Grain corrosion method for bonding silver wire and application of grain corrosion method

Abstract

The invention relates to the technical field of bonding wires, in particular to a grain corrosion method of a bonding silver wire and application of the grain corrosion method. The grain corrosion method of the bonding silver wire comprises the following steps: carrying out low-temperature rapid annealing on the bonding silver wire subjected to large deformation to obtain the annealed bonding silver wire; performing first corrosion on the annealed bonding silver wire by adopting a first corrosive liquid, and oxidizing and / or vulcanizing the surface of the annealed bonding silver wire to obtain a pre-corroded bonding silver wire; and carrying out second corrosion on the pre-corrosion bonding silver wire by adopting second corrosion liquid so as to display a microstructure. By means of the method, effective corrosion of the extremely-fine bonded silver wire metallographic specimen subjected to large deformation can be achieved, and the microstructure morphology is shown.

Description

Technical Field

[0001] The invention relates to the technical field of bonding wires, and in particular to a grain corrosion method for bonding silver wires and applications thereof. Background Art

[0002] In the production process of bonding wire, metal materials need to go through multiple drawing processes to obtain the required wire diameter specifications. However, after large plastic deformation, the grain size of ultra-fine silver and its alloys is significantly refined, and there is a large residual stress inside, which makes it extremely difficult to corrode the grain morphology, which brings great difficulties to the control of organizational properties and the determination of heat-affected zones, affecting the performance control of bonding wires and the optimization of bonding processes.

[0003] The traditional method for grain corrosion of silver or its alloys is to use a mixture of hydrogen peroxide and ammonia. Although it has a good corrosion effect on cast structures, it is basically difficult for this corrosion solution to corrode the grain morphology of large deformed structures.

[0004] The difficulties in corroding the grain morphology of ultra-fine silver and its alloy wires with large plastic deformation mainly include: (1) When the wire diameter is fine, the grain size is small, and the grain boundary and phase boundary are very fine, which easily leads to blurred grain boundaries and unclear phase boundaries during the corrosion process; (2) During the large deformation process, the internal residual stress is large and the lattice distortion is serious, making it difficult to corrode a clear grain morphology; (3) As the wire diameter becomes finer, the specific surface area increases. Under the action of interfacial tension, it is difficult for the ultra-fine alloy wire to fully contact with the corrosive solution to achieve effective corrosion, and the substances generated after corrosion adhere to the surface and are difficult to remove in time.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide a method for grain corrosion of bonding silver wires, which can achieve effective corrosion of extremely fine bonding silver wire metallographic samples after large deformation and reveal the microstructure morphology. This solves the problem that the existing corrosion methods are basically difficult to etch out the grain morphology for large deformation structures.

[0007] The second object of the present invention is to provide a method for grain corrosion of a bonding silver wire and its application in the preparation of the bonding silver wire.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] The present invention provides a method for grain corrosion of a bonding silver wire, comprising the following steps:

[0010] Performing low-temperature rapid annealing on the bonding silver wire after the large deformation to obtain the annealed bonding silver wire;

[0011] Using a first etching solution to perform a first etching on the annealed bonding silver wire, oxidizing and / or sulfiding the surface of the annealed bonding silver wire to obtain a pre-etched bonding silver wire;

[0012] The pre-etched bonding silver wire is subjected to a second etching process using a second etching solution to reveal the microstructure.

[0013] Furthermore, the diameter of the bonding silver wire after the large deformation is 15 to 30 μm.

[0014] Furthermore, the large deformation method includes drawing, and the drawing method includes: first large drawing to a material diameter of 8mm to 1.3mm, then medium drawing to a material diameter of 1.3mm to 81.5μm, then fine drawing to a material diameter of 81.5μm to 30μm, and finally micro-drawing to a material diameter of 30μm to 15μm.

[0015] Furthermore, the annealing temperature of the low-temperature rapid annealing is 200-250°C.

[0016] Furthermore, the annealing time of the low-temperature rapid annealing is 0.3 to 0.5 s.

[0017] Furthermore, the first etching solution is mainly prepared by mixing a hydrogen peroxide solution and an ammonia solution in a volume ratio of 0.95 to 1.05:1; wherein the mass fraction of the hydrogen peroxide solution is 2.5% to 3.5%, and the mass fraction of the ammonia solution is 25% to 28%.

