Silver-in-gold alloy bonding wire and preparation method and application thereof

Abstract

The invention relates to the field of integrated circuit packaging, in particular to a gold-clad silver alloy bonding wire and a preparation method and application thereof. The gold-clad silver alloy bonding wire is mainly made of a silver alloy core material and a pure gold pipe material coated outside the silver alloy core material. The silver alloy core material comprises the following components in parts by mass: 90 to 99 parts of silver, 0.5 to 5 parts of nickel, 0.1 to 3.0 parts of palladium, 0.35 to 3.5 parts of indium and 0.05 to 1 part of yttrium. The gold-clad silver alloy bonding wire has the advantages of being stable in performance and free of residues on the surface, and meanwhile has high corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit packaging, and in particular to a gold-clad silver alloy bonding wire and a preparation method and application thereof. Background Art

[0002] Bonding wires are the inner leads between the chip and the frame, and are one of the basic materials for integrated circuit packaging. As society's demand for the quantity and quality of integrated circuits continues to increase, the demand for bonding wires is growing. Traditional gold bonding wires, due to their excellent electrochemical properties and high reliability, have become the most widely used bonding wires in the high-end chip packaging industry. However, due to the high price of gold and limited global reserves, the price of gold bonding wires remains high. In order to reduce costs, it is a general trend to find alternative products with equivalent performance and low prices.

[0003] Silver has good electrical, thermal and mechanical properties, good bonding performance, and its price is only about 1.3% of gold, making it a good candidate for replacing gold bonding wires. However, silver is less resistant to oxidation than gold, and is easily sulfided and prone to electron migration, resulting in poor conductivity and reduced reliability, which limits its application in the high-end electronic packaging industry. Developing silver alloy wires that are resistant to corrosion, sulfidation and electron migration, and coating them with Au to form a protective layer, can produce bonding wires with good bonding performance and strong corrosion resistance, thus replacing gold bonding wires.

[0004] At present, silver-based bonding wires have the problem of uneven composition of various parts, which causes unstable product performance; the gold-coated process of gold-clad silver bonding wires is mainly completed through chemical plating and electroplating. The existing processes have defects such as process pollution of the environment, and the plating solution contains acid and base ions, which are easy to remain on the surface of the wire, affecting the corrosion resistance of the bonding wire.

[0005] In view of this, the present invention is proposed, which uses powder metallurgy to prepare silver alloy core materials to improve the uniformity of core material composition and performance stability, and uses hot isostatic pressing diffusion welding to coat gold on the surface of the silver alloy to form a clean, reliable and residue-free bonding interface, thereby obtaining a bonding wire with stable performance and good corrosion resistance. Summary of the invention

[0006] The object of the present invention is to provide a gold-clad silver alloy bonding wire and a preparation method and application thereof. The gold-clad silver alloy bonding wire has a stable structure, no residue on the surface, and has strong corrosion resistance, anti-sulfurization performance and anti-electron migration performance.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] One aspect of the present invention relates to a gold-clad silver alloy bonding wire, which is mainly made of a silver alloy core material and a pure gold tube material coated outside the silver alloy core material;

[0009] The components of the silver alloy core material include, by mass:

[0010] 90-99 parts of silver, 0.5-5 parts of nickel, 0.1-3.0 parts of palladium, 0.35-3.5 parts of indium and 0.05-1 part of yttrium.

[0011] The gold-clad silver alloy bonding wire has uniform composition, stable performance, no residue on the surface, and strong corrosion resistance.

[0012] Another aspect of the present invention also relates to a method for preparing a gold-clad silver alloy bonding wire, comprising the following steps:

[0013] (a) mixing raw material powders of the silver alloy core material in proportion and then vacuum sintering to obtain the silver alloy core material;

[0014] (b) assembling the silver alloy core material and the pure gold tube material, performing hot isostatic pressing diffusion welding and cooling to obtain a gold-clad silver blank rod;

[0015] (c) reducing the diameter of the gold-clad silver blank rod.

[0016] The method for preparing the gold-clad silver alloy bonding wire has the advantages of uniform composition, environmental protection, easy operation, etc. The prepared bonding wire has stable performance, no residue on the surface, and good corrosion resistance.

[0017] Another aspect of the present invention also relates to an integrated circuit packaging material, including the gold-clad silver alloy bonding wire or the bonding wire prepared by the preparation method of the gold-clad silver alloy bonding wire.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The gold-clad silver alloy bonding wire provided by the present invention is mainly made of a silver alloy core material and a pure gold tube coated on the outside of the silver alloy core material. The components of the silver alloy core material are reasonably selected and assembled, so that the bonding wire has improved anti-oxidation, anti-sulfurization and anti-electron migration capabilities, and has strong corrosion resistance.

