A modular heating stage with high temperature uniformity and temperature control method

Abstract

The application relates to the technical field of semiconductor manufacturing, in particular to a high-temperature-uniformity modular heating table and a temperature control method. The high-temperature-uniformity modular heating table comprises a heating table, a first oil pump, a second oil pump and a controller; the heating table comprises a heating module array, a heating box body and a cover plate arranged on the heating box body, the upper surface of the cover plate is used for placing a target substrate, the heating box body is provided with an oil bath cavity, the oil bath cavity is used for filling an oil bath medium, and the heating module array is arranged in the oil bath cavity. The high-temperature-uniformity modular heating table can realize high-uniform distribution of temperature, reduce the influence of temperature gradient on alignment accuracy, improve the precision and yield of chip transfer, has good cooling and heat dissipation effects, has accurate temperature control, and solves the problems that air turbulence and substrate thermal warping caused by the existing temperature gradient influence the transfer precision of equipment.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a modular heating stage with high temperature uniformity and a temperature control method. Background Technology

[0002] In micro-LED mass transfer, LED chips need to be flip-chip mounted onto a target substrate, requiring a positioning and alignment accuracy of less than 5μm between the chip bumps and the target substrate. This places extremely high demands on the alignment between the chip and the target substrate, and also imposes stringent requirements on the working environment, necessitating a windless environment; otherwise, chip misalignment may occur. Excessive deviation in positioning and alignment between the chip and the target substrate will reduce the yield of the final product. In actual processing, due to process constraints, laser mass transfer first uses a UV laser beam to penetrate a glass substrate and strike the elastic dynamic release layer. At this point, air bubbles are generated between the elastic dynamic release layer and the glass substrate, causing the LED chip to detach and fall onto the target substrate. Simultaneously, a heating platform is used to heat the target substrate to over 200°C to melt the LED chip solder joints and fuse them with the substrate, ensuring stable bonding when the LED chip falls onto the target substrate. Afterward, cooling is achieved by the heating platform or other cooling methods to lower the temperature of the LED chip and the target substrate, resulting in stable bonding.

[0003] It is evident that the heating and cooling times of the heating stage are directly related to the efficiency of laser mass transfer. Furthermore, due to the process constraints of laser mass transfer, the working area is kept as windless as possible, resulting in the absence of cooling fans or other heat dissipation facilities. This leads to poor heat dissipation, and the temperature gradient generated by this heat causes thermal distortion in the heating platform structure. This distortion results in unevenness of the target substrate, leading to decreased transfer accuracy and yield. Simultaneously, atmospheric turbulence caused by the temperature gradient may cause chip drift during the drop process, affecting transfer accuracy. In addition, it can also affect the accuracy of the alignment sensor. Therefore, minimizing the impact of temperature gradients on the platform structure and sensor accuracy in laser mass transfer equipment with poor heat dissipation and micron-level alignment accuracy requirements has become a challenging problem.

[0004] Typically, heating platforms are made of materials with high rigidity or low temperature sensitivity to reduce thermal distortion caused by temperature. At the same time, the heating platform needs to be machined to be as flat as possible. However, in actual production, the influence of temperature gradients increases the occurrence of unevenness or inconsistent surface contours of the heating platform, thus affecting the alignment accuracy.

[0005] Current technologies primarily involve adding a compliant material layer to the platform. Industrially, thermal insulation materials are also commonly used to insulate the heat source of the heating platform to mitigate temperature gradient issues. This approach passively reduces surface distortion, has limitations, and cannot control the impact of the heating platform's heat source and the temperature gradient caused by its temperature difference on the sensor. Currently, with the pursuit of efficiency, panel and wafer sizes are constantly increasing, and chip sizes are continuously shrinking, leading to increasingly stringent requirements for the flatness of the heating platform surface, which traditional passive solutions struggle to meet. On the other hand, some solutions improve the alignment accuracy of the equipment by updating and iterating alignment methods, strategies, or systems, but these solutions also suffer from time consumption and low efficiency. All of the above solutions optimize a single objective without coupling these objectives and factors together. In fact, part of the problem stems from the uneven heat dissipation from the heating platform, resulting in temperature gradients that affect the sensor and platform architecture, thus causing errors. Summary of the Invention

[0006] In response to the problems raised in the background technology, the purpose of this invention is to propose a modular heating stage with high temperature uniformity, which can achieve high temperature uniformity distribution, reduce the impact of temperature gradient on alignment accuracy, improve the accuracy and yield of chip transfer, have good cooling and heat dissipation effects, and precise temperature control. It solves the problems of air turbulence caused by temperature gradient and substrate thermal warping affecting the transfer accuracy of the equipment.