[0018] Furthermore, the first etching solution comprises a nitric acid solution with a mass fraction of 3% to 5%.

[0019] Furthermore, the first etching solution is mainly prepared by mixing a nitric acid solution with a mass fraction of 1.5% to 2.5% and a chloric acid solution with a mass fraction of 0.3% to 0.8%; wherein the volume ratio of the nitric acid solution to the chloric acid solution is 0.95 to 1.05:1.

[0020] Furthermore, the first etching solution comprises a sodium thiosulfate solution with a mass fraction of 0.1% to 1%.

[0021] Furthermore, the first etching solution is mainly prepared by mixing a sulfuric acid solution with a mass fraction of 0.05% to 0.15% and a sodium thiosulfate solution with a mass fraction of 0.3% to 0.8%; wherein the volume ratio of the sulfuric acid solution to the sodium thiosulfate solution is 0.95 to 1.05:1.

[0022] Furthermore, the second etching solution is mainly composed of a potassium cyanide solution and an ammonium persulfate solution in a mass ratio of 0.95 to 1.05:1; wherein the mass fraction of the potassium cyanide solution is 18.5% to 21.5%, and the mass fraction of the ammonium persulfate solution is 18.5% to 21.5%.

[0023] Furthermore, the first corrosion time is ≤60s.

[0024] Furthermore, the first etching method includes: immersing the annealed bonding silver wire in the first etching solution.

[0025] Furthermore, after the soaking is completed, the soaked bonding silver wire is taken out, washed with water and wiped with ethanol to remove excess first etching liquid on the surface of the soaked bonding silver wire, so as to obtain a pre-etched bonding silver wire.

[0026] Furthermore, the second corrosion time is 30 to 60 seconds.

[0027] Furthermore, the second etching method includes: after dipping cotton in the second etching liquid, wiping the surface of the pre-etched bonding silver wire.

[0028] Furthermore, after the second etching, the substrate is washed with water and wiped with ethanol to remove excess second etching solution.

[0029] Furthermore, the silver bonding wire includes silver bonding wire and / or silver alloy bonding wire.

[0030] The present invention also provides application of the grain corrosion method of the bonding silver wire in preparing the bonding silver wire.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The grain etching method of the bonding silver wire provided by the present invention can achieve effective etching of the metallographic sample of the extremely fine bonding silver wire and reveal the microstructure morphology. The grain morphology can guide the bonding wire production process and the bonding process.

[0033] (2) The grain corrosion method of the bonding silver wire provided by the present invention can eliminate the lattice distortion generated in the structure during the large deformation processing as much as possible through low-temperature rapid annealing, thereby improving the success rate of grain corrosion.

[0034] (3) The grain corrosion method of the bonding silver wire provided by the present invention improves the clarity of microstructure observation, optimizes material performance evaluation, and increases the flexibility and adaptability of corrosion tests through a two-step corrosion process.

[0035] (4) The metallographic sample prepared by the grain etching method of the bonding silver wire provided by the present invention can make the boundaries between the grains distinct and the grain morphology clear by controlling the temperature and time of low-temperature rapid annealing, the composition of the first etching solution and the second etching solution, the time of the first etching and the second etching, and other parameters.

[0036] (5) The grain corrosion method of the bonding silver wire provided by the present invention is suitable for the grain corrosion and visualization of extremely fine bonding silver wires that have undergone large deformation, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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.

[0038] Figure 1 The optical microscope image of the metallographic sample obtained in Example 1;

[0039] Figure 2 The optical microscope image of the metallographic sample obtained in Example 2;

[0040] Figure 3 The optical microscope image of the metallographic sample obtained in Example 3;

[0041] Figure 4 The optical microscope image of the metallographic sample obtained in Example 4;

[0042] Figure 5 This is a light microscope image of the metallographic sample obtained in Example 5;

[0043] Figure 6 This is a light microscope image of the metallographic sample obtained in Example 6;

[0044] Figure 7 This is a light microscope image of the metallographic sample obtained in Example 7;

[0045] Figure 8 This is a light microscope image of the metallographic sample obtained in Example 8;

[0046] Fig. 9 This is a light microscopic image of the metallographic sample obtained in Example 9;

[0047] Fig.10 This is a light microscope image of the metallographic sample obtained in Example 10;

