Lead-free alloy solder, preparation method thereof and display screen

Abstract

The invention discloses a lead-free alloy solder, a preparation method thereof and a display screen, and relates to the technical field of display. The lead-free alloy solder applied to the display screen comprises main fusion alloy and mutual fusion alloy, the melting point of the main fusion alloy ranges from 138 DEG C to 200 DEG C, the melting point of the mutual fusion alloy ranges from 210 DEG C to 280 DEG C, the main fusion alloy at least comprises tin and bismuth, and the mutual fusion alloy at least comprises tin, silver and / or tin and copper; the lead-free alloy solder can be used for welding light-emitting diodes in a display screen at the welding temperature larger than or equal to 200 DEG C and smaller than 210 DEG C. According to the lead-free alloy welding flux, the brittleness of welding spots can be greatly reduced, it is guaranteed that the welding spots have high welding strength and good impact reliability, the welding reliability of the lead-free alloy welding flux is guaranteed, and the performance of the lead-free alloy welding flux is good.

Description

Technical Field

[0001] This application belongs to the field of display technology, and particularly relates to a lead-free alloy solder, a preparation method thereof, and a display screen. Background Art

[0002] With the lead-free development of the electronics industry, the element lead (Pb) has been gradually phased out. In order to make the solder for attaching LED (light emitting diode) lamps in an LED display screen a lead-free solder, currently, high-temperature solder has been used to weld LED lamp beads onto a printed circuit board (PCB). However, the welding temperature of high-temperature solder is generally above 240°C. The excessively high temperature may cause problems such as easy yellowing and discoloration of LED lamp beads, deformation of the PCB, an increased risk of failure of the internal circuit of the PCB, and high power consumption.

[0003] Therefore, low-temperature solder has emerged as the times require. Currently, the welding temperature of commonly used low-temperature solder can be lower than that of high-temperature solder. However, low-temperature solder may cause a sharp increase in the brittleness of the solder joints, and the solder joints are prone to falling off and failing during service, thereby causing damage to the LED display screen. Summary of the Invention

[0004] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art, and provide a lead-free alloy solder, a preparation method thereof, and a display screen, so as to solve some problems existing in currently commonly used high-temperature solder and low-temperature solder.

[0005] To achieve the above application purpose, in the first aspect of this application, a lead-free alloy solder applied to a display screen is provided. The lead-free alloy solder includes a main melting alloy and a mutual melting alloy. The melting point of the main melting alloy is 138°C to 200°C, and the melting point of the mutual melting alloy is 210°C to 280°C. The main melting alloy includes at least tin and bismuth, and the mutual melting alloy includes at least tin and silver and / or tin and copper;

[0006] The lead-free alloy solder is used to weld the light-emitting diodes in the display screen at a welding temperature greater than or equal to 200°C and less than 210°C.

[0007] In some embodiments, the main melting alloy further includes at least one of silver, copper, and nickel.

[0008] In some embodiments, the main melting alloy includes, by mass percentage:

[0009] Bismuth, 30wt% - 40wt%;

[0010] Silver, 0wt% - 2wt%;

[0011] Copper, 0wt% - 1wt%;

[0012] Nickel, 0 wt% to 0.1 wt%;

[0013] The balance is tin.

[0014] In some embodiments, when the main fusion alloy includes tin, bismuth, silver, copper, and nickel, the main fusion alloy includes, by mass percentage:

[0015] Bismuth, 30 wt% to 40 wt%;

[0016] Silver, 0.1 wt% to 2 wt%;

[0017] Copper, 0.1 wt% to 1 wt%;

[0018] Nickel, 0.01 wt% to 0.1 wt%;

[0019] The balance is tin.

[0020] In some embodiments, the inter-fusion alloy further includes at least one of antimony and nickel.

[0021] In some embodiments, the inter-fusion alloy includes, by mass percentage:

[0022] Silver, 0.01 wt% to 4 wt%;

[0023] Copper, 0.01 wt% to 3 wt%;

[0024] Antimony, 0 wt% to 3 wt%;

[0025] Nickel, 0 wt% to 0.1 wt%;

[0026] The balance is tin.

[0027] In some embodiments, the lead-free alloy solder further includes metal nanoparticles, and the metal nanoparticles are capable of forming intermetallic compounds with the main fusion alloy at the welding temperature.

[0028] In a second aspect of the present application, there is provided a display screen, including the above-mentioned lead-free alloy solder. The display screen includes a circuit board and a light-emitting diode. The light-emitting diode is disposed on one side of the circuit board, and the lead-free alloy solder is located between the light-emitting diode and the circuit board. The lead-free alloy solder is used to weld the light-emitting diode to the circuit board at the welding temperature.

[0029] In a second aspect of the present application, there is provided a method for preparing a lead-free alloy solder. The method for preparing the lead-free alloy solder includes the following steps:

[0030] The primary molten alloy and the inter-molten alloy are respectively formed; wherein, the melting point of the primary molten alloy is 138°C to 200°C, the melting point of the inter-molten alloy is 210°C to 280°C, the primary molten alloy at least includes tin and bismuth, and the inter-molten alloy at least includes tin and silver and / or tin and copper;

[0031] The primary molten alloy is respectively made into primary molten alloy powder, and the inter-molten alloy is made into inter-molten alloy powder;

[0032] The primary molten alloy powder and the inter-molten alloy powder are physically mixed to obtain the lead-free alloy solder; wherein, the lead-free alloy solder is applied to a display screen, and the lead-free alloy solder is used to solder the light-emitting diodes in the display screen at a soldering temperature greater than or equal to 200°C and less than 210°C.

[0033] In some embodiments, physically mixing the primary molten alloy powder and the inter-molten alloy powder to obtain the lead-free alloy solder includes:

[0034] After physically mixing the primary molten alloy powder and the inter-molten alloy powder, metal nanoparticles are added and physically mixed to obtain the lead-free alloy solder; wherein, the metal nanoparticles are used to form intermetallic compounds with the primary molten alloy at the soldering temperature.

