WO2013071830A1

WO2013071830A1 - Roller way type solar cell silicon wafer sintering furnace

Info

Publication number: WO2013071830A1
Application number: PCT/CN2012/084135
Authority: WO
Inventors: 杨桂玲
Original assignee: Yang Guiling
Priority date: 2011-11-16
Filing date: 2012-11-06
Publication date: 2013-05-23
Also published as: CN102393139A

Abstract

A roller way type solar cell silicon wafer sintering furnace. A carrier for transferring a silicon wafer (5) is a roller way (3) capable of transferring along one direction. The roller way (3) comprises a plurality of rotatable rollers. The roller in contact with the silicon wafer (5) is made of a non-metallic material. A forced air cooling zone is arranged between a sintering zone and a blanking zone. The roller way type solar cell silicon wafer sintering furnace can avoid the pollution and the occurrence of "reticulated mottles" of the silicon wafer in the transferring process, increase the transferring speed, realize fast heating and cooling, improve the cell sintering quality, shorten the length of the furnace body, and reduce the energy consumption.

Description

Roller type solar cell wafer sintering furnace

Technical field

The present invention relates to a solar cell wafer sintering furnace, and more particularly to a solar cell wafer sintering furnace using a roller conveyor for transferring silicon wafers. Background technique

In the entire production process of solar cell wafers, the three processes of diffusion, printing and sintering are the most important. Among them, the sintering process is mainly used for drying the slurry printed on the surface of the silicon wafer, burning off the organic solvent volatilized from the slurry, and simultaneously sintering the front and back surfaces of the silicon wafer of the solar cell, so as to be printed on the slurry on the silicon wafer. The metal electrode forms a good ohmic contact with the silicon wafer, which is beneficial to the current output of the battery and exerts the efficiency that the battery should achieve. If the ohmic contact between the silicon wafer and the electrode is poor, a partial current cannot be output, thereby reducing the energy conversion efficiency of the battery. That is to say, the sintering process is a crucial step to make the crystalline silicon wafer truly have photoelectric conversion function, and the quality of the sintering directly affects the efficiency of the final solar cell. Therefore, the performance of the sintering equipment directly affects the quality of the battery.

At present, solar cell manufacturers at home and abroad mainly use mesh belt tunnel sintering furnaces, and preheating and discharging zones, heating zones, sintering zones and cooling zones are sequentially arranged in the longitudinal direction of the sintering furnace. Heat pipes of different densities are arranged in different areas to control the temperature of each zone. The silicon wafer printed with the electrode is transported through the mesh belt, and sequentially passes through different furnace temperature zones of the sintering furnace to complete the electrode sintering process of preheating, discharging, heating, sintering and cooling. Although the mesh belt tunnel sintering technology has been relatively mature, the following problems exist: First, the silicon wafer is in direct contact with the metal mesh belt, and the metal is contaminated with the silicon wafer; Second, the ordinary mesh belt tunnel sintering furnace has a lower running speed. Generally, it is only 2000mm/min. At present, the sintering process of the cell sheet can achieve high-speed sintering of 5000mm/min or more. If the mesh belt tunnel sintering furnace is used for high-speed sintering, the running stability of the mesh belt will be deteriorated. The back electrode surface causes the texture, which affects the appearance quality, and even causes fragmentation. Third, the metal mesh belt will accumulate a large amount of heat, and how the high-speed sintering causes the mesh belt to cool down in a short period of time to ensure the discharge temperature of the battery sheet. A problem that is more difficult to solve; Fourth, due to the heat storage of the mesh belt, the sintering furnace cannot be reached in a short period of time. The sintering temperature required by the process is 850 ° C ~ 950 ° C. After reaching the sintering temperature, even if it is cooled by water, it can not be cooled quickly. It is difficult to meet the requirement of silicon wafer cooling rate of 70 ° 0/8. The effect also increases the length of the heating section and the cooling section of the furnace. Generally, the mesh belt tunnel sintering furnace needs a length of 10 m to 12 m to complete the entire sintering process, thereby increasing the volume and cost of the sintering furnace; The quality is much greater than the quality of the silicon wafer. Therefore, the heat taken away by the heating mesh belt and the cooling mesh belt is much larger than the heat required for the sintering of the silicon wafer, so that the energy consumption of the sintering furnace is greatly improved.

