JP2764787B2 - High strength and high conductivity copper alloy for electronic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to excellent bending workability and pressability in addition to high strength and electrical conductivity, which are suitable as a lead material for semiconductor devices such as transistors and integrated circuits (ICs). The present invention relates to a high-strength, high-conductivity copper alloy for electronic equipment having punching properties.

[0002]

2. Description of the Related Art In recent years, the trend of IC packages has been symbolized by "miniaturization and lightness". Recently, however, the trend has been further promoted by the spread of surface packages.
At the same time, the increase in the number of pins and the reduction in heat generation accompanying the enhancement of the functions of the chip are also progressing. On the other hand, looking at a specific transition process relating to the form of an IC package, a pin insertion type package represented by DIP has been frequently used in the past. Becomes more mainstream, SOJ, S
The shift to surface mount types such as OP and QFP is progressing. Recently, fine pitch QFPs, in which the lead pitch has been reduced, have increased with the increase in the number of pins.
Thinning such as QFP is progressing.

[0003] By the way, most of the multi-pin, narrow-pitch frames are generally made by etching, but recently, partly because of the dramatic improvement in press micromachining technology, the production has been partially completed. Attempts are being made to incorporate good press working.

[0004] In any case, the lead frame as described above is used.
The thinning of the arm and the narrowing of the lead lower the lead strength,
The lead may be deformed during the assembly process or device mounting. Therefore, in order to solve such a problem, it is necessary to improve the strength of the lead frame material used as much as possible. Further, as the integration of ICs and the number of pins increase, power consumption increases, and measures to dissipate heat generated from chips become an important problem that cannot be ignored.

As described above, the lead frame material of semiconductor equipment is generally required to have the following various characteristics. a) The lead must have mechanical strength so that it is not easily deformed. b) It shall have the excellent etching and press workability required for forming the lead frame pattern. c) Chips High thermal conductivity to efficiently dissipate the heat generated by the device, d) excellent electrical characteristics, e) excellent solderability when mounting devices, and reliability of solder joints F) Ag plating for bonding, g) Excellent oxidation resistance without oxidizing the surface during the heating process, h) Excellent repetitive bendability I) The price is low.

However, in response to these various required characteristics, copper alloys such as phosphor bronze and the like which have been used in the past have been used.
All alloys (42 wt% Ni-Fe) had advantages and disadvantages, and none could satisfy all of the above characteristics. In particular, with the increase in the number of pins and miniaturization of leads, the complexity of the shape and the narrowing of the pins have advanced, and lead frame materials have better strength, bending workability, press punching properties, and the like. Considering that the etching property is required, it was difficult to say that the above-mentioned conventional material had sufficient performance in these points.

Accordingly, an object of the present invention is to provide a material which satisfies all of the above-mentioned characteristics required as a lead frame material of a semiconductor device or the like, in particular, a Vickers hardness of about 10%. It has a strength of 200 or more (65 kgf / mm ² or more in tensile strength) and a conductivity of more than 50% IACS (about 15 times that of 42 alloy), and also has sufficiently excellent bending workability and press punching properties. It is to provide a metal material.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and have reached the following conclusion. That is, a copper alloy based on copper, which originally has a very good thermal conductivity, is very advantageous in heat dissipation as compared with other lead frame materials, and has excellent electrical characteristics and properties.
Relatively good characteristics can be secured in terms of Ag plating properties, solderability, oxidation resistance, ductility, and the like. Therefore, if the strength, repetitive bending property, press punching property, etc., which can cope with thinning without impairing these characteristics can be improved to improve the drawbacks of the conventional copper alloy, the lead free of the future semiconductor equipment will be improved. It is considered that an excellent material such as a rubber material or a conductive spring material can be realized.

