A bonding wire for encapsulation and a method of manufacturing and using the same

Abstract

The application belongs to the technical field of bonding wire processing, and particularly relates to a bonding wire which can be applied to high-end packaging bonding wire processing, and further discloses a preparation method and application of the bonding wire. The packaging bonding wire has gold as a main raw material, and a proper amount of Ca, La, Mg, Pd, Cu and Gd trace elements are added. By adjusting the different adding amounts of the trace elements, the mechanical properties of the bonding wire are effectively enhanced, the bonding wire has better tensile strength, higher elongation, a shorter heat-affected zone in the bonding application process, and can realize low-arc and long-span packaging, and has better application performance.

Description

Technical Field

[0001] This invention belongs to the field of bonding wire processing technology, and particularly relates to a bonding wire that can be applied to high-end packaging, and further discloses its preparation method and application. Background Technology

[0002] Bonding wires are one of the key basic materials in semiconductor packaging. They serve as the primary connection material between the chip and external circuits for signal transmission and current conduction. Based on their material composition, bonding wires can generally be classified into bonding alloy wires, bonding silver wires, bonding copper wires, bonding aluminum wires, and alloy wires. However, from the perspective of application stability and high reliability, bonding alloy wires have always been the preferred choice in the high-end packaging market.

[0003] Furthermore, with the increasingly harsh and diverse application scenarios for semiconductor components in recent years, the requirements for bonding wires to withstand mechanical stress and temperature effects during bonding have become increasingly stringent. Especially with the increasing complexity of electronic products, in addition to significant functional improvements, ultra-thinning and miniaturization have become mainstream development trends driven by cost considerations. Therefore, the development of high-reliability bonding wires with high strength and the ability to achieve long spans and low curvature has attracted considerable attention. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a bonding wire that can be applied to high-end packaging. The bonding wire has high breaking strength and long elongation, excellent mechanical properties, short heat-affected zone, and better application performance.

[0005] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned bonding alloy wire and its application.

[0006] To solve the above-mentioned technical problems, the present invention provides a bonding wire for encapsulation, wherein the bonding wire, based on its total amount, has a main Au content of 99.9-99.99 wt% and contains 60-180 ppm of trace elements.

[0007] The trace elements include a mixture of Ca, La, Mg, Pd, Cu and Gd.

[0008] Specifically, in the bonding wire used for encapsulation, the amounts of Ca, La, Mg, Pd, Cu and Gd added to the trace elements are 10-30 ppm, which are independent of each other.

[0009] Specifically, the bonding wire used for encapsulation, and the trace elements include:

[0010] The amount of Ca added is 15-25 ppm; and / or,

[0011] The amount of La added is 15-25 ppm; and / or,

[0012] The amount of Mg added is 10-15 ppm; and / or,

[0013] The amount of Pd added is 20-25 ppm; and / or,

[0014] The amount of Cu added is 10-15 ppm; and / or,

[0015] The amount of Gd added is 15-25 ppm.

[0016] The present invention also discloses a method for preparing the bonding wire for packaging, comprising the following steps:

[0017] (1) Intermediate alloy processing: The selected trace elements and a portion of the gold raw materials are mixed and smelted for the first time to obtain master alloys of different elements; the master alloys are then mixed with the gold raw materials and mixed and smelted for the second time to obtain intermediate alloys;

[0018] (2) Melting and casting process: According to the selected proportion, the intermediate alloy and the gold raw material are mixed and melted for the third time, and gold casting rods are obtained by casting process.

[0019] (3) Drawing process: The gold casting rod is drawn to obtain a bonding wire of the required diameter;

[0020] (4) Annealing process: The bonding wire is annealed;

[0021] (5) Rewinding process: The treated bonding wire is rewound to the bobbin to obtain the desired product.

[0022] Specifically, in the method for preparing the bonding wire for packaging, in step (1), the intermediate alloy processing step further includes the step of processing, rolling and cutting the master alloy to obtain a master alloy sheet, and / or the step of processing, rolling and cutting the intermediate alloy to obtain an intermediate alloy sheet;

[0023] Preferably, in the first mixing and melting step, the trace elements are controlled to account for 1-3 wt% of the amount of the master alloy;

[0024] Preferably, in the second mixing and melting step, the trace elements are controlled to account for 0.8-1.2 wt% of the amount of the intermediate alloy.

[0025] Specifically, in the method for preparing the bonding wire for packaging, in step (2), the third mixing and melting step is vacuum melting, preferably vacuum melting 1-3 times;

[0026] Preferably, the casting process includes a downward continuous casting process;

[0027] Preferably, the diameter of the gold casting rod is 6-10 mm.

[0028] Specifically, in the method for preparing the bonding wire for packaging, step (3) further includes a step of drawing and peeling the surface of the gold casting rod.

[0029] Preferably, the drawing process is a multi-stage drawing process.

