JP2809713B2 - Copper alloy rolled foil for flexible printing - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a rolled copper alloy foil for flexible printing, and more particularly, to a flexible printed copper foil used for wiring circuits such as printed circuits and tape carriers. The present invention relates to a rolled copper alloy foil. More specifically, the present invention relates to a rolled copper alloy foil for flexible printing which is excellent in ultrafine workability, whisker resistance when coated with Sn plating, heat resistance and conductivity.

[Prior Art] A copper foil having a thickness of 5 to 40 μm is frequently used in an electric circuit such as a printed circuit. Such copper foils include electrolytic copper foils and rolled copper foils.

On printed circuit boards, after cladding copper foil on a board made of glass epoxy, paper phenol, etc., in addition to the board formed into the desired circuit pattern by the resist etching method, copper foil can be bonded to a film such as polyimide There are also flexible circuit boards. Some of these are used for mounting semiconductor chips as tape carriers and TAB (Tape Automated Bonding) leads. For the flexible circuit board, a rolled foil excellent in flexibility is used.

In recent years, with the miniaturization, high density, and multi-functionality of electrical equipment, high density of printed circuit boards has been strongly demanded. For this reason, the surface mounting method that enables high-density mounting of small chip components is gradually adopted. Began to be.

In recent years, tape carriers and TAB leads have been approaching pitch distances of 80 μm or less.

Normally, tough pitch copper and oxygen-free copper are used as rolled foils, but when both are used as leads,
First, a 5 μm-thick Ni base plating is formed on a portion to be joined to an electronic device, and a 1 μm-thick Au plating is further formed thereon.

For the connection portions where the pitch between the wiring leads is as narrow as 80 μm, the above-described Ni base plating and Au plating coating were commonly used.

Au plating on Ni underlayer plating is highly reliable, but expensive, so inexpensive Sn plating has been attempted instead. However, in the case of Sn plating, there is a problem that a short circuit between wirings occurs due to generation of whiskers in a short time.

On the other hand, solder plating is being studied instead of Sn plating for whisker countermeasures. However, this concept has not been put to practical use because the formation of a brittle intermetallic compound ε phase causes a problem of poor solder adhesion in solder plating.

[Problem to be Solved by the Invention] The present invention relates to a copper alloy rolled foil, and instead of a conventional Cu rolled foil, plating at a joint and the vicinity thereof is performed by two-layer plating of Ni plating and Au plating to Sn. It can be replaced by plating or solder plating, and its Sn plating layer does not generate whiskers at all, the base material does not soften even by heating at 230 ° C during solder bonding, and tin and solder peel off It does not occur even after holding at ℃ x 1000Hr, and has high strength and electrical conductivity.
An object of the present invention is to provide a copper alloy rolled foil for flexible printing which can be etched very finely as intended even when photo-etched at a pitch of about 80 μm.

[Means for Solving the Problems] The first gist of the present invention is that Cr: 0.02 to 0.3%, P: 0.04% or less, Zn: 1.0 to 5.0% (excluding 1.0%), and 10 ppm or less of S And the balance consists of Cu and impurities.

The second gist of the present invention is that Cr: 0.02 to 0.3%, P: 0.04% or less, Zn: 1.0 to 5.0% (excluding 1.0%), contains 10 ppm or less of S, and contains impurities and oxygen. The total is 50 ppm or less,
The present invention resides in a rolled copper alloy foil for flexible printing characterized by the balance of Cu.

The third gist of the present invention is that Zr: 0.005 to 0.1%, P: 0.04%
Below, Zn: 1.0 to 5.0% (excluding 1.0%), 10ppm
The present invention resides in a rolled copper alloy foil for flexible printing characterized in that it contains the following S and is composed of the balance of Cu and impurities.

The fourth gist of the present invention is as follows: Zr: 0.005 to 0.1%, P: 0.04%
Below, Zn: 1.0 to 5.0% (excluding 1.0%), 10ppm
The rolled copper alloy foil for flexible printing is characterized in that it contains the following S, the total of impurities and oxygen is 50 ppm or less, and the balance is Cu.

A fifth gist of the present invention is that Cr: 0.02 to 0.3% and Zr: 0.0
0.005 to 0.3 at least one of 05 to 0.1%, P: 0.04% or less, Zn: 1.0 to 5.0% (excluding 1.0%), contains 10ppm or less of S, the balance of Cu and impurities The present invention relates to a rolled copper alloy foil for flexible printing characterized by comprising:

The sixth gist of the present invention is that Cr: 0.02 to 0.3% and Zr: 0.0
It contains 0.005 to 0.3 of at least one of 05 to 0.1%, P: 0.04% or less, Zn: 1.0 to 5.0% (except 1.0%), contains 10ppm or less of S, and contains impurities and oxygen. Present in a rolled copper alloy foil for flexible printing characterized in that the total is 50 ppm or less and the balance is Cu.

