks and warpage due to stress are generated in the coating layer, and the adhesion strength is rather lowered.

As a dry plating method for forming these two underlying metal layers in the present invention, any one of a vacuum deposition method, a sputtering method, and an ion plating method may be appropriately employed.

[0032]

EXAMPLES Examples of the present invention are listed below together with comparative examples. Example 1: 50 μm thick polyimide film (Toray
DuPont product name "Kapton 200V") 12c
m × 12 cm, and a nickel coating layer was formed on one surface thereof by a vacuum evaporation method as a first layer of a base metal layer.
A copper coating layer was formed to a thickness of 1000 Å by vacuum evaporation as a second layer thereon.

Next, this was immersed in a weak alkaline degreasing agent for 1 minute, and then washed with water for 2 minutes to perform a surface cleaning treatment. Next, a primary electrolytic copper plating layer having a thickness of 1 μm was formed using an electrolytic copper plating solution having the composition shown in Table 1. The plating conditions at this time were a plating solution temperature of room temperature, air stirring, and a current density of 0.5 A / dm ² .

[0034]

[Table 1] Copper sulfate pentahydrate: 80 g / l Sulfuric acid: 200 g / l Brightener: as appropriate Chloride ion: 50 mg / l

After the formation of the primary electrolytic copper plating film, the film was washed with water and immersed in a catalizing solution and an accelerating solution (both manufactured by Okuno Pharmaceutical Co., Ltd.) to apply a catalyst to the substrate surface. Subsequently, the substrate was immersed in an electroless copper plating solution having the composition shown in Table 2 for 3 minutes to form an electroless copper plating film having a thickness of 0.1 μm on the surface. The plating conditions at this time were as follows: the temperature of the plating solution was 60 ° C., the pH was 12.5, and air stirring was performed.

[0036]

[Table 2] Copper sulfate: 10 g / liter EDTA: 30 g / liter HCHO (36% solution): 5 ml / liter PEG1000: 0.5 g / liter Dipyridyl: 10 mg / liter

After the electroless plating treatment, a secondary electrolytic copper plating film was formed using an electrolytic copper plating solution having the composition shown in Table 1 so that the thickness of the copper conductor layer finally became 5 μm. The plating conditions at this time were as follows: the temperature of the plating solution was room temperature, the air was stirred, and the current density during energization was 3 A / dm ^2.
And

The obtained substrate was irradiated with light from the copper film side to check for the presence of pinholes.
No light transmission was observed in the region of cm, indicating that no pinhole was present. Wiring width 4 using this substrate
When a flexible wiring board having a wiring pitch of 0 μm and a wiring pitch of 80 μm was manufactured based on a subtractive method according to a conventional method, a two-layer flexible wiring board free from defects due to pinholes in wiring portions was obtained.

When the wiring portion of the two-layer flexible wiring board was peeled off vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / cm or more, and the base metal layer was vacuum-deposited on the polyimide film. After that, the electroless plating process is immediately performed without applying the primary electrolytic copper plating film layer, and then the adhesive strength is higher than that of the substrate having the electrolytic copper plating film layer formed thereon, and the adhesion can be sufficiently provided for practical use. It was found to have strength.

In this embodiment, an example of manufacturing a single-sided flexible wiring board obtained from a substrate having a wiring pattern on one side of a polyimide film by a subtractive method has been described. It has been confirmed that the same excellent results can be obtained for a double-sided flexible wiring board having the above-mentioned or a single-sided or double-sided flexible wiring board manufactured by a semi-additive method.

Example 2 The procedure of Example 1 was repeated except that the first nickel coating layer in the base metal layer was formed to a thickness of 500 Å by vacuum evaporation.
A two-layer flexible printed circuit board was prepared and a two-layer flexible printed circuit board was prepared using this substrate in the same procedure as in Example 1.
A layer flexible wiring board was obtained. When the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf /
cm or more, and was found to have a sufficient adhesive strength to be practically used.

Example 3 A first nickel coating layer of a base metal layer was formed to a thickness of 1,000 angstroms by a vacuum evaporation method, and a second copper coating layer was formed to a thickness of 500 angstroms by a vacuum evaporation method. A two-layer flexible printed circuit board was manufactured in the same procedure as in Example 1 except that the wiring board was formed, and a two-layer flexible printed circuit board was manufactured in the same procedure as in Example 1 using this substrate. A two-layer flexible wiring board free from defects due to pinholes was obtained. Further, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / cm or more, and the adhesion strength sufficient for practical use was obtained. It was found to have.

Example 4 A two-layer flexible substrate was manufactured in the same procedure as in Example 1 except that chromium was formed to a thickness of 100 angstroms by vacuum evaporation instead of nickel of the first layer in the base metal layer. Using this substrate, a two-layer flexible wiring board was manufactured in the same procedure as in Example 1. As a result, a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. When the wiring portion of the obtained two-layer flexible wiring board was peeled vertically and the adhesion strength of the wiring portion was measured, the strength was 1 k.
gf / cm or more, and was found to have a sufficient adhesive strength to be practically used.

