A mixed tin paste applied to a photovoltaic junction box and a method of application thereof

Abstract

This application relates to the field of photovoltaic junction box soldering, specifically disclosing a mixed solder paste for photovoltaic junction boxes and its application method; a mixed solder paste for photovoltaic junction boxes includes mixed solder powder and flux, wherein the mixed solder powder includes Sn. 63 Pb 37 Tin powder and tin-bismuth alloy powder, wherein the tin-bismuth alloy is Sn 69.5 Bi 30 Cu 0.5 and Sn 64 Bi 35 One of Ag1, the Sn 63 Pb 37 The mass ratio of tin to bismuth alloy powder is (3-6):1; This application provides a mixed solder paste for photovoltaic junction boxes; the mixed solder paste, composed of two different powder types, can be heated at low temperature to form solder joints, which are stable, reliable, and not easily deformed, with moderate size, low residual pollution, and the solder pads can provide the flux required for secondary welding, and can be welded again under high temperature heating conditions.

Description

Technical Field

[0001] This application relates to the field of photovoltaic junction box soldering, and in particular to a mixed solder paste for use in photovoltaic junction boxes and its application method. Background Technology

[0002] With the rapid development of the photovoltaic industry in recent years, the demand for photovoltaic modules has also increased significantly. The main function of solar photovoltaic junction boxes is to connect and protect solar photovoltaic modules, connect the power generated by solar cells to external lines, and conduct the current generated by photovoltaic modules. Therefore, the strength of the photovoltaic junction box soldering is crucial to the stability of current transmission. It is estimated that the output value of solder paste used in each GW of photovoltaic junction boxes is about 1 million by 2023.

[0003] However, the current photovoltaic junction box manufacturing mainly involves first applying a small amount of solder paste or glue and then welding solder pads. The modules are then sent to the module factory for hot-press welding and reflow. The existing process involves applying solder paste, attaching solder pads, welding, and then welding the busbar at the module factory. This process is lengthy, slow, and inefficient. Summary of the Invention

[0004] To improve the existing photovoltaic junction box soldering process, this application provides a hybrid solder paste for photovoltaic junction boxes and its application method.

[0005] In a first aspect, this application provides a mixed solder paste for use in photovoltaic junction boxes, employing the following technical solution: a mixed solder paste for use in photovoltaic junction boxes, comprising mixed solder powder and flux, wherein the mixed solder powder comprises Sn 63 Pb 37 Tin powder and tin-bismuth alloy powder, wherein the tin-bismuth alloy is Sn 69.5 Bi 30 Cu 0.5 and Sn 64 Bi 35 One of Ag1, the Sn 63 Pb 37 The mass ratio of the tin-bismuth alloy powder to the bismuth alloy powder is (3-6):1.

[0006] By adopting the above technical solution, Sn 63 Pb 37 The melting point of the alloy powder is around 183℃, Sn 69.5 Bi 30 Cu 0.5 and Sn 64 Bi 35Ag1 has a melting point of 138-187℃. It is made by mixing two alloys with large differences in melting point to form a mixed solder paste. The amount of the low-temperature phase used is small. Low-temperature heating can promote the initial formation of the solder joint when the low-temperature phase melts first, which makes the solder joint hard and strong. The unmelted high-temperature phase is used to heat the solder pad to achieve secondary welding and strong welding with the solder strip.

[0007] By Sn 63 Pb 37 The melting point of the mixed tin powder formed by the powder and tin-bismuth alloy powder is around 175.5°C, which enables the mixed solder paste prepared in this application to form solder joints at a low temperature of 170-200°C. The solder joints are stable and reliable, not easily deformed, of moderate size, and have low residual contamination. At the same time, the residual solder sheets can provide the necessary flux for secondary soldering, and can be firmly soldered to the solder strip under high temperature heating conditions.

[0008] Adding bismuth powder to tin powder lowers the melting point of the mixed solder paste and improves its fluidity. Simultaneously, adding a small amount of Ag to the tin-bismuth alloy powder refines the grains, improves solder joint strength, and reduces the formation of black solder joints due to oxidation enrichment on the Bi surface.

