Performance improvement method and application of bonding wire

Abstract

The invention provides a bonding wire performance improvement method and application, and relates to the technical field of bonding wires. Specifically, the method comprises the following steps: annealing and carburizing the cast and drawn bonding wire at the same time; then circulating subzero treatment is carried out; washing treatment is carried out through a chemical washing agent and hot water in sequence, and the bonding wire with improved performance is obtained after drying. According to the performance improvement method, the defects that the bonding wire is prone to breaking in the using process, annealing is uneven in the annealing process, the annealing efficiency is low, and the bonding wire is oxidized in the storing, transporting and using processes can be overcome at the same time, the mechanical strength and the yield of the bonding wire can be effectively improved through the performance improvement method, and good application prospects are achieved.

Description

Technical Field

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

[0002] With the development of the integrated circuit manufacturing and packaging industries, the demand for bonding wires, one of the four basic materials for semiconductor packaging, is increasing. The vigorous development of microelectronics has continuously promoted chips to high performance, high density and miniaturization, thus putting higher requirements on the bonding wires as inner leads between the chip and the frame.

[0003] Bonding wires are usually made of metals such as copper, aluminum, silver, and gold, and can be connected to electronic components through various methods such as welding, crimping, and gluing. The traditional bonding wire preparation process usually includes: first, the selected metal raw material or alloy is smelted and cast into a preliminary rod or wire material, and then the preliminary rod or wire material is gradually drawn into a thin wire that meets the requirements through multiple drawing processes. However, the above preparation process usually has the following problems: (1) the bonding wire has a large internal stress after drawing; (2) the bonding wire is prone to jump wires, break wires, and cracks during the winding process; (3) the bonding wire is prone to oxidation during storage and transportation, which affects the subsequent performance of the bonding wire.

[0004] In response to the above problems, the following methods are usually used to solve them: (1) Annealing can reduce internal stress; however, conventional annealing methods usually cause uneven annealing due to uneven temperature in the furnace, which makes it easier to generate greater internal stress. After annealing, only annealing liquid is used to anneal the bonding wire, which can easily cause serious surface contamination of the bonding wire; (2) In order to avoid wire breakage, it is necessary to increase the toughness of the bonding wire through post-processing; (3) For example, in patent application CN202110522033.2, wax spraying is used to perform anti-oxidation treatment on the surface of the bonding wire; however, the bonding strength between the coating and the bonding wire is insufficient, and problems such as coating shedding are prone to occur.

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

[0006] The first object of the present invention is to provide a method for improving the performance of bonding wires, aiming to simultaneously solve the defects of bonding wires being prone to wire breakage during use, as well as the defects of uneven annealing during the current bonding wire preparation process, which results in insignificant internal stress elimination, and the bonding wires being prone to oxidation during storage.

[0007] The second object of the present invention is to provide an application of the bonding wire performance improvement method in bonding wires.

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

[0009] A method for improving the performance of a bonding wire comprises the following steps:

[0010] (1) annealing and carburizing the bond wires after casting and drawing at the same time;

[0011] (2) subjecting the bonding wire treated in step (1) to a cyclic cryogenic treatment;

[0012] (3) The bonding wire treated in step (2) is sequentially washed with a chemical detergent and hot water, and dried to obtain a bonding wire with improved performance.

[0013] The method for improving the performance of bonding wires is used in bonding wires.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention provides a performance improvement treatment process for bonding wires, which mainly includes simultaneous annealing treatment and carburizing treatment, as well as cyclic cryogenic treatment, and washing treatment performed independently by two media. It can effectively reduce the probability of quality defects such as broken wires and oxidation of bonding wires, and effectively enhance the overall quality of bonding wires, including wear resistance, oxidation resistance, toughness and other effects.

[0016] (2) The present invention is based on an optimization and upgrade of the current annealing method, and has the advantages of high heat transfer efficiency and uniform annealing, while almost avoiding the oxidation loss of annealing and having lower cost; furthermore, the mechanical strength of the bonding wire is enhanced through carburizing strengthening modification, and a carburized layer is formed by the diffusion of carbon atoms during annealing, thereby improving the wear resistance and oxidation resistance of the bonding wire.

