A main grid silver paste for solving solder joint mesh printing and a preparation method thereof

Abstract

A busbar silver paste and preparation method for solving the problem of solder joint screen printing are disclosed. The silver paste comprises the following components by weight: a solid content of 80-90%, which is the sum of the mass fractions of silver powder and glass powder; silver powder accounting for 77-87% of the solid content, including spherical silver powder and auxiliary silver powder, with the spherical silver powder accounting for 58-87% of the silver powder content and the auxiliary silver powder accounting for 0-20% of the silver powder content; glass powder accounting for 3-5% of the solid content; an organic carrier content of 9-20%, which includes a resin and a solvent; and a dispersant content of 1-3%, which is one or more of deep-sea fish oil and modified fish oil. The preparation method comprises sequentially mixing, stirring and dispersing, three-roll grinding, and sieving the resulting silver paste. The present invention can improve the fluidity and plasticity of the busbar silver paste, solving the problems of screen printing and poor flatness of solder joints.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing a main grid silver paste that solves the problem of solder joint mesh printing. Background Art

[0002] Research shows that with the diversity of solder ribbons in solar cell modules, such as circular solder ribbons of different specifications, triangular solder ribbons, segmented solder ribbons, etc., high matching requirements are placed on the busbar silver paste. Among them, the main grid silver paste is prone to poor welding, and the mesh mark at the main grid welding point is one of the important reasons for poor welding.

[0003] Because the solid content of most busbar silver pastes is closer to that of fine grid front silver, most front silver manufacturers make minor adjustments to the silver powder and organic carrier to make their products suitable for busbar silver paste preparation. The resulting busbar silver pastes possess some of the properties of fine grid silver pastes. Currently, due to material selection issues, most busbar silver pastes exhibit nodularity on solder joints and poor flatness. Summary of the Invention

[0004] The first object of the present invention is to provide a main grid silver paste that solves the problem of mesh printing at solder joints, so as to improve the fluidity and plasticity of the main grid silver paste and solve the problems of mesh printing and poor flatness at solder joints.

[0005] A main grid silver paste for solving the problem of solder joint mesh printing is composed of the following components in parts by weight:

[0006] The solid content is 80-90%, which is the sum of the mass fractions of silver powder and glass powder;

[0007] The silver powder accounts for 77-87% of the solid content, and the silver powder includes spherical silver powder and auxiliary silver powder, the spherical silver powder accounts for 58-87% of the silver powder content, and the auxiliary silver powder accounts for 0-20% of the silver powder content;

[0008] The glass powder accounts for 3 to 5% of the solid content;

[0009] The organic carrier content is 9-20%, and the organic carrier includes resin and solvent;

[0010] The content of the dispersant is 1-3%, and the dispersant is one or more of deep-sea fish oil and modified fish oil.

[0011] Using this solution, when silver powder and glass powder are added to the organic carrier, the particle surface becomes wetted by the solvent. However, some particles fail to disperse due to electrostatic and van der Waals forces. Deep-sea fish oil and modified fish oil, acting as dispersants, then gradually adsorb onto the particle surface, forming a film that prevents the particles from reaggregating, thereby achieving the desired dispersion. Deep-sea fish oil is rich in unsaturated fatty acids, with the main active ingredients being eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are well-performing anionic surfactants, so using deep-sea fish oil as a flexible dispersant can ensure that the slurry has strong fluidity even at high temperatures.

[0012] Preferably, the secondary surface treatment of the silver powder is carried out by a dry method or a wet method; the particle size of the spherical silver powder is 0.5 to 2.0 μm, the specific gravity is 0.5 to 2.5 m2 / g, and the tap density is 3.5 to 5.5 g / ml;

[0013] The spherical silver powder is subjected to secondary surface treatment and has a coating agent on its surface, wherein the coating agent includes a lubricant and a release agent;

[0014] The coating agent accounts for 0.1 to 0.6% of the mass of the silver powder; the lubricant and release agent are one or more of erucamide, oleamide, and polysiloxane;

[0015] The secondary surface treatment of the spherical silver powder adopts a dry method or a wet method.

[0016] Using the above scheme, the surface treatment of silver powder is to apply the coating agent to the surface of the silver powder particles, the lubricant enhances the ductility of the silver powder, its resistance to mechanical stirring and shear force, and the release agent makes the silver powder less likely to be dissolved by the resin and forms a protective layer for the silver powder interface, making it easier to disperse.

[0017] Preferably, the glass powder has a softening point of 600-700°C, the glass powder is gallium-indium glass, the main components of the glass powder include gallium oxide and indium oxide, and other components include silicon oxide, aluminum oxide, copper oxide, manganese oxide, and boron oxide; the total mass of gallium oxide and indium oxide accounts for 60-80% of the total mass of the glass powder.