[0030] Specifically, in the preparation method of the bonding wire for packaging, in step (4), the annealing temperature is 480-550℃, the winding speed is 60-80m / min, and the tension value is 0.8-1.7g.

[0031] Specifically, in the preparation method of the bonding wire for packaging, in step (5), the speed of the rewinding process is 600-700 rpm and the tension value is 1.0-1.5g.

[0032] The present invention also discloses the use of the bonding wire for packaging or the bonding wire for packaging prepared by the method for bonding leads.

[0033] The bonding wire for packaging described in this invention has a gold content of 99.9-99.99 wt%. By adding appropriate amounts of trace elements such as Ca, La, Mg, Pd, Cu, and Gd, and adjusting the different amounts of these trace elements, the mechanical properties of the bonding wire are effectively enhanced. This improves both the tensile strength and elongation, achieving high-strength, long-span bonding wire performance. Furthermore, during the ball bonding process, the heat-affected zone of the bonding wire is effectively shortened, meeting the low-radius packaging requirements. In addition, thermal shock testing shows that the reliability of the bonding wire is effectively improved, making it widely applicable in flash memory, high-end RF, and automotive packaging fields, especially laying a solid foundation for applications in harsh environments such as automotive products.

[0034] The bonding wire for packaging described in this invention fully considers factors such as the atomic radius, electronegativity, and solid solubility of each trace element during raw material optimization experiments. In particular, it focuses on investigating the influence of alloying elements on the processing and performance of the bonding wire. By utilizing the synergistic effect between trace elements, the mechanical properties are improved while the recrystallization temperature of the bonding wire is increased more effectively. A higher recrystallization temperature can ensure that the metal material is less prone to grain regrowth and recombination at high temperatures, thus ensuring the stability of the metal wire. It also allows for a shorter heat-affected zone during high-temperature bonding, thereby achieving low-arc packaging.

[0035] The bonding wire for packaging described in this invention incorporates Ca (Ca) in high-purity gold, which alters the gold's crystal lattice, enabling solid solution strengthening and precipitation strengthening, thereby increasing the gold's strength. The added La (La) element inhibits recrystallization nucleation and growth, and works in conjunction with Mg (Mg) to refine the grain structure, enhancing the mechanical properties of the finished bonding wire. Furthermore, La effectively improves sphericity during the bonding process. The addition of Pd (Pl) forms an infinitely miscible solid solution with gold, primarily functioning as solid solution strengthening, increasing the gold's strength while ensuring its corrosion resistance and heat resistance. Cu (Cu) is completely dissolved in gold, also functioning as solid solution strengthening, macroscopically improving the bonding wire's strength. Gd (Gypsum) segregates at grain boundaries, pinning them and preventing grain growth, thus increasing strength. Macroscopically, it raises the gold's recrystallization temperature, shortening the heat-affected zone of the bonding wire.

[0036] The high-end packaging bonding wire provided by this invention, through exploration and experimentation with bonding wire formulations, has achieved a high-reliability bonding wire with significantly improved strength and a short heat-affected zone by adding a small amount of multiple elements while ensuring the high purity (99.999 wt%) of the bonding wire raw materials. This improves the tensile strength of the bonding wire while achieving a longer elongation. Compared with most commercially available bonding wires, it has better tensile strength and higher elongation. During bonding applications, it has a shorter heat-affected zone, enabling low-arc, long-span packaging and superior application performance. The bonding wire described in this invention can be applied to high-end packaging fields, including but not limited to flash memory, high-end RF, and automotive products.

[0037] The present invention provides a method for processing high-end packaging bonding wires, including the preparation of an intermediate alloy, a casting process, a drawing process, an annealing process, a rewinding process, and subsequent finished product packaging; wherein,

[0038] The processing steps of the intermediate alloy involve mixing and melting the aforementioned trace elements with gold, followed by machining, rolling, cleaning, and cutting into master alloy sheets. The master alloy sheets with different elements are then mixed with gold and melted again to form an intermediate alloy ingot. This ingot is then machined, rolled, cleaned, and cut into intermediate alloy sheets. Intermediate alloys prepared in this way effectively reduce element segregation, improve the uniformity of alloy content, and effectively remove impurities introduced during the manufacturing process through multiple machining and cleaning passes.

[0039] The step of melting and casting into gold rods involves mixing intermediate alloy sheets of different elements with 5N gold and vacuum melting them 1-3 times, and then obtaining gold rods with uniform composition and a diameter of 8mm through a continuous pull casting process.

[0040] The drawing process not only involves drawing the gold casting rods, but also using a surface peeling device during the drawing process to remove defective and dirty surface layers, resulting in a smooth and scratch-free gold wire blank; further, the surface-treated wire is drawn in multiple stages until it reaches the required diameter of the bonding wire.

[0041] The annealing process involves annealing the bonded alloy wire drawn to the required diameter under certain tension, temperature, and speed to eliminate hardening and restore plasticity.

[0042] The rewinding process involves winding the annealed bonding wire to a fixed length at a certain tension and speed onto the finished spool.

