A bonding wire having high wear resistance and high reliability and a method for manufacturing the same

Abstract

A high-wear-resistant and high-reliability bonding wire is characterized by its chemical composition and mass percentages as follows: magnesium 0.0010-0.0025 wt.%, palladium 0.0010-0.0025 wt.%, lanthanum 0.0005-0.0025 wt.%, yttrium 0.0005-0.0030 wt.%, with the balance being gold. This invention also provides a method for preparing the aforementioned high-wear-resistant and high-reliability bonding wire. The bonding wire of this invention exhibits structural stability at high temperatures, high strength, good wear resistance, and good oxidation resistance. It is suitable for gold wire ball bonding processes, and during bonding, it is less prone to adhesion to the bonding tip, effectively reducing the tip wear rate, extending tip lifespan, and improving product reliability.

Description

Technical Field

[0001] This invention relates to the field of bonding wire technology for semiconductor packaging, and specifically to a bonding wire with high wear resistance and high reliability, and its preparation method. Background Technology

[0002] In the field of semiconductor packaging, bonding wires are key materials for achieving electrical connections between internal circuitry and external leads, and their performance plays a crucial role in packaging quality and the reliability of electronic products. Traditional bonding alloy wires (Au>99.99%) were widely used in early semiconductor packaging due to their good conductivity and chemical stability.

[0003] However, with the rapid development of semiconductor technology, the performance requirements for bonding wires are becoming increasingly stringent, and the limitations of traditional alloy bonding wires (pure gold bonding wires) are gradually becoming apparent. Traditional alloy bonding wires suffer from low hardness and poor wear resistance. In gold ball bonding processes, the bonding wires need to be repeatedly passed through ceramic nozzles for welding operations. Due to the insufficient hardness of pure gold bonding wires, the ceramic nozzles suffer severe wear during frequent friction. This not only significantly shortens the lifespan of the ceramic nozzles, increasing production costs, but may also affect the precision and stability of the welding process, thereby reducing the product yield.

[0004] To improve the performance of pure gold bonding wires, existing technologies attempt to increase their hardness by adding elements such as Ag and Cu. However, these methods have many drawbacks: when the Ag content exceeds 3%, the conductivity of the bonding wire decreases significantly, which is undoubtedly a serious problem for semiconductor packaging, which has extremely high conductivity requirements; although Cu can improve hardness, its chemical properties are highly reactive and it is easily oxidized during the soldering process. The resulting oxides can affect the reliability of the soldering, leading to problems such as cold solder joints and desoldering; in addition, the addition of Ag and Cu can cause the bonding wire grains to become coarser, increasing surface roughness and further aggravating the wear of the ceramic tip, while also affecting the connection performance between the bonding wire and the chip and external leads.

[0005] As semiconductor chips evolve towards smaller sizes and higher integration, the requirements for bonding wires are becoming increasingly stringent. Not only are higher hardness and wear resistance required to withstand more frequent and precise soldering operations, but they also need to maintain good conductivity and bonding reliability while improving performance. Therefore, the development of a new type of bonding wire is urgently needed. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a high-wear-resistant and high-reliability bonding wire and its preparation method. This bonding wire exhibits structural stability at high temperatures, high strength, good wear resistance, and good oxidation resistance. It is suitable for gold wire ball bonding processes, and during bonding, it does not easily adhere to the ceramic tip, effectively reducing the wear rate of the ceramic tip, extending its service life, and improving product reliability. The technical solution adopted is as follows:

[0007] A bonding wire with high wear resistance and high reliability is characterized by the following chemical composition and mass percentage: magnesium 0.0010-0.0025 wt.%, palladium 0.0010-0.0025 wt.%, lanthanum 0.0005-0.0025 wt.%, yttrium 0.0005-0.0030 wt.%, with the balance being gold.

[0008] In the preferred embodiment, the lanthanum content in the aforementioned bonding wire is 0.0010-0.0020 wt.%.

[0009] In the preferred embodiment, the yttrium content in the aforementioned bonding wire is 0.0005-0.0020 wt.%.

[0010] In the preferred embodiment, the diameter of the bonding wire is 15-30 μm.

[0011] This invention also provides a method for preparing the above-mentioned high wear resistance and high reliability bonding wire, characterized by comprising the following steps:

[0012] (1) By weight, the following raw materials are provided: magnesium 0.0010-0.0025 wt.%, palladium 0.0010-0.0025 wt.%, lanthanum 0.0005-0.0025 wt.%, yttrium 0.0005-0.0030 wt.%, with the balance being gold;

[0013] Then, the various raw materials are vacuum melted and cast to obtain alloy rods;

[0014] (2) The alloy rods are drawn and annealed to obtain gold alloy wires with a diameter of 15-30 μm;

[0015] (3) Finished product shaping heat treatment: Gold alloy wires with a diameter of 15-30μm are annealed online in a tube annealing furnace. At the end of the annealing process, the gold alloy wires are cooled by immersion coolant and then dried to obtain the required high wear resistance and high reliability bonding alloy wires.