[0009] Preferably, the mass ratio of the mixed tin powder to the flux is 100:(10-13).

[0010] Preferably, the tin powder in the mixed tin powder has a particle size of 25-53 μm.

[0011] Preferably, the flux comprises the following raw materials in parts by weight: 40-50 parts solvent, 30-40 parts rosin resin, 1-3 parts hydrogenated castor oil, 1-3 parts fumed silica, and 5-10 parts activator.

[0012] By employing the above technical solutions, rosin resin plays a binding and protective role during the soldering process, increasing the viscosity of the mixed solder paste, helping the solder to fix on the solder joint, and forming a protective film after soldering to prevent oxidation and corrosion of the solder joint, thus improving the reliability and stability of the solder joint. Hydrogenated castor oil reduces the surface tension of the solder, promotes the flow and wetting of the mixed solder paste on the solder joint, and improves soldering quality and efficiency. At the same time, hydrogenated castor oil also has certain antioxidant properties, helping to protect the solder joint from oxidation. Fumed silica can adjust the viscosity and thixotropy of the flux, preventing sedimentation and stratification of the flux during storage and use, ensuring the stability and printability of the flux.

[0013] Preferably, the solvent is at least one selected from polyethylene glycol, ethylene glycol, tetrahydrofurfuryl alcohol, hydrogenated rosin propylene ether, and diethyl adipate.

[0014] Preferably, the activator is at least one selected from methyl succinic acid, oxalic acid, salicylic acid, and succinic acid.

[0015] By employing the above technical solutions, methyl succinic acid, oxalic acid, salicylic acid, and succinic acid can remove oxides and contaminants from the surface of the solder joint, reduce the surface tension of the solder, and promote the wetting and bonding of the solder with the substrate. The activator can improve the reliability of the soldering and the strength of the solder joint, and reduce soldering defects.

[0016] Secondly, this application provides a method for applying mixed solder paste to photovoltaic junction boxes, employing the following technical solution:

[0017] A method for applying mixed solder paste to photovoltaic junction boxes includes the following specific steps: mixing mixed solder powder and flux evenly, vacuuming and shaping to form mixed solder paste, applying the mixed solder paste to a recessed substrate for printing, then soldering at 170-200℃ for 35-45s in an air atmosphere without pressure, and finally cooling to room temperature.

[0018] By adopting the above technical solution, the mixed solder paste can be pre-formed in an air atmosphere and pre-formed solder pads through low-temperature baking via printing. This saves on the solder pad surface mount process, resulting in appropriately sized solder joints, sufficient solder pad strength, strong adhesion to prevent detachment, low flux contamination, and residual solder pads providing flux for secondary soldering. Under high-temperature heating, it can be firmly soldered to the busbar. Using a recessed substrate reduces the amount of solder paste printed without decreasing the solder joint thickness, resulting in smaller solder joints and preventing solder pad overflow.

[0019] Preferably, rosin resin is heated and dissolved, then solvent, hydrogenated castor oil, fumed silica, and activator are added and mixed evenly to obtain flux; mixed tin powder and flux are mixed evenly, vacuumed and shaped to form mixed tin paste; the mixed tin paste is applied to a recessed substrate for printing, and then soldered at 170-200℃ for 35-45s in air atmosphere without pressure, and finally cooled to room temperature.

[0020] In summary, this application has the following beneficial effects:

[0021] 1. Because this application uses Sn 63 Pb 37 Sn 69.5 Bi 30 Cu 0.5 Sn 64 Bi 35 Ag1 and flux are mixed to form a mixed solder paste, which can be heated at low temperatures. This allows the low-temperature phase to melt first, resulting in a stable and reliable initial solder joint. At the same time, the unmelted high-temperature phase is used to heat the solder pads to achieve secondary soldering, ensuring a strong bond with the solder strip.

[0022] 2. In this application, pre-formed solder pads are formed by low-temperature baking through printing, which makes the solder pads have high strength and not easy to fall off. The residual solder pads can provide flux for secondary soldering. The printing of mixed solder paste changes the original process of applying solder paste / adhesive and then attaching solder pads, optimizes the process, saves time and increases efficiency. Detailed Implementation

[0023] The present application will be further described in detail below with reference to the embodiments.