[0009] Therefore, it is one of the precipitation-type copper alloys capable of increasing the strength without lowering the conductivity as compared with the solid-solution-type copper alloy.
As a result of conducting research focusing on Cu-Cr-Zr alloy, the following findings were obtained. (a) Cr and Zr are very effective elements for increasing the strength of copper alloys, and Cr is a component that also contributes to the improvement of electrical conductivity. A sufficiently satisfactory strength cannot be ensured as a material or a conductive spring material, and the addition of Ti and Fe is effective for further improving the strength. (b) However, although Ti and Fe are very effective in improving the strength of the alloy, their contents greatly affect the etching properties and the electric conductivity, and so the disorderly addition must be avoided. However, in the copper alloy to which Ti and Fe are added, when the alloy components such as Cr, Zr, Ti, and Fe and the alloy component ratio are strictly controlled, various properties such as strength, electric conductivity, and etching property are at a high level. You will be able to balance. (c) However, the addition of these components alone cannot ensure sufficient press punching properties as a future lead frame material or the like. However, for the above copper alloy, S which is avoided as having a significant adverse effect on elongation is considered.
Is contained in a strictly regulated concentration, the press punching property is remarkably improved without adversely affecting the required properties such as elongation. (d) In addition, when the average crystal grain size is controlled to 60 μm or less by selecting the solution treatment temperature, the bending properties as well as the above-mentioned properties can be balanced at a high level. (e) Further, a predetermined amount of Zn, Sn, In, Mn, P, M
By adding g or Si, it is possible to further improve the reliability of the solder joint and the strength characteristics of the alloy.

The present invention has been made on the basis of the above findings and the like. "The copper alloy for electronic equipment is made of Cr: 0.05 to 0.40% (hereinafter,% representing the component ratio is referred to as a weight ratio), Zr : 0.03 to 0.25%, Fe: 0.10 to 1.80%,
Ti: 0.10 to 0.80%, S: 0.0005 to less than 0.0080%, or Zn: 0.05 to 2.0%, one or more of Sn, In, Mn, P, Mg, and Si: 0.01 to 1% in total amount Containing one or more of these, and a "0.10%
≦ Ti ≦ 0.60% ”, the Fe / Ti weight ratio satisfies 0.66 to 2.6, and“ 0.60% <Ti ≦ 0.80% ”, the Fe / Ti weight ratio is 1.
The strength, electric conductivity, bending workability, press punching property are satisfied by satisfying 1 to 2.6, with the balance consisting of Cu and unavoidable impurities and having an average crystal grain size adjusted to 60 μm or less. And that various properties such as the reliability of the solder joints can be balanced at a high level. "

Next, the "reason for limiting the component composition and crystal grain size of the alloy as described above" in the present invention will be described in detail together with its operation. A) Ingredient composition (a) Cr Cr precipitates in the mother phase by aging treatment following the solution treatment of the alloy, and exhibits the effect of improving its strength and electric conductivity, but the Cr content is less than 0.05% In this case, the desired effect cannot be obtained by the above operation. On the other hand, if the Cr content exceeds about 0.30%, undissolved Cr will remain in the matrix even after the solution treatment, and if the Cr content exceeds 0.40%, scum is likely to be generated after press working. This significantly impairs stable press punching. Therefore, the Cr content is 0.05-0.40%
It was decided.

(B) Zr Zr forms a compound with Cu by aging treatment and precipitates in a matrix to exert an effect of strengthening it.
If the content is less than 0.2%, the desired effect of the above-mentioned effect cannot be obtained. On the other hand, if the content exceeds 0.25%, undissolved Zr remains in the matrix even after the solution treatment, which lowers the electrical conductivity and bending workability. Therefore, the Zr content was determined to be 0.03 to 0.25%.