[0020] (2) The preparation method of the gold-clad silver alloy bonding wire provided by the present invention first uses the powder metallurgy method to prepare the silver alloy core material, and fully mixes the components before smelting to improve the composition uniformity and performance stability of the core material; then uses hot isostatic pressing diffusion welding to weld the silver alloy core material and the pure gold tube together, avoiding the problem that chemical plating and electroplating are easy to pollute the environment and affect the performance of the bonding wire; this method is green and environmentally friendly, and the prepared bonding wire has stable performance, no residue on the surface, and has good corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A preparation process roadmap provided for an embodiment of the present invention;

[0023] Figure 2 A cross-sectional view of a core material hot pressing set provided in an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of the structure of a graphite sleeve provided in an embodiment of the present invention.

[0025] Reference numerals:

[0026] 1-graphite base, 2-quartz tube, 3-silver alloy mixed powder, 4-graphite flange, 5-weight block, 6-first graphite component, 7-second graphite component, 8-gap, 9-convex teeth, 10-groove. DETAILED DESCRIPTION

[0027] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0028] One aspect of the present invention relates to a gold-clad silver alloy bonding wire, which is mainly made of a silver alloy core material and a pure gold tube material coated outside the silver alloy core material;

[0029] The components of the silver alloy core material include, by mass:

[0030] 90-99 parts of silver, 0.5-5 parts of nickel, 0.1-3.0 parts of palladium, 0.35-3.5 parts of indium and 0.05-1 part of yttrium.

[0031] In some specific embodiments, the composition of the silver alloy core material includes, by weight:

[0032] 90 to 99 parts of silver (for example, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts or 99 parts), 0.5 to 5 parts of nickel (for example, 0.5 parts, 1 parts, 2 parts, 3 parts, 4 parts, 5 parts), 0.1 to 3 parts of palladium (for example, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts), 0.35 to 3.5 parts of indium (for example, 0.35 parts, 0.7 parts, 1.4 parts, 2.1 parts, 2.8 parts, 3.5 parts), 0.1 to 1 part of yttrium (for example, 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts or 1 parts).

[0033] The gold-clad silver alloy bonding wire is mainly made of a silver alloy core material and a pure gold tube coated on the outside of the silver alloy core material. The components of the silver alloy core material are reasonably selected and assembled, so that the bonding wire has improved anti-oxidation, anti-sulfurization and anti-electron migration capabilities, and has strong corrosion resistance.

[0034] The melting point of the bonding wire is generally controlled between 700 and 1000°C. According to the silver-palladium metallographic diagram, silver and palladium are infinitely miscible, and the lowest melting point of the alloy is 961.93°C. As the palladium content increases, the palladium content is controlled between 0.1 and 3.0 parts according to the relationship between the liquidus and the palladium content. If the palladium content is higher than this range, the melting point of the bonding wire is too high. The bonding wire needs to be melted and fired into a solder ball during bonding, and it is difficult to melt when firing the ball. If it is lower than this range, the corrosion resistance is poor.

[0035] Nickel can improve the corrosion resistance and electron migration resistance of silver alloys. The resistivity of silver is 1.58Ω·m, and the resistivity of nickel is 6.84Ω·m. In order to maintain the low resistivity of the silver alloy core material, the mass fraction of nickel in the new silver alloy material of the present invention is limited to within 0.5-5%.

[0036] Nickel and palladium can be dissolved indefinitely, and the melting point after dissolution is ≥1237°C. The melting point is too high, which is not conducive to tissue regulation. Moreover, nickel has a high melting point (1453°C) and is immiscible with silver. Nickel requires a third element to form an alloy with silver, so other elements need to be added to assist the formation of the silver-nickel alloy and adjust the melting point of nickel at the same time. Indium can form an alloy with nickel. When the mass fraction of nickel is 58.6%, the indium-nickel alloy forms a peritectic alloy with a melting point of 910°C. The melting point temperature meets the use requirements of the bonding wire, and the silver-nickel alloy has good corrosion resistance. Therefore, the weight ratio of indium to nickel in the new silver alloy material of the present invention is:

[0037] Nickel: Indium = 58.6: 41.4;

[0038] wIndium=wNi×(41.4 / 58.6)=0.706×wNi;

[0039] wIndium——mass fraction of indium;

[0040] wNickel——mass fraction of nickel;

[0041] The mass fraction of indium is 0.706 times the mass fraction of nickel.

[0042] Adding rare earth metal yttrium to silver-nickel alloy can refine grains, increase the toughness and strength of the silver alloy core material, and improve electrical properties. The yttrium content in the silver-nickel-yttrium alloy is in the range of 0.05% to 1.0%.

[0043] Furthermore, the pure gold tube is made by rolling a rectangular pure gold sheet.

[0044] Furthermore, the calculation formula of the thickness of the pure gold sheet is as follows:

[0045]

[0046] Among them, t 金 is the thickness of the pure gold sheet, that is, the thickness of the pure gold sheet before diameter reduction, in mm;

[0047] D is the diameter of the silver alloy core material, that is, the diameter of the silver alloy core material before diameter reduction, in mm;

[0048] h 金层 is the thickness of the gold layer in the finished bonding wire, that is, the thickness of the gold layer in the finished bonding wire after diameter reduction, in (mm), h 金层 =50×10 -6 ~200×10 -6 mm;

[0049] d is the finished bonding wire diameter, i.e. the wire diameter of the finished bonding wire obtained after diameter reduction, in mm, d = 10 × 10 -3 ~75×10 -3 mm.

