TWI528385B - Silver conductive adhesive and method for manufacturing the same - Google Patents

Description

Silver conductive adhesive and manufacturing method thereof

The present invention relates to a conductive paste, and more particularly to a silver conductive paste and a method of manufacturing the same.

In the current manufacturing technology of solar cells, silver conductive paste is usually used as the back electrode. In recent years, as the price of silver has risen and the increase can be as high as 80%, in order to reduce the production cost of solar cells, there is an urgent need for a low solid content silver paste, that is, a low silver content silver paste.

Chinese Patent Publication No. 101814551 discloses a method for preparing a solar cell back silver paste. The back silver paste produced in this patent has a relatively high solids content ranging from 75 wt% to 85 wt%. When the back electrode of the solar cell is fabricated by using the back silver paste, the production cost of the solar cell is greatly increased.

In addition, U.S. Patent Publication No. 20100163101 discloses a technique for producing a conductive paste by using a nickel aluminum alloy powder, a nickel aluminum chrome alloy powder or a nickel chrome alloy powder in place of a part of the silver powder. In this patent, the proportion of silver powder is from 37.5 wt% to 75 wt%, and the proportion of nickel alloy powder is from 25 wt% to 62.5 wt%. However, in the technique of directly adding a metal powder such as a nickel aluminum alloy powder, a nickel aluminum chrome alloy powder or a nickel chrome alloy powder, these metal powders The surface is oxidized during the subsequent sintering process, resulting in insufficient tensile force between the formed back electrode and the ruthenium substrate and poor conductivity, which cannot meet the requirements of the back electrode of the solar cell.

Therefore, one aspect of the present invention provides a method for producing a silver conductive paste by adding a suitable non-precious metal powder such as copper powder, silver plated copper powder, silver plated aluminum powder, silver plated nickel powder or plating. Silver tin powder is used as a conductive functional material. Thereby, the ratio of the silver content can be lowered while taking into consideration the conductivity of the silver conductive paste. Therefore, not only the conductivity of the back electrode of the solar cell can be ensured, but the solar cell can have excellent light conversion efficiency, and the price of the silver conductive paste can be effectively reduced.

Another aspect of the present invention provides a method for manufacturing a silver conductive paste, which can be used to fabricate a back electrode of a solar cell to enhance the adhesion of the back electrode to the substrate, and can be improved. Solderability between the back electrode and the tinned copper strip. Therefore, the tensile value between the back electrode and the ruthenium substrate and the light conversion efficiency of the solar cell can be improved.

In accordance with the above object of the present invention, a method of producing a silver conductive paste is provided which comprises the following steps. Providing a plurality of conductive metal powders, wherein the conductive metal powder comprises a spherical silver powder, and a submicron copper powder, a submicron silver plated copper powder, a submicron silver plated aluminum powder, a submicron silver plated nickel powder and/or Or sub-micron silver plated tin powder. These conductive metal powders are mixed with a polymer type dispersant at a normal temperature to form a first mixture. Provide multiple glass powders. These glass frits are mixed with an ionic dispersant at normal temperature to form a second mixture. An organic carrier is provided. The first mixture The second mixture is uniformly blended into the organic vehicle to form a colloid. In this colloid, the total content of the first mixture and the second mixture is from 40% by weight to 55% by weight, the organic vehicle has a content of the remaining proportion, and the ratio of the conductive metal powder to the glass powder is from 13.0 to 16.0. The colloid is ground to form a silver conductive paste.

According to an embodiment of the present invention, the glass frit has a median diameter (D50) of from 0.4 μm to 1.0 μm.

According to another embodiment of the present invention, the conductive metal powder comprises a spherical silver powder, and a submicron copper powder or a submicron silver plating copper powder. Moreover, the first mixture comprises spherical silver powder in an amount of from 90% by weight to 98% by weight, submicron-sized copper powder or sub-micron-sized silver-plated copper powder in an amount of from 1% by weight to 9% by weight, and in an amount of from 0.2% by weight to 1.2% by weight % of polymeric dispersant. The colloid contains a glass frit having a content of 2% by weight to 5% by weight, and an ionic dispersing agent in an amount of 0.1% by weight to 0.8% by weight.

According to still another embodiment of the present invention, the conductive metal powder comprises a spherical silver powder, and a submicron silver-plated copper powder or a sub-micron silver-plated aluminum powder. Moreover, these conductive metal powders further comprise flake silver powder. Further, the first mixture comprises spherical silver powder in an amount of from 83% by weight to 96% by weight, and the content of the micron-sized silver-plated copper powder or the sub-micron-plated silver-plated aluminum powder in an amount of from 1% by weight to 10% by weight, in an amount of from 1% by weight to 6% by weight The flake silver powder and the polymer type dispersant in an amount of 0.2% by weight to 1.2% by weight. The colloid contains a glass frit having a content of 2% by weight to 5% by weight, and an ionic dispersing agent in an amount of 0.1% by weight to 0.8% by weight.

