A copper alloy strip and a method of manufacturing and use thereof

Abstract

The application discloses a copper alloy strip, which comprises the following components in percentage by mass: Ni: 6-7%, Co: 2.0-2.5%, Si: 1.5-2%, Al: 1.0-1.5%, Mg: 0.05-0.15%, Ag: 0.06-0.1%, and the balance of Cu and inevitable impurities. The microstructure of the copper alloy strip comprises a matrix phase and a strengthening phase distributed in the matrix phase, the strengthening phase comprises beta-Ni3Si, delta-(Co, Ni)2Si and Ni3Al, the particle diameter of the strengthening phase is less than or equal to 5 nm, and the particle density per unit area is greater than or equal to 10000 pieces per mu m 2 The application further discloses a preparation method and application of the copper alloy strip. The alloy components are optimized, and a certain heat treatment process is combined, so that the prepared copper alloy has excellent strength, good electric conductivity, high-temperature softening resistance and stress relaxation resistance, and has a wide application prospect in a chip lead frame.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper alloy, in particular to a copper alloy strip and a preparation method and application thereof. BACKGROUND

[0002] With the development of high intelligence, multi-function and miniaturization of electronic and electrical products, the core of control chip also requires multi-core processor and microprocessor. Advanced chips have realized 3 nanometer specifications. As the chip carrier of integrated circuits, lead frames also require ultra-thin, miniaturization and multi-angle lead development, and the transmission current and signal of integrated circuits are required to be increased, so higher requirements are put forward for the performance of the chip carrier of integrated circuits, lead frames.

[0003] At present, the chip terminal production industry proposes that the lead frame of a 3 nanometer chip requires a copper alloy, the product specification is 0.02-0.05mm thickness specification, the tensile strength of the product reaches 1100MPa or more, the yield strength reaches 950MPa or more, the electrical conductivity reaches 30%IACS or more, the hardness reaches 300HV or more, the high-temperature softening resistance can reach 85% or more of the hardness before softening after being kept at 450℃ for 2h, and the stress relaxation resistance is less than 5% after being kept at 150℃ for 100h. However, the current copper alloy series cannot simultaneously meet the performance indicators of electrical conductivity and strength, and the high-temperature softening performance is also difficult to achieve.

[0004] The patent document with publication number CN115287495B discloses a copper alloy strip for semi-etching lead frames, the mass percentage composition of the copper alloy is Fe: 2.0-3.5%, P: 0.03-0.05%, Zn: 0.05-0.3%, Sn: 0.01-0.05%, Nb: 0.1-0.5%, the balance is copper and inevitable trace impurities. By controlling the addition amount of Fe, P, Zn, Sn and Nb, the grain is obviously refined, the structure is uniform, and the tensile strength is above 550MPa and the electrical conductivity is above 60IACS%.

[0005] The patent document with publication number CN115386767B discloses a lead frame copper alloy strip for ultra-large scale integrated circuit chip packaging, the weight percentage composition is: Ni: 2.0-4.0wt%, Co: 0.001-1.0wt%, Si: 0.3-1.2wt%, Nb: 0.001-0.3wt%, the balance is Cu. The yield strength of the copper alloy strip is ≥850MPa, the electrical conductivity is ≥45%IACS, the stress relaxation is ≤20% after being kept at 175℃ for 1000h, the Badway 90° bending R / t is ≤2.0 without cracking, and the hardness value is above 180HV after being kept at 650℃ for 1h.

[0006] Although the prior art has studied copper alloy strip for lead frame, it is known from the above that the current copper alloy strip cannot simultaneously meet the performance index requirements of the 3-nanometer chip lead frame. Therefore, based on application requirements, it is urgent to develop a new copper alloy strip that has good electrical conductivity, excellent high-temperature softening resistance and stress relaxation resistance while maintaining high strength. SUMMARY

[0007] To solve the above problems, the present application provides a copper alloy strip, which has high strength, good electrical conductivity, excellent high-temperature softening resistance and stress relaxation resistance, and can be used for the preparation of chip lead frames.

[0008] A copper alloy strip, comprising the following components in mass percentage: Ni: 6-7%, Co: 2.0-2.5%, Si: 1.5-2%, Al: 1.0-1.5%, Mg: 0.05-0.15%, Ag: 0.06-0.1%, and the balance being Cu and unavoidable impurities, the microstructure of the copper alloy strip comprising a matrix phase and a strengthening phase distributed in the matrix phase, the strengthening phase comprising β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al, the particle diameter of the strengthening phase being ≤5nm, and the particle density per unit area being ≥10000 / μm 2 .

[0009] The alloy component ratio of the present application is scientific and reasonable, and Ni, Co, Si and Al elements are added, so that β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al exist in the alloy microstructure, the strengthening phase is distributed at the grain boundary and along the grain boundary, plays the effect of pinning the grain boundary movement, improves the strength and high-temperature softening resistance of the material, and the diameter size of β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al is within 5nm, and the particle density per unit area is 10000 / μm 2 , which fully plays the dispersion strengthening effect of the strengthening phase and greatly improves the strength, electrical conductivity, high-temperature softening resistance and stress relaxation resistance of the material.

[0010] Preferably, the mass ratio of Ni, Co and Si in the copper alloy strip satisfies 4.1≤(Ni+Co) / Si≤4.5. Si can be solid-solved in the alloy matrix during solid solution treatment, and can form second phase β-Ni3Si, δ-(Co, Ni)2Si strengthening phase with Ni and Co during aging treatment, plays the second phase aging precipitation strengthening effect, greatly improves the strength, electrical conductivity and stress relaxation resistance of the alloy, and when the mass ratio of Ni+Co to Si is 4.1-4.5, the aging strengthening effect of the alloy is most obvious.