[0043] The method for preparing the bonding alloy wire described in this invention effectively reduces element segregation, improves the uniformity of alloy content, and effectively removes impurities introduced during the manufacturing process by adding machining, rolling, and cleaning steps during the intermediate alloy production process, thus ensuring batch-to-batch stability of the bonding alloy wire products.

[0044] The method for preparing bonding alloy wire described in this invention, by adding a peeling device during the drawing process, can remove surface defects of the gold casting blank to the greatest extent, such as subcutaneous pores, inclusions, mechanical damage, etc., to obtain a smooth and consistent surface quality, improve machinability, and make the breaking force and elongation of the bonding alloy wire product more stable. Attached Figure Description

[0045] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0046] Figure 1 This is a flowchart illustrating the processing of the bonding wire described in this invention.

[0047] Figure 2 These are comparative images of the appearance of the gold casting rods prepared in Example 1 and Comparative Example 1 of the present invention.

[0048] Figure 3 These are comparative images of the appearance of the intermediate alloy ingots prepared according to Embodiment 1 and Comparative Example 2 of the present invention.

[0049] Figure 4 The images show a comparison of the appearance of the gold casting rods prepared in Example 1 and Comparative Example 3 of this invention. Detailed Implementation

[0050] The following provides specific embodiments of the present invention to further illustrate the structure of the present invention.

[0051] In the following embodiments of the present invention, the purity of the raw materials used includes: gold with a purity of 99.999 wt%, commercially available calcium (Ca) with a purity of 99.9 wt%, commercially available lanthanum (La) with a purity of 99.99 wt%, commercially available magnesium (Mg) with a purity of 99.99 wt%, commercially available palladium (Pd) with a purity of 99.95 wt%, commercially available copper (Cu) with a purity of 99.99 wt%, and commercially available gadolinium (Gd) with a purity of 99.99 wt%.

[0052] Example 1

[0053] The bonding wire described in this embodiment is composed of the following metal materials in the following weight ratios: Ca 25ppm, La 20ppm, Mg 15ppm, Pd 22ppm, Cu 10ppm, Gd 15ppm, with the remainder being Au with a purity of 99.999wt%.

[0054] like Figure 1 The processing flow chart shown illustrates the preparation method of the bonding alloy wire described in this embodiment, which includes the following steps: intermediate alloy processing, casting process, drawing process, annealing process, and rewinding process.

[0055] (1) Intermediate alloy processing

[0056] a. Weigh out appropriate amounts of various trace element raw materials and gold raw materials separately, and set aside;

[0057] b. Melting Au-X master alloys: Determine the melting temperature of each trace element master alloy based on the binary phase diagrams of Au-Ca, Au-La, Au-Mg, Au-Pd, Au-Cu, and Au-Gd.

[0058] c. Loading: Weigh high-purity gold raw material (5N) and put it into a high-purity graphite crucible. Weigh a certain amount of the above-mentioned trace elements, wrap them with an appropriate amount of gold sheet, and put them into the same crucible. In this step, the trace elements are controlled to account for 2% of the mass content of the master alloy.

[0059] d. Vacuum melting and processing: After loading, place the above raw materials into a high-frequency induction alloy furnace, cover the furnace, and evacuate. Under vacuum conditions (vacuum degree: 5.0 × 10⁻⁶), the process continues. -3 Pa) is heated to 1150℃ to completely melt the added trace elements and gold raw materials. The corresponding temperature is maintained for 15 minutes for smelting. Then, it is stirred thoroughly 20 times and left to stand for 20 minutes to obtain a master alloy ingot with uniform composition. Heating is stopped, and the molten alloy is cooled with the furnace. After it has cooled completely, the master alloy is taken out and machined → rolled → cleaned and cut to finally make sheet master alloy for use.

[0060] e. Melting Au-X master alloy: Take the above-mentioned cut master alloy sheets and add high-purity gold raw materials into a high-purity graphite crucible. In this step, control the mass content of trace elements added to each element master alloy to be 1% of the master alloy. The vacuum melting process and processing are the same as the master alloy. Finally, the sheet master alloy is obtained for later use.

[0061] (2) Melting and casting process

[0062] According to the element content of the bonding wire design, and based on the proportion of trace elements in each intermediate alloy, select an appropriate amount of intermediate alloy sheets and place them together in a small, suspended crucible inside the furnace according to the required mass. Then, place high-purity gold raw material (5N grade) into a large crucible. During this step, control the total mass of the intermediate alloy and gold raw material to be 10 kg. After completing the loading and sealing of the furnace, perform vacuuming until the high vacuum degree reaches ≤5.0 × 10⁻⁶. -2 Pa, then heated to 1200℃ and refined for 45 minutes. The vacuum process was stopped while simultaneously introducing high-purity argon gas. Under this gas protection, the small crucible was opened, the intermediate alloy sheet was added, and stirring was performed 15 times at a frequency of 5 seconds per stirring point. The argon purging was then stopped and a vacuum was drawn until the vacuum level reached ≤5.0×10⁻⁶. -2 Pa, let stand for 20 minutes, stir 15 times, then repeat the standing-stirring cycle 4 times, and finally let stand for 5 minutes. Stop the vacuuming and simultaneously purge with high-purity argon gas, and continuously pull and cast an 8mm casting rod at a speed of 80mm / min;

