Copper alloy strip for multi-component synergistically reinforced lead frame and preparation method thereof

Abstract

The present invention provides a copper alloy strip for a multi-component synergistically reinforced lead frame and a preparation method thereof, and relates to the field of alloy technology. The copper alloy strip for a multi-component synergistically reinforced lead frame of the present invention comprises the following components in mass percentage: Ni: 0.9% to 3.0%; Si: 0.3% to 1.3%; Mg: 0.06% to 0.18%; Co: 0.5% to 1.5%; Ti: 0.02% to 0.1%; Y: 0.05% to 0.15%, with the remainder being copper and unavoidable impurities. The copper alloy strip prepared by the present invention has excellent mechanical properties and electrical conductivity, wherein the tensile strength σ b ≥850Mpa, electrical conductivity ≥48%IACS, yield strength σ 0.2 The preparation process of the present invention is simple, the operation difficulty is low, and it has broad market application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy materials, and in particular to a copper alloy strip for a multi-component synergistically reinforced lead frame and a preparation method thereof. Background Art

[0002] As a crucial component of integrated circuits, lead frames play a key role in supporting chips, connecting circuits, and distributing power. With the rapid development of integrated circuits toward large and ultra-large scale, the integration and density of circuits are increasing, placing higher demands on the precision, surface quality, and shape of lead frame materials. Furthermore, lead frame materials must possess excellent thermal and electrical conductivity, as well as high strength, elasticity, and resistance to bending.

[0003] International companies started early in the development of leadframe materials, experienced rapid growth, and boast highly mature technologies. Companies like Mitsubishi Shindoh, Furukawa Electric, Nippon Mining, Sumitsu Seiko, Diehl, Olin USA, and Wieland Germany all have their own Cu-Ni-Si alloy grades. They utilize semi-continuous casting, hot rolling, and solution aging treatment to industrialize the alloys. They have established numerous highly automated production lines, resulting in stable product performance and high added value, making them the world's leading suppliers of high-end leadframe sheet and strip. In 2019, domestic copper sheet and strip production reached nearly 2.87 million tons, of which less than 100,000 tons were for leadframes. This production primarily consisted of low-end leadframe materials such as KFC and C19400 alloys, with a smaller amount of Cu-Ni-Si. Domestic demand for leadframe materials approached 150,000 tons, with the majority of mid- to high-end leadframe materials relying on imports. Currently, only a few companies in China, such as Ningbo Xingye, China Aluminum Luoyang Copper, and Ningbo Bowei, have achieved industrialization of Cu-Ni-Si series alloys using semi-continuous casting methods, with an annual output of less than 5,000 tons. The alloys that have been industrialized in China are Cu-3.2%Ni-0.6%Si-0.06%Mg (C70250) and Cu-1.5Ni-0.25Si-0.03P (C19010). Among them, C70250 is currently only industrialized by a few companies in China. This is mainly due to the high content of nickel and silicon elements, which requires a high set of heat treatment technology. If the control is not reasonable, it is difficult to effectively achieve the complete precipitation of the second phase particles, resulting in low overall performance of the material.

[0004] At present, the main prominent problem in the industrial production of Cu-Ni-Si alloys in China is the failure to fully master the key production technologies such as the control technology of the composition uniformity of large-scale ingots of Cu-Ni-Si alloys, continuous high-temperature online solid solution and a complete set of heat treatment technologies. This has led to poor surface quality of alloy products (more than 10 small pits with a depth of 5μm within 1m), high surface roughness (0.10~0.15μm), unstable plate shape accuracy and other problems. The quality grade is low and can only be used for medium and low-end lead frame materials. Summary of the Invention

[0005] Based on this, the present invention provides a copper alloy strip for multi-component synergistically strengthening lead frame and a preparation method thereof. The tensile strength of the copper alloy strip of the present invention is σ b ≥850Mpa, electrical conductivity ≥48%IACS, yield strength σ 0.2 ≥750MPa, the strip has uniform chemical composition, excellent mechanical properties and electrical conductivity, and its preparation process is simple.

[0006] The multi-component synergistically reinforced copper alloy strip for lead frame of the present invention comprises the following components in percentage by mass:

[0007] Ni: 0.9% to 3.0%; Si: 0.3% to 1.3%; Mg: 0.06% to 0.18%; Co: 0.5% to 1.5%; Ti: 0.02% to 0.1%; Y: 0.05% to 0.15%, and the remainder is copper and unavoidable impurities.