[0011] Preferably, the mass ratio of Ni and Al in the copper alloy strip satisfies 8≤Ni / Al≤10. Al can significantly improve the corrosion resistance of the alloy, while the second phase strengthening phase Ni3Al is precipitated when Ni and Al in the alloy are solid solution and aging, thereby improving the strength and stress relaxation resistance of the alloy. When the weight ratio of Ni / Al is 8-10, the alloy has the best comprehensive performance.

[0012] Mg can play a deoxidizing role in the alloy, purify the melt, and improve the casting characteristics of the alloy. Meanwhile, Mg can be partially solid-solved in the matrix to improve the high-temperature softening resistance and stress relaxation resistance of the alloy. During aging treatment, Mg can further promote the complete precipitation of the second phases β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al, thereby improving the performance of the alloy.

[0013] The addition of trace Ag can further improve the recrystallization temperature and creep strength of the alloy, improve the high-temperature softening resistance and stress relaxation resistance of the material, and has an alloy strengthening effect. Meanwhile, trace Ag has little effect on the electrical conductivity of the alloy, and the electrical conductivity of the alloy after the addition of Ag can still be maintained above 30% IACS.

[0014] Preferably, the grain size of the copper alloy strip is ≤0.5 μm. According to the Hall-Petch formula σ s = σ0+ Kd -1 / 2 (σ s is the yield strength of the material; d is the average diameter of the grain; σ0 is the yield strength of a single crystal, which is a constant; K is the influence coefficient of the grain boundary on the strength, which is a constant), it can be concluded that the finer the grain size within a certain range, the higher the strength of the material. The grain size of the copper alloy strip is controlled to be ≤0.5 μm, thereby improving the strength of the material.

[0015] Preferably, the tensile strength of the copper alloy strip is ≥1100 MPa, the yield strength is ≥950 MPa, the electrical conductivity is ≥30% IACS, the hardness is ≥300 HV, the high-temperature softening resistance is ≥85% of the original hardness after being kept at 450℃ for 2h, and the stress relaxation rate is <5% after being kept at 150℃ for 100h. The copper alloy strip has high strength, good electrical conductivity, excellent high-temperature softening resistance and stress relaxation resistance.

[0016] More preferably, the tensile strength of the copper alloy strip is ≥1200 MPa, the yield strength is ≥1150 MPa, the electrical conductivity is ≥30% IACS, the hardness is ≥330 HV, the high-temperature softening resistance is ≥85% of the original hardness after being kept at 450℃ for 2h, and the stress relaxation rate is <4.5% after being kept at 150℃ for 100h.

[0017] Preferably, the thickness of the copper alloy strip is 0.02-0.05 mm. The copper alloy strip with the thickness can meet the thickness specification requirement of the chip lead frame material.

[0018] The application further provides a preparation method of the copper alloy strip, comprising the following technological process: batching smelting, semi-continuous casting, hot rolling, rough rolling, solid solution annealing, medium rolling, aging treatment, finished product rolling, bending straightening and stress relief annealing.

[0019] The hot rolling process is as follows: the ingot heating temperature is 980-1040 DEG C, the holding time is 2-3 h, the hot rolling starting temperature is 940-980 DEG C, the final rolling temperature is above 750 DEG C, the final rolling adopts online cooling solid solution, the hot rolling processing rate is above 90%, and the conductive rate of the hot rolled blank is controlled to be 12-15% IACS.

[0020] The solid solution annealing process is as follows: the annealing temperature is 950-1000 DEG C, and the annealing speed is 70-100 m / min.

[0021] The aging treatment process is as follows: first heating to 320-350 DEG C, holding for 8-10 h, then heating to 420-450 DEG C, and holding for 4-6 h.

[0022] The application promotes the precipitation of the strengthening phases beta-Ni3Si, delta-(Co, Ni)2Si and Ni3Al by the cooperation of the hot rolling, solid solution annealing and aging treatment process, controls the particle size and grain size of the strengthening phase, and greatly improves the strength, conductive rate, high temperature softening resistance and stress relaxation resistance of the material.

[0023] The ingot heating temperature is 980-1040 DEG C, the holding time is 2-3 h, the hot rolling starting temperature is 940-980 DEG C, the final rolling temperature is above 750 DEG C, the hot rolling processing rate is above 90%, the final rolling adopts online cooling solid solution, and the conductive rate of the hot rolled blank is controlled to be 12-15% IACS, so as to ensure the online solid solution effect of the hot rolled blank, and be beneficial to the further improvement of the second phase precipitation and dispersion distribution effect in the aging treatment.

[0024] On the basis of the hot rolling process, the application adopts one-time high-temperature solid solution rapid air cushion annealing, the annealing temperature is 950-1000℃, and the annealing speed is 70-100m / min. The one-time high-temperature solid solution rapid air cushion annealing firstly softens the cold work-hardened material, improves the processing plasticity of the material, and facilitates the subsequent cold working. Meanwhile, the high-temperature solid solution rapid air cushion annealing fully solid-solutes the alloy elements in the matrix, improves the solid solubility of the matrix, increases the precipitation capacity of the later strengthening phase, cooperates with the aging treatment process, promotes the precipitation of the strengthening phases Ni3Si phase, Ni3Al and δ-(Co, Ni)2Si, and ensures that the electrical conductivity of the alloy product reaches more than 30% IACS, and the alloy strength reaches the design requirements.

[0025] Preferably, the average grain size of the copper alloy strip after the solid solution annealing is controlled to be within 1μm, and the electrical conductivity is controlled to be within 10-14% IACS.