(C) Ti and Fe Ti and Fe form an intermetallic compound of Ti and Fe in the parent phase when the alloy is aged, and as a result, exhibit an effect of further improving the strength of the alloy. If the content of each of them is less than 0.01%, desired effects due to the above-mentioned effects cannot be obtained. On the other hand, if the Ti content exceeds 0.80% or the Fe content
If it exceeds 1.80%, undissolved inclusions containing Ti and Fe as main components have a size of 5 μm or more and significantly impair the etching property. What should be noted here is the effect of the Ti content and the Fe content on the strength and electric conductivity of the alloy. The strength and electric conductivity of the alloy are the same or the same.
The point is that even with the Fe content, it greatly changes depending on the Fe / Ti weight ratio. That is, in the range of “0.10% ≦ Ti ≦ 0.60%”, when the Fe / Ti weight ratio is less than 0.66, or “0.60%
% <Ti ≦ 0.80% ”, the electrical conductivity remarkably decreases in any case where the Fe / Ti weight ratio is less than 1.1. On the other hand, the strength of the alloy decreases when the Fe / Ti weight ratio exceeds 2.6 in the entire Ti content range of “0.10% ≦ Ti ≦ 0.80%”. That is, the electrical conductivity and the strength are in an inverse relationship with respect to the Fe / Ti weight ratio, and the optimal Fe / Ti weight ratio that balances the two at a high level is 0.66 in “0.10% ≦ Ti ≦ 0.60%”.
To 2.6, and 1.1 to 2.6 for "0.60% <Ti ≤ 0.80%"
It turns out that. Based on the above, the Ti content is set to 0.10 to 0.80% and the Fe content is set to 0.10 to 1.8% to satisfy the strength, electric conductivity and etching property of the alloy, respectively, and "0.10% ≦ Ti ≦ 0.60%”. % ”, The Fe / Ti weight ratio is 0.66 to 2.6, and“ 0.60% <Ti ≦ 0.80% ”
The Ti weight ratio was limited to 1.1 to 2.6, respectively.

(D) S S forms non-metallic inclusions in copper, but as the content increases, cracks originating from the non-metallic inclusions tend to occur and the elongation of the material decreases. However, this means that the area ratio of the sheared surface of the material at the time of press forming increases, and therefore, the occurrence of burrs and sagging is suppressed, which leads to remarkable improvement in press punching properties such as improvement in product accuracy. However, the S content is 0.0005
%, The desired effect of improving the press punching property cannot be secured, while if the S content is 0.0080% or more, the ductility is reduced, the repetitive bending property is significantly deteriorated, and the Ag plating property is also adversely affected. . Therefore, the content of S for improving the press punching property is determined to be 0.0005% or more and less than 0.0080%.

(E) Zn In the alloy according to the present invention, Zn exerts an action of improving the heat-peeling resistance of the solder, and is therefore a component that can be added if necessary. The desired effect due to the action cannot be obtained. On the other hand, if the content exceeds 2.0%, the conductivity will be reduced. Therefore, the Zn content is determined to be 0.05 to 2.0%.

(F) Sn, In, Mn, P, Mg and Si In the alloy according to the present invention, Sn, In, Mn, P, Mg and Si
In any case, one or two or more of these are added as necessary to exert the effect of improving strength mainly by solid solution strengthening without significantly lowering the conductivity of the alloy.
If their contents are less than 0.01% in total, the desired effects due to the above effects cannot be obtained. On the other hand, if their contents exceed 1.0% in total, the conductivity and bending workability of the alloy are deteriorated, and the punching property is adversely affected, and burrs are generated. Therefore, Sn, In, Mn, P, Mg
Alternatively, the total content of Si is set to 0.01 to 1%.

B) Crystal Grain Size The crystal grain size of the alloy has a remarkable influence on bending workability, and the smaller the crystal grain size, the better the bending workability (ie, the repetitive bending property). The crystal grain size can be adjusted by the solution temperature. However, when the average crystal grain size exceeds 60 μm, the number of times of repeated bending is significantly reduced. Therefore, in the present invention, the average crystal grain size is determined to be adjusted to 60 μm or less. .

Next, the effects of the present invention will be described more specifically with reference to examples.

EXAMPLES Copper alloys having various component compositions shown in Tables 1 and 2 were melted at 1200 ° C. in a high frequency melting furnace using electrolytic copper as a raw material, and cast into ingots. Then, the ingot was chamfered, heated at 950 ° C. for 1 hour, and hot-rolled to obtain a sheet material having a thickness of 8 mm. Next, this sheet material is subjected to a solution treatment at 900 ° C., and further a cold-rolled sheet material having a thickness of 0.3 mm is further subjected to aging treatment at 440 ° C. for 12 to 24 hours and cold rolling to a thickness of 0.15 mm. Finally, a strain relief annealing at 500 ° C. was performed. The crystal grain size (average crystal grain size) of each plate material thus obtained was examined. The results are shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

Next, the obtained sheet materials were released.
The evaluation items for the dough frame material are “tensile strength”, “elongation”, “electrical conductivity”, “repeated bending property”, “solderability”,
"Solder heat peeling resistance", "Ag plating property" and "press formability" were examined.