Chinese patent CN102032777A proposes a meshless silicon wafer sintering furnace for the problems of high energy consumption, low thermal efficiency and large surface area of the mesh belt sintering furnace. The working principle is that a conveyor consisting of a set of fixed brackets and moving brackets replaces the metal mesh belt, and the lifting, forward moving, descending and retreating actions are periodically performed by the moving bracket, and will be placed on the fixed bracket. The silicon wafer is gradually moved forward. The fixing bracket and the moving bracket support the wafer support legs made of steel wire and provided with a ceramic coating on the outer surface thereof. Although this patent solves the above-mentioned shortcomings of mesh belt transmission to some extent, the reciprocating handling method still has the following problems: First, the silicon wafer cannot be continuously and smoothly conveyed, and the conveying speed is not easy to be improved, and it is difficult to satisfy 5000 mm. /min's conveying requirements; Second, in order to meet the need of the wafer to continuously move up and down during the handling process, it will increase the effective height inside the furnace, because the upper and lower temperature difference of the furnace temperature is greater than the horizontal temperature difference, this will inevitably cause the silicon wafer After the temperature field fluctuates greatly, the sintering temperature is not easy to accurately control. Third, the transmission process of the silicon wafer is intermittently moved by the interaction of the moving bracket and the fixed bracket, and cannot be continuously and smoothly conveyed. Therefore, it cannot be in the furnace. The temperature measuring device following the movement of the silicon wafer is placed to realize the dynamic temperature measurement of the whole process of sintering the silicon wafer; the fourth is that the supporting leg of the supporting silicon wafer is made of steel wire, and the outer surface thereof is provided with a ceramic coating, due to the steel wire and the ceramic The difference in thermal expansion coefficient of the coating is large, and the ceramic coating is likely to fall off at a high temperature of 850 ° C to 950 ° C. Silicon electroluminescent wire in direct contact with the sheet, whereby the effect of preventing the loss of wafer contamination. To this end, the applicant developed a roller-type solar cell wafer sintering furnace, which effectively solved the shortcomings of the above two transportation methods. Summary of the invention

The present invention is directed to the disadvantages of the prior art, and provides a roller-type solar cell wafer sintering furnace in which a carrier for transporting a silicon wafer is a roller conveyor that can be transported in one direction, and the roller runner includes a plurality of rollers Rotatable roller body. Preferably, the material of the contact portion of the roller table with the silicon wafer is non-metallic; the material of the contact portion of the roller path with the silicon wafer is different from the material for the portion for supporting and driving the roller table. Preferably, the material of the contact portion of the roller table with the silicon wafer is made of a non-metal material, and the material for supporting and driving the portion of the roller table is made of a metal material. Preferably, at least a part of the roller bodies constituting the roller table is a flat roller body having a smooth surface or a roller body having a rough surface. The uneven roller body includes: a threaded roller body having a groove on the surface, a roller body having a plurality of dots or linear projections on the surface, and an unequal roller body having a plurality of rings on the surface. Preferably, at least a portion of the roller bodies constituting the roller table are solid roller bodies or hollow roller bodies. That is to say, the roller bodies constituting the roller table may be solid roller bodies, or may be hollow roller bodies, or may be a roller roller composed of a part of a solid roller body and a part of a hollow roller body. Preferably, the material of the contact portion of the roller table with the silicon wafer is ceramic, quartz ceramic or quartz glass; or the material of the material of the roller contact portion with the silicon wafer is 810 ₂ or Si ₃ N ₄ or SiC, or SiO ^ P A1 ₂ 0 ₃ bonded material. Preferably, the conveying speed of the roller table is arbitrarily adjustable below 15000 mm/min, or the conveying speed is between 4000 mm/min and 12000 mm/min. Preferably, a forced air cooling zone is disposed between the sintering zone and the blanking zone of the sintering furnace, and the silicon wafer is directly cooled into the forced air cooling zone after the sintering is completed; the forced air cooling zone may include: leaving the sintering zone a forced air-cooling zone roller path that continues to be forwarded, and a blowing device disposed above and/or below the forced air-cooling zone roller path; the blowing devices disposed above and below the forced air-cooling zone roller path are disposed opposite each other, and the cold air The wafer is simultaneously blown from the upper and lower directions. Preferably, the cold air blown by the blowing device may be clean air, nitrogen or a mixture of clean air and nitrogen, or the above-mentioned gas which is cooled. Preferably, the blowing pressure of the blowing device is arbitrarily adjustable below 6000 Pa, and the air volume matched thereto satisfies the cooling rate of the silicon wafer of 80 ° C / S. Preferably, the furnace body of the sintering furnace is composed of two parts which can be separated from each other, and the upper part of the furnace body can freely rise upward in the vertical direction under the action of mechanical force. Preferably, the heating mode used in the sintering furnace is a single heat source of infrared radiation heating, microwave heating or electric heating wire heating or any combination of the above three heat sources. The roller-type solar cell wafer sintering furnace provided by the invention has no pollution to the silicon wafer, no netting, no adhesion to the back of the battery, fast conveying speed, small temperature difference, good temperature repeatability and stability, and rapid temperature rise and fall, It does not require water cooling and has a short length, which can greatly reduce energy consumption and improve work efficiency, and can effectively achieve temperature spikes and improve battery sintering quality. DRAWINGS

