A hot reflow device for microlens fabrication

Abstract

The application relates to the technical field of microlens preparation, and discloses a hot reflow device for microlens preparation, which comprises a box body, a wafer loading platform is detachably arranged at the upper end of the box body, an installation groove matched with a wafer is arranged on the wafer loading platform, a vacuum pipe in communication with the installation groove is arranged in the wafer loading platform, the other end of the vacuum pipe is used for connecting a negative pressure system, and a heating plate is arranged above the wafer loading platform in a lifting mode. The application can fix the relative position between the wafer and the heating plate, ensure the level of the wafer, avoid the wafer from being lifted and shaken during the separation process of the wafer and the heating plate, effectively control the hot reflow time of the wafer, and ensure the quality of the wafer.

Description

Technical Field

[0001] This invention relates to the field of microlens fabrication technology, and in particular to a hot reflux device for microlens fabrication. Background Technology

[0002] The microlens thermal melting method involves placing photoresist pillars, after photolithography and development, onto a heating plate. The pillars melt under heat, and due to surface tension and gravity, the molten photoresist forms spherical / aspherical curved microlenses. In inverted heating, the heating plate is on top and the wafer is below, requiring the wafer and heating plate to be fixed to a specific device. However, existing devices typically have the following structure: the heating plate is inverted (heated side down) on a support plate, and a liftable stage with compressible pins is placed below it. During production, the wafer to be heated is placed on the pins of the liftable stage, and then the stage carrying the product is moved under the preheated heating plate for heating. After a predetermined time, the stage is slowly lowered to separate the wafer from the heating plate, the heating plate is removed, heating stops, and the wafer is allowed to cool naturally to complete the thermal reflow process.

[0003] In actual use, the existing device was found to have the following drawbacks: When placing the wafer on the stage, because the wafer is directly supported on the pins, it is difficult to keep the relative position of the wafer consistent, resulting in an unstable relative position of the wafer to the hot plate. Furthermore, due to the uneven height of the pins, it is difficult to ensure that the wafer is level, affecting product quality. When the stage carrying the wafer descends, the wafer is lifted by the vacuum suction between it and the hot plate before falling. This process causes the wafer to vibrate. During the wafer cooling process, airflow may enter from the wafer side, affecting the final wafer shape. Because the wafer rises and falls, it needs to be done slowly to avoid the wafer falling, resulting in imprecise time control during the thermal reflow process, with an error of 5 to 10 seconds, affecting product quality. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a thermal reflow apparatus for microlens fabrication, which ensures that the relative position between the wafer and the heating plate is fixed, ensures the level of the wafer, avoids vibration caused by the wafer being lifted during the separation of the wafer and the heating plate, effectively controls the thermal reflow time of the wafer, and ensures the quality of the wafer.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A hot reflow apparatus for microlens fabrication includes a housing, a wafer stage detachably mounted on the upper end of the housing, a mounting groove adapted to the wafer on the wafer stage, a vacuum tube connected to the mounting groove inside the wafer stage, the other end of the vacuum tube being connected to a negative pressure system, and a heating plate retractably mounted directly above the wafer stage.

[0007] Preferably, the sidewall of the mounting groove includes a sidewall body and an anti-rotation sidewall, the anti-rotation sidewall corresponding to the tangent edge of the wafer.

[0008] Preferably, the wafer carrier is provided with a material pick-up slot, which is connected to the mounting slot.

[0009] Preferably, the upper end of the housing is open, the bottom wall of the mounting groove is provided with a through hole, the through hole is connected to the opening, and the side wall of the housing is provided with an air pressure balance hole.

[0010] Preferably, the bottom wall of the mounting groove is replaceably provided with a support pad, which is used to support the wafer.

[0011] Preferably, it includes a lifting cylinder, the cylinder barrel of which is fixed to the housing, and the telescopic rod of which is connected to the heating plate.

[0012] Preferably, the lifting cylinder is connected to an air pipe, and the air pipe is equipped with a solenoid valve.

[0013] Preferably, the upper surface of the wafer stage is covered with a heat insulation layer.

