JP2002368367A - Printed wiring board material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board material which is capable of preventing a printed wiring board from decreasing in manufacturing yield and manufacturing it with high productivity by protecting a metal thin film formed on a polymer base material and as thick as 1 μm or below against oxidation. SOLUTION: A first metal layer 102 is formed on at least one surface of a polymer base material 100, and an oxide preventive layer 104 formed of a metal more basic than the first metal layer 102 or its oxide is formed on the surface of the first metal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board material, in particular, a packaging material for electronic parts and semiconductors (LSIs and ICs) and a packaging material, or a wiring board used for a liquid crystal display (LCD) and an inspection board for semiconductors and semiconductor packages. The present invention relates to a material that can be used for a printed wiring board having a pitch of 100 μm or less.

[0002]

2. Description of the Related Art The use of printed wiring boards is not limited to expanding, and is not limited to conventional wiring for connecting electronic components and their function as supports, but also CSP (Chip) for mounting ICs on a motherboard. Size Package)
It is used for a semiconductor substrate used as a part of the wiring of an IC as a semiconductor package such as a semiconductor package such as a BGA (Ball Grid Array) and a BGA (Ball Grid Array). In particular, in the case of flexible wiring board materials, a new application is being used for a probe for inspection of LCDs and semiconductors, and a wiring pitch of 50 μm or less is practically used, and furthermore, a wiring pitch of 30 μm or less is also practically used. Studies are underway.

Conventionally, as a flexible printed wiring board, a so-called cast material or a polyimide base material produced by applying a polyimide precursor on a copper foil and then performing imidization on the copper foil via an epoxy-based adhesive. Materials with foil attached have been widely used. However, since the minimum thickness of the copper foil is as large as 12 μm in cast materials and the like, there has been a problem that it is difficult to process a fine pattern having a wiring pitch of 50 μm or less. Copper foil 9
Although μm cast materials have been developed, they have 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 base material by a sputtering method or the like, which has been conventionally avoided from the viewpoint of price restrictions and heat resistance, or electrolytic copper plating is performed on the copper thin film. The so-called sputtered material processed into a copper thickness of 10 μm or less by applying the method has attracted attention. In particular, a material in which a copper thin film having a thickness of 1 μm or less is formed on a polyimide substrate by a sputtering method or the like has attracted 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 a liquid pattern resist on a copper thin film, exposing and developing to form a pattern resist, and further using a copper thin film as a power supply layer, electroplating a metal such as nickel or copper. Then, attention is paid to a material used for a method of manufacturing an electric circuit pattern or a component by removing a resist and then performing soft etching to remove a copper thin film.

[0005]

However, there is one
It is difficult to perform a rust-prevention treatment with a material formed only of a copper thin film of μm or less, and rust generated on the copper thin film, that is, a reduction in yield often occurs due to oxidation of copper. It has arisen as a problem.

For example, when copper is oxidized, the adhesion of the pattern resist (photoresist) on the copper thin film is reduced,
In the pattern plating step (circuit forming step by plating), a short circuit easily occurs because copper plating is also applied to the lower part of the pattern resist. Also, even if the pattern resist adheres to the oxidized copper, the glass mask and the exposure film (pattern mask for printing a circuit pattern) slightly float due to the unevenness caused by the oxide, and as a result, the light is blocked by the mask. The light also circulates in the portion and short-circuits are easily generated. Also, the problem that the copper oxide is dissolved in the development step after the exposure step or the chemical treatment in the pattern plating step, and the pattern resist is peeled off from the copper thin film, and as a result, a short circuit easily occurs in the pattern plating step. There is.

[0007] It is possible to solve such a problem caused by oxidation of copper by performing a rust-preventive treatment, particularly when the copper is thick. That is, 9
Such as a cast product using a copper foil having a thickness of at least μm or a sputtered product obtained by forming a copper thin film having a thickness of at most 1 μm by a sputtering method and then performing electrolytic copper plating to increase the thickness of the copper to, for example, 3 μm or more. In the case of printed wiring board materials with relatively thick copper, rust prevention treatment such as coating the copper surface with an organic chemical represented by benzotriazole or a metal that easily forms a passivation film is performed. Immediately before laminating a pattern resist on a copper foil, the surface of the copper surface-treated with a so-called soft etching solution such as ammonium persulfate is etched to a thickness of, for example, 3 μm or less to remove copper oxide and a rust preventive agent. At the same time, the copper surface can be roughened to improve the adhesion of the pattern resist.

