Precision preform soldering and method of making

Abstract

The application provides a precision preformed soldering piece and a preparation method thereof. By arranging a graphene layer between the preformed soldering piece and a flux layer, the welding quality and efficiency can be improved, the energy consumption and environmental pollution in the welding process can be reduced, the welding strength and corrosion resistance can be improved, the oxidation and thermal stress in the welding process can be reduced, the cavity rate can be reduced, the precision can be improved, fullerene is added in the alloy raw material, the fullerene has high chemical stability and strong mechanical properties, can form strong bonding with rare earth metals, has high heat conduction performance, can effectively dissipate heat, avoids overheating of the welding part to cause failure, significantly reduces the cavity rate, improves the precision of the welding, reduces the welding temperature required by the preformed soldering piece, and has excellent oxidation resistance, which can effectively prevent the oxidation of the metal surface.

Description

Technical Field

[0001] This invention relates to the field of preformed solder sheet technology, and in particular to precision preformed solder sheets and their preparation methods. Background Technology

[0002] In the field of electronic packaging, as the integration of components continues to increase, the density between components is getting higher and higher, and the lead spacing is getting finer and finer (especially the soldering of network connectors in 5G communication, with its dense components and irregularly shaped solder joints, as well as the ultra-high transmission efficiency requirements), the use of traditional soldering methods will cause damage to heat-sensitive electronic components. Therefore, it is more inclined to choose pre-formed solder pads with higher precision during soldering.

[0003] Preformed solder pads, with their specific processed shapes, are a common type of solder. They offer precise welding positioning and accurate quantitative application, typically used in applications requiring high solder shape and quality. These pads are generally small (mm-level) and lightweight (mg-level), making them particularly effective for controlling solder dimensions, especially in specific through-hole soldering and module connections. Pre-calculated metal content ensures solder quality and consistency, achieving high-precision brazing through precise control of solder metal content in electronic packaging. However, these preformed solder pads still suffer from high void ratios that are difficult to eliminate and cannot achieve even higher precision soldering. Therefore, there is an urgent need for a high-precision preformed solder pad that can improve soldering precision, reduce void ratios, and provide stable and uniform solder to meet the current market's high-precision requirements for preformed solder pads. Summary of the Invention

[0004] In order to solve the technical problems of high void ratio, difficulty in eliminating voids, and inability to achieve higher precision welding in the prior art, this invention provides a high-precision preformed welding sheet that can improve welding precision, reduce void ratio, and has stable and highly uniform solder.

[0005] A second objective of this invention is to provide a method for preparing precision preformed solder sheets.

[0006] To achieve the first objective mentioned above, the technical solution adopted by the present invention is as follows:

[0007] A precision preformed solder sheet includes a preformed solder sheet and a modified graphene layer and a flux layer sequentially coated on the preformed solder sheet;

[0008] The alloy raw material of the preformed solder sheet, by weight percentage, consists of the following components: 90.5-95.2% tin, 1.0-2.8% silver, 0.1-1.2% copper, 0.1-0.2% cerium, 0.5-1.4% yttrium, 0.2-0.7% gallium, 0.5-1.0% antimony, and 2.3-3.0% fullerene;

[0009] The flux layer comprises 75-80 wt% rosin, 10-15 wt% activator, 2-3 wt% surfactant, 4-6 wt% thixotropic agent, and 3-6 wt% antioxidant. By setting a graphene layer between the preformed solder sheet and the flux layer, the welding quality and efficiency can be improved, while reducing energy consumption and environmental pollution during the welding process. It can also improve the strength and corrosion resistance of the weld, reduce oxidation and thermal stress during the welding process, thereby reducing voids and improving precision. Furthermore, graphene can also enhance… The high electrical and thermal conductivity of the weld results in better electrical and thermal conductivity of the welded material. By adding fullerene to the alloy raw material, the fullerene has extremely high chemical stability and strong mechanical properties. It can form a strong bond with rare earth metals and has high thermal conductivity, which can effectively dissipate heat and prevent overheating of the weld joint, thus avoiding failure. It can also significantly reduce the void ratio, improve the welding precision, reduce energy consumption, reduce the welding temperature required for preformed weld pieces, and has excellent anti-oxidation properties, which can effectively prevent oxidation of the metal surface.