[0016] In the preferred step (1), magnesium, palladium, lanthanum, and yttrium are added in the form of master alloys. First, the Mg-Pd-Au master alloy, La-Au master alloy, and Y-Au master alloy are melted separately, and then each master alloy and pure gold are prepared according to the required proportions of each component in step (1); or, the Mg-Au master alloy, Pd-Au master alloy, La-Au master alloy, and Y-Au master alloy are melted separately, and then each master alloy and pure gold are prepared according to the required proportions of each component in step (1). The above master alloys are prepared using vacuum melting and casting processes. For example, adding 5g of magnesium and 5g of palladium to 990g of pure gold, fully melting in a vacuum induction melting furnace, and then casting yields 1000g of Mg-Pd-Au master alloy; adding 5g of lanthanum to 995g of pure gold, fully melting in a vacuum induction melting furnace, and then casting yields 1000g of La-Au master alloy; adding 5g of yttrium to 995g of pure gold, fully melting in a vacuum induction melting furnace, and then casting yields 1000g of Y-Au master alloy.

[0017] In preferred step (1), a vacuum induction melting furnace is used to melt various raw materials under a vacuum of 10^-2 Pa, and the superheat of the melt is controlled at 50-150℃. High-frequency induction heating is used to fully melt the materials and ensure that the alloy composition is uniformly distributed.

[0018] In the preferred step (1), the casting adopts a directional continuous casting process: after the alloy liquid is melted, argon gas is introduced into the furnace cavity of the vacuum induction melting furnace, and alloy bars are drawn into them through a graphite mold (preferably with a diameter of 8 mm). During the continuous casting process, the casting speed (1-3 mm / s) and cooling water temperature (19-25℃) should be controlled to ensure the quality and dimensional accuracy of the bars.

[0019] In preferred step (2), the process of drawing and annealing the alloy bar includes the following steps:

[0020] (2-1) Rough drawing: Through multiple drawing passes, the alloy bar is drawn into a gold alloy wire with a diameter of 1 mm. The deformation of each drawing pass is controlled at 15-20%.

[0021] (2-2) Homogenization annealing: Gold alloy wire with a diameter of 1 mm is annealed at 600-650℃ for 1-3 hours (preferably 2 hours), and nitrogen protection is used during the annealing process;

[0022] (2-3) Small drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 1.0 mm is drawn to a diameter of 0.1 mm, and the deformation of each drawing pass is controlled at 10-15%;

[0023] (2-4) Intermediate annealing: The gold alloy wire with a diameter of 0.1 mm is annealed online in a tubular annealing furnace. The online annealing speed of the tubular annealing furnace is controlled at 30-90 m / min, and the annealing temperature is 400-630℃.

[0024] (2-5) Fine drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 0.1 mm is drawn to a finished wire diameter of 15-30 μm, and the deformation of each drawing pass is controlled at 8-12%.

[0025] By employing a three-stage temperature-controlled drawing process combined with homogenization annealing and intermediate annealing, a uniform nanocrystalline structure can be obtained. During the drawing process, by controlling the amount of drawing deformation and temperature at different stages, the internal microstructure of the material is gradually refined and homogenized, forming a nanocrystalline structure and improving the overall performance of the material.

[0026] Step (2-1) involves rough drawing to initially reduce the diameter of the bar, preparing for subsequent small and fine drawing.

[0027] Step (2-2) Homogenization annealing effectively improves the compositional uniformity within pure gold wire. Through homogenization, atoms diffuse sufficiently, resulting in a more homogeneous composition within the gold alloy wire. In gold alloy wires containing additive elements such as Mg, Pd, La, and Y, homogenization annealing ensures these elements are uniformly distributed within the gold matrix, preventing localized enrichment or deficiency. Uniformly distributed elements can more effectively exert their respective effects. For example, the solid solution strengthening effect of Mg and Pd uniformly increases the wire's hardness, while the grain refinement and grain boundary purification effects of La and Y are consistently present throughout the wire, thereby improving the overall mechanical properties and stability of the bonded alloy wire. Homogenization annealing also eliminates residual processing stress, restores the material's plasticity, and facilitates subsequent drawing processes.

[0028] Steps (2-4) involve intermediate annealing to eliminate work hardening of the material and improve its plasticity, while controlling the elongation at 10-20%.

[0029] In preferred step (3), the online annealing speed in the tubular annealing furnace is controlled at 50-120 m / min (preferably 90 m / min), and the annealing temperature is 400-590℃. The tensile strength and elongation of the wire are achieved by controlling the annealing temperature and speed, with the elongation controlled at 2-6%.