[0035] Compared with the prior art, the present application has the following technical effects:

[0036] The lead-free alloy solder provided by the embodiments of the present application, its preparation method, and a display screen. The main melting alloy in the lead-free alloy solder can be welded at a relatively low phase transition temperature. At the same time, a mutually soluble alloy is physically mixed in the main melting alloy. In this way, at a relatively low welding temperature, the main melting alloy is in a molten state and can achieve matrix mutual solubility with the mutually soluble alloy, so that bismuth in the main melting alloy will not diffuse and coarsen excessively, and is evenly dispersed in the solder joints, thereby greatly reducing the brittleness of the solder joints. Moreover, if the main melting alloy and the mutually soluble alloy also contain Ni element, the Ni element can inhibit the segregation of the Bi-rich phase. At the same time, if the mutually soluble alloy also contains Sb element, the Sb element can also inhibit the segregation and coarsening of the Bi-rich phase, improve the welding strength of the material, and reduce brittleness at the same time. In addition, if the lead-free alloy solder contains nano-enhanced particles, the nano-enhanced particles can undergo a metallurgical reaction with the main melting alloy during the welding process to generate intermetallic compounds. The intermetallic compounds are extremely fine and evenly dispersed in the solder joints, forming particle reinforcement and dispersion strengthening, ensuring the solder joint strength while further reducing brittleness. This alloy system ensures that the solder joints have high welding strength and good impact reliability. Furthermore, when the lead-free alloy solder is applied to weld light-emitting diodes in a display screen, since the lead-free alloy solder is a low-temperature solder, it can greatly reduce or even avoid various risks brought by excessive heat input to the light-emitting diodes, improve the service reliability of the solder joints after welding, and greatly improve the performance of the display screen. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 It is a process flow chart of the preparation of a lead-free alloy solder provided by the embodiments of the present application;

[0039] Figure 2 It is a process flow chart of the preparation of another lead-free alloy solder provided by the embodiments of the present application;

[0040] Figure 3 It is a process flow chart of the preparation of a main melting alloy provided by the embodiments of the present application;

[0041] Figure 4 It is a process flow chart of the preparation of a mutually soluble alloy provided by the embodiments of the present application;

[0042] Figure 5 It is a schematic diagram of the shear thrust on the LED lamp beads in a display screen provided by the embodiments of the present application;

[0043] Figure 6 It is a schematic diagram of an LED lamp bead in a display screen being impacted by a pendulum provided by an embodiment of the present application. Specific Embodiments

[0044] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0045] In the present application, the term "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Among them, A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0046] In the present application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b or c", or "at least one (item) of a, b and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c or a - b - c, where a, b, c can be single or multiple respectively.

[0047] It should be understood that in various embodiments of the present application, the magnitude of the sequence numbers of each process does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0048] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0049] The weight of the relevant components mentioned in the specification of the embodiments of the present application not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass in the specification of the embodiments of the present application can be well-known mass units such as μg, mg, g, kg, etc.

[0050] The terms "first", "second", etc. are for descriptive purposes only, used to distinguish objects such as substances from each other, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features.

[0051] With the development of technology, electronic devices have been studied and applied more and more widely in people's lives. Due to factors such as environmental protection and safety, the lead-free (Pb) trend in the electronics industry has gradually become popular, which makes it necessary to use less, preferably no, Pb element in the electronics industry. However, in LED displays, in order to solder LED beads well onto the PCB, the traditionally used solder is Sn63Pb37. The melting point of Sn63Pb37 is about 183°C, and the soldering temperature is around 210°C. It is a solder with excellent performance in the electronics industry. Thus, by setting the Sn63Pb37 solder between the LED beads and the PCB and then soldering the LED beads and the PCB at a temperature of about 210°C, the soldered LED beads are not easily detached and fail. However, it can be clearly seen that Sn63Pb37 contains Pb and the Pb content is relatively high, which is contrary to the lead-free trend.

[0052] It should be noted that 63 in Sn63Pb37 represents that the mass percentage of Sn is 63wt%, and 37 represents that the mass percentage of Pb is 37wt%. Other alloys are similar hereinafter and will not be elaborated further.

[0053] In order to achieve lead-free, high-temperature solders have been developed currently, such as SnAg3.0Cu0.5, SnAg1.0Cu0.5, etc. The soldering temperature of high-temperature solders is generally above 240°C, and the soldering performance is good, which can ensure that the LED beads are not easily detached and fail from the PCB. However, the temperature used in the soldering process of high-temperature solders is too high, which will bring many problems with uncontrollable risks. For example, the LED beads are prone to yellowing and discoloration, the PCB itself is prone to deformation, the risk of internal circuit failure of the PCB increases, and the power consumption is large.

[0054] In order to achieve better effects, low-temperature solders have been developed currently, such as Sn42Bi58, etc. The soldering temperature of low-temperature solders can be used below 190°C, and many of the above problems caused by high temperature will not exist. However, since low-temperature solders usually contain a large amount of bismuth (Bi) element, the brittleness of the solder joints between LED lamp beads and PCBs increases sharply, making the LED lamp beads prone to falling off and failing during service. As is well known, there are two common application scenarios for LED displays, namely stage rental screens and advertising stadium screens. Since stage rental screens need to be disassembled and assembled frequently, it is inevitable to often touch the LED lamp beads. Advertising stadium screens will inevitably be hit by footballs and it is also inevitable to often touch the LED lamp beads. Then, if the LED lamp beads are brittle, it is easier to fall off and fail in these two scenarios, resulting in limited applications of stage rental screens and advertising stadium screens. Thus, it can be seen that the problem of easy embrittlement and lamp falling of the commonly used SnBi-based alloys in LED displays is a major pain point in the industry.

[0055] To solve the above problems, it can also be considered to add indium (In) element to the solder to improve the toughness of the solder joints while reducing the melting point. However, since In belongs to precious metals and the cost is high, it is difficult to carry out large-scale production and application in the civilian and consumer electronics industries.

[0056] Based on the above content, on the one hand, the embodiments of the present application provide a lead-free alloy solder applied to a display screen. The lead-free alloy solder may include a main melting alloy and an intermelting alloy. The melting point of the main melting alloy is 138°C to 200°C, and the melting point of the intermelting alloy is 210°C to 280°C. The main melting alloy at least includes tin (Sn) and bismuth (Bi), and the intermelting alloy at least includes tin (Sn) and silver (Ag) and / or tin (Sn) and copper (Cu); the lead-free alloy solder is used to be able to be used at a soldering temperature greater than or equal to 200°C and less than 210°C.

[0057] In practical applications, the display screen in the embodiments of the present application is an LED display screen.

[0058] In practical applications, the melting point of the main melting alloy is 138°C to 200°C, indicating that the main melting alloy is a low-melting-point alloy solder. Here, the melting point of the above main melting alloy is not specifically limited. Exemplarily, the melting point of the main melting alloy can be 138°C, 140°C, 160°C, 180°C, 190°C or 200°C, etc.

[0059] In practical applications, the melting point of the intermelting alloy is 210°C to 280°C, indicating that the intermelting alloy is a high-melting-point alloy solder. Here, the melting point of the above intermelting alloy is not specifically limited. Exemplarily, the melting point of the intermelting alloy can be 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C or 280°C, etc.

