A method for preparing CuCrSn alloy thin strip for etching lead frames

Abstract

This invention relates to a method for preparing CuCrSn alloy thin strip for etching lead frames, characterized by the following steps: S1, weighing powder raw materials; S2, mechanical alloying: mechanically alloying the powder raw materials to obtain alloyed powder; S3, uniformly mixing the alloyed powder with a binder and spray drying to obtain granulated powder particles; S4, powder rolling and forming: rolling the granulated powder particles into green strip; S5, continuously debinding and sintering the green strip to obtain a sintered body; S6, cold rolling the sintered body and then performing a second sintering to obtain a second sintered body; S7, precision rolling and annealing the second sintered body. Compared with the prior art, this invention has a simple process; the prepared CuCrSn alloy thin strip has low residual stress, good shape control, and high etching quality.

Description

Technical Field

[0001] This invention relates to the field of metal material preparation technology, specifically to a method for preparing CuCrSn alloy thin strip for etching lead frames. Background Technology

[0002] Leadframes are one of the key components of integrated circuits, playing a vital role in support, protection, connection, conduction, and heat dissipation. With the ultra-large-scale development of integrated circuits, leadframes are evolving towards multi-pin, ultra-thin, and high-precision designs. Etching has gradually become the main processing method for forming high-precision leadframes, which requires leadframe materials to possess higher mechanical and electrical properties and better machinability.

[0003] CuCrSn alloys possess high strength, electrical conductivity, and good etching performance, making them a preferred material for manufacturing lead frames for very large-scale integrated circuits. Currently, a combination of melting and casting and deformation heat treatment processes is widely used to prepare CuCrSn alloy thin strips. However, due to the low solid solubility of Cr in Cu, Cr precipitates at the grain boundaries of the Cu matrix during solidification, forming relatively large second-phase particles. These unevenly distributed coarse particles easily cause stress concentration, increasing the residual stress inside the rolled strip. Furthermore, traditional methods require multiple rolling deformations, which is not only cumbersome but also results in high strip deformation resistance, difficulty in controlling the strip shape, and compromised etching quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing CuCrSn alloy thin strip for etching lead frames, which has the characteristics of simple process, low residual stress, good plate shape control and high etching quality.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a method for preparing CuCrSn alloy thin strip for etching lead frame, characterized in that it includes the following steps: S1, weighing powder raw materials;

[0006] S2. Mechanical alloying: Mechanically alloying powder raw materials to obtain alloyed powder;

[0007] S3. Spray dry and granulate the alloyed powder to obtain granulated powder particles.

[0008] S4. Powder rolling forming: Rolling granulated powder particles into raw strips;

[0009] S5. The raw strip is continuously degreased and sintered to obtain a sintered body;

[0010] S6. After cold rolling, the sintered body is sintered a second time to obtain a second sintered body;

[0011] S7. The second sintered body is precision rolled and annealed.

[0012] Preferably, in step S1, the powder raw material is 0.3-0.6 wt.% Cr powder and 0.1-0.3 wt.% Sn powder, with the balance being Cu powder, and the purity of the powder raw material is ≥99.99%. Controlling the element content within the above range can fully utilize the strengthening effect of alloying elements, while avoiding a significant reduction in conductivity due to excessive elements dissolving in the matrix.

[0013] Preferably, in step S1, the average particle size of Cr powder and Sn powder is 3-8 μm, and the particle size of electrolytic Cu powder is 10-30 μm.

[0014] Preferably, in step S2, the ball milling temperature is 5-20℃, the ball milling time is 10-60 hours, and an Ar atmosphere is introduced for protection. Controlling the ball milling temperature at 5-20℃ using cooling water is beneficial for the mechanical alloying of the powder raw materials.

[0015] Preferably, in step S3, the binder is 0.8-1.2 wt.% paraffin alcohol by weight of the alloyed powder, and the granulated powder particles have a flowability of 25-30 s and a bulk density of 3.5-4 g / cm³. 3 By controlling the flowability and bulk density of the prepared powder particles within the above-mentioned range through spray drying granulation, it can be ensured that the raw strip has sufficiently high strength and density after the powder is rolled into shape.

