Silver bonding wire for packaging and preparation method and application thereof

Abstract

The present invention provides a silver bonding wire for packaging and a preparation method and application thereof. The preparation method comprises: (1) weighing a metal raw material: the metal raw material comprises the following components by mass fraction: 1.4-2.1% gold, 2.8-3.3% palladium, 0.3-0.7% copper, 0.02-0.06% tin, 0.03-0.05% cerium, 0.03-0.06% ytterbium, 0.04-0.08% calcium, 0.003-0.005% chromium, 0.004-0.009% beryllium, 0.006-0.01% lanthanum, and the balance is silver; (2) melting and casting; (3) wire drawing; (4) final annealing; (5) solidification and packaging. The present invention improves the reliability of packaging by introducing a specific amount of palladium, gold and copper into silver, supplemented with a variety of elements, and adjusting the annealing conditions, while improving the mechanical properties of 20μm silver bonding wire. The silver bonding wire is suitable for high-density packaging of micro LED devices.

Description

Technical Field

[0001] The invention belongs to the technical field of silver bonding wires, and in particular relates to a silver bonding wire for packaging, a preparation method thereof and an application thereof. Background Art

[0002] Bonding wire is a special metal wire used in the semiconductor packaging process. It is mainly used for the connection inside the chip and the electrical interconnection between the chip and the external pins. Its main function is to weld metal wires such as gold, aluminum, and copper to the pads or lead frames on the silicon wafer by ultrasonic or hot pressing at high temperature to form a reliable electrical connection. Common bonding wire materials include gold, aluminum, copper, silver, etc., according to different application requirements. With the development of high density, high speed and miniaturization of electronic packaging, gold bonding wire can no longer meet the requirements due to cost and performance issues. Copper and silver bonding wires with lower costs have gradually become substitutes for gold wires, but copper bonding wires have problems such as high hardness, easy oxidation, and complex processes. Silver is low in cost and has excellent electrical and thermal conductivity when used as a bonding wire. It is one of the most promising materials for the future development of high integration, high density and high speed of electronic packaging.

[0003] As the LED market scale expands and the demand for cost control increases, the use of silver alloy wire can significantly reduce packaging costs without affecting or less affecting product performance. At the same time, the strong reflective performance of silver alloy helps to improve the luminous efficiency of LED devices, especially in certain packaging structures, silver alloy wire can play an auxiliary reflection role and improve the utilization rate of light sources. The miniaturization of LEDs has promoted its application in more high-tech fields, such as wearable devices, smart lighting, car displays, virtual reality, augmented reality and other emerging fields. These applications require LED devices to be lighter, thinner and more flexible. However, with the development of LED miniaturization, the performance requirements for silver bonding wires are also constantly increasing. Therefore, there is an urgent need for a silver bonding wire with better mechanical properties, conductivity and stability to meet the needs of smaller and higher-performance LED devices. Summary of the invention

[0004] The purpose of the present invention is to provide a silver bonding wire for packaging and a preparation method and application thereof, wherein the reliability and stability of the silver bonding wire are improved.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for preparing a silver bonding wire for packaging, comprising the following steps:

[0006] (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 1.4-2.1% gold, 2.8-3.3% palladium, 0.3-0.7% copper, 0.02-0.06% tin, 0.03-0.05% cerium, 0.03-0.06% ytterbium, 0.04-0.08% calcium, 0.003-0.005% chromium, 0.004-0.009% beryllium, 0.006-0.01% lanthanum, and the balance is silver;

[0007] (2) Melting and casting: The metal raw materials are subjected to vacuum melting and directional continuous casting process to obtain core wire rods with a diameter of 6-8 mm;

[0008] (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 6-8 cm, the core wire rod after rough drawing is medium drawn to a diameter of 0.8-1.0 cm, a first intermediate annealing is performed, the wire obtained by medium drawing is finely drawn to a diameter of 0.1-0.3 mm, a second intermediate annealing is performed, and the wire obtained by fine drawing is ultra-finely drawn to 20-40 μm to obtain a silver alloy bonding wire;

[0009] (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix;

[0010] (5) Curing and packaging: Cool the silver alloy bonding wire substrate to 20-30° C., and perform winding and packaging to obtain the silver alloy bonding wire for LED packaging.