[0014] Preferably, the box body includes a frame, and the side of the frame is provided with side panels, wherein at least one side panel is openable and closable.

[0015] Preferably, the wafer carrier is provided with horizontal bubbles.

[0016] The heating device for hot reflow process according to an embodiment of the present invention has the following advantages compared with the prior art: by detachably setting a wafer stage at the upper end of the housing, and setting a mounting slot adapted to the wafer on the wafer stage, the appropriate wafer stage can be selected according to the size of the wafer first, and the wafer stage can be set on the housing. Then the wafer is placed in the mounting slot, thereby realizing the full enclosure mounting of the wafer. This not only ensures that the relative position between the wafer and the heating plate is fixed, but also ensures that the wafer is level when supported in the mounting slot. At the same time, it avoids the wafer being disturbed by airflow during the cooling process, thus ensuring the final surface shape of the wafer.

[0017] In addition, by setting a vacuum tube inside the wafer stage that is connected to the mounting slot, and the other end of the vacuum tube is used to connect to the negative pressure system, the wafer can be adsorbed by negative pressure. This allows the wafer to be completely adsorbed in the mounting slot during the separation process from the heating plate, avoiding vibration caused by being lifted during the separation process and ensuring product quality.

[0018] Meanwhile, by raising and lowering the heating plate directly above the wafer stage, the wafer will not fall because the heating plate rises and falls. This allows for rapid bonding and separation between the heating plate and the wafer, effectively controlling the heat reflow time and ensuring the quality of the wafer products. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the thermal reflux apparatus for fabricating microlenses according to the present invention.

[0020] Figure 2 This is a cross-sectional view of the hot reflux apparatus for microlens fabrication according to the present invention.

[0021] Figure 3 This is a schematic diagram of the heating plate of the present invention.

[0022] Figure 4 This is a cross-sectional view of the plate body of the present invention.

[0023] Wherein: 1-box body, 11-air pressure balance hole, 12-support leg, 2-wafer stage, 21-mounting slot, 22-anti-rotation side wall, 23-material loading slot, 24-through hole, 3-vacuum tube, 4-heating plate, 41-plate body, 42-cooling system, 43-heating system, 44-temperature sensor, 45-heating tube, 46-cooling tube, 47-auxiliary heating device, 48-insulation layer, 5-support pad, 6-lifting cylinder, 7-insulation layer, 8-horizontal bubble, 9-controller, 100-wafer. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] like Figure 1-2As shown, a preferred embodiment of the present invention provides a hot reflow apparatus for microlens fabrication, comprising a housing 1. A wafer stage 2 is detachably mounted on the upper end of the housing 1. The wafer stage 2 has a mounting groove 21 adapted to a wafer 100. A vacuum tube 3, communicating with the mounting groove 21, is located inside the wafer stage 2. The other end of the vacuum tube 3 is connected to a negative pressure system. A heating plate 4 is vertically detachable above the wafer stage 2. Specifically, the hot reflow apparatus for microlens fabrication further includes a lifting cylinder 6. The cylinder barrel of the lifting cylinder 6 is fixed to the outer wall of the housing 1. The extension rod of the lifting cylinder 6 is connected to the heating plate 4, enabling the lifting and lowering of the heating plate 4. For ease of control, the lifting cylinder 6 is connected to an air pipe, and a solenoid valve is mounted on the air pipe. The opening and closing of the solenoid valve drives the lifting cylinder 6 to lift and lower the wafer stage 2.

[0026] Based on the aforementioned distinguishing technical features, the hot reflow apparatus for microlens fabrication detachably sets a wafer stage 2 at the upper end of the housing 1, and sets a mounting groove 21 on the wafer stage 2 that is compatible with the wafer 100. Thus, the appropriate wafer stage 2 can be selected according to the size of the wafer 100 and set on the housing 1. Then, the wafer 100 is placed in the mounting groove 21, thereby achieving full enclosure mounting of the wafer 100. This not only ensures that the relative position between the wafer 100 and the heating plate 4 is fixed, but also ensures that the wafer 100 is level as it is supported in the mounting groove 21. At the same time, it avoids the wafer 100 being disturbed by airflow during the cooling process, thus ensuring the final surface shape of the wafer 100.

