CN100433198C - A high-strength and high-conductivity copper-rare earth alloy material and its preparation process - Google Patents

Abstract

The invention discloses a high-strength and high-conductivity copper-rare earth alloy material and its preparation process. The mass ratio of the components of the alloy is: copper: chromium: neodymium is 97.6-98.8: 0.4-1.1: 0.02-0.08. The preparation process of the invention includes alloy melting and casting process, alloy casting process and alloy casting process. In the alloy casting process, alloy casting ingots are directly cold-rolled and then subjected to aging treatment. The preparation process of the present invention directly adds pure metal Cr particles when the alloy is melted and casted, and the casting temperature is 1100°C-1250°C. The alloy material of the invention has the following characteristics: the tensile strength is 470-510MPa, the elongation is 12-15%, the electrical conductivity is 88-91% IACS, and the softening temperature is 510-540°C. The melting and casting technology of the alloy of the invention not only simplifies the process and reduces segregation, but also facilitates the precise control of the alloy composition. The alloy of the invention has a simple preparation process and excellent performance, and can be widely used in the electronic industry and machinery industry where high conductivity, high strength and high working temperature are required, and is especially suitable for the microelectronic industry that requires high strength, high conductivity and good processing performance.

Description

A high-strength and high-conductivity copper-rare earth alloy material and its preparation process

Technical field:

The invention belongs to the field of metal electronic materials, and relates to a high-strength and high-conductivity copper-rare earth alloy material and a preparation process thereof, in particular to a high-strength and high-conductivity copper-chromium-neodymium alloy and a preparation process thereof.

Background technique:

The research and development of high-strength and high-conductivity copper-based conductive materials has always been one of the hot spots in the research of copper alloys. Many fields of application require the materials used to have both high conductivity and high strength. According to different structural and performance characteristics, high-strength and high-conductivity copper-based materials can be divided into two categories: high-strength and high-conductivity copper alloys and high-strength and high-conductivity copper-based composite materials. The two types of materials are different in terms of strengthening mechanism, preparation process, performance characteristics and even application fields. In recent years, the performance of high-strength and high-conductivity copper-based materials has been greatly improved by comprehensively utilizing various strengthening methods.

Solid solution strengthening, deformation strengthening, grain boundary strengthening, precipitation strengthening, and composite strengthening are the five main strengthening methods in the design of high-strength and high-conductivity copper-based materials, and their essence is to strengthen the material by preventing the movement of dislocations. The first four strengthening methods are usually applied to the strengthening of copper alloys, and composite strengthening is mainly used for the strengthening of copper-based composite materials. At present, high-performance high-strength and high-conductivity copper-based materials often make comprehensive use of various strengthening mechanisms to maximize performance and reduce costs. Since alloying elements exist in a solid solution state, the electrical conductivity of the copper matrix will be seriously affected. When designing high-strength and high-conductivity copper alloys, the general principle is to require that the selected alloying elements have a very low solid solubility in the copper matrix at room temperature ( Cr, Zr, Fe, Ag, Be, etc.), or compound precipitation can be formed between alloying elements (Fe ₂ P, Cu ₃ Zr, Mg _m P _n , Ni ₂ Si, etc.). In addition, some auxiliary elements that are beneficial to the properties of the alloy can be added, such as P (deoxidation, prevent hydrogen embrittlement), Zn (prevent brittle phase Cu ₃ Sn, Cu ₅ Sn ₆ between the metal substrate and the coating) and Mg (improve the material resistance stress relaxation properties), etc.

For high-strength and high-conductivity deformable copper-based materials, it is not only required that the alloying elements and copper have very low mutual solubility at room temperature, but also the second phase components must have good plasticity to prevent the interface between the reinforced phase and the matrix during large deformations. cracking. According to the analysis of binary phase diagrams of a large number of copper alloys, only Cu-Ag and Cu-bcc (Nb, Ta, Fe, V, Cr, Mo) systems meet the above requirements.