According to still another embodiment of the present invention, the conductive metal powder comprises a spherical silver powder and a submicron silver-plated aluminum powder. Moreover, these conductive metal powders further comprise high specific surface area flake silver powder and nano silver powder. In addition, the first mix The composition comprises spherical silver powder in an amount of 79% by weight to 94% by weight, submicron silver-plated aluminum powder in an amount of 2% by weight to 7% by weight, high specific surface area flake silver powder in an amount of 2% by weight to 7% by weight, and a content of 2wt % to 7 wt% of nano-sized silver powder, and a polymeric dispersant in an amount of 0.2 wt% to 1.2 wt%; and a colloid comprising glass frit having a content of 2 wt% to 5 wt%, and a content of 0.1 wt% to 0.8 wt% % ionic dispersant.

According to still another embodiment of the present invention, the glass frit has a softening point cooling temperature of from 300 ° C to 380 ° C.

According to still another embodiment of the present invention, the raw material of the organic carrier comprises 1 wt% to 5 wt% of polyvinyl butyral resin (PVB), 2 wt% to 16 wt% of ethyl cellulose (Etlyl Cellulose; EC), 2% to 10% by weight of rheological properties aid, 16% to 25% by weight of Butyl Carbitol (BC) or 16% to 25% by weight of diethylene glycol monobutyl ether acetate (Butyl Carbitol Acetate; BCA), and terpineol (Terpineol) in the remaining proportion.

According to still another embodiment of the present invention, the step of providing the organic vehicle comprises performing agitation and dissolution treatment of the raw material of the organic vehicle at a temperature of from 70 ° C to 90 ° C.

According to still another embodiment of the present invention, the step of grinding the colloid comprises dispersing the colloid to a fineness of less than 8 μm.

According to still another embodiment of the present invention, the step of grinding the colloid comprises adding a thickener or a diluent to adjust the viscosity of the colloid.

According to still another embodiment of the present invention, the step of grinding the colloid utilizes a three-roller.

According to the above object of the present invention, a silver conductive paste is proposed. The silver conductive paste comprises a first mixture, a second mixture, and an organic vehicle. The first mixture comprises a plurality of conductive metal powders and a polymeric dispersant. These conductive metal powders include globular silver powder, and submicron copper powder, submicron silver plated copper powder, submicron silver plated aluminum powder, submicron silver plated nickel powder and/or submicron silver plated tin powder. . The second mixture comprises a plurality of glass frits and an ionic dispersant. The first mixture and the second mixture described above are uniformly blended in an organic vehicle to form a colloid. Wherein, in the colloid, the total content of the first mixture and the second mixture is from 40% by weight to 55% by weight, and the organic vehicle has a content of the remaining ratio. Moreover, the ratio of these conductive metal powders to glass frit is from 13.0 to 16.0.

According to an embodiment of the present invention, the glass frit has a median diameter of from 0.4 μm to 1.0 μm.

According to another embodiment of the present invention, the conductive metal powder comprises a spherical silver powder, and a submicron copper powder or a submicron silver plating copper powder. Moreover, the first mixture comprises spherical silver powder in an amount of from 90% by weight to 98% by weight, submicron-sized copper powder or sub-micron-sized silver-plated copper powder in an amount of from 1% by weight to 9% by weight, and in an amount of from 0.2% by weight to 1.2% by weight % of polymeric dispersant. The colloid contains a glass frit having a content of 2% by weight to 5% by weight, and an ionic dispersing agent in an amount of 0.1% by weight to 0.8% by weight.

According to still another embodiment of the present invention, the conductive metal powder comprises a spherical silver powder, and a submicron silver-plated copper powder or a sub-micron silver-plated aluminum powder. Moreover, these conductive metal powders further comprise flake silver powder. In addition, the first mixture comprises spherical silver powder in an amount of 83% by weight to 96% by weight, and the content is 1% by weight to 10% by weight of the micron-sized silver-plated copper powder or the sub-micron-plated silver-plated aluminum powder, the flaky silver powder in an amount of 1% by weight to 6% by weight, and the polymer type dispersing agent in an amount of 0.2% by weight to 1.2% by weight . The colloid contains a glass frit having a content of 2% by weight to 5% by weight, and an ionic dispersing agent in an amount of 0.1% by weight to 0.8% by weight.