Here, "tensile strength" and "elongation" were measured by a tensile test, and "electric conductivity" was evaluated by electrical conductivity (% IACS). The evaluation criteria for tensile strength and conductivity are as follows:
The tensile strength was 65 kgf / mm ² or more, and the conductivity was 50% IACS or more. "Repeatable bendability" is defined as the number of times to break by performing a 90 ° repetitive bending test in the same direction under the bending condition of “(bending radius) / (plate thickness) = 1” and counting back and forth once. Was evaluated.
In addition, the evaluation criteria of the repetitive bendability were evaluated as acceptable (o) when the number of times of bending was 4 or more, and as negative (x) when the number of times of bending was less than 4 times.

"Solder wettability" was evaluated by measuring the zero-cross time by a surface tension method using a meniscograph using a solder checker. The solder used was 60% Sn-40% Pb, and the temperature of the solder bath was set at 230 ± 5 ° C. At this time, the zero-crossing time was allowed to be less than 1 second (○), and the zero-crossing time was not allowed to be more than 1 second (× ). "Solder heat peelability" is measured by applying 90% Sn-10% Pb solder plating of about 5μm thickness to the sample.
Hold in air at 50 ° C for up to 1000 hours,
Take out every 0 hours, "(bending radius) / (plate thickness) = 1"
Under the above bending conditions, 90-degree bending was performed once in a reciprocating manner, and the presence or absence of plating peeling at the bent portion was examined and evaluated. The evaluation criteria for the solder heat-peelability were acceptable (可) when the peeling start time exceeded 500 hours, and negative (x) when the peeling time was 500 hours or less.

"Silver plating property" means that a thickness of about 5 μm
m, and the sample was heated in the air at 350 ° C. for 3 minutes, and then evaluated by observing the presence or absence of swelling on the surface of the silver plating. In addition, the evaluation criteria of the silver plating property were evaluated as acceptable (○) when no blistering occurred, and as negative (x) when blistering occurred. The “press punching property” was evaluated by observing the surface of the sample with an optical microscope after breaking the sample with a press, and evaluating the shear surface area ratio and the occurrence of burrs. In addition, the evaluation criteria of the press punching property are as follows.
If the area ratio of the shear surface was less than 80%, the result was evaluated as "poor" (x). Here, the shear surface area ratio is Defined. Tables 3 and 4 show the evaluation results.

[0025]

[Table 3]

[0026]

[Table 4]

The following is clear from the results shown in Tables 3 and 4. That is, the present invention alloys 1 to 16,
All have a tensile strength of 65 kgf / mm ² or more, a conductivity of 50% IACS or more, a large shear surface area ratio, no burrs, repetitive bendability, solderability, solder heat resistance peeling, Ag It can be seen that the plating property and the etching property are all excellent.

On the other hand, since the comparative alloys 17 to 49 do not contain S, any of them has a low shear surface area ratio and burrs are generated. Comparative alloys 50 and 52 to 64 have an S content exceeding the upper limit specified in the present invention, have a good shear surface area ratio and no burr, but have deteriorated repeated bending property and Ag plating property. . Comparative alloys 65 and 70 had Sn contents exceeding the upper limit specified in the present invention, and had Sn, In, Mn,
Since the sum of the contents of P, Mg and Si is also higher than the upper limit specified in the present invention, burrs are generated and the repetitive bending property and Ag plating property are deteriorated. In the comparative alloy 51, since the S content is lower than the lower limit specified in the present invention, burrs are generated and there is no effect of improving the press punching property.

In the comparative alloys 31 and 32, the Cr content or the Zr content also exceeded the upper limit specified in the present invention, and the repetitive bending property deteriorated and burrs were generated. Comparative alloy 51
And 52 have a low Cr content of less than 65 kgf / mm ² because the Cr content is below the lower limit specified in the present invention. Also,
The comparative alloys 33 and 54 have a low strength of less than 65 kgf / mm ² because the Zr content is lower than the lower limit specified in the present invention.

The comparative alloys 37, 38, 40, 58 and 59 have a low strength of less than 65 kgf / mm ² because the Fe / Ti weight ratio exceeds the upper limit specified in the present invention. Comparative alloys 36, 39, 60 and 62
Since the Fe / Ti weight ratio is less than the lower limit specified in the present invention, the electrical conductivity is as low as less than 50% IACS.