The typical preparation process of precipitation-strengthened copper alloy is: melting and casting-homogenization treatment-hot rolling-solution treatment-cold rolling-aging. For the smelting and casting of high-conductivity and high-strength copper alloys, the main focus is on the optimization of smelting and pouring processes to obtain master alloy ingots with less casting defects, uniform composition, and low impurity content, and to reduce smelting costs as much as possible. After the master alloy ingot is prepared by the casting method, it is homogenized to eliminate the composition segregation caused in the casting process; then the ingot is pre-deformed and hot-rolled, and the coarseness formed in the casting and homogenization process is eliminated through dynamic recrystallization , Uneven organization. The hot-rolled samples were subjected to solution treatment at a certain temperature, and then subjected to aging treatment after a certain degree of cold deformation treatment. Cold deformation can introduce a large number of point and line defects in the alloy matrix. These defects can serve as the nucleation core of the precipitated phase and the diffusion channel of atoms during the aging process, accelerating the precipitation process and refining the precipitated phase particles. For precipitation-strengthened high-strength and high-conductivity copper alloys, the properties of the alloy depend on the type of precipitated phase, the type, quantity, shape, size, distribution, and deformation of the alloy. Large pre-deformation and short-term aging can obtain the highest hardness and high conductivity. Due to the unique properties of rare earth elements, they are often added as microalloying elements to metal materials for modification. The addition of a small amount of rare earth elements can change the microstructure, impurity content, interface conditions, etc. of the alloy, and ultimately affect the performance of the alloy. This effect can be either beneficial or detrimental, depending on the type of alloy system and various process conditions. Previous studies on the effect of rare earths on metal materials mainly focus on the following aspects: purification, modification, microalloying of rare earths and their effects on material conductivity, processing and mechanical properties, wear resistance, and oxidation resistance. impact etc. At present, rare earths have been widely used in steel and aluminum, and a large amount of experimental data has been mastered, and their effects and mechanisms have been studied in depth. The application of rare earths in copper alloys cannot be compared with the former two in theory or practice.

Integrated circuit lead frame materials are an important application field of high-strength and high-conductivity copper alloys. At present, they account for more than 80% of the lead frame material consumption. More than 100 types of copper alloy series for high, medium and low-grade lead frames have been developed, Table 1 The main properties of some copper alloy lead frame materials are listed. my country lags behind advanced countries in the research and production of lead frame copper alloy materials, with few varieties and low output, especially high-grade lead frame materials basically rely on imports. Although there are already some lead frame material production and processing enterprises, they basically rely on imitation and technology introduction, and there are few products with independent intellectual property rights. Some scientific research institutes and colleges and universities have carried out research and development of such materials, such as Tsinghua University, Luoyang Institute of Technology, Nanchang University, etc., but they are basically in the laboratory stage and cannot meet the needs of the rapid development of my country's microelectronics industry. Therefore, it is of great significance to develop new copper-based lead frame materials with high strength, high conductivity and high softening temperature as soon as possible.

Table 1 Commonly used lead frame alloys and their properties

Invention content:

The purpose of the present invention is to provide a new high-strength and high-conductivity copper alloy material, which still maintains a conductivity as high as 88-91% IACS and an elongation of 12-15% under a sufficiently high strength, which can be used as a copper alloy that requires good processing. High-performance lead frame materials can also be applied to microelectronics and electric power industries that require high strength and high conductivity.

In order to achieve the above object, the copper-rare earth alloy technical scheme provided by the invention is as follows:

The mass ratio of the components of the alloy of the invention is: copper: chromium: neodymium 97.6-98.8: 0.4-1.1: 0.02-0.08.

The preparation process of the high-strength and high-conductivity copper-rare earth alloy material of the present invention includes an alloy melting and casting process and a treatment process after alloy melting and casting. In the treatment process after alloy melting and casting, the alloy ingot is directly cold-rolled and then subjected to aging treatment.

The preparation process of the present invention directly adds pure metal Cr particles when the alloy is melted and casted, and the casting temperature is 1100°C-1250°C.

When melting and casting the alloy in the preparation process of the present invention, a Cu-Nd master alloy is used, and the Nd content in the master alloy is 7-18wt%, and Cu-Cr alloy in molten state is added.

In the preparation process of the present invention, after cold rolling, the aging treatment temperature is 380°C-600°C.

The purity of metal Cr particles added in the preparation process of the invention is 99.7-99.9 wt%, and the particle size is 0.5-3.0mm.

The vacuum degree in the furnace is maintained at 2×10 ^-1 Pa to 1×10 ^-2 Pa during the melting and casting of the preparation process of the present invention.

The specific description of the alloy technical scheme of the present invention is as follows:

1. Alloy melting and casting process

a). Cu-Nd (Nd: 7-18wt%) master alloy casting

Copper is first melted in a vacuum intermediate frequency induction furnace, and then the rare earth metal Nd fragments are added in proportion, and cast into bars at 1100°C to 1300°C for later use.

b).Cu-Cr-Nd alloy casting

Melt copper in a vacuum intermediate frequency induction furnace first, then directly add Cr particles, and then add Cu-Nd master alloy after melting. 2×10 ^-1 Pa-1×10 ^-2 Pa.

2. Treatment process after alloy casting

After the cast alloy ingot is peeled on the surface, it is directly cold-rolled without solution treatment, and then subjected to aging treatment at 380°C-600°C for a holding time of 30min-60min, and then taken out after cooling in the furnace.