According to still another embodiment of the present invention, the conductive metal powder comprises a spherical silver powder and a submicron silver-plated aluminum powder. Moreover, these conductive metal powders further comprise high specific surface area flake silver powder and nano silver powder. Further, the first mixture comprises spherical silver powder in an amount of 79% by weight to 94% by weight, submicron silver-plated aluminum powder in an amount of 2% by weight to 7% by weight, high specific surface area flake silver powder in an amount of 2% by weight to 7% by weight, A nano-sized silver powder having a content of 2% by weight to 7% by weight, and a polymer-based dispersing agent having a content of 0.2% by weight to 1.2% by weight. The colloid contains a glass frit having a content of 2% by weight to 5% by weight, and an ionic dispersing agent in an amount of 0.1% by weight to 0.8% by weight.

According to still another embodiment of the present invention, the raw material of the organic vehicle comprises 1 wt% to 5 wt% of polyvinyl butyral resin, 2 wt% to 16 wt% of ethyl cellulose, and 2 to 10 wt% of rheological properties. Auxiliary, 16% to 25% by weight of diethylene glycol monobutyl ether or 16% to 25% by weight of diethylene glycol monobutyl ether acetate, and terpineol in a residual ratio.

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The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; Flow chart of the method.

The invention provides a low solid content silver conductive adhesive which is suitable for the manufacture of the back electrode of a solar cell. Among them, the solid content of the silver conductive paste can be as low as 40% by weight. Please refer to FIG. 1 , which is a flow chart showing a method for manufacturing a silver conductive paste according to an embodiment of the present invention. In the present embodiment, when the silver conductive paste is prepared, a plurality of conductive metal powders may be provided first as described in step 102 of the method 100. In some embodiments, the conductive metal powder may comprise a globular silver powder, and, for example, a sub-micron copper powder, a sub-micron silver-plated copper powder, a sub-micron silver-plated aluminum powder, a sub-micron silver-plated nickel powder, and/or Or sub-micron silver plated tin powder. In other embodiments, the conductive metal powder may further comprise flake silver powder, nano silver powder and/or high specific surface flake silver powder to promote the sinterability of the silver conductive paste. Wherein, the high specific surface area flake silver powder has a specific surface area greater than or equal to 3 m ² /g.

In one embodiment, after the conductive metal powder is provided, the conductive metal powder may be mixed with a polymeric dispersant at a normal temperature, that is, at about 25 ° C, as described in step 104 to form a first mixture. . This mixing step 104 allows the various conductive metal powders to achieve a preferred dispersion state.

Next, as described in step 106, a plurality of glass frits are provided. In the present embodiment, the glass frit is preferably an environmentally-friendly glass powder that is lead-free, cadmium-free, and flawless. In an embodiment, the glass powder median particle diameter may be, for example, 0.4 μm to 1.0 μm. Further, the softening point cooling temperature of these glass frits may be, for example, 300 ° C to 380 ° C. Then, in one embodiment, the glass frits are mixed with an ionic dispersant at ambient temperature, i.e., at about 25 ° C, as described in step 108 to form a second mixture. This mixing step 108 can make the glass The powder reaches a preferred dispersion state.

Next, as described in step 110, an organic vehicle is provided and the first mixture and the second mixture are uniformly blended in an organic vehicle to form a colloid. In one embodiment, the raw material of the organic vehicle may, for example, comprise 1 wt% to 5 wt% of polyvinyl butyral resin, 2 wt% to 16 wt% of ethyl cellulose, 2 wt% to 10 wt% of rheological property aid, 16 wt% to 25 wt% diethylene glycol monobutyl ether or 16 wt% to 25 wt% diethylene glycol monobutyl ether acetate, and terpineol in a residual ratio. In step 110, the agitation and dissolution treatment of all of the raw materials of the organic vehicle can be carried out at a temperature of from 70 ° C to 90 ° C until a transparent and homogeneous organic vehicle is formed. In an exemplary embodiment, the stirring and dissolution of all of the materials of the organic vehicle can be carried out at a temperature of 85 °C.

In the present embodiment, the total weight content of the first mixture mainly composed of the conductive metal powder and the second mixture mainly composed of the glass frit is referred to as a solid content. In the colloid of an embodiment, the total content of the first mixture and the second mixture may preferably be from 40% by weight to 55% by weight, and the organic vehicle has a content in the remaining proportion. For example, when the total content of the first mixture and the second mixture is 45 wt%, the content of the organic vehicle is 55 wt%. Further, in the colloid, the ratio of the conductive metal powder to the glass frit may preferably be, for example, from 13.0 to 16.0.

Then, as described in step 112, the colloid is abraded using, for example, a three-roller machine to form the desired silver conductive paste. In one embodiment, the colloid may be ground and dispersed to a fineness of less than 8 [mu]m. In addition, depending on the product requirements, when the colloid is ground, a thickener or diluent is added to adjust the silver conductivity. The viscosity of the glue so that the viscosity of the silver conductive paste meets the requirements.