[0048] Fig.11 This is a light microscope image of the metallographic sample obtained in Comparative Example 1;

[0049] Fig.12 This is a light microscopic image of the metallographic sample obtained in Comparative Example 2;

[0050] Fig.13 This is a light microscopic image of the metallographic sample obtained in Comparative Example 3;

[0051] Fig.14 This is a light microscopic image of the metallographic sample obtained in Comparative Example 4;

[0052] Fig.15 This is a light microscopic image of the metallographic sample obtained in Comparative Example 5;

[0053] Fig.16 This is a light microscope image of the metallographic sample prepared in Comparative Example 6. DETAILED DESCRIPTION

[0054] 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.

[0055] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0056] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0057] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0058] In a first aspect, the present invention provides a method for etching the grains of a bonding silver wire, or a method for etching the grains of an extremely fine silver wire and its alloy wire, comprising the following steps:

[0059] The bonding silver wire that has been greatly deformed is subjected to low-temperature rapid annealing, and the annealed bonding silver wire is obtained after cooling.

[0060] Subsequently, a first etching solution is used to perform a first etching on the annealed bonding silver wire, and the surface of the annealed bonding silver wire is oxidized and / or sulfided to obtain a pre-etched bonding silver wire.

[0061] Among them, sulfidation is to enhance the surface contrast by generating silver sulfide (Ag2S), which is convenient for observing grain interfaces and surface details under a microscope. The reflection and scattering properties of the sulfide layer are different from those of the silver body, and this contrast difference can clearly highlight the grain boundaries and other structural features.

[0062] Then, a second etching solution is used to perform a second etching on the pre-etched bonding silver wire to reveal the microstructure.

[0063] In view of the difficulties in the current grain morphology corrosion of ultra-fine silver and its alloy bonding wires, the present invention provides a grain corrosion method for ultra-fine bonding silver wires, which can achieve effective corrosion of metallographic samples of ultra-fine bonding silver wires and reveal the microstructure morphology. The grain morphology is used to guide the bonding wire production process and bonding process. The problem that the existing corrosion method is basically difficult to etch out the grain morphology for large deformation tissues is solved.

[0064] Aiming at the problem of grain morphology corrosion of extremely fine silver and its alloy wires, the present invention proposes a method of step-by-step corrosion after heat treatment to relieve stress: the present invention first performs low-temperature rapid annealing on the bonding silver wire after large deformation. The low-temperature rapid annealing process can alleviate the accumulated tissue defects of the material during the large deformation production process, effectively reduce the degree of lattice distortion in the tissue, and improve the success rate of grain corrosion; after the annealing is completed, the silver and its alloy bonding wires that have undergone low-temperature rapid annealing are metallographically prepared, and corrosion is started after there are no scratches (no scratches indicate that the surface of the sample is flat and clean after grinding and polishing). The corrosion is divided into two steps, and the composition of the etching solution in each step is different. The main function of the first etching solution used in the first step of corrosion is to oxidize and / or sulfide the surface of the bonding silver wire to enhance the contrast of the microscopic results on the surface of the bonding wire, so as to facilitate the clear display of grain boundaries, defects and other microstructures. Then, the second etching solution is used to perform the second step of corrosion to reveal the complex structure of silver and its alloys.

[0065] More specifically, the purpose of the low temperature rapid annealing of the present invention is to eliminate the lattice distortion generated in the structure during the large deformation process as much as possible, that is, stress relief annealing. In this process, due to the thermal movement of point defects and dislocations, the density of both is significantly reduced, so that the degree of lattice distortion in the structure is reduced, and the success rate of grain etching is improved.

[0066] The present invention comprises two steps of etching, wherein in the first step of etching, after oxidation and / or sulfidation treatment, a uniform corrosion layer will be formed on the surface of the sample; in the second step of etching, on the one hand, part of the surface layer can be selectively removed to make the grain boundary more obvious, and on the other hand, the corrosion rate and depth can be more accurately controlled during further etching to avoid excessive damage caused by one-time strong corrosion.

[0067] The metallographic specimen prepared by the etching method provided by the present invention has distinct boundaries between grains and clear grain morphology. It can be seen that the grain etching method of bonding silver wire provided by the present invention is suitable for the etching and visualization of grains of extremely fine silver and its alloy wires that have undergone large deformation.

