JPH0387324A - Copper alloy rolled foil for flexible printed wiring board - Google Patents

Abstract

PURPOSE:To manufacture the Cu alloy rolled foil for a flexible printed arising board having excellent ultra-fine workability, whisker resistance in the stage of Sn plating, heat resistance and electrical conductivity by subjecting a Cu alloy in which specified amounts of Ag, P, Zn, Sn and Co are incorporated into Cu and S, O2, etc., are extremely reduced to working into exceedingly thin foil. CONSTITUTION:A Cu alloy constituted of, by weight, 0.02 to 0.3% Ag, 0.02 to 0.04% P, >1.0 to 5.0% Zn, <10ppm S and the balance Cu as well as the total content of impurities and O2 is regulated to <=50ppm, or constituted of 0.05 to 0.2% Sn, 0.02 to 0.05% P, >1.0 to 5.0% Zn, <10ppm S and the balance Cu as well as the total content of impurities and O2 is regulated to <=50ppm or constituted of 0.15 to 0.25% Co, 0.04 to 0.08% P, >1.0 to 5.0% Zn, <10ppm S and the balance Cu as well as the total content of impurities and O2 is regulated to <=50ppm is rolled into foil having <=40mum thickness, which is then manufactured.

Description

Detailed Description of the Invention [Field of Application in Industry A] The present invention relates to a rolled copper alloy foil for flexible printing. The present invention relates to copper alloy rolled foil for use. For more information, see 8i
The present invention relates to a rolled copper alloy foil for flexible printing that has excellent microprocessability, whisker resistance when coated with Sn plating, heat resistance, and electrical conductivity.

[Prior Art] Copper foil with a thickness of 5 to 40 μm is often used in electrical circuits such as printed circuits. Such copper foils include electrolytic copper foils and rolled copper foils.

Printed circuit boards can be made by cladding copper foil on a substrate made of glass epoxy or paper phenol, and then forming the desired circuit pattern using a resist etching method, or by laminating the copper foil onto a film such as polyimide. There are also flexible circuit boards. Some of these are tape carriers, T A B (Tape Automated
Bonding) Used as a lead in mounting semiconductor chips. Rolled foil, which is superior in flexibility, is used for flexible circuit boards.

In recent years, with the miniaturization, higher density, and multifunctionality of electrical equipment, there has been a strong demand for higher density printed circuit boards, and for this reason, surface mounting methods that can mount small chip components at high density are gradually being adopted. It started to happen.

Recently, the pitches of tape carriers and TAB leads have become closer to each other with a pitch distance of 80 μm or less.

[Problems to be Solved by the Invention] Tough pitch copper and oxygen-free copper are usually used as rolled foils, but when using either as a lead, first a 5 μm thick Ni undercoat is applied to the part to be bonded to an electronic device. A 1 μm thick Au plating is formed thereon.

It has been common practice to use Ni underplating and Au plating as described above for connection parts where the lead-to-lead pitch of wiring is as narrow as 80 μm.

Although Au plating on Ni underplating is highly reliable, it is expensive, so an inexpensive Sn plating has been attempted as an alternative. However, in the case of Sn plating, there is a problem in that short circuits between wirings occur due to the generation of whiskers in a short period of time.

On the other hand, solder plating is being considered instead of Sn plating to prevent whiskers. However, this concept has not been put into practical use because solder plating causes problems such as poor solder adhesion.

The present invention relates to a copper alloy rolled foil, and instead of the conventional Cu rolled foil, the plating at the joint and its vicinity is replaced with Sn plating or solder plating instead of two-layer plating of Ni plating and Au plating. Moreover, the Sn plating layer does not generate any whiskers, the base material does not soften even when heated at 230°C during soldering, and the tin and solder do not peel off even after being held at 150°C for 1000 hours. Further, to provide a rolled copper alloy foil for flexible printing, which is a foil having high strength and conductivity, and which can be etched very neatly according to the target even when resist etching is performed with a thickness of 5 μm and a pitch of about 80 μm. With the goal.