[0026] After obtaining the copper alloy strip after the solid solution annealing, the application adopts a ladder aging treatment process, firstly heats to 320-350℃, keeps warm for 8-10h, then increases the temperature to 420-450℃, and keeps warm for 4-6h. In the ladder aging treatment process, Ni, Co, Si and Al precipitate to form the second phase strengthening phase, the early main strengthening phase is β-Ni3Si phase and Ni3Al phase, the peak aging state is the common strengthening of Ni3Si phase, Ni3Al and δ-(Co, Ni)2Si phase, and the strengthening effect of δ-(Co, Ni)2Si phase is mainly, thereby improving the electrical conductivity, strength and stress relaxation resistance of the alloy; in addition, the solid solubility of Mg is much greater than that in copper, in the ladder aging treatment process, the Mg phase exists on the surface and inside of Ni3Si phase, Ni3Al and δ-(Co, Ni)2Si, prevents the growth of these second phases, but promotes the nucleation of Ni3Si phase, Ni3Al and δ-(Co, Ni)2Si, thereby increasing the precipitation quantity of the second phase, ensuring that the diameters of the precipitated second phase Ni3Si phase, Ni3Al and δ-(Co, Ni)2Si strengthening phase particles are less than 5nm, and the precipitated strengthening phase particles per unit area are 10000 / μm 2 Therefore, the second phase dispersion strengthening effect is greatly improved, thereby improving the strength and high-temperature softening resistance of the material.

[0027] Preferably, the processing rate of the rough rolling is 95-98%, the processing rate of the medium rolling is 80-90%, and the processing rate of the finished product rolling is 45-50%.

[0028] Preferably, the stress relief annealing is online stress relief annealing, the annealing temperature is 380-420℃, the annealing speed is 100-150m / min, the protective gas is nitrogen and hydrogen mixed gas, and the hydrogen content is 2-4%.

[0029] The present application adopts online stress relief annealing, the processing texture organization grain of the alloy is fully recovered during the annealing process, the processing internal stress of the material is completely eliminated, the etching dimensional stability of the alloy strip in processing lead frame is improved, and the prepared copper alloy has good ductility and bending resistance.

[0030] The present application adopts large processing rate in rough rolling and medium rolling to texture the organization, and combines with the stress relief annealing process to ensure the grain size and performance of the alloy organization.

[0031] The present application also provides the application of the above-mentioned copper alloy strip in chip lead frame.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The present application optimizes the alloy components and combines with certain heat treatment processing technology to control the organization structure of the copper alloy.

[0034] (2) The present application adopts online stress relief annealing, the processing texture organization grain of the alloy is fully recovered during the annealing process, the processing internal stress of the material is completely eliminated, the etching dimensional stability of the alloy strip in processing lead frame is improved, and the prepared copper alloy has good ductility and bending resistance.

[0035] (3) The tensile strength of the copper alloy strip of the present application reaches 1100 MPa or more, the yield strength reaches 950 MPa or more, the conductivity reaches 30% IACS or more, the hardness reaches 300 HV or more, the high-temperature softening resistance is 85% or more of the hardness before softening after 2h of heat preservation at 450℃, and the stress relaxation resistance is less than 5% after 100h of heat preservation at 150℃, which can meet the performance requirements of chip lead frame and has a broad application prospect in chip lead frame. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments.

[0037] The chemical composition of the copper alloy strip in the embodiment of the present application is shown in Table 1.

[0038] Table 1 Chemical composition of copper alloy strip (wt%)

[0039] Ni Co Si Al Mg Ag Other Cu 6-7 2.0-2.5 1.5-2.0 1.0-1.5 0.05-0.15 0.06-0.1 <0.05 Balance

[0040] The preparation process of the copper alloy strip in the embodiment of the present application is as follows: batching smelting, semi-continuous casting, hot rolling on-line cooling solid solution, face milling, rough rolling, edge cutting, high-temperature solid solution rapid air cushion annealing, medium rolling, step aging treatment, finished product rolling, draw bending straightening, stress relief low-temperature air cushion annealing and cleaning. The specific steps are as follows:

[0041] S1, batching smelting

[0042] The electrolytic copper is added into the smelting furnace for heating and melting, and the smelting furnace melt is tightly covered with dry charcoal; then the temperature is raised to 1340-1380℃, pure nickel, cobalt, silicon, aluminum and silver are added according to the component proportion, slagging is performed after 30-50 minutes, covering agent is used for covering, the covering thickness is 80-100mm, the gas diffuser installed at the bottom of the furnace is opened, and the mixed gas of 80% high-purity N2 and 20% high-purity CO is introduced, the gas pressure is 0.1-0.3MPa, and the bottom blowing gas flow is 40-60L / min. After 1-1.5h of heat preservation, the copper-magnesium intermediate alloy is added according to the proportion, and the temperature of the copper liquid is reduced to 1300-1340℃.

[0043] S2, semi-continuous casting

[0044] The temperature of the copper liquid is controlled at 1300-1340℃, the stopper is opened, and the copper water is put into the crystallizer, then the cooling water is opened, and when the height of the copper liquid in the crystallizer reaches about two-thirds of the crystallizer, the traction machine is started to begin the casting work at 20-30mm / min, the vibration is started, the frequency of the vibrator is 30-50 times / min, and the amplitude is 5-7mm, and the graphite powder spraying covering is adopted during the whole casting process; when the ingot is cast to 0.5-1.0m, the steady casting stage is reached, the casting speed is controlled at 40-50mm / min, and the red ingot technology is used for casting, i.e. only the primary cooling water of the crystallizer is used without secondary cooling water, and the temperature of the ingot when it comes out of the crystallizer port is above 700℃. The flow of the primary cooling water of the crystallizer is 10-15m 3 / h, the water pressure is 0.4-0.6MPa, the inlet water temperature is 20-28℃, and the outlet water temperature is controlled at 40-50℃. The casting specification of the ingot is 160*620mm*8000mm.