[0068] In some specific embodiments, the diameter of the bonding silver wire after large deformation is 15 to 30 μm, including but not limited to any point value of 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 28 μm, and 30 μm, or a range value between any two of them.

[0069] The prior art lacks a method for etching the grains of extremely fine silver and its alloy wires, while the grain etching method provided by the present invention is suitable for extremely fine bonding silver wires with a diameter of 15 to 30 μm and can reveal clear grain morphology.

[0070] In some specific embodiments, the large deformation method includes drawing, and the drawing method includes: first drawing to a material diameter of 8mm to 1.3mm (for example, 6mm, 5mm or 3mm), then medium drawing to a material diameter of 1.3mm to 81.5μm (for example, 1mm, 800μm, 500μm, 300μm, 100μm or 90μm), then fine drawing to a material diameter of 81.5μm to 30μm (for example, 80μm, 60μm, 50μm or 40μm), and finally micro-pulling to a material diameter of 30μm to 15μm (for example, 25μm or 20μm).

[0071] In some specific embodiments, the annealing temperature of the low-temperature rapid annealing is 200-250°C, including but not limited to any point value of 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or a range between any two of them.

[0072] Among them, since the recrystallization temperature of Ag is about 250°C, in order to achieve the purpose of significantly reducing lattice distortion while preventing recrystallization, the temperature needs to be controlled below 250°C. Since the diameter of the bonding silver wire is at the micron level, the thinnest can reach more than ten microns, so the temperature and time of low-temperature rapid annealing need to be strictly controlled.

[0073] In some specific embodiments, the annealing time of the low-temperature rapid annealing is 0.3-0.5 s, including but not limited to any one of 0.3 s, 0.35 s, 0.4 s, 0.45 s, and 0.5 s or a range between any two of them.

[0074] It is understandable that the low-temperature rapid annealing process corresponding to the bonding silver wires of different wire diameters is different. As the wire diameter of the bonding silver wire increases, the annealing time can be appropriately increased. However, the annealing time should not be too long, because the wire diameter of the bonding silver wire is very thin, and a long annealing time will cause the grains to grow.

[0075] In some specific embodiments, the first etching solution is mainly prepared by mixing a hydrogen peroxide solution and an ammonia solution in a volume ratio of 0.95 to 1.05:1. The volume ratio of the hydrogen peroxide solution to the ammonia solution can be 0.95:1, 0.98:1, 1:1, 1.02:1 or 1.05:1.

[0076] The function of the first etching solution is to oxidize and / or sulfide the surface of the bonding silver wire after annealing, so as to form a uniform etching layer on the surface of the bonding silver wire after annealing, which is conducive to clearly showing the grains.

[0077] In some specific implementations, the mass fraction of the hydrogen peroxide solution is 2.5% to 3.5%, for example, 3%.

[0078] In some specific embodiments, the mass fraction of the ammonia solution is 25% to 28%, such as 26% or 27%. The mass fraction of the ammonia solution refers to the mass percentage concentration of ammonia (NH3) in the solution, that is, the mass of ammonia accounts for the percentage of the total mass of the solution.

[0079] In some specific implementations, the first etching solution includes a nitric acid solution with a mass fraction of 3% to 5%, for example, a 4% nitric acid solution.

[0080] In some specific embodiments, the first etching solution is mainly prepared by mixing a nitric acid solution with a mass fraction of 1.5% to 2.5% (e.g., 2%) and a chloric acid solution with a mass fraction of 0.3% to 0.8% (e.g., 0.5%). The volume ratio of the nitric acid solution to the chloric acid solution is 0.95 to 1.05:1, such as 0.95:1, 0.98:1, 1:1, 1.02:1 or 1.05:1.

[0081] In some specific embodiments, the first etching solution includes a sodium thiosulfate solution with a mass fraction of 0.1% to 1%, such as a 0.3%, 0.5% or 0.8% sodium thiosulfate solution.

[0082] In some specific embodiments, the first etching solution is mainly prepared by mixing a sulfuric acid solution having a mass fraction of 0.05% to 0.15% (e.g., 0.1%) and a sodium thiosulfate solution having a mass fraction of 0.3% to 0.8% (e.g., 0.5%). The volume ratio of the sulfuric acid solution to the sodium thiosulfate solution is 0.95 to 1.05:1, such as 0.95:1, 0.98:1, 1:1, 1.02:1 or 1.05:1.