In the present embodiment, a portion of the silver powder is replaced with other non-precious metal powders, particularly non-precious metal powders which are silver plated on the surface. Therefore, in the case of ensuring the conductivity and the tensile force value of the silver conductive paste, the amount of the silver powder of the silver conductive paste can be effectively reduced, and the manufacturing cost of the silver conductive paste can be greatly reduced. In addition, the conductive metal powder may further comprise flake silver powder and/or nano silver powder, thereby increasing the tensile force between the electrode formed by the high temperature sintering of the silver conductive paste and the tantalum substrate of the solar cell, and improving the solar cell. Photoelectric conversion efficiency, and good solderability with tinned copper strips. In addition, the silver conductive paste formed by the method 100 does not contain lead, cadmium and antimony, and is an environmentally friendly material that is environmentally friendly.

The technical contents and effects of the present embodiment will be more specifically described below using a plurality of embodiments and a comparative example.

In Embodiment 1, the conductive metal powder contains a spherical silver powder, and a submicron copper powder or a submicron silver plating copper powder. The conductive metal powder is prepared in a percentage by weight, and the conductive metal powder contains spherical silver powder in an amount of 90% by weight to 98% by weight, and sub-micron-sized copper powder or sub-micron-sized silver-plated copper powder in an amount of 1% by weight to 9% by weight. After mixing these conductive metal powders, these conductive metal powders are mixed at a normal temperature with a polymer type dispersant in an amount of 0.2% by weight to 1.2% by weight to form a first mixture. Therefore, the first mixture comprises spherical silver powder in an amount of 90% by weight to 98% by weight, and conductive metal powder such as submicron-sized copper powder or sub-micron-plated silver-plated copper powder in an amount of 1% by weight to 9% by weight, and the content is 0.2. A wt% to 1.2 wt% polymer type dispersant.

Next, prepare lead-free, cadmium-free and flawless rings by weight percentage Glass powder. These glass powder median diameters may be, for example, from 0.4 μm to 1.0 μm. Further, the softening point cooling temperature of these glass frits may be, for example, 300 ° C to 380 ° C. These glass frits are mixed with an ionic dispersant at room temperature to form a second mixture.

Next, the organic vehicle is prepared in percentage by weight. In the colloid, the raw material of the organic vehicle comprises 1 wt% to 2 wt% of polyvinyl butyral resin, 5 wt% to 12 wt% of ethyl cellulose, 2 wt% to 8 wt% of rheological property aid, and 25 wt%. Diethylene glycol monobutyl ether or 25 wt% diethylene glycol monobutyl ether acetate, and terpineol in a residual ratio. Then, these raw materials are placed in a mixing vessel, and these raw materials are stirred and dissolved at a temperature of, for example, 85 ° C until a transparent and homogeneous organic vehicle is formed.

Then, based on the weight percentage, the first mixture and the second mixture are first supplied, then the organic vehicle is added, and the first mixture, the second mixture and the organic vehicle are placed in the mixing tank. These materials are uniformly stirred in a mixing tank for 30 minutes to 50 minutes to uniformly blend the first mixture and the second mixture in an organic vehicle to form a colloid. In the colloid of this embodiment, the content of the first mixture is 54 wt% to 58 wt%, the content of the glass frit may be 2 wt% to 5 wt%, and the content of the ionic dispersant is 0.1 wt% to 0.8 wt%, and the conductive metal The ratio of powder to glass powder is from 13.0 to 16.0. Moreover, the total content of the first mixture and the second mixture is 60% by weight, and the organic vehicle has a content of the remaining ratio.

Next, the colloid was ground and dispersed by a three-roller machine so that the fineness of the colloid was less than 8 μm. Then, according to the product demand, a thickener or a diluent is added to adjust the viscosity of the silver conductive paste to obtain the desired silver conductive paste.

The obtained silver conductive paste was applied by a screen printing method to a 156 mm × 156 mm polycrystalline silicon wafer (die thickness: 180 μm). Further, the wet film weight of the screen printing was controlled to 60 μg/mm ² , and it was dried at a temperature of 250 ° C to 300 ° C by an infrared heating furnace. Next, the back aluminum paste and the front silver conductive paste were applied, and rapidly sintered at a temperature of 780 ° C to 840 ° C by an infrared heating furnace. The thickness of the backside silver electrode obtained after the treatment was 6 μm to 10 μm, and the tensile force after soldering was 1.8 N/mm. Compared with the control group without adding copper powder and silver-plated copper powder, the tensile value is increased by 0.3 N/mm, and the cost of silver conductive rubber can be reduced by 8% to 10%.