[0011] In the prior art, palladium is usually introduced into the silver alloy wire to improve the reliability of LED packaging, but the premise is that the ratio of the welding bonding surface during ball welding (i.e., the ratio of the area of ​​the welding bonding area to the overall overlapping area) is greater than 80%. However, in actual welding, the welding bonding surface ratio is not only related to the characteristics of the wire itself, but also to factors such as the cleanliness of the free air ball (FAB) surface and the LED chip pad surface during ball welding, resulting in the unsatisfactory reliability of the silver bonding wire with only palladium added. In addition to palladium, the present invention also adds a certain amount of gold and copper to the silver bonding wire, which can improve the reliability of the silver bonding wire for LED packaging when the ratio of the welding bonding surface (i.e., the ratio of the area of ​​the welding bonding area to the overall overlapping area) is less than 80%, thereby improving the yield of the product. Analysis shows that under this condition, the grains of the organization are refined and more uniform, and the ability of natural aging softening is improved, and the diffusion rate of the intermediate compound during welding with aluminum is delayed, which can maintain the structural integrity of the welding area, thereby improving the reliability of the packaging. During LED packaging, chloride ions in the packaging molding compound may also release sulfur. Once water vapor penetrates or is adsorbed, the bonded metal wire will be corroded. The inventors have improved the corrosion resistance of silver bonding wires by adding a certain proportion of tin, cerium, ytterbium, calcium, chromium, beryllium, and lanthanum to the system of the present invention. The analysis shows that multi-element doping can change the grain boundary voltage, thereby reducing electrochemical corrosion.

[0012] Furthermore, the conditions of the first intermediate annealing are: the effective length of the annealing furnace is 700-900 mm, the annealing temperature is 520-570° C., and the annealing rate is 110-120 m / min.

[0013] Furthermore, the conditions of the second intermediate annealing are: the effective length of the annealing furnace is 700-900 mm, the annealing temperature is 400-450° C., and the annealing rate is 90-100 m / min.

[0014] Furthermore, in the step (4), the effective length of the annealing furnace is 700-900 mm, the annealing temperature is 500-550° C., and the annealing rate is 70-80 m / min.

[0015] Furthermore, the temperature of vacuum melting in step (2) is 1150-1350°C.

[0016] Furthermore, the conditions of the directional continuous casting process in step (2) are: under argon atmosphere, pressure 0.02-0.05 Pa, speed 30-50 mm / min.

[0017] 20μm silver bonding wire can be widely used in LED miniaturized packaging due to its advantages of small space occupation and cost savings. 20μm silver bonding wire is conducive to precision bonding in a smaller space, and is particularly suitable for high-density packaging and micro LED devices, which can meet the increasingly miniaturized and refined packaging requirements. However, the breaking load and elongation of 20μm silver bonding wire in the prior art are not ideal. The present invention improves the mechanical strength of 20μm silver bonding wire by adjusting the conditions of intermediate annealing and final annealing. It is analyzed that multiple annealing can optimize the microstructure of the silver bonding wire, change the residual stress inside the silver bonding wire, and improve the ductility and tensile strength.

[0018] The second aspect of the present invention provides a silver bonding wire for packaging obtained by the above preparation method.

[0019] Furthermore, the diameter of the silver bonding wire for packaging is 20 μm, the breaking load is 10-11 cN, and the elongation is 10-11%.

[0020] A third aspect of the present invention provides an application of silver bonding wire for packaging, wherein the silver bonding wire is used for high-density packaging of micro LED devices.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0022] 1. The present invention introduces a specific amount of palladium, gold and copper into silver, supplemented with a variety of elements, and adjusts the annealing conditions to solve the problem that the reliability of the prior art silver bonding wire containing palladium is affected by the welding bonding surface ratio, thereby improving the reliability of the package and improving the mechanical properties of the 20μm silver bonding wire. The silver bonding wire of the present invention is suitable for high-density packaging of micro LED devices.

[0023] 2. In addition to palladium, the present invention also adds a certain amount of gold and copper to the silver bonding wire, which can improve the reliability of LED packaging using the silver bonding wire when the welding bonding surface ratio (i.e. the ratio of the area of ​​the welding bonding area to the overall overlapping area) is lower than 80%, thereby improving the product yield.