[0010] Preferably, the method for preparing the modified graphene layer includes the following steps:

[0011] A mixed solution containing ammonium chloride and rare earth chloride is heated in a water bath at 40-50℃, graphene oxide is added, and the solution is ultrasonically treated at 200-325W for 30-90 minutes. After washing and vacuum drying, modified graphene oxide is obtained. The modified graphene oxide is ultrasonically dispersed in deionized water to prepare a graphene suspension. A cationic surfactant is added to the graphene suspension and stirred until homogeneous to obtain a modified graphene treatment solution. This modified graphene treatment solution is then coated onto a preformed solder sheet. By adding rare earth elements to modify the graphene, it achieves higher compatibility with the preformed solder sheet, better flexibility and elasticity, lower stress under drastic temperature changes, and improved flux performance in the preformed process. The wetting and spreading speed and uniformity of the solder pad surface, after curing, can form a flux coating with consistent thickness and uniform composition, which is beneficial to improve the heat uniformity of the flux coating, reduce flux residue, thereby reducing the void ratio and improving its uniform dispersion on the solder pad surface layer. More preferably, the cationic surfactant is any one of octylphenol polyoxyethylene ether and isooctylphenol polyoxyethylene ether, more preferably isooctylphenol polyoxyethylene ether, which can prevent the agglomeration effect of rare earth elements and solve the problem of insufficient uniform dispersion. It can also improve its heat dissipation performance, effectively reduce the surface tension of lead-free solder, obtain good welding effect, and improve the wetting ability of flux.

[0012] Preferably, the rare earth chloride is a mixture of cerium chloride, niobium chloride, and palladium chloride. By using these three elements, coordination bonds can be formed with the oxygen-containing functional groups of graphene oxide, reducing the interfacial energy and surface energy of graphene oxide. This functionalizes the graphene oxide, improving the heat uniformity of the flux coating, reducing flux residue, and thus lowering the void ratio.

[0013] Preferably, the ratio of ammonium chloride, cerium chloride, niobium chloride and palladium chloride is 2:2:3:1.

[0014] Preferably, the activator is any one of isopropylamine hydrobromide, triethanolamine hydrobromide, and monoisopropanolamine; more preferably, the activator is monoisopropanolamine.

[0015] Preferably, the thixotropic agent is a combination of hydroquinone, dodecyl stearic acid, and modified hydrogenated castor oil. More preferably, the thixotropic agent is a mixture of hydroquinone, dodecyl stearic acid, and modified hydrogenated castor oil in a mass ratio of 2:1:3. The hydroquinone, dodecyl stearic acid, and modified hydrogenated castor oil work together to prevent the solder sheet from collapsing, thus preventing phenomena such as tailing, adhesion, and collapse during brazing.

[0016] Preferably, the antioxidant is any one of ethoxyquinoline, 2-ethyl ether azole, and methylbenzotriazole; more preferably, the antioxidant is methylbenzotriazole.

[0017] Preferably, the surfactant is sodium dodecylbenzenesulfonate.

[0018] Preferably, the overall shape of the precision preformed welding sheet is square, round, arc-shaped, ring-shaped, frame-shaped, or strip-shaped.

[0019] To achieve the second objective mentioned above, the technical solution adopted by the present invention is as follows:

[0020] The method for preparing a precision preformed solder sheet as described in any of the preceding methods includes the following steps:

[0021] S1. Weigh the above alloy components according to the weight percentage, melt and mix them, cool to 800°C, then add fullerene, continue to heat to 1600°C, mix for 3-5 minutes, cool and then die-cast.