[0007] Another objective of this invention is to propose a temperature control method for a modular heating stage with high temperature uniformity, which can control the heating and cooling process of the heating stage in real time according to the temperature of the heating stage, effectively improving the heating and cooling efficiency.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] A modular heating stage with high temperature uniformity includes a heating stage, a first oil pump, a second oil pump, and a controller;

[0010] The heating stage includes a heating module array, a heating box, and a cover plate covering the heating box. The upper surface of the cover plate is used to place the target substrate. The heating box is provided with an oil bath cavity, which is filled with an oil bath medium. The heating module array is located inside the oil bath cavity and is immersed in the oil bath medium. The heating module array is composed of multiple heating unit blocks. The heating unit blocks are made of porous material. Each heating unit block has a heater placement cavity and a temperature sensor placement cavity. A heater is installed in the heater placement cavity, and a first temperature sensor is installed in the temperature sensor placement cavity. The heating module array is used to heat the heating stage. A second temperature sensor is provided on the surface of the cover plate.

[0011] The input end of the first oil pump is connected to a cold oil source, and the output end of the first oil pump is connected to the cold oil input end of the heating box. The first oil pump is used to input cooled oil bath medium into the oil bath cavity. The input end of the second oil pump is connected to the hot oil output end of the heating box. The second oil pump is used to discharge the heated oil bath medium out of the oil bath cavity.

[0012] The signal output terminals of the first temperature sensor and the second temperature sensor are respectively connected to the signal input terminal of the controller, and the heater, the first oil pump and the second oil pump are respectively connected to the controller.

[0013] To further explain, the heating unit block is in the shape of a hexagonal prism, and each of the six sides of the heating unit block is provided with a first insert structure. Multiple heating unit blocks are spliced ​​together through the first insert structure to obtain the heating module array.

[0014] To further explain, the first insert structure is a recessed groove facing the inner side of the heating unit block, or the first insert structure is a protruding block facing the outer side of the heating unit block, and the block cooperates with the groove.

[0015] To further explain, the inner wall of the heating box is provided with a second insert structure, which cooperates with the first insert structure, and the heating module array is engaged with the second insert structure through the first insert structure.

[0016] Furthermore, a flexible material layer is provided between the heating module array and the cover plate, and a heat insulation material layer is provided on the outer cover of the heating box.

[0017] To further explain, it also includes an oil cooling device, wherein the output end of the second oil pump is connected to the input end of the oil cooling device, and the output end of the oil cooling device is connected to a cold oil recovery container.

[0018] To further clarify, the cover plate is made of solid ceramic plate, and the heating box body is made of solid metal plate.

[0019] To further explain, the heating unit block is made of metal or alloy and refractory metal carbides, nitrides, borides and silicides, and the oil bath medium is any one of methyl silicone oil, soybean oil, cottonseed oil and heat transfer oil.

[0020] A temperature control method, applied to the aforementioned modular heating stage with high temperature uniformity, includes the following steps:

[0021] Step S1: Obtain the initial heat flux density and ambient temperature, wherein the ambient temperature is the surface temperature of the cover plate;

[0022] Step S2: Predict the heating time required to reach the first target temperature, where the first target temperature is the temperature that the cover plate needs to reach after heating.

[0023] Step S3: Control the heating module array to heat according to the initial control model and the predicted heating time. The control model is a feedforward feedback integrated control.

[0024] Step S4: Obtain the actual temperature of the cover plate after heating;

[0025] Step S5: Determine whether the absolute value of the temperature difference between the actual temperature and the first target temperature is within the first difference range. If not, adjust the heating power of the heating unit block, continue to heat up, and return to step S4. If yes, execute step S6.

[0026] Step S6: Control the heating module array to heat according to the set heating time;

[0027] Step S7: Control the heating module array to stop heating and control the second oil pump to start;

[0028] Step S8: Obtain the current temperature of the cover plate after cooling;

[0029] Step S9: Determine whether the absolute value of the temperature difference between the current temperature and the second target temperature is within the second difference range. If not, control the second oil pump to keep it on and continue cooling before returning to step S8. If yes, execute step S10, where the second target temperature is the temperature to be reached after cooling.

[0030] Step S10: Control the second oil pump to shut down;

[0031] Step S11: End cooling.

[0032] Furthermore, the method also includes a step of optimizing the control model, which includes:

[0033] Step A1: Initialize the heat flux density, heating time, and model parameters of the control model;

[0034] Step A2: Control the execution of steps S1 to S10;

[0035] Step A3: Determine if it is the optimal solution. If yes, end the process; otherwise, proceed to step A4.

[0036] Step A4: Calculate and sort the fitness of individual solutions;

[0037] Step A5: Perform selection, crossover, and mutation operations sequentially to obtain new values ​​for the model parameters of the control model;

[0038] Step A6: Substitute the new values ​​into the numerical population and the model parameters of the control model, then proceed to step A2.