[0045] S3, hot rolling on-line cooling solid solution

[0046] The ingot heating temperature is 980-1040 °C, the holding time is 2-3 h, the hot rolling starting temperature is 940 °C-980 °C, the final rolling temperature is above 750 °C, and the electrical conductivity of the hot-rolled blank is controlled at 12-15% IACS. The hot rolling reduction is above 90%, and the width of the hot-rolled strip is 650±5 mm.

[0047] S4, face milling

[0048] The single-face milling amount is 0.8-1.2 mm.

[0049] S5, rough rolling

[0050] The rough rolling reduction is controlled at 95-98%.

[0051] S6, edge cutting

[0052] The single-edge cutting is 7-8 mm, and the width of the cut strip is 635±0.5 mm.

[0053] S7, high-temperature solid solution rapid air cushion annealing

[0054] The annealing temperature is 950-1000 °C, the annealing speed is 70-100 m / min, the protective gas is a mixture of nitrogen and hydrogen gas, and the hydrogen content is 2-4%. After the first annealing, the average grain size is controlled within 1 μm, and after full solid solution, the electrical conductivity is controlled at 10-14% IACS.

[0055] S8, intermediate rolling

[0056] The intermediate rolling reduction is controlled at 80-90%.

[0057] S9, step aging treatment

[0058] First, heating to 320-350 °C, holding for 8-10 h, then heating to 420-450 °C, holding for 4-6 h. The grain size of the material is controlled within 0.5 μm, and the diameters of the precipitated strengthening phases β-Ni3Si, δ-(Co,Ni)2Si and Ni3Al are within 5 nm, and the precipitated strengthening phase particles per unit area are 10000 / μm 2 The above fully plays the role of the strengthening phase dispersion strengthening, greatly improves the strength, electrical conductivity and high-temperature softening resistance of the material. If the precipitated strengthening phase particle size is above 20 nm, its strengthening effect is greatly reduced, and it is difficult to play a sufficient strengthening effect. The electrical conductivity of the aged alloy is improved from 10-14% IACS before aging to above 30% IACS after aging.

[0059] S10, finished product rolling

[0060] The finished product is rolled by a 20-roll finishing mill, and the processing rate is controlled at 45-50%.

[0061] S11, stretch bending and straightening

[0062] During the stretch bending and straightening, the straightening elongation is 0.15-0.2%, and the straightening unit tension is 25-30 kg / mm 2 .

[0063] S12, stress relief low-temperature air cushion annealing

[0064] The single sheet unfolding type air cushion furnace is used for on-line stress relief annealing, the annealing temperature is 380-420 DEG C, the annealing speed is 100-150 m / min, the protective gas is the mixed gas of nitrogen and hydrogen, and the hydrogen content is 2-4%.

[0065] S13, cleaning

[0066] First, degreasing is carried out, the degreasing agent is sodium hydroxide aqueous solution, the PH range is 7-9, and the solution temperature is 60-70 DEG C; then, pickling is carried out, the sulfuric acid concentration is 100-130 g / l, the temperature is ≤40 DEG C, the Cu 2+ content in the acid solution is ≤1.2 g / l; cleaning and drying are carried out, and the oven temperature is 65-70 DEG C.

[0067] S14, finished product slitting and packaging.

[0068] The thickness of the copper alloy strip prepared in the embodiment of the application is 0.02-0.05 mm, the tensile strength of the product reaches more than 1100 MPa, the yield strength reaches more than 950 MPa, the conductivity reaches more than 30% IACS, the hardness reaches more than 300 HV, the high-temperature softening resistance can reach more than 85% of the hardness before softening after being kept at 450 DEG C for 2 h, and the stress relaxation resistance is less than 5% after being kept at 150 DEG C for 100 h, so the product is suitable for being used as a material for producing lead frames.

[0069] The technical scheme and effects of the application will be illustrated by specific examples.

[0070] The specific components of the copper alloy strips of examples 1-4 and comparative examples 1-4 are shown in table 2, and the key process parameters are shown in table 3.

[0071] Example 1

[0072] The preparation steps of the copper alloy strip of the embodiment are as follows:

[0073] 1), batching and smelting

[0074] The electrolytic copper is added into the smelting furnace to be heated and melted, the smelting furnace melt is tightly covered with dry charcoal; then the temperature is raised to 1370℃, pure nickel, cobalt, silicon, aluminum and silver are added according to the component proportion, the slag is taken out after 38 minutes, the covering agent is used for covering, the covering thickness is 89mm, the gas diffuser installed at the bottom of the furnace is opened, the mixed gas of 80% high-purity N2 and 20% high-purity CO is input, the gas pressure is 0.17MPa, the bottom blowing gas flow is 45L / min. After 1.2h of heat preservation, the copper-magnesium intermediate alloy is added according to the proportion, and the temperature of the copper liquid is reduced to 1330℃.

[0075] 2) Semi-continuous casting

[0076] The temperature of the copper liquid is controlled at 1330℃, the stopper is opened, and the copper water is put into the crystallizer, then the cooling water is opened, when the height of the copper liquid in the crystallizer reaches about two-thirds of the crystallizer, the traction machine is started to begin the casting work at 22mm / min, the vibration is started, the frequency of the vibrator is 38 times / min, the amplitude is 5.6mm, and the graphite powder spraying covering is adopted during the whole casting process; when the ingot is cast to 0.8m, the steady casting stage is reached, the casting speed is controlled at 48mm / min, the red ingot technology is used for casting, that is, only the primary cooling water of the crystallizer is used without secondary cooling water, and the temperature of the ingot when it is out of the crystallizer is at 730℃. The flow of the primary cooling water of the crystallizer is 12m 3 / h, the water pressure is 0.5MPa, the water inlet temperature is 25℃, and the water outlet temperature is controlled at 48℃. The ingot casting specification is 160*620mm*8000mm.