[Means for Solving the Problems] The first gist of the present invention is that Ag: 0.02 to 0.3% (the same below weight%), P: 02 to 0.04%, Zn: 1
．． 0 to 5.0% (excluding 1.0%), 10pp
It is present in a rolled copper alloy foil for flexible printing, which is characterized by containing less than m of S, with the remainder consisting of Cu and impurities.

The second gist of the present invention is that Ag: 0.02-0.3%, P
: 0.02 to 0.04%, Zn: 1.0 to 5.0% (excluding 1.0%).

It is present in a copper alloy rolled foil for flexible printing characterized by containing 10 ppm or less of S, the total amount of impurities and oxygen being 50 ppm or less, and the balance being Cu.

The third gist of the present invention is that Sn: 0.05-0.2%, P
: 02 to 0.05%, Zn: 1.0 to 5.0% (excluding 1.0%), 10 ppm or less of S, and the balance consists of Cu and impurities. Present in printed copper alloy rolled foil.

The fourth gist of the present invention is that Sn: 0.05-0.2%, P
: 02 to 0.05%, zn: 1.0 to 5.0% (excluding 1.0%), contains 10 ppm or less of S, the total of impurities and oxygen is 50 ppm or less, the balance is Cu A rolled copper alloy foil for flexible printing is characterized by:

The gist of 'N%5 of the present invention is co=0.15~0225
%, P: 0.04-11.08%, Zn: 1.0-5.
0% (excluding 1.0%), 10ppm or less S
The copper alloy rolled foil for flexible printing is characterized in that it contains Cu and the remainder is Cu and impurities.

The sixth gist of the present invention is Co: 0.15 to 0.25%,
Contains P: 04 to 0.08%, Zn: 1.0 to 5.0% (excluding 1.0%), 10 ppm or less of S,
The copper alloy rolled foil for flexible printing is characterized in that the total amount of impurities and oxygen is 50 ppm or less, and the balance is Cu.

A seventh aspect of the present invention resides in the copper alloy rolled foil for flexible printing, which is characterized in that the thickness of the foil is 40 μm or less in the first to sixth aspects.

[Function] The effects and reasons for limitations of the contained elements of the present invention will be explained.

(Zn) Zn is Sn? ! Suppresses the generation of whiskers in Ff materials,
Increases electrical conductivity. For this purpose, it is necessary to contain Zn in an amount exceeding 1%.

When Zn is contained in an amount exceeding 1%, the formation of intermetallic compound (Cu, Sn) phases that deteriorate adhesion can be suppressed. This is thought to be because Zn suppresses the formation of Kirkendahloid that occurs on the base material side of the Cu and Sn phases, thereby improving adhesion.

In addition, a small amount of Zn diffuses into the Sn plating and relieves the internal stress of Sn, which seems to suppress whisker growth.

However, if the Zn content exceeds 5%, although there is no problem with whisker resistance, there are disadvantages such as electrical conductivity being less than 60% IACS and the tendency to cause stress corrosion cracking that is unique to brass. Therefore, the Zn content is set to 5% or less.

(S) Next, the reason for setting the upper limit of the S content will be described.

In conventional copper alloys, S is mostly Cu in copper alloys.
If Mn or Mg is contained as an impurity, it exists as MnS or MgS. It has been found that both of them are localized in grain boundaries, which causes problems during etching. With conventional copper alloys, when performing resist etching, especially when using foils with a thickness of 5 to 40 μm, the etching solution may be repelled due to poor adhesion of the resist, resulting in defects such as uneven etching. The present inventor investigated the cause. As a result, it was found that the cause of the problem was found in S. Therefore, in order to prevent problems from occurring, S
Although it is desirable to completely remove carbon dioxide, it is difficult to avoid contamination from raw materials, furnace materials, coated charcoal, fuel, etc., and the amount has been set at 10 ppm or less.