[0039] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0040] By using a heating module array, a highly uniform temperature distribution can be achieved, avoiding the impact of air turbulence and substrate thermal warping caused by temperature gradients on the transfer accuracy of the equipment. Furthermore, using a hot oil bath in conjunction with the heating module array further improves the temperature uniformity of the heating stage, thereby reducing the impact of temperature gradients on alignment accuracy and further improving the temperature gradient problem around the heating stage. This ensures the accuracy and yield of LED chip transfer and effectively avoids affecting the accuracy of the alignment sensor in the transfer equipment. The heating unit blocks are made of porous materials and employ sweating cooling technology during cooling, effectively improving cooling efficiency and heat dissipation. This effectively avoids thermal distortion of the heating platform structure caused by temperature gradients resulting from difficult-to-dissipate heat. By using a controller to control the heat source temperature and setting a first temperature sensor matched to the heater, the temperature of the heating stage can be controlled more precisely. Attached Figure Description

[0041] Figure 1 This is a three-dimensional structural schematic diagram of a modular heating platform with high temperature uniformity according to an embodiment of the present invention.

[0042] Figure 2 This is a perspective sectional view of a modular heating platform with high temperature uniformity according to an embodiment of the present invention.

[0043] Figure 3 This is a three-dimensional structural diagram of the heating module array of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0044] Figure 4 This is a three-dimensional structural diagram of the heating unit block of the heating module array of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0045] Figure 5 This is a perspective sectional view of the heating unit block of the heating module array of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0046] Figure 6 This is a perspective sectional view of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0047] Figure 7 This is a perspective sectional view of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0048] Figure 8 This is a three-dimensional structural diagram of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0049] Figure 9 This is a three-dimensional structural diagram of a modular heating stage with high temperature uniformity according to an embodiment of the present invention.

[0050] Figure 10 This is a schematic flowchart of a temperature control method according to an embodiment of the present invention;

[0051] Figure 11 This is a schematic diagram of the process for optimizing the control model according to an embodiment of the present invention;

[0052] Figure 12 This is a schematic diagram of a temperature control method according to an embodiment of the present invention, combined with the optimization of the control model;

[0053] The components include: heating platform 1, heating box 11, oil bath chamber 111, second insert structure 112, circuit interface 113, oil bath medium injection interface 114, oil bath medium discharge interface 115, cover plate 12, heating module array 13, heating unit block 131, heater placement chamber 1311, temperature sensor placement chamber 1312, first insert structure 1313, slot 1314, card block 1315, heater circuit slot 1316, temperature sensor circuit slot 1317, flexible material layer 14, heat insulation material layer 15, first oil pump 2, second oil pump 3, controller 4, oil cooling device 5, and connecting lines 6. Detailed Implementation

[0054] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0055] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, features defined with "first" and "second" may explicitly or implicitly include one or more of these features, used to distinguish and describe features, without any order or emphasis.

[0056] In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0057] like Figures 1 to 9 As shown, a modular heating platform with high temperature uniformity includes a heating platform 1, a first oil pump 2, a second oil pump 3, and a controller 4.

[0058] The heating stage 1 includes a heating module array 13, a heating box 11, and a cover plate 12 covering the heating box 11. The upper surface of the cover plate 12 is used to place the target substrate. The heating box 11 is provided with an oil bath cavity 111, which is used to fill an oil bath medium. The heating module array 13 is disposed in the oil bath cavity 111 and immersed in the oil bath medium. The heating module array 13 is composed of multiple heating unit blocks 131 spliced ​​together. The heating unit blocks 131 are made of porous material. The heating unit blocks 131 have a heater placement cavity 1311 and a temperature sensor placement cavity 1312. The heater placement cavity 1311 is provided with a heater, and the temperature sensor placement cavity 1312 is provided with a first temperature sensor. The heating module array 13 is used to heat the heating stage 1. The surface of the cover plate 12 is provided with a second temperature sensor.

[0059] The input end of the first oil pump 2 is connected to a cold oil source, and the output end of the first oil pump 2 is connected to the cold oil input end of the heating box 11. The first oil pump 2 is used to input a cooled oil bath medium into the oil bath chamber 111. The input end of the second oil pump 3 is connected to the hot oil output end of the heating box 11. The second oil pump 3 is used to discharge the heated oil bath medium from the oil bath chamber 111.

[0060] The signal output terminals of the first temperature sensor and the second temperature sensor are respectively connected to the signal input terminal of the controller 4. The heater, the first oil pump 2 and the second oil pump 3 are respectively connected to the controller 4.