[0008] The method for preparing the multi-component synergistically reinforced copper alloy strip for lead frame of the present invention comprises the following steps:

[0009] (1) Ingredients: Weigh titanium powder, magnesium powder, Cu-Y alloy, silicon powder, cobalt powder, nickel powder, and copper powder;

[0010] (2) Melting: The weighed titanium powder, magnesium powder and Cu-Y alloy are sealed in a pure copper tube and fixed on the robot arm of a vacuum induction furnace, and copper powder, nickel powder, silicon powder and cobalt powder are added to the crucible of the vacuum induction furnace; after the vacuum induction furnace is evacuated, a protective atmosphere is introduced to 0.05 MPa, and then the crucible is heated until all the solids in the crucible are melted and the temperature is raised to 1500°C. The induction current is turned off, and the robot arm is quickly operated to immerse the pure copper tube containing the titanium powder, magnesium powder and Cu-Y alloy under the melt liquid surface, the robot arm is lifted and the induction current is turned on to continue to keep warm for 2 minutes to 5 minutes, and then casting is carried out after keeping warm. After the casting is completed, it is cooled to obtain an ingot;

[0011] (3) Solid solution: The ingot obtained in step (2) is subjected to surface milling treatment, and then placed in a muffle furnace and heated to 800°C to 900°C and kept warm for 3h to 5h. After the insulation is completed, the ingot is taken out and water-cooled;

[0012] (4) Hot rolling: The solution-solution ingot is kept at 700°C to 800°C for 15 to 40 minutes, taken out and sent to a hot rolling mill for rolling with a reduction of 15% to 35% per pass, and the final rolling amount is 50%;

[0013] (5) Cold rolling: the sample after rolling in step (4) is sent to a cold rolling mill and rolled at a rate of 8% to 12% per pass to a plate thickness of 1.5 mm to 2.5 mm. The plate is then annealed at 400°C to 450°C for 3h to 5h, and then rolled at a rate of 8% to 12% per pass to a plate thickness of 0.3 mm to 0.5 mm. The plate is then annealed at 300°C to 350°C for 3h to 5h, and finally rolled at a rate of 8% to 12% per pass to a plate thickness of 0.15 mm to 0.25 mm.

[0014] Preferably, the Y content in the Cu-Y alloy is 15 wt.% to 25 wt.%.

[0015] Preferably, the protective atmosphere in step (2) is argon or nitrogen.

[0016] Preferably, the heating rate in step (3) is 3°C to 6°C / min.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The copper alloy strip prepared by the present invention has excellent mechanical properties and electrical conductivity, wherein the tensile strength σ b ≥850Mpa, electrical conductivity ≥48%IACS, yield strength σ 0.2 ≥750MPa.

[0019] (2) The preparation process of the present invention is simple and has low operation difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the metallographic image of the sample after solid solution in comparative example 1;

[0021] Figure 2 This is the metallographic image of the sample in the final state of Comparative Example 1;

[0022] Figure 3 This is the metallographic image of the sample after solutionization in Example 1;

[0023] Figure 4 This is the metallographic image of the sample in the final state of Example 1. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions and advantages of the present invention more clear, the preferred embodiments of the present invention are further described in detail below with reference to the examples. Based on the examples in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] 0.5g titanium powder, 1.5g magnesium powder, and 5g Cu-Y alloy (wherein the Y content is 20wt.%) are sealed in a pure copper tube and fixed on the robotic arm of a vacuum induction furnace. 938.5g copper powder, 18g nickel powder, 6.5g silicon powder, and 10g cobalt powder are added to the crucible of the vacuum induction furnace. The vacuum induction furnace was evacuated to below 15Pa, and a protective atmosphere of argon was introduced to 0.05MPa. Then, an induction power supply was introduced to start heating. When all the solids in the crucible were melted and the temperature rose to about 1500°C, the induction current was turned off. The robotic arm was quickly operated to immerse the pure copper tube containing titanium powder, magnesium powder, and Cu-Y alloy under the melt surface. The robotic arm was lifted, the induction current was turned on, and the heat was continued for 3 minutes. After the heat was kept warm, casting was carried out. After the casting was completed, it was cooled for about 30 minutes and then taken out. The ingot was milled and placed in a muffle furnace. The temperature was increased to 850°C at a heating rate of 5°C / min and kept warm for 4 hours. After the heat was finished, the ingot was taken out and water-cooled. The solutionized ingot is placed in a muffle furnace at 800°C for 30 minutes, then taken out and sent to a hot rolling mill for a rolling process with a reduction of 30% per pass, and the final rolling amount is 50%. It is then sent to a cold rolling mill and rolled at a speed of 10% per pass to a plate thickness of about 2mm. The plate is then annealed at 430°C for 4 hours, and then rolled at a speed of 10% per pass to a plate thickness of 0.45mm. The plate is then annealed at 330°C for 3 hours, and finally rolled at a speed of 10% per pass to a plate thickness of 0.2mm (any edge cracks that may occur are promptly removed during the cold rolling process), thus obtaining a multi-component synergistically strengthened copper alloy strip for lead frames.