[0060] It should be understood that the above-mentioned main fusible alloy comprising at least tin (Sn) and bismuth (Bi) may mean that the main fusible alloy is an SnBi-based alloy. Specifically, the main fusible alloy may only include Sn and Bi; or, in addition to Sn and Bi, the main fusible alloy may also include other elements, such as at least one of silver (Ag), copper (Cu), nickel (Ni), etc. There is no specific limitation here and it shall be subject to actual applications.

[0061] It should be understood that the above-mentioned inter-fusible alloy comprising at least tin (Sn) and silver (Ag), and / or tin (Sn) and copper (Cu) may mean that the inter-fusible alloy may at least include tin (Sn), silver (Ag), and copper (Cu). Thus, the welding strength of the solder joint between the LED lamp bead and the PCB can be improved by adding Ag and Cu, and the wettability of the lead-free alloy solder can be enhanced. Moreover, the melting point of the inter-fusible alloy is between 210°C and 280°C, and it is not very brittle and has good toughness. Specifically, the inter-fusible alloy may only include Sn, Ag, and Cu; or, in addition to Sn, Ag, and Cu, the inter-fusible alloy may also include other elements, such as at least one of antimony (Sb) and nickel (Ni), etc. There is no specific limitation here and it shall be subject to actual applications.

[0062] It should be understood that the above-mentioned lead-free alloy solder can be used at a soldering temperature greater than or equal to 200°C and less than 210°C may mean that the lead-free alloy solder in the embodiments of the present application is a low-temperature solder. Specifically, the soldering temperature of the lead-free alloy solder in the embodiments of the present application may be 200°C, 201°C, 203°C, 205°C, 207°C, or 209°C, etc.

[0063] Thus, when a soldering temperature higher than the melting point of the main fusible alloy is adopted for the lead-free alloy solder in the embodiments of the present application, at this soldering temperature, the main fusible alloy is in a molten state. At this time, the inter-fusible alloy has not melted. Then, the molten main fusible alloy can coat the inter-fusible alloy, and a chemical metallurgical reaction will occur between the molten main fusible alloy and the inter-fusible alloy. For example, Sn and Ag, and / or Sn and Cu in the inter-fusible alloy will penetrate into the molten main fusible alloy, thereby generating a mixed alloy, but a part of the inter-fusible alloy body will still be retained to form the final lead-free alloy solder.

[0064] It should be understood that the above lead-free alloy solder can be used at a soldering temperature greater than or equal to 200°C and less than 210°C, which may mean that the lead-free alloy solder in the embodiments of the present application can be used to solder the LED lamp beads in the display screen at a soldering temperature greater than or equal to 200°C and less than 210°C. Specifically, the LED display screen includes LED lamp beads and a PCB. The LED lamp beads are arranged on one side surface of the PCB, and the lead-free alloy solder is located between the LED lamp beads and the PCB. The lead-free alloy solder can be used to solder the LED lamp beads to the PCB at a soldering temperature greater than or equal to 200°C and less than 210°C.

[0065] The embodiments of the present application provide a lead-free alloy solder. The main melting alloy in the lead-free alloy solder can be soldered at a lower phase change temperature. At the same time, a mutually soluble alloy is physically mixed in the main melting alloy. In this way, at a lower soldering temperature, the main melting alloy is in a molten state and can achieve matrix mutual solubility with the mutually soluble alloy, so that bismuth in the main melting alloy will not diffuse and coarsen excessively and is uniformly dispersed in the solder joint, thereby greatly reducing the brittleness of the solder joint.

[0066] When the lead-free alloy solder is applied to the soldering of LED lamp beads in an LED display screen, since the lead-free alloy solder is a low-temperature solder, it can greatly reduce or even avoid various risks brought by excessive heat input to the LED lamp beads, improve the service reliability of the solder joint after soldering, and greatly improve the performance of the LED display screen.

[0067] In some embodiments, the main melting alloy may further include at least one of silver (Ag), copper (Cu), nickel (Ni), etc.; the mutually soluble alloy may further include at least one of antimony (Sb), nickel (Ni), etc.

[0068] Exemplarily, the main melting alloy may be SnBi35Ag1Cu0.5Ni0.05, SnBi30Cu0.5Ni0.05, SnBi40Ag1Ni0.05, etc.

[0069] Exemplarily, the mutually soluble alloy may be SnAg1Cu0.5Sb0.5Ni0.05, etc.

[0070] An embodiment of the present application provides a lead-free alloy solder. The main melting alloy in the lead-free alloy solder can be welded at a relatively low phase transition temperature. At the same time, the inter-melting alloy in the lead-free alloy solder is in a molten state at the welding temperature. At this time, the main melting alloy can achieve matrix inter-melting with the inter-melting alloy during the welding process. At the same time, the addition of at least one of elements such as Ag, Cu, Ni, and Sb can prevent excessive diffusion of Bi in the main melting alloy, and can be evenly dispersed in the formed solder joints, thereby reducing the brittleness of the solder joints and improving the reliability of the solder joints. Moreover, if the main melting alloy and the inter-melting alloy contain Ni element, the Ni element can inhibit the segregation of the Bi-rich phase. And if the inter-melting alloy contains Sb element, the addition of the Sb element can also inhibit the segregation and coarsening of the Bi-rich phase, improve the welding strength of the lead-free alloy solder, and at the same time reduce the brittleness of the lead-free alloy solder, ensuring the welding reliability of the lead-free alloy solder.

[0071] In some embodiments, the main melting alloy may include, by mass percentage: bismuth (Bi), 30 wt% to 40 wt%; silver (Ag), 0 wt% to 2 wt%; copper (Cu), 0 wt% to 1 wt%; nickel (Ni), 0 wt% to 0.1 wt%; and the balance is tin (Sn).

[0072] Exemplarily, Bi may be 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt% or 40 wt% etc. by mass percentage.

[0073] Exemplarily, Ag may be 0 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt% or 2 wt% etc. by mass percentage.

[0074] Exemplarily, Cu may be 0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt% or 1 wt% etc. by mass percentage.

[0075] Exemplarily, Ni may be 0 wt%, 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt% or 0.1 wt% etc. by mass percentage.

[0076] An embodiment of the present application provides a lead-free alloy solder. The main melting alloy in the lead-free alloy solder is a low-melting-point alloy solder, and its solid-liquid phase temperature (i.e., melting point range) can be between 138 °C and 200 °C, which can ensure welding at a temperature below 210 °C.

[0077] In some embodiments, when the main molten alloy includes tin (Sn), bismuth (Bi), silver (Ag), copper (Cu), and nickel (Ni), the main molten alloy may be by mass percentage: bismuth (Bi), 30wt% to 40wt%; silver (Ag), 0.1wt% to 2wt%; copper (Cu), 0.1wt% to 1wt%; nickel (Ni), 0.01wt% to 0.1wt%; the balance being tin (Sn).