[0050] The thickness of the pure gold sheet is t 金 According to the core diameter D of the gold-clad silver bonding wire, the finished wire diameter d and the thickness h of the gold layer in the finished wire 金层 According to the principle that the volume ratio of the gold layer of the bonding wire and the silver alloy core material remains unchanged during the processing, the following formula is obtained:

[0051] πDt 金 / π(D / 2) 2 =π(dh 金层 )h 金层 / π(d / 2-h 金层 ) 2 .

[0052] The above formula is derived to obtain the calculation formula for the thickness of the pure gold sheet.

[0053] The composition of pure gold pipe is Au with a purity of not less than 99.99%.

[0054] Furthermore, the wire diameter d of the gold-clad silver alloy bonding wire is 10 to 75 μm (for example, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm or 75 μm).

[0055] Furthermore, the thickness of the gold coating h 金 The thickness of the gold coating layer is 50-200 nm (e.g., 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 175 nm or 200 nm). If the thickness of the gold coating layer is less than 50 nm, the corrosion resistance is insufficient, and if it is greater than 200 nm, the precious metal content is too high, resulting in excessive cost.

[0056] Another aspect of the present invention also relates to a method for preparing a gold-clad silver alloy bonding wire, comprising the following steps:

[0057] (a) mixing raw material powders of the silver alloy core material in proportion and then vacuum sintering to obtain the silver alloy core material;

[0058] (b) assembling the silver alloy core material and the pure gold tube material, performing hot isostatic pressing diffusion welding and cooling to obtain a gold-clad silver blank rod;

[0059] (c) reducing the diameter of the gold-clad silver blank rod

[0060] The existing production method of silver alloy bonding wire mainly prepares silver alloy billet rods by continuous casting, which has problems of uneven composition and unstable performance; gold-plated silver bonding wire mainly uses electroplating or chemical plating to plate pure gold on the outer wall of the silver wire, and it is inevitable to use a plating solution containing chemical components such as acid and alkali ions. The chemical ions in the plating solution are easy to remain on the surface of the wire body, thereby affecting the corrosion resistance of the bonding wire. The used plating solution is very likely to cause environmental pollution. Therefore, the existing technology has certain defects both in terms of product performance and environmental impact.

[0061] Powder metallurgy is a metallurgical method for preparing metal materials. Because the raw materials are powders, all components can be fully stirred and mixed before smelting to obtain a mixed powder with highly uniform composition. Vacuum hot pressing and sintering the mixed powder can obtain metal ingots with high composition uniformity, ensuring the consistency of the composition of each part.

[0062] Hot Isostatic Pressing Diffusion Welding (HIP) is a solid-state welding technology under high temperature and high pressure, which is often used to connect difficult-to-process materials such as high-temperature alloys, titanium alloys, and nickel alloys. The principle of this technology is to heat the two workpieces to be connected to a certain temperature under high temperature and high pressure, and then apply pressure to make the two workpieces diffuse and combine in the solid state to form a whole. This connection method has the advantages of high strength, high density, high toughness, and high corrosion resistance, and can make the connection part have good mechanical properties and chemical stability.

[0063] The method for preparing a bonding wire provided by the present invention first uses a powder metallurgy method to prepare a silver alloy core material, and fully mixes the components before smelting to improve the composition uniformity and performance stability of the core material.

[0064] Furthermore, during the vacuum sintering process, the absolute pressure of the vacuum furnace chamber is 1×10 -4 ~9×10 -1 Pa (e.g. 1×10 -4 , 1×10 -3 , 1×10 -2 or 9×10 -1 ).

[0065] Furthermore, the vacuum sintering temperature is 673-770°C (for example, 673°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C or 770°C).

[0066] During the metal sintering process, due to the mutual attraction of solid molecules (or atoms), the powder body produces particle bonding under high temperature and high pressure, and the powder body is densified and recrystallized through material migration to form a dense and hard sintered body. The calculation formula of sintering temperature is:

[0067] T S =(0.7~0.8)T M ;

[0068] T S is the sintering temperature (℃); T M is the absolute melting point of the powder (℃). When the melting point of the silver alloy core material is T M When the melting point of silver is 961.93℃, the sintering temperature range is: T S =(0.7~0.8)

[0069] ×961.93=673~770(℃).

[0070] Furthermore, the vacuum sintered structure is as follows Figure 2 shown.

[0071] Furthermore, the vacuum sintering time is 30 to 120 minutes (e.g., 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes or 120 minutes). If the sintering time is less than 30 minutes, the material density of the core material after sintering will be relatively low, thereby affecting the strength and conductivity of the material. If the sintering time is greater than 120 minutes, it will cause grain growth, which will also reduce the material density.