[0063] The long casting rod is cut into shorter rods and placed back into a high-purity graphite crucible for a second casting process. The parameters are basically the same as the first casting: after charging and sealing the furnace, a vacuum is drawn until the high vacuum degree reaches ≤5.0×10⁻⁶. -2 The solution is heated to 1200℃ and refined for 20 minutes. It is then stirred 15 times at a frequency of 5 seconds per cycle, allowed to stand for 10 minutes, stirred 15 times, and this process of standing and stirring is repeated 3 times. Finally, it is allowed to stand for 5 minutes. While stopping the vacuum process, high-purity argon gas is introduced, and an 8mm diameter ingot is produced by continuous downward casting at a speed of 80mm / min. The final product is an 8mm diameter ingot with a smooth surface and uniform composition.

[0064] (3) Drawing process

[0065] The gold casting rod with a diameter of 8 mm obtained above was subjected to a large drawing process. During this process, the surface was treated by a peeling die with a diameter of 3.06 mm, and the rod was drawn down to a diameter of 1.51 mm at a drawing speed of 40 m / min.

[0066] Intermediate drawing: 1.51mm diameter drawn to 0.07963mm, drawing speed is 120m / min;

[0067] Fine drawing: The diameter of 79.63μm is drawn to the required wire diameter at a drawing speed of 240m / min.

[0068] (4) Annealing process

[0069] Annealing was performed at an annealing temperature of 520℃, a tension of 1.2g, and a take-up speed of 70m / min.

[0070] (5) Rewinding process

[0071] Using a winding machine, the gold wire is wound to the required length at 650 rpm and a tension of 1.2g. The wound gold wire is then placed in a plastic box, labeled, and packaged in a cardboard box.

[0072] Example 2

[0073] The bonding wire described in this embodiment is composed of the following metal materials in the following weight ratios: Ca 15ppm, La 25ppm, Mg 15ppm, Pd 20ppm, Cu 10ppm, Gd 25ppm, with the remainder being gold with a purity of 99.999wt%.

[0074] The preparation method of the bonding wire described in this embodiment is the same as that in Embodiment 1.

[0075] Example 3

[0076] The bonding wire described in this embodiment is composed of the following metal materials in the following weight ratios: Ca 25ppm, La 15ppm, Mg 10ppm, Pd 25ppm, Cu 15ppm, Gd 20ppm, with the remainder being gold with a purity of 99.999wt%.

[0077] The preparation method of the bonding wire described in this embodiment is the same as that in Embodiment 1.

[0078] Example 4

[0079] The bonding wire described in this embodiment is composed of the following metal materials in the following weight ratios: Ca 10ppm, La 30ppm, Mg 10ppm, Pd 30ppm, Cu 10ppm, Gd 30ppm, with the remainder being Au with a purity of 99.999wt%.

[0080] like Figure 1 The processing flow chart shown illustrates the preparation method of the bonding alloy wire described in this embodiment, which includes the following steps: intermediate alloy processing, casting process, drawing process, annealing process, and rewinding process.

[0081] (1) Intermediate alloy processing

[0082] a. Weigh out appropriate amounts of various trace element raw materials and gold raw materials separately, and set aside;

[0083] b. Melting Au-X master alloys: Determine the melting temperature of each trace element master alloy based on the binary phase diagrams of Au-Ca, Au-La, Au-Mg, Au-Pd, Au-Cu, and Au-Gd.

[0084] c. Loading: Weigh high-purity gold raw material (5N) and put it into a high-purity graphite crucible. Weigh a certain amount of the above-mentioned trace elements, wrap them with an appropriate amount of gold sheet, and put them into the same crucible. In this step, the trace elements are controlled to account for 1% of the mass content of the master alloy.

[0085] d. Vacuum melting and processing: After loading, place the above raw materials into a high-frequency induction alloy furnace, cover the furnace, and evacuate. Under vacuum conditions (vacuum degree: 5.0 × 10⁻⁶), the process continues. -3 Pa) Heat to 1100℃ to completely melt the added trace elements and gold raw materials, maintain the corresponding temperature for 20 minutes for smelting, then stir thoroughly 15 times, let stand for 10 minutes to obtain a master alloy ingot with uniform composition; stop heating, let the molten alloy cool with the furnace, and after it has cooled completely, take out the master alloy, and perform machining → rolling → cleaning and cutting to finally make sheet master alloy for use.