[0078] Exemplarily, Bi may be 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, or 40wt% etc. by mass percentage.

[0079] Exemplarily, Ag may be 0.1wt%, 0.2wt%, 0.5wt%, 1wt%, 1.5wt%, or 2wt% etc. by mass percentage.

[0080] Exemplarily, Cu may be 0.1wt%, 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, or 1wt% etc. by mass percentage.

[0081] Exemplarily, Ni may be 0.01wt%, 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, or 0.1wt% etc. by mass percentage.

[0082] The embodiments of the present application provide a lead-free alloy solder. The main molten alloy in the lead-free alloy solder is a low-melting-point alloy solder, and its solid-liquid phase temperature (i.e., melting point range) can be between 138°C and 200°C, which can ensure welding at temperatures below 210°C.

[0083] In some embodiments, the inter-melting alloy may include by mass percentage: silver (Ag), 0.01wt% to 4wt%; copper (Cu), 0.01wt% to 3wt%; antimony (Sb), 0wt% to 3wt%; nickel (Ni), 0wt% to 0.1wt%; the balance being tin (Sn).

[0084] Exemplarily, Ag may be 0.01wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, or 4wt% etc. by mass percentage.

[0085] Exemplarily, Cu may be 0.01wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or 3wt% etc. by mass percentage.

[0086] Exemplarily, Sb may be 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or 3wt% etc. by mass percentage.

[0087] Exemplarily, Ni may be 0 wt%, 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt%, or 0.1 wt% etc. by mass percentage.

[0088] The embodiments of the present application provide a lead-free alloy solder. The eutectic alloy in the lead-free alloy solder is a high-melting-point alloy solder, and its solid-liquid phase temperature (i.e., melting point range) can be between 210°C and 280°C. The eutectic alloy can better provide the overall welding reliability for the lead-free alloy solder.

[0089] In some embodiments, in the lead-free alloy solder, the composition of the main melting alloy may include only one, and the composition of the eutectic alloy may include at least one.

[0090] The embodiments of the present application provide a lead-free alloy solder, which can obtain a lead-free alloy solder that can greatly reduce the brittleness of solder joints, ensure that the solder joints have high welding strength and good impact reliability, and guarantee welding reliability through the cooperation of a main melting alloy and at least one eutectic alloy.

[0091] In some embodiments, the lead-free alloy solder of the embodiments of the present application may further include metal nanoparticles, and the metal nanoparticles are used to be able to form intermetallic compounds with the main melting alloy at the welding temperature.

[0092] Exemplarily, the particle size of the metal nanoparticles may be less than or equal to 100 nm. Specifically, the particle size of the metal nanoparticles may be 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, or 100 nm etc.

[0093] In applications, the above metal nanoparticles may include Ag nanoparticles, Cu nanoparticles, Ni nanoparticles, alloy-based nanoparticles (for example, AgCu alloy nanoparticles), etc. The melting points of these nanoparticles are higher and they will not directly melt at the welding temperature, but react with the main melting alloy to form intermetallic compounds.

[0094] Thus, when the welding temperature is higher than the melting point of the main melting alloy, the main melting alloy is in a molten state, while the eutectic alloy is not melted, and the metal nanoparticles only chemically react with the molten main melting alloy. Specifically, the metal nanoparticles only undergo a metal alloying reaction with Sn in the molten main melting alloy to form intermetallic compounds. At this time, in the lead-free alloy solder, there will be the main melting alloy structure that the main melting alloy and the eutectic alloy have not reacted completely, the structure after the main melting alloy and the eutectic alloy have reacted completely, the eutectic alloy structure that the main melting alloy and the eutectic alloy have not reacted completely, and the intermetallic compounds formed by the reaction of the metal nanoparticles and the main melting alloy.

[0095] An embodiment of the present application provides a lead-free alloy solder. During the soldering process, metal nanoparticles in the lead-free alloy solder undergo an alloying (metallurgical) reaction with the molten main alloy to form intermetallic compounds. These intermetallic compounds can be extremely fine and evenly dispersed in the solder joint, forming particle reinforcement and dispersion strengthening. While ensuring the strength of the solder joint, it can further reduce brittleness, that is, this alloy system ensures that the solder joint has high soldering strength and good impact reliability, effectively improving the soldering reliability of the lead-free alloy solder.

[0096] In a second aspect, an embodiment of the present application provides a display screen. The display screen may include the above-mentioned lead-free alloy solder. The display screen includes a circuit board and light-emitting diodes. The light-emitting diodes are arranged on one side of the circuit board, and the lead-free alloy solder is located between the light-emitting diodes and the circuit board. The lead-free alloy solder is used to solder the light-emitting diodes to the circuit board at the soldering temperature.

[0097] In practical applications, the above-mentioned circuit board may include any one of a PCB, an FPC (flexible printed circuit), etc.

[0098] An embodiment of the present application provides a display screen. The light-emitting diodes in the display screen can be well soldered to the circuit board through the lead-free alloy solder, greatly reducing the risk of dropout failure of the light-emitting diodes, and the performance of the display screen is good.

[0099] In a third aspect, an embodiment of the present application provides a method for preparing a lead-free alloy solder.

[0100] Reference Figure 1 As shown, the method for preparing the lead-free alloy solder may include the following steps:

[0101] S1. Prepare the main alloy and the mutually soluble alloy respectively.

[0102] It should be noted that there is no specific limitation on the preparation sequence of the main alloy and the mutually soluble alloy. The main alloy can be prepared first and then the mutually soluble alloy; or, the mutually soluble alloy can be prepared first and then the main alloy; or, the main alloy and the mutually soluble alloy can be prepared simultaneously, and no specific limitation is made here.

[0103] There is no specific limitation on the method for preparing the main alloy and the mutually soluble alloy here. Exemplarily, the main alloy and the mutually soluble alloy can be prepared respectively by chemical metallurgical melting.

[0104] S2. Make the main alloy into main alloy powder and make the mutually soluble alloy into mutually soluble alloy powder respectively.

[0105] In practical applications, the main melting alloy can be made into main melting alloy powder and the mutual melting alloy can be made into mutual melting alloy powder respectively through an ultrasonic atomization process.

[0106] S3. Physically mix the main melting alloy powder and the mutual melting alloy powder to obtain a lead-free alloy solder.

[0107] In practical applications, the main melting alloy powder and the mutual melting alloy powder can be physically mixed evenly in a certain proportion to obtain a lead-free alloy solder.