[0022] S2, Preparation of modified graphene oxide treatment solution;

[0023] S3. The modified graphene oxide treatment liquid obtained in step S2 is uniformly coated on the surface of the preformed welding sheet substrate and dried to obtain the pretreated preformed welding sheet.

[0024] S4. Spray flux evenly onto the surface of the pre-treated preformed solder sheet obtained in step S3, and dry it to obtain a precision preformed solder sheet. The solder sheet substrate is prepared by first melting the alloy and then adding fullerene. The operation method is simple. The prepared fullerene solder sheet has high connection strength and oxidation resistance, and can also significantly reduce the void rate of the solder joint, which can improve the service life and safety of the post-weld material.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. The precision preformed welding sheet provided in this application, by setting a graphene layer between the preformed welding sheet and the flux layer, can improve the quality and efficiency of welding, reduce energy consumption and environmental pollution during the welding process, improve the strength and corrosion resistance of the welding, and reduce oxidation and thermal stress during the welding process, thereby reducing the generation of voids and improving precision. In addition, graphene can also improve the electrical and thermal conductivity of the welding, so that the welded material has better electrical conductivity and thermal conductivity. By adding fullerene to the alloy raw material, fullerene has extremely high chemical stability and strong mechanical properties, can form strong bonds with rare earth metals, and also has high thermal conductivity, which can effectively dissipate heat, avoid overheating of the welding part and failure, significantly reduce voids, improve welding precision, reduce energy consumption, reduce the welding temperature required for the preformed welding sheet, and has excellent anti-oxidation properties, which can effectively prevent metal surface oxidation.

[0027] 2. The method for preparing precision preformed welding sheets provided in this application involves first melting an alloy, then adding fullerene to prepare a welding sheet substrate, and finally coating it with a modified graphene layer and a flux layer. The operation method is simple, and the prepared fullerene welding sheets have high connection strength and oxidation resistance. They can also significantly reduce the void rate of the weld joints, thereby improving the service life and safety of the post-weld materials. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0029] Figure 1 This is a cross-sectional structural diagram of the precision preformed welding sheet of this application. Detailed Implementation

[0030] The specific technical solution of the present invention will be described below with reference to specific embodiments 1-3:

[0031] A precision preformed solder sheet includes a preformed solder sheet 1, and a modified graphene layer 2 and a flux layer 3 sequentially coated on the preformed solder sheet 1;

[0032] The alloy raw material of the preformed solder sheet 1 is composed of the following components by weight percentage: 90.5-95.2% tin, 1.0-2.8% silver, 0.1-1.2% copper, 0.1-0.2% cerium, 0.5-1.4% yttrium, 0.2-0.7% gallium, 0.5-1.0% antimony, and 2.3-3.0% fullerene;

[0033] The flux layer 3 contains 75-80 wt% rosin, 10-15 wt% activator, 2-3 wt% surfactant, 4-6 wt% thixotropic agent and 3-6 wt% antioxidant.

[0034] (1) Preparation of modified graphene oxide

[0035] A mixed solution containing ammonium chloride, cerium chloride, niobium chloride, and palladium chloride in a volume ratio of 2:2:3:1 is heated in a water bath at 40-50°C. Graphene oxide is added, and the solution is ultrasonically treated for 60 minutes at a power of 200-325W. After washing and vacuum drying, modified graphene oxide is obtained. The modified graphene oxide is ultrasonically dispersed in deionized water to prepare a graphene suspension. Isooctylphenol polyoxyethylene ether is added to the graphene suspension and stirred evenly to obtain a modified graphene treatment solution. The modified graphene treatment solution is then coated onto a pre-formed solder sheet to obtain the final product.

[0036] (2) Preparation of flux

[0037] Add 75wt% rosin to a container and heat to 120-140℃. After dissolving, add 2wt% surfactant and stir until completely dissolved. Keep the temperature at 120-140℃ and add 5wt% thixotropic agent and stir until completely dissolved. Reduce the temperature to 60-80℃, add 3wt% antioxidant and 15wt% activator, and stir for 40-60 minutes to obtain liquid flux.