[0061] By configuring the heating module array 13, which is composed of multiple heating unit blocks 131, the smaller size of each heating unit block 131 reduces its heat capacity, allowing it to reach the specified temperature more quickly and effectively improving heating efficiency. Furthermore, the modular structure of the multiple heating unit blocks 131 gives the heating module array 13 a modular feature, allowing for adjustments to the heating area by increasing or decreasing the number of heating unit blocks 131 according to actual production needs. Furthermore, by setting the oil bath chamber 111 inside the heating box 11, the heating module array 13 is completely immersed in the oil bath medium. Heating is achieved by the heater in each heating unit block 131, thus realizing a hot oil bath. An oil bath is a hot bath method that uses oil as the heat bath substance. The controller 4 is communicatively connected to the first temperature sensor and the heater. The first temperature sensor can detect the real-time temperature of the heating unit block 131. The controller 4 controls the heating power of each heating unit block 131 according to the real-time temperature of the heating unit block 131, thereby changing the heat flux density and temperature of a single heating unit block 131. The second temperature sensor can measure the actual temperature of the heated cover plate 12 to determine whether the cover plate 12 has reached the temperature required for LED chip transfer bonding. Using the hot oil bath method for heating can make the overall temperature distribution of the heating platform 1 highly uniform and effectively reduce the impact of temperature gradient.

[0062] It is worth noting that the heating platform 1 of the present invention employs a sweating cooling technology, a biomimetic technique that mimics the principle of human body regulating temperature through sweating. By setting up the first oil pump 2 and the second oil pump 3, when the heating platform 1 needs cooling, the first oil pump 2 rapidly pumps external cooling oil bath medium into the oil bath chamber 111, while the second oil pump 3 discharges the heated oil bath medium from the oil bath chamber 111. At this time, since the heating unit block 131 is made of a porous material, the pumped cooling oil bath medium, like sweat, permeates through the "sweat pores" of each heating unit block 131, cooling and carrying away heat from the components, thus lowering their temperature. Simultaneously, the cooling oil bath medium seeping from the "sweat pores" of each heating unit block 131 forms a heat insulation layer on the upper surface of the heating module array 13, effectively isolating the heating module array 13 from the cover plate 12, further cooling the cover plate 12, and effectively improving cooling efficiency. It should be noted that the cold oil source can be a container filled with cooling oil bath medium.

[0063] The present invention utilizes the heating module array 13 to achieve highly uniform temperature distribution, avoiding the impact of air turbulence and substrate thermal warping caused by temperature gradients on the transfer accuracy of the equipment. Furthermore, the use of a hot oil bath in conjunction with the heating module array further improves the temperature uniformity of the heating platform 1, thereby reducing the impact of temperature gradients on alignment accuracy and further improving the temperature gradient problem around the heating platform 1. This ensures the accuracy and yield of LED chip transfer and effectively avoids affecting the accuracy of the alignment sensor in the transfer equipment. The heating unit block 131 is made of porous material and employs a sweating cooling technology during cooling, effectively improving cooling efficiency and heat dissipation. This effectively avoids thermal distortion of the heating platform structure caused by temperature gradients resulting from difficult-to-dissipate heat. By using the controller 4 to control the heat source temperature and setting a first temperature sensor matched to the heater, the temperature of the heating platform 1 can be controlled more precisely.

[0064] This invention, while taking into account platform structural distortion, also reduces the impact on chip drop and sensors by decreasing the overall temperature gradient, effectively improving chip transfer accuracy. This invention improves chip transfer accuracy through proactive distortion reduction, resulting in higher efficiency compared to traditional solutions.

[0065] To further explain, the heating unit block 131 is a hexagonal prism, and each of the six sides of the heating unit block 131 is provided with a first insert structure 1313. Multiple heating unit blocks 131 are spliced ​​together through the first insert structure 1313 to obtain the heating module array 13.

[0066] The heating module array 13 is formed by splicing the heating unit blocks 131 together using the first insert structure 1313. The first insert structure 1313 is located on the six sides of the heating unit blocks 131, allowing multiple heating unit blocks 131 to be spliced ​​together. Using the insert structure can reduce the volume of a single heating unit block 131, thereby reducing its heat capacity and enabling it to reach the specified temperature faster and better, thus improving heating efficiency. On the other hand, using the insert structure makes the heating module array 13 modular, allowing the heating unit blocks 131 to be added or removed according to actual production needs, facilitating the adjustment of the heating area to adapt to changes in wafer size specifications, thus having wide applicability.

[0067] Furthermore, each independent heating unit block 131 has an independent heater placement cavity 1311 and a temperature sensor placement cavity 1312, which are used to place the heater and the first temperature sensor, respectively. This allows the heating unit block 131 to be prefabricated independently, enabling mass production. Specifically, the heater is a PTC heater, which features rapid heating and convenient placement.

[0068] To further explain, the first insert structure 1313 is a recessed groove 1314 facing the inner side of the heating unit block 131, or the first insert structure 1313 is a protruding block 1315 facing the outer side of the heating unit block 131, and the block 1315 cooperates with the groove 1314.

