JP4463442B2 - Printed wiring board materials - Google Patents

Description

[0001]
[Industrial application fields]
The present invention is a printed wiring board material, particularly a printed circuit board having a pitch between wirings of 100 μm or less used for mounting of electronic components and semiconductors (LSIs, ICs) and packaging materials, or liquid crystal displays (LCDs), semiconductors and semiconductor packages. The present invention relates to a material that can be used for a wiring board.
[0002]
[Prior art]
The expansion of the use of printed wiring boards is not limited, and it is not only the conventional wiring for connecting electronic components and their functions as a support, but also CSP (Chip Size Package) and BGA for mounting ICs on the motherboard. (Ball Grid Array) and other semiconductor packages have been used for semiconductor substrates used as part of IC wiring, and the miniaturization of wiring rules has been progressing. In particular, flexible wiring board materials are used for LCD and semiconductor inspection probes as a new application, and wiring pitches of 50 μm or less are practically used. Furthermore, wiring processing of wiring pitches of 30 μm or less is also practical. Consideration is being made.
[0003]
Conventionally, as a flexible printed wiring board application, a copper foil is pasted on an epoxy-based adhesive on a so-called cast material or polyimide base material prepared by imidizing after coating a polyimide precursor on a copper foil. The attached material has been widely used.
However, in the case of a cast material or the like, the minimum thickness of the copper foil is as thick as 12 μm, so that there has been a problem that it becomes difficult to process a fine pattern with a wiring pitch of 50 μm or less. A cast material of 9 μm copper foil has also been developed, but has not yet been put into practical use, including the handling surface of the base material.
[0004]
Against this background, a copper thin film of 1 μm or less is formed on a polyimide substrate by sputtering or the like, which has conventionally been avoided from price constraints and heat resistance, or electrolytic copper plating is applied to the copper thin film So-called sputtered materials processed to have a copper thickness of 10 μm or less are attracting attention.
In particular, a material in which a copper thin film having a thickness of 1 μm or less is formed on a polyimide base material by a sputtering method or the like is attracting attention as a material capable of fine wiring processing by a semi-additive method. That is, for example, after laminating a dry film resist or liquid pattern resist on a copper thin film, exposure and development are performed to form a pattern resist, and further, a metal such as nickel or copper is electroplated using the copper thin film as a power feeding layer. Then, after peeling off the resist, soft etching is performed to remove the copper thin film, thereby attracting attention as a material used in a method for producing an electric circuit pattern or a part.
[0005]
[Problems to be solved by the invention]
However, it is difficult to carry out the rust prevention treatment with a material in which a copper thin film having a thickness of 1 μm or less is formed on a substrate, and rust generated on the copper thin film, that is, the yield is often lowered due to oxidation of copper. It has occurred as a new problem.
[0006]
For example, when copper is oxidized, the adhesion of the pattern resist (photoresist) onto the copper thin film is reduced, and copper plating is also applied to the lower part of the pattern resist in the pattern plating process (circuit formation process by plating). It becomes easy to generate a short circuit. Even if the pattern resist is in close contact with oxidized copper, the glass mask or exposure film (pattern mask for circuit pattern printing) slightly floats due to the unevenness caused by the oxide, resulting in light shielding by the mask. Light also circulates in the area, making it easy to cause a short circuit. Alternatively, the copper oxide is dissolved by the chemical treatment in the development process and pattern plating process after the exposure process, and the pattern resist is peeled off from the copper thin film. As a result, a short circuit is likely to occur in the pattern plating process. There is.
[0007]
Such a problem caused by oxidation of copper can be solved by applying a rust preventive treatment especially for a copper thicker one.
That is, a cast product using a copper foil having a thickness of 9 μm or more, a sputter product in which a copper thin film having a thickness of 1 μm or less is formed by a sputtering method or the like, and electrolytic copper plating is applied to increase the copper thickness to, for example, 3 μm or more. In the case of printed wiring board materials with relatively thick copper, such as rust prevention treatment such as coating the surface of copper with organic chemicals such as benzotriazole and metals that can easily form passivation films The copper surface that has been surface-treated with a so-called soft etching solution such as ammonium persulfate immediately before laminating the pattern resist on the copper foil is etched to a thickness of, for example, 3 μm or less, and copper oxide or a rust preventive agent The surface of copper can be roughened and the adhesion of the pattern resist can be improved.
[0008]
However, when these rust prevention treatments are applied to a material that only forms a copper thin film of 1 μm or less, it becomes very difficult to control the etching thickness of the copper foil, and the variation in the thickness of the remaining copper foil is large. As a result, variations in surface resistance occur, and variations in plating thickness during pattern plating may result in a decrease in yield, or in the worst case, a copper thin film may be completely removed.