[0072] In some specific embodiments, the core material hot pressing kit is placed in a vacuum furnace, and the furnace chamber is evacuated until the vacuum degree in the furnace chamber reaches 10 -4 ~10 -1 Pa (e.g. 6.7×10 -3 Pa, 5×10 -2 Pa or 5×10 -1 Pa); then the furnace temperature is heated to 673-770°C (for example, 673°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C or 770°C), and the temperature is kept for 30-120min (for example, 30min, 45min, 60min, 90min or 120min); after the furnace temperature is cooled, the core material hot pressing kit is taken out, all tooling is removed, and the silver alloy core material is obtained.

[0073] Furthermore, during the vacuum sintering process, a counterweight block is used to press the powder core material.

[0074] Powder pressing can be considered that first the powder particles are displaced to fill the air gap, and then when the pressing force exceeds the plastic deformation resistance of the material, the powder particles are plastically deformed to obtain a dense pressed blank. Figure 2 In the sintered structure shown, the powder core material is pressed by the weight of the counterweight 5 during the sintering process, and the pressing is performed at the sintering temperature.

[0075] According to the relationship between deformation resistance and temperature:

[0076] P t1 =P t2 *e a(t2-t1)

[0077] P t1 ——The plastic deformation resistance value at temperature t1, which can be approximately regarded as the yield strength;

[0078] P t2 ——The plastic deformation resistance value at temperature t2 can be approximately regarded as the yield strength;

[0079] a——Temperature coefficient. The temperature coefficient of single-phase and multi-phase alloys is 0.0085.

[0080] Take t1 as the sintering temperature Ts, t2 as the room temperature 25°C, and Pt2 as the yield strength of silver at room temperature 35MPa, i.e. 35kg / cm 2 , so the deformation resistance of silver at sintering temperature is: P Ts =35×e 0.0085(25-Ts) .

[0081] The weight M of the counterweight 5 is calculated as follows:

[0082] M≥S×P Ts =π(D / 2) 2 ×35×e 0.0085(25-Ts) ;

[0083] M≥27.5×D 2 ×e 0.0085×(25-Ts) ;

[0084] M——weight of counterweight 5 (kg);

[0085] S——Cross-sectional area of ​​powder pressed silver alloy core (cm 2 );

[0086] D——diameter of powder pressed silver alloy core (cm);

[0087] Ts——Sintering temperature (℃).

[0088] For example, when the diameter of the silver alloy core material during sintering is 100 mm, namely 10 cm, and the sintering temperature is 700° C., the weight M of the counterweight block 5 is ≥ 8.86 kg.

[0089] Furthermore, the vacuum sintering furnace temperature is 20-80°C (eg, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C).

[0090] Further, the temperature of the hot isostatic pressing diffusion welding is 577-770°C (for example, 577°C, 590°C, 620°C, 650°C, 670°C, 690°C, 710°C, 730°C, 750°C or 770°C).

[0091] The temperature calculation formula for hot isostatic pressing diffusion welding is as follows:

[0092] T h =(0.6~0.8)T M ;

[0093] Among them, T h is the temperature of hot isostatic pressing diffusion welding, in °C;

[0094] T M is the absolute melting point of the powder, in °C.

[0095] When T M When the melting point of silver is 961.93℃, the diffusion soldering temperature is: T h =577~770℃.

[0096] If the temperature of hot isostatic pressing diffusion welding exceeds this temperature range, the core material will soften or even melt, and the shape of the core material and the tube cannot be guaranteed. The diameter of the core material and the thickness of the tube after diffusion cannot be guaranteed to be uniform, which will cause instability in the size and quality of the wire during the subsequent processing. If the temperature is lower than this temperature range, the two materials cannot produce atomic mutual diffusion, and a new diffusion layer cannot be formed at the interface to achieve a reliable connection. In the subsequent drawing process, it is easy to cause the core material and the tube to separate, resulting in the gold coating on the outer layer of the silver alloy wire falling off, and the corrosion resistance is reduced.

[0097] After the silver alloy core material is prepared, the silver alloy core material and the pure gold tube are welded together by hot isostatic pressing diffusion welding to prepare a gold-clad silver blank rod, avoiding the problem that chemical plating and electroplating are easy to pollute the environment and affect the performance of the bonding wire. This method is green and environmentally friendly, and the prepared bonding wire has stable performance, no residue on the surface, and has good corrosion resistance, sulfidation resistance and electron migration resistance.

[0098] Furthermore, the pressure of hot isostatic pressing diffusion welding is 0.5-50 MPa (eg, 0.5 MPa, 5 MPa, 15 MPa, 25 MPa, 35 MPa, 45 MPa or 50 MPa).

[0099] If the pressure of hot isostatic pressing diffusion welding is lower than this range, the two materials cannot produce mutual diffusion of atoms, and a new diffusion layer cannot be formed at the interface to achieve reliable connection. In the later drawing process, it is easy to cause the core material and the tube to separate, resulting in the gold coating of the outer layer of the silver alloy wire falling off and the corrosion resistance decreasing. If the pressure is higher than this range, the requirements for equipment increase sharply, the equipment cost is too high or damaged, and the core material and the gold tube are deformed, resulting in dimensional accuracy exceeding the tolerance.