[0069] Specifically, the first insert structure 1313 on one side of one of the heating unit blocks 131 is a recessed slot 1314 facing the inner side of the heating unit block 131, and the first insert structure 1313 on one side of the other heating unit block 131 is a protruding block 1315 facing the outer side of the heating unit block 131. The two heating unit blocks 131 are spliced ​​by the block 1315 being engaged in the slot 1314. Similarly, the other heating unit blocks 131 are spliced ​​in the same way to finally obtain the heating module array 13, which has the characteristics of modularity, simple splicing method, and convenient addition or removal of heating unit blocks 131.

[0070] Preferably, the shape of the slot 1314 and the shape of the block 1315 are both wedge-shaped, which makes the engagement between the two heating unit blocks 131 more secure.

[0071] Preferably, the inner sidewall of the heating box 11 is provided with a second insert structure 112, which cooperates with the first insert structure 1313, and the heating module array 13 is engaged with the second insert structure 112 through the first insert structure 1313.

[0072] To better install and fix the heating module array 13, a second insert structure 112 is also provided on the inner side of the heating box 11. Since the second insert structure 112 cooperates with the first insert structure 1313, it facilitates the fixing and installation of the heating module array 13. Specifically, the second insert structure 112 also has the same slot 1314 and the same block 1315 as the first insert structure 1313. The heating module array 13 is installed and fixed in the heating box 11 by the block 1315 of the first insert structure 1313 engaging with the slot 1314 of the second insert structure 112, or by the block 1315 of the second insert structure 112 engaging with the slot 1314 of the first insert structure 1313.

[0073] Preferably, a flexible material layer 14 is provided between the heating module array 13 and the cover plate 12, and a heat insulation material layer 15 is provided on the outside of the heating box body 11.

[0074] In this embodiment, the second insert structure 112 is slightly higher than the first insert structure 1313. Considering the thermal distortion of porous materials after heating, to prevent the thermal distortion from affecting the cover plate 12, in addition to leaving a gap between the heating module array 13 and the cover plate 12, an additional flexible material layer 14 is placed so that the upper end surface of the heating module array 13 is in contact with the lower end surface of the flexible material layer 14, and the upper end surface of the flexible material layer 14 is in contact with the lower end surface of the cover plate 12, further reducing the impact of the thermal distortion of the lower heating module array 13 on the surface flatness of the upper cover plate 12. Preferably, the flexible material layer 14 is made of a high-temperature resistant flexible material, such as fluororubber or silicone rubber film (PDMS).

[0075] Furthermore, by providing the heat insulation layer 15, the internal heat source can be isolated from the heat exchange with the external environment, thereby reducing the impact of environmental and other factors on the heating platform, and further reducing the impact of the heating module array 13 on external device sensors. Preferably, the heat insulation layer 15 is made of materials such as glass fiber or polyurethane.

[0076] To further explain, it also includes an oil cooling device 5, the output end of the second oil pump 3 is connected to the input end of the oil cooling device 5, and the output end of the oil cooling device 5 is connected to the cold oil recovery container.

[0077] In laser mass transfer, besides heating to melt the LED chip solder joints and fuse them with the substrate, cooling is also required to solidify the solder joints, thus completing the welding process. When the heating stage 1 needs cooling, the first oil pump 2 rapidly pumps external cooling oil bath medium into the oil bath chamber 111, while the second oil pump 3 discharges the heated oil bath medium from the oil bath chamber 111. The hot oil is then cooled by the oil cooling device 5 and transported to the cold oil recovery container for reuse in the next cooling cycle. Specifically, the oil cooling device 5 is communicatively connected to the controller 4, which controls the opening and closing of the oil cooling device 5. The oil cooling device 5 is an air-cooled oil cooler, which has the advantages of fast cooling speed and environmental friendliness.

[0078] To further explain, the side wall of the heating box 11 is provided with a line interface 113, an oil bath medium injection interface 114, and an oil bath medium discharge interface 115. The heating unit block 131 is provided with a heater line groove 1316 and a temperature sensor line groove 1317. The top of the heater line groove 1316 is connected to the heater placement cavity 1311, and the bottom of the heater line groove 1316 is provided through the heating unit block 131. The heater is connected to the controller 4 through a connecting line 6. The heater line groove 1316 provides passage for the connecting line 6 connected to the heater.

[0079] The top of the temperature sensor wiring slot 1317 is connected to the temperature sensor placement cavity 1312, and the bottom of the temperature sensor wiring slot 1312 is disposed through the heating unit block 131. The first temperature sensor is connected to the controller 4 via a connecting line 6. The temperature sensor wiring slot 1317 provides passage for the connecting line 6 connected to the first temperature sensor. The wiring interface 113 provides passage for the connecting line 6 connected to the heater and the connecting line 6 connected to the first temperature sensor.