[0009]
In this way, with a printed wiring board material in which a copper thin film of 1 μm or less is only formed on the substrate surface, it is difficult to prevent copper oxidation by subjecting the copper foil surface to rust prevention treatment. This is a major obstacle to improving the yield when manufacturing fine wiring patterns and fine parts.
Even if the thickness of the metal thin film formed on the polymer substrate is 1 μm or less, the present invention prevents the oxidation of the metal thin film without causing a decrease in yield, and enables the printed wiring board to be manufactured with excellent productivity. It is an object to provide a printed wiring board material that can be manufactured.
[0010]
[Means for Solving the Problems]
The printed wiring board material of the present invention has a first metal layer on at least one surface of a polymer substrate, and a base metal or a metal of these metals on the surface of the first metal layer. It has the antioxidant layer which consists of these oxides.
The thickness of the antioxidant layer is preferably 0.1 to 5 nm, the first metal layer is preferably copper or copper-based metal, and the antioxidant layer is made of tin, indium, And one or more metals selected from the group consisting of zinc and oxides of those metals, the thickness of the first metal layer is preferably 50 nm to 1 μm, A polyimide is preferred.
[0011]
In this way, not only the first metal layer is effectively prevented from being oxidized, but also the antioxidant layer is easily etched in the etching process when the printed wiring board is made from the printed wiring board material. Therefore, the productivity of the printed wiring board is not lowered.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The printed wiring board material according to the present invention has a first metal layer on at least one surface of a polymer base material, and a metal that is baser than the first metal layer on the surface of the first metal layer or a material thereof. It has an antioxidant layer made of an oxide.
[0013]
FIG. 1 shows an example in which a first metal layer 102 is formed on one surface of a polymer substrate, that is, the surface of the polymer substrate 100, and an antioxidant layer 104 is further formed on the first metal layer 102. It is sectional drawing shown. FIG. 2 shows that the first metal layer 102 is formed on both surfaces of the polymer substrate, that is, the upper and lower surfaces of the polymer substrate 100, and the antioxidant layer 104 is formed on the surface of each first metal layer 102. It is sectional drawing which shows the example.
[0014]
Polymer substrate The material of the polymer substrate is not particularly limited, and any material that can be used as a printed wiring board or a flexible printed wiring board can be preferably used.
For example, polyimide, filled polyimide, epoxy resin, polyethylene terephthalate, polyetherimide, polyethylene naphthalate, polyethylene sulfur, polyamide, aromatic polyamide, or the like can be used.
[0015]
Of these, polyimide or filled polyimide is particularly preferred from the viewpoint that heat resistance is often one of the required items in the working environment during or after processing of the printed wiring material. Specific product names include, for example, “Kapton Super V”, “Kapton V”, “Kapton E”, “Kapton EN”, “Kapton H” (manufactured by Toray DuPont Co., Ltd.), “Upilex S”, “ Iupilex SGA (above Ube Industries, Ltd.), Apical AH, Apical NPI, Apical HP (above Kaneka Chemical Co., Ltd.), etc. Yes, it can be suitably used in the present invention.
[0016]
Furthermore, a polyimide formed by directly imidizing an acid anhydride and an amine can also be used effectively.
Examples of such acid anhydrides include pyromellitic acid anhydride, biphthalic acid anhydride, benzophenone tetracarboxylic acid anhydride, oxydiphthalic acid anhydride, hydrofurandiphthalic acid anhydride, and the like.
[0017]
On the other hand, examples of the amine include methoxydiaminobenzene, 4,4′-oxydianiline, 3,4′oxydianiline, 3,3′oxydianiline, bisdianilinomethane, and 3,3′-diaminozenzo. Phenone, p, p-aminophenoxybenzene, p, m-aminophenoxybenzene, m, p-aminophenoxybenzene, m, m-aminophenoxybenzene, chloro-m-aminophenoxybenzene, p-pyridineaminophenoxybenzene, m -Pyridineaminophenoxybenzene, p-aminophenoxybiphenyl, m-aminophenoxybiphenyl, p-bisaminophenoxybenzidisulfone, m-bisaminophenoxybenzodisulfone, p-bisaminophenoxybenzylketone, m-bisaminophenoxybenzylketone, p- Bisaminophenoxybenzylhexafluoropropane, m-bisaminophenoxybenzylhexafluoropropane, m-bisaminophenoxybenzylhexafluoropropane, p-bisaminophenoxybenzylpropane, o-bisaminophenoxybenzylpropane, m-bisaminophenoxybenzyl Examples include propane, p-diaminophenoxybenzylthioether, m-diaminophenoxybenzylthioether, indanediamine, spirobidiamine, and diketonediamine.
