Method for producing low residual stress copper alloy strip, lead frame and connector
By employing an upward continuous casting and multiple annealing processes, the problem of residual stress control in Cu-Fe-P alloy strips was solved, enabling the preparation of alloy strips with high strength and low residual stress, suitable for etching applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGXI COPPER CORP
- Filing Date
- 2023-03-10
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies struggle to effectively control residual stress during the fabrication of Cu-Fe-P alloy strips, especially in etching applications, leading to strip warping issues.
The process flow of upward continuous casting → continuous extrusion → cold rolling → primary annealing → cold precision rolling → secondary annealing is adopted. By controlling the degree of deformation during cold precision rolling and the secondary annealing process, Cu-Fe-P alloy strip with low residual stress is obtained.
Cu-Fe-P alloy strips with tensile strength ≥390MPa, elongation ≥3%, conductivity ≥85%, and surface residual stress in the range of -50 to 50MPa were prepared, meeting the performance requirements for etching applications.
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Figure CN116274914B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of processing technology of integrated circuit and semiconductor component packaging materials, specifically relating to the preparation method of low residual stress copper alloy strip, lead frame and connector. Background Technology
[0002] Currently, leadframe materials are key materials for integrated circuits and semiconductor device packaging, fixing chips, protecting internal components, transmitting electrical signals, and dissipating heat from components within integrated circuits. The most widely used leadframe materials on the market are Cu-Fe-P series alloys, with C19210 alloy becoming a crucial material for the electronic information industry, including integrated circuits and discrete semiconductor devices, due to its excellent electrical and thermal conductivity, processing performance, suitable strength, plating and solderability, compatibility with packaging materials, and relatively low cost. Currently, Cu-Fe-P alloy strips (C19210 / C19400) used for leadframes require a strength of 480-540 MPa and a conductivity of ≥60%. For leadframe strips used in etching, stringent requirements are placed on residual stress to prevent warping after etching. For C19210 alloy strips used in etching, high strength (H-state or EH-state) must be ensured while keeping residual stress at a low level.
[0003] The basic process for producing low residual stress Cu-Fe-P alloy strip is semi-continuous casting → hot rolling → cold rolling → annealing → cold rolling → annealing → cold precision rolling → stress-relief annealing. The mechanical properties of the alloy strip are improved by increasing the cold precision rolling deformation. However, when preparing Cu-Fe-P alloy strip in the H or EH state, the degree of cold precision rolling deformation is too large, and it is difficult to eliminate most of the residual stress of the strip after stress-relief annealing. Summary of the Invention
[0004] This invention discloses a method for preparing low residual stress copper alloy strip, a lead frame, and a connector to solve any of the above-mentioned and potential problems in the prior art.
[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing low residual stress copper alloy strip, the preparation method specifically including the following steps:
[0006] S1) Cu-Fe-P alloy cast rods are prepared by upward continuous casting;
[0007] S2) The cast rod obtained in S1) is continuously extruded to prepare a continuously extruded slab;
[0008] S3) The extruded slab obtained in S2) is subjected to multiple cold rolling passes;
[0009] S4) Anneal the cold-rolled strip obtained in S3);
[0010] S5) The annealed strip obtained in S4) is cold-rolled;
[0011] S6) Anneal the cold-rolled strip of S5) to obtain a copper alloy strip with low residual stress.
[0012] Furthermore, in S1), the casting temperature of the upward continuous casting is 1150-1180℃, and the surface of the melt is covered with baked charcoal during the melting and casting process. The diameter of the casting rod is 16-30mm, and there are no cracks on the surface of the casting rod.
[0013] Furthermore, in S2), the feed rod speed during continuous extrusion is 2.5 to 5 m / min, the extruded slab has no notches on the edge, the thickness of the extruded slab is 10-14 mm, the thickness tolerance is ≤0.5 mm, and the average size of the recrystallized grains of the extruded slab is ≤50 μm.
[0014] Furthermore, in S3), after multiple cold rolling passes, the strip thickness is 0.8mm-1.5mm.
[0015] Furthermore, in step S4), the annealing process is performed in an air quenching furnace with a heating rate ≥20℃ / min, a heating temperature of 420-460℃, a holding time of 0.5-2h, and a cooling rate ≥100℃ / min.