[0083] In some specific embodiments, the second etching solution is mainly composed of a potassium cyanide solution and an ammonium persulfate solution in a mass ratio of 0.95 to 1.05:1, wherein the mass ratio may be 0.95:1, 0.98:1, 1:1, 1.02:1 or 1.05:1.

[0084] After the second etching solution is used for etching, silver and its complex alloy structure can be clearly revealed.

[0085] In some specific implementations, the mass fraction of the potassium cyanide solution is 18.5% to 21.5%, for example 20%.

[0086] In some specific embodiments, the mass fraction of the ammonium persulfate solution is 18.5% to 21.5%, for example 20%.

[0087] In some specific embodiments, when the first etching solution is mainly prepared by mixing a hydrogen peroxide solution and an ammonia solution in a volume ratio of 0.95 to 1.05:1, the first etching time is ≤ 60s; including but not limited to any point value of 60s, 59s, 58s, 57s, 56s, 55s, 53s, 52s, 50s, 48s, 45s, 43s, 40s, 37s, 35s, 33s, 30s, 25s, 20s, 15s or any range value between two of them; preferably 15 to 60s. The first etching time should not be too long, otherwise it will cause excessive corrosion on the surface of the sample, blackening the structure, and making it unclear.

[0088] In some specific embodiments, when the first etching solution is a 3% to 5% nitric acid solution, a 0.1% to 1% sodium thiosulfate solution by mass, a solution mainly prepared by mixing a 1.5% to 2.5% nitric acid solution with a 0.3% to 0.8% chloric acid solution by mass, or a solution mainly prepared by mixing a 0.05% to 0.15% sulfuric acid solution with a 0.3% to 0.8% sodium thiosulfate solution by mass, the time of the first etching can be set according to actual conditions.

[0089] In some specific embodiments, the first etching method includes: immersing the annealed bonding silver wire in the first etching solution. In some specific embodiments, after the immersion is completed, the immersed bonding silver wire is taken out, rinsed with clean water, and wiped with ethanol to remove excess first etching solution on the surface of the immersed bonding silver wire to obtain a pre-etched bonding silver wire.

[0090] In some specific embodiments, when the second etching solution is mainly composed of a potassium cyanide solution and an ammonium persulfate solution in a mass ratio of 0.95 to 1.05:1, the second etching time is 30 to 60 seconds, including but not limited to any point value of 30 seconds, 33 seconds, 35 seconds, 38 seconds, 40 seconds, 42 seconds, 45 seconds, 48 ​​seconds, 50 seconds, 42 seconds, 55 seconds, 58 seconds, and 60 seconds, or a range value between any two of them. The second etching time should not be too long, otherwise it will cause excessive corrosion on the sample surface, blackening of the structure, and unclearness.

[0091] In some specific implementations, the second etching method includes: dipping cotton in the second etching solution and then wiping the surface of the pre-etched bonding silver wire.

[0092] The first etching and the second etching methods in the present invention are different because the first etching solution and the second etching solution have different corrosion strengths. The second etching is more corrosive, so a wiping method is adopted.

[0093] In some specific implementations, after the second etching, the surface is rinsed with clean water and wiped with ethanol to remove excess of the second etching solution.

[0094] The present invention can make the boundaries between the grains distinct and the grain morphology clear by controlling the temperature and time of low-temperature rapid annealing, the composition of the first etching solution and the second etching solution, the time of the first etching and the second etching, and other parameters.

[0095] In some specific embodiments, the silver bonding wire includes a silver bonding wire and / or a silver alloy bonding wire.

[0096] It is understandable that corrosion is mainly achieved by chemically reacting the corrosive liquid with the metal material to generate related substances to increase contrast, which is beneficial to morphological observation. The corrosive liquid components corresponding to metal materials of different compositions are different. The grain corrosion method of the bonding silver wire of the present invention is applicable to silver-containing materials, including metallic silver and silver alloys.

[0097] In a second aspect, the present invention provides application of the grain corrosion method of the bonding silver wire in preparing the bonding silver wire.