[0018]
The thickness of such a polymer base material is not particularly limited, and can be appropriately selected depending on the purpose of use of the printed wiring board. For example, in the polyimide film base material often used for flexible printed wiring plate applications, those having a thickness of 12.5 to 150 μm are preferable, those having a thickness of 12.5 to 100 μm are more preferable, and those having a thickness of 12.5 to 75 μm are particularly preferable. Thick ones are preferred and are readily available on the market.
[0019]
First metal layer The first metal layer is a single metal or alloy film having a thickness of 50 nm to 1 μm.
The type of metal used for the first metal layer is not particularly limited, but the metal film is used as a power supply layer (conductor layer) for wiring of a printed wiring board or electrolytic plating in an additive method. Excellent conductivity, easily soluble in acidic etchants such as cupric chloride and ferric chloride, alkaline etchants such as ammonia, and other etchants and soft etchants such as ammonium persulfate Something is required.
[0020]
As such a metal, for example, a single metal such as copper, aluminum, molybdenum, cobalt, nickel, and an alloy containing at least one of these metals are preferable. Among these, copper and metals mainly composed of copper are particularly preferable metals because they are excellent in electrical conductivity and rich in spreadability. Here, in this invention, the metal which has copper as a main component is a metal which contains copper 50weight% or more, ie, a copper alloy or copper.
[0021]
The method for forming the first metal layer is not particularly limited, and is a wet process such as electroless plating, electrolytic plating, dry process such as vapor deposition, ion plating, sputtering, and chemical vapor transport. (CVD method) or a combination of these can be appropriately selected and used.
Among these, the sputtering method is preferable in consideration of the adhesion between the first metal layer and the polymer substrate and the ease of film formation. The sputtering method includes various methods such as DC sputtering, RF sputtering, DC magnetron sputtering, RF magnetron sputtering, ECR sputtering, and laser beam sputtering. However, the sputtering method is not particularly limited and may be appropriately used as necessary. it can. In particular, the DC magnetron sputtering method is preferable because it is low in cost and can easily form the first metal layer.
[0022]
In this case, the film forming conditions of the first metal layer by magnetron sputtering are as follows: the sputtering gas is argon gas, and the pressure is 10 ^{−2 to 1} Pa, preferably 7 × 10 ^{−2 to} 7 × 10 ⁻¹ Pa, more preferably 10 ⁻¹ to 4 × 10 ⁻¹ Pa, and the sputtering power density is ¹ to 100 Wcm ⁻² , preferably 1 to 50 Wcm ⁻² , and more preferably 1 to 20 Wcm ⁻² .
[0023]
As a target used for sputtering, copper having a purity of 99.9% or more, preferably 99.99% or more, or a metal mainly composed of copper can be used. Use of a target having a purity of 99.999% or more is not preferable because it causes a significant increase in cost. The film thickness when the first metal layer is formed by magnetron sputtering can be controlled by managing the film formation time by obtaining the film formation speed in advance.
[0024]
The thickness of the first metal layer formed by such a method is 50 nm or more, preferably 100 nm or more, more preferably 200 nm or more. The first metal layer is used as a power supply layer for electrolytic plating when forming a fine pattern by the additive method, and as a base layer for electroless plating. There is no need to secure or pinholes.
[0025]
In addition, the purity of the metal used for the first metal layer is the ratio of the single metal to the entire first metal layer when the first metal layer is formed of a single metal. In the case of forming, the ratio of the alloy to the entire first metal layer is 99.9% or more, preferably 99.99% or more. Within this range, sufficient electrical conductivity can be ensured.
[0026]
On the other hand, in order to form a fine pattern on a printed wiring board, the first metal layer needs to be thin to some extent, and the cost for forming the first metal layer by a sputtering method that is preferably used. Considering the above constraints, the thickness of the first metal layer is desirably 1 μm or less, preferably 500 nm or less.
Furthermore, in order to improve the adhesive strength and heat resistance between the polymer substrate and the first metal layer, an adhesive layer is provided between the polymer substrate and the first metal layer, or the surface of the polymer substrate is treated with plasma or ultraviolet light. It is preferable to use a known technique such as exposure to water or immersion in an alkaline etching solution to modify the surface, or modification of the polymer substrate surface with a silane coupling material or another type of polymer.