(Oxygen, impurities) Also, regarding oxygen and impurities, if the impurities exist in the form of oxides, they may inhibit microfabrication during etching in foils with a thickness of 5 to 40 μm, similar to S above. Understood, it was set at 50 ppm or less.

S1 Oxygen and impurities may appear on the surface of plates or strips with a thickness of 0.1 mm or more, but due to the size and
The number and amount is small and there is usually no need to limit the amount mixed in, but when the foil is 5 to 40 μm thick, pinholes occur during rolling, rolling breaks, and the aforementioned resist adhesion failure occurs. The inventor of the present invention has found that etching defects may occur, and has set the above-mentioned upper limit.

(Ag, P) Ag forms a solid solution in Cu and has the effect of improving strength and softening temperature. Such an effect does not occur at less than 0.02%.
If it exceeds 0.3%, the effect is saturated and it is not economical, so 0.
．． The upper limit is 3%.

In this case, P is an element necessary for deoxidizing the Cu alloy during the manufacturing process and for preventing hydrogen embrittlement cracking during annealing, and if it is less than 0.02%, the effect is small; %
If the amount exceeds 100%, these effects can be sufficiently exhibited, but solid solution occurs and the conductivity decreases.

Therefore, the P content when containing Ag is 0.02
~0.05%.

(Sn, P) Sn forms a solid solution in Cu and has the effect of improving strength and softening temperature. If it is less than 0.05%, it will not be possible to maintain the target heat resistance, and if it exceeds 0.2%, the conductivity will be 60%.
I become lower than AC5. Therefore, the Sn content is 0.05 to 0. 2%.

In this case, P is an element necessary for deoxidizing the Cu alloy during the manufacturing process and for preventing hydrogen embrittlement cracking during annealing, and if it is less than 0.02%, the effect is small; %
If the amount exceeds 100%, these effects can be sufficiently exhibited, but solid solution occurs and the conductivity decreases.

Therefore, the P content when containing Sn is 0.02
~0105%.

(Co, P) CO forms cobalt phosphide with P, which is an essential element for improving strength and preventing softening under temperature conditions. However, if it is less than 0.15%, P (content 0.04~
Even if cobalt phosphide is formed by combining with a part of cobalt phosphide (0.08%), if the effect of improving strength is exceeded, solid solute cO, which cannot form cobalt phosphide, will increase and reduce electrical conductivity. Become. Therefore, the content of CO is set to 0.15 to 0.25%.

P is an element that forms cobalt phosphide with CO and contributes to improving strength and softening temperature, but the content is 0.04%.
If the content is less than 0.0%, it will not contribute to strength improvement, etc.
If it exceeds 0.8%, solid solution P which cannot form a form of cobalt phosphide will increase, leading to a decrease in electrical conductivity. Therefore, C.O.
The P content in the case of containing is 0.04 to 0.08%.

[Example] Hereinafter, the present invention will be explained by examples.

Various alloys shown in Tables 1 to 3 are melted in a graphite pot,
Mold cast.

The ingot was machined to face 2.5 mm on each side.
0mmtx70mmwx200mmu, hot rolled at 900°C to a thickness of 10mm, cold rolled to a thickness of 0.2mm, and then intermediate annealed at 500°C x IHr.

Next, the foil was carefully pickled and cold-rolled repeatedly to produce a foil with a thickness of 35 μm, and pinholes and rolling breaks were observed.

In addition, foils with thicknesses of 5 μm and 65 μm were produced using the same procedure.

(Etching properties) For these foils, 50 resists were baked with a width of 100 μm, an interval of 80 μm, and a length of 20 μm, and chemical milling was performed using a 40% ferric chloride solution to produce 50 leads and examine their soundness. .

