JP4100629B2 - High strength and high conductivity copper alloy - Google Patents

Description

  The present invention relates to a copper alloy for electronic parts having excellent bending workability and high strength and high conductivity, and particularly in a small and highly integrated copper alloy for semiconductor device leads and terminal connector springs. -It is related with the copper alloy for electronic components which was excellent in thermal conductivity, and excellent in especially a high strength characteristic.

Copper and copper alloys are widely used materials for electronic parts such as connectors and lead terminals, and flexible circuit boards, and the rapid development of IT has led to higher functionality and smaller size of information equipment. The copper and copper alloys are required to have further improved characteristics (strength, bending workability, conductivity) in response to the reduction in thickness and thickness.
Terminals and connectors used in electronic electrical components are required to have high strength, high conductivity, and good bending workability as electronic and electrical devices become smaller and lighter. In addition, with high integration of LSI, semiconductor elements with high power consumption are often used, and Cu-Ni-Si based copper alloys with good heat dissipation and conductivity are used for lead frame materials of semiconductor devices. Came to be used. However, in general, in lead frame processing for ICs and the like, the lead terminals are bent at a right angle after forming the lead terminal part and the conductive connection part with the IC by stamping method or etching method, etc. In addition to conductivity, strength, in particular, excellent bending workability is required. Therefore, when precipitation hardening type copper alloy is applied to a lead frame, strength and bending workability are required in addition to conductivity. However, conductivity and strength are generally incompatible.
In the prior art, the amount of Ni, Si, O component in the Cu-Ni-Si-based copper alloy is adjusted, and the particle size of the precipitate, the precipitate having a particle size of less than 0.03 μm, the precipitate of 0.03 to 100 μm, An alloy with a controlled number ratio is known (for example, Patent Document 1). However, the invention described in Patent Document 1 is for producing a Cu—Ni—Si based copper alloy suitable for shearing such as punching, and is excellent in conductivity and shearing workability. It did not have a good bending workability.
JP-A-10-219374

  Therefore, the present invention has sufficient strength as a lead frame material for spring materials and semiconductor devices without compromising the excellent thermal conductivity and conductivity of the Cu—Ni—Si based copper alloy, and also has bending workability. The purpose was a copper alloy.

As a result of repeated research to achieve the above object, the present inventors have adjusted the components of a Cu-Ni-Si based copper alloy having excellent strength, conductivity, springiness, etc. It has been found that by adjusting the shape, size, and area ratio of an object within a specified range, a copper alloy having unprecedented high strength can be obtained without impairing high conductivity and bending workability.
The present invention has been completed based on the above findings. In a copper alloy, Ni: 1.5% or more and 4.0% or less (where,% in the description of the present invention is mass%), Si: 0.15% or more and 1.0% or less, Ni / Si content ratio Ni / Si: 3 or more and 7 or less, O: 0.0050% or less, the balance being Cu and inevitable impurities And a Ni—Si-based precipitate having a major axis: a and a minor axis: b, a: 20 nm to 200 nm and an aspect ratio a / b: 1 to 3 By occupying 80% or more in the area ratio of all precipitates contained in the copper alloy, excellent conductivity and thermal conductivity, strength, which can be sufficiently satisfied as a conductive spring material, or a lead material of semiconductor equipment, Specially designed for both springiness and bending workability Has, preferably a characteristic value of the tensile strength 800～1000MPa, conductivity 35 to 55% IACS. When one or more of Zn, Mg, Sn, and In are contained in the above component composition in an amount of 0.01% to 1.0%, the strength and springiness can be further increased without impairing conductivity, thermal conductivity, and bending workability. Can be excellent.

  The copper alloy of the present invention has excellent strength and unprecedented bending workability without impairing the conductivity and thermal conductivity that are excellent as a conventional Cu—Ni—Si based copper alloy. Therefore, it can be provided as an appropriate material for various electric and electronic parts such as lead frames, terminals, connectors and the like that are compatible with rapidly developing IT and are particularly small and highly integrated.