Example 5: A two-layer flexible film was formed in the same manner as in Example 1 except that chromium oxide was formed to a thickness of 100 angstroms by vacuum evaporation instead of nickel in forming the first layer in the base metal layer. A substrate was prepared, and a two-layer flexible wiring board was prepared using this substrate in the same procedure as in Example 1. As a result, a two-layer flexible wiring board free from defects due to pinholes in the wiring portion was obtained.
Further, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / cm or more, and the adhesion strength sufficient for practical use was obtained. It was found to have.

Example 6: The first chromium oxide coating layer of the base metal layer was formed to a thickness of 50 angstroms by a vacuum evaporation method, and the second copper coating layer was formed to a thickness of 1,500 angstroms by a vacuum evaporation method. A two-layer flexible printed circuit board was manufactured in the same procedure as in Example 1 except that the wiring layer was formed to a thickness of 2 mm, and a two-layer flexible wiring board was manufactured in the same procedure as in Example 1 using this substrate. Thus, a two-layer flexible wiring board free from defects due to pinholes was obtained. Further, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / cm or more, and the adhesion strength sufficient for practical use was obtained. It was found to have.

Example 7: The formation of the first layer in the base metal layer was replaced with nickel having a nickel content of 40% by weight.
A two-layer flexible substrate was prepared in the same procedure as in Example 1 except that a nickel alloy was formed to a thickness of 100 Å by a vacuum deposition method, and this substrate was used to produce a two-layer flexible substrate in the same procedure as in Example 1. When a wiring board was prepared, a two-layer flexible wiring board having no defects due to pinholes in the wiring portion was obtained. Further, when the wiring portion of the obtained two-layer flexible wiring board was peeled vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / c.
m or more, and was found to have a sufficient adhesive strength to be practically used.

Example 8: 5 μm primary copper plating layer
A two-layer flexible printed circuit board was manufactured in the same procedure as in Example 1 except that the wiring board was formed to a thickness of m, and a two-layer flexible wiring board was manufactured in the same procedure as in Example 1 using this substrate. A two-layer flexible wiring board free from defects caused by pinholes was obtained. Further, when the wiring portion of the obtained two-layer flexible wiring board was peeled vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / c.
m or more, and was found to have a sufficient adhesive strength to be practically used.

Example 9: The primary copper electroplating layer was 5 μm thick.
A two-layer flexible printed circuit board was produced in the same procedure as in Example 5 except that the substrate was formed to a thickness of m, and a two-layer flexible wiring board was produced in the same procedure as in Example 1 using this substrate. A two-layer flexible wiring board free from defects caused by pinholes was obtained. Further, when the wiring portion of the obtained two-layer flexible wiring board was peeled vertically and the adhesion strength of the wiring portion was measured, the strength was 1 kgf / c.
m or more, and was found to have a sufficient adhesive strength to be practically used.

Comparative Example 1: The same procedure as in Example 1 except that the thickness of the first nickel coating layer of the base metal layer was set to 50 Å and the thickness of the second copper coating layer was set to 50 Å. When the primary electrolytic copper plating treatment was performed, the electrolytic voltage became 10 V or more, the current stopped flowing, and the electrolytic copper plating treatment could not be continued.

Comparative Example 2: A two-layer flexible substrate was produced in the same procedure as in Example 1 except that the primary copper plating treatment was not performed on the underlying metal layer, and this substrate was used to perform the same procedure as in Example 1. When a two-layer flexible wiring board was produced by the procedure described in the above, a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. However, when the wiring portion of the obtained two-layer flexible wiring board was peeled vertically and its adhesion strength was measured, the strength was found to be 1 kgf / c.
m or less, and did not have an adhesive strength that could be put to practical use.

Comparative Example 3: A two-layer flexible substrate was produced in the same procedure as in Example 1 except that the thickness of the primary copper plating film layer applied on the base metal layer was changed to 0.1 μm, and this substrate was used. Then, a two-layer flexible wiring board was produced in the same procedure as in Example 1. As a result, a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. However, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and its adhesion strength was measured, the strength was 1 kgf / cm or less, which was not enough to be practically used. Was.

Comparative Example 4: Two-layer flexible substrate in the same procedure as in Example 1 except that the primary electrolytic copper plating and the electroless copper plating were omitted, and the electrolytic copper plating was performed directly on the underlying metal layer. Was prepared. The obtained substrate was irradiated with light from the copper coating side to check for the presence or absence of pinholes. As a result, light was partially transmitted within a region of 12 cm × 12 cm, indicating that pinholes were present. Further, when a two-layer flexible wiring board was produced using this substrate in the same procedure as in Example 1, it was confirmed that there was a defective portion in the wiring portion due to a missing portion considered to be due to a pinhole. Was not suitable for producing a two-layer flexible wiring board having a wiring portion having a narrow pitch width.