However, when these rust-preventive treatments are applied to a material having only a copper thin film of 1 μm or less, it is very difficult to control the etching thickness of the copper foil, and the thickness of the remaining copper foil is reduced. When the variation increases, the surface resistance varies, and the plating thickness varies at the time of pattern plating, so that the yield may decrease or, in the worst case, the copper thin film may be completely removed.

As described above, in a printed wiring board material in which a copper thin film having a thickness of 1 μm or less is formed only on the surface of a base material, it is difficult to perform a rust preventive treatment on the surface of the copper foil to prevent oxidation of the copper, and the semi-additive. This is a major obstacle to improving the yield when fabricating fine wiring patterns and fine components by the construction method. The present invention prevents the oxidation of a metal thin film formed on a polymer substrate even if the thickness of the metal thin film is 1 μm or less without lowering the yield, and enables printed wiring boards to be manufactured with excellent productivity. An object of the present invention is to provide a printed wiring board material that can be manufactured.

[0010]

The printed wiring board material of the present invention has a first metal layer on at least one surface of a polymer substrate, and the first metal layer is provided on the surface of the first metal layer. It is characterized by having an antioxidant layer made of a metal which is more noble or an oxide of such a metal. The thickness of the antioxidant layer is preferably 0.1 to 5 nm, the first metal layer is preferably copper or a metal mainly composed of copper, and the antioxidant layer is tin, indium, And at least one metal selected from the group consisting of zinc and oxides of these metals, and the thickness of the first metal layer is preferably 50 nm to 1 μm, and the polymer substrate is It is preferably polyimide.

In this manner, not only can the first metal layer be effectively prevented from being oxidized, but also the oxidation preventing layer can be easily formed in the etching step when the printed wiring board is formed from the printed wiring board material. Since etching can be performed, the productivity of the printed wiring board is not reduced.

[0012]

Embodiments of the present invention will be described below 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 substrate, and on the surface of the first metal layer, a metal lower than the first metal layer or a metal thereof. It has an antioxidant layer made of an oxide.

FIG. 1 shows that a first metal layer 102 is formed on one surface of a polymer substrate, that is, a surface of a polymer substrate 100, and an antioxidant layer 1 is formed on the first metal layer 102.
It is sectional drawing which shows the example in which 04 was formed. FIG. 2 shows that a first metal layer 102 is formed on both surfaces of the polymer substrate, that is, upper and lower surfaces of the polymer substrate 100, respectively, and an 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 polymeric substrate is not particularly limited, if as it can be used as a printed wiring board or a flexible printed wiring board can be suitably used. For example, polyimide, or filled polyimide, epoxy resin, polyethylene terephthalate, polyetherimide, polyethylene naphthalate,
Polyethylene sulfur, polyamide, aromatic polyamide and the like can be used.

Among these, polyimide or a polyimide containing filler is particularly preferable in view of the fact that heat resistance is often one of the required items in the use environment during or after processing of the printed wiring material. It is. Specific product names include, for example, “Kapton Super V”, “Kapton V”, “Kapton E”, “Kapton EN”, “Kapton H” (all manufactured by Toray DuPont), “Upilex S”, “ Upilex SG
A ”(above, manufactured by Ube Industries, Ltd.),“ Apical A
H "," Apical NPI "," Apical HP "(above,
(Kanebuchi Chemical Industry Co., Ltd.), etc., which are easily available in the market and can be suitably used in the present invention.

Further, a polyimide formed by directly imidizing an acid anhydride and an amine can also be used effectively. Examples of such an acid anhydride include pyromellitic anhydride, biphthalic anhydride, benzophenonetetracarboxylic anhydride, oxydiphthalic anhydride, hydrofurandiphthalic anhydride and the like.