[0086] e. Melting Au-X master alloy: Take the above-mentioned cut master alloy sheets and add high-purity gold raw materials into a high-purity graphite crucible. In this step, control the mass content of trace elements added to the master alloy of each element to be 0.8% of the master alloy. The vacuum melting process and processing are the same as the master alloy. Finally, the sheet master alloy is obtained for later use.

[0087] (2) Melting and casting process

[0088] According to the element content of the bonding wire design, and based on the proportion of trace elements in each intermediate alloy, select an appropriate amount of intermediate alloy sheets and place them into a small crucible suspended inside the furnace according to the required mass. Then, place high-purity gold raw material (5N grade) into a large crucible. In this step, control the total mass of the intermediate alloy and gold raw material to be 10 kg. After completing the loading and sealing of the furnace, perform vacuuming until the high vacuum degree reaches ≤5.0×10⁻⁶. -2 Pa, then heated to 1200℃ and refined for 45 minutes. The vacuum process was stopped while simultaneously introducing high-purity argon gas. Under this gas protection, the small crucible was opened, the intermediate alloy sheet was added, and stirring was performed 15 times at a frequency of 5 seconds per stirring point. The argon purging was then stopped and a vacuum was drawn until the vacuum level reached ≤5.0×10⁻⁶. -2 Pa, let stand for 20 minutes, stir 15 times, then repeat the standing-stirring cycle 4 times, and finally let stand for 5 minutes. Stop the vacuuming and simultaneously purge with high-purity argon gas, and continuously pull and cast an 8mm casting rod at a speed of 80mm / min;

[0089] The long casting rod is cut into shorter rods and placed back into a high-purity graphite crucible for a second casting process. The parameters are basically the same as the first casting: after charging and sealing the furnace, a vacuum is drawn until the high vacuum degree reaches ≤5.0×10⁻⁶. -2 The solution is heated to 1200℃ and refined for 20 minutes. It is then stirred 15 times at a frequency of 5 seconds per cycle, allowed to stand for 10 minutes, stirred 15 times, and this process of standing and stirring is repeated 3 times. Finally, it is allowed to stand for 5 minutes. While stopping the vacuum process, high-purity argon gas is introduced, and an 8mm diameter ingot is produced by continuous downward casting at a speed of 80mm / min. The final product is an 8mm diameter ingot with a smooth surface and uniform composition.

[0090] (3) Drawing process

[0091] The gold casting rod with a diameter of 8 mm obtained above was subjected to a large drawing process. During this process, the surface was treated by a peeling die with a diameter of 3.06 mm, and the rod was drawn down to a diameter of 1.51 mm at a drawing speed of 20 m / min.

[0092] Intermediate drawing: 1.51mm diameter drawn to 0.07963mm, drawing speed is 60m / min;

[0093] Fine drawing: The diameter of 79.63μm is drawn to the required wire diameter at a drawing speed of 180m / min.

[0094] (4) Annealing process

[0095] Annealing was performed at an annealing temperature of 480℃, a tension of 0.8g, and a take-up speed of 60m / min.

[0096] (5) Rewinding process

[0097] Using a winding machine, the gold wire is wound to the required length at 600 rpm and a tension of 1.0g. The wound gold wire is then placed in a plastic packaging box, labeled, and then packaged in a cardboard box.

[0098] Example 5

[0099] The bonding wire described in this embodiment is composed of the following metal materials in the following weight ratios: Ca 30ppm, La 10ppm, Mg 30ppm, Pd 10ppm, Cu 30ppm, Gd 10ppm, with the remainder being Au with a purity of 99.999wt%.

[0100] like Figure 1 The processing flow chart shown illustrates the preparation method of the bonding alloy wire described in this embodiment, which includes the following steps: intermediate alloy processing, casting process, drawing process, annealing process, and rewinding process.

[0101] (1) Intermediate alloy processing

[0102] a. Weigh out appropriate amounts of various trace element raw materials and gold raw materials separately, and set aside;

[0103] b. Melting Au-X master alloys: Determine the melting temperature of each trace element master alloy based on the binary phase diagrams of Au-Ca, Au-La, Au-Mg, Au-Pd, Au-Cu, and Au-Gd.

[0104] c. Loading: Weigh high-purity gold raw material (5N) and put it into a high-purity graphite crucible. Weigh a certain amount of the above-mentioned trace elements, wrap them with an appropriate amount of gold sheet, and put them into the same crucible. In this step, the trace elements are controlled to account for 3% of the mass content of the master alloy.

[0105] d. Vacuum melting and processing: After loading, place the above raw materials into a high-frequency induction alloy furnace, cover the furnace, and evacuate. Under vacuum conditions (vacuum degree: 5.0 × 10⁻⁶), the process continues. -3 Pa) Heat to 1200℃ to completely melt the added trace elements and gold raw materials, maintain the corresponding temperature for 10 minutes for smelting, then stir thoroughly 20 times, let stand for 30 minutes to obtain a master alloy ingot with uniform composition; stop heating, let the molten alloy cool with the furnace, and after it has cooled completely, take out the master alloy, and perform machining → rolling → cleaning and cutting to finally make sheet master alloy for use.