[0016] Furthermore, in S5), the degree of cold finishing rolling is 65-90%, and copper alloy strip with a thickness ≥0.1mm is prepared. The tensile strength of the strip after finishing rolling is 430-480MPa.
[0017] Furthermore, in S6), the annealing process is carried out in a gas quenching furnace for two-stage annealing. The first-stage annealing has a heating rate ≥20℃ / min, an annealing temperature of 230-280℃, and a holding time of 1-3h. The second-stage annealing has a heating rate ≥20℃ / min, an annealing temperature of 350-400℃, a holding time of 0.5-2h, and a cooling rate ≥100℃ / min after annealing.
[0018] Furthermore, the volume fraction of recrystallized grains in the residual stress copper alloy strip is 40-60%, the tensile strength of the strip is ≥390MPa, the elongation is ≥3, the conductivity is ≥85%, and the residual stress on the surface of the strip is between -50 and 50MPa.
[0019] A lead frame comprising a substrate, the substrate being prepared using a low residual stress copper alloy strip obtained by the above-described preparation method.
[0020] A connector comprising a conductor portion prepared from a low residual stress copper alloy strip obtained by the above-described preparation method.
[0021] The advantages and beneficial effects of this invention are as follows: This invention proposes a main process for preparing Cu-Fe-P alloy strip with low residual stress, which is a combination of continuous casting, continuous extrusion, cold rolling, primary annealing, cold finishing rolling, and secondary annealing. The optimal age strengthening effect is obtained by controlling the primary and secondary annealing processes. By controlling the deformation degree of cold finishing rolling to above 65% and the two-stage annealing process of secondary annealing to control the recrystallization volume fraction to 40-60%, the Cu-Fe-P alloy strip is ensured to be in the H state or between EH. At the same time, a higher recrystallization volume fraction can ensure that the strip as a whole is in a low residual stress level.
[0022] This invention can prepare Cu-Fe-P alloy strips with tensile strength ≥390MPa, elongation ≥3, and electrical conductivity ≥85%, with residual stress on the surface of the strips ranging from -50 to 50MPa. Attached Figure Description
[0023] Figure 1 This is a flowchart illustrating a method for preparing a low residual stress copper alloy strip according to the present invention.
[0024] Figure 2 This is a schematic diagram of the metallographic structure after annealing in Embodiment 1 of the present invention.
[0025] Figure 3 This is a schematic diagram of the metallographic structure after annealing in Embodiment 2 of the present invention.
[0026] Figure 4 This is a schematic diagram of the metallographic structure after annealing in Embodiment 3 of the present invention. Detailed Implementation
[0027] The technical solution of the present invention will be further described below with reference to specific embodiments.
[0028] like Figure 1 As shown, the present invention discloses a method for preparing a low residual stress copper alloy strip, the method specifically comprising the following steps:
[0029] S1) Copper alloy casting rods are prepared by upward continuous casting;
[0030] S2) The Cu-Fe-P alloy casting rod obtained in S1) is continuously extruded to prepare a continuously extruded slab;
[0031] S3) The extruded slab obtained in S2) is subjected to multiple cold rolling passes;
[0032] S4) Anneal the cold-rolled strip obtained in S3);
[0033] S5) The annealed strip obtained in S4) is cold-rolled;
[0034] S6) Anneal the cold-rolled strip of S5).
[0035] The casting temperature of the upward continuous casting in S1) is 1150-1180℃, and the surface of the melt is covered with baked charcoal during the casting process.
[0036] In the continuous extrusion process described in S2), the feed rod speed is 2.5 to 5 m / min, the edge of the extruded slab has no notches, the thickness of the extruded slab is 10-14 mm, and the thickness tolerance is ≤0.5 mm.
[0037] After multiple cold rolling passes in S3), the strip thickness is 0.8mm-1.5mm.
[0038] In S4), the annealing process is carried out in an air quenching furnace with a heating rate ≥20℃ / min, a heating temperature of 420-460℃, a holding time of 0.5-2h, and a cooling rate ≥100℃ / min.
[0039] In S5), the degree of cold finishing rolling is 65-90%, and Cu-Fe-P alloy strip with a thickness ≥0.1mm is prepared. The tensile strength of the strip after finishing rolling is 430-480MPa.