[0077] 3) Hot rolling on-line cooling solid solution

[0078] The heating temperature of the ingot is 1020℃, the heat preservation time is 2.4h, the hot rolling starting temperature is 960℃, and the final rolling temperature is at 780℃, so that the conductivity of the hot-rolled blank is controlled at 14% IACS. The hot rolling thickness is 15mm, the hot rolling processing rate is controlled at 90.62%, and the width of the hot-rolled strip is 650±5mm.

[0079] 4) Milling

[0080] The single-side milling amount is 1.0mm.

[0081] 5) Rough rolling

[0082] The rough rolling is to 0.6mm, and the rough rolling processing rate is controlled at 95.38%.

[0083] 6) Edge cutting

[0084] The single-side cutting is 7.5mm, and the width of the cut strip is 635±0.5mm.

[0085] 7) High-temperature solid solution rapid air cushion annealing

[0086] The annealing temperature is 980°C, the annealing speed is 90 m / min, the protective gas is a mixture of nitrogen and hydrogen gas, and the hydrogen content is 2.6%. The average grain size is controlled at 0.7 μm after the first annealing.

[0087] 8) Medium rolling

[0088] The medium rolling is to 0.096 mm, and the processing rate is controlled at 84%.

[0089] 9) Staged aging treatment

[0090] First, heating to 330°C, holding for 9 h, then heating to 430°C, holding for 5.5 h. The grain size of the material is controlled at 0.3 μm, and the diameters of the precipitated strengthening phases β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al are controlled at 2 nm. The precipitated strengthening phase particles per unit area are 14118 / μm2. 2 .

[0091] 10) Final rolling

[0092] The final rolling is performed by using a 20-roll finishing mill, and the final rolling is to 0.05 mm, and the processing rate is controlled at 47.92%.

[0093] 11) Stretch bending and straightening

[0094] The straightening elongation is 0.17%, and the straightening unit tension is 28 kg / mm 2 .

[0095] 12) Stress relief low-temperature air cushion annealing

[0096] The on-line stress relief annealing is performed by using a single sheet unfolding air cushion furnace, the annealing temperature is 390°C, the annealing speed is 120 m / min, the protective gas is a mixture of nitrogen and hydrogen gas, and the hydrogen content is 2.5%.

[0097] 13) Cleaning

[0098] First, degreasing is performed by using a sodium hydroxide aqueous solution, the PH range is 7.9, and the solution temperature is 68°C; then, pickling is performed by using sulfuric acid, the sulfuric acid concentration is 115 g / l, the temperature is 35°C, the Cu 2+ solubility in the acid solution is 0.8 g / l; cleaning and drying are performed by using an oven, and the oven temperature is 68°C.

[0099] 14) Final product slitting and packaging

[0100] Example 2

[0101] The preparation steps of the copper alloy strip of the present example are as follows:

[0102] 1) Melting

[0103] The electrolytic copper is added into the melting furnace to be heated and melted, and the melting furnace melt is tightly covered with dry charcoal; then the temperature is raised to 1355℃, and pure nickel, cobalt, silicon, aluminum and silver are added according to the component proportion, and after 45 minutes, the slag is removed, covered with a covering agent, and the covering thickness is 95mm, the gas diffuser installed at the bottom of the furnace is opened, and the mixed gas of 80% high-purity N2 and 20% high-purity CO is introduced, the gas pressure is 0.12MPa, and the bottom blowing gas flow is 45L / min. After 1.45h of heat preservation, the copper-magnesium intermediate alloy is added in proportion, and the temperature of the copper liquid is reduced to 1320℃.

[0104] 2) Semi-continuous casting

[0105] The temperature of the copper liquid is controlled at 1320℃, the stopper is opened, and the copper water is put into the crystallizer, then the cooling water is opened, and when the height of the copper liquid in the crystallizer reaches about two-thirds of the crystallizer, the traction machine is started to begin the casting work at 26mm / min, the vibration is started, the frequency of the vibrator is 35 times / min, and the amplitude is 5.5mm. Graphite powder is used for covering during the whole casting process; when the ingot is cast to 0.9m, the steady casting stage is reached, the casting speed is controlled at 44mm / min, and the red ingot technology is used for casting, i.e. only the primary cooling water of the crystallizer is used without secondary cooling water, and the temperature of the ingot when it comes out of the crystallizer is 770℃. The flow rate of the primary cooling water of the crystallizer is 13m 3 / h, the water pressure is 0.52MPa, and the inlet water temperature is 26℃, and the outlet water temperature is controlled at 42℃. The casting ingot has a specification of 160*620mm*8000mm.

[0106] 3) Hot rolling and on-line cooling and solid solution

[0107] The heating temperature of the ingot is 990℃, the heat preservation time is 3h, the starting temperature of hot rolling is 950℃, and the final rolling temperature is 790℃, so as to ensure that the electrical conductivity of the hot-rolled blank is controlled at 15% IACS. The hot rolling thickness is 15mm, the hot rolling processing rate is controlled at 90.62%, and the width of the hot-rolled strip is 650±5mm.

[0108] 4) Milling

[0109] The single-side milling amount is 1.0mm.

[0110] 5) Rough rolling

[0111] The rough rolling is to 0.6mm, and the rough rolling processing rate is controlled at 95.38%.

[0112] 6) Edge cutting

[0113] The single-side cutting is 7.5mm, and the width of the cut strip is 635±0.5mm.

[0114] 7) High temperature solution and rapid air cushion annealing

[0115] The annealing temperature is 960°C, the annealing speed is 78 m / min, the protective gas is a mixture of nitrogen and hydrogen gas, and the hydrogen content is 3.1%. The average grain size is controlled at 0.6 μm after the first annealing.

[0116] 8) Medium rolling

[0117] The medium rolling is to 0.085 mm, and the processing rate is controlled at 85.83%.