[0108] Here, no specific limitation is made on the mixing ratio of the main melting alloy powder and the mutual melting alloy powder. Exemplarily, the mixing ratio of the main melting alloy powder and the mutual melting alloy powder can be 1-9:1. When the proportion of the main melting alloy is higher, a lower welding temperature can be used. Specifically, the mixing ratio of the main melting alloy powder and the mutual melting alloy powder can be 1:1, 3:1, 5:1, 8:1 or 9:1, etc.

[0109] The embodiment of the present application provides a preparation method of a lead-free alloy solder. The main melting alloy and the mutual melting alloy are respectively prepared through chemical metallurgy melting, and two or more main melting alloys and mutual melting alloys with different melting points are physically mixed to obtain a new solder. This solder can enable the main melting alloy to be welded at a lower phase change temperature, and mutually penetrate and melt with the mutual melting alloy during the welding melting process, so that Bi in the main melting alloy will not diffuse and coarsen excessively, and can be evenly dispersed in the solder joint. The performance of the lead-free alloy solder is good; in addition, this preparation method is simple and easy to implement, which is beneficial to industrial production and application.

[0110] In some embodiments, with reference to Figure 2 as shown, the above step S3. Physically mix the main melting alloy powder and the mutual melting alloy powder to obtain a lead-free alloy solder may include:

[0111] S31. After physically mixing the main melting alloy powder and the mutual melting alloy powder, add metal nanoparticles and physically mix them to obtain a lead-free alloy solder.

[0112] In practical applications, the main melting alloy powder and the mutual melting alloy powder can be physically mixed evenly in a certain proportion, and then a certain proportion of metal nanoparticles are added and physically mixed to obtain a lead-free alloy solder.

[0113] Here, no specific limitation is made on the mass fraction of the added metal nanoparticles. Exemplarily, the mass fraction of the added metal nanoparticles can be 0.1%-5%. Specifically, the mass fraction of the added metal nanoparticles can be 0.1%, 1%, 2%, 3%, 4% or 5%, etc.

[0114] It should be noted that the main melting alloy, inter-melting alloy, metal nanoparticles, etc. in the embodiments of the present application can refer to the above embodiments, which will not be elaborated here.

[0115] In addition, it should be noted that the difference between the soldering process of the lead-free alloy solder in the embodiments of the present application and the soldering process of traditional solders is that: in the embodiments of the present application, the time of maintaining the peak temperature (for example, 209 °C) during soldering should be greater than or equal to 120 s. Of course, the peak temperature can also be set to any value greater than or equal to 210 °C and less than 230 °C, that is, a wider process window can be achieved. When the soldering temperature is higher, the solder has more heat input, so that the reaction between the inter-melting alloy and the main melting alloy is more sufficient, and relatively higher soldering reliability can also be obtained.

[0116] The embodiments of the present application provide a preparation method of a lead-free alloy solder. The main melting alloy and the inter-melting alloy are respectively prepared by chemical metallurgical smelting, and two or more main melting alloys, inter-melting alloys and nano-enhanced particles with different melting points are physically mixed to obtain a new solder. This solder can be soldered under the condition of the lower phase change temperature of the main melting alloy, and mutually penetrate and melt with the inter-melting alloy during the soldering melting process. Moreover, the main melting alloy can also chemically react with the nano-enhanced particles to generate intermetallic compounds, so that Bi in the main melting alloy will not diffuse and coarsen excessively, and is uniformly dispersed in the solder joints, and the performance of the lead-free alloy solder is good; in addition, this preparation method is simple and easy to implement, which is beneficial to industrial production and application.

[0117] In some embodiments, referring to Figure 3 as shown, taking the main melting alloy as SnXBiYAgZCuANiB as an example, the smelting process of the main melting alloy includes the following steps:

[0118] S11. Put the Sn ingot into the smelting furnace and heat it up to 1100 °C. After the temperature is stable, add the Ag ingot, stir for a period of time, then take out and cast and cool to obtain the SnXAgZ intermediate alloy.

[0119] Among them, Z is 1 part to 10 parts by mass, and the balance is X.

[0120] S12. Put the Sn ingot into the smelting furnace and heat it up to 1200 °C. After the temperature is stable, add the Cu block, stir for a period of time, then take out and cast and cool to obtain the SnXCuA intermediate alloy.

[0121] Among them, A is 0.5 part to 5 parts by mass, and the balance is X.

[0122] S13. Put the Sn ingot into the smelting furnace and heat it up to 1560 °C. After the temperature is stable, add the Ni block, stir for a period of time, then take out and cast and cool to obtain the SnXNiB intermediate alloy.

[0123] Among them, B is 0.1 part to 1 part by mass, and the balance is X.

[0124] S14. Put the Sn ingot into a melting furnace and heat it up to 380 °C. After the temperature stabilizes, add the Bi ingot and stir for a period of time. Then heat it up to 450 °C. After the temperature stabilizes again, add the SnXAgZ master alloy and stir for a period of time. Then add the SnXNiB master alloy and stir for a period of time. Finally, add the SnXCuA master alloy and stir for a period of time, and then take it out for casting and cooling to obtain SnXBiYAgZCuANiB.

[0125] It should be noted that the order of the above steps S11, S12, and S13 is not specifically limited, and it shall be subject to the actual operation.

[0126] In addition, when any one of Z, A, and B is 0, for example, if Z = 0, then step S11 does not need to be carried out, and the same applies to others, which will not be elaborated here.

[0127] In some embodiments, referring to Figure 4 as shown, taking the mutual melting alloy SnCAgDCuESbFNiG as an example, the melting process of the mutual melting alloy includes the following steps:

[0128] S21. Put the Sn ingot into a melting furnace and heat it up to 1100 °C. After the temperature stabilizes, add the Ag ingot and stir for a period of time, and then take it out for casting and cooling to obtain the SnCAgD master alloy.

[0129] Among them, D is 1 part to 10 parts by mass, and the balance is C.

[0130] S22. Put the Sn ingot into a melting furnace and heat it up to 1200 °C. After the temperature stabilizes, add the Cu block and stir for a period of time, and then take it out for casting and cooling to obtain the SnCCuE master alloy.

[0131] Among them, E is 0.5 part to 5 parts by mass, and the balance is C.

[0132] S23. Put the Sn ingot into a melting furnace and heat it up to 1560 °C. After the temperature stabilizes, add the Ni block and stir for a period of time, and then take it out for casting and cooling to obtain the SnCNiG master alloy.

[0133] Among them, G is 0.1 part to 1 part by mass, and the balance is C.

[0134] S24. Place the Sn ingot into a melting furnace and heat it up to 800 °C. After the temperature stabilizes, add Sb blocks, stir for a period of time, then cool down to 450 °C. After the temperature stabilizes, add the SnCAgD master alloy, stir for a period of time, then add the SnCNiG master alloy, stir for a period of time, and finally add the SnCCuE master alloy. After stirring for a period of time, take it out for casting and cooling to obtain SnCAgDCuESbFNiG.