[0024] 3. The present invention can improve the corrosion resistance of silver bonding wire by adding a certain proportion of tin, cerium, ytterbium, calcium, chromium, beryllium and lanthanum to the system of the present invention.

[0025] 4. The present invention improves the mechanical strength of 20 μm silver bonding wire by adjusting the conditions of intermediate annealing and final annealing, which is of great significance for the high-density packaging of silver bonding wire for micro LED devices. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] This embodiment provides a silver bonding wire for packaging, and the preparation method thereof comprises the following steps:

[0029] (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 1.8% gold, 3.1% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver;

[0030] (2) Melting and Casting: The metal raw materials are subjected to vacuum melting and directional continuous casting process to obtain a core wire rod with a diameter of 7 mm; the vacuum melting temperature is 1205°C; the directional continuous casting process conditions are: under argon atmosphere, pressure 0.04 Pa, speed 40 mm / min;

[0031] (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 7 cm, the roughly drawn core wire rod is medium drawn to a diameter of 0.9 cm, and the first intermediate annealing is performed. The wire obtained by the medium drawing is finely drawn to a diameter of 0.2 mm, and the second intermediate annealing is performed. The wire obtained by the fine drawing is ultra-finely drawn to 20 μm to obtain a silver alloy bonding wire; the conditions of the first intermediate annealing are: the effective length of the annealing furnace is 800 mm, the annealing temperature is 550° C., and the annealing rate is 115 m / min; the conditions of the second intermediate annealing are: the effective length of the annealing furnace is 800 mm, the annealing temperature is 430° C., and the annealing rate is 95 m / min;

[0032] (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix; the effective length of the annealing furnace is 800 mm, the annealing temperature is 520° C., and the annealing rate is 75 m / min;

[0033] (5) Curing and packaging: Cool the silver alloy bonding wire substrate to 25° C., and perform winding and packaging to obtain the silver alloy bonding wire for LED packaging.

[0034] Example 2

[0035] This embodiment provides a silver bonding wire for packaging, and the preparation method thereof comprises the following steps:

[0036] (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 1.4% gold, 2.8% palladium, 0.3% copper, 0.02% tin, 0.03% cerium, 0.03% ytterbium, 0.04% calcium, 0.003% chromium, 0.004% beryllium, 0.006% lanthanum, and the balance is silver;

[0037] (2) Melting and Casting: The metal raw materials are subjected to vacuum melting and directional continuous casting processes to obtain core wire rods with a diameter of 6 mm; the vacuum melting temperature is 1150°C; the directional continuous casting process conditions are: under argon atmosphere, pressure 0.02 Pa, speed 30 mm / min;

[0038] (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 6 cm, the roughly drawn core wire rod is medium drawn to a diameter of 0.8 cm, a first intermediate annealing is performed, the wire obtained by the medium drawing is finely drawn to a diameter of 0.1 mm, a second intermediate annealing is performed, and the wire obtained by the fine drawing is ultra-finely drawn to 20 μm to obtain a silver alloy bonding wire; the conditions of the first intermediate annealing are: the effective length of the annealing furnace is 700 mm, the annealing temperature is 520° C., and the annealing rate is 110 m / min; the conditions of the second intermediate annealing are: the effective length of the annealing furnace is 700 mm, the annealing temperature is 400° C., and the annealing rate is 90 m / min;

[0039] (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix; the effective length of the annealing furnace is 700 mm, the annealing temperature is 500° C., and the annealing rate is 70 m / min;

[0040] (5) Curing and packaging: Cool the silver alloy bonding wire substrate to 20° C., and perform winding and packaging to obtain the silver alloy bonding wire for LED packaging.

