Technical Field

[0001] The present application relates to a furnace, in particular to a furnace for drying photovoltaic devices.

Background

[0002] In the production of photovoltaic devices such as silicon wafers of crystalline silicon solar cells, a sintering furnace is required to sinter the photovoltaic devices. The sintering furnace typically includes a drying section, a sintering section, and a cooling section. Here, photovoltaic devices printed with paste such as silver paste are transported by a conveyor belt through the drying section, the sintering section and the cooling section in this order, and then transported out of the sintering furnace by the conveyor belt.

Summary

[0003] At least one object in a first aspect of the present application is to provide a furnace, including: a furnace chamber and a conveying device. The furnace chamber includes a heating zone and a cooling zone. The conveying device is used to carry a processing element and move the processing element at a uniform speed to pass through the heating zone and the cooling zone in the furnace chamber sequentially. Here, the furnace is configured such that the processing element moves through the heating zone for 20 to 40 minutes.

[0004] According to the first aspect described above, the furnace is configured to provide heating to dry the processing element, thereby removing solvent materials from the processing element.

[0005] According to the first aspect described above, the processing element is a photovoltaic device.

[0006] According to the first aspect described above, the heating zone includes a plurality of heating units, each heating unit being arranged side-by-side along a length direction of the furnace chamber and configured to each independently provide the heat through a heating element. [0007] According to the first aspect described above, the heating zone includes 12 to 15 heating units, and the length of the heating zone is 4 to 6 m.

[0008] According to the first aspect described above, the cooling zone includes at least one cooling unit, each of the cooling units being arranged side-by-side along the length direction of the furnace chamber and configured to each independently provide cooling through a cooling element.

[0009] According to the first aspect described above, the cooling zone includes 1 to 4 cooling units, and the cooling zone has a length of 0.3 to 0.5 m.

[0010] According to the first aspect described above, the heating zone includes 15 heating units and the cooling zone includes 1 cooling unit.

[0011] According to the first aspect described above, the conveying speed of the conveying device is 100 to 300 mm/min.

[0012] According to the first aspect described above, each of the heating units and each of the cooling units includes: a fan assembly and a divider assembly. Here, the fan assembly and the divider assembly are configured to enable gas in the furnace chamber to flow inside respective units, thereby enabling the heat and cooling provided by the heating element and the cooling element to spread uniformly to the processing element.

[0013] According to the first aspect described above, the furnace further includes two end barriers. The two end barriers are respectively provided at an inlet end and an outlet end of the furnace chamber. Here, each of the end barriers includes a gas curtain device that generates a gas curtain for blocking the flow of air between the interior and exterior environments of the furnace chamber to enable the oxygen content in the gas within the furnace chamber to reach a preset value.

[0014] At least one object in a second aspect of the present application is to provide a sintering furnace including a drying section, a sintering section, and a cooling section. Here, the drying section includes the furnace of any in the first aspect described above.

[0015] Other objects and advantages of the present application will be apparent from the description of the present application hereinafter with reference to the accompanying drawings, and may help with a full understanding of the present application.

Brief Description of Drawings

[0016] Fig. 1A is a perspective view of a furnace according to an example of the present application;

[0017] Fig. 1 B is a front view of the furnace shown in Fig. 1A;

[0018] Fig. 1 C is a schematic diagram of the principle of the furnace shown in Fig. 1A

[0019] Fig. 2A is an exploded view of the furnace in Fig. 1A;

[0020] Fig. 2B is a partial cross-sectional view of the furnace chamber in Fig. 2A along long and width directions;

[0021] Fig. 3 is a schematic view of a sintering furnace including the furnace shown in Fig. 1A.

Detailed Description

[0022] Various specific embodiments of the present application will be described below with reference to the attached drawings that form a part of the present specification. It should be understood that while terms denoting orientation, such as “front,” “rear,” “upper,” “lower,” “left,” “right,” “top,” “bottom,” “inside,” “outside,” etc., are used in the present application to describe various exemplary structural parts and elements of the present application, these terms are used herein for convenience of illustration only and are determined based on the exemplary orientations shown in the attached drawings. Since the examples disclosed in the present application may be disposed in different orientations, these terms denoting orientation are for illustrative purposes only and should not be considered as limiting.