(Extent of whisker generation) After electric field degreasing in alkaline, current density 3A/d in sulfuric acid bath.
2, apply Sn plating to a thickness of 15 μm, attach a 0.2 mm copper alloy plate to the opposite side of the Sn plating using an epoxy resin adhesive, apply a compressive stress of approximately 4 kg/mm' by bending, and No. 8 (no change in content) After being left at room temperature for one year, the presence or absence of whiskers was investigated.

(Softening properties, electrical conductivity) Regarding the softening properties, IHr in an electric furnace under charcoal coating
The temperature at which 60% of the tensile strength was maintained was determined.

The conductivity was based on JISHO505.

The above test results are summarized in Tables 1 to 3.

Alloys containing 1 to 5% Zn do not generate whiskers even when Sn plating is applied to the surface, and by controlling S, oxygen, and other impurities, the thickness can be reduced to 5 to 5%.
Even for the 40 μm foil, the defect rate after resist etching was good at 2% or less.

In particular, with alloy foils other than the alloy foil of the present invention, when the thickness decreases to 5 to 40 μm, the etching property decreases significantly, but with the alloy of the present invention, there is almost no decrease. Even when heated, the softening temperature is 280°C or higher. In addition, tough pitch copper (No. 8) is also listed in the table as a conventional alloy.

[Effects of the Invention] According to the present invention, even if Sn plating is performed in place of the conventional Ni and Au plating, no whiskers occur at all.

Furthermore, the yield after ultra-fine processing is also improved.

Furthermore, it has a tensile strength that is significantly superior to conventional materials.

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

Procedural amendment (method) % formula % 1. Indication of the case 1999 Patent Application No. 66691 2. Name of the invention Copper alloy rolled foil for flexible printing 3. Person making the amendment Relationship to the case Patent applicant address Hyogo 1-3-18 Wakihama-cho, Fuchuo-ku, Kobe Prefecture Name (119) Kobe Steel, Ltd. Representative Sokichi Kametaka 4, Agent Address: 160 Telephone: 03 (358) 88
40 Address 12 Motoshio-cho, Shinjuku-ku, Tokyo 25th September 1990 The column of [Claims/Explanation] and [Details of the invention]

Claims (7)

[Claims] (1) Ag: 0.02-0.3% (same below weight%)
, P: 0.02-0.04%, Zn: 1.0-5.0%
A rolled copper alloy foil for flexible printing, characterized in that it contains 10 ppm or less of S (excluding 1.0%), and the remainder consists of Cu and impurities. (2) Ag: 0.02-0.3%, P: 0.02-0
．． 04%, Zn: 1.0 to 5.0% (however, 1.0%
A rolled copper alloy foil for flexible printing, characterized in that it contains 10 ppm or less of S, the total amount of impurities and oxygen is 50 ppm or less, and the balance is Cu. (3) Sn: 0.05-0.2% (same below weight%)
, P: 0.02-0.05%, Zn: 1.0-5.0%
A rolled copper alloy foil for flexible printing, characterized in that it contains 10 ppm or less of S (excluding 1.0%), and the remainder consists of Cu and impurities. (4) Sn: 0.05-0.2%, P: 0.02-0
．． 05%, Zn: 1.0 to 5.0% (however, 1.0%
A rolled copper alloy foil for flexible printing, characterized in that it contains 10 ppm or less of S, the total amount of impurities and oxygen is 50 ppm or less, and the balance is Cu. (5) Co: 0.15-0.25% (same below weight%), P: 0.04-0.08%, Zn: 1.0-5.0
% (excluding 1.0%) and 10 ppm or less of S, with the remainder consisting of Cu and impurities. (6) Co: 0.15~0.25%, P: 0.04~
0.08%, Zn: 1.0 to 5.0% (however, 1.0%
A rolled copper alloy foil for flexible printing, characterized in that it contains S of 10 ppm or less, the total amount of impurities and oxygen is 50 ppm or less, and the balance is Cu. (7) The rolled copper alloy foil for flexible printing according to any one of claims 1 to 6, wherein the foil has a thickness of 40 μm or less.