[0100] Furthermore, the hot isostatic pressing diffusion welding time is 10 to 240 minutes (for example, 10 minutes, 50 minutes, 100 minutes, 150 minutes, 200 minutes or 240 minutes). If the hot isostatic pressing diffusion welding time is lower than this range, the mutual diffusion between the atoms of the two materials is insufficient, the diffusion layer is too thin, the material connection is unreliable, and the core material and the tube are easily separated in the later drawing process, resulting in the gold coating layer of the outer layer of the silver alloy wire falling off, and the corrosion resistance is reduced; if the diffusion time is higher than this range, the thermal expansion of the silver alloy core material will be greater than the thermal expansion of the gold tube, causing the gold tube to become thinner or even deformed, and the final composite blank size accuracy will be reduced. Moreover, if the diffusion time is too long, the core material and the tube will dissolve into each other, resulting in a large amount of silver being dissolved in the gold coating layer, and the corrosion resistance will be reduced.

[0101] Furthermore, the pressure medium of hot isostatic pressing diffusion welding includes: an inert gas. In some specific embodiments, the inert gas includes but is not limited to: nitrogen or argon.

[0102] Furthermore, the pressure medium of hot isostatic pressing diffusion welding may also include: reducing gas. In some specific embodiments, the reducing gas includes: at least one of hydrogen, nitrogen or argon.

[0103] Then, the prepared gold-clad silver blank rod is reduced in diameter to 10-75 μm to obtain a gold-clad silver bonding wire.

[0104] Furthermore, the prepared gold-clad silver wire has a diameter of 10 to 75 μm (for example, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 75 μm).

[0105] In some specific embodiments, the method for preparing the gold-clad silver alloy bonding wire is as follows: Figure 1 As shown, the following steps are included:

[0106] (1) Material preparation: prepare pure silver powder, nickel powder, palladium powder, indium powder, and yttrium powder according to the proportions, and prepare pure gold sheets as required;

[0107] (2) Sintering of silver alloy core material: Pure silver powder is fully mixed with nickel powder, palladium powder, indium powder and yttrium powder according to a certain proportion; the mixed powder is placed in a cylindrical quartz tube 2 or a graphite crucible to prepare a core material hot pressing kit; the core material hot pressing kit is placed in a vacuum furnace for sintering, and the furnace chamber is first evacuated; the furnace temperature is then heated to the sintering temperature and the high temperature is maintained; after the furnace temperature is cooled, the core material hot pressing kit is taken out; then, the core material hot pressing kit is taken out and all tooling is removed to obtain the silver alloy core material;

[0108] (3) rolling the pure gold sheet into a pure gold tube, assembling the silver alloy core material and the pure gold tube, placing them in a set of graphite sleeves, tightly wrapping the outside of the graphite sleeves with pre-tensioned steel wires to make a diffusion welding unit, performing hot isostatic pressing diffusion welding and cooling on the diffusion welding unit in a high-pressure and high-temperature furnace, and removing the sleeves to obtain a gold-clad silver blank rod;

[0109] (4) Reduce the diameter of the gold-plated silver billet to Obtain gold-clad silver bonding wire.

[0110] In some specific embodiments, the method for making the core material hot pressing kit is:

[0111] The silver alloy mixed powder 3 is placed in a cylindrical quartz tube 2 or a graphite crucible; the lower part is sealed with a graphite base 1 to keep the quartz tube 2 stable and vertical, the upper part is pressed with a graphite flange 4, and a high-temperature resistant and high-density counterweight 5 is placed on the graphite block for pressure to make a core material hot pressing kit, such as Figure 2 shown.

[0112] In some specific embodiments, the graphite sleeve uses a staggered insertion structure, which has the functions of tightly wrapping the material, continuing to press inward under high pressure, and guiding the pressing movement. Figure 3 As shown. The graphite sleeve can be composed of 2 to 10 graphite components. Taking the graphite sleeve with two graphite components as an example, one or more pairs of convex teeth 9 and grooves 10 are processed on both sides of each graphite component. When assembled, the convex teeth 9 of the first graphite component 6 are aligned with the grooves 10 of the second graphite component 7, and a group of graphite components are assembled into a hollow cylinder. A certain gap 8 is left between the assembled convex teeth 9 and the grooves 10. When the outside is subjected to a more isotropic uniform pressure, each graphite component can move inward in the expected direction to further compress the workpiece.

[0113] The embodiments of the present invention will be described in detail below with reference to specific examples and comparative examples.

[0114] Example 1

[0115] The method for preparing the gold-clad silver alloy bonding wire provided in this embodiment comprises the following steps:

[0116] 1. Prepare the raw materials of silver alloy core material according to the following mass parts, with a powder particle size of 100 mesh; including:

[0117] 98.95 parts of silver powder, 0.5 parts of nickel powder, 0.1 parts of palladium powder, 0.35 parts of indium powder, and 0.1 parts of yttrium powder;

[0118] The raw material of pure gold pipes is 99.999% pure gold;

[0119] The finished product goal is to prepare gold-clad silver bonding wire with a wire diameter of 25μm and a pure gold cladding thickness of 100nm.