[0030] In steps (2-4) and (3), the length of the tubular annealing furnace is usually 60-100cm.

[0031] In the preferred embodiment, a surface treatment step (2b) is performed between step (2) and step (3), specifically as follows:

[0032] The gold alloy wire obtained in step (2) is placed in an ultrasonic cleaner and the surface of the wire is cleaned with water as the cleaning solution. Then, it is placed in a 0.01% benzotriazole ethanol solution for passivation treatment.

[0033] Alternatively, the gold alloy wire obtained in step (2) can be passivated by placing it in a benzotriazole ethanol solution with a mass percentage concentration of 0.01%.

[0034] Passivation treatment forms a dense protective film on the wire surface, further reducing the surface adhesion of the wire and decreasing the adhesion between the ceramic tip and the bonding wire.

[0035] The bonding wire of this invention incorporates trace elements magnesium (Mg), palladium (Pd), lanthanum (La), and yttrium (Y) within a specified range. These trace elements work synergistically, with lanthanum and yttrium refining grains and purifying grain boundaries. Combined with the solid solution strengthening effects of magnesium and palladium, this comprehensively improves the bonding wire's strength, hardness, conductivity, and oxidation resistance. The wire exhibits higher strength, structural stability at high temperatures, and is less prone to oxide buildup. During the ball-forming process, it is less likely to cause contamination and adhesion on the ceramic tip surface, effectively reducing the tip wear rate and extending tip life. This meets the high-performance requirements of semiconductor packaging bonding wires, improving device yield and reliability. Specific details are as follows:

[0036] (1) Pd-Mg synergistic strengthening: There is a synergistic strengthening effect between Mg and Pd. Both are dissolved in the Au lattice, and the resulting strengthening effect is better than the sum of the effects of adding them alone. This significantly improves the hardness and wear resistance of the bonding wire. By strengthening with trace amounts of Pd and Mg through solid solution, the hardness and wear resistance of the material can be improved while ensuring conductivity. Pd and Mg atoms form a solid solution in the gold lattice, which hinders dislocation movement, thereby improving the hardness and strength of the material, reducing the wear of the bonding wire on the ceramic tip, and extending the service life of the ceramic tip. At the same time, due to the small amount added, the impact on conductivity is minimal.

[0037] Magnesium and palladium have different atomic radii than gold. In pure gold, they dissolve into the gold lattice as solute atoms, forming interstitial or substitutional solid solutions. Magnesium atoms, with smaller radii than gold, enter the interstitial spaces of the gold lattice, resulting in interstitial solid solution strengthening. Palladium atoms, with radii similar to gold, dissolve into the lattice via substitution, resulting in substitutional solid solution strengthening and forming intermetallic compounds such as Au-Mg, Au-Pd, or Au-Mg-Pd. These intermetallic compounds exhibit high hardness and brittleness. Their dispersed distribution within the gold matrix hinders dislocation movement, requiring additional energy and making material deformation more difficult, thus increasing the hardness of the bonding wires.

[0038] (2) Rare Earth Microalloying: The combined use of two rare earth elements, La and Y, refines the grains and purifies the grain boundaries. The trace solid solution of rare earth elements in the gold alloy forms solid solution strengthening, and the surface diffusion enrichment and segregation of rare earth elements on the surface reduce the surface energy and adhesion energy of the gold alloy, thereby reducing the surface friction coefficient and improving the service life of the ceramic nozzle. The refined grains make the material properties more uniform, and the purification of grain boundaries reduces the impact of impurities and defects on performance.

[0039] The combined effect of lanthanum and yttrium in bonded alloy wires significantly refines the grain size. During alloy solidification and crystallization, lanthanum and yttrium preferentially segregate at grain boundaries and nuclei. The presence of lanthanum and yttrium atoms hinders grain growth, resulting in a finer, more uniform grain structure in the bonded alloy wire. This refined grain structure increases the area of ​​grain boundaries, which, as defect regions in the crystal structure, impede dislocation movement. Under stress and deformation, dislocations find it difficult to cross the numerous fine grain boundaries, thereby improving the strength and toughness of the bonded alloy wire.

[0040] Furthermore, the combined addition of these two rare earth elements enhances grain boundary purification. In bonding wires, impurities often accumulate at grain boundaries, reducing their strength and impacting performance. Lanthanum and yttrium react chemically with impurities at grain boundaries to form stable compounds, reducing impurity segregation and purifying the grain boundary environment. At high temperatures, the purified grain boundaries effectively inhibit atomic diffusion, reducing performance degradation caused by hot starts. This ensures the reliability of bonding wires in semiconductor packaging and use, and lowers the risk of poor soldering and device failure due to grain boundary issues.