[0027] In addition, by setting a vacuum tube 3 inside the wafer stage 2 that is connected to the mounting groove 21, and the other end of the vacuum tube 3 is used to connect to the negative pressure system, the wafer 100 can be adsorbed by negative pressure, so that the wafer 100 is completely adsorbed in the mounting groove 21 during the separation process from the heating plate 4, avoiding the vibration caused by being lifted during the separation process from the heating plate 4, and ensuring the quality of the product.

[0028] Meanwhile, by raising and lowering the heating plate 4 directly above the wafer stage 2, the wafer 100 will not fall because the heating plate 4 rises and falls. This allows for rapid bonding and separation between the heating plate 4 and the wafer 100, effectively controlling the heat reflow time and ensuring the quality of the wafer 100 product.

[0029] In this embodiment, the sidewall of the mounting slot 21 includes a sidewall body and an anti-rotation sidewall 22. The anti-rotation sidewall 22 corresponds to the diced edge of the wafer 100. During installation, the wafer 100 is placed into the mounting slot 21 with the diced edge corresponding to the anti-rotation sidewall 22, which can prevent the wafer 100 from rotating within the mounting slot 21, thereby ensuring the effect of thermal reflow. In addition, to facilitate the removal of the cooled wafer 100 from the mounting slot 21, the wafer stage 2 is provided with a pick-up slot 23. The pick-up slot 23 is connected to the mounting slot 21. When it is necessary to remove the wafer 100, it can be removed by inserting it into the pick-up slot 23.

[0030] In this embodiment, the upper end of the housing 1 is open, and the bottom wall of the mounting groove 21 is provided with a through hole 24, which communicates with the opening. The side wall of the housing 1 is provided with a pressure balancing hole 11. Since the product surface of the wafer 100 contains devices, the through hole provided on the bottom wall of the mounting groove 21 allows the devices to be directly accommodated in the through hole, avoiding the devices being supported by the bottom wall of the mounting groove 21, thereby ensuring the quality of the wafer 100. In the tooling state, the housing 1, the wafer stage 2, and the wafer 100 form a sealed space. The product surface of the wafer 100 is located inside the sealed space, protecting the products on the wafer 100 from the influence of airflow during heating and cooling. At the same time, the pressure balancing hole 11 can balance the pressure changes caused by heating inside the housing 1 during heat reflow.

[0031] In this embodiment, the bottom wall of the mounting groove 21 is replaceably provided with a support pad 5, which is used to support the wafer 100. The support pad 5 can be made of compressible silicone, and its thickness can be replaced. By reducing the thickness of the compressible silicone, the conversion from contact heating to non-contact heating can be achieved. Generally, the wafer 100 adopts a contact heating method, that is, the heating plate 4, the wafer stage 2, the wafer 100, and the compressible silicone are interference-fitted. The heating plate 4 is supported by the wafer stage 2 to prevent the weight of the heating plate 4 from crushing the wafer 100. The wafer 100 is in close contact with the heating plate 4 by the support of the compressible silicone (that is, at this time, the upper surface of the support pad 5 is higher than the upper surface of the mounting groove 21 in the normal state. When the heating plate 4 is lowered, the upper surface of the support pad 5 is flush with the upper surface of the mounting groove 21). In some cases, non-contact heating can be used, in which case the wafer 100 and the heating plate 4 do not contact each other (that is, in this case, the upper surface of the support pad 5 is lower than the upper surface of the mounting groove 21 under normal conditions).

[0032] In this embodiment, the housing 1 includes a frame with side panels on its sides, at least one of which is openable and closable, facilitating routine cleaning and maintenance of the housing 1's interior. Simultaneously, adjustable support feet 12 are installed at the bottom of the housing 1, and a horizontal bubble 8 is provided on the wafer stage 2. Adjusting the support feet 12 in conjunction with the horizontal bubble 8 on the wafer stage 2 allows for determination of whether the thermal reflow device is level. Furthermore, a heat insulation layer 7 is laid on the upper surface of the wafer stage 2 to prevent the heating plate 4 from heating areas of the wafer stage 2 outside the mounting slot 21.