[0120] 2. Use a V-type mixer to mix the powder thoroughly;

[0121] 3. According to Figure 2 The structure shown is that the lower end of a quartz tube 2 with an inner diameter of 65 mm and a thickness of 2 mm is sealed with a graphite base 1, the powder is placed in the quartz tube 2 and compacted, the upper end is pressed with a flange graphite block, and a counterweight block 5 is pressed on the graphite block to make a core material hot pressing kit;

[0122] The weight of the counterweight 5 is calculated as follows:

[0123] M>27.5×6.5 2 ×e 0.0085(750-25) =2.45(kg)

[0124] Select a 5kg counterweight 5 to meet the usage requirements.

[0125] 4. Place the core material hot pressing kit into the vacuum furnace and evacuate the furnace chamber until the vacuum degree in the furnace chamber reaches 6.7×10 - 3 Pa; then the furnace temperature is heated to 750°C and kept at this temperature for 60 minutes; after the furnace temperature is cooled, the core material hot pressing kit is taken out, all tooling is removed, and a silver alloy round rod is obtained;

[0126] 5. Roll the gold into pure gold sheets. The thickness of the pure gold sheets is calculated using formula (1):

[0127]

[0128] Cut the pure gold sheet to a length equal to the length of the silver alloy line segment and a width equal to the outer circumference of the silver alloy core material, that is:

[0129] W gold=65×π=204.2(mm)

[0130] 7. Use a rolling device to make the pure gold sheet into a gold sheet tube to obtain a pure gold tube, the inner diameter of which is equal to the outer diameter of the silver alloy core material;

[0131] 8. Use pure gold tubing to wrap the silver alloy core material and place it in two prefabricated semi-cylindrical graphite sleeves, such as Figure 3 As shown, a diffusion welding unit is made by tightly and evenly winding steel wire;

[0132] 9. Place the diffusion welding unit in a hot isostatic pressing furnace for diffusion welding. The diffusion welding temperature is 600°C, the melting temperature of the silver alloy ingot, the diffusion pressure is 50 MPa, and the holding time is 30 min. The two materials of the diffusion welding unit form a metallurgical bond, forming a strong and pure interface bond. The diffusion welding unit is transformed into a gold-clad silver ingot to obtain a gold-clad silver billet rod with a diameter of 65 mm.

[0133] 10. Use a rotary forging machine to reduce the diameter of the gold-clad silver blank rod to a diameter of 8 mm, and then use a wire drawing machine to reduce the diameter and draw the product to a final wire diameter of 25 μm to obtain a gold-clad silver bonding wire.

[0134] Example 2

[0135] The method for preparing the gold-clad silver alloy bonding wire provided in this embodiment comprises the following steps:

[0136] 1. Prepare the raw materials of silver alloy core material according to the following mass parts, with a powder particle size of 200 mesh; including:

[0137] 97.8 parts of silver powder, 1 part of nickel powder, 0.2 parts of palladium powder, 0.7 parts of indium powder, and 0.3 parts of yttrium powder;

[0138] The raw material of pure gold pipes is 99.995% pure gold;

[0139] The finished product goal is to produce gold-clad silver bonding wire with a wire diameter of 15μm and a pure gold coating thickness of 80nm.

[0140] 2. Use a three-dimensional mixer to mix the powder thoroughly;

[0141] 3. According to Figure 2 The structure shown is that the lower end of a quartz tube 2 with an inner diameter of 100 mm and a thickness of 2 mm is sealed with a graphite base 1, the powder is placed in the quartz tube 2 and compacted, the upper end is pressed with a flange graphite block, and a counterweight block 5 is pressed on the graphite block to make a core material hot pressing kit;

[0142] The weight of the counterweight 5 is calculated as follows:

[0143] M>27.5×10 2 ×e 0.0085(680-25) =10.5(kg)

[0144] Select 12kg counterweight 5 to meet the usage requirements.

[0145] 4. Place the core material hot pressing kit into the vacuum furnace and evacuate the furnace chamber until the vacuum degree in the furnace chamber reaches 1×10 -2 Pa; then the furnace temperature is heated to 680°C and kept at this temperature for 100 minutes; after the furnace temperature is cooled, the core material hot pressing kit is taken out, all tooling is removed, and a silver alloy round rod is obtained;

[0146] 5. Roll the gold into pure gold sheets. The thickness of the pure gold sheets is calculated using formula (1):

[0147]

[0148] Cut the pure gold sheet to a length equal to the length of the silver alloy line segment and a width equal to the outer circumference of the silver alloy core material, that is:

[0149] W gold=100×π=314.2(mm)

[0150] 7. Use a rolling device to make the pure gold sheet into a gold sheet tube to obtain a pure gold tube, the inner diameter of which is equal to the outer diameter of the silver alloy core material;