On the other hand, examples of the amine include methoxydiaminobenzene, 4,4′-oxydianiline,
4'oxydianiline, 3,3'oxydianiline, bisdianilinomethane, 3,3'diaminozenzophenone, p, p-aminophenoxybenzene, p, m-aminophenoxybenzene, m, p-amino Phenoxybenzene, m, m-aminophenoxybenzene, chloro-m
-Aminophenoxybenzene, p-pyridineaminophenoxybenzene, m-pyridineaminophenoxybenzene, p-aminophenoxybiphenyl, m-aminophenoxybiphenyl, p-bisaminophenoxybendisulfone, m-bisaminophenoxybendisulfone,
p-bisaminophenoxybenzylketone, m-bisaminophenoxybenzylketone, p-bisaminophenoxybenzylhexafluoropropane, m-bisaminophenoxybenzylhexafluoropropane, m-bisaminophenoxybenzylhexafluoropropane, p
-Bisaminophenoxybenzylpropane, o-bisaminophenoxybenzylpropane, m-bisaminophenoxybenzylpropane, p-diaminophenoxybenzylthioether, m-diaminophenoxybenzylthioether, indanediamine, spirobidiamine, diketonediamine and the like. .

The thickness of such a polymer substrate is not particularly limited, and can be appropriately selected according to the intended use of the printed wiring board. For example, a polyimide film substrate often used for flexible printed wiring board applications preferably has a thickness of 12.5 to 150 μm, more preferably 12.5 to 100 μm, and particularly preferably 12.5 to 75 μm. Thick ones are preferred and are readily available on the market.

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. However, since the metal film is used as a power supply layer (conductor layer) at the time of electrolytic plating in a printed wiring board or an additive construction 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.

As such a metal, for example, a simple metal such as copper, aluminum, molybdenum, cobalt, nickel and the like, and an alloy containing at least one or more thereof are preferable. Among them, copper and a metal mainly composed of copper are particularly preferable metals because they have excellent conductivity and are rich in extensibility. Here, in the present invention, the metal mainly composed of copper is a metal containing 50% by weight or more of copper, that is, a copper alloy or copper.

The method for forming the first metal layer is not particularly limited, and is a wet process such as an electroless plating method, an electrolytic plating method, a dry process such as a vapor deposition method, an ion plating method, a sputtering method, and a chemical vapor deposition method. Phase transport method (CVD method)
And the like, and combinations thereof 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. In addition, DC sputtering, RF sputtering, DC magnetron sputtering,
Although there are various methods such as F magnetron sputtering, ECR sputtering, and laser beam sputtering, the method is not particularly limited and can be appropriately used as needed. In particular, the DC magnetron sputtering method is preferable because it is inexpensive and can easily form the first metal layer.

In this case, the conditions for forming 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.
７7 × 10 ⁻¹ Pa, more preferably 10 ⁻¹ to 4 × 10
^-1 Pa, and a sputtering power density of 1 to 100 Wcm.
^-2 , preferably 1 to 50 Wcm ^-2 , more preferably 1 to
２０20 Wcm ⁻² .

As a target used for sputtering, copper or a metal mainly composed of copper having a purity of 99.9% or more, preferably 99.99% or more can be used. It is not preferable to use a target having a purity of 99.999% or more, because a cost is significantly increased. The control of the film thickness when forming the first metal layer by magnetron sputtering can be performed by controlling the film forming time by obtaining the film forming speed in advance.

The thickness of the first metal layer formed by such a method is at least 50 nm, preferably at least 100 nm, more preferably at least 200 nm. The first metal layer is used as a power supply layer for performing electrolytic plating or a base layer during electroless plating when forming a fine pattern by the additive method, so that the electric conductivity is within such a range. There is no need to secure them or generate pinholes.

In the case where the first metal layer is formed of a single metal, the purity of the metal used for the first metal layer is defined as the ratio of the single metal to the entire first metal layer, and the purity of the alloy is the first metal. When the metal layer is formed, the ratio of the alloy to the entire first metal layer is 99.9% or more, preferably 99.99% or more. Can be.

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 first metal layer is formed by a preferably used sputtering method. In consideration of cost constraints in such a case, it is desirable that the thickness of the first metal layer is 1 μm or less, preferably 500 nm or less. Furthermore, for the purpose of improving the adhesive strength and heat resistance between the polymer base material and the first metal layer, an adhesive layer may be provided between the polymer base material and the first metal layer, or the surface of the polymer base material may be exposed to 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.

Specific examples of the substance that can be used as the adhesive layer include metals selected from the group consisting of metals such as titanium, vanadium, cobalt, nickel, zinc, tungsten, molybdenum, zirconium, tantalum, tin, and indium. An alloy comprising one or more metals,
Heat-resistant alloys such as Monel, Nichrome, and Inconel are exemplified. Further, oxides, nitrides, carbides, phosphorus compounds, and indium tin oxide (IT)
O), a composite oxide of the metal such as zinc chromate or the like can also be used as the adhesive layer.