[0017] (3) The present invention first proposes to use cyclic deep cryogenic treatment to post-treat the bonding wire, which can significantly refine the grains, increase the dislocation density, reduce the residual stress, strengthen the matrix, and significantly increase the fracture toughness and hardness of the bonding wire.

[0018] (4) The present invention uses two different media for cleaning. On the one hand, a chemical cleaning agent is used to clean the annealed bonding wire to remove the oxide layer or foreign matter on the surface of the bonding wire, ensuring a more thorough cleaning while reducing the pulling resistance; on the other hand, hot water can more easily remove impurities on the surface of the bonding wire, thereby improving the cleanliness of the bonding wire surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a SEM image of the bonding wire surface of Comparative Example 1 of the present invention;

[0021] Figure 2 This is a SEM image of the bonding wire surface of Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, it will be understood by those skilled in the art that the following embodiments are only some 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 conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially. In addition, the terms "one", "two", and "1" are only used for descriptive purposes and are not to be understood as indicating or implying relative importance.

[0023] The first aspect of the present invention is to provide a method for improving the performance of a bonding wire, which mainly includes the following steps (1) to (3).

[0024] First, the bonding wire objects to which the present invention is applicable are explained: the "bonding wire after casting and drawing" refers to the bonding wire that has undergone conventional alloy melting, casting, shaping, and drawing, but has not been annealed; the present invention does not impose any restrictions on the composition of the bonding wire, including but not limited to metals such as gold, silver, copper, zinc, or other non-metallic modified components; the present invention also does not impose any strict restrictions on the pre-process flow of the bonding wire. However, since the performance improvement method of the present invention does not include a diameter reduction treatment, the bonding wire should already have a preset diameter before performing the performance improvement method.

[0025] (1) The bonding wires after casting and drawing are subjected to annealing and carburizing treatment simultaneously.

[0026] As a preferred embodiment, step (1) is carried out in a salt bath or sand bath environment; it is worth noting that the annealing treatment and the carburizing treatment are carried out synchronously in the salt bath or sand bath environment.

[0027] As a more preferred embodiment, the salt bath medium includes at least one of sodium chloride, potassium chloride, barium chloride, calcium chloride, sodium nitrate, potassium nitrate, sodium nitrite, or potassium nitrite. A person skilled in the art can select one or more of the above salts and adjust the proportions of the salt components to obtain a salt bath medium with different melting points suitable for a specific annealing temperature. It is worth noting that among the salt bath mediums provided by the present invention, some have relatively low melting points, such as sodium nitrite, which has a melting point of approximately 271°C. Such low-melting-point mediums are generally not used independently as the salt bath medium, but are used in combination with other high-melting-point mediums for macro-control of temperature.

[0028] As a more preferred embodiment, the medium of the sand bath includes but is not limited to at least one of quartz sand, yellow sand, fine sea sand or desert sand.

[0029] As a preferred embodiment, the annealing temperature is 400°C to 500°C, including but not limited to any one of 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, and 500 (°C) or a numerical range consisting of any two of them.

[0030] As a more preferred embodiment, the annealing treatment includes: continuously feeding the wire into the temperature environment of the annealing treatment; which can be understood as continuously inputting and outputting the wire into the temperature environment of the annealing treatment; the wire feeding speed is 0.5m / s to 1.0m / s.

[0031] As a more preferred embodiment, the heat treatment time of the annealing treatment is 1 hour to 3 hours, and the length of the annealing chamber is 3 meters to 5 meters.

[0032] As a preferred embodiment, the carburizing treatment includes: adding a carbon raw material into the solid medium environment of step (1), wherein the carbon raw material includes carbide and carbonate; in some optional embodiments, the carbide includes at least one of carbides such as silicon carbide, boron carbide, sodium carbide, calcium carbide, titanium carbide, and zirconium carbide, and the carbonate includes at least one of carbonates such as sodium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, copper carbonate, zinc carbonate, iron carbonate, and sodium bicarbonate.

[0033] As a more preferred embodiment, the mass ratio of the carbide to the carbonate is 85-95:5-15.

[0034] As a more preferred embodiment, the mass ratio of the solid phase medium to the carbon raw material is 80-85:15-20.