[0080] Preferably, the sidewall of the heat insulation material layer 15 is also provided with the circuit interface 113, the oil bath medium injection interface 114 and the oil bath medium discharge interface 115, and the circuit interface 113, the oil bath medium injection interface 114 and the oil bath medium discharge interface 115 of the heat insulation material layer 15 are respectively provided in a one-to-one correspondence with the circuit interface 113, the oil bath medium injection interface 114 and the oil bath medium discharge interface 115 of the heating box body 11.

[0081] To further explain, considering the density of the oil bath medium after heating and the achievement of sweating and cooling, in this embodiment, an oil bath medium injection port 114 is provided at the lower part of the side wall of the heating box 11, and an oil bath medium discharge port 115 is provided at the upper part of the side wall of the heating box 11 opposite to the oil bath medium injection port 114. The output end of the first oil pump 2 is connected to the oil bath medium injection port 114, and the input end of the second oil pump 3 is connected to the oil bath medium discharge port 115.

[0082] Preferably, the cover plate 12 is made of solid ceramic plate, and the heating box body 11 is made of solid metal plate.

[0083] Since the cover plate 12 is in direct contact with the target substrate, the cover plate 12 is made of solid ceramic plate. Specifically, the ceramic material of the solid ceramic plate is silicon carbide (SiC). The reason for choosing this material is that, on the one hand, its average coefficient of thermal expansion is only 4.4×10^-6 / ℃ in the range of 25℃ to 1400℃, and its thermal distortion affected by temperature is minimal; on the other hand, it has a very high thermal conductivity of 58.6W / m·k, which is very suitable as a platform material for heating the target substrate. In addition, it can also prevent the escape of the oil bath material below.

[0084] Furthermore, the heating box body 11 is made of solid metal plate, specifically Invar steel, which has the characteristic that deformation is minimally affected by temperature. The specific grade can be 4J32, which has the lowest coefficient of thermal expansion.

[0085] To further explain, the heating unit block 131 is made of metal or alloy and refractory metal carbides, nitrides, borides and silicides, and the oil bath medium is any one of methyl silicone oil, soybean oil, cottonseed oil and heat transfer oil.

[0086] The heating unit block 131 is made of a porous material with a novel mesh structure and pore structure. It can be made of various metals or alloys, as well as carbides, nitrides, borides, and silicides of refractory metals. In this design, stainless steel and ceramic materials can be used, such as foamed alumina ceramic. The porous material allows the heating unit block 131 to be completely immersed in an oil bath medium, thus achieving a hot oil bath. An oil bath is a heating method that uses oil as the heating medium. Since the surface temperature of the cover plate 12 will exceed 180°C during the chip flipping process, high-temperature silicone oil, soybean oil, cottonseed oil, and thermally conductive oil with boiling points higher than 180°C are selected as the oil bath medium. Methyl silicone oil is usually dimethyl silicone oil, with a typical operating temperature of 200°C; different models can be selected depending on the specific application. Soybean oil has a boiling point of 230°C and a freezing point below -10°C, as does cottonseed oil. While heat transfer oil is the cheapest medium for oil baths, long-term use at high temperatures can easily lead to problems such as the generation of gas, tar, and pipe blockage. Using a hot oil bath method for heating can ensure a uniform temperature distribution across the heating platform 1, effectively reducing the impact of temperature gradients.

[0087] like Figure 10 As shown, a temperature control method, applied to the modular heating stage with high temperature uniformity, includes the following steps:

[0088] Step S1: Obtain the initial heat flux density and ambient temperature, wherein the ambient temperature is the surface temperature of the cover plate;

[0089] Step S2: Predict the heating time required to reach the first target temperature, where the first target temperature is the temperature that the cover plate needs to reach after heating.

[0090] Step S3: Control the heating module array to heat according to the initial control model and the predicted heating time. The control model is a feedforward feedback integrated control.

[0091] Step S4: Obtain the actual temperature of the cover plate after heating;

[0092] Step S5: Determine whether the absolute value of the temperature difference between the actual temperature and the first target temperature is within the first difference range. If not, adjust the heating power of the heating unit block, continue to heat up, and return to step S4. If yes, execute step S6.

[0093] Step S6: Control the heating module array to heat according to the set heating time;

[0094] Step S7: Control the heating module array to stop heating and control the second oil pump to start;

[0095] Step S8: Obtain the current temperature of the cover plate after cooling;

[0096] Step S9: Determine whether the absolute value of the temperature difference between the current temperature and the second target temperature is within the second difference range. If not, control the second oil pump to keep it on and continue cooling before returning to step S8. If yes, execute step S10, where the second target temperature is the temperature to be reached after cooling.

[0097] Step S10: Control the second oil pump to shut down;

[0098] Step S11: End cooling.