[0027]
Specific examples of the material that can be used as the adhesive layer include one selected from metals such as titanium, vanadium, cobalt, nickel, zinc, tungsten, molybdenum, zirconium, tantalum, tin, and indium, or a group thereof. Examples include alloys containing the above metals, heat resistant alloys such as Monel, Nichrome, and Inconel. Furthermore, the metal oxides such as oxides, nitrides, carbides, phosphorus compounds, and metal oxides such as indium tin oxide (ITO) and zinc chromate can also be used as the adhesive layer.
[0028]
The thickness of such an adhesive layer is desirably 5 to 50 nm, preferably 5 to 20 nm, and if within this range, the effect of improving the adhesive strength and heat resistance between the polymer substrate and the first metal layer There is.
Antioxidant layer The metal used in the antioxidant layer or the metal used in those oxides is a base metal than the first metal layer. A base metal with respect to the metal here is a metal having a lower standard electrode potential in an aqueous solution system.
[0029]
For example, in the present invention, considering that the metal used for the first metal layer is preferably copper or a metal mainly composed of copper, indium, tin, zinc and their oxides are easily dissolved in the etching process. It is a preferable material because it is a metal that can be produced and has a high antioxidant effect on the first metal layer. When these metals are used, it is considered that the oxidation of the first metal layer can be prevented by a kind of electrochemical action.
[0030]
The method for forming such an antioxidant layer is not particularly limited, and can be appropriately selected based on the characteristics of the material to be formed. Examples thereof include wet methods such as electroless plating, and dry methods such as vapor deposition, ion plating, ion cluster beam, and sputtering.
Among these, when a low melting point metal such as indium, tin, or zinc is used as the antioxidant layer, a vapor deposition method using metal vapor generated by heating and melting the metal is preferable. In addition, when an oxide of a metal such as indium, tin, or zinc is used, a sputtering method capable of easily forming the oxide is preferable. Among the sputtering methods, the DC magnetron sputtering method is most efficiently and inexpensively formed. This is preferable because it is possible. Tin oxide, indium oxide, and ITO are conductive materials, and zinc oxide is a material that exhibits high conductivity by adding several percent by weight of aluminum oxide or silicon oxide, and can be easily formed by DC magnetron sputtering. It is a possible substance. These oxides are also readily available on the market.
[0031]
The thickness of such an antioxidant layer is 0.1 to 5 nm, preferably 0.5 to 2 nm. Within this range, the first metal layer has an antioxidant effect.
It should be noted that with such a thin film thickness, the metal or metal oxide may not be formed into a complete layer, that is, an island shape (sea-island structure) may be considered, but the effect of the present invention is hindered at all. It is not a thing. When the metal or metal oxide does not form completely in layers, such as growing in an island shape, the film thickness is measured by the equivalent film thickness expected from the film formation speed or by a quartz oscillator film thickness meter. The film thickness calculated from the weight and density of the formed material may be within the above range.
[0032]
The formation of the first metal layer and the antioxidant layer on the polymer substrate may be performed on one side of the polymer substrate as shown in FIG. 1 or as shown in FIG. 2, depending on the use of the printed wiring board. It may be on both sides of the polymer substrate.
When forming a metal layer on both sides of the polymer substrate, the first metal layer and the antioxidant layer may be formed on each side, or after forming the first metal layer on both sides, A film may be formed on one metal layer. The deposition order of each metal layer is the same as the film deposition apparatus, such as a vapor deposition apparatus, an ion plating apparatus, a sputtering apparatus, and the structure of each apparatus, for example, both sides, at the same time. Whether it is a film-forming sputtering device, vapor deposition device or ion plating device, or a device capable of continuously performing sputtering and vapor deposition in a roll-to-roll manner, the first metal layer is a sputtering device, and the antioxidant layer is a vapor deposition device. In order to produce the printed wiring board material according to the present invention in the most efficient manner, considering whether the printed wiring material of the present invention is to be produced using two devices, etc. be able to.
[0033]
By producing a printed wiring board using such a wiring board material, even if the thickness of the first metal layer is 1 μm or less by fine pattern processing with a pitch between wirings of 100 μm or less, preferably 50 μm or less. Thus, oxidation of the first metal layer can be prevented and productivity can be improved without causing a decrease in yield.
[0034]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[0035]
[Example 1]
Using a 50 μm-thick polyimide film, “Apical NPI” (manufactured by Kaneka Chemical Co., Ltd.) as a polymer substrate, cut it into an 8 cm square, and place it on a substrate holder of a sputtering apparatus, up to a pressure of 10 ⁻³ Pa or less. A vacuum was drawn. The polyimide film was plasma treated under the conditions of an oxygen flow rate of 100 SCCM, a pressure of 1.3 Pa, an RF power of 100 W, and a treatment time of 3 minutes.