[0118] 9) Staged aging treatment

[0119] First heated to 325°C, and kept for 10 h, then heated to 445°C, and kept for 4.5 h. The grain size of the material is controlled at 0.27 μm, and the diameters of the precipitated strengthening phases β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al are controlled at 1.9 nm. The precipitated strengthening phase particles per unit area are 14235 / μm2. 2 .

[0120] 10) Final rolling

[0121] The final rolling is performed by using a 20-roll finishing mill, and the final rolling is to 0.045 mm, and the processing rate is controlled at 47.05%.

[0122] 11) Tension leveling and straightening

[0123] The straightening elongation is 0.18%, and the straightening unit tension is 29 kg / mm 2 .

[0124] 12) Stress relief low temperature air cushion annealing

[0125] The on-line stress relief annealing is performed by using a single sheet air cushion furnace, the annealing temperature is 390°C, the annealing speed is 140 m / min, and the protective gas is a mixture of nitrogen and hydrogen gas, and the hydrogen content is 2.9%.

[0126] 13) Cleaning

[0127] First, the degreasing is performed by using a sodium hydroxide aqueous solution, the PH range is 8.5, and the solution temperature is 67°C; then, the pickling is performed by using sulfuric acid, the sulfuric acid concentration is 124 g / l, the temperature is 37°C, the Cu 2+ solubility in the acid solution is 0.75 g / l; and then, the cleaning and drying are performed by using an oven, and the oven temperature is 67°C.

[0128] 14) Final product slitting and packaging

[0129] Example 3

[0130] The preparation steps of the copper alloy strip of the present embodiment are as follows:

[0131] 1) batching and smelting

[0132] The electrolytic copper is added into the smelting furnace for heating and melting, and the smelting furnace melt is tightly covered with dry charcoal; then the temperature is raised to 1355℃, and pure nickel, cobalt, silicon, aluminum and silver are added according to the component ratio, slagging is performed after 47 minutes, covering agent is used for covering, the covering thickness is 96mm, the gas diffuser installed at the bottom of the furnace is opened, and the mixed gas of 80% high-purity N2 and 20% high-purity CO is introduced, the gas pressure is 0.26MPa, and the bottom blowing gas flow is 57L / min. After 1.1h of holding, the copper-magnesium intermediate alloy is added in proportion, and the temperature of the copper liquid is reduced to 1325℃.

[0133] 2) semi-continuous casting

[0134] The temperature of the copper liquid is controlled at 1325℃, the stopper is opened, and the copper water is put into the crystallizer, then the cooling water is opened, and when the height of the copper liquid in the crystallizer reaches about two-thirds of the crystallizer, the traction machine is started to begin the casting work at 26mm / min, the vibration is started, the frequency of the vibrator is 38 times / min, and the amplitude is 6.7mm. Graphite powder is used for covering during the whole casting process; when the ingot is cast to 0.7m, the steady casting stage is reached, the casting speed is controlled at 43mm / min, and the red ingot technology is used for casting, i.e. only the primary cooling water of the crystallizer is used without secondary cooling water, and the temperature of the ingot when it comes out of the crystallizer port is above 762℃. The flow rate of the primary cooling water of the crystallizer is 12m 3 / h, the water pressure is 0.48MPa, and the inlet water temperature is 22℃, and the outlet water temperature is controlled at 47℃. The casting specification of the ingot is 160*620mm*8000mm.

[0135] 3) hot rolling and online cooling and solid solution

[0136] The heating temperature of the ingot is 1011℃, the holding time is 2.4h, the starting temperature of hot rolling is 970℃, and the final rolling temperature is 795℃, so as to ensure that the electrical conductivity of the hot-rolled blank is controlled at 13.5% IACS. The hot rolling is performed to 14mm, and the processing rate is controlled at 91.25%, and the width of the hot-rolled strip is 650±5mm.

[0137] 4) face milling

[0138] The single-face milling amount is 1.0mm.

[0139] 5) rough rolling

[0140] The rough rolling is performed to 0.55mm, and the processing rate is controlled at 95.42%.

[0141] 6) edge cutting

[0142] Single shear 7-8mm, shear width 635±0.5mm.

[0143] 7) High temperature solution rapid air cushion annealing

[0144] Single sheet unfolding air cushion furnace annealing, annealing temperature 955℃, annealing speed 75m / min, protective gas nitrogen and hydrogen mixed gas, hydrogen content 3.3%. The average grain size after the first annealing is controlled at 0.57μm.

[0145] 8) Medium rolling

[0146] Medium rolling to 0.075mm, medium rolling processing rate controlled at 86.36%.

[0147] 9) Staged aging treatment

[0148] First heated to 345℃, holding for 8.5h, then heated to 435℃, holding for 5h. Ensures the material grain size control within 0.25μm, while ensuring the precipitated strengthening phase β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al etc. diameter size at 1.8nm, unit area precipitated strengthening phase particles at 15823 / μm 2 .

[0149] 10) Finished product rolling

[0150] Finished product rolling using 20-roll finishing mill, finished product rolling to 0.04mm, processing rate controlled at 46.67%.

[0151] 11) Stretch bending straightening

[0152] Stretch bending straightening, straightening elongation 0.17%, straightening unit tension 27kg / mm 2 .

[0153] 12) Stress relief low temperature air cushion annealing

[0154] Single sheet unfolding air cushion furnace online stress relief annealing, annealing temperature 395℃, annealing speed 132m / min, protective gas nitrogen and hydrogen mixed gas, hydrogen content 2.8%.

[0155] 13) Cleaning

[0156] First degreasing, degreasing agent using sodium hydroxide aqueous solution, PH range 7.8, solution temperature 64℃; then pickling, sulfuric acid concentration 118g / l, temperature 36℃, Cu 2+ solubility in acid solution 0.69g / l; cleaning and drying, oven temperature 66℃.

[0157] 14) Finished product slitting, packaging.