[0035] As a more preferred embodiment, before performing step (1), the solid phase medium and the carbon raw material are fully mixed. This step can be performed in any stirring device for solid phase materials.

[0036] As a preferred embodiment, step (1) is carried out in a heat treatment device, which is assembled from a heat preservation unit, a transmission unit, a heating unit and a temperature control system; wherein the heating unit includes but is not limited to a plurality of thermocouples or thermal resistors, and the temperature control system includes but is not limited to thermistors, temperature measuring chips, etc.

[0037] (2) The bonding wires processed in step (1) are subjected to cyclic cryogenic treatment.

[0038] As a preferred embodiment, the cyclic cryogenic treatment uses liquid nitrogen as a refrigerant, and the cyclic cryogenic treatment includes: cyclically lowering and raising the temperature within a temperature range, wherein the upper and lower limits of the temperature range correspond to the upper and lower limits of the temperature cycle, respectively; specifically, the lower limit of the cycle temperature is -160°C to -140°C, and the upper limit of the cycle temperature is 15°C to 30°C; in some preferred embodiments, the number of cycles is 3 to 5 times.

[0039] As a more preferred embodiment, the cyclic cryogenic treatment starts from -100°C, cools to the lower limit of the cyclic temperature, and then heats to the upper limit of the cyclic temperature, which constitutes one cycle; the above operation is repeated 3 to 5 times in total.

[0040] As a more preferred embodiment, the time of each cycle of the cyclic cryogenic treatment includes a temperature drop section and a temperature rise section, the temperature rise section lasts for 0.4h to 0.8h, and the temperature drop section lasts for 1.5h to 3h.

[0041] As a more preferred embodiment, the cyclic cryogenic treatment operation includes the following steps: immersing the bonding wire in liquid nitrogen to achieve deep cooling, and placing the bonding wire in room temperature air to achieve heating.

[0042] (3) The bonding wire treated in step (2) is sequentially washed with a chemical detergent and hot water, and dried to obtain a bonding wire with improved performance.

[0043] As a preferred embodiment, the chemical wash comprises at least one of a borax solution, a potassium fluoroborate solution or an acid solution; in some more preferred embodiments, the solute of the chemical wash comprises at least one of borax, sodium tetraborate decahydrate, fluoroboric acid, potassium fluoroborate, sodium fluoroborate, copper fluoroborate, dilute sulfuric acid, dilute nitric acid or citric acid, and the solvent of the chemical wash includes but is not limited to water.

[0044] As a more preferred embodiment, the concentration of the chemical detergent is 2.5wt.% to 10wt.%, including but not limited to any one of 2.5, 3, 4, 5, 6, 7, 8, 8.5, 9, 9.5, 10 (wt.%) or a numerical range consisting of any two of them.

[0045] In a preferred embodiment, the chemical cleaning treatment includes unwinding the bonding wire at a speed of 0.5 m / s to 1 m / s, passing the bonding wire through the chemical cleaning agent. In other optional embodiments, the cleaning treatment may also be performed by thoroughly immersing the bonding wire in the chemical cleaning agent or spraying the chemical cleaning agent onto the surface of the bonding wire.

[0046] As a preferred embodiment, the temperature of the hot water is 70°C to 90°C.

[0047] As a preferred embodiment, the drying temperature is 150° C. to 200° C., and the drying time is 0.3 h to 2 h.

[0048] In a preferred embodiment, the drying is performed in a heat treatment device comprising a heat preservation unit, a transmission unit, a heating unit, and a temperature control system. The heating unit includes, but is not limited to, several infrared heating devices and a high-temperature-resistant blower, and the temperature control system includes, but is not limited to, a thermistor and a temperature measurement chip. In an optional embodiment, the heating unit is embedded within the heat treatment device to prevent contamination and damage to the heating unit from the liquid environment and to increase temperature measurement accuracy.

[0049] A second aspect of the present invention is to provide use of the bonding wire performance improvement method according to the first aspect in bonding wires.

