JPH11264037A - Copper alloy foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide Cu-Fe-P series copper alloy foil having sufficient strength and electrical conductivity and moreover excellent in productivity. SOLUTION: This foil is the one having a compsn. contg., by weight, 0.05 to 3.5% Fe and 0.01 to 0.4% P, furthermore contg., at need, one or two kinds of 0.05 to 5% Zn and 0.05 to 3% Sn, moreover contg., at need, one or more kinds among Mg, Co, Pb, Zr, Cr, Mn, Al, Ni, Si, In and B by 0.01 to 2% in total, and the balance Cu, in which the dimensions of inclusions are regulated to <=10 μm, and also, the number of the inclusions with 5 to 10 μm dimensions is regulated to <50 pieces/mm<2> in the cross-section parallel to rolling. It is suitable as a copper alloy foil material high in reliability in use for printed circuit boards and in a semiconductor packaging field such as IC tape carriers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy foil having excellent strength and electrical conductivity suitable for use in semiconductor mounting such as a flexible printed wiring board and an IC tape carrier. The present invention relates to a Cu—Fe—P based copper alloy foil in which the size and the number of inclusions are regulated.

[0002]

2. Description of the Related Art Printed wiring boards based on organic substances include rigid copper-clad laminates (rigid) made of glass epoxy and paper phenol boards, and flexible copper boards made of polyimide and polyester boards. Copper foil is mainly used as a conductive material of a printed wiring board. Copper foils are classified into electrolytic copper foils and rolled copper foils depending on the manufacturing method. Among the above printed wiring boards, a flexible printed circuit board which requires a multi-layer board and high flexibility by increasing the density of the printed wiring board is required to laminate a copper foil on a resin board and use an adhesive or heat and pressure. Are formed integrally. As the copper foil used, rolled copper foil of tough pitch copper or oxygen-free copper is often used, and in recent years, as an effective means of high-density mounting, a multilayer wiring board called a build-up board is often used. I have.

Further, a part of the printed wiring board is used as a tape carrier or TAB (tape automated bonding) lead for mounting a semiconductor chip. In the field of semiconductor chip mounting, in recent years,
BGA (Ball Grid Grid)
(Array) and CSP (chip size package). As a result, the number of terminals per area increases, but at the same time, the terminals have a narrow pitch, so that a high-density wiring board is also required for a mounting board. As an effective means for realizing high density, a multilayer substrate is also used in the field of semiconductor mounting.

On the other hand, in the manufacturing process, when the thickness of the foil is reduced, it becomes difficult to perform rolling at a high yield.
In particular, internal defects such as inclusions cause breakage during rolling and cause pinholes, thereby lowering productivity and consequently increasing manufacturing costs. Therefore, it is desired that the material has few inclusions. In recent years, for applications requiring high strength and conductivity, such as copper alloys for electronic equipment, precipitation-type copper alloys are often used. A Cu-Fe-P-based copper alloy is a typical precipitation-type copper alloy having both high strength and high electrical conductivity, and has been put to practical use as a material for electronic devices. In this alloy, strength and electrical conductivity increase due to precipitation of fine Fe or Fe—P-based compounds in the copper matrix during the aging precipitation process.

[0005]

The above-mentioned printed circuit board is (1) used while being fixed in a bent state at the time of assembling, and (2) a driving system (for example, a head portion of a printer, a driving circuit in a hard disk). Substrate and the like, which is repeatedly bent 10,000 times to 1,000,000 times or more. With the recent miniaturization and high density of electronic devices, miniaturization of the printed circuit board itself is required, and the strength of pure copper foil is insufficient, so that problems such as cutting or deformation occur when processing and assembling parts. In addition, since pure copper has a remarkably low heat resistance, there is a problem that a problem of deformation and disconnection occurs due to heating when laminating a copper foil on a resin substrate, and reliability is reduced.