The thickness of such an adhesive layer is 5 to 50 nm,
The thickness is preferably 5 to 20 nm, and within this range, there is an effect of improving the adhesive strength between the polymer substrate and the first metal layer and the heat resistance. Antioxidant layer The metal used for the antioxidant layer or the metal used for these oxides is a metal that is lower than the first metal layer. Here, the metal that is lower than the metal is a metal having a lower standard electrode potential in an aqueous solution system.

For example, in the present invention, considering that the metal used for the first metal layer is preferably a metal mainly composed of copper or copper, indium, tin, zinc and their oxides are used in the etching step. It is a preferable substance because it is a metal that can be easily dissolved and has a high antioxidant effect on the first metal layer. It is considered that the use of these metals can prevent the oxidation of the first metal layer by a kind of electrochemical action.

The method of forming such an antioxidant layer is not particularly limited, and can be appropriately selected based on the characteristics of the substance to be formed. For example, a wet method such as electroless plating, and a dry method such as an evaporation method, an ion plating method, an ion cluster beam method, and a sputtering method may be used. 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 the case where an oxide of a metal such as indium, tin, or zinc is used, a sputtering method capable of easily forming an oxide is preferable. Among the sputtering methods, a DC magnetron sputtering method is most efficient and can be formed at low cost. It is preferable because it is possible. Tin oxide, indium oxide and ITO are conductive substances, and zinc oxide is a substance having high conductivity by adding aluminum oxide or silicon oxide by several weight%, and easily formed by DC magnetron sputtering. It is a possible substance. These oxides are also readily available on the market.

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 effect of preventing oxidation. It is conceivable that the metal or metal oxide is not completely formed into a layer with such a thin film thickness, that is, an island shape (sea-island structure).
However, the effect of the present invention is not hindered at all. If the metal or metal oxide is not completely formed in a layered manner, such as when it grows into an island, the converted film thickness estimated from the film formation rate or the film thickness measured by a quartz crystal film thickness meter, etc. It is sufficient that the film thickness calculated from the weight and density of the applied substance is within the above range.

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. As described above, both sides of the polymer substrate may be used.
When forming a metal layer on both sides of the polymer substrate, a first metal layer and an antioxidant layer may be formed on each side, or the first antioxidant layer may be formed on both sides after forming the first metal layer. It may be formed on one metal layer. The deposition order of each metal layer is determined by a method suitable for the characteristics of the material used for each layer, such as a deposition apparatus, an evaporation apparatus, an ion plating apparatus, a sputtering apparatus, and a configuration of each apparatus, for example.
Whether it is a sputtering device that can form a film on both sides simultaneously, a vapor deposition device or an ion plating device, or a device that can perform sputtering and vapor deposition continuously in a roll-to-roll system,
The first metal layer is most efficiently applied to the present invention by appropriately considering whether the printed wiring material of the present invention is manufactured using two devices such as a sputtering device and an oxidation preventing layer using a vapor deposition device. The printed wiring board material described can be appropriately selected so that it can be manufactured.

By making a printed wiring board using such a wiring board material, the pitch between wirings is 100 μm.
In the following, preferably in a fine pattern processing of 50 μm or less, even if the thickness of the first metal layer is 1 μm or less,
Oxidation of the first metal layer can be prevented without lowering the yield, and productivity can be improved.

[0034]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto.

[0035]

Example 1 a polyimide film of 50μm thick as the polymer substrate, "Apical NPI" using (Kaneka Corporation), cut it to 8cm square, was placed on a substrate holder of a sputtering apparatus, ^10-3 Evacuation was performed to a pressure of Pa or less. Oxygen flow rate 100 SCCM, pressure
Plasma treatment of the polyimide film was performed under the conditions of 1.3 Pa, RF power of 100 W, and processing time of 3 minutes.

Then, a copper target (purity 99.99)
%) With an argon flow rate of 40 SCCM and a pressure of 0.2
Film formation was performed for 15 minutes under the conditions of 6 Pa and DC 180 W, and copper as the first metal layer was formed to a thickness of 250 nm. Further, the sample was taken out from the sputtering apparatus, placed in an electron beam heating type vapor deposition apparatus, and evacuated to a pressure of 10 ⁻³ Pa or less. A film was formed on copper with a thickness of. The zinc film thickness was controlled by a shutter that can be opened and closed in conjunction with a quartz crystal film thickness meter.