[0135] It should be noted that the order of the above steps S21, S22, and S23 is not specifically limited, and it shall be subject to the actual operation.

[0136] In addition, when any one of E, F, and G is 0, for example, if E = 0, then step S21 does not need to be carried out. The same applies to others and will not be elaborated here.

[0137] The following uses multiple specific examples to illustrate the preparation method and application of the lead-free alloy solder provided by the embodiments of the present application.

[0138] Example 1

[0139] 1. Preparation of the master alloy:

[0140] The master alloy is SnBi35Ag1Cu0.5Ni0.05, and the melting process of SnBi35Ag1Cu0.5Ni0.05 may include the following steps:

[0141] (1). Place 95 parts of Sn ingots into a melting furnace and heat it up to 1100 °C. After the temperature stabilizes, add 5 parts of Ag ingots, stir evenly for 20 min, then take it out for casting and cooling to obtain the Sn95Ag5 master alloy.

[0142] (2). Place 95 parts of Sn ingots into a melting furnace and heat it up to 1200 °C. After the temperature stabilizes, add 5 parts of Cu blocks, stir evenly for 20 min, then take it out for casting and cooling to obtain the Sn95Cu5 master alloy.

[0143] (3). Place 99.5 parts of Sn ingots into a melting furnace and heat it up to 1560 °C. After the temperature stabilizes, add 0.5 parts of Ni blocks, stir evenly for 20 min, then take it out for casting and cooling to obtain the Sn99.5Ni0.5 master alloy.

[0144] (4) Put 25 parts of Sn ingots into a melting furnace and heat it up to 380 °C. After the temperature is stable, add 35 parts of Bi ingots, stir evenly for 10 min, then heat it up to 450 °C. After the temperature is stable, add 20 parts of Sn95Ag5 master alloy, stir evenly for 10 min, then add 10 parts of Sn99.5Ni0.5 master alloy and stir evenly for 10 min. Finally, add 10 parts of Sn95Cu5 master alloy and stir evenly for 10 min, then take it out for casting and cooling to obtain SnBi35Ag1Cu0.5Ni0.05.

[0145] 2. Preparation of the inter-fused alloy:

[0146] The inter-fused alloy is SnAg1Cu0.5Sb0.5Ni0.05, and the melting process of SnAg1Cu0.5Sb0.5Ni0.05 may include the following steps:

[0147] (1) Put 95 parts of Sn ingots into a melting furnace and heat it up to 1100 °C. After the temperature is stable, add 5 parts of Ag ingots, stir evenly for 20 min, then take it out for casting and cooling to obtain Sn95Ag5 master alloy.

[0148] (2) Put 95 parts of Sn ingots into a melting furnace and heat it up to 1200 °C. After the temperature is stable, add 5 parts of Cu blocks, stir evenly for 20 min, then take it out for casting and cooling to obtain Sn95Cu5 master alloy.

[0149] (3) Put 99.5 parts of Sn ingots into a melting furnace and heat it up to 1560 °C. After the temperature is stable, add 0.5 parts of Ni blocks, stir evenly for 20 min, then take it out for casting and cooling to obtain Sn99.5Ni0.5 master alloy.

[0150] (4) Put 59.5 parts of Sn ingots into a melting furnace and heat it up to 800 °C. After the temperature is stable, add 0.5 parts of Sb blocks, stir evenly for 10 min, then cool it down to 450 °C. After the temperature is stable, add 20 parts of Sn95Ag5 master alloy, stir evenly for 10 min, then add 10 parts of Sn99.5Ni0.5 master alloy, stir evenly for 10 min, and finally add 10 parts of Sn95Cu5 master alloy, stir evenly for 10 min, then take it out for casting and cooling to obtain SnAg1Cu0.5Sb0.5Ni0.05.

[0151] 3. Preparation of the lead-free alloy solder:

[0152] (1) Make SnBi35Ag1Cu0.5Ni0.05 into

[0153] SnBi35Ag1Cu0.5Ni0.05 powder by ultrasonic atomization process.

[0154] (2) Make SnAg1Cu0.5Sb0.5Ni0.05 into

[0155] SnAg1Cu0.5Sb0.5Ni0.05 powder.

[0156] (3) Physically mix SnBi35Ag1Cu0.5Ni0.05 powder and SnAg1Cu0.5Sb0.5Ni0.05 powder evenly at a ratio of 1:1 to obtain a lead-free alloy solder.

[0157] Example 2

[0158] 1. Preparation of the main melting alloy:

[0159] The main melting alloy is SnBi30Cu0.5Ni0.05, and the melting process of SnBi30Cu0.5Ni0.05 may include the following steps:

[0160] (1) Put 95 parts of Sn ingots into a melting furnace and heat up to 1200 °C. After the temperature is stable, add 5 parts of Cu blocks, stir evenly for 20 min, then take out, cast and cool to obtain Sn95Cu5 master alloy.

[0161] (2) Put 99.5 parts of Sn ingots into a melting furnace and heat up to 1560 °C. After the temperature is stable, add 0.5 parts of Ni blocks, stir evenly for 20 min, then take out, cast and cool to obtain Sn99.5Ni0.5 master alloy.

[0162] (3) Put 50 parts of Sn ingots into a melting furnace and heat up to 380 °C. After the temperature is stable, add 30 parts of Bi ingots, stir evenly for 10 min, then heat up to 450 °C. After the temperature is stable, add 10 parts of Sn99.5Ni0.5 master alloy and stir evenly for 10 min. Finally, add 10 parts of Sn95Cu5 master alloy and stir evenly for 10 min, then take out, cast and cool to obtain SnBi30Cu0.5Ni0.05.

[0163] 2. Preparation of the interpenetrating alloy:

[0164] The interpenetrating alloy is SnAg1Cu0.5Sb0.5Ni0.05, and the melting process of SnAg1Cu0.5Sb0.5Ni0.05 may include the following steps:

[0165] (1) Put 95 parts of Sn ingots into a melting furnace and heat up to 1100 °C. After the temperature is stable, add 5 parts of Ag ingots, stir evenly for 20 min, then take out, cast and cool to obtain Sn95Ag5 master alloy.

[0166] (2). Put 95 parts of Sn ingots into a melting furnace and heat it up to 1200 °C. After the temperature stabilizes, add 5 parts of Cu blocks. After uniformly stirring for 20 min, take it out for casting and cooling to obtain Sn95Cu5 master alloy.

[0167] (3). Put 99.5 parts of Sn ingots into a melting furnace and heat it up to 1560 °C. After the temperature stabilizes, add 0.5 parts of Ni blocks. After uniformly stirring for 20 min, take it out for casting and cooling to obtain Sn99.5Ni0.5 master alloy.