[0024] All raw materials used in the examples are commercially available.

[0025] Example

[0026] Example 1

[0027] This embodiment provides a mixed solder paste for use in photovoltaic junction boxes, comprising mixed solder powder and flux, wherein the mass ratio of mixed solder powder to flux is 100:11.5, and the mixed solder powder includes Sn. 63 Pb 37 powder and Sn 69.5 Bi 30 Cu 0.5 Sn 63 Pb 37 powder and Sn 69.5 Bi 30 Cu 0.5 The mass ratio is 5:1, Sn 63 Pb 37 For Sn 63 Pb 37 -T3E type, Sn 69.5 Bi 30 Cu 0.5 For Sn 69.5 Bi 30 Cu 0.5 -T3 type, the average particle size of the mixed tin powder is 25-53μm, the flux contains the following raw materials in parts by weight: solvent 45kg, rosin resin 35kg, wherein the solvent is ethylene glycol, and the rosin resin CAS number is 85026-55-7.

[0028] The application method of mixed solder paste in photovoltaic junction boxes includes the following specific steps:

[0029] After heating and dissolving the rosin resin, mix it with the solvent, then mix it with the mixed tin powder, stir for 10 minutes, and vacuum for 30 minutes to obtain the shaped mixed tin paste. Wipe the copper components with a lint-free cloth, then apply the obtained mixed tin paste to a stencil with an opening of 8mm*4mm and a thickness of 1.10mm for printing. The stencil is recessed in the middle. Solder at 180℃ for 38 seconds in air atmosphere without applying pressure, and then cool to room temperature.

[0030] Example 2

[0031] The difference between Example 2 and Example 1 is that the Sn in the mixed tin powder raw material... 63 Pb 37 powder and Sn 69.5 Bi 30 Cu 0.5 The mass ratio is 3:1.

[0032] Example 3

[0033] The difference between Example 3 and Example 1 is that the Sn in the mixed tin powder raw material... 63 Pb 37 powder and Sn 69.5 Bi 30 Cu 0.5 The mass ratio is 6:1.

[0034] Example 4

[0035] The difference between Example 4 and Example 1 is that the tin-bismuth alloy powder in the mixed tin powder raw material is Sn. 64 Bi 35 Ag1. Where Sn 64 Bi 35 Ag1 is Sn 64 Bi 35 Ag1-T3 type.

[0036] Example 5

[0037] The difference between Example 5 and Example 1 is that the application method of the mixed solder paste includes the following specific steps:

[0038] After heating and dissolving the rosin resin, mix it with the solvent, then mix it with the mixed tin powder, stir for 10 minutes, and vacuum for 30 minutes to obtain the shaped mixed tin paste. Wipe the copper components with a lint-free cloth, then apply the obtained mixed tin paste to a stencil with an opening of 8mm*4mm and a thickness of 1.10mm for printing. The stencil is recessed in the middle. Solder at 170℃ for 38 seconds in air atmosphere without applying pressure, and then cool to room temperature.

[0039] Example 6

[0040] The difference between Example 6 and Example 1 is that the application method of the mixed solder paste includes the following specific steps:

[0041] After heating and dissolving the rosin resin, mix it with the solvent, then mix it with the mixed tin powder, stir for 10 minutes, and vacuum for 30 minutes to obtain the shaped mixed tin paste. Wipe the copper components with a lint-free cloth, then apply the obtained mixed tin paste to a stencil with an opening of 8mm*4mm and a thickness of 1.10mm for printing. The stencil is recessed in the middle. Solder at 200℃ for 38 seconds in air atmosphere without applying pressure, and then cool to room temperature.

[0042] Example 7

[0043] The difference between Example 7 and Example 1 is that the application method of the mixed solder paste includes the following specific steps:

[0044] After heating and dissolving the rosin resin, mix it with the solvent, then mix it with the mixed tin powder, stir for 10 minutes, and vacuum for 30 minutes to obtain the shaped mixed tin paste. Wipe the copper components with a lint-free cloth, then apply the obtained mixed tin paste to a stencil with an opening of 8mm*4mm and a thickness of 1.10mm for printing. The stencil is recessed in the middle. Solder at 100℃ for 23 seconds without applying pressure in an air atmosphere, then solder at 150℃ for 33 seconds and cool to room temperature.