[0027] The performance test of the prepared copper alloy strip was carried out, wherein the mass percentage of each element in the copper alloy strip is as follows:

[0028] Ni: 1.801%; Si: 6.475%; Mg: 1.426%; Co: 0.989%; Ti: 0.484%; Y: 0.089%, and the balance is copper and inevitable impurities.

[0029] The hardness of the copper alloy strip prepared in Example 1 is HV=269.2, and the tensile strength σ b =854.5Mpa, electrical conductivity = 54% IACS, yield strength σ 0.2 =744MPa.

[0030] Example 2

[0031] 0.4g titanium powder, 1.0g magnesium powder, and 7.5g Cu-Y alloy (wherein the Y content is 20wt.%) were sealed in a pure copper tube and fixed on the robotic arm of a vacuum induction furnace. 934.6g copper powder, 14g nickel powder, 6.5g silicon powder, and 16g cobalt powder were added to the crucible of the vacuum induction furnace. The vacuum induction furnace was evacuated to below 15Pa, and a protective atmosphere of argon was introduced to 0.05MPa. Then, an induction power supply was introduced to start heating. When all the solids in the crucible were melted and the temperature rose to about 1500°C, the induction current was turned off. The robotic arm was quickly operated to immerse the pure copper tube containing titanium powder, magnesium powder, and Cu-Y alloy under the melt surface. The robotic arm was lifted, the induction current was turned on, and the heat was continued for 3 minutes. After the heat was kept warm, casting was carried out. After the casting was completed, it was cooled for about 30 minutes and then taken out. The ingot was milled and placed in a muffle furnace. The temperature was increased to 800°C at a heating rate of 5°C / min and kept warm for 5 hours. After the heat was finished, the ingot was taken out and water-cooled. The solutionized ingot is placed in a muffle furnace at 700°C for 40 minutes, taken out and sent to a hot rolling mill for a rolling process with a reduction of 20% per pass, and the final rolling amount is 50%. It is then sent to a cold rolling mill and rolled at a speed of 10% per pass to a plate thickness of about 2mm. The plate is then annealed at 400°C for 5 hours, and then rolled at a speed of 10% per pass to a plate thickness of 0.45mm. The plate is then annealed at 350°C for 4 hours, and finally rolled at a speed of 10% per pass to a plate thickness of 0.2mm (any edge cracks that may occur are promptly removed during the cold rolling process), thus obtaining a multi-component synergistically strengthened copper alloy strip for lead frames.

[0032] The performance test of the prepared copper alloy strip was carried out, wherein the mass percentage of each element in the copper alloy strip is as follows:

[0033] Ni: 1.397%; Si: 0.6491%; Mg: 0.934%; Co: 1.579%; Ti: 0.038%; Y: 0.142%, and the remainder is copper and inevitable impurities.

[0034] The hardness of the copper alloy strip prepared in Example 2 is HV=261.5, and the tensile strength σ b =853.2Mpa, electrical conductivity = 55.4%IACS, yield strength σ 0.2 =752.7MPa.

[0035] Example 3

[0036] 0.6g titanium powder, 1.2g magnesium powder, and 5g Cu-Y alloy (with a Y content of 20wt.%) were sealed in a pure copper tube and fixed on a vacuum induction furnace robotic arm. 943.2g copper powder, 19g nickel powder, 6g silicon powder, and 5g cobalt powder were added to the crucible of the vacuum induction furnace. The vacuum induction furnace was evacuated to below 15Pa, and a protective atmosphere of argon gas was introduced to 0.05MPa. Then, an induction power supply was connected to start heating. When all the solids in the crucible melted and the temperature rose to about 1500°C, the induction current was turned off. The robotic arm was quickly operated to immerse the pure copper tube containing the titanium powder, magnesium powder, and Cu-Y alloy below the melt surface. The robotic arm was raised, the induction current was turned on, and the temperature was maintained for 3 minutes. After the temperature was maintained, casting was carried out. After the casting was completed, the ingot was cooled for about 30 minutes and removed. The ingot was milled and then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min and maintained for 3 hours. After the temperature was maintained, the ingot was removed and water-cooled. The solutionized ingot is placed in a muffle furnace at 750°C for 40 minutes, then taken out and sent to a hot rolling mill for a rolling process with a reduction of 20% per pass, and the final rolling amount is 50%. It is then sent to a cold rolling mill and rolled at a reduction rate of 10% per pass to a plate thickness of about 2mm. The plate is then annealed at 400°C for 5 hours, and then rolled at a reduction rate of 10% per pass to a plate thickness of 0.45mm. The plate is then annealed at 300°C for 5 hours, and finally rolled at a reduction rate of 10% per pass to a plate thickness of 0.2mm (any edge cracks that may occur are promptly removed during the cold rolling process), thus obtaining a multi-component synergistically strengthened copper alloy strip for lead frames.