[0006] In the field of semiconductor chip mounting, the circuit rules of mounted chips have been miniaturized.
The “0.1-0.2 μm rule” has been developed. 0.
In the case of the 1 to 0.2 μm rule, the pitch of the gold or aluminum bumps to be attached to the back of the chip is about 40 μm,
In order to bond bumps having a pitch of 0 μm, the wiring pitch of the substrate needs to be 15 μm or less. Wiring pitch is 1
In order to reduce the thickness to 5 μm or less, it is necessary to reduce the thickness of the copper foil used for the substrate to 14 μm or less. This is because etching and assembling cannot be performed unless the thickness of the copper foil is equal to or less than the pitch. However, in the conventional rolled copper foil,
When the plate thickness is 14 μm or less, a problem such as cutting or deformation occurs at the time of IRB (inner lead bonding) due to insufficient strength. Therefore, there is a demand for a material having sufficient strength and further sufficient electric conductivity to meet the above demand.

[0007] In order to meet the above requirements, it is one of effective means to use a copper alloy to which a certain additive element is added.
The use of a copper alloy alone does not always provide sufficient strength, and the addition of an element causes a problem such as a decrease in electrical conductivity, which is another required characteristic of the substrate. In the above-described Cu-Fe-P-based alloy, fine Fe or Fe-P-based precipitated particles are generated in the copper matrix, so that strength and conductivity are increased. Crystallization or precipitates are likely to remain, and because of the high activity of the added elements, oxides,
Since sulfides, silicides, and the like are easily generated, the result is that a structure in which these relatively large particles are dispersed in a matrix tends to be formed. In putting a Cu-Fe-P alloy to practical use as a copper alloy foil material, if these coarse particles remain, they cause breakage during rolling and cause pinholes, thereby lowering productivity and consequently reducing production costs. Cause an increase. The present invention has been made to solve the above-described problems, and has an object to provide a Cu-Fe-P-based copper alloy foil having sufficient strength and electrical conductivity, and also having excellent productivity. I have.

[0008]

Means for Solving the Problems Accordingly, the present inventors have:
After repeated research on copper alloy foil suitable as metal foil, C
After adjusting the components of the u-Fe-P-based alloy, if necessary, Zn and / or Sn, further Mg, Co,
Pb, Zr, Cr, Mn, Al, Ni, Si, In, and / or B are contained, and the production conditions are controlled and selected, and precipitates, crystals, oxides, sulfides, and silicides in the matrix are formed. By controlling the distribution of inclusions such as
It has been found that a material suitable as an alloy foil can be provided.
The present invention has been completed based on the above findings,
The copper alloy contains 0.05 to 3.5% by weight of Fe (hereinafter, the percentage means% by weight unless otherwise specified) and 0.01 to 0.4% of P, and 0.05 to 5% if necessary.
% Of Zn and 0.05 to 3% of Sn, and optionally Mg, Co, Pb,
One or more of Zr, Cr, Mn, Al, Ni, Si, In and B are contained in a total amount of 0.01 to 2%, and the balance is C
u and its unavoidable impurities, the size of inclusions is 10 μm or less, and 5 to 10 μm
The number of inclusions having a size of m is less than 50 pieces / mm ^2. The foil has sufficient strength and electrical conductivity as a foil for a printed wiring board or an IC tape carrier, and further has a productivity. Also relates to a good copper alloy foil.

In the present invention, the term "inclusion" means a precipitation reaction in a solid phase matrix after a solidification process during casting, ie, a cooling process after solidification, a cooling process after hot rolling, and an aging annealing. Microscopic observation of this alloy in the matrix, such as precipitates, generally coarse crystallized substances generated by segregation during the solidification process during casting, and impurities and oxides and sulfides generated by reactions in the molten metal during melting Used to encompass the observed particles. "Size of inclusions" refers to the diameter of the smallest circle containing the inclusions under microscopic observation. The “number of inclusions” is the number of inclusions per unit square mm actually counted at a number of places by microscopic observation of a rolled parallel section of the material.

[0010]

Next, the reason why the composition of the copper alloy in the present invention is limited as described above will be described together with its operation.