[0016] Preferably, in step S4, the rolling speed of the powder is 1-30 m / min, the green strip thickness is 0.2-0.5 mm, and an H2 atmosphere is used for protection. Controlling the rolling speed and green strip thickness within these ranges ensures both uniform thickness and density of the green strip and efficient production. This invention uses H2, which has low viscosity, as a protective gas, which helps to reduce or eliminate the adverse effects of gases in the powder on the rolling process.

[0017] Preferably, in step S5, the degreasing temperature is 400-500℃, the degreasing time is 20-40 min, the sintering temperature is 800-900℃, and the sintering time is 40-80 min. The degreasing and sintering are carried out under H2 atmosphere protection. Degreasing and sintering can be performed continuously under H2 atmosphere protection, and the strip length is not limited.

[0018] Preferably, in step S6, the total cold rolling deformation rate is 30-50%, the secondary sintering temperature is 900-950℃, the sintering time is 30-60 min, Ar atmosphere protection is used during the secondary sintering, and gas quenching is performed after the secondary sintering. Controlling the cold rolling deformation rate within the above range can both strengthen the alloy and better control residual stress; the secondary sintering further densifies the strip, and gas quenching after sintering avoids the precipitation of a large amount of alloying elements.

[0019] Preferably, in step S7, the finishing rolling deformation rate is 15-20%, the annealing temperature is 400-450℃, the annealing time is 30-120 min, the annealing is carried out under N2 atmosphere protection, and the annealing tension is 10-30 N / mm. 2 By introducing dislocations into the strip through precision rolling, fine and dispersed second-phase precipitation can be promoted during annealing, thereby improving the strength and conductivity of the alloy strip. The annealing tension should be controlled at 10-30 N / mm. 2 This can effectively reduce residual stress.

[0020] Compared with the prior art, the advantages of the present invention are: the second phase particles inside the prepared CuCrSn alloy thin strip are small and dispersed, with low residual stress, good plate shape control and high etching quality; the preparation process does not require melting and casting and cumbersome rolling deformation process, and has the advantages of short process flow, low preparation cost and suitability for large-scale production. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process of the present invention;

[0022] Figure 2 This is a transmission electron microscope (TEM) image of the CuCrSn alloy thin strip from Example 1 of the present invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] Figure 1 The preparation process diagrams of Examples 1-5 are shown.

[0025] Example 1:

[0026] S1. Weigh the powdered raw materials: the contents of Cr powder and Sn powder are 0.5wt.% and 0.3wt.% respectively, the average particle size of electrolytic Cu powder is 10μm, and the average particle size of Cr powder and Sn powder is 3μm.

[0027] S2. Mechanical alloying: The powder raw material is mechanically alloyed using ball milling to obtain alloyed powder; the ball milling temperature is 5℃, the ball milling time is 20h, and Ar protection is used.

[0028] S3. Spray Drying Granulation: The alloying powder and binder are mixed evenly and then spray-dried to obtain granulated powder particles. The binder is paraffin alcohol, and the weight of paraffin alcohol is 1 wt.% of the weight of the alloying powder. The resulting granulated powder particles have a flowability of 30s and a loose packing density of 3.8 g / cm³. 3 .

[0029] S4. Powder rolling forming: The granulated powder particles are rolled into a green strip; the rolling speed is 10m / min, the green strip thickness is 0.4mm, and H2 protection is applied.

[0030] S5. Continuous degreasing and sintering: continuous degreasing temperature 400℃, degreasing time 40min, sintering temperature 820℃, sintering time 60min, H2 protection.

[0031] S6. Cold rolling and secondary sintering: The sintered body is cold rolled and then sintered again to obtain a second sintered body; the total deformation rate of cold rolling is 50%, and the deformation rate per pass is 17%. The secondary sintering temperature is 950℃, the sintering time is 45min, Ar protection is used, the N2 flow rate at the discharge port is 5m / s, and the pressure is 0.2MPa.

[0032] S7. Finish rolling and annealing: The second sintered body is finished rolled and annealed to obtain CuCrSn alloy thin strip; the finish rolling deformation rate is 15%, the annealing temperature is 440℃, the annealing time is 40min, N2 protection is applied during annealing, and the annealing tension is 15N / mm. 2 .