[0041] Example 3

[0042] This embodiment provides a silver bonding wire for packaging, and the preparation method thereof comprises the following steps:

[0043] (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 2.1% gold, 3.3% palladium, 0.7% copper, 0.06% tin, 0.05% cerium, 0.06% ytterbium, 0.08% calcium, 0.005% chromium, 0.009% beryllium, 0.01% lanthanum, and the balance is silver;

[0044] (2) Melting and Casting: The metal raw materials are subjected to vacuum melting and directional continuous casting process to obtain a core wire rod with a diameter of 8 mm; the vacuum melting temperature is 1350°C; the directional continuous casting process conditions are: under argon atmosphere, pressure 0.05 Pa, speed 50 mm / min;

[0045] (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 8 cm, the roughly drawn core wire rod is medium drawn to a diameter of 1.0 cm, and the first intermediate annealing is performed. The wire obtained by the medium drawing is finely drawn to a diameter of 0.3 mm, and the second intermediate annealing is performed. The wire obtained by the fine drawing is ultra-finely drawn to 20 μm to obtain a silver alloy bonding wire; the conditions of the first intermediate annealing are: the effective length of the annealing furnace is 900 mm, the annealing temperature is 570° C., and the annealing rate is 120 m / min; the conditions of the second intermediate annealing are: the effective length of the annealing furnace is 900 mm, the annealing temperature is 450° C., and the annealing rate is 100 m / min;

[0046] (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix; the effective length of the annealing furnace is 900 mm, the annealing temperature is 550° C., and the annealing rate is 80 m / min;

[0047] (5) Curing and packaging: Cool the silver alloy bonding wire substrate to 30° C., and perform winding and packaging to obtain the silver alloy bonding wire for LED packaging.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 is that gold and copper are not included.

[0050] The metal raw material includes the following components in mass fractions: 3.1% palladium, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 1 is that the added amounts of gold, palladium and copper are different.

[0053] The metal raw materials include the following components in mass fractions: 2.8% gold, 1.6% palladium, 1% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0054] Comparative Example 3

[0055] The difference between this comparative example and Example 1 is that the added amounts of gold, palladium and copper are different.

[0056] The metal raw materials include the following components in mass fractions: 1.2% gold, 4.0% palladium, 0.2% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 1 is that the amount of palladium added is different.

[0059] The metal raw materials include the following components in mass fractions: 1.8% gold, 2.1% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0060] Comparative Example 5

[0061] The difference between this comparative example and Example 1 is that the amount of palladium added is different.

[0062] The metal raw materials include the following components in mass fractions: 1.8% gold, 4.5% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0063] Comparative Example 6

[0064] The difference between this comparative example and Example 1 is that the amount of gold added is different.

[0065] The metal raw materials include the following components in mass fractions: 0.7% gold, 3.1% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0066] Comparative Example 7

[0067] The difference between this comparative example and Example 1 is that the amount of gold added is different.

[0068] The metal raw materials include the following components in mass fractions: 2.7% gold, 3.1% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0069] Comparative Example 8

[0070] The difference between this comparative example and Example 1 is that the amount of copper added is different.

[0071] The metal raw materials include the following components in mass fractions: 1.8% gold, 3.1% palladium, 0.1% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0072] Comparative Example 9

[0073] The difference between this comparative example and Example 1 is that the amount of copper added is different.

[0074] The metal raw materials include the following components in mass fractions: 1.8% gold, 3.1% palladium, 1.4% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver.

[0075] Comparative Example 10

[0076] The difference between this comparative example and Example 1 is that tin, cerium, ytterbium, calcium, chromium, beryllium and lanthanum are not added.

[0077] The metal raw material includes the following components in mass fractions: 1.8% gold, 3.1% palladium, 0.5% copper, and the balance is silver.

[0078] Comparative Example 11

[0079] The difference between this comparative example and Example 1 is that the added amounts of tin, cerium, ytterbium, calcium, chromium, beryllium and lanthanum are different.

[0080] The metal raw materials include the following components in mass fractions: 1.8% gold, 3.1% palladium, 0.5% copper, 0.01% tin, 0.06% cerium, 0.02% ytterbium, 0.09% calcium, 0.010% chromium, 0.003% beryllium, 0.005% lanthanum, and the balance is silver.

[0081] Comparative Example 12

[0082] The difference between this comparative example and Example 1 is that the metal raw materials are different.

[0083] The metal raw materials include the following components in mass fractions: 1.8% gold, 3.1% palladium, 0.5% copper, 0.03% tin, 0.04% platinum, 0.05% ytterbium, 0.06% indium, 0.004% chromium, 0.008% rhodium, 0.009% lanthanum, and the balance is silver.