(Fe) Fe has an effect of improving the strength and heat resistance of the alloy alone or by forming an intermetallic compound with P, but if its content is less than 0.05%, it is desirable. High strength cannot be obtained. On the other hand, when Fe is contained in a ratio exceeding 3.5%, the workability is reduced, the conductivity is significantly reduced, and coarse Fe particles remain in the matrix. As a result, the productivity is lowered due to breakage during rolling, generation of pinholes, and the like. For these reasons, the content of Fe is determined to be 0.05% or more and 3.5% or less.

(P) P forms an intermetallic compound with Fe to improve the strength without lowering the conductivity.
When the content is less than 0.4%, the effect is not obtained. On the other hand, when the content is more than 0.4%, the workability is remarkably reduced and the conductivity is remarkably reduced.

(Zn) Zn acts as a deoxidizing agent at the time of melting and casting and has an effect of improving the heat resistance of the solder joint. However, if the content is less than 0.05%, the effect is remarkable. On the other hand, when the content of Zn exceeds 5%, the conductivity is significantly reduced, so that the Zn content is 0.0
5% or more and 5% or less.

(Sn) Sn has the effect of ensuring the strength of the alloy. However, if its content is less than 0.05%, the strength is not sufficiently improved, while if the Sn content exceeds 3%, the conductivity is increased. The Sn content is 0.05% or more and 3% or less since the hot workability of the alloy is lowered while the rate of reduction is remarkable.
It is determined as follows.

(Mg, Co, Pb, Zr, Cr, Mn,
Al, Ni, Si, In or B) Mg, Co, Pb,
Since Zr, Cr, Mn, Al, Ni, Si, In and B all have the same effect of improving the strength of the copper alloy, one or more of them may be added as necessary. However, if the total content is less than 0.01%, the effect of improving the strength cannot be obtained, while if the total content exceeds 2%, the conductivity is significantly reduced. And 0.01% or more and 2% or less.

(Inclusion) In this alloy system, inclusion particles may be present in the matrix. Inclusions for obtaining the necessary strength for this alloy are small, but coarse inclusions exceeding 0.5 μm do not contribute to the strength, and especially large ones cause breakage and pinholes in the rolling process, and Properties are significantly reduced. In order not to cause such a problem, the upper limit of the size of the coarse inclusions is set to 10 μm, and the number of inclusions having a size of 5 to 10 μm in the parallel rolling section is set to less than 50 / mm ^2. .

Next, a manufacturing process for obtaining this alloy will be described. In order to obtain desired strength and electrical conductivity, the tempered state of the material needs to be an aging state. This aging treatment is necessary to improve strength and electrical conductivity, but the aging treatment temperature needs to be 300 to 700 ° C. If the temperature is lower than 300 ° C., it takes a long time to perform the aging treatment, which is not economical. On the other hand, if the temperature is higher than 700 ° C., Fe forms a solid solution, and the aging does not improve the strength and electric conductivity. Next, the sheet is finished to a desired thickness by cold rolling, and the thickness of the foil after the cold rolling is desirably 100 μm (0.1 mm) or less, and a normal use form is assumed. The preferred thickness of the rolled copper alloy foil is, for example, 0.035 mm, 0.07 mm, 0.0
18 mm or 0.010 mm.

[0018]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. (Examples and Comparative Examples) Copper alloys having various component compositions shown in Table 1 were melted in a high-frequency melting furnace and cast into ingots having a thickness of 20 mm. Next, this ingot is heated at 800 to 950 ° C.
After hot rolling to a thickness of 8 mm at a temperature, and after facing the surface to remove scale, 2 mm thick by cold rolling
Plate. Then, after annealing for 1 hour at a temperature of 350 to 900 ° C., cold rolling was performed to 0.5 mm. After further aging for 5 hours at a temperature of 400 to 600 ° C., a foil having a thickness of 0.018 mm was formed by cold rolling.