[0033] In this embodiment, the heating plate 4 includes a plate body 41, a cooling system 42, and a heating system 43. The plate body 41 is made of a high thermal conductivity material, such as graphene, metal, or a high thermal conductivity ceramic material, and its surface needs to have good flatness, requiring a flatness of less than 0.01 mm. The plate body 41 is internally equipped with a temperature sensor 44, a heating tube 45, and a cooling tube 46. The heating tube 45 is circulatedly connected to the heating system 43, and the cooling tube 46 is circulatedly connected to the cooling system 42. Both the heating system 43 and the cooling system 42 are electrically connected to the temperature sensor 44. The heating system 43 mainly heats the heating medium through a heating element and then uses a circulating pump to transport the heated medium to the heating tube 45 for further heating. The cooling system 42 is mainly a cooling tank, which uses a circulating pump to transport the cooling medium to the cooling tube 46. The heating and cooling media can be oil, high-pressure water, or high-pressure steam. The maximum temperature of the heating / cooling media can reach 400℃.

[0034] The heating plate 4 has a temperature sensor 44, a heating tube 45, and a cooling tube 46 installed inside the plate body 41. The heating tube 45 is circulatedly connected to the heating system 43, and the cooling tube 46 is circulatedly connected to the cooling system 42. Both the heating system 43 and the cooling system 42 are electrically connected to the temperature sensor 44. Thus, the temperature of the plate body 41 can be detected in real time by the temperature sensor 44 and compared with the set temperature. When the set temperature is higher than the detected temperature, the cooling system 42 is activated. When the set temperature is lower than the detected temperature, the heating system 43 is activated. When the set temperature is equal to the detected temperature, the current heating and cooling system is maintained. This can effectively control the heating and cooling process during the reflow process, avoid stress generated during the cooling process, prevent the dome from sinking, and ensure that the profile deviation of the rubber ball is qualified after cooling.

[0035] In this embodiment, the temperature sensor 44 is located on the upper part of the plate 41, the heating pipe 45 and the cooling pipe 46 are located on the lower part of the plate 41, and an auxiliary heating device 47 is also provided in the middle of the plate 41, that is, the auxiliary heating device 47 is located between the temperature sensor 44 and the heating pipe 45. The auxiliary heating device 47 is electrically connected to the temperature sensor 44. The auxiliary heating device 47 can adopt an electric heating method or an electromagnetic heating method. In cooperation with the temperature sensor 44, it is used to rapidly heat up the plate in the initial stage of heating, and to achieve precise temperature control of the plate 41 in the subsequent heat reflow process.

[0036] Meanwhile, to ensure precise control, the heat reflow device for microlens fabrication also includes a controller 9. The temperature sensor 44, the solenoid valve, and the auxiliary heating device 47 are all electrically connected to the controller 9. The controller 9 can adjust the flow rate of the heating / cooling medium and the opening and closing of the auxiliary heating device 47 in real time to achieve precise control of the temperature of the heating plate 4. The temperature control accuracy can reach ±0.1℃. The control part can control the temperature change curve by inputting multiple temperature segments (maximum input segments of more than 20 segments). The controller 9 can also control the opening and closing of the solenoid valve, thereby controlling the lifting cylinder 6 to ensure the heat reflow time.

[0037] In addition, to further ensure control accuracy, the temperature measured by the temperature sensor 44 must be accurate, and multiple sensors can be installed within the plate 41. Specifically, the plate 41 has a rectangular cross-section, and five temperature sensors 44 are respectively located at the four corners and the center of the plate 41. The temperature of the plate 41 can be detected in real time and compared with the set temperature (curve), enabling independent control of the heating and cooling curves. Adjustments can be made according to process parameters to eliminate stress generated during the cooling of the rubber balls in the hot reflow process, preventing ball top depression and minimizing the surface deviation (SPD) of the rubber balls.