According to a seventh aspect of the present invention, there is provided a rolled copper alloy foil for flexible printing according to the first to sixth aspects, wherein the foil has a thickness of 40 μm or less.

[Operation] The effects of the elements contained in the present invention and the reasons for limitation will be described.

(Zn) Zn suppresses the generation of whiskers in the Sn coating material, improves the adhesion of Sn plating or solder plating, and lowers the conductivity. For that purpose, it is necessary to contain Zn exceeding 1%.

When Zn is contained in an amount exceeding 1%, generation of an intermetallic compound (Cu ₃ Sn) phase which deteriorates the adhesion of Sn plating or solder plating can be suppressed. This is considered to be due to the fact that Zn suppresses the formation of Kirkendall wedge generated on the base material side of the Cu ₃ Sn phase and improves the adhesion.

In addition, it is considered that a small amount of Zn diffuses into the Sn plating to reduce the internal stress of Sn, thereby suppressing whisker growth.

However, when Zn exceeds 5%, there is no problem in whisker resistance, but the drawbacks are that the electrical conductivity is less than 60% IACS and it has the characteristic of easily causing stress corrosion cracking unique to brass. Therefore, Zn is set to 5% or less.

(S) Next, the reason for setting the upper limit of the content of S will be described. In conventional copper alloys, S is often
When it exists as CuS and contains Mn or Mg as an impurity, it exists as MnS or MgS. All of them have been found to be localized in the grain boundaries, which causes problems during etching. In the case of a conventional copper alloy, particularly in the case of a foil having a thickness of 5 to 40 [mu] m, in the case of resist etching, defects such as poor adhesion of the resist and repelling of an etching solution have occurred. The present inventors have investigated the cause. As a result, it was found that the cause exists in S. Therefore, in order to prevent the occurrence of defects, it is desirable to completely remove S, but it is difficult to avoid contamination from raw materials / furnace materials, coated charcoal, fuel, and the like, and the content is set to 10 ppm or less.

(Oxygen and impurities) Also, when oxygen and impurities are present in the form of oxides, the foil having a thickness of 5 to 40 μm may impede the fine processing during etching as in the case of S described above. Understandable, it was determined to be 50ppm or less.

S, oxygen, and impurities, even if they appear on the surface of plates and strips with a thickness of 0.1 mm or more, have the size, number,
The amount is small, and it is not necessary to limit the amount that is usually mixed. However, when a foil having a thickness of 5 to 40 μm is formed, pinholes occur during rolling, rolling breakage, and the above-described poor adhesion of the resist and etching. The inventor has found that a defect or the like occurs, and sets the above upper limit.

(Cr) Cr has an effect of precipitating in Cu to improve strength and softening temperature. If it is less than 0.02%, such effect is small. A Cr precipitate having a diameter of more than 0.3% having a diameter of more than 10 μm appears and causes a problem in fine processing. Further, the upper limit is set to 0.3% because the flowability at the time of ingot making is reduced and the casting surface of the ingot becomes worse.

(Zr) Zr has the effect of forming a solid solution in Cu to increase the strength and softening temperature and to improve the heat resistance. If it is less than 0.005%, the target heat resistance cannot be maintained. If it exceeds 0.1%, the flow of molten metal at the time of ingot formation is reduced as in the case of Cr, the casting surface of the ingot is also deteriorated, and the yield is reduced.

 Therefore, the Zr content is set to 0.005 to 0.1%.

(P) P is required to be added in an amount of 0.02% or less for deoxidation at the time of agglomeration in the air. However, if it exceeds 0.04%, P forms a solid solution in Cu and lowers the electrical conductivity.

During ingot making in a reducing atmosphere or in a vacuum, oxygen in the molten metal or ingot becomes 10 ppm or less, and a deoxidizing agent is not required, so deoxidation with P is not required. Therefore, the upper limit of the P content is set to 0.04%.

EXAMPLES Hereinafter, the present invention will be described with reference to examples.

Various alloys shown in Tables 1 and 2 were melted with a graphite pot and cast in a mold.