[0033] Figure 2 This is a transmission electron microscopy (TEM) image of the CuCrSn alloy strip from this embodiment. The CuCrSn alloy strip obtained in this embodiment has a tensile strength of 578 MPa, a conductivity of 75.3% IACS, a warpage of 0.1 mm, a lateral bend of 0.05 mm after etching, a twist of 0.55 mm, and a particle protrusion of 0.007 mm on the etched side.

[0034] Example 2:

[0035] S1. Weigh the powdered raw materials: the contents of Cr powder and Sn powder are 0.5wt.% and 0.2wt.% respectively, the average particle size of electrolytic Cu powder is 20μm, and the average particle size of Cr powder and Sn powder is 5μm.

[0036] S2. Mechanical alloying: The powder raw material is mechanically alloyed using ball milling to obtain alloyed powder; the ball milling temperature is 9℃, the ball milling time is 26h, and Ar protection is applied.

[0037] S3. Spray Drying Granulation: The alloying powder and binder are mixed evenly and then spray-dried to obtain granulated powder particles. The binder used in spray drying granulation is paraffin alcohol, which accounts for 1 wt.% of the weight of the alloying powder. The resulting granulated powder particles have a flowability of 29 s and a bulk density of 3.9 g / cm³. 3 .

[0038] S4. Powder rolling forming: Roll the granulated powder particles into a green strip; the rolling speed is 5m / min, the green strip thickness is 0.5mm, and H2 protection is used.

[0039] S5. Continuous degreasing and sintering: The raw strip is continuously degreased and sintered to obtain a sintered body; the continuous degreasing temperature is 400℃, the degreasing time is 35min, the sintering temperature is 880℃, the sintering time is 50min, and H2 protection is applied.

[0040] S6. Cold rolling and secondary sintering: The sintered body is cold rolled and then sintered again to obtain a second sintered body; the total deformation rate of cold rolling is 40%, and the deformation rate per pass is 15%. The secondary sintering temperature is 940℃, the sintering time is 60min, Ar protection is used, the N2 flow rate at the discharge port is 3m / s, and the pressure is 0.1MPa.

[0041] S7. Finish rolling and annealing: The second sintered body is finished rolled and annealed to obtain CuCrSn alloy thin strip; the finish rolling deformation rate is 15%, the annealing temperature is 400℃, the annealing time is 60min, N2 protection is applied during annealing, and the annealing tension is 18N / mm. 2 .

[0042] The obtained CuCrSn alloy strip has a tensile strength of 585MPa, a conductivity of 74.6% IACS, a warpage of 0.08mm, a side bend of 0.04mm after etching, a twist of 0.42mm, and a particle protrusion of 0.008mm on the etched side.

[0043] Example 3:

[0044] S1. Weigh the powdered raw materials: the contents of Cr powder and Sn powder are 0.4wt.% and 0.3wt.% respectively, the average particle size of electrolytic Cu powder is 20μm, and the average particle size of Cr powder and Sn powder is 8μm.

[0045] S2. Mechanical alloying: The powder raw material is mechanically alloyed using ball milling to obtain alloyed powder; the ball milling temperature is 15℃, the ball milling time is 34h, and Ar protection is applied.

[0046] S3. Spray Drying Granulation: The alloying powder and binder are mixed evenly and then spray-dried to obtain granulated powder particles. The binder used in spray drying granulation is paraffin alcohol, and the weight of paraffin alcohol is 1 wt.% of the weight of the alloying powder. The resulting granulated powder particles have a flowability of 28 s and a loose packing density of 3.9 g / cm³. 3 .

[0047] S4. Powder rolling forming: Roll the granulated powder particles into a green strip; the rolling speed is 15m / min, the green strip thickness is 0.3mm, and H2 protection is applied.

[0048] S5. Continuous degreasing and sintering: The raw strip is continuously degreased and sintered to obtain a sintered body; the continuous degreasing temperature is 450℃, the degreasing time is 20min, the sintering temperature is 860℃, the sintering time is 40min, and H2 protection is applied.

[0049] S6. Cold rolling and secondary sintering: The sintered body is cold rolled and then sintered again to obtain a second sintered body; the total deformation rate of cold rolling is 45%, and the deformation rate per pass is 15%. The secondary sintering temperature is 950℃, the sintering time is 38min, Ar protection is used, the N2 flow rate at the discharge port is 6m / s, and the pressure is 0.3MPa.