[0106] e. Melting Au-X master alloy: Take the above-mentioned cut master alloy sheets and add high-purity gold raw materials into a high-purity graphite crucible. In this step, control the mass content of trace elements added to the master alloy of each element to be 1.2% of the master alloy. The vacuum melting process and processing are the same as the master alloy. Finally, the sheet master alloy is obtained for later use.

[0107] (2) Melting and casting process

[0108] According to the element content of the bonding wire design, and based on the proportion of trace elements in each intermediate alloy, select an appropriate amount of intermediate alloy sheets and place them together in a small, suspended crucible inside the furnace according to the required mass. Then, place high-purity gold raw material (5N grade) into a large crucible. During this step, control the total mass of the intermediate alloy and gold raw material to be 10 kg. After completing the loading and sealing of the furnace, perform vacuuming until the high vacuum degree reaches ≤5.0 × 10⁻⁶. -2 Pa, then heated to 1200℃ and refined for 45 minutes. The vacuum process was stopped while simultaneously introducing high-purity argon gas. Under this gas protection, the small crucible was opened, the intermediate alloy sheet was added, and stirring was performed 15 times at a frequency of 5 seconds per stirring point. The argon purging was then stopped and a vacuum was drawn until the vacuum level reached ≤5.0×10⁻⁶. -2Pa, let stand for 20 minutes, stir 15 times, then repeat the standing-stirring cycle 4 times, and finally let stand for 5 minutes. Stop the vacuuming and simultaneously purge with high-purity argon gas, and continuously pull and cast an 8mm casting rod at a speed of 80mm / min;

[0109] The long casting rod is cut into shorter rods and placed back into a high-purity graphite crucible for a second casting process. The parameters are basically the same as the first casting: after charging and sealing the furnace, a vacuum is drawn until the high vacuum degree reaches ≤5.0×10⁻⁶. -2 The solution is heated to 1200℃ and refined for 20 minutes. It is then stirred 15 times at a frequency of 5 seconds per cycle, allowed to stand for 10 minutes, stirred 15 times, and this process of standing and stirring is repeated 3 times. Finally, it is allowed to stand for 5 minutes. While stopping the vacuum process, high-purity argon gas is introduced, and an 8mm diameter ingot is produced by continuous downward casting at a speed of 80mm / min. The final product is an 8mm diameter ingot with a smooth surface and uniform composition.

[0110] (3) Drawing process

[0111] The gold casting rod with a diameter of 8 mm obtained above was subjected to a large drawing process. During this process, the surface was treated by a peeling die with a diameter of 3.06 mm, and the rod was drawn down to a diameter of 1.51 mm at a drawing speed of 60 m / min.

[0112] Intermediate drawing: 1.51mm diameter drawn to 0.07963mm, drawing speed is 180m / min;

[0113] Fine drawing: The diameter of 79.63μm is drawn to the required wire diameter at a drawing speed of 300m / min.

[0114] (4) Annealing process

[0115] Annealing was performed at an annealing temperature of 550℃, a tension of 1.7g, and a take-up speed of 80m / min.

[0116] (5) Rewinding process

[0117] Using a winding machine, the gold wire is wound to the required length at 700 rpm and a tension of 1.5g. The wound gold wire is then placed in a plastic box, labeled, and packaged in a cardboard box.

[0118] Comparative Example 1

[0119] The raw material composition of the bonding wire described in this comparative example is the same as that in Example 1. The only difference is that in step (2), the casting process adopts an intermittent casting method instead of the continuous downward casting operation used in this invention.

[0120] Comparative Example 2

[0121] The raw material composition of the bonding wire described in this comparative example is the same as that in Example 1. The only difference is that in step (1), the intermediate alloy processing process of the present invention is not used, that is, the master alloy melting, machining and cleaning operations are not carried out, but the intermediate alloy is directly prepared into sheet form by rolling and cutting.

[0122] Comparative Example 3

[0123] The raw material composition of the bonding wire described in this comparative example is the same as that in Example 1. The only difference is that in step (3), the drawing process does not involve large-scale skin stripping.

[0124] Comparative Example 4

[0125] The preparation method of the bonding wire described in this comparative example is the same as that in Example 2, except that the trace elements do not contain lanthanum (La).

[0126] Comparative Example 5

[0127] The preparation method of the bonding wire described in this comparative example is the same as that in Example 2, except that the trace elements do not contain gadolinium (Gd).

[0128] Comparative Example 6

[0129] The raw material composition and preparation method of the bonding wire described in this comparative example are the same as those in Example 3, except that the content of lanthanum (La) added to the trace elements is 7 ppm.

[0130] Comparative Example 7

[0131] The raw material composition and preparation method of the bonding wire described in this comparative example are the same as those in Example 3, except that the content of gadolinium (Gd) added in the trace elements is 7 ppm.