[0158] Example 4

[0159] The preparation steps of the copper alloy strip of the present example are as follows:

[0160] 1) batch smelting

[0161] The electrolytic copper was added into the smelting furnace for heating and melting, and the smelting furnace melt was tightly covered with dry charcoal; then the temperature was raised to 1365℃, and pure nickel, cobalt, silicon, aluminum and silver were added according to the component ratio, slagging was performed after 39 minutes, covering agent was used for covering, the covering thickness was 92mm, the gas diffuser installed at the bottom of the furnace was opened, and the mixed gas of 80% high-purity N2 and 20% high-purity CO was blown in, the gas pressure was 0.24MPa, and the bottom blowing gas flow was 51L / min. After 1.3h of holding, the copper-magnesium intermediate alloy was added in proportion, and the temperature of the copper liquid was reduced to 1325℃.

[0162] 2) semi-continuous casting

[0163] The temperature of the copper liquid was controlled at 1325℃, the stopper was opened, and the copper water was put into the crystallizer, then the cooling water was opened, and when the height of the copper liquid in the crystallizer reached about two-thirds of the crystallizer, the traction machine was started to begin the casting work at 28mm / min, the vibration was turned on, the frequency of the vibrator was 42 times / min, and the amplitude was 6.3mm. Graphite powder was used for covering during the whole casting process; when the ingot was cast to 0.65m, the steady casting stage was reached, the casting speed was controlled at 48mm / min, and the red ingot technology was used for casting, i.e. only the primary cooling water of the crystallizer was used without secondary cooling water, and the temperature of the ingot when it came out of the crystallizer was at 775℃. The flow rate of the primary cooling water of the crystallizer was 12m 3 / h, the water pressure was 0.52MPa, and the inlet water temperature was 23℃, and the outlet water temperature was controlled at 46℃. The casting specification of the ingot was 160*620mm*8000mm.

[0164] 3) hot rolling and online cooling and solid solution

[0165] The heating temperature of the ingot was 995℃, the holding time was 2.7h, the starting temperature of hot rolling was 962℃, and the final rolling temperature was at 793℃, so as to ensure that the electrical conductivity of the hot-rolled blank was controlled at 14.2% IACS. The hot rolling was performed to 14mm, the processing rate was controlled at 91.25%, and the width of the hot-rolled strip was 650±5mm.

[0166] 4) face milling

[0167] The amount of single face milling was 1.0mm.

[0168] 5) rough rolling

[0169] The rough rolling was performed to 0.5mm, and the processing rate was controlled at 95.83%.

[0170] 6) Trimming

[0171] The single edge shear is 7.5 mm, and the width of the strip after shearing is 635 ± 0.5 mm.

[0172] 7) High temperature solution rapid air cushion annealing

[0173] The single sheet air cushion furnace annealing is adopted, the annealing temperature is 965 °C, the annealing speed is 84 m / min, the protective gas is a mixed gas of nitrogen and hydrogen, and the hydrogen content is 2.8%. The average grain size after the first annealing is controlled within 0.5 μm.

[0174] 8) Medium rolling

[0175] The medium rolling is to 0.057 mm, and the medium rolling processing rate is controlled at 88.6%.

[0176] 9) Staged aging treatment

[0177] First heated to 335 °C, and kept for 9 h, then heated to 440 °C, and kept for 4.8 h. The grain size of the material is controlled within 0.2 μm, and the diameters of the precipitated strengthening phases β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al are controlled within 1.5 nm, and the precipitated strengthening phase particles per unit area are 17427 / μm 2 .

[0178] 10) Finished product rolling

[0179] The finished product rolling is adopted by using a 20-roll finishing mill, the finished product is rolled to 0.03 mm, and the processing rate is controlled at 47.37%.

[0180] 11) Tension bending straightening

[0181] When tension bending straightening, the straightening elongation is 0.16%, and the straightening unit tension is 27 kg / mm 2 .

[0182] 12) Stress relief low temperature air cushion annealing

[0183] The single sheet air cushion furnace is adopted for online stress relief annealing, the annealing temperature is 385 °C, the annealing speed is 120 m / min, the protective gas is a mixed gas of nitrogen and hydrogen, and the hydrogen content is 2.3%.

[0184] 13) Cleaning

[0185] First, degreasing is performed, the degreasing agent is a sodium hydroxide aqueous solution, the PH range is 7.9, and the solution temperature is 67 °C; then, pickling is performed, the sulfuric acid concentration is 108 g / l, the temperature is 36 °C, the Cu 2+Solubility 0.76 g / l; cleaning and drying in an oven at 68°C.

[0186] 14) Finishing, slitting and packaging.

[0187] Comparative Example 1

[0188] The copper alloy strip of this example contains the following elements in mass percentage: Ni 6.5%, Co 2.25%, Si 1.75%, Mg 0.125%, Ag 0.08%, and the balance being Cu. No Al is added in the alloying elements. The preparation steps are the same as those of Example 4.

[0189] Comparative Example 2

[0190] The copper alloy strip of this example contains the following elements in mass percentage: Ni 6.5%, Co 2.25%, Si 1.75%, Al 1.25%, and the balance being Cu. No Mg and Ag are added in the alloying elements. The preparation steps are the same as those of Example 4.

[0191] Comparative Example 3

[0192] The copper alloy strip of this example contains the following elements in mass percentage: Ni 6.5%, Co 2.25%, Si 1.75%, Al 1.25%, Mg 0.125%, Ag 0.08%, and the balance being Cu. The difference between the preparation steps of this example and those of Example 4 is that bell furnace annealing is used in Step 7) at a temperature of 550°C for 6h.

[0193] Comparative Example 4

[0194] The copper alloy strip of this example contains the following elements in mass percentage: Ni 6.5%, Co 2.25%, Si 1.75%, Al 1.25%, Mg 0.125%, Ag 0.08%, and the balance being Cu. The difference between the preparation steps of this example and those of Example 4 is that single aging treatment is used in Step 9) at an annealing temperature of 435°C for 5h.