[0038] Example 1:

[0039] S1. Weigh the above alloy components according to the weight percentage, melt and mix them, cool to 800°C, then add fullerene, continue to heat to 1600°C, mix for 3 minutes, cool and then die-cast.

[0040] S2. The modified graphene oxide treatment liquid obtained in step (1) is uniformly coated on the surface of the preformed welding sheet substrate and dried to obtain the pre-treated preformed welding sheet.

[0041] S3. Spray the flux obtained in step (2) evenly onto the surface of the pre-formed solder sheet obtained in step S2, and dry it to obtain a precision pre-formed solder sheet.

[0042] Example 2:

[0043] S1. Weigh the above alloy components according to the weight percentage, melt and mix them, cool to 800°C, then add fullerene, continue to heat to 1600°C, mix for 4 minutes, cool and then die-cast.

[0044] S2. The modified graphene oxide treatment liquid obtained in step (1) is uniformly coated on the surface of the preformed welding sheet substrate and dried to obtain the pre-treated preformed welding sheet.

[0045] S3. Spray the flux obtained in step (2) evenly onto the surface of the pre-formed solder sheet obtained in step S2, and dry it to obtain a precision pre-formed solder sheet.

[0046] Example 3:

[0047] S1. Weigh the above alloy components according to the weight percentage, melt and mix them, cool to 800°C, then add fullerene, continue to heat to 1600°C, mix for 5 minutes, cool and then die-cast.

[0048] S2. The modified graphene oxide treatment liquid obtained in step (1) is uniformly coated on the surface of the preformed welding sheet substrate and dried to obtain the pre-treated preformed welding sheet.

[0049] S3. Spray the flux obtained in step (2) evenly onto the surface of the pre-formed solder sheet obtained in step S2, and dry it to obtain a precision pre-formed solder sheet.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that fullerene was not added to the alloy solder, but the rest of the preparation methods and steps are the same as in Example 1.

[0052] Comparative Example 2

[0053] S1. Weigh the above alloy components according to the weight percentage, melt and mix them, cool to 800°C, then add fullerene, continue to heat to 1600°C, mix for 5 minutes, cool and then die-cast.

[0054] S2. Spray the flux obtained in step (2) evenly onto the surface of the preformed solder sheet obtained in step S1, and dry it to obtain the preformed solder sheet.

[0055] Table 1: Component weight percentage of solder alloy powder in Examples 1-3 and Comparative Examples 1-2

[0056] Alloy composition Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 tin 90.5 92.3 95.2 93.5 90.5 silver 2.1 2.8 1 2.1 2.1 copper 1.2 0.5 0.1 1.2 1.2 cerium 0.1 0.2 0.1 0.1 0.1 yttrium 1.4 0.9 0.5 1.4 1.4 gallium 0.7 0.3 0.2 0.7 0.7 antimony 1 0.5 0.6 1 1 Fullerenes 3 2.5 2.3 - 3

[0057] The preformed solder pads obtained in Examples 1-3 and Comparative Examples 1-2 were used to reflow solder the chips, and the void ratio was tested using X-ray detection. The void ratio was calculated as (S1-S2) / S1, where S1 is the solderable area of ​​the chip and S2 is the actual solderable area of ​​the chip. The void ratio test results are shown in Table 2.

[0058] Table 2: Void ratio test results of Examples 1-3 and Comparative Examples 1-2

[0059] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Cavitation rate (%) 0.33 0.36 0.32 1.92 1.00