[0050] S7. Finish rolling and annealing: The second sintered body is finished rolled and annealed to obtain CuCrSn alloy thin strip; the finish rolling deformation rate is 18%, the annealing temperature is 430℃, the annealing time is 70min, N2 protection is applied during annealing, and the annealing tension is 18N / mm. 2 .

[0051] The obtained CuCrSn alloy strip has a tensile strength of 565MPa, a conductivity of 76.6% IACS, a warpage of 0.09mm, a side bend of 0.07mm after etching, a twist of 0.56mm, and a particle protrusion of 0.010mm on the etched side.

[0052] Example 4:

[0053] S1. Weigh the powdered raw materials: the contents of Cr powder and Sn powder are 0.6 wt.% and 0.25 wt.%, respectively, the average particle size of electrolytic Cu powder is 10 μm, and the average particle size of Cr powder and Sn powder is 4 μm.

[0054] S2. Mechanical alloying: The powder raw material is mechanically alloyed using ball milling to obtain alloyed powder; the ball milling temperature is 18℃, the ball milling time is 30h, and Ar protection is used to obtain alloyed powder.

[0055] S3. Spray Drying Granulation: The alloying powder and binder are mixed evenly and then spray-dried to obtain granulated powder particles. The binder used in spray drying granulation is paraffin alcohol, and the weight of paraffin alcohol is 1.2 wt.% of the weight of the alloying powder. The resulting granulated powder particles have a flowability of 25 s and a loose packing density of 4 g / cm³. 3 .

[0056] S4. Powder rolling forming: The granulated powder particles are rolled into a green strip; the rolling speed is 23m / min, the green strip thickness is 0.2mm, and H2 protection is applied.

[0057] S5. Continuous degreasing and sintering: The raw strip is continuously degreased and sintered to obtain a sintered body; the continuous degreasing temperature is 450℃, the degreasing time is 35min, the sintering temperature is 900℃, the sintering time is 40min, and H2 protection is applied.

[0058] S6. Cold rolling and secondary sintering: The sintered body is cold rolled and then sintered again to obtain a second sintered body; the total deformation rate of cold rolling is 48%, and the deformation rate per pass is 16%. The secondary sintering temperature is 930℃, the sintering time is 38min, Ar protection is used, the N2 flow rate at the discharge port is 8m / s, and the pressure is 0.4MPa.

[0059] S7. Finish rolling and annealing: The second sintered body is finished rolled and annealed to obtain CuCrSn alloy thin strip; the finish rolling deformation rate is 18%, the annealing temperature is 450℃, the annealing time is 35min, N2 protection is applied during annealing, and the annealing tension is 22N / mm. 2 .

[0060] The obtained CuCrSn alloy strip has a tensile strength of 560MPa, a conductivity of 76.7% IACS, a warpage of 0.11mm, a side bend of 0.09mm after etching, a twist of 0.87mm, and a particle protrusion of 0.011mm on the etched side.

[0061] Example 5:

[0062] S1. Weigh the powdered raw materials: the contents of Cr powder and Sn powder are 0.45wt.% and 0.3wt.% respectively, the average particle size of electrolytic Cu powder is 15μm, and the average particle size of Cr powder and Sn powder is 6μm.

[0063] S2. Mechanical alloying of powder raw materials: ball milling temperature 12℃, ball milling time 28h, Ar protection, to obtain alloyed powder.

[0064] S3. Spray Drying Granulation: The alloying powder and binder are mixed evenly and then spray-dried to obtain granulated powder particles. The binder is paraffin alcohol, and the weight of paraffin alcohol is 1 wt.% of the weight of the alloying powder. The resulting granulated powder particles have a flowability of 27 s and a loose packing density of 4 g / cm³. 3 .

[0065] S4. Powder rolling forming: The granulated powder particles are rolled into a green strip; the rolling speed is 18m / min, the green strip thickness is 0.25mm, and H2 protection is used.

[0066] S5. Continuous degreasing and sintering: The raw strip is continuously degreased and sintered to obtain a sintered body; the continuous degreasing temperature is 470℃, the degreasing time is 25min, the sintering temperature is 860℃, the sintering time is 40min, and H2 protection is applied.