[0018] Using the above solution, gallium and indium are both rare metals, both are silvery white, have strong plasticity, good ductility, good corrosion resistance, can wet glass powder particles, improve brightness and whiteness; gallium indium glass powder has a high softening point, the viscosity can be quickly reduced after softening, and has good flow properties.

[0019] Preferably, the auxiliary silver powder is one or more of 0.2-1 μm ultrafine spherical powder and 1-3 μm flake powder.

[0020] Preferably, the weight ratio of the resin to the organic carrier is no more than 5%, and the resin is one or more of ethyl cellulose, acrylic resin, PVB, CAB, rosin resin, and phenolic resin.

[0021] Preferably, the solvent is one or more of butyl carbitol, butyl carbitol acetate, terpineol, 12-diol, and triethylene glycol butyl ether.

[0022] Preferably, the modified fish oil is oxidized fish oil, which is prepared by introducing oxygen combined with light or hydrogen peroxide combined with light to modify ordinary fish oil.

[0023] Using the above scheme, the main component of fish oil is unsaturated fatty acid glyceride. The oxygen content of ordinary fish oil increases after oxidation modification, which can better wet the surface of the particles, evenly disperse the particles, and prevent the sedimentation and agglomeration of the particles.

[0024] Preferably, the organic carrier is prepared by mixing, heating and stirring a resin and a solvent in sequence, with a stirring speed of 100-1000 r / min and a boiling temperature of 60-80°C.

[0025] Another object of the present invention is to provide a method for preparing the above-mentioned main grid silver paste for solving the problem of solder joint mesh printing, which comprises mixing 77-87% by weight of silver powder, 3-5% by weight of glass powder, 9-20% by weight of organic vehicle, and 1-3% by weight of dispersant in sequence, stirring and dispersing, three-roll grinding, and sieving to obtain the main grid silver paste for solving the problem of solder joint mesh printing.

[0026] Preferably, a stirrer is used for stirring and dispersing at a speed of 30 to 60 r / min and a stirring time of 60 to 120 min; a three-roll mill is used for grinding at a speed of 200 to 400 r / min; and a 300 to 500 mesh screen is used for filtering.

[0027] The beneficial effects of the present invention are:

[0028] First, the secondary surface treatment of silver powder is to apply the coating agent to the surface of silver powder particles. The lubricant enhances the ductility of silver powder, its resistance to mechanical stirring and shear force, and the release agent makes the silver powder less likely to be dissolved by the resin and forms a protective layer on the interface of the silver powder, making it easier to disperse.

[0029] Second, the rare metals gallium and indium are silvery white, have strong plasticity, good ductility, good corrosion resistance, can wet glass powder particles, and improve brightness and whiteness; gallium indium glass powder has a high softening point, and the viscosity can be rapidly reduced after softening, and it has good flow properties.

[0030] Third, the deep-sea fish oil in the dispersant is a flexible dispersant, which makes the slurry have strong fluidity even at high temperatures. The modified fish oil in the dispersant is made by oxidizing and modifying ordinary fish oil. The modified fish oil has an increased oxygen content, which can better wet the particle surface, evenly disperse the particles, and prevent particle sedimentation and aggregation.

[0031] The above-mentioned beneficial effects comprehensively improve the fluidity and plasticity of the main grid silver paste, and solve the problems of mesh printing and poor flatness of solder joints. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 Schematic diagram of a main grid with mesh segment printing in a comparative example of the present invention;

[0034] Figure 2 Schematic diagram of a main grid with no mesh nodes printed on solder joints according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] Example 1

[0036] A busbar silver paste for solving solder joint mesh printing, the formula of which is shown in Tables 1 to 4 below:

[0037] Table 1

[0038]

[0039]

[0040] Table 2

[0041]

[0042] The spherical silver powder is subjected to a secondary surface treatment by a dry method, and the lubricant and release agent of the coating agent are both oleic acid amide: the spherical silver powder and oleic acid amide are placed in a mixer for mixing, and the oleic acid amide accounts for 0.3% of the mass of the silver powder, so that the oleic acid amide is evenly dispersed and adsorbed on the surface of the spherical silver powder to form a coating layer.

[0043] Table 3

[0044] Gallium-Indium Glass Components Mass parts (%) Gallium oxide 40 Indium oxide 25 Silicon oxide 10 Copper oxide 15 Manganese oxide 10 Boron oxide 0 Alumina 0

[0045] Table 4

[0046] Organic carrier components Parts by weight (%) Specific parameters (weight parts) resin 4 Ethyl cellulose: 3%, phenolic resin: 1% solvent 96 Butyl Carbitol: 36%, Butyl Carbitol Acetate: 60%

[0047] The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 500 r / min and a boiling temperature of 60°C.