In Embodiment 2, the conductive metal powder comprises a spherical silver powder and a flake silver powder, and a submicron silver plated copper powder or a submicron silver plated aluminum powder. Preparing a conductive metal powder according to a percentage by weight, the conductive metal powder comprising spherical silver powder in an amount of 83% by weight to 96% by weight, submicron silver-plated copper powder or sub-micron silver-plated aluminum powder in an amount of 1% by weight to 10% by weight; The flaky silver powder is contained in an amount of from 1% by weight to 6% by weight. After mixing these conductive metal powders, these conductive metal powders are mixed at a normal temperature with a polymer type dispersant in an amount of 0.2% by weight to 1.2% by weight to form a first mixture. Therefore, the first mixture comprises spherical silver powder in an amount of 83% by weight to 96% by weight, submicron silver-plated copper powder or sub-micron-plated silver-plated aluminum powder in an amount of 1% by weight to 10% by weight, and a content of 1% by weight to 6wt. A conductive metal powder such as flaky silver powder, and a polymer type dispersant in an amount of 0.2% by weight to 1.2% by weight.

Next, prepare lead-free, cadmium-free and flawless environmentally friendly glass powder by weight percentage. These glass powder median diameters may be, for example, from 0.4 μm to 1.0 μm. In addition, the softening point cooling temperature of these glass powders can be, for example, 300 ° C To 380 ° C. These glass frits are mixed with an ionic dispersant at room temperature to form a second mixture.

Next, the organic vehicle is prepared in percentage by weight. In the colloid, the raw material of the organic vehicle comprises 2 wt% to 4 wt% of polyvinyl butyral resin, 6 wt% to 14 wt% of ethyl cellulose, 2 wt% to 8 wt% of rheological property aid, 20 wt% Diethylene glycol monobutyl ether or 20% by weight of diethylene glycol monobutyl ether acetate, and terpineol in a residual ratio. Then, these raw materials are placed in a mixing vessel, and these raw materials are stirred and dissolved at a temperature of, for example, 85 ° C until a transparent and homogeneous organic vehicle is formed.

Then, based on the weight percentage, the first mixture and the second mixture are first supplied, then the organic vehicle is added, and the first mixture, the second mixture and the organic vehicle are placed in the mixing tank. These materials are uniformly stirred in a mixing tank for 30 minutes to 50 minutes to uniformly blend the first mixture and the second mixture in an organic vehicle to form a colloid. In the colloid of this embodiment, the content of the first mixture is 50% by weight to 55% by weight, the content of the glass frit may be 2% by weight to 5% by weight, and the content of the ionic dispersing agent is 0.1% by weight to 0.8% by weight, and the conductive metal The ratio of powder to glass powder is from 13.0 to 16.0. Moreover, the total content of the first mixture and the second mixture is 55 wt%, and the organic vehicle has a content in the remaining ratio.

Next, the colloid was ground and dispersed by a three-roller machine so that the fineness of the colloid was less than 8 μm. Then, according to the product demand, a thickener or a diluent is added to adjust the viscosity of the silver conductive paste to obtain the desired silver conductive paste.

The obtained silver conductive paste was applied by a screen printing method to a 156 mm × 156 mm polycrystalline silicon wafer (die thickness: 180 μm). Further, the wet film weight of the screen printing was controlled to 55 μg/mm ² to 65 μg/mm ² , and dried at a temperature of 250 ° C to 300 ° C by means of an infrared heating furnace. Next, the back aluminum paste and the front silver conductive paste were applied, and rapidly sintered at a temperature of 780 ° C to 840 ° C by an infrared heating furnace. The thickness of the backside silver electrode obtained after the treatment was 4 μm to 8 μm, and the tensile force after soldering was 1.5 N/mm. Compared with the control group without adding silver-plated copper powder and silver-plated aluminum powder, the tensile value is increased by 0.3 N/mm, and the cost of silver conductive adhesive can be reduced by 8% to 10%.

In Example 3, the conductive metal powder comprises a spherical silver powder, a high specific surface area silver powder and a nano silver powder, and a submicron silver-plated aluminum powder. Preparing a conductive metal powder according to a percentage by weight, the conductive metal powder comprising spherical silver powder in an amount of 79% by weight to 94% by weight, submicron silver-plated aluminum powder in an amount of 2% by weight to 7% by weight, and a content of 2% by weight to 7% by weight High specific surface area flake silver powder, and nano silver powder in an amount of 2 wt% to 7 wt%. After mixing these conductive metal powders, these conductive metal powders are mixed at a normal temperature with a polymer type dispersant in an amount of 0.2% by weight to 1.2% by weight to form a first mixture. Therefore, the first mixture comprises spherical silver powder in an amount of 79% by weight to 94% by weight, submicron silver-plated aluminum powder in an amount of 2% by weight to 7% by weight, high specific surface area flake silver powder in an amount of 2% by weight to 7% by weight, And a conductive metal powder such as nanometer silver powder in an amount of 2% by weight to 7% by weight, and a polymer type dispersing agent in an amount of 0.2% by weight to 1.2% by weight.