Various properties were evaluated for each of the alloy foils thus obtained. In the table, tough pitch copper is also described as a conventional alloy. As for “strength”, the tensile strength was measured by a tensile tester. "Electrical conductivity" was indicated by conductivity (% IACS). The "heat resistance" was evaluated by heating at various temperatures for 30 minutes, and as a softening temperature a temperature at which the tensile strength was intermediate between the strength before heating and the strength when sufficiently softened. The number of inclusions was obtained by observing the rolled parallel cross section of the material with a microscope and counting the unit square mm
The number of inclusions having a size of 5 to 10 μm per hit. Moreover, thickness 0.018mm, width 450mm, length 5000
m was prepared, and productivity was also evaluated. "Productivity" was evaluated based on the occurrence of breaks during the rolling process and the occurrence of pinholes at the product stage. Regarding “break”, ○ indicates that no break occurred, and x indicates that break occurred.
"Pinhole" has a diameter of 0.1 m per 1000 m.
The number of generated pinholes of 5 mm or more was measured.

[0020]

[Table 1]

As can be seen from Table 1, the alloy foil of the present invention has excellent strength, electrical conductivity and heat resistance. Since the number of inclusions is small, the number of generated pinholes is small, up to six. On the other hand, the comparative alloy No. 1 is inferior in conductivity to the alloy of the present invention because of the higher Fe. Comparative alloy No.
Sample No. 2 has poor conductivity because of high Sn. Comparative alloy No. 3 is P
, The strength is inferior. Comparative alloy No.4
Has a low conductivity because both Fe and P are high. Comparative example
Nos. 1, 3, and 4 are examples in which breakage occurred during the manufacturing process due to a large number of inclusions, and the number of pinholes increased.

[0022]

As described above, according to the present invention,
Copper alloy foil with excellent strength, electrical conductivity and heat resistance, and also excellent productivity can be obtained.This alloy foil can be used for applications in the semiconductor mounting field such as printed wiring boards and IC tape carriers. It is suitable as a highly reliable copper alloy foil material.

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Claims (5)

[Claims] 1. The method according to claim 1, wherein 0.05 to 3.5% of Fe is contained.
And 0.01 to 0.4% of P, the balance being Cu and its unavoidable impurities, and the size of inclusions is 10 μm or less, and the number of inclusions having a size of 5 to 10 μm is A copper alloy foil having a rolled parallel cross section of less than 50 pieces / mm ² . 2. 0.05 to 3.5% by weight of Fe
And 0.01 to 0.4% of P, and 0.0
Contains one or two of 5 to 5% Zn and 0.05 to 3% Sn, the balance being Cu and its unavoidable impurities, and the size of inclusions is 10 μm or less, and A copper alloy foil, wherein the number of inclusions having a size of 5 to 10 μm is less than 50 / mm ² in a rolled parallel section. 3. The composition according to claim 1, wherein the content of Fe is 0.05 to 3.5% by weight.
And 0.01 to 0.4% P, further containing Mg,
Co, Pb, Zr, Cr, Mn, Al, Ni, Si, I
One or more of n and B are contained in a total amount of 0.01 to 2%, the balance is made of Cu and its unavoidable impurities, and the size of inclusions is 10 μm or less, and 5 to 1
The number of inclusions having a size of 0 μm is 50
A copper alloy foil having a size of less than ² mm ² . 4. 0.05 to 3.5% by weight of Fe
And 0.01 to 0.4% of P, and 0.0
It contains one or two of 5 to 5% Zn and 0.05 to 3% Sn, and further contains Mg, C
o, Pb, Zr, Cr, Mn, Al, Ni, Si, In
And B in a total amount of 0.01 to 2%, the balance being Cu and its unavoidable impurities, and the size of inclusions is 10 μm or less, and 5 to 1%.
The number of inclusions having a size of 0 μm is 50
A copper alloy foil having a size of less than ² mm ² . 5. An intermediate material obtained by subjecting an ingot to predetermined rolling and heat treatment is subjected to an aging treatment at a material temperature of 300 to 700 ° C. for 1 to 10 hours, and then to 0% in the final rolling. .
The copper alloy foil according to any one of claims 1 to 4, wherein the foil is finished to a thickness of 1 mm or less.