[0036]
Next, using a copper target (purity 99.99%), a film was formed for 15 minutes under the conditions of an argon flow rate of 40 SCCM, a pressure of 0.26 Pa, and DC of 180 W to form a first metal layer of copper to a thickness of 250 nm. did.
Further, a sample is taken out from the sputtering apparatus and placed in an electron beam heating type vapor deposition apparatus. After evacuating to a pressure of 10 ⁻³ Pa or less, zinc is used as a vapor deposition source, and 1 nm of zinc is used as an antioxidant layer. The film was formed on copper with a thickness of. The film thickness of zinc was controlled by a shutter that can be opened and closed in conjunction with a crystal oscillator type film thickness meter.
[0037]
The sample thus prepared was left in a class 10000 clean room at a temperature of 25 ° C. and a humidity of 50% for 30 days, and visually inspected.
The evaluation was performed based on whether or not a discoloration site indicating copper oxidation was generated, but no particular discoloration site was generated in this sample.
[0038]
[Example 2]
A sample was prepared and evaluated in the same manner as in Example 1 except that indium was formed to a thickness of 1 nm as the antioxidant layer, but no discoloration site indicating copper oxidation occurred.
[0039]
[Example 3]
A sample was prepared and evaluated in the same manner as in Example 1 except that tin was formed to a thickness of 1 nm as an antioxidant layer, but no discoloration site indicating copper oxidation was generated.
[Example 4]
Instead of forming zinc as an antioxidant layer in Example 1 by vapor deposition, a sample was prepared by forming zinc oxide with a thickness of 1 nm by sputtering.
That is, using a zinc oxide target (added with 3% by weight of aluminum oxide), a film was formed for 10 seconds under the conditions of an argon flow rate of 40 SCCM, a pressure of 0.26 Pa, and DC of 180 W, and the zinc oxide as an antioxidant layer was formed to a thickness of 1 nm. Filmed.
[0041]
When the obtained sample was evaluated in the same manner as in Example 1, no discoloration site indicating copper oxidation occurred.
[0042]
[Example 5]
A sample was prepared in the same manner as in Example 4 except that indium oxide was used as a sputtering target and indium oxide was formed as an anti-oxidation layer with a thickness of 1 nm, and evaluation was performed in the same manner as in Example 1. There was no discoloration site indicating copper oxidation.
[0043]
[Example 6]
A sample was prepared in the same manner as in Example 4 except that tin oxide was used as a sputtering target and tin oxide was formed as an anti-oxidation layer with a thickness of 1 nm, and evaluation was performed in the same manner as in Example 1. There was no discoloration site indicating copper oxidation.
[0044]
[Example 7]
A sample was prepared in the same manner as in Example 4 except that ITO (20% by weight of tin oxide) was used as a sputtering target and ITO was formed as an anti-oxidation layer with a thickness of 1 nm. Evaluation was made in the same manner as in Example 1. However, no discoloration indicating copper oxidation was observed.
[0045]
[Comparative Example 1]
When a sample was prepared and evaluated in the same manner as in Example 1 except that the antioxidant layer was not formed on copper, a discolored portion showing copper oxidation was generated.
[0046]
【The invention's effect】
According to the present invention, at least after forming the first metal layer on one surface of the polymer substrate, the antioxidant layer made of a base metal or an oxide thereof than the first metal has a thickness of 0.1 nm to 5 nm. By forming the first metal layer, it is possible to prevent oxidation of the first metal layer, and it is possible to prevent a decrease in the adhesion of the pattern resist formed on the first metal layer. Further, even if the thickness of the first metal layer is 1 μm or less, it is possible to prevent variations in plating thickness during pattern plating, and it is possible to produce a printed wiring board with excellent productivity.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a printed wiring board material of the present invention.
FIG. 2 is a cross-sectional view showing an example of a printed wiring board material of the present invention.
[Explanation of symbols]
100 Polymer substrate 102 First metal layer 104 Antioxidation layer

Claims (4)

A polymer substrate has a first metal layer on at least one surface, and an antioxidant layer made of a base metal or an oxide of these metals on the surface of the first metal layer. Have
The antioxidant layer has a thickness of 0.1 to 5 nm;
The oxidation layer, tin, indium, and one or more metals or printed wiring board material, wherein Rukoto such oxides of those metals selected from the group consisting of zinc. The printed wiring board material according to claim 1, wherein the first metal layer is copper or a metal mainly composed of copper. The printed wiring board material according to claim 1 or 2 , wherein the first metal layer has a thickness of 50 nm to 1 µm. Printed circuit board material according to any one of claims 1 to 3, wherein the polymer substrate is a polyimide.

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