Next, prepare lead-free, cadmium-free and flawless environmentally friendly glass powder by weight percentage. The glass powder median diameter may be, for example, 0.2 μm to 0.8 μm. Further, the softening point cooling temperature of these glass frits may be, for example, 280 ° C to 350 ° C. Mixing these glasses with an ionic dispersant at room temperature Powder to form a second mixture.

Next, the organic vehicle is prepared in percentage by weight. In the colloid, the raw material of the organic vehicle comprises 3 wt% to 5 wt% of polyvinyl butyral resin, 6 wt% to 16 wt% of ethyl cellulose, 2 wt% to 10 wt% of rheological property aid, 16 wt% Diethylene glycol monobutyl ether or 16% by weight of diethylene glycol monobutyl ether acetate, and terpineol in a residual ratio. Then, these raw materials are placed in a mixing vessel, and these raw materials are stirred and dissolved at a temperature of, for example, 85 ° C until a transparent and homogeneous organic vehicle is formed.

Then, based on the weight percentage, the first mixture and the second mixture are first supplied, then the organic vehicle is added, and the first mixture, the second mixture and the organic vehicle are placed in the mixing tank. These materials are uniformly stirred in a mixing tank for 30 minutes to 50 minutes to uniformly blend the first mixture and the second mixture in an organic vehicle to form a colloid. In the colloid of this embodiment, the content of the first mixture is 45 wt% to 50 wt%, the content of the glass frit may be 2 wt% to 5 wt%, and the content of the ionic dispersant is 0.1 wt% to 0.8 wt%, and the conductive metal The ratio of powder to glass powder is from 13.0 to 16.0. Moreover, the total content of the first mixture and the second mixture is 50% by weight, and the organic vehicle has a content in the remaining ratio.

Next, the colloid was ground and dispersed by a three-roller machine so that the fineness of the colloid was less than 8 μm. Then, according to the product demand, a thickener or a diluent is added to adjust the viscosity of the silver conductive paste to obtain the desired silver conductive paste.

The obtained silver conductive paste was applied by a screen printing method to a 156 mm × 156 mm polycrystalline silicon wafer (die thickness: 180 μm). Further, the wet film weight of the screen printing was controlled to 50 μg/mm ² to 60 μg/mm ² , and it was dried at a temperature of 250 ° C to 300 ° C by an infrared heating furnace. Next, the back aluminum paste and the front silver conductive paste were applied, and rapidly sintered at a temperature of 780 ° C to 840 ° C by an infrared heating furnace. The thickness of the backside silver electrode obtained after the treatment was 4 μm to 6 μm, and the tensile force after soldering was 1.2 N/mm. Compared with the control group without adding silver-plated aluminum powder, high specific surface area silver powder and nano silver powder, the tensile value increased by 0.3 N/mm, and the cost of silver conductive rubber could be reduced by 10%.

In the comparative example, the conductive metal powder contained a spherical or flake silver powder in an amount of 99.5 wt%. After mixing these conductive metal powders, these conductive metal powders were mixed at a normal temperature with a polymer type dispersant having a content of 0.5% by weight to form a first mixture.

Next, prepare lead-free, cadmium-free and flawless green glass powder. These glass powder median diameters may be, for example, from 0.4 μm to 1.0 μm. Further, the softening point cooling temperature of these glass frits may be, for example, 300 ° C to 380 ° C. These glass frits are mixed with an ionic dispersant at room temperature to form a second mixture.

Next, the organic vehicle is prepared in percentage by weight. The raw material of the organic vehicle comprises 5 wt% to 12 wt% of ethyl cellulose, 5 wt% to 18 wt% of a rheological property aid, and terpineol in a residual ratio. Then, these raw materials are placed in a mixing vessel, and these raw materials are stirred and dissolved at a temperature of, for example, 50 ° C until a transparent and homogeneous organic vehicle is formed.

Then, based on the weight percentage, the first mixture and the second mixture are first supplied, then the organic vehicle is added, and the first mixture, the second mixture and the organic vehicle are placed in the mixing tank. Mix these materials evenly in the mixing tank For 40 minutes, the first mixture and the second mixture were uniformly blended in an organic vehicle to form a colloid. In the colloid of this embodiment, the content of the first mixture is from 50% by weight to 52% by weight, the content of the glass frit is from 3% by weight to 5% by weight, and the content of the ionic dispersing agent is from 0.1% by weight to 0.8% by weight. Moreover, the total content of the first mixture and the second mixture is 55 wt%, and the organic vehicle has a content in the remaining ratio.

Next, the colloid was ground and dispersed by a three-roller machine so that the fineness of the colloid was less than 10 μm. Then, according to the product demand, a thickener or a diluent is added to adjust the viscosity of the silver conductive paste to obtain the desired silver conductive paste.