[0098] By observing the metallographic specimen of the ultra-fine bonding silver wire after the above-mentioned grain corrosion method of the bonding silver wire, and observing the size and distribution of the grains, the production process of the ultra-fine bonding silver wire can be regulated and its bonding performance can be predicted. First, the clear grain morphology can make the judgment of the heat-affected zone of the material after the melt ball more accurate, so as to more accurately regulate the melt ball process. Secondly, smaller grains usually mean higher bonding strength, but fine grains will increase the number of grain boundaries. The increase in the number of grain boundaries will hinder the migration of electrons and affect the conductivity of the bonding wire. The morphology of the grains also has a certain influence on the high-temperature service performance of the bonding wire. Equiaxed grains are isotropic, while columnar crystals have larger thermal expansion values ​​in specific directions. Therefore, it is necessary to regulate the production process of ultra-fine bonding silver wire according to the morphology and distribution of the grains, and coordinately regulate the drawing process and the heat treatment process to obtain ultra-fine bonding silver wire products with appropriate grain size and uniform distribution.

[0099] Therefore, the grain corrosion method of the bonding silver wire provided by the present invention is suitable for the grain corrosion and visualization of extremely fine silver and its alloy wires that have undergone large deformation, and has broad application prospects.

[0100] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0101] Example 1

[0102] The method for etching the grains of the bonding silver wire provided in this embodiment comprises the following steps:

[0103] (1) The silver alloy bonding wire (with a diameter of 30 μm) after large deformation is subjected to low-temperature rapid annealing, wherein the large deformation method includes drawing, and the drawing method includes: firstly large-scale drawing to a material diameter of 8 mm, then medium-scale drawing to a material diameter of 1 mm, then fine-scale drawing to a material diameter of 50 μm, and finally micro-drawing to a material diameter of 30 μm, the annealing temperature is 250° C., and the annealing time is 0.5 s, to obtain the annealed bonding silver wire.

[0104] (2) After cotton is dipped in the first etching solution, the surface of the annealed bonding silver wire is wiped to perform the first etching to oxidize the surface of the annealed bonding silver wire, wherein the first etching solution is composed of a hydrogen peroxide solution (mass fraction is 3%) and an ammonia solution (mass fraction is 26%) in a volume ratio of 1:1. During the first etching, the cotton is wiped for 60 seconds, and then the excess first etching solution on the surface of the annealed bonding silver wire is cleaned with anhydrous ethanol to obtain a pre-etched bonding silver wire.

[0105] (3) After cotton is dipped in the second etching solution, the surface of the pre-etched bonding silver wire is wiped to perform the second etching, wherein the second etching solution is composed of a potassium cyanide solution (mass fraction of 20%) and an ammonium persulfate solution (mass fraction of 20%) in a mass ratio of 1:1. During the second etching, the cotton is wiped for 60 seconds to reveal the silver and its complex alloy structure. After that, the excess second etching solution on the surface of the pre-etched bonding silver wire is cleaned with anhydrous ethanol to obtain a metallographic sample.

[0106] like Figure 1 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0107] Example 2

[0108] The grain corrosion method of the bonding silver wire provided in this embodiment is basically the same as that in Embodiment 1, except that: in step (1), the diameter of the silver alloy bonding wire after large deformation is 15 μm, and the drawing method includes: firstly large pulling to a material diameter of 5 mm, then medium pulling to a material diameter of 1.3 mm, then fine pulling to a material diameter of 80 μm, and finally micro-pulling to a material diameter of 15 μm, and the annealing time is 0.3 s.

[0109] like Figure 2 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0110] Example 3

[0111] The grain etching method for bonding silver wires provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the annealing temperature is 200° C. and the annealing time is 0.4 s.

[0112] like Figure 3 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0113] Example 4

[0114] The grain etching method for bonding silver wires provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the annealing temperature is 225°C.

[0115] like Figure 4 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0116] Example 5

[0117] The grain etching method for bonding silver wires provided in this embodiment is basically the same as that in Embodiment 1, except that in step (2), the volume ratio of the hydrogen peroxide solution to the ammonia solution is replaced with 0.95:1.

[0118] like Figure 5 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0119] Example 6

[0120] The grain etching method of the bonding silver wire provided in this embodiment is basically the same as that in Embodiment 1, except that: in step (2), cotton is used to wipe for 30 seconds during the first etching.