[0023] Figs. 1A to 1C are structural diagrams of a furnace 100 for illustrating an external structure of the furnace 100, in accordance with one example of the present application. Fig. 1A is a perspective view of the furnace 100, Fig. 1 B is a front view of the furnace 100, and Fig. 1C is a simplified schematic diagram of the furnace 100. As shown in Figs. 1A to 1 C, the furnace 100 includes a furnace chamber 112 and a conveying device 118. The furnace chamber 112 includes a heating zone 106, in which gas is heated, and a cooling zone 107, in which gas is cooled. The conveying device 118 is used to carry and move a processing element 110 along the conveying direction, passing through the heating zone 106 and the cooling zone 107 in the furnace 112 chamber sequentially. In the present example, the furnace chamber 112 includes an upper furnace chamber 113 and a lower furnace chamber 114, and a conveying space 120 provided between the upper furnace chamber 113 and the lower furnace chamber 114 and extending along a length direction L of the furnace chamber. The conveying device 118 passes through the furnace chamber 112 along the length direction L of the furnace chamber 112 for carrying the processing element 110 into the conveying space 120 from an inlet end 151 (i.e. , the left end) of the furnace chamber 112 and out from an outlet end 152 (i.e., the right end) of the furnace chamber 112 after moving through the furnace chamber 112 in the conveying space 120. In the present example, the speed at which the conveying device 118 conveys the processing element 110 is substantially uniform, so that the setting facilitates the control of the conveying device 118 on the one hand, and on the other hand facilitates the continuous operation of the furnace 100, such as continuously conveying the processing element 110 by the conveying device 118 into the furnace chamber 112.

[0024] The furnace 100 further includes two end barriers 108 provided at the inlet end 151 and the outlet end 152 of the furnace chamber. The end barriers 108 are used to block the flow of gas between the interior and exterior environments of the furnace chamber 112 so that the oxygen content in the gas inside the furnace chamber 112 can be controlled within a predetermined range. In the present example, each end barrier 108 includes a gas curtain device 209 (see Figs. 2A and 2B) and an exhaust device 154, and the exhaust device 154 is disposed outside of the gas curtain device 209. The exhaust device 154 is used to exhaust air from the inlet end 151 and the outlet end 152 of the furnace chamber. The gas curtain device 209 includes a pair of end barrier boxes 219 (see Figs. 2A and 2B), the air outlets of the pair of end barrier box 219 being placed face to face, and each end barrier box 219 being in fluid communication with an inert gas source to create a gas curtain by the opposing flow of inert gas streams. By providing the exhaust device 154 and the gas curtain device 209, the gas circulation inside and outside the furnace chamber 112 can be reduced or substantially blocked. Although the end barrier box 219 in the upper furnace chamber 113 and the end barrier box 219 in the lower furnace chamber 114 shown in Fig. 1C are connected to different inert gas sources 153a and 153b, in other examples they may also be connected to the same inert gas source. Further, the inert gas source 153a is also in fluid communication with the middle of the furnace chamber 112 to input an inert gas into the interior of the furnace chamber 112. The input inert gas flows from the middle of the furnace chamber 112 in a direction towards the inlet end 151 and the outlet end 152, enabling better blocking of air from the environment outside the furnace chamber 112 from entering the interior of the furnace chamber 112. The specific structure of the gas curtain device 209 will be described in detail with reference to Figs. 2A to 2B. In other examples, the end barrier 108 may also be provided with other structures or other means to block the flow of gas inside and outside the furnace chamber 112, depending on specific needs.

[0025] The heating zone 106 includes a plurality of heating units 101 arranged side- by-side along the length direction L of the furnace chamber 112 and upstream in the conveying direction of the furnace chamber 112. Each heating unit 101 is provided with an independent heating element 103 to each independently provide heat through the heating element 103. In the present example, the heating element 103 is a heating rod, and the number of the heating units 101 is 12 to 15. The cooling zone 107 includes at least one cooling unit 102, and the at least one cooling unit 102 is disposed downstream in the conveying direction of the furnace chamber 112 side by side with the heating units 101 along the length direction L of the furnace chamber 112. Each cooling unit 102 is provided with an independent cooling element 105 to each independently provide cooling through the cooling element 105. In the present example, the cooling element 105 is an air heat exchanger, and the number of the cooling units 102 is 1 to 4.