The obtained silver conductive paste was applied by a screen printing method to a 156 mm × 156 mm polycrystalline silicon wafer (die thickness: 180 μm). Further, the wet film weight of the screen printing was controlled to 55 μg/mm ² to 65 μg/mm ² , and dried at a temperature of 250 ° C to 300 ° C by means of an infrared heating furnace. Next, the back aluminum paste and the front silver conductive paste were applied, and rapidly sintered at a temperature of 780 ° C to 840 ° C by an infrared heating furnace. The thickness of the backside silver electrode obtained after the treatment was 4 μm to 8 μm, and the tensile force after soldering was 1.2 N/mm.

It is obvious from the above embodiments that one of the advantages of the present invention is that the silver conductive paste of the present invention is produced by adding a suitable non-precious metal powder such as copper powder, silver plated copper powder, silver plated aluminum powder, silver plated nickel. Powder or silver-plated tin powder is used as a conductive functional material. Thereby, the ratio of the silver content can be lowered while taking into consideration the conductivity of the silver conductive paste. Therefore, not only the conductivity of the back electrode of the solar cell can be ensured, but the solar cell can have excellent light conversion efficiency, and the price of the silver conductive paste can be effectively reduced.

It can be seen from the above embodiments that another advantage of the present invention is that the adhesion of the back electrode to the ruthenium substrate can be enhanced when the back surface electrode of the solar cell is fabricated by using the silver conductive paste produced by the method for producing the silver conductive paste of the present invention. Force, and can improve the solderability between the back electrode and the tinned copper strip. Therefore, the tensile value between the back electrode and the ruthenium substrate and the light conversion efficiency of the solar cell can be improved.

While the present invention has been described above by way of example, it is not intended to be construed as a limitation of the scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

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Claims (17)