[0132] Experimental Example

[0133] 1. Bonding wire performance testing

[0134] The bonding wires processed in Examples 1-3 and Comparative Examples 1-7 were tested for parameters such as breaking force, elongation, uniaxial drawing length, recrystallization temperature, heat-affected zone, and thermal shock reliability. The testing methods and standards for each parameter are as follows:

[0135] 1) Tensile strength and elongation test: Refer to GB / T10573-2020 "Tension Test Method for Non-ferrous Metal Wires";

[0136] 2) Single-axis drawing length test method: The bonding wire is drawn from 0.025mm to 0.020mm through 6 passes. There is no upper limit on the length of a single axis. The length is compared until the wire breaks naturally during the drawing process. The length of the bonding wire drawn from each axis is 0.020mm.

[0137] 3) Recrystallization temperature: The recrystallization temperature of the bonding wire was determined by differential scanning calorimetry (DSC). The sample was about 30 mg, the heating temperature range was 50-500℃, and the heating rate was 40℃ / min.

[0138] 4) Length of heat-affected zone: The length of the heat-affected zone (HAZ) was determined by measuring the average grain size of different regions after the bonding wire was sintered using the intercept method in the national standard GB / T6394--2002 "Method for Determination of Average Grain Size of Metals".

[0139] 5) Reliability testing: Before the test, the electrical parameters and appearance of the sample are tested and inspected to ensure that the electrical parameters are qualified and the appearance is normal; at low temperature -55℃ (+0, -10) and high temperature +125℃ (+15, -0), 30 minutes is one cycle (15 minutes for each of the high and low temperatures), and the switching time does not exceed 30 seconds. The electrical performance and appearance are tested once every 100 cycles.

[0140] The performance test results are shown in Table 1 below.

[0141] Table 1. Test results of bonding alloy wire performance

[0142]

[0143] As shown in Table 1 above, the bonding wire prepared using the element ratio of the present invention can achieve a single-axis drawing length of over 7000m, which is nearly 4.5 times longer than the existing processes of Comparative Examples 1-3. This greatly reduces the difficulty of micro-drawing the bonding wire, lowers the micro-drawing breakage rate, and significantly improves reliability. This proves that the bonding wire of the present invention is more suitable for packaging automotive products and can withstand harsher environmental changes.

[0144] In addition, extensive experiments conducted in this invention have revealed that the addition of element La can effectively improve the mechanical properties of the bonding wire, and the addition of element Gd can effectively increase the recrystallization temperature of the bonding wire, thereby achieving a shorter heat-affected zone and making it more suitable for applications in products with low-arc packaging requirements.

[0145] In summary, the bonding wire of this invention, through the scientific selection and proportioning of trace elements and after extensive experimentation, achieves high tensile strength while maintaining a long elongation, a short heat-affected zone, and high reliability. While meeting the performance requirements of ordinary wire bonding, it can also adapt to the packaging needs of low-arc, long-span applications. It can be applied in electronic packaging products such as automotive components, requiring long lifespan and resistance to harsh environments, demonstrating significant advantages.

[0146] 2. Appearance Evaluation

[0147] Figure 2This is a comparison image of the surface of the gold ingots obtained by continuous pull casting in Example 1 and intermittent pull casting in Comparative Example 1. From... Figure 2 The results show that the gold rods obtained by the continuous casting process of this invention have a smoother and cleaner surface, and the gold wires produced can be processed to a diameter of 15μm. In contrast, the gold rods obtained by the down-draw intermittent casting process in Comparative Example 1 have bamboo-like defects on their surface, and the gold wires produced can only be processed to a maximum diameter of 18μm. In the processing of wires smaller than 18μm, wire breakage is quite serious.

[0148] Figure 3 The images show a comparison of the appearance of the intermediate alloy ingots prepared in Example 1 and Comparative Example 2. It can be seen that the bonding wire preparation method of the present invention, by incorporating machining, rolling, and cleaning steps during the intermediate alloy production process, effectively reduces elemental segregation, improves the uniformity of alloy content, effectively removes impurities introduced during the production process, and ensures batch-to-batch stability of the bonding wire products. The intermediate alloy ingots treated with the above process have a smooth and bright surface, free of impurities, and can be cut into gold flakes for subsequent use.

[0149] Figure 4 The images show a comparison of the appearance of the gold casting rods prepared in Example 1 and Comparative Example 3. It can be seen that the bonding wire preparation method of the present invention, by incorporating a peeling device during the drawing process, can remove surface defects of the gold casting blank to the greatest extent, such as subcutaneous pores, inclusions, and mechanical damage, thereby obtaining a smooth and consistent surface quality, improving machinability, and making the breaking force and elongation of the bonding wire product more stable. It can be seen that the surface of the gold casting rod after peeling is smoother and cleaner.

[0150] 3. Product uniformity

[0151] This experimental example is used to investigate the effect of the "intermediate alloy processing" step on the uniformity of the bonding wire product. The uniform alloy casting rod is the basis for subsequent processing and also the cornerstone for the high mechanical properties of the finished bonding wire.