[0041] The diffusion enrichment and segregation of lanthanum and yttrium on the surface of the bonding wire reduce the surface energy and adhesion energy of the gold alloy. The reduced surface energy makes the bonding wire surface more stable, decreasing the activity of surface atoms and reducing the likelihood of reactions with external substances. The reduced adhesion energy decreases the adhesion between the bonding wire and contact materials such as the ceramic nozzle and chip electrodes during bonding, lowering the surface friction coefficient. In gold ball bonding, this effect significantly reduces friction and wear between the bonding wire and the ceramic nozzle, extending the nozzle's lifespan.

[0042] (3) Mg enhances high-temperature oxidation resistance, and Pd's stability strengthens the overall oxidation resistance of the bonding wire, reducing oxide contamination and wear on the ceramic tip. La and Y refine grains and purify grain boundaries, working together with Mg and Pd to maintain a stable structure and performance of the bonding wire at high temperatures, further reducing abnormal wear on the ceramic tip caused by changes in the bonding wire's properties. These effects work together to comprehensively reduce friction and wear between the bonding wire and the ceramic tip. In long-term operation of the gold wire ball bonding process, the wear rate of the ceramic tip is effectively reduced, resulting in a single ceramic tip lifespan of up to 800,000 points, which is more than 30% higher than that of traditional products.

[0043] In summary, the bonding wire of this invention exhibits structural stability, high strength, good wear resistance, and good oxidation resistance at high temperatures. It is suitable for gold wire ball bonding processes and does not easily adhere to the bonding tip during bonding, effectively reducing the wear rate of the tip, extending the lifespan of the tip, and improving product reliability. Detailed Implementation

[0044] Experimental Example 1:

[0045] In this experimental example, the preparation method of the bonding wire includes the following steps:

[0046] (1) By weight, the following raw materials are prepared: 0.0005-0.0030 wt.% magnesium (the amount of magnesium used in the six tests was 0.0005 wt.%, 0.0010 wt.%, 0.0015 wt.%, 0.0020 wt.%, 0.0025 wt.%, 0.0030 wt.%), 0.0005-0.0030 wt.% palladium (the amount of palladium used in the six tests was 0.0005 wt.%, 0.0010 wt.%, 0.0015 wt.%, 0.0020 wt.%, 0.0025 wt.%, 0.0030 wt.%), with the balance being gold;

[0047] Then, the various raw materials are vacuum melted and cast to obtain alloy rods;

[0048] (2) The alloy rod is drawn and annealed to obtain a gold alloy wire with a diameter of 20 μm;

[0049] (3) Finished product shaping heat treatment: The gold alloy wire with a diameter of 20 μm is annealed online in a tube annealing furnace (the online annealing speed of the tube annealing furnace is controlled at 90 m / min, the annealing temperature is 500℃; the length of the tube annealing furnace is 100 cm). The gold alloy wire is cooled by immersion coolant at the end of the annealing process, and then dried to obtain the required bonding alloy wire.

[0050] The process of drawing and annealing the alloy bar in step (2) includes the following steps:

[0051] (2-1) Rough drawing: Through multiple drawing passes, the alloy bar is drawn into a gold alloy wire with a diameter of 1 mm. The deformation of each drawing pass is controlled within 20%.

[0052] (2-2) Homogenization annealing: Gold alloy wire with a diameter of 1 mm was annealed at 620℃ for 2 hours, and nitrogen protection was used during the annealing process;

[0053] (2-3) Small drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 1.0 mm is drawn to a diameter of 0.1 mm, and the deformation of each drawing pass is controlled within 15%;

[0054] (2-4) Intermediate annealing: Gold alloy wire with a diameter of 0.1 mm is annealed online in a tubular annealing furnace. The online annealing speed of the tubular annealing furnace is controlled at 50 m / min (the length of the tubular annealing furnace is 100 cm), and the annealing temperature is 480℃.

[0055] (2-5) Fine drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 0.1 mm is drawn to a finished wire diameter of 20 μm, and the deformation of each drawing pass is controlled within 10%.

[0056] The tensile properties (TS: tensile strength, EL: elongation) and elongation capacity of the bonded wires (Au-Mg-Pd microalloyed bonded wires) obtained from the six tests in Example 1 were tested at room temperature. The test results are shown in Table 1.

[0057] Table 1:

[0058]

[0059] Table 1 shows that adding trace amounts of Pd and Mg can increase the tensile strength of the wire and significantly improve its elongation. However, when the Pd and Mg content exceeds 0.0025 wt.%, the elongation decreases significantly (embrittlement effect), and the elongation also decreases significantly. Analysis of the fracture morphology collected on-site indicates that the wire exhibits brittle fracture, and Mg was detected at the fracture surface. Regarding the roundness of the crimped solder balls, when Pd and Mg content is below 0.0010 wt.%, the roundness is poor; when Pd and Mg content is ≥0.0010 wt.%, the roundness is relatively good. Increasing the amount of magnesium and palladium from 0.0005 wt.% to 0.0030 wt.% did not significantly improve the lifespan of the ceramic nozzle.

