JPS6141751A - Manufacture of copper alloy material for lead frame - Google Patents

Abstract

PURPOSE:To manufacture the titled Cu alloy material having superior characteristics such as strength, electric conductivity, bendability and hardness by hot working a Cu-Cr-Zr alloy ingot contg. specified amounts of Zr and Cr and by subjecting the hot worked material to proper cold working, aging and annealing. CONSTITUTION:A Cu-Cr-Zr alloy ingot contg. 0.03-0.14wt% Zr and 0.2-1.5wt% Cr is subjected to prescribed hot working such as rolling, forging or extrusion. The hot rolled material is subjected to primary cold working at 30-80% reduction of area, prescribed aging at 450-500 deg.C for about 2-5hr, and secondary cold working at >=80% reduction of area to form a material of desired about 0.2mm. thickness. This thin material is annealed at about 250-450 deg.C below the aging temp. for about 5min-1hr to obtain a Cu alloy material for a lead frame having superior characteristics such as strength, electric conductivity, bendability and hardness.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a method for manufacturing a copper alloy material for lead frames.
Cu (copper) has excellent properties such as strength and electrical conductivity.
The present invention relates to a method for manufacturing a lead frame material that is Cr (chromium)-Zr (zirconium) based and has further improved various properties such as conductivity, flexibility, and hardness without impairing its strength.

Prior art In recent years, electronic equipment parts, especially ceramic-sealed or resin-sealed package metal materials for semiconductor circuits such as integrated circuits, so-called lead frame materials, have been developed to have electrical conductivity, heat resistance, flexibility, and solderability. Various copper alloy materials that have required properties such as hardness have been studied, and for example, Japanese Patent Publication No. 58-39901 describes a Cu-Cr-Zr alloy material as one such copper alloy material. However, those currently in practical use include oxygen-free copper, phosphor bronze, iron-containing copper, and tin-containing copper. Therefore, these materials are conductive (501 alloy).

194 alloy) and heat resistance at the same time. By the way, as the degree of integration of semiconductor circuits increases, there is an increasing demand for improvement in the above-mentioned characteristic values.
In order to meet this requirement, the practical use of precipitation hardening copper alloy materials that undergo solution treatment, quenching treatment, cold working, and aging annealing treatment is being considered.

On the other hand, as a representative example of a precipitation hardening type copper alloy, the present inventors previously discovered that 0.3 to 1.5% of Cr and 0.03 to 1.5% of Zr were used.
JP-A-56-20135 discloses a copper alloy containing at least 0.14% of St (silicon) and, if necessary, 0.01 to 0.08% of St (silicon) together with these components.
(see Japanese Patent Publication No. 2003-111000), and it was revealed that such a copper alloy is useful as an electrode material for resistance welding.

Problems to be solvedHowever, such precipitation hardening type Cu-Cr-Z
When using r-based alloys for lead frames, the degree of cold working is significantly greater than in conventional applications.
In general, the final plate thickness is approximately 0.2 to 0.3 fi, and the degree of cold working is 90% or more, so the performance required for lead frame materials, such as high electrical conductivity, 90° repeated bending, etc. It has become clear that the properties such as high softening temperature are not necessarily satisfied, and disadvantages such as decreased ductility and electrical conductivity occur.

Solution The inventors conducted various studies to obtain a useful lead frame material from a Cu-Cr-Zr precipitation hardening alloy, and as a result of optimizing the manufacturing process, the required performance as described above was achieved. They have discovered that it is possible to improve this, and have arrived at the present invention.

That is, the present invention provides 0.03% to 0.03% on a weight basis.
After performing prescribed hot working on a Cu-Cr-Zr steel alloy ingot containing at least 14% Zr and 0.2% to 1.5% Cr, 30 to 80% After performing a first cold working at a working degree, then performing a predetermined aging treatment, a second cold working is performed at a working degree of 80% or more, and then a temperature lower than the aging treatment temperature. The sintering treatment was performed at a low temperature.

The copper alloy material for lead frames obtained in this way maintains the strength required for lead frame materials, while maintaining its electrical conductivity (air conductivity), flexibility, and even hardness. , ductility, etc. are effectively increased.

By the way, Cr, which is an alloying component in the copper alloy used in the present invention, is an element that improves strength.
There is a limit to the strength improvement effect caused by this, and that is 1.5
% (based on weight, hereinafter the same), it does not contribute much to increasing the strength, and on the contrary, it causes problems such as increased costs. On the other hand, if the amount added is less than 0.2%, the strength improvement effect is not achieved. The amount of Cr added is 0.2 to 1.5%, preferably 0.5 to 1.0%, since it becomes insufficient and cannot maintain sufficient strength as a lead frame material.
It is necessary to stop within the range of .