[0045] Example 8

[0046] The difference between Example 8 and Example 1 is that the flux ingredients in the mixed solder paste include the following parts by weight: 45 kg solvent, 35 kg rosin resin, 2 kg hydrogenated castor oil, and 2 kg fumed silica. The hydrogenated castor oil is PEG40, and the fumed silica has an average particle size of 10-20 nm.

[0047] The application method of mixed solder paste includes the following specific steps:

[0048] Rosin resin is heated and dissolved, then mixed with solvent, rosin resin, hydrogenated castor oil, and fumed silica to form a flux paste. The flux paste is then mixed with mixed tin powder and stirred for 10 minutes, followed by vacuuming for 30 minutes to obtain a shaped mixed tin paste. After wiping the copper components with a lint-free cloth, the obtained mixed tin paste is applied to a stencil with an opening of 8mm*4mm and a thickness of 1.10mm for printing. The stencil is recessed in the middle. The stencil is soldered at 180℃ for 38 seconds in air without applying pressure, and then cooled to room temperature.

[0049] Example 9

[0050] The difference between Example 9 and Example 8 is that the flux raw materials in the mixed solder paste include the following parts by weight: 45 kg solvent, 35 kg rosin resin, 2 kg hydrogenated castor oil, 2 kg fumed silica, and 8 kg activator; wherein the activator is methyl succinic acid.

[0051] The application method of mixed solder paste includes the following specific steps:

[0052] After heating and dissolving rosin resin, mix it with solvent, rosin resin, hydrogenated castor oil, and fumed silica. Stir until homogeneous, then add an activator and continue stirring to form a flux. Mix the flux with mixed tin powder, stir for 10 minutes, and then vacuum for 30 minutes to obtain a shaped mixed tin paste. Wipe the copper components with a lint-free cloth, then apply the obtained mixed tin paste to a stencil with an opening of 8mm*4mm and a thickness of 1.10mm for printing. The center of the stencil is recessed. Solder at 180℃ for 38 seconds in air without applying pressure, and then cool to room temperature.

[0053] Example 10

[0054] The difference between Example 10 and Example 9 is that the amount of solvent used in the flux raw materials of the mixed solder paste is 40 kg, the amount of rosin resin is 40 kg, the amount of hydrogenated castor oil is 1 kg, the amount of fumed silica is 3 kg, and the amount of activator is 5 kg.

[0055] Example 11

[0056] The difference between Example 11 and Example 9 is that the amount of solvent used in the flux raw materials of the mixed solder paste is 50 kg, the amount of rosin resin is 30 kg, the amount of hydrogenated castor oil is 3 kg, the amount of fumed silica is 1 kg, and the amount of activator is 10 kg.

[0057] Comparative Example

[0058] Comparative Example 1

[0059] The difference between Comparative Example 1 and Example 1 is that the solder powder mixed in the mixed solder paste is Sn. 63 Pb 37 pink.

[0060] Comparative Example 2

[0061] The difference between Comparative Example 2 and Example 1 is that the solder powder mixed in the solder paste is Sn. 42 Bi 58 -T3 portions and Sn 63 Pb 37 -A mixture of T3E powders, Sn 42 Bi 58 -T3 portions and Sn 63 Pb37 The mass ratio of T3E powder is 2:5.

[0062] Performance testing

[0063] After soldering with the mixed solder paste provided in Examples 1-11 and Comparative Examples 1-2 of this application, the performance of the solder joints was tested, and the specific test results are shown in Table 1.

[0064] Detection methods

[0065] I. Appearance Inspection

[0066] Observe and record the height, size, and appearance of the solder joint after it has formed.

[0067] II. Wettability

[0068] The wetting properties of the mixed solder paste were tested in accordance with the standard ICPTM 650 2.4.45 "Solder Paste - Wetting Test".