[0048] The above method for preparing the main grid silver paste to solve the problem of solder joint mesh printing has the following specific steps:

[0049] 1) preparing silver powder, glass powder, organic carrier and dispersant according to the above formula and mixing them in sequence;

[0050] 2) After mixing, use a stirrer to disperse the mixture. The stirring speed of the stirrer is set to 30 r / min and the stirring time is 120 min.

[0051] 3) After stirring and dispersing, three-roll milling was performed, and the grinding speed of the three-roll mill was set to 300 r / min;

[0052] 4) After grinding, sieve and filter using a 400-mesh sieve.

[0053] Please refer to Figure 2 , Table 13, Table 14, the main grid silver paste for solving the mesh printing of solder joints prepared according to the above formula and steps has no mesh printing and other performances are qualified.

[0054] Example 2

[0055] A busbar silver paste for solving solder joint mesh printing, the formula of which is shown in Tables 5 to 8 below:

[0056] Table 5

[0057]

[0058] The modified fish oil preparation method is as follows: ordinary fish oil and hydrogen peroxide are put into a beaker, the beaker is placed in a 55°C water bath, and light is irradiated at the same time, and the oxidized fish oil is obtained after the reaction for 30 minutes.

[0059] Table 6

[0060]

[0061] The spherical silver powder is subjected to a secondary surface treatment by a dry method, and the lubricant and release agent of the coating agent are both polysiloxane: the spherical silver powder and polysiloxane are placed in a mixer for mixing, and the polysiloxane accounts for 0.1% of the mass of the silver powder, so that the polysiloxane is evenly dispersed and adsorbed on the surface of the spherical silver powder to form a coating layer.

[0062] Table 7

[0063] Gallium-Indium Glass Components Mass parts (%) Gallium oxide 30 Indium oxide 30 Silicon oxide 8 Copper oxide 9 Manganese oxide 8 Boron oxide 8 Alumina 7

[0064] Table 8

[0065] Organic carrier components Parts by weight (%) Specific parameters (weight parts) resin 3 Acrylic resin: 2%, rosin resin: 1% solvent 97 Alcohol ester: 37%, terpineol: 60%

[0066] The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 100 r / min and a boiling temperature of 80°C.

[0067] The above method for preparing the main grid silver paste to solve the problem of solder joint mesh printing has the following specific steps:

[0068] 1) preparing silver powder, glass powder, organic carrier and dispersant according to the above formula and mixing them in sequence;

[0069] 2) After mixing, use a stirrer to disperse the mixture. The stirring speed of the stirrer is set to 60 r / min and the stirring time is 60 min.

[0070] 3) After stirring and dispersing, use a three-roll mill to perform three-roll grinding, and set the grinding speed of the three-roll mill to 400 r / min;

[0071] 4) After grinding, sieve and filter using a 500-mesh sieve.

[0072] Please refer to Figure 2 , Table 13, Table 14, the main grid silver paste for solving the mesh printing of solder joints prepared according to the above formula and steps has no mesh printing and other performances are qualified.

[0073] Example 3

[0074] A busbar silver paste for solving solder joint mesh printing, the formula of which is shown in Tables 9 to 12 below:

[0075] Table 9

[0076]

[0077]

[0078] The modified fish oil preparation method is as follows: ordinary fish oil is placed in a reaction container, oxygen is introduced into the reaction container for 5 minutes and light is irradiated at the same time, and oxidized fish oil is obtained after the reaction.

[0079] Table 10

[0080]

[0081] The spherical silver powder is subjected to a secondary surface treatment by a wet method, wherein the lubricant and release agent of the coating agent are both erucamide: erucamide is added to ethanol to prepare a coating agent solution, and then the spherical silver powder and the coating agent solution are placed in a mixer for mixing, wherein the erucamide accounts for 0.6% of the mass of the silver powder. After the erucamide is dissolved in ethanol, it is uniformly mixed with the spherical silver powder in a liquid state, and a coating layer is formed on the surface of the spherical silver powder.

[0082] Table 11

[0083] Gallium-Indium Glass Components Mass parts (%) Gallium oxide 55 Indium oxide 25 Silicon oxide 5 Copper oxide 4 Manganese oxide 3 Boron oxide 3 Alumina 5

[0084] Table 12

[0085]

[0086]

[0087] The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 550 r / min and a boiling temperature of 60°C.

[0088] The above method for preparing the main grid silver paste to solve the problem of solder joint mesh printing has the following specific steps:

[0089] 1) preparing silver powder, glass powder, organic carrier and dispersant according to the above formula and mixing them in sequence;

[0090] 2) After mixing, use a stirrer to disperse the mixture. The stirring speed of the stirrer is set to 50 r / min and the stirring time is 70 min.

[0091] 3) After stirring and dispersing, three-roll milling was performed, and the grinding speed of the three-roll mill was set to 300 r / min;

[0092] 4) After grinding, sieve and filter using a 300-mesh sieve.