[0060] Example 2: In this example, Au-Pd-Mg microalloy (Au+0.0020Pd+0.0020Mg) with advantages of high tensile strength and good wire elongation ability from Table 1 was selected. In step (2), different annealing processes were carried out to study its effect on wire elongation ability.

[0061] Process route 1 is as follows: the smelted busbar does not undergo any heat treatment during the intermediate wire stretching process until the finished wire diameter is 20um.

[0062] Process route 2 is as follows: After the smelted busbar is stretched to 1.0 mm, it is subjected to homogenization annealing. The annealing conditions are annealing the gold alloy wire with a diameter of 1 mm at 620℃ for 2 hours. The annealing process is protected by nitrogen. After that, the wire is stretched to a diameter of 20 μm.

[0063] Process route 3 is the drawing and annealing process route used in step (2) of test example 1.

[0064] Table 2:

[0065]

[0066] As shown in Table 2, when homogenization annealing is used during the wire stretching process, the wire stretching capability is improved; when intermediate annealing (stress relief) is introduced during the wire stretching process after a certain processing rate and work hardening occurs, the wire stretching capability is further improved.

[0067] Experimental Example 3:

[0068] In this experimental example, Au-Pd-Mg microalloys (Au+0.0020Pd+0.0020Mg) with advantages of high tensile strength and good elongation ability as shown in Table 1 were selected, and Au-Pd-Mg-La microalloys were manufactured by adding La.

[0069] In this experimental example, the preparation method of the bonding wire includes the following steps:

[0070] (1) By weight, the following raw materials are prepared: magnesium 0.0020 wt.%, palladium 0.0020 wt.%, lanthanum 0.0005-0.0050 wt.% (the amount of lanthanum used in the six tests was 0.0005 wt.%, 0.0010 wt.%, 0.0020 wt.%, 0.0025 wt.%, 0.0030 wt.%, and 0.0050 wt.%, respectively), with the balance being gold;

[0071] Then, the various raw materials are vacuum melted and cast to obtain alloy rods;

[0072] (2) The alloy rod is drawn and annealed to obtain a gold alloy wire with a diameter of 20 μm;

[0073] (3) Finished product shaping heat treatment: The gold alloy wire with a diameter of 20 μm is annealed online in a tube annealing furnace (the online annealing speed of the tube annealing furnace is controlled at 90 m / min, the annealing temperature is 500℃; the length of the tube annealing furnace is 100 cm). The gold alloy wire is cooled by immersion coolant at the end of the annealing process, and then dried to obtain the required bonding alloy wire.

[0074] The process and conditions for drawing and annealing the alloy rod in step (2) of Experimental Example 3 are the same as those in Experimental Example 1.

[0075] The tensile properties (TS: tensile strength, EL: elongation) and elongation capacity of the bonded wires (Au-Mg-Pd-La microalloyed bonded wires) obtained from the six tests in Example 3 were tested at room temperature. The test results are shown in Table 3.

[0076] Table 3:

[0077]

[0078] Table 3 shows that in Au-Pd-Mg-La microalloyed wire, the elongation did not change significantly, while the strength increased with the increase of La content. La increases the effective nucleation sites, resulting in a tendency for the grain size to decrease. However, when the La content is ≥0.0025wt.%, the wire's stretchability and elongation also tend to decrease.

[0079] The Au-Pd-Mg-La microalloyed wire (wire diameter: 20μm) was tested on an ASM wire bonding machine. The ceramic tip used was Sanhuan CR5-28H0-CF2090-CD. Continuous bonding was performed using the Normal bonding method. A brand new ceramic tip was used for each bonding. The number of bonding points of a single ceramic tip from the start of use until obvious wear or contamination (such as ceramic tip orifice enlargement exceeding the specified value, decreased bonding accuracy, etc.) was recorded, as shown in Table 4.

[0080] Table 4:

[0081]

[0082] Table 4 shows that in Au-Pd-Mg-La microalloyed wire, the addition of La is beneficial to the roundness of the solder balls during crimping, with a content of 0.0010-0.0030 wt.% being relatively good. When the content exceeds 0.0030 wt.%, the spherical shape becomes off-center. Meanwhile, the lifespan of the ceramic tip also varies with the amount of La added: a La content of 0.0010-0.0025 wt.% significantly improves the lifespan of the ceramic tip; however, a La content less than 0.0010 wt.% or more than 0.0025 wt.% does not significantly improve the lifespan of the ceramic tip.