[0168] (4). Put 59.5 parts of Sn ingots into a melting furnace and heat it up to 800 °C. After the temperature stabilizes, add 0.5 parts of Sb blocks and uniformly stir for 10 min. Then cool it down to 450 °C. After the temperature stabilizes, add 20 parts of Sn95Ag5 master alloy, uniformly stir for 10 min, then add 10 parts of Sn99.5Ni0.5 master alloy, uniformly stir for 10 min, and finally add 10 parts of Sn95Cu5 master alloy. After uniformly stirring for 10 min, take it out for casting and cooling to obtain SnAg1Cu0.5Sb0.5Ni0.05.

[0169] 3. Preparation of lead-free alloy solder:

[0170] (1). Make SnBi30Cu0.5Ni0.05 powder by ultrasonic atomization process for SnBi30Cu0.5Ni0.05.

[0171] (2). Make

[0172] SnAg1Cu0.5Sb0.5Ni0.05 powder by ultrasonic atomization process for SnAg1Cu0.5Sb0.5Ni0.05.

[0173] (3). After physically mixing SnBi30Cu0.5Ni0.05 powder and SnAg1Cu0.5Sb0.5Ni0.05 powder evenly at a ratio of 1:1, lead-free alloy solder is obtained.

[0174] Example 3

[0175] 1. Preparation of master alloy:

[0176] The master alloy is SnBi40Ag1Ni0.05. The melting process of SnBi40Ag1Ni0.05 may include the following steps:

[0177] (1). Put 95 parts of Sn ingots into a melting furnace and heat it up to 1100 °C. After the temperature stabilizes, add 5 parts of Ag ingots. After uniformly stirring for 20 min, take it out for casting and cooling to obtain Sn95Ag5 master alloy.

[0178] (2) Put 99.5 parts of Sn ingots into a melting furnace and heat it up to 1560 °C. After the temperature stabilizes, add 0.5 part of Ni blocks. After uniformly stirring for 20 min, take out and cast, and then cool to obtain the Sn99.5Ni0.5 master alloy.

[0179] (3) Put 30 parts of Sn ingots into a melting furnace and heat it up to 380 °C. After the temperature stabilizes, add 40 parts of Bi ingots and stir uniformly for 10 min. Then heat it up to 450 °C. After the temperature stabilizes, add 20 parts of Sn95Ag5 master alloy and stir uniformly for 10 min. Then add 10 parts of Sn99.5Ni0.5 master alloy and stir uniformly for 10 min to obtain SnBi40Ag1Ni0.05.

[0180] 2. Preparation of the inter-fused alloy:

[0181] The inter-fused alloy is SnAg1Cu0.5Sb0.5Ni0.05. The melting process of SnAg1Cu0.5Sb0.5Ni0.05 may include the following steps:

[0182] (1) Put 95 parts of Sn ingots into a melting furnace and heat it up to 1100 °C. After the temperature stabilizes, add 5 parts of Ag ingots. After uniformly stirring for 20 min, take out and cast, and then cool to obtain the Sn95Ag5 master alloy.

[0183] (2) Put 95 parts of Sn ingots into a melting furnace and heat it up to 1200 °C. After the temperature stabilizes, add 5 parts of Cu blocks. After uniformly stirring for 20 min, take out and cast, and then cool to obtain the Sn95Cu5 master alloy.

[0184] (3) Put 99.5 parts of Sn ingots into a melting furnace and heat it up to 1560 °C. After the temperature stabilizes, add 0.5 part of Ni blocks. After uniformly stirring for 20 min, take out and cast, and then cool to obtain the Sn99.5Ni0.5 master alloy.

[0185] (4) Put 59.5 parts of Sn ingots into a melting furnace and heat it up to 800 °C. After the temperature stabilizes, add 0.5 part of Sb blocks and stir uniformly for 10 min. Then cool it down to 450 °C. After the temperature stabilizes, add 20 parts of Sn95Ag5 master alloy and stir uniformly for 10 min. Then add 10 parts of Sn99.5Ni0.5 master alloy and stir uniformly for 10 min. Finally, add 10 parts of Sn95Cu5 master alloy and stir uniformly for 10 min. Then take out and cast, and then cool to obtain SnAg1Cu0.5Sb0.5Ni0.05.

[0186] 3. Preparation of the lead-free alloy solder:

[0187] (1). The SnBi40Ag1Ni0.05 is made into SnBi40Ag1Ni0.05 powder through an ultrasonic atomization process.

[0188] (2). The SnAg1Cu0.5Sb0.5Ni0.05 is made into

[0189] SnAg1Cu0.5Sb0.5Ni0.05 powder through an ultrasonic atomization process.

[0190] (3). After physically mixing the SnBi40Ag1Ni0.05 powder and the SnAg1Cu0.5Sb0.5Ni0.05 powder evenly at a ratio of 1:1, a lead-free alloy solder is obtained.

[0191] Example 4

[0192] The difference between Example 4 and Example 1 is only that: in step (3) of Example 1, after physically mixing the SnBi35Ag1Cu0.5Ni0.05 powder and the SnAg1Cu0.5Sb0.5Ni0.05 powder evenly at a ratio of 1:1 to obtain a lead-free alloy solder, it can be replaced with:

[0193] (31). After physically mixing the SnBi35Ag1Cu0.5Ni0.05 powder and the SnAg1Cu0.5Sb0.5Ni0.05 powder evenly at a ratio of 1:1, silver nanoparticles with a mass fraction of 1% and a particle size of 50 nm are added to obtain a lead-free alloy solder.

[0194] Comparative Example 1

[0195] Superalloy solder SnAg3.0Cu0.5.

[0196] Comparative Example 2

[0197] Low-temperature alloy solder Sn42Bi58.

[0198] Comparative Example 3

[0199] Low-temperature alloy solder SnBi35Ag1.

[0200] Next, the 4# powder solder paste of the lead-free alloy solder in Examples 1-4 of the present application, the 4# powder solder paste of the superalloy solder in Comparative Example 1, the 4# powder solder paste of the low-temperature alloy solder in Comparative Example 2, and the 4# powder solder paste of the low-temperature alloy solder in Comparative Example 3 are respectively applied to Figure 5 and Figure 6 in the display screen. Specifically, as Figure 5 and Figure 6As shown, the LED lamp beads 4 are arranged on one side surface of the PCB 1. Each LED lamp bead 4 has 4 pins 3, and 4# powder solder paste is provided between each pin 3 and the PCB 1. Among them, the 4# powder solder paste can be the lead-free alloy solder 4# powder solder paste of Embodiments 1-4 of the present application, the 4# powder solder paste of the high-temperature alloy solder of Comparative Example 1, the 4# powder solder paste of the low-temperature alloy solder of Comparative Example 2, and the 4# powder solder paste of the low-temperature alloy solder of Comparative Example 3.