[0121] like Figure 6 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0122] Example 7

[0123] The grain etching method for bonding silver wires provided in this embodiment is basically the same as that in Embodiment 1, except that in step (3), the mass ratio of potassium cyanide solution to ammonium persulfate solution is replaced with 1.05:1.

[0124] like Figure 7 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0125] Example 8

[0126] The grain etching method of the bonding silver wire provided in this embodiment is basically the same as that in Embodiment 1, except that: in step (3), cotton is used to wipe for 30 seconds during the second etching.

[0127] like Figure 8 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0128] Example 9

[0129] The grain etching method for bonding silver wires provided in this embodiment is basically the same as that in Embodiment 1, except that: in step (2), the first etching solution is replaced by a mixed solution of sulfuric acid and sodium thiosulfate, wherein the mixed solution is prepared by mixing a sulfuric acid solution with a mass fraction of 1% and a sodium thiosulfate solution with a mass fraction of 0.5%, and the volume ratio of the sulfuric acid solution to the sodium thiosulfate solution is 1:1.

[0130] like Fig. 9 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0131] Example 10

[0132] The grain corrosion method of the silver bonding wire provided in this embodiment is basically the same as that in Embodiment 1, except that in step (1), the silver alloy bonding wire (with a diameter of 30 μm) that has undergone a large deformation is replaced by a silver bonding wire that has undergone a large deformation and has a diameter of 20 μm.

[0133] like Fig.10 The optical microscope image of the metallographic sample prepared in this embodiment is shown. It can be seen that the boundaries between the grains are clearly defined and the grain morphology is clear.

[0134] Comparative Example 1

[0135] The grain corrosion method of the silver bonding wire provided in this comparative example is basically the same as that in Example 1, except that: low-temperature rapid annealing is not performed in step (1), but the silver alloy bonding wire that has undergone a large deformation is directly subjected to the first corrosion of step (2).

[0136] like Fig.11 The optical microscope image of the metallographic sample prepared in this comparative example is shown. It can be seen that the residual stress in the structure of comparative example 1 is large, the lattice distortion is serious, and the structure morphology after corrosion is blurred.

[0137] Comparative Example 2

[0138] The grain corrosion method of the bonding silver wire provided in this comparative example is basically the same as that in Example 1, except that in step (1), the annealing temperature is 300° C. and the annealing time is 2 s.

[0139] like Fig.12 The optical microscope image of the metallographic sample prepared in this comparative example is shown. It can be seen that the increase in annealing temperature and time in comparative example 2 causes the grains to grow seriously and changes the original structure morphology.

[0140] Comparative Example 3

[0141] The grain etching method of the bonding silver wire provided in this comparative example is basically the same as that of Example 1, except that step (2) is not performed, and instead the second etching of step (3) is directly performed on the surface of the bonding silver wire after annealing.

[0142] like Fig.13 The optical microscope image of the metallographic sample prepared in this comparative example is shown. It can be seen that in comparative example 3, only one step of etching was performed, and the etching morphology was not sufficient.

[0143] Comparative Example 4

[0144] The grain etching method of the bonding silver wire provided in this comparative example is basically the same as that of Example 1, except that step (3) is not performed and cotton is used for wiping for 2 minutes during the first etching.

[0145] like Fig.14 Shown is the optical microscopic image of the metallographic sample obtained in this comparative example. It can be seen that comparative example 4 is over-corroded.

[0146] Comparative Example 5

[0147] The grain etching method of the bonding silver wire provided in this comparative example is basically the same as that in Example 1, except that: in step (2), cotton is used to wipe for 120 seconds during the first etching.

[0148] like Fig.15 Shown is the optical microscopic image of the metallographic sample obtained in this comparative example. It can be seen that comparative example 5 is over-corroded.

[0149] Comparative Example 6

[0150] The grain etching method of the bonding silver wire provided in this comparative example is basically the same as that of Example 1, except that in step (3), the second etching solution is an ammonium persulfate solution (mass fraction is 20%).

[0151] like Fig.16 The light micrograph of the metallographic sample prepared in this comparative example is shown. It can be seen that the corrosion of comparative example 6 is not sufficient and the structure contrast is not obvious enough.

[0152] In summary, the grain corrosion method of the bonding silver wire provided by the present invention can achieve effective corrosion of the metallographic sample of the extremely fine bonding silver wire after large deformation, revealing the microstructure morphology.