[0083] Example 1: In this example, the preparation method of the high wear resistance and high reliability bonding wire includes the following steps:

[0084] (1) By weight, the following raw materials are prepared: magnesium 0.0020 wt.%, palladium 0.0020 wt.%, lanthanum 0.0020 wt.%, yttrium (the amount of yttrium used in the five tests was 0.0005 wt.%, 0.0010 wt.%, 0.0020 wt.%, 0.0030 wt.%, and 0.0050 wt.%), with the balance being gold;

[0085] Then, the various raw materials are vacuum melted and cast to obtain alloy rods;

[0086] (2) The alloy rod is drawn and annealed to obtain a gold alloy wire with a diameter of 20 μm;

[0087] (3) Finished product shaping heat treatment: The gold alloy wire with a diameter of 20 μm is annealed online in a tube annealing furnace (the online annealing speed of the tube annealing furnace is controlled at 90 m / min, the annealing temperature is 500℃; the length of the tube annealing furnace is 100 cm). The gold alloy wire is cooled by immersion coolant at the end of the annealing process, and then dried to obtain the required bonding alloy wire.

[0088] The process and conditions for drawing and annealing the alloy rod in step (2) of Example 1 are the same as those in Experiment 1.

[0089] The tensile properties (TS: tensile strength, EL: elongation) and elongation capacity of the bonded wires (Au-Pd-Mg-La-Y microalloyed bonded wires) obtained in the five tests in Example 1 were tested at room temperature. The test results are shown in Table 5.

[0090] Table 5:

[0091]

[0092] Table 5 shows that in Au-Pd-Mg-La-Y microalloyed bonding wires, the elongation did not change significantly, while the strength increased with increasing Y content. However, when the Y content was ≥0.0030 wt.%, the wire's stretchability decreased, and the elongation also tended to decrease.

[0093] The Au-Pd-Mg-La-Y microalloyed bonding wire (wire diameter: 20μm) was tested on an ASM wire bonding machine. The ceramic tip used was Sanhuan CR5-28H0-CF2090-CD. Continuous bonding was performed using the Normal bonding method. A brand new ceramic tip was used for each bonding. The number of bonding points of a single ceramic tip was recorded from the start of use until obvious wear or contamination (such as ceramic tip orifice enlargement exceeding the specified value, decreased bonding accuracy, etc.) was observed.

[0094] The observed roundness of the crimped solder balls and the lifespan of the ceramic tips are shown in Table 6, and the corresponding first-solder ball push force and second-solder bonding force are shown in Table 7. Meanwhile, reliability tests HTST (150℃) and TS (-40~125℃) were performed on the packaged chip, and the results are shown in Table 7.

[0095] Table 6:

[0096]

[0097] Table 6 shows that in Au-Pd-Mg-La-Y microalloyed bonding wires, the addition of Y is beneficial to the roundness of the solder balls. A content of 0.0005-0.0030 wt.% is relatively good, and a content of 0.0005-0.0020 wt.% is optimal. When the content exceeds 0.0030 wt.%, the spherical shape becomes off-center. Meanwhile, the lifespan of the ceramic tip also varies with the amount of Y added: a content of 0.0005-0.0030 wt.% has an effect on improving the lifespan of the ceramic tip; and a Y content of 0.0010-0.0020 wt.% has the best effect on improving the lifespan of the ceramic tip.

[0098] Table 7:

[0099]

[0100] Table 7 shows that in Au-Pd-Mg-La-Y microalloyed wire, the addition of Y is beneficial to improving the push force of the first weld ball and the bonding strength of the second weld. A Y content of 0.0005-0.0030 wt.% is relatively good, with the optimal content being 0.0005-0.0020 wt.%. However, when the Y content is ≥0.0030 wt.%, both the push force of the first weld ball and the bonding strength of the second weld tend to decrease. This is related to the possibility that at high temperatures, a higher Y content may cause ceramic tip contamination, leading to poor ball formation and bonding strength in the second weld.

[0101] Table 8:

[0102]

[0103] Table 8 shows that in Au-Pd-Mg-La-Y microalloyed wire, the addition of Y element has a significant advantage over Au 99.99% pure gold wire in reliability testing. A Y content of 0.0005-0.0030 wt.% is relatively good, with the best being 0.0005-0.0020 wt.%. When the Y content is ≥0.0030 wt.%, the high-temperature impact resistance tends to decrease. This is related to the possibility of ceramic tip contamination at high temperatures due to higher Y content, leading to poor balling and secondary weld bonding.

[0104] The test results in Tables 1-8 show that the gold alloy wire made by the present invention, which contains appropriate amounts of trace elements Pd, Mg, La, and Y (Mg 0.0010-0.0025wt.%; Palladium 0.0010-0.0025wt.%; Lanthanum 0.0005-0.0025wt.%, especially 0.0010-0.0020wt.%; Yttrium 0.0005-0.0030wt.%, especially 0.0005-0.0020wt.%), has the following beneficial effects: excellent wire stretching ability, excellent mechanical properties, and excellent wear resistance of the ceramic tip, as well as good reliability. While improving performance, it reduces the cost of consumable materials for ceramic tips for customers, thereby reducing costs.