A method for manufacturing a silver conductive paste, comprising: providing a plurality of conductive metal powders, wherein the conductive metal powder comprises a spherical silver powder, and a submicron copper powder, a submicron silver plated copper powder, a submicron silver plated aluminum powder Powder, sub-micron-plated silver-plated nickel powder and/or sub-micron-plated silver-plated tin powder; mixing the conductive metal powder with a polymer dispersant at normal temperature to form a first mixture; providing a glass frit; Mixing the glass frit with an ionic dispersant to form a second mixture at normal temperature; providing an organic vehicle; uniformly blending the first mixture and the second mixture in the organic vehicle to form a colloid In the colloid, the total content of the first mixture and the second mixture is 40% by weight to 555% by weight, the organic carrier has a content of the remaining ratio, and the ratio of the conductive metal powder to the glass powder is 13.0. To 16.0; and grinding the colloid to form the silver conductive paste. The method for producing a silver conductive paste according to claim 1, wherein the glass frit has a median diameter of from 0.4 μm to 1.0 μm. The method for producing a silver conductive paste according to claim 1, wherein the conductive metal powder comprises the spherical silver powder, and the sub-micron copper powder or the sub-micron silver-plated copper powder, and the first mixture comprises The spherical silver powder having a content of 90 wt% to 98 wt%, the submicron copper powder having a content of 1 wt% to 9 wt% or the submicron grade a silver-plated copper powder, and the polymer-type dispersant in an amount of 0.2% by weight to 1.2% by weight; and the colloid comprises the glass powder in an amount of 2% by weight to 5% by weight, and the content is 0.1% by weight to 0.8% by weight The ionic dispersant. The method for manufacturing a silver conductive paste according to claim 1, wherein the conductive metal powder comprises the spherical silver powder, and the sub-micron silver-plated copper powder or the sub-micron-plated silver-plated aluminum powder, and the conductive The metal powder further comprises flake silver powder, and the first mixture comprises the spherical silver powder in an amount of 83% by weight to 96% by weight, the submicron silver-plated copper powder in an amount of 1% by weight to 10% by weight or the sub-micron plating a silver aluminum powder, the flake silver powder in an amount of 1% by weight to 6% by weight, and the polymer type dispersing agent in an amount of 0.2% by weight to 1.2% by weight; and the colloid comprises the glass powder in an amount of 2% by weight to 5% by weight And the ionic dispersant in an amount of from 0.1% by weight to 0.8% by weight. The method for manufacturing a silver conductive paste according to claim 1, wherein the conductive metal powder comprises the spherical silver powder and the sub-micron silver-plated aluminum powder, and the conductive metal powder further comprises a high specific surface area flake silver powder. And the nano-sized silver powder, and the first mixture comprises the spherical silver powder in an amount of 79% by weight to 94% by weight, the sub-micron-plated silver-plated aluminum powder in an amount of 2% by weight to 7% by weight, and the content is 2% by weight to 7% by weight The high specific surface area flake silver powder, the nano silver powder in an amount of 2 wt% to 7 wt%, and the high molecular dispersant in an amount of 0.2 wt% to 1.2 wt%; and the colloid comprises a content of 2 wt% to 5 wt% of the glass frit, and the ionic dispersant in an amount of 0.1 wt% to 0.8 wt%. The method for producing a silver conductive paste according to claim 1, wherein the glass frit has a softening point cooling temperature of 300 ° C to 380 ° C. The method for producing a silver conductive paste according to claim 1, wherein the raw material of the organic carrier comprises 1 wt% to 5 wt% of polyvinyl butyral resin, 2 wt% to 16 wt% of ethyl cellulose, 2 wt% to 10 wt%. % rheology additive, 16 wt% to 25 wt% diethylene glycol monobutyl ether or 16 wt% to 25 wt% diethylene glycol monobutyl ether acetate, and terpineol in a residual ratio. The method for producing a silver conductive paste according to claim 1, wherein the step of providing the organic vehicle comprises performing agitation and dissolution treatment of a raw material of the organic vehicle at a temperature of from 70 ° C to 90 ° C. The method for producing a silver conductive paste according to claim 1, wherein the step of grinding the colloid comprises dispersing the colloid to a fineness of less than 8 μm. The method for producing a silver conductive paste according to claim 1, wherein the step of grinding the colloid comprises adding a thickener or a diluent to adjust the viscosity of the colloid. The method for producing a silver conductive paste according to claim 1, wherein the step of grinding the colloid uses a three-roller. A silver conductive paste comprising: a first mixture, wherein the first mixture comprises a plurality of conductive metals Powder and a polymeric dispersant, and the conductive metal powder comprises a spherical silver powder, and a submicron copper powder, a submicron silver plated copper powder, a submicron silver plated aluminum powder, a submicron silver plated nickel powder a powder and/or sub-micron-scale silver-plated tin powder; a second mixture, wherein the second mixture comprises a glass frit and an ionic dispersant; and an organic vehicle, wherein the first mixture is uniformly blended with the second mixture Mixing in the organic vehicle to form a colloid, wherein in the colloid, the total content of the first mixture and the second mixture is 40% by weight to 555% by weight, the organic vehicle has a content of the remaining ratio, and the The ratio of the conductive metal powder to the glass frit is from 13.0 to 16.0. The silver conductive paste of claim 12, wherein the glass frit has a median particle diameter of from 0.4 μm to 1.0 μm. The silver conductive paste of claim 12, wherein the conductive metal powder comprises the spherical silver powder, and the sub-micron copper powder or the sub-micron silver-plated copper powder, and the first mixture comprises a content of 90 wt. % to 98% by weight of the spherical silver powder, the submicron copper powder or the submicron silver plated copper powder in an amount of 1% by weight to 9% by weight, and the polymer type in an amount of 0.2% by weight to 1.2% by weight a dispersant; and the colloid comprises the glass frit in an amount of 2% by weight to 5% by weight, and the ionic dispersing agent in an amount of 0.1% by weight to 0.8% by weight. The silver conductive paste of claim 12, wherein the conductive metal powder comprises the spherical silver powder, and the sub-micron silver-plated copper powder or the sub-micron Grade silver-plated aluminum powder, and the conductive metal powder further comprises flake silver powder, and the first mixture comprises the spherical silver powder in an amount of 83% by weight to 96% by weight, and the content is from 1% by weight to 10% by weight of the sub-micron level a silver-plated copper powder or the micron-sized silver-plated aluminum powder, the flake silver powder in an amount of 1 wt% to 6 wt%, and the polymer dispersant in an amount of 0.2 wt% to 1.2 wt%; and the colloid inclusion content It is 2 wt% to 5 wt% of the glass frit, and the ionic dispersant is contained in an amount of 0.1 wt% to 0.8 wt%. The silver conductive paste of claim 12, wherein the conductive metal powder comprises the spherical silver powder, the sub-micron silver-plated aluminum powder, and the conductive metal powder further comprises a high specific surface area flake silver powder and nanometer. a silver powder, and the first mixture comprises the spherical silver powder in an amount of 79% by weight to 94% by weight, the submicron silver-plated aluminum powder in an amount of 2% by weight to 7% by weight, and the content is 2% by weight to 7% by weight. a specific surface area flake silver powder, the nano silver powder in an amount of 2% by weight to 7% by weight, and the polymer type dispersing agent in an amount of 0.2% by weight to 1.2% by weight; and the colloid comprises a content of 2% by weight to 5% by weight The glass frit, and the ionic dispersant in an amount of from 0.1% by weight to 0.8% by weight. The silver conductive paste of claim 12, wherein the raw material of the organic carrier comprises 1 wt% to 5 wt% of polyvinyl butyral resin, 2 wt% to 16 wt% of ethyl cellulose, and 2 wt% to 10 wt% of stream A property-modifying agent, 16% by weight to 25% by weight of diethylene glycol monobutyl ether or 16% by weight to 25% by weight of diethylene glycol monobutyl ether acetate, and terpineol having a residual ratio.