The alloy material of the invention has the following characteristics: the tensile strength is 470-510 MPa, the elongation is 12-15%, the electrical conductivity is 88-91% IACS, and the softening temperature is 510-540 DEG C. The melting and casting technology of the alloy of the invention not only simplifies the process and reduces segregation, but also facilitates the precise control of the alloy composition. The treatment and processing technology after the alloy casting further shortens the production cycle and saves the cost. The alloy of the invention has a simple preparation process and excellent performance, and can be widely used in the electronic industry and machinery industry where high conductivity, high strength and high working temperature are required, and is especially suitable for the microelectronic industry that requires high strength, high conductivity and good processing performance.

Description of drawings

Figure 1: The longitudinal distribution of Cr elements along the Cu-Cr-Nd ingot

Figure 2: Effect of different process flow on alloy hardness

Figure 3: The effect of different process flow on the electrical conductivity of the alloy

Detailed ways

The present invention will be described in detail below in conjunction with the examples.

Example 1:

The raw materials are electrolytic copper with a purity of 99.9%, electrolytic chromium with a purity of 99.9%, and rare earth metal neodymium with a purity of 99.5%. The Cu-Nd (Nd: 8wt%) master alloy is first smelted by first melting copper in a vacuum intermediate frequency induction furnace, then adding proportioned rare earth metal Nd fragments, and casting them into bars at 1150°C for later use. Then carry out Cu-Cr-Nd alloy smelting according to the mass ratio of Cu:Cr:Nd as 98.20:0.70:0.03, first melt copper in a vacuum intermediate frequency induction furnace, and then directly add crushed pure Cr particles, the particle size is 0.5-1.0 mm, add Cu-Nd master alloy after melting, heat preservation temperature is 1300°C, casting temperature is 1180°C, keep the vacuum degree in the furnace at 1.5×10 ^-2 Pa, and cast the cast rod. Cut off the head and tail of the cast rod, polish the surface smooth, and directly cold-roll, the cumulative reduction is about 95%. Carry out aging treatment under vacuum, the aging temperature is 430 ℃, the holding time is 35min, take out after cooling with the furnace. The electrical conductivity of the 98.20Cu-0.70Cr-0.05Nd alloy obtained by the above process reaches 90% IACS, the tensile strength reaches 510MPa, and the softening temperature reaches 540°C.

Example 2:

The raw materials are electrolytic copper with a purity of 99.9%, electrolytic chromium with a purity of 99.9%, and rare earth metal neodymium with a purity of 99.5%. The Cu-Nd (Nd: 9wt%) master alloy is first smelted by first melting copper in a vacuum intermediate frequency induction furnace, then adding proportioned rare earth metal Nd fragments, and casting them into bars at 1100°C for later use. Then carry out Cu-Cr-Nd alloy smelting according to the mass ratio of Cu:Cr:Nd as 98.20:0.90:0.04, melt copper first in the vacuum intermediate frequency induction furnace, and then directly add the crushed pure Cr particles, the particle size is 1.8- 2.5 mm, add Cu-Nd master alloy after melting, hold temperature at 1250°C, casting temperature at 1100°C, keep the vacuum degree in the furnace at 1×10 ^-2 Pa, and cast into cast rods. Cut off the head and tail of the cast rod, polish the surface smooth, and directly cold-roll, the cumulative reduction is about 95%. Carry out aging treatment under vacuum, the aging temperature is 500°C, the holding time is 30min, and it is taken out after cooling with the furnace. The electrical conductivity of the 98.20Cu-0.90Cr-0.04Nd alloy obtained by the above process reaches 91% IACS, the tensile strength reaches 500MPa, and the softening temperature reaches 530°C.

Example 3:

The raw materials are electrolytic copper with a purity of 99.9%, electrolytic chromium with a purity of 99.9%, and rare earth metal neodymium with a purity of 99.5%. The Cu-Nd (Nd: 12wt%) master alloy is first smelted by first melting copper in a vacuum intermediate frequency induction furnace, then adding proportioned rare earth metal Nd fragments, and casting them into bars at 1200°C for later use. Then the Cu-Cr-Nd alloy is smelted according to the mass ratio of Cu:Cr:Nd as 98.2:0.9:0.06. Copper is first melted in a vacuum intermediate frequency induction furnace, and then the crushed pure Cr particles are directly added, and the particle size is 2.. 0-3.0mm, add Cu-Nd master alloy after melting, heat preservation temperature is 1200°C, casting temperature is 1100°C, keep the vacuum degree in the furnace at 2×10 ^-2 Pa, and cast into cast rods. Cut off the head and tail of the cast rod, polish the surface smooth, and directly cold-roll, the cumulative reduction is about 95%. Carry out aging treatment under vacuum, the aging temperature is 380 ℃, the holding time is 40min, take out after cooling with the furnace. The electrical conductivity of the 98.2Cu-0.9Cr-0.06Nd alloy obtained by the above process reaches 88% IACS, the tensile strength reaches 490MPa, and the softening temperature reaches 520°C.