Next, the reason why the numerical ranges such as the composition of the copper alloy, the size of the precipitates, and the aspect ratio are limited in the present invention will be described together with the operation thereof.
[Ni content]
Ni has the effect of ensuring the strength and heat resistance of the alloy and precipitates a compound with Si, which will be described later, thereby contributing to an increase in the strength of the alloy. However, if the content is less than 1.5%, the desired strength cannot be obtained. On the other hand, if the Ni content exceeds 4.0%, the workability during hot rolling deteriorates and the product is bent. A decrease in workability and electrical conductivity is significant. Furthermore, the area ratio of large particles of precipitates is increased, which is not preferable. Therefore, the Ni content of the alloy of the present invention is 1.5% to 4.0%, preferably 2.5 to 3.5%.
[Si content]
Si precipitates a compound with Ni to improve the strength and heat resistance of the alloy. If the Si content is less than 0.15%, precipitation of the compound is insufficient, so that the desired strength cannot be obtained. On the other hand, when the Si content exceeds 1.0%, the workability during hot rolling is lowered and the conductivity is significantly lowered. Furthermore, the area ratio of large particles of precipitates is increased, which is not preferable. Therefore, the Si content of the alloy of the present invention is 0.15% or more and 1.0% or less, preferably 0.4 to 0.9%.
[Ni / Si ratio]
If the Ni / Si content ratio Ni / Si is less than 3 or more than 7 even if the Ni and Si content is within the above range, it is less than 3 in order to deviate from the appropriate composition ratio of the Ni-Si based precipitate. In this case, when Si exceeds 7, the amount of Ni dissolved increases, which is not preferable because the decrease in conductivity becomes remarkable. Therefore, the Ni / Si ratio of the alloy of the present invention is 3 or more and 7 or less, preferably 4.0 to 5.5.

[O amount]
O easily reacts with Si in the alloy. When Si is present in the alloy in an oxide state, the precipitation of Ni and Si compounds is hindered, high strength cannot be obtained, and bending workability deteriorates. Therefore, the O content of the alloy of the present invention is 0.0050% or less, preferably 0.0030% or less.
[Zn, Mg, Sn, In amount]
The amounts of Zn, Mg, Sn, and In all have the effect of improving the strength mainly by solid solution strengthening without significantly reducing the conductivity of the alloy. Therefore, if necessary, one or more of these metals are added. If the total content is less than 0.01%, the effect of improving the strength by solid solution strengthening cannot be obtained, while the total amount is 1.0%. When the above is added, the electrical conductivity of an alloy and bending workability fall will become remarkable. Therefore, the amount of Zn, Mg, Sn and In added individually or in combination of two or more types is 0.01% or more and 1.0% or less, preferably 0.05% or more and 0.8% or less in total. is there. In the present invention, these elements are intentionally added elements. When the total amount is 0.01% or more, these elements are not regarded as inevitable impurities. That is, the present invention according to claim 2 is an alloy in which these elements are intentionally added to give a total amount of 0.01% or more and satisfy other requirements.

[Size and area ratio of Ni-Si based precipitates]
When the major axis of the Ni-Si-based precipitate is a (nm) and the minor axis is b (nm), a precipitate with a of less than 20 nm is subjected to rolling with a work strain η = 2 or more. It will re-dissolve inside and reduce the electrical conductivity. Here, the processing strain η is represented by η = ln (t ₀ / t), where t _{0 is} the thickness before rolling and t is the thickness after rolling. On the other hand, if a exceeds 200 nm, the dispersion interval of precipitates in the alloy becomes too large, so that an increase in strength cannot be obtained. Therefore, the size of the Ni—Si based precipitate in the alloy of the present invention is a: 20 nm or more and 200 nm or less. In addition, when the aspect ratio of the precipitate is expressed by a / b, when a / b exceeds 3, when the rolling process is performed with η = 2 or more, the precipitate is re-dissolved in the copper and the conductivity is increased. It will decrease. Therefore, the aspect ratio a / b of the precipitate is 1 or more and 3 or less. On the other hand, when the area ratio of precipitates in the alloy relating to precipitates within the above range is less than 80%, there are many precipitates in which a exceeds 200 nm. And, for example, there are many Ni-Si-based particles (crystallized products) of 1000 nm or more in which precipitates with a exceeding 200 nm and crystallized products generated during melt casting were not dissolved by hot rolling or solution treatment. When doing so, the desired strength cannot be obtained even by work hardening in rolling. Therefore, the area ratio of precipitates within the above range is 80% or more of all precipitates (all Ni—Si based precipitates).
The Cu—Ni—Si based copper alloy that satisfies the above requirements of the present invention is usually employed by those skilled in the art for ingot casting, hot rolling, solution treatment, intermediate cold rolling, aging treatment, final cold rolling, In strain relief annealing and the like, it can be produced by appropriately selecting the heating temperature, time, cooling rate, rolling degree, and the like. The alloy of the present invention has excellent conductivity and thermal conductivity, strength, springiness, and bending workability, and preferably has a tensile strength of 800 to 950 MPa, more preferably 800 to 1000 MPa, and a conductivity of preferably 35 to 35. The characteristic value of 55% IACS is shown.