[0151] 8. Use pure gold tubing to wrap the silver alloy core material and place it in the prefabricated four semi-cylindrical graphite sleeves, such as Figure 3 As shown, a diffusion welding unit is made by tightly and evenly winding steel wire;

[0152] 9. Place the diffusion welding unit in a hot isostatic pressing furnace for diffusion welding. The diffusion welding temperature is 680°C, the melting temperature of the silver alloy billet, the diffusion pressure is 40 MPa, and the holding time is 90 min. The two materials of the diffusion welding unit form a metallurgical bond, forming a strong and pure interface bond. The diffusion welding unit is transformed into a gold-clad silver ingot to obtain a gold-clad silver billet rod with a diameter of 100 mm.

[0153] 10. Use a rotary forging machine to reduce the diameter of the gold-clad silver blank rod to a diameter of 10 mm, and then use a wire drawing machine to reduce the diameter and draw the product to a final wire diameter of 15 μm to obtain a gold-clad silver bonding wire.

[0154] Example 3

[0155] The method for preparing the gold-clad silver alloy bonding wire provided in this embodiment comprises the following steps:

[0156] 1. Prepare the raw materials of silver alloy core material according to the following mass parts, with a powder particle size of 200 mesh; including:

[0157] 95.1 parts of silver powder, 2 parts of nickel powder, 1 part of palladium powder, 1.4 parts of indium powder, and 0.5 parts of yttrium powder;

[0158] The raw material of pure gold pipes is 99.99% pure gold;

[0159] The finished product goal is to produce gold-clad silver bonding wire with a wire diameter of 30μm and a pure gold coating thickness of 120nm.

[0160] 2. Use a high-speed ball mill to mix the powder thoroughly;

[0161] 3. According to Figure 2 The structure shown is that the lower end of a quartz tube 2 with an inner diameter of 50 mm and a thickness of 2 mm is sealed with a graphite base 1, the powder is placed in the quartz tube 2 and compacted, the upper end is pressed with a flange graphite block, and a counterweight block 5 is pressed on the graphite block to make a core material hot pressing kit;

[0162] The weight of the counterweight 5 is calculated as follows:

[0163] M>27.5×10 2 ×e 0.0085(673-25) =2.79(kg)

[0164] Select 3kg counterweight 5 to meet the usage requirements.

[0165] 4. Place the core material hot pressing kit into the vacuum furnace and evacuate the furnace chamber until the vacuum degree in the furnace chamber reaches 5×10 -4 Pa; then the furnace temperature is heated to 673°C and kept at this temperature for 50 minutes; after the furnace temperature is cooled, the core material hot pressing kit is taken out, all tooling is removed, and a silver alloy round rod is obtained;

[0166] 5. Roll the gold into pure gold sheets. The thickness of the pure gold sheets is calculated using formula (1):

[0167]

[0168] Cut the pure gold sheet to a length equal to the length of the silver alloy line segment and a width equal to the outer circumference of the silver alloy core material, that is:

[0169] W gold=50×π=157.1(mm)

[0170] 7. Use a rolling device to make the pure gold sheet into a gold sheet tube to obtain a pure gold tube, the inner diameter of which is equal to the outer diameter of the silver alloy core material;

[0171] 8. Use pure gold tubing to wrap the silver alloy core material and place it in the prefabricated four semi-cylindrical graphite sleeves, such as Figure 3 As shown, a diffusion welding unit is made by tightly and evenly winding steel wire;

[0172] 9. Place the diffusion welding unit in a hot isostatic pressing furnace for diffusion welding. The diffusion welding temperature is 750°C, the melting temperature of the silver alloy billet, the diffusion pressure is 10 MPa, and the holding time is 50 min. The two materials of the diffusion welding unit form a metallurgical bond, forming a strong and pure interface bond. The diffusion welding unit is transformed into a gold-clad silver ingot to obtain a gold-clad silver billet rod with a diameter of 50 mm.

[0173] 10. The gold-clad silver billet rod is processed by a rolling machine to a diameter of 7 mm, and then a wire drawing machine is used to reduce the diameter and draw the product to a final wire diameter of 30 μm to obtain a gold-clad silver bonding wire.

[0174] Comparative Example 1

[0175] The preparation method of the bonding wire in this comparative example is to use a continuous casting method to manufacture a silver alloy billet rod, and to use a chemical plating method to plate pure gold, which specifically includes the following steps:

[0176] 1. Use silver alloy to continuously cast into diameter Silver alloy billet rod;

[0177] 2. Pull the 8mm pure silver blank rod into a diameter of pure silver wire;

[0178] 3. Use chemical plating method The surface of the pure silver wire is plated with 0.001mm thick pure gold;

[0179] 4. The gold-plated silver wire is drawn to a finished gold-plated silver wire with a wire diameter of 25μm.