[0040] In step S6), the annealing process is carried out in a gas quenching furnace for two-stage annealing. The first-stage annealing has a heating rate ≥20℃ / min, an annealing temperature of 230-280℃, and a holding time of 1-3h. The second-stage annealing has a heating rate ≥20℃ / min, an annealing temperature of 350-400℃, a holding time of 0.5-2h, and a cooling rate ≥100℃ / min after annealing.
[0041] The residual stress Cu-Fe-P alloy strip has a recrystallized grain volume fraction of 40-60%, a tensile strength ≥390MPa, an elongation ≥3%, an electrical conductivity ≥85%, and a surface residual stress of -50 to 50MPa.
[0042] A lead frame comprising a substrate, the substrate being prepared using a low residual stress copper alloy strip obtained by the above-described preparation method.
[0043] A connector comprising a conductor portion prepared from a low residual stress copper alloy strip obtained by the above-described preparation method.
[0044] Example 1
[0045] Low residual stress Cu-Fe-P alloy strips with a thickness of 0.1 mm were prepared using electrolytic copper as raw material, with the addition of copper-iron master alloys and copper-phosphorus master alloys. The Cu-Fe-P alloy composition was controlled to be Fe 0.08–0.12%, P 0.03–0.035%, Sn 0.01–0.02%, with the remainder being copper and unavoidable impurities. Copper alloy cast rods were prepared by upward continuous casting at a casting temperature of 1150–1180℃, with baked charcoal covering the surface of the melt during the casting process. The upward-drawing continuous casting rod is continuously extruded to prepare an extruded slab with a thickness of 12.5 mm. After continuous extrusion, it is cold-rolled in multiple passes to a strip thickness of 0.8 mm. The 0.8 mm cold-rolled strip is heated to 450 °C at a rate of 20 °C / min and held for 1.5 h in an gas quenching furnace, followed by nitrogen quenching with a cooling rate ≥100 °C / min. After annealing, it is cold-finished to 0.1 mm. The cold-finished strip undergoes finished product annealing, using a two-stage annealing process in an gas quenching furnace. First, it is heated to 250 °C at a rate of 20 °C / min and held for 2 h, then further heated to 380 °C and held for 1 h. The metallographic structure after annealing is as follows: Figure 2 As shown, the recrystallization volume fraction is about 42%, the tensile strength of the strip is 397 MPa, the elongation is 4.6%, the conductivity is 87% IACS, and the residual stress on the surface of the strip is -42 MPa.
[0046] Example 2
[0047] Low residual stress Cu-Fe-P alloy strips with a thickness of 0.4 mm were prepared using electrolytic copper as raw material, with the addition of copper-iron master alloys and copper-phosphorus master alloys. The Cu-Fe-P alloy composition was controlled to be Fe 0.08–0.12%, P 0.03–0.035%, Sn 0.01–0.02%, with the remainder being copper and unavoidable impurities. Copper alloy cast rods were prepared by upward continuous casting at a casting temperature of 1150–1180℃, with baked charcoal covering the surface of the melt during the casting process. The upward-drawing continuous casting rod is continuously extruded to prepare an extruded slab with a thickness of 12.5 mm. After continuous extrusion, it is cold-rolled in multiple passes to a strip thickness of 1.5 mm. The 1.5 mm cold-rolled strip is heated to 450 °C at a rate of 20 °C / min and held for 1.5 h in an gas quenching furnace, followed by nitrogen quenching with a cooling rate ≥100 °C / min. After annealing, it is cold-finished to 0.4 mm. The cold-finished strip undergoes finished product annealing, using a two-stage annealing process in an gas quenching furnace. First, the temperature is raised to 250 °C at a rate of 20 °C / min and held for 1.5 h, then further raised to 380 °C and held for 1 h. The metallographic structure after annealing is as follows: Figure 3 As shown, the recrystallization volume fraction is about 50%, the tensile strength of the strip is 393 MPa, the elongation is 5.2%, the conductivity is 88% IACS, and the residual stress on the surface of the strip is -38 MPa.