Manufacture of samples Mainly made of electrolytic copper or oxygen-free copper, nickel (Ni), silicon (Si), zinc (Zn), copper magnesium master alloy (Cu-Mg), tin (Sn), indium (In) The raw material was melted in a high-frequency melting furnace in a vacuum or argon atmosphere, and cast into a 25 × 50 × 150 mm ingot. Next, the ingot was subjected to hot rolling and solution treatment, intermediate cold rolling, aging treatment, final cold rolling, and strain relief annealing in this order to obtain a flat plate having a thickness of 0.15 mm.
Various test pieces of the obtained plate material were collected and tested, and “strength”, “conductivity”, and “bending workability” were evaluated.
Method for Precipitating Precipitates of Target Size An example of a method for depositing precipitates of the target size is shown below.
(1) Major axis a of precipitate: 20 to 200 nm After heating the ingot to 750 to 950 ° C. for 0.5 to 12 hours to dissolve the Ni—Si-based crystallized material generated during casting, Roll. At the end of hot rolling, water cooling is performed from a material temperature of 700 to 900 ° C, preferably from 850 to 900 ° C. When a material temperature of 700 ° C. or higher cannot be obtained at the end of hot rolling, the solution is heated again to 700 to 950 ° C. for 0.5 hour or longer and then cooled with water to sufficiently perform solution treatment. Thereafter, cold rolling at a working strain η = 0 to 2.5 and aging treatment at 300 to 650 ° C. for 0.1 to 24 hours are performed.
(2) Major axis a of the precipitate: less than 20 nm Hot rolling is performed in the same manner as in (1) above, and after cold rolling with a working strain η = 0 to 2.5, 0.5 to 300 to 450 ° C. Perform aging treatment for 24 hours.
(3) When the major axis a of the precipitate exceeds 200 nm The ingot before hot rolling is heated in the same manner as in (1) above, and is not cooled actively after hot rolling, but allowed to cool (air cooling). . After cold rolling with a working strain η = 0 to 2.5, an aging treatment is performed at 550 to 700 ° C. for 0.1 to 24 hours.
Evaluation of Precipitates Using a scanning electron microscope and a transmission electron microscope, the alloy strip before the final cold rolling was cut parallel to the rolling direction at right angles to the thickness, and the precipitates in the cross section were observed with 10 fields of view and photographed. The major axis a, the minor axis b, and the area of each of the precipitates having a major axis a of 5 nm or more were measured using an image analysis apparatus (trade name Luzex, manufactured by Nireco Corporation). FIG. 1 and FIG. 2 show the frequency distribution of the major axis and minor axis measurement values of the precipitate of Example 1. In the present invention, the total area of the precipitates refers to the sum of the areas of the precipitates having a major axis a of 5 μm or more. The major axis a is 20 nm to 200 nm, the aspect ratio a / The ratio of the total area of the precipitates in which b is 1 to 3 was calculated as the area ratio C (%). Also, the average aspect ratio a determined by the average major axis a _ta as the average value of the major axis of all the measured precipitates, the average major axis a _ta and the average minor axis b _ta of the average minor axis of all the measured precipitates. _ta / b _ta is described in Tables 1-2 and 2-2 for reference. This is because the size of the precipitate cannot be known only by describing the area ratio C (%).
In addition, by the final cold rolling (usually processing strain η = 2 or more), a Ni—Si-based precipitate having a major axis of 20 nm or less or a precipitate having a major axis exceeding 20 nm but having an aspect ratio exceeding 3 is dissolved. However, it was confirmed that a precipitate having an aspect ratio of 1 to 3 at 20 nm or more maintained its major axis, minor axis and aspect ratio even after the final cold rolling. Also, the area ratio C of the precipitates hardly changes even after the final cold rolling because the precipitates exceeding 200 nm are not dissolved.
About physical property evaluation "strength" of a test piece, it carried out using the No. 13 B test piece according to the tensile test prescribed | regulated to JISZ2241, and measured the tensile strength.
“Conductivity” is a four-terminal method for measuring the electrical resistance of a test piece, and the ratio of electrical conductivity to standard annealed copper (with a volume resistivity of 1.7241 μΩcm) is expressed as a percentage and expressed in% IACS. .
Regarding “bending workability”, the surface of a bending part obtained by bending a test piece having a width of 10 mm with a W bending tester using a die having a bending radius of 0.15 mm and a load of 50 kN was observed with an optical microscope (100 times). The presence / absence of cracks was investigated and evaluated. The case where no cracks occurred was indicated by ○ and the case where cracks occurred was indicated by ×.