[0201] It should be noted that Figure 5 and Figure 6 only show 2 pins 4 of each LED lamp bead 4. The other two pins of each LED lamp bead 4 are on the same horizontal line as these two pins 3 respectively, so they are blocked by these two pins 3 in the cross-sectional view and are not shown in Figure 5 and Figure 6 either.

[0202] In practical applications, the 4# powder solder paste of Embodiments 1-4 of the present application and Comparative Examples 1-3 is printed on one side surface of the PCB 1, and then the LED lamp beads 4 are placed on the side of the PCB 1 printed with the 4# powder solder paste, and welded and formed at a temperature greater than or equal to 200°C and less than 210°C to obtain the structures as shown in Figure 5 and Figure 6 .

[0203] Here, the specific type of the above-mentioned LED lamp beads 4 is not limited. Exemplarily, the LED lamp beads 4 can be 1515 LED lamp beads, etc.

[0204] It should be noted that the number of pins 3 of each LED lamp bead 4 is not limited to 4.

[0205] In addition, the solders of Embodiments 1-4 of the present application and Comparative Examples 1-3 are not limited to the 4# powder solder paste, and this is only for illustration here.

[0206] Please refer to Figure 5 again. Push each LED lamp bead 4 with a shear thrust F1 to obtain the average value of the lamp bead thrust, as shown in Table 1 below. It should be noted that the average value of the lamp bead thrust refers to the maximum force used to push off the LED lamp bead 4. The larger the average value of the lamp bead thrust, the better the welding stability of the LED lamp bead 4.

[0207] Please refer to Figure 6 again. Use a pendulum 5 to impact the welded LED lamp bead 4 to obtain the average value of the impact energy, as shown in Table 1 below. It should be noted that the average value of the impact energy represents the ability of the LED lamp bead 4 to absorb the impact force. The larger the average value of the impact energy, the greater the toughness and the smaller the brittleness of the solder joint between the pin 3 and the PCB 1, and the less likely the LED lamp bead 4 is to fall off and fail.

[0208] Table 1

[0209]

[0210]

[0211] As can be seen from Table 1, compared with Comparative Example 1, the average values of the lamp bead thrust and the impact energy in Examples 1-4 of the present application are not much different, indicating that the soldering strength of the lead-free alloy solder of the present application is comparable to that of the high-temperature solder in Comparative Example 1, and the brittleness problem is greatly reduced, and it can basically reach the level of the high-temperature solder.

[0212] Compared with Comparative Examples 2-3, the average values of the lamp bead thrust and the impact energy in Examples 1-4 of the present application are both larger, indicating that the performance of the lead-free alloy solder of the present application is superior to that of the traditional low-temperature solder.

[0213] Only the content related to the inventive points is introduced here, and the rest can be obtained by referring to the related technologies and will not be elaborated here.

[0214] The above embodiments only represent several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A lead-free alloy solder, characterized in that: Applied to display screens, the lead-free alloy solder comprises a main melting alloy and an inter-melting alloy, the melting point of the main melting alloy is 138° C. to 200° C., the melting point of the inter-melting alloy is 210° C. to 280° C., the main melting alloy comprises at least tin and bismuth, and the inter-melting alloy comprises at least tin and silver and / or tin and copper; The lead-free alloy solder is used for soldering the light-emitting diodes in the display screen at a soldering temperature greater than or equal to 200° C. and less than 210° C.

2. The lead-free alloy solder according to claim 1, characterized in that: The main melt alloy further includes at least one of silver, copper and nickel.

3. The lead-free alloy solder according to claim 2, characterized in that: The main melting alloy comprises, by mass percentage: Bismuth, 30 wt% to 40 wt%; Silver, 0wt% to 2wt%; Copper, 0wt% to 1wt%; Nickel, 0 wt% to 0.1 wt%; The balance is tin.

4. The lead-free alloy solder according to claim 3, characterized in that: In the case where the main melting alloy includes tin, bismuth, silver, copper and nickel, the main melting alloy includes, by mass percentage: Bismuth, 30 wt% to 40 wt%; Silver, 0.1wt% to 2wt%; Copper, 0.1wt% to 1wt%; Nickel, 0.01wt% to 0.1wt%; The balance is tin.

5. The lead-free alloy solder according to claim 1, characterized in that: The intermetallic alloy further includes at least one of antimony and nickel.

6. The lead-free alloy solder according to claim 5, characterized in that: The intermelting alloy comprises, by mass percentage: Silver, 0.01wt% to 4wt%; Copper, 0.01wt% to 3wt%; Antimony, 0wt% to 3wt%; Nickel, 0 wt% to 0.1 wt%; The balance is tin.

7. The lead-free alloy solder according to any one of claims 1 to 6, characterized in that: The lead-free alloy solder further includes metal nanoparticles, and the metal nanoparticles are configured to generate intermetallic compounds with the main melting alloy at the soldering temperature.

8. A display screen, characterized in that: The method comprises the lead-free alloy solder as claimed in any one of claims 1 to 7, wherein the display screen comprises a circuit board and a light-emitting diode, wherein the light-emitting diode is arranged on one side of the circuit board, and the lead-free alloy solder is located between the light-emitting diode and the circuit board, and the lead-free alloy solder is used to solder the light-emitting diode to the circuit board at the soldering temperature.

9. A method for preparing a lead-free alloy solder, characterized in that: The steps include: Forming a main melting alloy and an inter-melting alloy respectively; wherein the melting point of the main melting alloy is 138°C to 200°C, the melting point of the inter-melting alloy is 210°C to 280°C, the main melting alloy comprises at least tin and bismuth, and the inter-melting alloy comprises at least tin and silver and / or tin and copper; The main melting alloy is made into main melting alloy powder, and the mutual melting alloy is made into mutual melting alloy powder; The main melting alloy powder and the mutual melting alloy powder are physically mixed to obtain the lead-free alloy solder; wherein the lead-free alloy solder is applied to a display screen, and the lead-free alloy solder is used to solder the light-emitting diodes in the display screen at a soldering temperature greater than or equal to 200°C and less than 210°C.

10. The method for preparing lead-free alloy solder according to claim 9, characterized in that: The physically mixing the main melting alloy powder and the mutual melting alloy powder to obtain the lead-free alloy solder comprises: The lead-free alloy solder is obtained by physically mixing the main melting alloy powder and the mutual melting alloy powder, and then adding metal nanoparticles and physically mixing them; wherein the metal nanoparticles are used to generate intermetallic compounds with the main melting alloy at the soldering temperature.

Images