[0037] The performance test of the prepared copper alloy strip was carried out, wherein the mass percentage of each element in the copper alloy strip is as follows:

[0038] Ni: 1.901%; Si: 0.601%; Mg: 0.118%; Co: 0.497%; Ti: 0.059%; Y: 0.008%, and the balance is copper and inevitable impurities.

[0039] The hardness of the copper alloy strip prepared in Example 3 is HV=266.7, and the tensile strength σ b =855.4Mpa, electrical conductivity = 55.8% IACS, yield strength σ 0.2 =758.9MPa.

[0040] Comparative Example 1

[0041] 964g of copper powder, 19g of nickel powder, 6g of silicon powder, and 11g of cobalt powder were added to a crucible in a vacuum induction furnace. The furnace was evacuated to below 15Pa, and a protective argon atmosphere was introduced to 0.05MPa. An induction power supply was then connected to begin heating. Once all the solids in the crucible had melted and the temperature had risen to approximately 1500°C, the induction current was turned off and casting was rapidly performed. After casting, the ingot was cooled for approximately 30 minutes and removed. The ingot was milled and then placed in a muffle furnace, heated to 900°C at a rate of 5°C / min and held for 4 hours. After the ingot was removed and water-cooled, the solutionized ingot was sent to a cold rolling mill, rolled at a rate of approximately 20% per pass until the sheet thickness reached approximately 0.2mm, yielding a copper alloy sheet strip.

[0042] The performance test of the prepared copper alloy strip was carried out, wherein the mass percentage of each element in the copper alloy strip is as follows:

[0043] Ni: 1.901%; Si: 0.583%; Co: 1.082%; the balance being copper and inevitable impurities.

[0044] The hardness of the copper alloy strip prepared in Comparative Example 1 is HV=209.2, and the tensile strength σ b =650.5Mpa, electrical conductivity = 38.4% IACS, yield strength σ 0.2 =553.8MPa.

[0045] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A method for preparing a copper alloy strip for a multi-component synergistically reinforced lead frame, characterized in that: The following steps are involved: (1) Ingredients: Weigh titanium powder, magnesium powder, Cu-Y alloy, silicon powder, cobalt powder, nickel powder and copper powder; (2) Melting: The weighed titanium powder, magnesium powder and Cu-Y alloy are sealed in a pure copper tube and fixed on the robot arm of the vacuum induction furnace. Copper powder, nickel powder, silicon powder and cobalt powder are added to the crucible of the vacuum induction furnace. After the vacuum induction furnace is evacuated, a protective atmosphere is introduced to 0.05 MPa, and then the crucible is heated until all the solids in the crucible are melted and the temperature is raised to 1500 ° C. The induction current is turned off, and the robot arm is quickly operated to immerse the pure copper tube containing the titanium powder, magnesium powder and Cu-Y alloy under the melt surface. The robot arm is lifted and the induction current is turned on to continue to keep the temperature for 2 minutes to 5 minutes. After the temperature is kept, casting is carried out. After the casting is completed, it is cooled to obtain an ingot. (3) Solid solution: The ingot obtained in step (2) is subjected to surface milling treatment, and then placed in a muffle furnace and heated to 800°C to 900°C for 3h to 5h. After the insulation is completed, the ingot is taken out and water-cooled; (4) Hot rolling: The ingot after solutionization is kept at 700℃~800℃ for 15min~40min, taken out and sent to the hot rolling mill for rolling with a reduction of 15%~35% per pass, and the final rolling amount is 50%; (5) Cold rolling: the sample after rolling in step (4) is sent to a cold rolling mill and rolled at a speed of 8% to 12% per pass to a plate thickness of 1.5 mm to 2.5 mm, and then the plate is annealed at 400°C to 450°C for 3h to 5h, and then the plate is rolled at a speed of 8% to 12% per pass to a plate thickness of 0.3 mm to 0.5 mm; the plate is annealed at 300°C to 350°C for 3h to 5h, and finally the plate is rolled at a speed of 8% to 12% per pass to a plate thickness of 0.15 mm to 0.25 mm, thereby obtaining a multi-component synergistically reinforced copper alloy strip for lead frames; The multi-component synergistically reinforced copper alloy strip for lead frame includes the following components in percentage by mass: Ni: 0.9%~3.0%; Si: 0.3%~1.3%; Mg: 0.06%~0.18%; Co: 0.5%~1.5%; Ti: 0.02%~0.1%; Y: 0.05%~0.15%, the balance is copper and inevitable impurities.

2. The preparation method according to claim 1, characterized in that The Y content in the Cu-Y alloy is 15 wt.% to 25 wt.%.

3. The preparation method according to claim 1, characterized in that The protective atmosphere in step (2) is argon or nitrogen.

4. The preparation method according to claim 1, characterized in that The heating rate in step (3) is 3°C~6°C / min.

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