[0099] Specifically, the control model is integrated into the controller. The heat flux density can be estimated by the current of the heater, thereby estimating the heating time to the target temperature. The heat flux density indirectly reflects the heating status and condition of the heater. The heating status of the PTC heater is directly reflected by the current I and voltage U. In this invention, the voltage U is generally a fixed value, but in practice, it depends on the working requirements. The current I can be measured by instruments or the controller's measurement function to determine its current value. At this time, the heating power of the heater P=UI. The heat flux density is estimated using the following formula: ,in Φ Heat flow, in W. λ The thermal conductivity of the material (in this invention, the thermal conductivity of the oil bath medium) is expressed in W / (m*k). A The surface area of ​​the cavity in which the heater is placed. δ The distance from the heater placement cavity to the outer surface of the heating unit block. The temperature difference between the heater placement cavity and the outer surface of the heating platform can be used to estimate the heat flow rate of the heater during heating using the above formula. The heat flux density q is the heat flow rate through a unit area per unit time. Therefore... q=Φ / AThe heat flux density can be obtained, which indirectly reflects the current thermodynamic state of the heater. The ambient temperature and the actual temperature are measured by the second temperature sensor. After measuring the temperature of the cover plate, the second temperature sensor transmits the measurement to the controller. The controller then estimates the heating time required to heat to the target temperature and controls the heating module array to heat according to the initial control model and the predicted heating time. After heating, the heating power of the heating unit is adjusted according to the actual temperature of the cover plate (the heating power can be adjusted by changing the current of the heater), thereby adjusting the heat flux density. Specifically, the first difference range and the second difference range can be 5°C, but in actual production, the first difference range and the second difference range can be adjusted according to actual production needs. It is worth noting that in step S6, heating is performed according to the set heating time, and the object being heated is the target substrate in the mass transfer. After the temperature adjustment is completed, the controller controls the heating module array to heat the target substrate in the mass transfer according to the set heating time. After the heating is completed, the controller controls the heating module array to stop heating and controls the second oil pump to start cooling. When the absolute value of the temperature difference between the current temperature and the second target temperature is within the second difference range, the controller controls the second oil pump to turn off and end the cooling.

[0100] The temperature control method described above can control the heating and cooling process of the heating platform in real time according to the temperature of the heating platform, effectively improving the efficiency of heating and cooling.

[0101] Furthermore, in this invention, due to the laws of heat transfer, the temperature in the middle of the heating module array is high, while the temperature at the periphery is low. Therefore, the real-time temperature of each heating unit block can be measured by each of the first temperature sensors, thereby controlling the heating power of each heating unit block through the controller. For example, the controller controls the heating power of the heater in the heating unit block located in the middle to decrease, and controls the heating power of the heater in the heating unit blocks located on the periphery to increase, thereby ensuring the overall temperature uniformity of the heating module array.

[0102] like Figure 11 As shown, further explanation is provided, the method also includes a step of optimizing the control model, which includes:

[0103] Step A1: Initialize the heat flux density, heating time, and model parameters of the control model;

[0104] Step A2: Control the execution of steps S1 to S10;

[0105] Step A3: Determine if it is the optimal solution. If yes, end the process; otherwise, proceed to step A4.

[0106] Step A4: Calculate and sort the fitness of individual solutions;

[0107] Step A5: Perform selection, crossover, and mutation operations sequentially to obtain new values ​​for the model parameters of the control model;

[0108] Step A6: Substitute the new values ​​into the numerical population and the model parameters of the control model, then proceed to step A2.

[0109] In addition to integrating the control model, the controller also incorporates a permutation-based genetic algorithm. The primary purpose of this algorithm is to iteratively optimize the feedforward-feedback integrated control, ensuring that any heater in the heating module array can reach the same temperature at different locations. The algorithm iterates and modifies certain parameters in the control model to allow heaters at different locations to reach the same temperature in the shortest possible time, minimizing temperature gradients. The genetic algorithm flowchart is shown below. Figure 11 As shown, the specific parameters of the model refer to some coefficients in the predictive mathematical models of the control model and control flow. The genetic algorithm includes sorting, selection, crossover, and mutation operations. Sorting by fitness in this invention refers to substituting the new values ​​obtained in A5 into the control model to obtain results such as heating time, which can represent heating efficiency. Then, the heating time is used for sorting; in terms of time, shorter heating times are better, as shorter heating times also indicate higher fitness of the new values ​​changed by the genetic algorithm. In the genetic algorithm, parameter mutation is within a certain range. The "selection operation" refers to selecting new values ​​within the range of higher fitness after sorting by fitness. The "crossover operation" refers to exchanging common parts between two control models of the same type but different data, thereby changing the coefficients in the control model. The "mutation operation" mimics the errors that may occur during DNA exchange in real-world genetics, leading to changes in values, further altering the coefficients in the control model. After the above steps, the model parameters of the new control model and the new control model can be obtained. The flowchart of combining feedforward feedback integrated control and the permutation-based genetic algorithm is shown below. Figure 12 As shown.