[0180] Comparative Example 2

[0181] The preparation method of the bonding wire in this comparative example is to use a continuous casting method to manufacture a silver alloy billet rod, and to use an electroplating method to plate pure gold, which specifically includes the following steps:

[0182] 1. Use 99.99% silver to continuously cast into diameter of sterling silver blank rod;

[0183] 2. Pull the 10mm pure silver blank rod into a diameter of pure silver wire;

[0184] 3. Use electroplating method The surface of the pure silver wire is electroplated with 0.002mm thick pure gold;

[0185] 4. The gold-plated silver wire is drawn to a finished gold-plated silver wire with a diameter of 15μm;

[0186] Comparative Example 3

[0187] The implementation steps are the same as those in Example 1, but the thickness of the gold sheet is 0.1 mm.

[0188] Comparative Example 4

[0189] The implementation steps are the same as those in Example 2, but the sintering temperature is 550°C.

[0190] Comparative Example 5

[0191] The implementation steps are the same as those in Example 2, but the weight of the counterweight 5 is 5 kg.

[0192] Comparative Example 6

[0193] The implementation steps are the same as those in Example 3, but the diffusion temperature is 400°C.

[0194] Comparative Example 7

[0195] The implementation steps are the same as those of Example 3, but the content of indium in the silver alloy core material is 0.5 parts.

[0196] The wire diameter, breaking force, oxidation discoloration time, sulfurization discoloration time, and electron migration failure time of the prepared bonding wire products were tested, and the results are shown in Table 1.

[0197] Table 1 Experimental results

[0198]

[0199]

[0200] It can be seen from Table 1 that the bonding wires of the embodiments have higher tensile strength, dimensional stability and corrosion resistance than those of the comparative examples, which indicates that the bonding wires provided by the present invention have high dimensional accuracy and strong corrosion resistance.

[0201] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A gold-clad silver alloy bonding wire, characterized in that: Mainly made of a silver alloy core material and a pure gold tube covering the silver alloy core material; The components of the silver alloy core material include, by mass: 90-99 parts of silver, 0.5-5 parts of nickel, 0.1-3.0 parts of palladium, 0.35-3.5 parts of indium and 0.05-1 part of yttrium.

2. The gold-clad silver alloy bonding wire according to claim 1, characterized in that: The mass fraction of indium is 0.706 times the mass fraction of nickel; Preferably, the pure gold tube is made by rolling a rectangular pure gold sheet; Preferably, the thickness of the pure gold sheet is calculated as follows: Among them, t 金 is the thickness of the pure gold sheet, in mm; D is the diameter of the silver alloy core material, in mm; h 金层 is the thickness of the gold layer in the finished bonding wire, in mm, h 金层 =50×10 -6 ~200×10 -6 mm; d is the finished bonding wire diameter, in mm, d = 10 × 10 -3 ~75×10 -3 mm.

3. The method for preparing the gold-clad silver alloy bonding wire according to claim 1 or 2, characterized in that: The following steps are involved: (a) mixing raw material powders of the silver alloy core material in proportion and then vacuum sintering to obtain the silver alloy core material; (b) assembling the silver alloy core material and the pure gold tube material, performing hot isostatic pressing diffusion welding and cooling to obtain a gold-clad silver blank rod; (c) reducing the diameter of the gold-clad silver blank rod.

4. The method for preparing the gold-clad silver alloy bonding wire according to claim 3, characterized in that: During the vacuum sintering process, the absolute pressure of the vacuum furnace chamber is 1×10 -4 ~9×10 -1 Pa.

5. The method for preparing the gold-clad silver alloy bonding wire according to claim 3, characterized in that: The temperature of the vacuum sintering of the silver alloy core material is 673-770°C: Preferably, the vacuum sintering and heat preservation time is 30 to 120 minutes.

6. The method for preparing the gold-clad silver alloy bonding wire according to claim 3, characterized in that: During the vacuum sintering process, the powder core material is pressed by a counterweight block.

7. The method for preparing the gold-clad silver alloy bonding wire according to claim 6, characterized in that: The weight calculation formula of the counterweight block is as follows: M≥27.5×D 2 ×e 0.0085×(25-Ts) ; Wherein, M is the weight of the counterweight, in kg; D is the diameter of the powder pressed silver alloy core, in cm; Ts is the sintering temperature in °C.

8. The method for preparing the gold-clad silver alloy bonding wire according to claim 3, characterized in that: The vacuum sintering furnace temperature is 20-80°C.

9. The method for preparing the gold-clad silver alloy bonding wire according to claim 3, characterized in that: The temperature of the hot isostatic pressing diffusion welding is 577-770°C; Preferably, the pressure of the hot isostatic pressing diffusion welding is 0.5-50 MPa; Preferably, the hot isostatic pressing diffusion welding time is 10 to 240 minutes.

10. An integrated circuit packaging material, characterized in that: The invention relates to a gold-clad silver alloy bonding wire as claimed in claim 1 or 2 or a gold-clad silver alloy bonding wire prepared by the method for preparing a gold-clad silver alloy bonding wire as claimed in any one of claims 3 to 10.

Images