Figure 1 is a front elevational view showing one embodiment of a roller-type solar cell wafer sintering furnace according to the present invention;

Figure 2 is a side view of Figure 1;

3 is a schematic view showing a structure of a roller body in a silicon wafer sintering furnace for a roller-type solar cell according to the present invention;

Fig. 4 is a view showing another structure of a roller body in a silicon wafer sintering furnace for a roller-type solar cell according to the present invention.

Among them, the reference numerals are as follows:

1 upper furnace body, 2 lower furnace body, 3 roller table, 4 heating pipe, 5 silicon wafer, 6 blowing device, 7 furnace body bracket, 8 hinges, protrusions on 9 roller table, 10 roller road metal support shaft head, 11 bearings, 12-roller thread, 13 non-metallic rings, 14 metal roller shafts.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can refer to the description. As shown in FIG. 1 and FIG. 2, the present invention discloses a solar cell silicon wafer sintering furnace, which is composed of a loading zone, a drying zone, a pre-baking zone, a sintering zone, a forced air cooling zone and a blanking zone. , no traditional network In the water cooling zone required for the belt sintering furnace, the silicon wafer can be directly cooled into the forced air cooling zone after being sintered. The carrier for transporting the silicon wafer is a roller table 3 which can be transported in one direction, and the silicon wafer 5 is supported by a plurality of rotatable high temperature resistant roller bodies, and the silicon wafer is continuously and smoothly transferred horizontally by continuous operation of the roller body. Drying, pre-firing, sintering and cooling are performed in sequence during the transfer. The outer side of the furnace body may be provided with a furnace body bracket 7 for supporting the furnace body. And the furnace body can be divided into an upper furnace body 1 and a lower furnace body 2. The upper furnace body 1 and the lower furnace body 2 can be separated by a drive mechanism for operation or maintenance. This drive mechanism can be a hinge 8. In order to ensure that the silicon wafer 5 is transported at a high temperature of 850 ° C to 950 ° C without contaminating the silicon wafer, the roller lane 3 exposed to the furnace and in contact with the silicon wafer 5 is a non-metal which is resistant to high temperature and has no pollution to the silicon wafer. Material, materials that can be used are 810 ₂ or Si ₃ N ₄ or SiC, or SiO^P A1 ₂ 0 ₃ bonded materials. Among them, the high-purity fused silica ceramic roll and the quartz glass tube are the preferred materials for the transfer sheet of the silicon wafer 5 because they have no pollution to the silicon wafer 5, high temperature performance and relatively low cost. In the present invention, since the roller table 3 which is in contact with the silicon wafer 5 at a high temperature employs a material which does not contaminate the silicon wafer 5, the metal contamination problem caused by the metal mesh belt transmission is effectively eliminated.