[0050] It can be understood that the performance improvement method of the bonding wire described in the present invention can also be understood as a post-processing method of the bonding wire. Therefore, in the use of the second aspect, on the basis of adopting the performance improvement method, it includes but is not limited to a bonding wire preparation method, a bonding wire prepared based on the performance improvement method, and a bonding wire-related semiconductor packaging method, etc.; it is worth noting that in the use, the performance improvement method can be a coherent and independent operation unit, or the operation process of the performance improvement method can be intermittently interspersed; when containing the performance improvement method, any product or method can be used as an implementation method of the use of the present invention.

[0051] Example 1

[0052] (1) The finished Cu bonding wire is buried in a mixed salt, which includes a base salt of sodium nitrate and potassium nitrate (mass ratio = 1:1) and a carburizing agent of sodium carbonate and silicon carbide (mass ratio = 85:15). The mass ratio of the base salt to the carburizing agent is 80:20. The mixed salt is heated to 500°C and the heat treatment time is 1 hour. The bonding wire is annealed to remove stress and the carburizing treatment is achieved at a high temperature.

[0053] (2) The bonding wire is introduced into a liquid nitrogen freezing device, starting from room temperature (in the processing environment of each embodiment of the present invention, the room temperature is 25°C), cooled to -150°C, and then heated to room temperature. This is considered one cycle, and a total of three cycles of cryogenic treatment are performed.

[0054] (3) The bonding wires derived from the cryogenic circulation device are introduced into a cleaning furnace containing a chemical cleaning agent for cleaning. The chemical reagent is a 2.5 wt.% borax aqueous solution.

[0055] (4) Use a hot water bath at 80°C to thoroughly clean the surface of the bonding wire, and use a drying oven at 180°C to dry the bonding wire.

[0056] Example 2

[0057] The method is basically the same as Example 1, with the only difference being that Ag bonding wire is used to replace the initial Cu bonding wire.

[0058] Example 3

[0059] The method is basically the same as Example 1, with the only difference being that the original Cu bonding wire is replaced by an Au bonding wire.

[0060] Example 4

[0061] It is basically the same as Example 1, except that in step (1), the bonding wire is buried in the mixed sand, which includes yellow sand as the base sand and a carburizing agent of sodium carbonate and silicon carbide (mass ratio = 9:1), and the mass ratio of the base sand to the carburizing agent is 85:15.

[0062] Example 5

[0063] It is basically the same as Example 1, with the only difference being that the cryogenic cycle is replaced with a 4-cycle cycle.

[0064] Example 6

[0065] It is basically the same as Example 1, with the only difference being that the cryogenic cycle is replaced with a 5-cycle cycle.

[0066] Example 7

[0067] The method is basically the same as Example 1, except that: in step (1), the base salt is replaced by sodium chloride and potassium chloride (mass ratio = 4:6); in step (3), the 2.5 wt.% borax aqueous solution is replaced by a 5 wt.% potassium fluoroborate solution.

[0068] Comparative Example 1

[0069] The method is basically the same as Example 1, except that: step (1) is replaced as a whole by placing the finished Cu bonding wire in a conventional annealing furnace (model: KSL-1400XA1 (UL)), heating it to 500°C, and heat treating it for 1 hour to anneal the bonding wire to remove stress.

[0070] Comparative Example 2

[0071] The process is basically the same as Example 1, except that no carburizing agent is added in step (1).

[0072] Comparative Example 3

[0073] The method is basically the same as Example 1, with the only difference being that step (2) is eliminated.

[0074] Test example

[0075] (a) Tensile strength: The test method is based on the standard "HB5177-1996 Metal Wire Tensile Test Method".

[0076] (b) Elongation: The test method is based on the standard "HB5177-1996 Metal Wire Tensile Test Method".

[0077] (c) Hardness: The bond wire hardness was tested using a Shimadzu ultramicro dynamic hardness tester (model DUH-211 / 211S).

[0078] (d) Antioxidant Ability: The oxidation time of the bonding wire was tested using the mass change method at room temperature. The method is as follows: using an electronic balance, the bonding wire samples of each embodiment and comparative example were weighed with the same mass; the samples were placed in a test tube or beaker, and appropriate amounts of ammonia water, hydrogen peroxide solution, and acidic sodium silicate solution were added to form a reaction system, which was then allowed to stand; the mass of the bonding wire was measured after the same time interval (7 days), and the degree of oxidation was evaluated by calculating the percentage of mass loss under the same treatment time.