[0152] Table 2 below shows the results of determining the total content of trace elements added to the head, middle and tail of the gold casting rods in Examples 1-3 and Comparative Example 2 without using the above-mentioned intermediate alloy preparation technology.

[0153] Table 2. Elemental Distribution of Gold Casting Rods

[0154]

[0155] The test results above show that in Comparative Example 2, which did not use the intermediate alloy preparation technology described in this patent, the content of added trace elements in the head, middle, and tail of the gold casting rod was uneven and highly inconsistent. In contrast, Examples 1-3, which used an intermediate alloy that underwent multiple melting, machining, cleaning, and trimming processes, resulted in a more uniform element content across the head, middle, and tail when the gold casting rod was made.

[0156] As can be seen, the optimized intermediate alloy preparation process of this invention can make the elemental composition of the resulting gold casting rod more uniform. The preparation of the master alloy effectively avoids deviations caused by the weighing process of trace elements. During multiple melting processes, through stirring, cleaning, and cutting, the trace elements are further dispersed, enhancing the uniformity of trace element addition, effectively reducing element segregation problems, and improving the uniformity of trace elements in the gold casting rod. In addition, multiple machining and cleaning processes can effectively remove harmful impurities introduced during the manufacturing process. The method for preparing the bonding alloy wire described in this invention effectively ensures the application performance of the bonding alloy wire.

[0157] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A bonding wire for encapsulation, characterized in that, The bonding wire contains 60-180 ppm of trace elements by weight; the trace element composition is Ca, La, Mg, Pd, Cu and Gd, with the remainder being Au with a purity of 99.999 wt%; the preparation method of the bonding wire for encapsulation includes the following steps: (1) Intermediate alloy processing: The selected trace elements and a portion of the gold raw materials are mixed and smelted for the first time to obtain master alloys of different elements; the master alloys are then mixed and smelted with a portion of the gold raw materials for the second time to obtain intermediate alloys; (2) Melting and casting process: According to the selected proportion, the intermediate alloy and the remaining gold raw materials are mixed and melted for the third time, and gold casting rods are obtained by casting process; (3) Drawing process: The gold casting rod is drawn to obtain a bonding wire of the required diameter; (4) Annealing process: The bonding wire is annealed; (5) Rewinding process: The treated bonding wire is rewound to the bobbin to obtain the desired result.

2. The bonding wire for encapsulation according to claim 1, characterized in that, The amounts of Ca, La, Mg, Pd, Cu and Gd added are 10-30 ppm, which are independent of each other.

3. The bonding wire for encapsulation according to claim 1, characterized in that, Among the trace elements: The amount of Ca added is 15-25 ppm; and / or, The amount of La added is 15-25 ppm; and / or, The amount of Mg added is 10-15 ppm; and / or, The amount of Pd added is 20-25 ppm; and / or, The amount of Cu added is 10-15 ppm; and / or, The amount of Gd added is 15-25 ppm.

4. The bonding wire for encapsulation according to claim 1, characterized in that, In step (1), the intermediate alloy processing step further includes the step of processing, rolling and cutting the master alloy to obtain a master alloy sheet, and / or the step of processing, rolling and cutting the intermediate alloy to obtain an intermediate alloy sheet.

5. The bonding wire for encapsulation according to claim 1, characterized in that, In the first mixing and melting step, the trace elements are controlled to account for 1-3 wt% of the amount of the master alloy.

6. The bonding wire for encapsulation according to claim 1, characterized in that, In the second mixing and melting step, the trace elements are controlled to account for 0.8-1.2 wt% of the amount of the intermediate alloy.

7. The bonding wire for encapsulation according to claim 1, characterized in that, In step (2), the third mixing and melting step is vacuum melting.

8. The bonding wire for encapsulation according to claim 7, characterized in that, In step (2), the third mixing and melting step is to perform vacuum melting 1-3 times.

9. The bonding wire for encapsulation according to claim 1, characterized in that, The casting process includes a downward continuous casting process.

10. The bonding wire for encapsulation according to claim 1, characterized in that, The diameter of the gold-cast rod is 6-10 mm.

11. The bonding wire for encapsulation according to claim 1, characterized in that, In step (3), the drawing process further includes a step of drawing and peeling the surface of the gold casting rod.

12. The bonding wire for encapsulation according to claim 1, characterized in that, The drawing process involves multiple drawing steps.

13. The bonding wire for encapsulation according to claim 1, characterized in that, In step (4), the annealing temperature is 480-550℃, the winding speed is 60-80m / min, and the tension value is 0.8-1.7g.

14. The bonding wire for encapsulation according to claim 1, characterized in that, In step (5), the speed of the rewinding process is 600-700 rpm and the tension value is 1.0-1.5g.

15. Use of the bonding wire for packaging according to any one of claims 1-14 for the preparation of bonding leads.

Images