Comparative Example 5: The primary electrolytic copper plating film layer was 12
A two-layer flexible substrate was produced in the same procedure as in Example 1, except that the thickness of the conductive layer was formed to a thickness of 15 μm, and the thickness of the final conductor layer obtained by performing the secondary electrolytic copper plating treatment was changed to 15 μm. Using this substrate, a two-layer flexible wiring board was produced in the same procedure as in Example 1, and a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. However, the obtained two-layer flexible wiring board is
It is not suitable for a flexible wiring board because the thickness of the copper conductor layer at the portion considered to be the exposed portion of the polyimide film based on the coarse pinhole at the time of forming the base metal layer is small and the step with other portions is as large as 12 μm. I understood that.

Comparative Example 6: A two-layer flexible substrate was produced in the same procedure as in Example 4 except that the thickness of the primary copper plating film layer applied on the base metal layer was changed to 0.1 μm, and this substrate was used. Then, a two-layer flexible wiring board was produced in the same procedure as in Example 1. As a result, a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. However, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and its adhesion strength was measured, the strength was 1 kgf / cm or less, which was not enough to be practically used. Was.

Comparative Example 7: A two-layer flexible substrate was produced in the same procedure as in Example 5, except that the thickness of the primary copper plating layer applied on the underlying metal layer was changed to 0.1 μm, and this substrate was used. Then, a two-layer flexible wiring board was produced in the same procedure as in Example 1. As a result, a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. However, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and its adhesion strength was measured, the strength was 1 kgf / cm or less, which was not enough to be practically used. Was.

Comparative Example 8: A two-layer flexible substrate was produced in the same procedure as in Example 7, except that the thickness of the primary copper plating layer applied on the base metal layer was changed to 0.1 μm, and this substrate was used. Then, a two-layer flexible wiring board was produced in the same procedure as in Example 1. As a result, a two-layer flexible wiring board free from defects caused by pinholes in the wiring portion was obtained. However, when the wiring portion of the obtained two-layer flexible wiring board was peeled off vertically and its adhesion strength was measured, the strength was 1 kgf / cm or less, which was not enough to be practically used. Was.

[0057]

As described above, according to the method of manufacturing a two-layer flexible substrate of the present invention, the pinholes of the underlying metal layer generated by the dry plating method applied to the insulating film are formed into two layers of the underlying metal layer. After being reduced by forming, the lowering of the adhesion of the underlying metal layer based on the fine pinholes among the pinholes is suppressed by performing the primary electrolytic copper plating treatment, and the exposure of the insulator film due to the coarse pinholes is performed. By covering the portion with an electroless copper plating film layer, the occurrence of the conductor portion loss due to the coarse pinhole is suppressed, so that a two-layer flexible substrate having an extremely thin copper conductor layer of 3 to 18 μm is obtained. Sound and easy to get. Therefore, by using this substrate, a highly reliable two-layer flexible wiring board having high adhesion and a defect-free wiring portion can be efficiently obtained, and the effect is large.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H05K 3/38 H05K 3/38 C // C23C 14/06 C23C 14/06 N

Claims (7)

[Claims] 1. A two-layer flexible substrate comprising: a base metal layer formed directly on one or both sides of an insulator film without an adhesive; and a copper conductor layer having a desired thickness formed on the base metal layer. In the manufacturing method, a coating layer formed by dry plating using at least one selected from the group consisting of nickel, copper-nickel alloy, chromium, and chromium oxide on an insulating film, and the coating layer Formed by a copper coating layer by a dry plating method further formed on the
Next, after forming a primary electrolytic copper plating film layer on the base metal layer, an electroless copper plating film layer is formed as an intermediate metal layer on the primary electrolytic copper plating film layer, and finally on the intermediate metal layer. A method for manufacturing a two-layer flexible substrate, comprising: finally forming a copper conductor layer having a thickness of 5 to 18 μm on an insulator film by forming a secondary electrolytic copper plating film layer. 2. A dry plating layer using at least one selected from the group consisting of nickel, copper-nickel alloy, chromium, and chromium oxide formed as the first layer of the base metal layer has a thickness of 50 to 50. 2. The method for manufacturing a two-layer flexible substrate according to claim 1, wherein the thickness is 2,000 angstroms. 3. The two-layer flexible substrate according to claim 1, wherein the thickness of the copper coating layer formed by the dry plating method, which is formed as the second layer of the base metal layer, is 200 to 5,000 angstroms. Method. 4. The two-layer flexible substrate according to claim 1, wherein the dry plating method for forming the base metal layer is any one of a vacuum deposition method, a sputtering method, and an ion plating method. Production method. 5. The thickness of the primary electrolytic copper plating film layer is 0.3
2. The method for manufacturing a two-layer flexible substrate according to claim 1, wherein the thickness is in a range of 10 to 10 [mu] m. 6. The thickness of the electroless copper plating film layer is 0.0
2. The method according to claim 1, wherein the distance is in the range of 1 to 1.0 [mu] m.
A method for producing a two-layer flexible substrate according to the above. 7. The method for producing a two-layer flexible substrate according to claim 1, wherein a catalyst applying treatment is performed as a pretreatment when forming the electroless copper plating film layer.