[0084] Comparative Example 13

[0085] The difference between this comparative example and Example 1 is that no intermediate annealing is performed.

[0086] A silver bonding wire for packaging, the preparation method of which comprises the following steps:

[0087] (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 1.8% gold, 3.1% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver;

[0088] (2) Melting and Casting: The metal raw materials are subjected to vacuum melting and directional continuous casting process to obtain a core wire rod with a diameter of 7 mm; the vacuum melting temperature is 1205°C; the directional continuous casting process conditions are: under argon atmosphere, pressure 0.04 Pa, speed 40 mm / min;

[0089] (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 7 cm, the core wire rod after rough drawing is medium drawn to a diameter of 0.9 cm, the wire obtained by medium drawing is fine drawn to a diameter of 0.2 mm, and the wire obtained by fine drawing is ultra-fine drawn to 20 μm to obtain a silver alloy bonding wire;

[0090] (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix; the effective length of the annealing furnace is 800 mm, the annealing temperature is 520° C., and the annealing rate is 75 m / min;

[0091] (5) Curing and packaging: Cool the silver alloy bonding wire substrate to 25° C., and perform winding and packaging to obtain the silver alloy bonding wire for LED packaging.

[0092] Comparative Example 14

[0093] The difference between this comparative example and Example 1 is that the conditions of intermediate annealing and final annealing are different.

[0094] A silver bonding wire for packaging, the preparation method of which comprises the following steps:

[0095] (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 1.8% gold, 3.1% palladium, 0.5% copper, 0.03% tin, 0.04% cerium, 0.05% ytterbium, 0.06% calcium, 0.004% chromium, 0.008% beryllium, 0.009% lanthanum, and the balance is silver;

[0096] (2) Melting and Casting: The metal raw materials are subjected to vacuum melting and directional continuous casting process to obtain a core wire rod with a diameter of 7 mm; the vacuum melting temperature is 1205°C; the directional continuous casting process conditions are: under argon atmosphere, pressure 0.04 Pa, speed 40 mm / min;

[0097] (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 7 cm, the roughly drawn core wire rod is medium drawn to a diameter of 0.9 cm, and the first intermediate annealing is performed. The wire obtained by the medium drawing is finely drawn to a diameter of 0.2 mm, and the second intermediate annealing is performed. The wire obtained by the fine drawing is ultra-finely drawn to 20 μm to obtain a silver alloy bonding wire; the conditions of the first intermediate annealing are: the effective length of the annealing furnace is 800 mm, the annealing temperature is 500° C., and the annealing rate is 90 m / min; the conditions of the second intermediate annealing are: the effective length of the annealing furnace is 800 mm, the annealing temperature is 500° C., and the annealing rate is 90 m / min;

[0098] (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix; the effective length of the annealing furnace is 800 mm, the annealing temperature is 450° C., and the annealing rate is 90 m / min;

[0099] (5) Curing and packaging: Cool the silver alloy bonding wire substrate to 25° C., and perform winding and packaging to obtain the silver alloy bonding wire for LED packaging.

[0100] Performance Testing

[0101] 1. Reliability test: The silver bonding wires of Examples 1-3 and Comparative Examples 1-14 were used to encapsulate LED lamp beads in a conventional manner, under the following conditions: BSOB wire bonding, encapsulation silica gel: Dow Corning OE6650, FAB burning ball: EFO, current: 60mA; N2+H2 (gas flow rate: 0.5L / min). A reliability test was conducted to observe whether the LED lamps could still be lit, and the number of failed lamps was recorded.

[0102] (1) Thermal shock test: -40℃*30min-100℃*30min. After completing 100 cycles of thermal shock each time, observe whether the lamp can still light up and record the number of failed lamps (1000 samples per group).

[0103] (2) High temperature and high humidity test: 85℃ / 85%RH-1000hrs, and finally reflow soldering at 260℃ / 5sec, test 100 pieces. Record the number of failed lamps.

[0104] (3) High temperature storage test: 100℃, 1000hrs, and finally reflow soldering at 260℃ / 5sec, test 100 pieces. Record the number of failed lamps.