[0079] The results of this test example are recorded in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] As can be seen from Table 1, the embodiments of the present invention, after subjecting the bonding wire to carburizing-annealing, cyclic deep cooling, and special cleaning, obtain bonding wires with higher tensile properties, elongation, hardness, and oxidation resistance than the comparative examples. These bonding wires can be used as post-processing processes for conventional bonding wires or as an improvement to conventional bonding wire production processes, and have significant improvements and good application prospects.

[0084] Furthermore, Figure 1 、 Figure 2 Scanning electron microscope test images of the bonding wires of Comparative Example 1 and Example 1 of the present invention are provided respectively; by comparing the SEM images, it can be seen that after the treatment of the present invention, the bonding wires exhibit a more fine and uniform grain distribution, the grains are significantly refined, and the dislocation density is increased.

[0085] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. 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 deviate from the essence of the corresponding technical solutions within 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 improving the performance of a bonding wire, characterized in that: The steps include: (1) annealing and carburizing the bond wires after casting and drawing at the same time; (2) subjecting the bonding wire treated in step (1) to a cyclic cryogenic treatment; (3) The bonding wire treated in step (2) is sequentially washed with a chemical detergent and hot water, and dried to obtain a bonding wire with improved performance.

2. The method for improving the performance of a bonding wire according to claim 1, wherein: Step (1) is performed in a salt bath or sand bath environment; Preferably, the medium of the salt bath includes at least one of sodium chloride, potassium chloride, barium chloride, calcium chloride, sodium nitrate, potassium nitrate, sodium nitrite or potassium nitrite; Preferably, the medium of the sand bath includes at least one of quartz sand, yellow sand, fine sea sand or desert sand.

3. The method for improving the performance of a bonding wire according to claim 1, wherein: The annealing temperature is 400°C to 500°C; The annealing treatment time is 1 hour to 3 hours, and the annealing chamber length is 3 meters to 5 meters; or, the wire speed of the annealing is 0.5 meters per second to 1 meter per second.

4. The method for improving the performance of a bonding wire according to claim 2, wherein: The carburizing treatment includes: adding carbon raw materials into a solid phase medium of a salt bath or a sand bath, wherein the carbon raw materials include carbides and carbonates; Preferably, the carbide includes at least one of silicon carbide, boron carbide, sodium carbide, calcium carbide, titanium carbide or zirconium carbide, and the carbonate includes at least one of sodium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, copper carbonate, zinc carbonate, iron carbonate, sodium bicarbonate or potassium bicarbonate.

5. The method for improving the performance of a bonding wire according to claim 4, wherein: The mass ratio of the carbide to the carbonate is 85-95:5-15; Preferably, the mass ratio of the solid phase medium to the carbon raw material is 80-85:15-20.

6. The method for improving the performance of a bonding wire according to claim 1, wherein: The lower limit of the cycle temperature of the cyclic cryogenic treatment is -160°C to -140°C, and the upper limit of the cycle temperature is 15°C to 30°C; Preferably, the number of cycles of the cyclic cryogenic treatment is 3 to 5 times.

7. The method for improving the performance of a bonding wire according to claim 1, wherein: The chemical detergent comprises at least one of a borax solution, a fluoroborate solution or an acid solution; Preferably, the solute of the chemical wash comprises at least one of borax, sodium tetraborate decahydrate, fluoroboric acid, potassium fluoroborate, sodium fluoroborate, copper fluoroborate, dilute sulfuric acid, dilute nitric acid or citric acid; Preferably, the concentration of the chemical detergent is 2.5 wt.% to 10 wt.%.

8. The method for improving the performance of a bonding wire according to claim 1, wherein: The temperature of the hot water is 70°C to 90°C.

9. The method for improving the performance of a bonding wire according to claim 1, wherein: The drying temperature is 150° C. to 200° C., and the drying time is 0.3 h to 2 h.

10. Use of the bonding wire performance improvement method according to any one of claims 1 to 9 in bonding wires.

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