The thus prepared sample was heated at a temperature of 25.
It was left in a clean room of class 10000 at 50 ° C. and a humidity of 50% for 30 days, and visually inspected for appearance. The evaluation was performed based on the presence or absence of a discolored portion indicating oxidation of copper. However, no discolored portion was particularly 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 an antioxidant layer, but no discolored portion indicating oxidation of copper was generated. .

[0039]

Example 3 A sample was prepared and evaluated in the same manner as in Example 1 except that tin was formed in a thickness of 1 nm as an antioxidant layer, but no discolored portion indicating oxidation of copper was generated.

[0040]

Embodiment 4 A sample was prepared by forming zinc oxide to a thickness of 1 nm by sputtering instead of forming zinc as an antioxidant layer by an evaporation method in Example 1. That is, using a zinc oxide target (adding 3% by weight of aluminum oxide), an argon flow rate of 40 SCCM and a pressure of 0.2 were used.
Film formation was performed for 10 seconds under the conditions of 6 Pa and DC 180 W, and zinc oxide as an antioxidant layer was formed to a thickness of 1 nm.

When the obtained sample was evaluated in the same manner as in Example 1, no discolored portion indicating oxidation of copper was generated.

[0042]

Embodiment 5 Indium oxide was used as a sputtering target, and 1 indium oxide was used as an antioxidant layer.
A sample was prepared in the same manner as in Example 4 except that the sample was formed to have a thickness of nm, and evaluated in the same manner as in Example 1. However, no discolored portion indicating oxidation of copper was generated.

[0043]

Example 6 A sample was prepared in the same manner as in Example 4 except that tin oxide was formed to a thickness of 1 nm as an antioxidant layer using tin oxide as a sputtering target, and evaluated in the same manner as in Example 1. Was performed, but no discolored portion indicating oxidation of copper was generated.

[0044]

Embodiment 7 ITO as a sputtering target
(Tin oxide 20% by weight) as an antioxidant layer
A sample was prepared in the same manner as in Example 4 except that O was formed to a thickness of 1 nm, and evaluated in the same manner as in Example 1, but no discoloration indicating oxidation of copper was observed.

[0045]

Comparative Example 1 A sample was prepared and evaluated in the same manner as in Example 1 except that the antioxidant layer was not formed on copper, and a discolored portion indicating oxidation of copper was generated.

[0046]

According to the present invention, at least after forming the first metal layer on one side of the polymer substrate, an antioxidant layer made of a metal which is more noble than the first metal or an oxide thereof is used. By forming the layer to a thickness of 1 nm to 5 nm, it is possible to prevent oxidation of the first metal layer, and it is possible to prevent a decrease in adhesion of a 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 sectional view showing an example of a printed wiring board material of the present invention.

FIG. 2 is a sectional view showing an example of a printed wiring board material of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 polymer base material 102 first metal layer 104 antioxidant layer

Continued on the front page F term (reference) 4E351 AA02 BB01 BB32 BB33 BB35 CC03 CC06 DD04 DD12 DD35 GG13 5E343 AA02 AA16 AA18 AA33 BB16 BB24 BB34 BB52 BB57 BB59 BB71 DD22 DD25 DD32 GG08 GG11

Claims (6)

[Claims] 1. A polymer base material having a first metal layer on at least one surface thereof, and a surface of the first metal layer formed of a metal which is lower than the first metal layer or an oxide of such a metal. A printed wiring board material having an antioxidant layer. 2. The printed wiring board material according to claim 1, wherein said antioxidant layer has a thickness of 0.1 to 5 nm. 3. The printed wiring board material according to claim 1, wherein the first metal layer is made of copper or a metal mainly composed of copper. 4. The antioxidant layer according to claim 1, wherein the antioxidant layer is made of one or more metals selected from the group consisting of tin, indium, and zinc or oxides of these metals. The printed wiring board material according to the above. 5. The method according to claim 1, wherein said first metal layer has a thickness of 50 nm to 1 μm.
The printed wiring board material according to any one of claims 1 to 4, wherein m is m. 6. The printed wiring board material according to claim 1, wherein said polymer substrate is polyimide.