In addition, Zr, which is an essential component added together with Cr, is an element that finely disperses Cr within the alloy structure, maintains good electrical conductivity of Cu, and also contributes to increasing strength. When the amount added is less than 0.03%, the quenching sensitivity, strength, and heat resistance of the alloy can be sufficiently improved, while when it exceeds 0.14%, properties such as electrical conductivity are deteriorated. In addition, since it cannot contribute to the improvement of strength, the amount added is 0.03% to 0.1%.
It needs to be 4%. Note that the desirable addition ratio of Zr is less than 0.10%, particularly 0.04 to 0.0%.
It is about 8%. In addition, the amount of Zr added was 0.10%.
By keeping the corrosion resistance to less than 1, it is possible to effectively improve the corrosion resistance of the resulting copper alloy material for lead frames, especially the stress corrosion cracking resistance.

Furthermore, in the present invention, in addition to the above-mentioned Cr and Zr, it is also possible to add St as needed to use it as a quaternary alloy system, and by adding such Si, the alloy can be improved. By improving heat resistance, it is possible to impart advantageous properties as a material for lead frames.

Therefore, when the amount of Si added is less than 0.01%, the effect of improving heat resistance can be sufficiently exhibited;
Excessive addition of St exceeding 0.05% causes problems such as a decrease in electrical conductivity; therefore, the amount of St added is limited to 0.000%.
It is desirable to keep it at 0.01 to 0.08%, and generally 0.01% to 0.08%.
．． A range of 0.02% to 0.04% is preferably adopted.

And Cu according to the present invention having such an alloy composition
- Cr-Zr steel alloys are produced in the same manner as before, using copper base metal, intermediate alloys, and/or additive elements as appropriate, and are made into specified copper alloy ingots. The copper alloy ingot is subjected to predetermined hot processing such as rolling, forging, etc. in order to make it into the intended lead frame material.
Processing such as extrusion will be performed. Note that at this time, it is possible to omit the solution treatment for the copper alloy material.

Further, the raw material obtained by such hot working, that is, the hot working material, is then subjected to first stage cold working such as rolling, forging, drawing, etc. according to the present invention. This first stage cold working is carried out at a medium level, and is carried out so that the degree of working is within the range of 30 to 80%.

Furthermore, the material subjected to such first stage cold working,
The aging treatment inherent to the alloy of the present invention, in other words, the aging annealing treatment is carried out. Note that this aging annealing treatment is generally carried out at a temperature of 450 to 500°C for 2 to 5 hours. In addition, since such aging annealing treatment is carried out at a relatively thick stage of the material, mechanical or chemical surface cleaning can be carried out technically easily, and therefore such treatment is not recommended. The sintering treatment can also be carried out in air, and in this respect it is possible to reduce costs.

Next, the material thus aged and purified is subjected to cold working again. This second stage of cold working is a strength process, and a working degree of 80% or more is adopted, which results in the desired thin-walled product of around 0.2fi. .

Then, the material subjected to the second stage cold working is subjected to a short-time sintering treatment at an even lower temperature, that is, at a temperature lower than the above aging treatment temperature. Become. Note that this sintering treatment is generally carried out at a temperature of 250° C. to 450° C. for 5 minutes to 1 hour.

By performing such a sintering treatment after the second-stage high-strength cold working, the second-stage heat treatment is performed at a temperature lower than that in the aging sintering treatment, preferably at a temperature of 250 to 350°C. Not only can it recover the performance deterioration peculiar to highly processed materials obtained through cold working, such as deterioration in electrical conductivity and 90° repeated bending properties, but also the material strength can be effectively improved. The mechanism of this improvement in strength and recovery of ductility is not yet clear, but it is speculated that this is probably due to the progress of cell structure formation accompanying low-temperature sintering.

In addition, unlike the previous aging annealing treatment, the metal structure change due to such low-temperature sintering treatment is not accompanied by precipitation of supersaturated elements such as Cr and Zr, but due to dislocations etc. introduced by intense cold working. It concerns the rearrangement of lattice defects. Therefore, as mentioned above, the sintering time is 5 minutes to 1 hour, whereas the pre-stage aging sintering process usually takes about 2 to 4 hours.
Usually, a time of about 5 to 30 minutes is sufficient, and it is possible to use either a bunch type furnace or a continuous sintering furnace as the sintering equipment. Moreover, the treatment temperature is 450 to 500°C for the aging treatment in the first stage, while the treatment temperature in the latter stage is about 250 to 450°C.
It is not difficult to manufacture, therefore, it is easy to manufacture and does not involve much increase in cost.

Effects of the Invention According to the present invention, the copper material for lead frames manufactured from the Cu-Cr-Zr steel alloy ingot can be used for conventional copper alloy lead frames without any loss in its good strength properties. It is a material for lead frames of semiconductor circuits such as integrated circuits because its electrical conductivity is effectively improved compared to other materials, and it also has excellent flexibility, 90° repeated bending characteristics, hardness, etc. It is suitable as a material for lead frames, and also shows superior usefulness compared to phosphor bronze, soot-containing copper, iron-containing copper alloy, etc., which have been considered to have excellent characteristics as materials for lead frames. It is.

EXAMPLES In order to clarify the present invention more specifically, some examples of the present invention will be shown below, but the present invention shall not be limited in any way by the description of such examples. It goes without saying that. Furthermore, it should be understood that the examples illustrated here are only a portion of the numerous experiments conducted by the present inventors.