[0105] Table 1 Reliability test results

[0106]

[0107]

[0108] 2. Anti-sulfurization test: The silver bonding wires of Examples 1-3 and Comparative Examples 1-14 were used to encapsulate LED lamp beads. Ten samples were taken from each group and marked. Each group of LED lamp bead samples was placed in a 3L sealed container (sublimation sulfur concentration was 2g / L, constant temperature was 80°C). After sulfidation for 5 hours, each group of LED lamp bead samples was taken out, the light flux was tested, and the light decay was calculated. The calculation formula is: 5-hour light decay = [1-(5-hour light flux / 0-hour light flux)]*100%.

[0109] Table 2 Results of sulfur resistance test

[0110]

[0111]

[0112] 3. Referring to the testing standard YS / T 1105-2016, the mechanical properties of the silver alloy bonding wires for LED packaging of Examples 1-3 and Comparative Examples 1-14 were measured. -

[0113] Table 1 Mechanical properties test

[0114]

[0115]

[0116] The results show that the silver bonding wires prepared in Examples 1-3 have excellent comprehensive performance, but the comprehensive performance decreases to varying degrees by changing the composition, ratio and annealing conditions of the raw materials.

[0117] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silver bonding wire for packaging, characterized in that: The following steps are involved: (1) Weighing metal raw materials: the metal raw materials include the following components by mass fraction: 1.4-2.1% gold, 2.8-3.3% palladium, 0.3-0.7% copper, 0.02-0.06% tin, 0.03-0.05% cerium, 0.03-0.06% ytterbium, 0.04-0.08% calcium, 0.003-0.005% chromium, 0.004-0.009% beryllium, 0.006-0.01% lanthanum, and the balance is silver; (2) Melting and casting: The metal raw materials are subjected to vacuum melting and directional continuous casting process to obtain core wire rods with a diameter of 6-8 mm; (3) Wire drawing: the core wire rod is roughly drawn to a diameter of 6-8 cm, the core wire rod after rough drawing is medium drawn to a diameter of 0.8-1.0 cm, a first intermediate annealing is performed, the wire obtained by medium drawing is finely drawn to a diameter of 0.1-0.3 mm, a second intermediate annealing is performed, and the wire obtained by fine drawing is ultra-finely drawn to 20-40 μm to obtain a silver alloy bonding wire; (4) Final annealing: annealing the silver alloy bonding wire in a nitrogen atmosphere to obtain a silver alloy bonding wire matrix; (5) Solidification and packaging: The silver alloy bonding wire substrate is cooled to 20-30° C., and then wound and packaged to obtain the silver alloy bonding wire for packaging.

2. The method for preparing the silver bonding wire for packaging according to claim 1, characterized in that: The conditions of the first intermediate annealing are: the effective length of the annealing furnace is 700-900 mm, the annealing temperature is 520-570° C., and the annealing rate is 110-120 m / min.

3. The method for preparing the silver bonding wire for packaging according to claim 2, characterized in that: The conditions for the second intermediate annealing are: the effective length of the annealing furnace is 700-900 mm, the annealing temperature is 400-450° C., and the annealing rate is 90-100 m / min.

4. The method for preparing the silver bonding wire for packaging according to claim 3, characterized in that: In the step (4), the effective length of the annealing furnace is 700-900 mm, the annealing temperature is 500-550° C., and the annealing rate is 70-80 m / min.

5. The method for preparing the silver bonding wire for packaging according to claim 1, characterized in that: The temperature of vacuum melting in step (2) is 1150-1350°C.

6. The method for preparing the silver bonding wire for packaging according to claim 5, characterized in that: The conditions of the directional continuous casting process in step (2) are: under argon atmosphere, pressure 0.02-0.05 Pa, speed 30-50 mm / min.

7. Silver bonding wire for packaging obtained by the preparation method according to any one of claims 1 to 6.

8. The silver bonding wire for packaging according to claim 7, characterized in that: The diameter of the silver bonding wire for packaging is 20 μm, the breaking load is 10-11 cN, and the elongation is 10-11%.

9. The use of the silver bonding wire for packaging according to claim 7, characterized in that: The silver bonding wire is used for high-density packaging of micro LED devices.

Images