The technical principles of the present invention relate to:

a). Melting and casting of low-chromium copper-chromium alloy (containing 0.4-1.2wt% chromium): According to the copper-chromium binary phase diagram, the eutectic composition of copper-chromium alloy is about 1.28wt%. When the hypereutectic alloy enters the liquid-solid two-phase region from the liquid phase region during the cooling process, the primary Cr is first precipitated. Since the specific gravity of Cr is smaller than that of Cu, it is easy to float up and cause specific gravity segregation. The higher the chromium content, the more serious the segregation, and the prepared intermediate alloy The composition is not uniform, resulting in the inability to accurately control the composition of the alloy in the future. However, the alloy composition of the present invention contains less than 1.28wt% chromium, is a hypoeutectic alloy, and its temperature interval and composition interval are much smaller than that of a hypereutectic alloy, so the fluidity during solidification is better, and the segregation after solidification will also be smaller . For this reason, the present invention adopts the smelting technology of directly adding pure chromium, and after melting and casting, a Cu-Cr-Nd alloy casting having a composition close to the nominal value and without macro-segregation can be obtained. Figure 1 is the distribution of Cr elements along the longitudinal direction of the ingot obtained by the composition analysis of the glow discharge spectrometer, which shows that the ingot cast by this process has almost no macro segregation.

b). Cold deformation and aging treatment: cold deformation can introduce a large number of point and line defects in the alloy matrix. On the one hand, these defects can improve the strength of the alloy, and on the other hand, they can serve as nucleation centers and atoms of the precipitated phase during the aging process. The diffusion channel accelerates the precipitation process and refines the precipitated phase particles. Non-ferrous metal materials usually undergo homogenization treatment after melting and casting, and usually undergo solution treatment before cold deformation, so as to achieve solid solution strengthening and improve the precipitation strengthening effect during aging treatment after cold deformation. Since the alloy of the present invention can obtain a non-segregation alloy during casting, there is no need for homogenization treatment; and considering that the alloy of the present invention is not balanced and solidified during casting, the alloying elements have been effectively dissolved into the matrix, so the solid solution treatment process can also be omitted , direct cold deformation and aging treatment. It can be seen from Figure 2 that the hardness of the alloy after 95% cold rolling does not decrease significantly during the aging process like other alloys, indicating that its recovery and recrystallization speed is lower than that of the solid solution + cold rolling + aging alloy, which may be due to the alloy in The cooling rate during casting into ingot is lower than the quenching cooling rate during solution treatment. This relatively low cooling rate leaves less supersaturated vacancies in the matrix, and the presence of these vacancies will promote recovery and recrystallization. carried out. On the other hand, recovery and recrystallization reduce the point defect density, which increases the electrical conductivity of the alloy, and the effect is more obvious than that of the alloy treated by solid solution + cold rolling + aging (see Figure 3).

Claims (6)

1, a kind of preparation technology of high strength high conducting copper-rare-earth alloy material, comprise the founding of alloy, the treatment process behind the alloy casting, it is characterized in that: in the founding of described alloy by copper: chromium: neodymium is that the mass ratio of 97.6-98.8: 0.4-1.1: 0.02-0.08 carries out alloy casting; Directly cold rolling in the treatment process behind the alloy casting to alloy cast ingot, carry out Ageing Treatment again.

2, a kind of preparation technology by the described high strength high conducting copper-rare-earth alloy material of claim 1, it is characterized in that: during alloy casting, directly add simple metal Cr particle, cast temperature is 1100 ℃-1250 ℃.

3, by the preparation technology of claim 1 or 2 described high strength high conducting copper-rare-earth alloy materials, it is characterized in that: during alloy casting, adopt the Cu-Nd intermediate alloy, the Nd content in the intermediate alloy is 7wt%-18wt%, and adds the Cu-Cr alloy of molten state.

4, by the preparation technology of claim 1 or 2 described high strength high conducting copper-rare-earth alloy materials, it is characterized in that: after cold rolling, the temperature of carrying out Ageing Treatment is 380 ℃-600 ℃.

5, by the preparation technology of the described high strength high conducting copper-rare-earth alloy material of claim 2, it is characterized in that: the Metal Cr particle purity of interpolation is 99.7wt%-99.9wt%, and granular size is 0.5mm-3.0mm.

6, by the preparation technology of claim 1 or 2 described high strength high conducting copper-rare-earth alloy materials, it is characterized in that: keeping the interior vacuum degree of stove during founding is 2 * 10 ^-1Pa-1 * 10 ^-2Pa.

Images