[0110] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A modular heating stage with high temperature uniformity, characterized in that, Includes a heating platform, a first oil pump, a second oil pump, and a controller; The heating stage includes a heating module array, a heating box, and a cover plate covering the heating box. The upper surface of the cover plate is used to place the target substrate. The heating box is provided with an oil bath cavity, which is filled with an oil bath medium. The heating module array is located inside the oil bath cavity and is immersed in the oil bath medium. The heating module array is composed of multiple heating unit blocks. The heating unit blocks are made of porous material. Each heating unit block has a heater placement cavity and a temperature sensor placement cavity. A heater is installed in the heater placement cavity, and a first temperature sensor is installed in the temperature sensor placement cavity. The heating module array is used to heat the heating stage. A second temperature sensor is provided on the surface of the cover plate. The input end of the first oil pump is connected to a cold oil source, and the output end of the first oil pump is connected to the cold oil input end of the heating box. The first oil pump is used to input cooled oil bath medium into the oil bath cavity. The input end of the second oil pump is connected to the hot oil output end of the heating box. The second oil pump is used to discharge the heated oil bath medium out of the oil bath cavity. The signal output terminals of the first temperature sensor and the second temperature sensor are respectively connected to the signal input terminal of the controller, and the heater, the first oil pump and the second oil pump are respectively connected to the controller.

2. The modular heating stage with high temperature uniformity according to claim 1, characterized in that, The heating unit block is in the shape of a hexagonal prism, and each of the six sides of the heating unit block is provided with a first insert structure. Multiple heating unit blocks are spliced ​​together through the first insert structure to form the heating module array.

3. The modular heating stage with high temperature uniformity according to claim 2, characterized in that, The first insert structure is a recessed groove facing the inner side of the heating unit block, or the first insert structure is a protruding block facing the outer side of the heating unit block, and the block cooperates with the groove.

4. The modular heating stage with high temperature uniformity according to claim 2, characterized in that, The inner wall of the heating box is provided with a second insert structure, which cooperates with the first insert structure. The heating module array is engaged with the second insert structure through the first insert structure.

5. The modular heating stage with high temperature uniformity according to claim 1, characterized in that, A flexible material layer is provided between the heating module array and the cover plate, and a heat insulation material layer is provided on the outside of the heating box.

6. The modular heating stage with high temperature uniformity according to claim 1, characterized in that, It also includes an oil cooling device, the output end of the second oil pump is connected to the input end of the oil cooling device, and the output end of the oil cooling device is connected to a cold oil recovery container.

7. The modular heating stage with high temperature uniformity according to claim 1, characterized in that, The cover plate is made of solid ceramic plate, and the heating box body is made of solid metal plate.

8. The modular heating stage with high temperature uniformity according to claim 1, characterized in that, The heating unit block is made of metal or alloy and refractory metal carbides, nitrides, borides and silicides, and the oil bath medium is any one of methyl silicone oil, soybean oil, cottonseed oil and heat transfer oil.

9. A temperature control method, applied to a modular heating stage with high temperature uniformity as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step S1: Obtain the initial heat flux density and ambient temperature, wherein the ambient temperature is the surface temperature of the cover plate; Step S2: Predict the heating time required to reach the first target temperature, where the first target temperature is the temperature that the cover plate needs to reach after heating. Step S3: Control the heating module array to heat according to the initial control model and the predicted heating time. The control model is a feedforward feedback integrated control. Step S4: Obtain the actual temperature of the cover plate after heating; Step S5: Determine whether the absolute value of the temperature difference between the actual temperature and the first target temperature is within the first difference range. If not, adjust the heating power of the heating unit block, continue to heat up, and return to step S4. If yes, execute step S6. Step S6: Control the heating module array to heat according to the set heating time; Step S7: Control the heating module array to stop heating and control the second oil pump to start; Step S8: Obtain the current temperature of the cover plate after cooling; Step S9: Determine whether the absolute value of the temperature difference between the current temperature and the second target temperature is within the second difference range. If not, control the second oil pump to keep it on and continue cooling before returning to step S8. If yes, execute step S10, where the second target temperature is the temperature to be reached after cooling. Step S10: Control the second oil pump to shut down; Step S11: End cooling.

10. The temperature control method according to claim 9, characterized in that, The method also includes a step of optimizing the control model, wherein the step of optimizing the control model includes: Step A1: Initialize the heat flux density, heating time, and model parameters of the control model; Step A2: Control the execution of steps S1 to S10; Step A3: Determine if it is the optimal solution. If yes, end the process; otherwise, proceed to step A4. Step A4: Calculate and sort the fitness of individual solutions; Step A5: Perform selection, crossover, and mutation operations sequentially to obtain new values ​​for the model parameters of the control model; Step A6: Substitute the new values ​​into the numerical population and the model parameters of the control model, then proceed to step A2.

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