The ingot is machined to cut the front and back sides 2.5mm each and 50mmt
X 70mmw x 200mml, hot-rolled to a thickness of 10mm at a temperature of 900 ° C, water-cooled from a temperature of 600 ° C or more, cold-rolled to a thickness of 0.2mm after removing oxide scale, and then 500 ° C x 1Hr intermediate Annealing was performed.

Next, pickling was carefully performed, and cold rolling was further repeated to produce a foil having a thickness of 35 μm, and pinholes and rolling cuts were observed.

Further, a foil having a thickness of 5 μm and a thickness of 65 μm were produced by the same procedure.

(Etching property) About these foils, width 100μm, interval 80μm, length 2
Bake 50 resists at 0μm, ferric chloride solution 40
Chemical milling at 50% produced 50 leads and investigated their soundness.

(About whisker) performs Sn plating thickness 1.5μm by the current density of 3A / dm ² in electric field degreasing after sulfate bath in an alkaline, 0.2 mm copper alloys opposite side and Sn plating adhesive epoxy resin After applying a compressive stress of about 4 kg / mm ² by bending and leaving it at room temperature for one year, the presence or absence of whisker formation was examined.

(Softening characteristics, conductivity) For softening characteristics, 1Hr in an electric furnace under charcoal coating
The temperature at which the temperature was maintained and maintained at 60% of the tensile strength was determined.
The conductivity was based on JISH0505.

 Table 1 summarizes the above test results.

An alloy containing 1 to 5% of Zn does not generate whiskers even if the surface is plated with Sn, and has a thickness of 5 to 40 by regulating S and oxygen and other impurities.
2% defect rate after photo-etching even for μm foil
The following was good.

In particular, in alloy foils other than the alloy foil of the present invention, when the thickness is reduced to 5 to 40 μm, the etching property is significantly reduced, but is hardly reduced in the alloy of the invention. In addition, it shows a softening temperature of 300 ° C. or more by heating such as soldering or heating for 1 hour, and does not soften at 230 ° C. during soldering. In the table, tough pitch copper (No. 10) is also described as a conventional alloy.

[Effects of the Invention] According to the present invention, even if Sn plating is performed instead of the conventional plating of Ni and Au, no whisker property is generated.

 In addition, the yield after ultrafine processing is improved.

Furthermore, it has a much higher tensile strength than conventional materials.

As described above, the present invention has excellent characteristics as a copper alloy foil for flexible printing, and has excellent characteristics as a material for miniaturization, high-density mounting, and multifunctionalization of electronic devices. .

Continuation of front page (56) References JP-A-62-146231 (JP, A) JP-A-63-310931 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 9 / 00-9/10 H05K 1/09

Claims (7)

(57) [Claims] (1) Cr: 0.02 to 0.3% (the same applies to weight% or less);
04% or less, Zn: 1.0-5.0% (excluding 1.0%), 10
A rolled copper alloy foil for flexible printing, comprising: S or less in ppm, and the balance being Cu and impurities. (2) Cr: 0.02-0.3%, P: 0.04% or less, Zn: 1.0-
Rolled copper alloy foil for flexible printing characterized by containing 5.0% (but excluding 1.0%) and 10ppm or less of S, the total of impurities and oxygen being 50ppm or less, and the balance being Cu. 3. Zr: 0.005 to 0.1%, P: 0.04% or less, Zn: 1.0
A rolled copper alloy foil for flexible printing characterized by containing up to 5.0% (excluding 1.0%), 10 ppm or less of S, and the balance of Cu and impurities. 4. Zr: 0.005 to 0.1%, P: 0.04% or less, Zn: 1.0
A rolled copper alloy foil for flexible printing, characterized in that it contains up to 5.0% (excluding 1.0%), 10 ppm or less of S, the total of impurities and oxygen is 50 ppm or less, and the balance is Cu. 5. An alloy containing 0.005 to 0.3 of at least one of Cr: 0.02 to 0.3% and Zr: 0.005 to 0.1%, P: 0.04% or less, Zn: 1.0 to 5.0% (excluding 1.0%). A rolled copper alloy foil for flexible printing, characterized by containing 10 ppm or less of S and the balance of Cu and impurities. 6. At least one of Cr: 0.02 to 0.3% and Zr: 0.005 to 0.1% is contained 0.005 to 0.3, P: 0.04% or less, Zn: 1.0 to 5.0% (excluding 1.0%). , Containing 10 ppm or less of S, the total of impurities and oxygen being 50 ppm or less,
Rolled copper alloy foil for flexible printing characterized by the balance of Cu. 7. The rolled copper alloy foil for flexible printing according to claim 1, wherein the thickness of the foil is 40 μm or less.