[0048] Example 3
[0049] Low residual stress Cu-Fe-P alloy strips with a thickness of 0.6 mm were prepared using electrolytic copper as raw material, with the addition of copper-iron master alloys and copper-phosphorus master alloys. The Cu-Fe-P alloy composition was controlled to be Fe 0.08–0.12%, P 0.03–0.035%, Sn 0.01–0.02%, with the remainder being copper and unavoidable impurities. Copper alloy cast rods were prepared by upward continuous casting at a casting temperature of 1150–1180℃, with baked charcoal covering the surface of the melt during the casting process. The upward-drawing continuous casting rod is continuously extruded to prepare an extruded slab with a thickness of 12.5 mm. After continuous extrusion, it is cold-rolled in multiple passes to a strip thickness of 2.3 mm. The 2.3 mm cold-rolled strip is heated to 450 °C at a rate of 20 °C / min and held for 1.5 h in an gas quenching furnace, followed by nitrogen quenching with a cooling rate ≥100 °C / min. After annealing, it is cold-finished to 0.6 mm. The cold-finished strip undergoes finished product annealing, using a two-stage annealing process in an gas quenching furnace. First, the temperature is raised to 250 °C at a rate of 20 °C / min and held for 1.5 h, then further raised to 380 °C and held for 1 h. The metallographic structure after annealing is as follows: Figure 4 As shown, the recrystallization volume fraction is about 46%, the tensile strength of the strip is 398 MPa, the elongation is 4.1%, the conductivity is 87% IACS, and the residual stress on the surface of the strip is 43 MPa.
[0050] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of this application; at the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of this application. Therefore, the content of this specification should not be construed as a limitation of this application.
[0051] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.
[0052] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.
[0053] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0054] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.
Claims
1. A method for preparing a low residual stress copper alloy strip, characterized in that, The preparation method specifically includes the following steps: S1) Cu-Fe-P alloy casting rods are prepared by upward continuous casting; The casting temperature of the upward continuous casting is 1150~1180℃. During the melting and casting process, baked charcoal is used to cover the surface of the melt. The diameter of the casting rod is 16-30mm and there are no cracks on the surface of the casting rod. S2) The Cu-Fe-P alloy casting rod obtained in S1) is continuously extruded to prepare a continuously extruded slab; During the continuous extrusion process, the feed rod speed is 2.5~5m / min, the extruded slab has no notches on the edge, the thickness of the extruded slab is 10-14mm, the thickness tolerance is ≤0.5mm, and the average size of the recrystallized grains of the extruded slab is ≤50μm. S3) The extruded slab obtained in S2) is subjected to multiple cold rolling passes; S4) Anneal the cold-rolled strip obtained in S3); S5) The annealed strip obtained in S4) is cold-rolled; The cold rolling deformation degree is 65-90%, and copper alloy strip with a thickness ≥0.1mm is prepared; S6) Anneal the cold-rolled strip of S5) to obtain a Cu-Fe-P alloy strip with low residual stress; In step S6), the annealing process is carried out in a gas quenching furnace for two-stage annealing. The first-stage annealing has a heating rate ≥20℃ / min, an annealing temperature of 230-280℃, and a holding time of 1-3h. The second-stage annealing has a heating rate ≥20℃ / min, an annealing temperature of 350-400℃, a holding time of 0.5-2h, and a cooling rate ≥100℃ / min after annealing.
2. The preparation method according to claim 1, characterized in that, After multiple cold rolling passes in S3), the strip thickness is 0.8mm-1.5mm.
3. The preparation method according to claim 1, characterized in that, In step S4), the annealing process is performed in an air quenching furnace with a heating rate ≥20℃ / min, a heating temperature of 420-460℃, a holding time of 0.5~2h, and a cooling rate ≥100℃ / min.
4. The preparation method according to claim 1, characterized in that, The residual stress copper alloy strip has a recrystallized grain volume fraction of 40-60%, a tensile strength ≥390MPa, an elongation ≥3%, an electrical conductivity ≥85%, and a surface residual stress of -50~50MPa.
5. A lead frame, the lead frame comprising a substrate, characterized in that, The substrate is a low residual stress copper alloy strip obtained by the preparation method described in any one of claims 1-4.
6. A connector, the connector comprising a conductor portion, characterized in that, The conductor portion is made of a low residual stress copper alloy strip obtained by the preparation method described in any one of claims 1-4.