[0067] S6. Cold rolling and secondary sintering: The sintered body is cold rolled and then sintered again to obtain a second sintered body; the total deformation rate of cold rolling is 48%, and the deformation rate per pass is 16%. The secondary sintering temperature is 945℃, the sintering time is 35min, Ar protection is used, the N2 flow rate at the discharge port is 6m / s, and the pressure is 0.3MPa.

[0068] S7. Finish rolling and annealing: The second sintered body is finished rolled and annealed to obtain CuCrSn alloy thin strip; the finish rolling deformation rate is 20%, the annealing temperature is 420℃, the annealing time is 47min, N2 protection is applied during annealing, and the annealing tension is 20N / mm. 2 .

[0069] The obtained CuCrSn alloy strip has a tensile strength of 571 MPa, a conductivity of 75.5% IACS, a warpage of 0.08 mm, a side bend of 0.06 mm after etching, a twist of 0.62 mm, and a particle protrusion of 0.009 mm on the etched side.

[0070] Comparative Example 1:

[0071] The difference between this comparative example and Example 1 is that the secondary sintering was omitted. The prepared CuCrSn alloy strip has a tensile strength of 488MPa, a conductivity of 60.4% IACS, a warpage of 0.32mm, a side bend of 0.25mm after etching, a twist of 0.93mm, and a particle protrusion of 0.023mm on the etched side.

[0072] Comparative Example 2:

[0073] The difference between this comparative example and Example 4 is that spray drying granulation was omitted. The prepared CuCrSn alloy strip has a tensile strength of 507MPa, a conductivity of 64.8% IACS, a warpage of 0.09mm, a side bend of 0.13mm after etching, a twist of 0.85mm, and a particle protrusion of 0.015mm on the etched side.

Claims

1. A method for preparing CuCrSn alloy thin strip for etching lead frames, characterized in that: Includes the following steps: S1. Weigh the powdered raw material; the powdered raw material is 0.3-0.6 wt.% Cr powder and 0.1-0.3 wt.% Sn powder, with the balance being Cu powder, and the purity of the powdered raw material is ≥99.99%; S2. Mechanical alloying: The powder raw material is mechanically alloyed using ball milling to obtain alloyed powder; the ball milling temperature is 5-20℃, the ball milling time is 10-60h, and Ar atmosphere is introduced for protection. S3. Spray drying granulation: The alloying powder and binder are mixed evenly and then spray dried to obtain granulated powder particles; the binder is paraffin alcohol at 0.8-1.2 wt.% of the weight of the alloying powder; the granulated powder particles have a flowability of 25-30 s and a loose packing density of 3.5-4 g / cm³. 3 ; S4. Powder rolling forming: Rolling granulated powder particles into raw strips; S5. The raw strip is continuously degreased and sintered to obtain a sintered body; S6. After cold rolling, the sintered body is sintered again to obtain a second sintered body; S7. The second sintered body is precision rolled and annealed.

2. The method for preparing CuCrSn alloy thin strip for etching lead frames according to claim 1, characterized in that: In step S1, the average particle size of Cr powder and Sn powder is 3-8 μm, and the particle size of electrolytic Cu powder is 10-30 μm.

3. The method for preparing CuCrSn alloy thin strip for etching lead frames according to claim 1, characterized in that: In step S4, the rolling speed of the powder rolling is 1-30 m / min, the thickness of the green strip is 0.2-0.5 mm, and it is protected by H2 atmosphere.

4. The method for preparing CuCrSn alloy thin strip for etching lead frames according to claim 1, characterized in that: In step S5, the degreasing temperature is 400-500℃, the degreasing time is 20-40 min, the sintering temperature is 800-900℃, and the sintering time is 40-80 min. The degreasing and sintering are carried out under H2 atmosphere protection.

5. The method for preparing CuCrSn alloy thin strip for etching lead frames according to claim 1, characterized in that: In step S6, the total cold rolling deformation rate is 30-50%, the secondary sintering temperature is 900-950℃, the sintering time is 30-60min, Ar atmosphere protection is used during the secondary sintering, and gas quenching is performed after the secondary sintering is completed.

6. The method for preparing CuCrSn alloy thin strip for etching lead frames according to claim 1, characterized in that: In step S7, the finishing rolling deformation rate is 15-20%, the annealing temperature is 400-450℃, the annealing time is 30-120 min, the annealing process is carried out under N2 atmosphere protection, and the annealing tension is 10-30 N / mm. 2 .

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