Example 1 0.7% by weight of Cr and 0.05% by weight of 7. 1100m x 150n consisting of an alloy composition of r and the remainder Cu
An ingot of X5Q was melted, and this ingot was hot-rolled at a temperature of about 930°C until it had a thickness of 15mm. After performing the first stage of cold rolling to (working degree -67%), a sintering aging treatment was performed at a temperature of 475° C. for 4 hours.

After this, the depth further increases to 0.25m (processing degree -95%)
A second stage of cold rolling was performed, and then various finishing annealing treatments were performed at temperatures of 200 to 450° C. for 10 minutes as shown in Table 1 below.

The thus obtained sintered material was subjected to hardness measurements, tensile tests, bending tests, and electrical conductivity measurements, and the results are shown in Table 1 below.

In addition, in the bending test, the sample material was sandwiched between jigs with a bent corner of 0.2 R, and repeated bending at an angle of 90° was performed.
″→90°−09 was counted as one time, and the number of times until breakage was shown.

As is clear from the results in Table 1, by applying a low-temperature finish sintering treatment, the electrical conductivity, bending, hardness, etc. are improved compared to materials that have not been subjected to such sintering treatment. improved, especially at sintering temperatures of 250°C or higher, especially 30°C.
It is understood that improvements in each characteristic value are observed at temperatures above 0°C.

Example 2 Various alloy compositions shown in Table 2 below were prepared.
Melt a specified copper alloy molten metal in a high-frequency electric furnace using an electrolytic copper ingot, an intermediate alloy, and/or an additive element as appropriate,
Then, by casting, various desired copper alloy ingots for lead frames (150nX 100n
X 50n) was agglomerated.

Next, using the obtained copper alloy ingots of Samples 1 to 10, each was hot rolled at a temperature of about 930°C to a thickness of 150°C, and then the hot rolled material was rolled into a plate. The first stage of cold rolling was performed until the thickness became 5ms (working degree -67%), and then the sintering aging treatment was performed at a temperature of 475°C for 4 hours.
, 5 am (working degree -90%), and then a final sintering treatment was performed at a temperature of 350° C. for 10 minutes.

The various sintered materials thus obtained were subjected to tensile tests, bending tests, heat resistance tests, and electrical conductivity measurements in the same manner as in Example 1, and the results were compared to those for conventional lead frames. Along with the materials (11m11-13),
It is also shown in Table 3 below.

In addition, the heat resistance (softening temperature) and bendability (
The evaluation symbols (number of times) have the following meanings.

Table 2 Table 3 As is clear from the results in Tables 2 and 3, the sintered materials Arashi 1 to Magne 5, which are made of alloy compositions according to the present invention, all have excellent tensile strength. However, the comparative products and the conventional materials in Nos. 6 to 13 all have some inherent defects. That's what I'm doing.

In addition, if Zr in the alloy composition significantly exceeds the specified value (upper limit), it will not be sufficiently hardened in the air cooling process after hot rolling at 930°C, resulting in mechanical problems in the final product. This causes problems such as insufficient performance, or in other words, poor strength and decreased electrical conductivity.

Example 3 0.90 wt% Cr, 0.08 wt% Zr, 0.0
A 100 m x 100 m x 150 Yoiho ingot having an alloy composition containing 3% by weight of St and the balance being Cu was melted, and this ingot was hot rolled at a temperature of about 930°C to a thickness of 15 mm. Next, this hot rolled material was subjected to first stage cold rolling, sinter aging treatment, second stage cold rolling, and finishing under various conditions as shown in Table 4 below. A sintering treatment was performed to obtain various desired sintering treatment materials.

The various sintered materials thus obtained were subjected to tensile tests, bending tests, heat resistance tests, and electrical conductivity measurements in the same manner as in Example 1, and the results are shown in Table 5 below. Note that the evaluation symbols for bendability and heat resistance in Table 5 have the same meanings as in Example 2.

Table 5 As is clear from the comparison of Tables 4 and 5, the first cold rolling improves the tensile strength of the material, and the electrical conductivity, bendability and heat resistance of the material. The influence of the second stage cold rolling is large, and according to the present invention, the first stage cold rolling is
By performing the second stage cold rolling with a working degree of 0 to 80% and a working degree of 80% or more, desired properties such as tensile strength, electrical conductivity, bendability, It is understood that a lead frame material that satisfies all heat resistance requirements can be obtained.

Claims (1)

[Claims] C containing at least 0.03% to 0.14% zirconium and 0.2% to 1.5% chromium on a weight basis
After performing predetermined hot working on the u-Cr-Zr steel alloy ingot, a first cold working was performed at a working degree of 30 to 80%, and then a predetermined aging treatment was performed. After that, 8 more
A method for manufacturing a copper alloy material for a lead frame, comprising performing a second cold working at a working degree of 0% or more, and then performing a sintering treatment at a temperature lower than the aging treatment temperature.