[0026] In the present example, the processing element 110 is a photovoltaic device, such as a sheet of silicon wafer printed with a slurry, and the furnace 100 is used to dry the photovoltaic device and remove organic matter such as organic solvents in the slurry to facilitate subsequent sintering of the photovoltaic device. The applicants have found that for different slurries, complete removal of organic matter such as organic solvents in the slurries requires that the heating time maintained for the processing element 110 in the heating zone 106 of the furnace chamber 112 is not exactly the same, and that the difference between the heating time required by some slurries can even reach nearly ten times. For example, some slurries require only a few minutes of heating time, while some slurries require tens of minutes of heating time. Adequate heating time will not affect the slurry, but insufficient heating time will cause the organic solvent in the slurry to not be adequately removed. The applicants also have found that the temperature required to generally remove the organic matter from the slurry is not high, and it is generally around 300°C. Therefore, the length of the cooling zone required to cool the photovoltaic device to room temperature is not high. The conversion of a portion of the cooling zone to a heating zone can meet cooling requirements and extend the length of the heating zone with a certain total length of the furnace.

[0027] In the present example, the length of the heating zone 106 is 4 to 6 m and the length of the cooling zone 107 is 0.3 to 0.5 m, so that the time for the processing element 110 to pass through the heating zone 106 can be made to 20 to 40 minutes only by controlling the speed at which the conveying device 118 conveys the processing element 110 to be approximately 100 to 300 mm/minute. As a more specific example, the heating zone 106 includes a total of 15 heating units 101 , that is, Z01 to Z15, the cooling zone 107 includes a total of 1 cooling unit C01 , and the time for the processing element 110 passing through the heating zone 106 is 30 minutes. In this way, the furnace 100 is able to maintain the conveying speed of the conveying device 118 not too low, so that the furnace 100 is able to operate continuously to ensure that the processing element 100 is maintained in the heating zone 106 for sufficient time, thus being suitable for removing organic matter such as organic solvents in most kinds of slurry.

[0028] In other examples, the processing element 110 may also be a circuit board and the furnace 100 is used to reflow solder electronic components on the circuit board.

[0029] Figs. 2A and 2B illustrate the internal structure of the furnace 100 of the present application, where Fig. 2A is an exploded view of the furnace 100 and Fig. 2B is a partial cross-sectional view along one length direction of the furnace chamber 112. As shown in Figs. 2A and 2B, each heating unit 101 is further provided with a fan assembly 104 and a divider assembly 245. By providing separate fan assembly 104 and divider assembly 245 in each heating unit 101 , the gas within each heating unit 101 is able to flow inside the respective unit according to a certain flow path, thereby enabling the heat provided by the heating element 103 to spread evenly to the processing element 110.

[0030] In the present example, each cooling unit 102 is also provided with a fan assembly 104 and a divider assembly 245 so that gas within each cooling unit 102 can flow inside the respective unit according to a certain flow path, thereby enabling the cooling provided by the cooling unit 102 to spread evenly to the processing element 110. The cooling element 105 is a fin heat exchanger including a plurality of fins 246 disposed spaced from and substantially parallel to each other, and cooling water or cooling air circulates inside the fins 246 to provide cooling to the gas circulating between the spaced fins 246.

[0031] The gas curtain device 209 includes a pair of end barrier boxes 219 disposed opposite in the height direction H of the furnace chamber 112. Each end barrier box 219 includes an air inlet 262 and a plurality of guide fins 261 , the end barrier box 219 configured to direct gas entering the end barrier box 219 from the air inlet 262 to flow along each guide fin 261 . For example, an end barrier box 219a located in the upper furnace chamber 113 is configured to direct gas entering the air inlet 262 to flow downward along the guide fins 261 , and an end barrier box 219b located in the lower furnace chamber 114 is configured to direct gas entering the air inlet 262 to flow upward along the guide fins 261 . As such, the gas flowing into the gas inlets 262 of the upper furnace chamber 113 and the lower furnace chamber 114, respectively, can flow relatively to form a gas curtain capable of reducing the inner and outer air flow of the furnace chamber 112.