The comparative alloys 42 and 63 have a conductivity of 50% IACS because the Zn content exceeds the upper limit specified in the present invention.
It is lower than less. Comparative alloys 44-47 and 49 are Sn,
Since the total amount of In, Mn, P, Mg, and Si exceeds the upper limit specified in the present invention, the electrical conductivity decreases and the repetitive bending property deteriorates. The comparative alloy 35 has a crystal grain size exceeding 60 μm and is out of the range specified in the present invention, so that the repetitive bending property is deteriorated.

[0032]

[Summary of effects] As described above, according to the present invention, the tensile strength, elongation, electrical conductivity, bending workability, press punching property, Ag plating property, solderability and solder heat-peelability are high, and the surface It is possible to provide "high strength and high conductivity copper alloy suitable for electronic equipment such as lead frame material and conductive spring material" which has excellent characteristics and reliability, and improves the performance of electronic equipment. Industrially extremely useful effects such as a large contribution can be obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-51674 (JP, A) JP-A-63-130737 (JP, A) A. CALLCUT ET AL. , "COPPERS FOR E LECTRICAL PURPOSE S", IEEE PROCEEDING S, JUNE 1986, VOL. 133, P ART A, NO. 4, p. 174-201 (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 9/00-9/10 H01L 23/48 H01L 23/50

Claims (4)

(57) [Claims] (1) Cr: 0.05 to 0.40%, Zr: 0.03 to 0.25%, Fe: 0.
10 to 1.80%, Ti: 0.10 to 0.80%, S: 0.0005% or more
In addition to containing less than 0.0080%, “0.10% ≦ Ti ≦ 0.60%”
The weight ratio satisfies 0.66 to 2.6, and “0.60% <Ti ≦ 0.80
% ", The Fe / Ti weight ratio satisfies 1.1 to 2.6, the balance consists of Cu and unavoidable impurities, and the average crystal grain size is adjusted to 60 μm or less. Highly conductive copper alloy. 2. Cr: 0.05 to 0.40%, Zr: 0.03 to 0.25%, Fe: 0.
10 to 1.80%, Ti: 0.10 to 0.80%, S: 0.0005% or more
Less than 0.0080%, Zn: 0.05 to 2.0%, and “0.10% ≦ Ti ≦ 0.60%”, Fe / Ti
The weight ratio satisfies 0.66 to 2.6, and “0.60% <Ti ≦ 0.80
% ", The Fe / Ti weight ratio satisfies 1.1 to 2.6, the balance consists of Cu and unavoidable impurities, and the average crystal grain size is adjusted to 60 μm or less. Highly conductive copper alloy. (3) Cr: 0.05 to 0.40%, Zr: 0.03 to 0.25%, Fe: 0.
10 to 1.80%, Ti: 0.10 to 0.80%, S: 0.0005% or more
Less than 0.0080%, and at least one of Sn, In, Mn, P, Mg and Si: 0.01 to 1 in total
%, And in “0.10% ≦ Ti ≦ 0.60%”, Fe / Ti
The weight ratio satisfies 0.66 to 2.6, and “0.60% <Ti ≦ 0.80
% ", The Fe / Ti weight ratio satisfies 1.1 to 2.6, the balance consists of Cu and unavoidable impurities, and the average crystal grain size is adjusted to 60 μm or less. Highly conductive copper alloy. (4) Cr: 0.05 to 0.40%, Zr: 0.03 to 0.25%, Fe: 0.
10 to 1.80%, Ti: 0.10 to 0.80%, S: 0.0005% or more
Less than 0.0080%, Zn: 0.05 to 2.0%, and at least one of Sn, In, Mn, P, Mg and Si: 0.01 to 1 in total amount
%, And in “0.10% ≦ Ti ≦ 0.60%”, Fe / Ti
The weight ratio satisfies 0.66 to 2.6, and “0.60% <Ti ≦ 0.80
% ", The Fe / Ti weight ratio satisfies 1.1 to 2.6, the balance consists of Cu and unavoidable impurities, and the average crystal grain size is adjusted to 60 μm or less. Highly conductive copper alloy.