In order to ensure good running performance of the roller table and to realize smooth transmission of the silicon wafer 5, the present invention designs a metal and non-metal composite roller table 3. That is, the portion exposed to the furnace and supporting and transporting the silicon wafer 5 is a non-metallic material which is resistant to high temperatures and has no contamination to the silicon wafer 5. The materials that support the transmission on the outside of the furnace and at both ends of the roller are made of metal materials with good wear resistance and easy machining, such as stainless steel, heat-resistant steel, and ordinary steel. The member that functions as a support transmission may be a roller table metal support shaft head 10 that is supported by the bearing 11. The non-metallic portion of the roller table 3 of such a structure is inside the furnace body, and the metal portion is outside the furnace body, which can effectively prevent the non-metallic portion and the metal portion from falling off due to the difference in expansion coefficient like the ceramic coating layer; The non-metallic roller table 3 in the furnace can effectively prevent heat from being conducted through the roller body to the metal support and the transmission mechanism outside the furnace body due to the low thermal conductivity. The metal support and the transmission mechanism are prevented from malfunctioning due to temperature rise or the service life is reduced. Therefore, the composite structure not only achieves the purpose of not polluting the silicon wafer 5, but also ensures that the roller table 3 is long-lasting. Run smoothly. During the continuous transfer of the wafer 5 through the roller table 3, the wafer 5 and the roller body are always in instantaneous contact and in a relative motion state. At the same time, in order to reduce the contact area between the silicon wafer 5 and the support as much as possible, and to reduce heat storage, the bonding and "mesh" phenomenon which may occur in contact with the support of the large area of the silicon wafer 5 is eliminated, as shown in FIG. 3 and FIG. It can be seen that the present invention can be designed with a threaded or annular structure or a plurality of dot-like or linear protrusions on the surface of the roller body. For example, the thread 12 on the roller body in Fig. 3 and the non-metallic ring 13 in Fig. 4. Also, the structure of the above-mentioned thread, ring or projection may be sparsely arranged. For example, it is sparse to each wafer to be in contact with only two annular structures to achieve the transfer of the wafer with a minimum of support points, and the wafer forms a number of instantaneous points or lines with the roller path during operation. The contact, heat and support are relatively uniform, effectively solving the adhesion and "mesh" phenomenon on the back of the silicon wafer, and also solving the problem that the conventional static point support is easy to break due to heat and uneven force. In Fig. 4, the center of the roller body may be a metal roller shaft 14, and a non-metallic ring 13 may be sleeved on the outer side of the metal roller shaft 14. The silicon wafer 5 is only in contact with the non-metallic ring 13. The projection 9 on the roller table is shown in FIG. During the transmission of the silicon wafer 5 through the roller table, it is always moved smoothly and continuously in a horizontal direction, without the ups and downs of the movement process, and at the same time, the silicon wafer 5 can be transported at a constant speed, and the silicon wafer 5 is continuously conveyed. Drying, pre-burning, sintering, and cooling are performed by sequentially passing through the respective temperature zones. Therefore, compared with the conveying method of periodically moving back and forth by the moving carriage to move the silicon wafer 5 forward and backward, the roller conveyor does not disturb the airflow in the furnace, and does not cause fluctuations in the furnace temperature. The silicon wafer 5 moves in the horizontal direction without the upper and lower temperature difference, and moves at a uniform speed, so the sintering temperature is more uniform, the sintering process is consistent, and the battery sintering quality is higher. In addition, this continuous and horizontal transmission mode can be used to measure the temperature of the silicon wafer 5 during the whole process of sintering the silicon wafer 5 like a mesh belt transmission. In order to achieve high battery sintering quality, high work efficiency and maintenance of roller table maintenance, the conveying speed of the roller table can be arbitrarily adjusted below 15000mm/min. The normal working speed is 4000mm/min~ 12000mm/min. Generally, after the silicon wafer 5 is sintered, the cooling rate is as fast as possible, and the cooling rate is preferably greater than 80 ° C / s. The invention provides a forced air cooling zone between the sintering zone and the blanking zone, and the silicon wafer 5 is sintered, directly discharged from the furnace of the sintering furnace, and directly conveyed to the roller table 3 of the forced air cooling zone, and continues to be transported forward. Rapid cooling is achieved during the