[0105] The test methods used in the above experimental examples and embodiments are as follows:

[0106] 1. TS (Tension Value): The maximum tensile force that a wire of a certain length can withstand when stretched at a certain speed until it breaks.

[0107] Test method: The Instron 3343 tensile testing machine was used, and the test was conducted in accordance with the method of GB / T 10573. The gauge length was 100 mm and the tensile speed was 10 mm / min.

[0108] 2. EL (Elongation): The percentage of the original length of a wire when it is stretched to break at a certain speed.

[0109] Test method: The Instron 3343 tensile testing machine was used, and the test was conducted in accordance with the method of GB / T 10573. The gauge length was 100 mm and the tensile speed was 10 mm / min.

[0110] 3. Wire stretching ability: The ability of a wire to stretch without breaking during the thinning process. It is usually measured by the average length obtained when the wire is stretched to a certain diameter and a certain number of wires.

[0111] Wire stretching capability evaluation standard: Taking the stretching to 0.8mil (20μm) as an example, the typical stretching is 50km, with an average length of >4000 meters per shaft.

[0112] Excellent: Average length > 6000 meters per axle.

[0113] Acceptable length: 3000~6000 meters per axle.

[0114] Poor: Average length < 3000 meters per axle.

[0115] 4. Roundness of the solder ball: In IC or LED packaging, the roundness of the ball after it has been heated by FAB and then hot-pressed onto the chip or bracket.

[0116] Evaluation criteria for the roundness of crimped solder balls: The ratio deviation of the diameter-to-length ratio of the X-axis and Y-axis is less than ±3%.

[0117] Excellent: Abnormal percentage <0.5%

[0118] Acceptable: Anomaly rate 0.5-1.0%

[0119] Poor: Abnormal percentage > 1.0%

[0120] 5. Ceramic Tip Life Evaluation Standard: There is no fixed standard for ceramic tip life. Different packaging methods, wire materials, and ceramic tips typically result in different lifespans. This invention uses a normal soldering method, soldering the tip onto an aluminum layer to calculate the number of solder joints. Based on customer usage, the ceramic tip life standard is 600,000 joints.

[0121] Excellent: Over 600,000 points

[0122] Acceptance: 300,000-600,000 points

[0123] Poor: Below 300,000 points

[0124] 6. First Solder Ball Push Force: In IC or LED packaging, a force is applied to the solder ball in a specific direction after the first soldering (first soldering) to test the bonding strength between the solder ball and the soldering surface. The magnitude of this force is the first solder ball push force.

[0125] Evaluation standard for welding ball thrust: Refer to JEDEC JESD22 - B117 standard.

[0126] 7. Second Solder Bond Strength: In IC or LED packaging, after the second soldering (second soldering), the connection strength between the second solder joint and the object being soldered (such as chip pins, substrate pads, etc.). This is typically measured by applying a certain external force to the solder joint using a tensile testing device, determining the magnitude of the force required to cause the solder joint to separate or break.

[0127] Evaluation standard for the bonding strength of two welds: Refer to JEDEC JESD22 - B117 standard.

[0128] 8. Reliability Testing

[0129] (1) HTST (150℃):

[0130] Test method: Place the wire-bonded product in a high-temperature storage device, keep the temperature stable at 150℃, and bake continuously. Observe the conductivity of the test product every 200 hours.

[0131] Qualification standard: >1000 hours.

[0132] (2) TS (-40~125℃):

[0133] Test method: Place the wire-bonded product into a temperature cycling test device, maintain it at a low temperature of -45℃ for 30 minutes, and then maintain it at a high temperature of 125℃ for 30 minutes, which is one cycle; repeat the operation to test the conductivity of the product.

[0134] Qualification standard: >800 rounds.

Claims

1. A bonding wire with high wear resistance and high reliability, characterized in that... Its chemical composition and mass percentage are as follows: magnesium 0.0010-0.0025 wt.%, palladium 0.0010-0.0025 wt.%, lanthanum 0.0005-0.0025 wt.%, yttrium 0.0005-0.0030 wt.%, with the balance being gold; The method for preparing the high-wear-resistant and high-reliability bonding wire includes the following steps: (1) By weight, the following raw materials are provided: magnesium 0.0010-0.0025 wt.%, palladium 0.0010-0.0025 wt.%, lanthanum 0.0005-0.0025 wt.%, yttrium 0.0005-0.0030 wt.%, with the balance being gold; Then, the various raw materials are vacuum melted and cast to obtain alloy rods; (2) The alloy rods are drawn and annealed to obtain gold alloy wires with a diameter of 15-30 μm; The process of drawing and annealing the alloy bar in step (2) includes the following steps: (2-1) Rough drawing: Through multiple drawing passes, the alloy bar is drawn into a gold alloy wire with a diameter of 1 mm. The deformation of each drawing pass is controlled at 15-20%. (2-2) Homogenization annealing: anneal gold alloy wire with a diameter of 1 mm at 600-650℃ for 1-3 hours, with nitrogen protection during the annealing process; (2-3) Small drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 1.0 mm is drawn to a diameter of 0.1 mm, and the deformation of each drawing pass is controlled at 10-15%; (2-4) Intermediate annealing: The gold alloy wire with a diameter of 0.1 mm is annealed online in a tubular annealing furnace. The online annealing speed of the tubular annealing furnace is controlled at 30-90 m / min, and the annealing temperature is 400-630℃. (2-5) Fine drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 0.1 mm is drawn to a finished wire diameter of 15-30 μm, and the deformation of each drawing pass is controlled at 8-12%; (3) Finished product shaping heat treatment: Gold alloy wires with a diameter of 15-30μm are annealed online in a tube annealing furnace. At the end of the annealing process, the gold alloy wires are cooled by immersion coolant and then dried to obtain the required high wear resistance and high reliability bonding alloy wires.