[0032] The exhaust device 154 is located outside the end barrier box 219a for extracting air at the inlet end 151 and the outlet end 152 of the furnace chamber 112 such that negative pressure is generally able to be formed at the inlet end 151 and the outlet end 152 of the furnace chamber 112. As a result, the gas at the end barrier 108 generally flows from inside the furnace chamber to outside the furnace chamber, thereby better preventing external air from entering the furnace chamber 112. Moreover, after the gas inside the furnace chamber 112 flows outwards, it can also be extracted away by the exhaust device 154 in a timely manner, thereby substantially blocking the gas fluid communication between the internal and external environments of the furnace chamber 112. It should be noted that although only the specific structure of the end barrier 108 at the inlet end 151 of the furnace chamber 112 is shown in Fig. 2B, it can be understood by those skilled in the art that the end barrier 108 of the same structure is also provided at the outlet end 152 of the furnace chamber 112.

[0033] By providing the gas curtain device 209 and the exhaust device 154 of the end barrier 108, and further inputting an inert gas into the middle in the length direction L of the furnace chamber 112, the oxygen content in the gas within the furnace chamber 112 can basically be maintained to a certain range, and this is especially suitable for photovoltaic devices printed with certain slurry.

[0034] Fig. 3 is a schematic view showing a sintering furnace 380 including the furnace 100 shown in Fig. 1A. As shown in Fig. 3, the sintering furnace 380 includes a drying section 370, a sintering section 371 , and a cooling section 372, and the drying section 370, the sintering section 371 , and the cooling section 372 may be connected by a same conveying device 373 or by separate conveying devices. In the drying section 370, the organic matter or the like in the slurry printed on the photovoltaic device can volatilize. In the sintering section 371 , the electrode materials and silicon on the photovoltaic device are heated to a eutectic temperature, and the silicon atoms are dissolved in proportion into the electrode materials in a molten state. In the cooling section 372, the silicon atoms dissolved in the electrode materials are re-crystallized in a solid form such that an ohmic contact is formed between the electrode and the silicon, resulting in a solar cell. In the present example, the drying section 370 includes the furnace 100.

[0035] The drying section, sintering section and cooling section of existing sintering furnaces are generally monolithic structures. Due to the frame structure, it is very difficult to extend the length of the heating zone of the furnace in the drying section separately. The present application makes certain modifications to the reflow furnace to provide a furnace suitable for printing photovoltaic devices of various slurries, particularly suitable for drying sections of sintering furnaces, and can also be used for reflow soldering electronic components on circuit boards.

[0036] The applicants have found that in an existing sintering furnace, when the time for a photovoltaic device passing through the heating zone of the furnace of the drying section is only a few minutes, for the photovoltaic device printed with certain slurry, the organic matter in the slurry cannot be completely removed. By controlling the heating time of the photovoltaic device in the heating zone to 20 to 40 minutes in the present application, most of the organic matter in the slurry can be better removed. In order to ensure the working efficiency of the furnace in the drying section, the conveying speed of the conveying device has a lower limit, and it is not possible to extend the heating time of the photovoltaic device in the heating zone simply by reducing the conveying speed of the conveying device. The present application ensures that the heating time of the photovoltaic device in the heating zone reaches 20 to 40 minutes by extending the length of the heating zone to 4 to 6 m, and the conveying device can still maintain a conveying speed of 100 to 300 mm/min, thereby meeting the requirements of the photovoltaic devices printed with various slurries.

[0037] Moreover, the furnace of the present application includes a plurality of heating units independently providing heat, is capable of independently controlling the temperature for each heating unit such that the interior of the furnace chamber may have a richer temperature profile, thereby providing more possibilities for organic matter in the slurry printed on the photovoltaic device.

[0038] Furthermore, the furnace of the present application may also control the oxygen content in the gas inside the furnace chamber, depending on the specific needs, with particularly good effects on the removal of certain organic matter in the slurry.

[0039] The furnace of the present application may be adapted from a reflow furnace, and it is particularly suitable for drying sections of a sintering furnace in addition to maintaining its function of being used for reflow soldering electronic components on circuit boards.

[0040] Although the present disclosure has been described in connection with examples of the examples outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or foreseeable now or in the near future, may be apparent to those having at least ordinary skill in the art. In addition, the technical effects and/or technical problems described in the present specification are exemplary and not limiting; therefore, the disclosure in the present specification may be used to solve other technical problems and have other technical effects and/or may solve other technical problems.

Therefore, examples of the present disclosure as set forth above are intended to be illustrative and not limiting. Various changes may be made without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to include all known or earlier developed alternatives, modifications, variations, improvements and/or substantial equivalents.