process to achieve rapid cooling. The manner of achieving forced air cooling may be such that the blowing device 6 is disposed opposite to each other above and below the roller path of the forced air cooling zone. The blowing device 6 can be a wind grille with a plurality of small holes, and the cold air is simultaneously directed from the upper and lower directions to the silicon wafer 5 conveyed on the roller table, so that the silicon wafer 5 is rapidly cooled; usually, the wind turbine is blown toward the silicon wafer 5 The cold air pressure can be arbitrarily adjusted below 6000Pa, and the matching air volume should meet the requirement of the silicon wafer cooling rate of 80 °C / S without fragmentation. The silicon wafer 5 is simultaneously blown from the upper and lower directions in order to cause the cold air to simultaneously act on the upper and lower surfaces of the silicon wafer 5. The up and down pressures that the silicon wafer 5 is subjected to upon cooling are as uniform as possible. One is to make the cooling of the silicon wafer 5 more uniform, and the second is to prevent the silicon wafer 5 from being broken due to the inconsistent force. Further, it is possible to prevent the silicon wafer 5 from changing the running direction and the trajectory under the action of the high-pressure high-speed cold air to affect the normal transmission. The windshield with numerous small holes is set to achieve a certain wind pressure and wind speed, which plays a role in concentrating the airflow cooling of the silicon wafer and quickly taking away heat. The use of clean air, nitrogen or a mixture of clean air and nitrogen as a cooling medium, or the above-mentioned gas is cooled by a cooling device in advance, in order to increase the cooling rate as quickly as possible and to improve the cooling effect. The forced cooling process of the silicon wafer 5 is completed outside the furnace of the sintering furnace, and does not have any influence on the sintering section due to factors such as the flow velocity and the flow direction of the cooling air, thereby ensuring the stability of the sintering process. In addition, when the wafer 5 is transported through the roller table 3, when the silicon wafer 5 is sintered away from the furnace, only the silicon wafer 5 having a small heat capacity enters the forced cooling zone, unlike the mesh belt tunnel sintering furnace, the silicon wafer 5 is required to have a large heat capacity network. The belt is cooled together, so that the silicon wafer transported by the roller table 3 has a better cooling effect. Through the above measures, the cooling rate of the silicon wafer 5 can reach 150 ° C / S or more, and the efficient and rapid cooling of the sintered cell sheet is achieved, the temperature peak effect is achieved, and the sintering quality of the battery is improved. In the present invention, the roller table 3 is always rotated in the fixed position in the sintering furnace, and is rotated by the roller table 3. The dynamic friction forces the silicon wafer 5 forward, and the roller table 3 does not move relatively in the longitudinal direction of the sintering furnace, and only the silicon wafer 3 passes through the sintering furnace longitudinally to complete the entire sintering process. After the roller table 3 is heated to a predetermined temperature in the sintering furnace and reaches the heat balance, the heat is hardly absorbed. Compared with the mesh belt sintering furnace, only the silicon wafer with a small mass takes away heat during the entire sintering process, and the silicon wafer 5 The forced cooling process is also performed outside the furnace of the sintering furnace. Therefore, the roller-type sintering furnace greatly reduces the energy consumption compared with the mesh belt tunnel sintering furnace. Furthermore, hollow roller tables can also be used. The use of hollow roller conveyors can reduce heat storage and reduce energy consumption. In order to facilitate the cleaning operation of the roller table and the debris in the furnace, the sintering furnace body of the present invention is composed of two parts which can be separated from the upper and lower sides, and is bounded by the center line of the horizontal direction of the roller table, and the upper furnace body 1 can be vertically upward. Free rise, the lifting process can be done by hydraulic system or hinge system. In the production process, when abnormal phenomena such as chips and cards are found, the lifting system is started, and the upper furnace body 1 is quickly raised to complete the cleaning and maintenance work. In order to obtain a better heating effect, the heating mode adopted by the present invention is a single heat source of infrared radiation heating, microwave heating or electric heating wire heating or any combination of the above three heat sources, and the heating tube 4 is shown in FIG. . Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the embodiments, and are fully applicable to various fields suitable for the present invention, and are easily accessible to those skilled in the art. The invention is not limited to the specific details and the details shown and described herein, without departing from the scope of the appended claims.