2. The high wear resistance and high reliability bonding wire according to claim 1, characterized in that: The lanthanum content in the bonding wire is 0.0010-0.0020 wt.%.

3. The high wear resistance and high reliability bonding wire according to claim 1, characterized in that: The yttrium content in the bonding wire is 0.0005-0.0020 wt.%.

4. The high wear resistance and high reliability bonding wire according to claim 1, characterized in that: The diameter of the bonding alloy wire is 15-30 μm.

5. The method for preparing the high wear resistance and high reliability bonding wire according to claim 1, characterized in that... Includes the following steps: (1) By weight, the following raw materials are provided: magnesium 0.0010-0.0025 wt.%, palladium 0.0010-0.0025 wt.%, lanthanum 0.0005-0.0025 wt.%, yttrium 0.0005-0.0030 wt.%, with the balance being gold; Then, the various raw materials are vacuum melted and cast to obtain alloy rods; (2) The alloy rods are drawn and annealed to obtain gold alloy wires with a diameter of 15-30 μm; The process of drawing and annealing the alloy bar in step (2) includes the following steps: (2-1) Rough drawing: Through multiple drawing passes, the alloy bar is drawn into a gold alloy wire with a diameter of 1 mm. The deformation of each drawing pass is controlled at 15-20%. (2-2) Homogenization annealing: anneal gold alloy wire with a diameter of 1 mm at 600-650℃ for 1-3 hours, with nitrogen protection during the annealing process; (2-3) Small drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 1.0 mm is drawn to a diameter of 0.1 mm, and the deformation of each drawing pass is controlled at 10-15%; (2-4) Intermediate annealing: The gold alloy wire with a diameter of 0.1 mm is annealed online in a tubular annealing furnace. The online annealing speed of the tubular annealing furnace is controlled at 30-90 m / min, and the annealing temperature is 400-630℃. (2-5) Fine drawing: Through multiple drawing passes, the gold alloy wire with a diameter of 0.1 mm is drawn to a finished wire diameter of 15-30 μm, and the deformation of each drawing pass is controlled at 8-12%; (3) Finished product shaping heat treatment: Gold alloy wires with a diameter of 15-30μm are annealed online in a tube annealing furnace. At the end of the annealing process, the gold alloy wires are cooled by immersion coolant and then dried to obtain the required high wear resistance and high reliability bonding alloy wires.

6. The method for preparing high wear-resistant and high-reliability bonding wire according to claim 5, characterized in that: In step (1), a vacuum induction melting furnace is used to melt various raw materials under a vacuum of 10^-2 Pa, and the superheat of the melt is controlled at 50-150℃.

7. The method for preparing high wear resistance and high reliability bonding wire according to claim 5, characterized in that: In step (1), the casting adopts a directional continuous casting process: after the alloy liquid is melted, argon gas is introduced into the furnace cavity of the vacuum induction melting furnace, and alloy bars are drawn and cast through a graphite mold.

8. The method for preparing high wear resistance and high reliability bonding wire according to claim 5, characterized in that: In step (3), the online annealing speed of the tubular annealing furnace is controlled at 50-120 m / min, and the annealing temperature is 400-590℃; In steps (2-4) and (3), the length of the tubular annealing furnace is 60-100cm.

9. The method for preparing high wear-resistant and high-reliability bonding wire according to claim 5, characterized in that... Between steps (2) and (3), a surface treatment step (2b) is performed, specifically as follows: The gold alloy wire obtained in step (2) is placed in an ultrasonic cleaner and the surface of the wire is cleaned with water as the cleaning solution. Then, it is placed in a 0.01% benzotriazole ethanol solution for passivation treatment. Alternatively, the gold alloy wire obtained in step (2) can be passivated by placing it in a benzotriazole ethanol solution with a mass percentage concentration of 0.01%.

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