The Example of the high intensity | strength highly conductive copper alloy which concerns on this invention is described with a comparative example about the copper alloy of the component composition shown to Table 1-1 and Table 2-1. Alloy Examples 1 to 7 of the present invention included fine precipitates having an aspect ratio of 1 to 1.6 of about 30 nm to 100 nm, and had excellent strength, conductivity, and bending workability. On the other hand, when the results of Comparative Examples 8 to 17 are examined, Comparative Examples 8 to 11 are alloys having compositions outside the range of the alloy composition of the present invention. In Comparative Example 8, since the amount of Ni added is less than 1.5%, the amount of Ni—Si-based precipitates is reduced, so that sufficient strength cannot be obtained. In Comparative Example 9, since the addition amount of Si exceeds 1.0%, the solid solution amount of Si increases, resulting in a decrease in electrical conductivity and poor bending workability. In Comparative Example 10, since the Ni / Si ratio deviates from the appropriate composition ratio of the precipitate, the amount of Ni dissolved increases, resulting in a decrease in conductivity. Therefore, sufficient strength cannot be obtained. In Comparative Example 11, the addition amount of Zn, Mg, and Sn as subcomponents generally exceeds 1.0%, so that the strength is sufficient, but the conductivity decreases due to their solid solution, and bending workability is also increased. Is inferior. Since Zn, Mg and Sn in Comparative Example 11 are not inevitable impurities, they do not fall under the invention example according to claim 1 and contain more than 1.0% of Zn, Mg and Sn. It does not correspond to the invention example concerning.

About Comparative Examples 12-17, it is an alloy remove | deviated from the precipitation state of the alloy of this invention. In Comparative Example 12, since the size of the precipitate was less than 20 nm, the precipitate was dissolved during processing, and the electrical conductivity was lowered. In Comparative Example 13, since the aspect ratio of the precipitate exceeded 3, the solid solution was dissolved during processing, and the bending workability was inferior. In Comparative Example 14, since the size of the precipitate exceeds 200 nm, the dispersion interval of the precipitate becomes large, and a desired strength cannot be obtained. In Comparative Example 15, in addition to precipitates having a size of 20 nm to 200 nm, many coarse precipitates were observed, and as a result, the strengthening by the precipitates as a whole decreased. 3 and 4 show the frequency distribution of measured values of the major axis and the minor axis of the precipitate of Comparative Example 16. FIG. In Comparative Example 16, the aspect ratio exceeds 3, and there are coarse precipitates as shown in FIGS. 3 and 4, so the area ratio C is as small as 60%. Has fallen. In Comparative Example 17, as in Comparative Example 12, since the size of the precipitate was less than 20 nm, the solid solution was dissolved during processing, and the electrical conductivity was lowered.

表中「−」は「添加せず」を表す。

In the table, “-” represents “not added”.

4 is a graph showing a frequency distribution of measured long diameters of precipitates of Example 1. 2 is a graph showing a frequency distribution of measured minor axis values of precipitates of Example 1. FIG. It is a graph which shows the frequency distribution of the major axis measured value of the precipitate of the comparative example 16. It is a graph which shows the frequency distribution of the short axis measured value of the precipitate of the comparative example 16.

Claims (2)

In mass proportion
Ni: 1.5% to 4.0%,
Si: 0.15% or more and 1.0% or less,
Ni / Si content ratio Ni / Si: 3 or more and 7 or less,
O: In a copper alloy of 0.0050% or less and the balance being Cu and inevitable impurities,
When the major axis is “a” and the minor axis is “b”, the copper alloy contains Ni—Si-based precipitates in which “a” is 20 nm to 200 nm and the aspect ratio a / b is 1 to 3 before the final cold rolling. accounting for 80% or more by area ratio of all the precipitates,
Tensile strength: 800～950MPa and conductivity: 35 to 55% IACS der Rukoto characterized, excellent electrical conductivity, bending workability electronic parts for high strength and high conductivity copper alloy having both. In mass proportion
Ni: 1.5% to 4.0%,
Si: 0.15% or more and 1.0% or less,
Ni / Si content ratio Ni / Si: 3 or more and 7 or less,
O: 0.0050% or less,
In a copper alloy containing 0.01% or more and 1.0% or less in total of one or more of Zn, Mg, Sn and In, with the balance being Cu and inevitable impurities,
When the major axis is “a” and the minor axis is “b”, the copper alloy contains Ni—Si-based precipitates in which “a” is 20 nm to 200 nm and the aspect ratio a / b is 1 to 3 before the final cold rolling. Occupy 80% or more in the area ratio of all precipitates
Tensile strength: 800～1000MPa and conductivity: 35 to 55% you being a IACS electronic components for high-strength and high conductivity copper alloy.

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