[0195] Table 2 Chemical composition of the copper alloy strips of the examples and comparative examples of the present application / wt%

[0196] No. Ni Co Si Al Mg Ag Cu Example 1 6.2 2.4 1.8 1.2 0.06 0.09 Balance Example 2 6.7 2.3 1.7 1.4 0.08 0.07 Balance Example 3 6.8 2.2 1.6 1.3 0.15 0.085 Balance Example 4 6.5 2.25 1.75 1.25 0.125 0.08 Balance Comparative Example 1 6.5 2.25 1.75 — 0.125 0.08 Balance Comparative Example 2 6.5 2.25 1.75 1.25 — — Balance Comparative Example 3 6.5 2.25 1.75 1.25 0.125 0.08 Balance Comparative Example 4 6.5 2.25 1.75 1.25 0.125 0.08 Balance

[0197] Table 3 Key process parameter control of the examples and comparative examples of the present application

[0198]

[0199] The mechanical properties, electrical conductivity, and microstructure of the copper alloy strips prepared in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are shown in Table 4. The testing methods are as follows:

[0200] Mechanical property test: room temperature tensile test was carried out according to GB / T 228.1-2010 Metallic materials - Tensile test - Part 1 : Method of test at room temperature on an electronic universal mechanical property testing machine, using a 20mm wide specimen with a tensile speed of 5mm / min.

[0201] Conductivity test: according to GB / T 3048.2-2007 Electrical performance test methods for wire and cable - Part 2: Resistivity test of metallic materials, using %IACS.

[0202] Metallographic structure grain size test: according to GB / T 6394-2007 Metallic materials - Determination of average grain size - Intercept method, the grain size in the photos collected by a 1000 times metallographic microscope was tested. The width of the sample was 10mm and the length was 10mm.

[0203] Table 4: structure and properties of each embodiment of the present application and comparative examples

[0204]

[0205] The tensile strength of the copper alloy strip prepared in Examples 1-4 reached 1100MPa or more, the yield strength reached 950MPa or more, the conductivity reached 30%IACS or more, the hardness reached 300HV or more, the high temperature softening resistance was that the hardness after keeping at 450℃ for 2h was 85% or more of the hardness before softening, and the stress relaxation resistance was that the stress relaxation rate was less than 5% after keeping at 150℃ for 100h, so the copper alloy strip had good stress relaxation resistance, very high strength, excellent high temperature softening resistance and conductivity.

[0206] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A copper alloy strip, characterized by, The copper alloy strip comprises the following components in percentage by mass: Ni: 6-7%, Co: 2.0-2.5%, Si: 1.5-2%, Al: 1.0-1.5%, Mg: 0.05-0.15%, Ag: 0.06-0.1%, and the balance of Cu and inevitable impurities, and the microstructure of the copper alloy strip comprises a matrix phase and a strengthening phase distributed in the matrix phase, the strengthening phase comprises β-Ni3Si, δ-(Co, Ni)2Si and Ni3Al, the particle diameter of the strengthening phase is ≤5 nm, and the particle density per unit area is ≥10000 / μm2 2 ; The copper alloy strip is prepared by the following process flow: ingredient smelting, semi-continuous casting, hot rolling, rough rolling, solid solution annealing, medium rolling, aging treatment, finished product rolling, bending straightening and stress relief annealing, The solid solution annealing process is that the annealing temperature is 950-1000 DEG C, and the annealing speed is 70-100 m / min. The aging treatment process is that the temperature is first heated to 320-350 DEG C, and then heated to 420-450 DEG C after 8-10 h of heat preservation. The hardness ratio of the copper alloy strip after heat preservation at 450 DEG C for 2 h to the original hardness is greater than or equal to 85%, and the stress relaxation rate after heat preservation at 150 DEG C for 100 h is less than 5%.

2. The copper alloy strip of claim 1, wherein The mass ratio of Ni, Co and Si in the copper alloy strip satisfies 4.1 <= (Ni+Co) / Si <= 4.

5.

3. The copper alloy strip of claim 1, wherein The mass ratio of Ni and Al in the copper alloy strip satisfies 8 <= Ni / Al <= 10.

4. The copper alloy strip of claim 1, wherein The grain size of the copper alloy strip is less than or equal to 0.5 mu m.

5. The copper alloy strip of claim 1, wherein The tensile strength of the copper alloy strip is greater than or equal to 1100 MPa, the yield strength is greater than or equal to 950 MPa, and the conductivity is greater than or equal to 30% IACS.

6. The copper alloy strip of claim 1, wherein The hot rolling process is that the ingot heating temperature is 980-1040 DEG C, the heat preservation time is 2-3 h, the hot rolling starting temperature is 940-980 DEG C, the final rolling temperature is above 750 DEG C, the final rolling adopts online cooling solidification, the hot rolling processing rate is above 90%, and the conductivity of the hot rolled blank is controlled to be 12-15% IACS.

7. The copper alloy strip of claim 1, wherein The average grain size of the copper alloy strip after solid solution annealing is controlled to be within 1 mu m, and the conductivity is controlled to be 10-14% IACS.

8. The copper alloy strip of claim 7, wherein The rough rolling processing rate is 95-98%, the medium rolling processing rate is 80-90%, and the finished product rolling processing rate is 45-50%.

9. The copper alloy strip of claim 8, wherein, The stress relief annealing is online stress relief annealing, the annealing temperature is 380-420 DEG C, the annealing speed is 100-150 m / min, the protective gas is a mixed gas of nitrogen and hydrogen, and the hydrogen content is 2-4%.

10. The copper alloy strip according to any one of claims 1-9 is applied in a chip lead frame.

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