[0060] As shown in Table 2, Comparative Example 1, lacking fullerene, resulted in a significant increase in void ratio. Similarly, Comparative Example 2, where the solder sheet layer was not coated with a modified graphene layer, also exhibited an increased void ratio. Therefore, the precision preformed solder sheet provided in this application, by incorporating a graphene layer between the preformed solder sheet and the flux layer, can improve welding quality and efficiency, reduce energy consumption and environmental pollution during the welding process, enhance welding strength and corrosion resistance, and decrease oxidation and thermal stress during welding, thereby reducing void ratio and improving precision. Furthermore, graphene can improve the electrical and thermal conductivity of the solder, resulting in better electrical and thermal conductivity of the welded material. By adding fullerene to the alloy raw materials, the fullerene... Fullerenes possess extremely high chemical stability and strong mechanical properties. They can form strong bonds with rare earth metals and also have high thermal conductivity, effectively dissipating heat and preventing overheating at the weld joint, thus reducing the void ratio and improving welding precision. Furthermore, they reduce energy consumption and the welding temperature required for preformed weld sheets. They also exhibit excellent oxidation resistance, effectively preventing metal surface oxidation. The preparation method involves first melting an alloy, then adding fullerenes to prepare the weld sheet substrate, followed by coating with a modified graphene layer and a flux layer. The operation is simple, and the prepared fullerene weld sheets have high bonding strength and oxidation resistance, significantly reducing the void ratio at the weld joint and improving the service life and safety of the post-weld materials.

[0061] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A precision preformed welding sheet, characterized in that: It includes a preformed solder sheet (1), and a modified graphene layer (2) and a flux layer (3) sequentially wrapped around the preformed solder sheet (1). The alloy raw material of the preformed solder sheet (1) is composed of the following components by weight percentage: 90.5-95.2% tin, 1.0-2.8% silver, 0.1-1.2% copper, 0.1-0.2% cerium, 0.5-1.4% yttrium, 0.2-0.7% gallium, 0.5-1.0% antimony and 2.3-3.0% fullerene; The flux layer (3) is composed of the following components by weight percentage: 75-80wt% rosin, 10-15wt% activator, 2-3wt% surfactant, 4-6wt% thixotropic agent and 3-6wt% antioxidant; The preparation method of the modified graphene layer (2) includes the following steps: A mixed solution containing ammonium chloride and rare earth chloride is heated in a water bath at 40-50℃, graphene oxide is added, and the solution is ultrasonicated at 200-325W for 30-90 minutes. After washing and vacuum drying, modified graphene oxide is obtained. The modified graphene oxide is ultrasonically dispersed in deionized water to prepare a graphene suspension. A cationic surfactant is added to the graphene suspension and stirred evenly to obtain a modified graphene treatment solution. The modified graphene treatment solution is coated onto a preformed solder sheet to obtain the final product. The rare earth chloride is a mixture of cerium chloride, niobium chloride and palladium chloride; The volume ratio of ammonium chloride, cerium chloride, niobium chloride, and palladium chloride is 2:2:3:

1.

2. The precision preformed welding sheet according to claim 1, characterized in that: The activator is any one of isopropylamine hydrobromide, triethanolamine hydrobromide, and monoisopropanolamine.

3. The precision preformed welding sheet according to claim 1, characterized in that: The thixotropic agent is a combination of hydroquinone, dodecyl stearic acid, and modified hydrogenated castor oil.

4. The precision preformed welding sheet according to claim 1, characterized in that: The antioxidant is any one of ethoxyquinoline, 2-ethyl ether azole, and methylbenzotriazole.

5. The precision preformed welding sheet according to claim 1, characterized in that: The surfactant is sodium dodecylbenzenesulfonate.

6. The precision preformed welding sheet according to claim 1, characterized in that: The overall shape of the precision preformed welding sheet is square, round, arc, ring, frame or strip.

7. The method for preparing a precision preformed solder sheet as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Weigh the above alloy components according to the weight percentage, melt and mix them, cool to 800°C, then add fullerene, continue to heat to 1600°C, mix for 3-5 minutes, cool and then die-cast. S2, Preparation of modified graphene oxide treatment solution; S3. The modified graphene oxide treatment liquid obtained in step S2 is uniformly coated on the surface of the preformed welding sheet substrate and dried to obtain the pretreated preformed welding sheet. S4. Spray flux evenly onto the surface of the pre-formed solder sheet obtained in step S3, and dry it to obtain a precision pre-formed solder sheet.

Images