[0093] Please refer to Figure 2 , Table 13, Table 14, the main grid silver paste for solving the mesh printing of solder joints prepared according to the above formula and steps has no mesh printing and other performances are qualified.

[0094] Please refer to Figure 1 and Figure 2 The busbar silver pastes of Examples 1-3 and the busbar silver paste of Comparative Example 1 on the market were used in solar cells, respectively. The conversion efficiency (EFF), open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), series resistance (Rs), parallel resistance (Rsh), welding tension, and screen printing of the manufactured cells were analyzed. The results are shown in Tables 13 and 14 below:

[0095] Table 13

[0096] serial number EFF (%) Voc(V) Isc(A) FF(%) Example 1 23.27 0.6854 11.629 80.11 Example 2 23.28 0.6852 11.622 80.16 Example 3 23.26 0.6851 11.624 80.09 Comparative Example 1 23.26 0.6852 11.622 80.08

[0097] Table 14

[0098] serial number Rs(Ω) Rsh(Ω) Welding tension (N) Net printing situation Example 1 0.0024 627 6.3 none Example 2 0.0024 562 6.6 none Example 3 0.0024 551 6.2 none Comparative Example 1 0.0024 582 4.7 have

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A busbar silver paste for solving solder joint mesh printing, characterized in that: It is composed of the following ingredients in parts by weight: The solid content is 80~90%, which is the sum of the mass fractions of silver powder and glass powder; The softening point of the glass powder is 600-700°C; The silver powder has a content of 77-87%, and the silver powder includes spherical silver powder and auxiliary silver powder, wherein the content of the spherical silver powder is 58-87% and the content of the auxiliary silver powder is 0-20%. The spherical silver powder is coated with a coating agent after secondary surface treatment, and the coating agent includes a lubricant and a release agent. The glass powder content is 3-5%; the glass powder is gallium-indium glass, the main components of the glass powder include gallium oxide and indium oxide, and other components include silicon oxide, aluminum oxide, copper oxide, manganese oxide, and boron oxide; the total mass of gallium oxide and indium oxide accounts for 60-80% of the total mass of the glass powder; The organic carrier content is 9-20%, and the organic carrier includes resin and solvent; The dispersant content is 1-3%, and the dispersant is one or more of deep-sea fish oil and modified fish oil.

2. The main grid silver paste for solving solder joint mesh printing according to claim 1 is characterized in that: The spherical silver powder has a particle size of 0.5-2.0 μm, a specific gravity of 0.5-2.5 m2 / g, and a tap density of 3.5-5.5 g / ml; The coating agent accounts for 0.1-0.6% of the mass of the silver powder; the lubricant and release agent are one or more of erucamide, oleamide, and polysiloxane; The secondary surface treatment of the spherical silver powder adopts a dry method or a wet method.

3. The main grid silver paste for solving solder joint mesh printing according to claim 1, characterized in that: The auxiliary silver powder is one or more of 0.2-1 μm ultrafine spherical powder and 1-3 μm flake powder.

4. The main grid silver paste for solving solder joint mesh printing according to claim 1, characterized in that: The weight of the resin in the organic carrier does not exceed 5%, and the resin is one or more of ethyl cellulose, acrylic resin, PVB, CAB, rosin resin, and phenolic resin.

5. The main grid silver paste for solving solder joint mesh printing according to claim 1, characterized in that: The solvent is one or more of butyl carbitol, butyl carbitol acetate, terpineol, alcohol ester dodecanol, and triethylene glycol butyl ether.

6. The main grid silver paste for solving solder joint mesh printing according to claim 1, characterized in that: Modified fish oil is oxidized fish oil, which is modified by introducing oxygen combined with light or hydrogen peroxide combined with light to complete the modification of ordinary fish oil.

7. The main grid silver paste for solving solder joint mesh printing according to claim 1, characterized in that: The organic carrier is prepared by mixing, heating and stirring the resin and the solvent in sequence, with a stirring speed of 100-1000 r / min and a boiling temperature of 60-80°C.

8. A method for preparing a main grid silver paste for solving the problem of solder joint mesh printing according to claim 1, characterized in that: 77-87% by weight of silver powder, 3-5% by weight of glass powder, 9-20% by weight of organic vehicle, and 1-3% by weight of dispersant are sequentially mixed, stirred and dispersed, three-roll milled, and sieved to obtain a main grid silver paste for solving the problem of solder joint mesh printing.

9. The method for preparing a main grid silver paste for solving the problem of solder joint mesh printing according to claim 8, characterized in that: A stirrer is used for stirring and dispersing at a speed of 30-60 r / min and a stirring time of 60-120 min; a three-roll grinder is used for three-roll grinding at a speed of 200-400 r / min; and a 300-500 mesh sieve is used for filtration.

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