[0153] Furthermore, the present invention can make the boundaries between the grains distinct and the grain morphology clear by controlling the temperature and time of low-temperature rapid annealing, the composition of the first etching solution and the second etching solution, the time of the first etching and the second etching, and other parameters.

[0154] 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 method for grain corrosion of a bonding silver wire, characterized in that: The steps include: Performing low-temperature rapid annealing on the bonding silver wire after the large deformation to obtain the annealed bonding silver wire; Using a first etching solution to perform a first etching on the annealed silver bonding wire, oxidizing and / or sulfiding the surface of the annealed silver bonding wire to obtain a pre-etched silver bonding wire; The pre-etched bonding silver wire is subjected to a second etching process using a second etching solution to reveal the microstructure.

2. The method for grain etching of bonding silver wire according to claim 1, characterized in that: The diameter of the bonding silver wire after the large deformation is 15 to 30 μm.

3. The method for grain etching of bonding silver wire according to claim 1, characterized in that: The large deformation method includes drawing, and the drawing method includes: firstly large drawing to a material diameter of 8mm-1.3mm, then medium drawing to a material diameter of 1.3mm-81.5μm, then fine drawing to a material diameter of 81.5μm-30μm, and finally micro-drawing to a material diameter of 30μm-15μm.

4. The method for grain etching of bonding silver wire according to claim 1, characterized in that: At least one of the following conditions is met: (1) The annealing temperature of the low-temperature rapid annealing is 200-250° C.; (2) The annealing time of the low-temperature rapid annealing is 0.3 to 0.5 s.

5. The method for grain etching of bonding silver wire according to claim 1, characterized in that: At least one of the following conditions is met: (1) The first etching solution is mainly prepared by mixing a hydrogen peroxide solution and an ammonia solution in a volume ratio of 0.95 to 1.05:1; wherein the mass fraction of the hydrogen peroxide solution is 2.5% to 3.5%, and the mass fraction of the ammonia solution is 25% to 28%; (2) the first etching solution comprises a nitric acid solution with a mass fraction of 3% to 5%; (3) The first etching solution is mainly prepared by mixing a nitric acid solution with a mass fraction of 1.5% to 2.5% and a chloric acid solution with a mass fraction of 0.3% to 0.8%, wherein the volume ratio of the nitric acid solution to the chloric acid solution is 0.95 to 1.05:1; (4) the first etching solution comprises a sodium thiosulfate solution having a mass fraction of 0.1% to 1%; (5) The first etching solution is mainly prepared by mixing a sulfuric acid solution with a mass fraction of 0.05% to 0.15% and a sodium thiosulfate solution with a mass fraction of 0.3% to 0.8%; wherein the volume ratio of the sulfuric acid solution to the sodium thiosulfate solution is 0.95 to 1.05:

1.

6. The method for grain etching of bonding silver wire according to claim 1, characterized in that: The second etching solution is mainly composed of a potassium cyanide solution and an ammonium persulfate solution in a mass ratio of 0.95 to 1.05:1; wherein the mass fraction of the potassium cyanide solution is 18.5% to 21.5%, and the mass fraction of the ammonium persulfate solution is 18.5% to 21.5%.

7. The method for grain etching of bonding silver wire according to claim 1, characterized in that: At least one of the following conditions is met: (1) The first corrosion time is ≤ 60 s; (2) The first etching method comprises: immersing the annealed bonding silver wire in the first etching solution; (3) After the soaking is completed, the soaked bonding silver wire is taken out, washed with water and wiped with ethanol to remove excess of the first etching solution on the surface of the soaked bonding silver wire, thereby obtaining a pre-etched bonding silver wire.

8. The method for grain etching of bonding silver wire according to claim 1, characterized in that: At least one of the following conditions is met: (1) The second corrosion time is 30 to 60 seconds; (2) The second etching method comprises: using cotton to dip into the second etching solution and then wiping the surface of the pre-etched bonding silver wire; (3) After the second etching, wash with water and wipe with ethanol to remove excess of the second etching solution.

9. The method for grain etching of bonding silver wire according to any one of claims 1 to 8, characterized in that: The silver bonding wire includes a silver bonding wire and / or a silver alloy bonding wire.

10. Use of the grain etching method for bonding silver wire according to any one of claims 1 to 9 in preparing bonding silver wire.

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