Claims

Claim

A roller-type solar cell wafer sintering furnace, characterized in that, in the sintering furnace, a carrier for transporting a silicon wafer is a roller conveyor that can be transported in one direction, and the roller runner includes a plurality of rotatable rollers body.

2. The roller-type solar cell wafer sintering furnace according to claim 1, wherein the material of the roller contact portion with the silicon wafer is non-metallic.

3. A roller-type solar cell wafer sintering furnace according to claim 2, wherein the material of the roller table used at the point of contact with the silicon wafer is different from the material of the portion for supporting and driving the roller table.

The roller-type solar cell wafer sintering furnace according to any one of claims 2 to 3, wherein the material of the contact portion of the roller table with the silicon wafer is made of a non-metal material for supporting and driving the roller. The material of the track is made of metal.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, characterized in that at least a part of the roller bodies constituting the roller table is a flat roller body having a smooth surface or a surface unevenness Roll body.

6. The roller-type solar cell wafer sintering furnace according to claim 5, wherein the uneven roller body comprises: a threaded roller body having a groove on the surface, and a plurality of dots on the surface Or a linearly convex roller body with an unequal diameter roller body with a plurality of rings on the surface.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, wherein at least a part of the roller bodies constituting the roller table is a solid roller body or a hollow roller body.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, wherein the material of the contact portion of the roller table with the silicon wafer is ceramic, quartz ceramic or quartz glass.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, wherein the material of the contact portion of the roller table with the silicon wafer is &0 ₂ or Si ₃ N ₄ or SiC, or a combination of Si0 ₂ and A1 ₂ 0 ₃ .

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, wherein the conveying speed of the roller table is arbitrarily adjustable below 15000 mm/min, or the conveying speed is 4000 mm. /min ~ between 12000mm/min.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, characterized in that a forced air-cooling zone is provided between the sintering zone and the blanking zone of the sintering furnace, After the silicon wafer is sintered, it directly enters the forced air cooling zone for rapid cooling.

12. The roller-type solar cell wafer sintering furnace according to claim 11, wherein the forced air cooling zone comprises: a forced air cooling zone roller path that continues to be forwarded away from the sintering zone, and is disposed at A blower above and/or below the roller path in the forced air cooling zone.

13. The roller-type solar cell wafer sintering furnace according to claim 12, wherein the blowing devices disposed above and below the roller path of the forced air-cooling zone are disposed opposite to each other, and the cold air is simultaneously blown from the upper and lower directions. To the silicon wafer.

The roller-type solar cell wafer sintering furnace according to any one of claims 12 to 13, wherein the cold air blown by the blowing device is clean air, nitrogen or a mixture of clean air and nitrogen, or The above-mentioned gas that has been cooled.

The roller-type solar cell wafer sintering furnace according to any one of claims 12 to 13, wherein the blowing pressure of the blowing device is arbitrarily adjustable below 6000 Pa, and the matching air volume satisfies the silicon wafer. Cooling rate 80 °C / s.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, wherein the furnace body of the sintering furnace is composed of two parts which can be separated from each other, the upper part The furnace body can rise freely upward in the vertical direction under the action of mechanical force.

The roller-type solar cell wafer sintering furnace according to any one of claims 1 to 3, wherein the sintering furnace uses a heating method of infrared radiation heating, microwave heating or electric heating wire heating. A single heat source or any combination of the above three heat sources.