[0069] Table 1: Performance Test Results Data Table

[0070]

[0071] The performance test results show that this application uses two alloys with significantly different melting points to make solder paste, which promotes hard, strong, and non-deformable solder joints. Secondary soldering is achieved using the unmelted high-temperature phase and remaining solder pads, resulting in a strong bond with the solder strip. The method of printing the mixed solder paste changes the original process of applying solder paste / adhesive and then attaching solder pads, optimizing the process, saving time, and increasing efficiency. Through the different processes of the mixed solder paste in Examples 5-7, the performance test results show that in low-temperature soldering at 170-200℃, the mixed solder paste prepared in this application, through low-temperature baking via printing, forms pre-shaped solder pads with good solder pad strength, strong adhesion, and is not easily detached, providing flux for secondary soldering. In Examples 8-11, the flux raw materials in the mixed solder paste are different, with the mixed solder paste prepared in Example 9 exhibiting superior overall performance.

[0072] A comparison of Comparative Examples 1-2 and Example 1 shows that Comparative Example 1 uses Sn 63 Pb 37 While solder powder, used as soldering powder, maintains the solder joint height within a reasonable range, the solder joints are relatively soft after low-temperature soldering, making them prone to deformation and chipping after impact. This application further demonstrates that using two different types of solder powder can maintain a hard, firm, stable, and reliable solder joint. The mixed solder powder in Comparative Example 2 is Sn. 42 Bi 58 -T3 portions and Sn 63 Pb 37Although the T3E powder mixture produced solder joints of moderate size and appropriate height, the coarse metallographic structure of (2)Bi made the alloy brittle, affecting the solder joint strength. Compared with Example 1, the solder joint strength of Comparative Example 2 was lower, and black solder joints also appeared in Comparative Example 2. Further explanation of the use of Sn 64 Bi 35 Ag1 powder, as a soldering powder, can refine grains, enhance solder joint strength, and reduce the formation of black solder joints.

[0073] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A hybrid solder paste applied to a photovoltaic junction box, characterized in that, Includes mixed tin powder and flux, wherein the mixed tin powder includes Sn 63 Pb 37 Tin powder and tin-bismuth alloy powder, wherein the tin-bismuth alloy is Sn 69.5 Bi 30 Cu 0.5 and Sn 64 Bi 35 One of Ag1, the Sn 63 Pb 37 The mass ratio of the flux to the tin-bismuth alloy powder is (3-6):1; the flux paste comprises the following raw materials in parts by weight: 40-50 parts solvent, 30-40 parts rosin resin, 1-3 parts hydrogenated castor oil, 1-3 parts fumed silica, and 5-10 parts activator; the activator is at least one of methyl succinic acid, oxalic acid, salicylic acid, and succinic acid.

2. The mixed solder paste for photovoltaic junction boxes according to claim 1, characterized in that, The mass ratio of the mixed tin powder to the flux is 100:(10-13).

3. The hybrid solder paste for photovoltaic junction boxes according to claim 1, wherein The tin powder in the mixed tin powder has a particle size of 25-53 μm.

4. The hybrid solder paste for photovoltaic junction boxes according to claim 1, wherein The solvent is at least one of polyethylene glycol, ethylene glycol, tetrahydrofurfuryl alcohol, hydrogenated rosin propylene ether, and diethyl adipate.

5. A method for applying mixed solder paste to a photovoltaic junction box as described in any one of claims 1-4, characterized in that, The specific steps include: mixing the mixed tin powder and flux evenly, vacuuming and shaping to form a mixed tin paste, applying the mixed tin paste to a recessed substrate for printing, then soldering at 170-200℃ for 35-45 seconds in an air atmosphere without applying pressure, and finally cooling to room temperature.

6. The method for applying mixed solder paste to photovoltaic junction boxes according to claim 5, characterized in that, The specific steps include: heating and dissolving rosin resin, then adding solvent, hydrogenated castor oil, fumed silica, and activator and mixing evenly to obtain flux; mixing mixed tin powder and flux evenly, vacuuming and shaping to form mixed solder paste; applying the mixed solder paste to a recessed substrate for printing, then soldering at 170-200℃ for 35-45 seconds in air without applying pressure, and finally cooling to room temperature.