[0038] In this embodiment, the bottom of the plate 41 is provided with a heat insulation layer 48, which can not only effectively maintain the temperature of the plate 41 and reduce its heat loss, but also avoid the influence of the ambient temperature on the plate 41.

[0039] In this embodiment, to ensure the heating effect of the heating tube 45 on the plate 41, the heating tube 45 is U-shaped, serpentine, or wavy, thereby providing a larger contact area between the heating tube 45 and the plate 41, improving the heating speed and uniformity. Similarly, the cooling tube 46 is also U-shaped, serpentine, or wavy.

[0040] This application adds a temperature control system to the plate 41, avoiding the shortcoming of traditional heating plates 4 which cannot control the cooling curve (cooling rate, cooling time). This application can control the heating curve and cooling curve independently, and can be adjusted according to process parameters to eliminate the stress generated during the cooling of the rubber balls in the hot reflow process, so as to prevent the ball top from sinking and to make the ball profile deviation (SPD) smaller. This application can also automatically set the heating, cooling and heat preservation, which can be set before hot reflow and automatically controlled during hot reflow.

[0041] The working process of the hot reflux device for microlens fabrication is as follows:

[0042] Step 1: Adjust the wafer stage 2 to a horizontal position by adjusting the support foot 12;

[0043] Step 2: Preheat heating plate 4, set the temperature of heating plate 4 to the working temperature, and wait for the temperature of heating plate 4 to reach the working temperature;

[0044] Step 3: Place wafer 100 in the mounting slot 21 of wafer stage 2 and adjust wafer 100 to the designated position;

[0045] Step 4: Input the required heating and cooling time, turn on the device switch, the extension rod of the lifting cylinder 6 descends, the heating plate 4 contacts the wafer 100, and the device automatically starts timing;

[0046] Step 5: When the set heating time is reached, the lifting cylinder 6 automatically rises to separate the heating plate 4 from the wafer 100; the cooling time begins to be counted; during the separation process, the negative pressure system connected to the vacuum tube 3 works to prevent the wafer 100 from shaking during the separation process from the heating plate 4; when the separation is completed, the negative pressure system stops working.

[0047] Step 6: When the cooling time is reached, the device will alarm and remove wafer 100 and place it in the designated location;

[0048] Step 7: After the work is completed, the device is powered off and gas is shut off to complete the heat reflux operation.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A hot reflux apparatus for microlens fabrication, characterized in that: The device includes a housing and a lifting cylinder. The upper end of the housing is detachably equipped with a wafer stage. The side wall of the housing is equipped with a pressure balancing hole. The wafer stage is equipped with a mounting slot adapted to the wafer. The interior of the wafer stage is equipped with a vacuum tube that communicates with the mounting slot. The other end of the vacuum tube is used to connect to a negative pressure system. A heating plate is detachably mounted on the top of the wafer stage. The cylinder of the lifting cylinder is fixed to the housing, and the extension rod of the lifting cylinder is connected to the heating plate.

2. The hot reflux apparatus for microlens fabrication as described in claim 1, characterized in that: The sidewall of the mounting groove includes a sidewall body and an anti-rotation sidewall, the anti-rotation sidewall corresponding to the tangent edge of the wafer.

3. The hot reflux apparatus for microlens fabrication as described in claim 1, characterized in that: The wafer carrier is provided with a material pick-up slot, which is connected to the mounting slot.

4. The hot reflux apparatus for microlens fabrication as described in claim 1, characterized in that: The upper end of the housing is open, and the bottom wall of the mounting groove is provided with a through hole, which is connected to the opening.

5. The hot reflux apparatus for microlens fabrication as described in claim 1, characterized in that: The bottom wall of the mounting slot is replaceably provided with a support pad, which is used to support the wafer.

6. The hot reflux apparatus for microlens fabrication as described in claim 1, characterized in that: The lifting cylinder is connected to an air pipe, and an electromagnetic valve is installed on the air pipe.

7. The hot reflux apparatus for microlens fabrication as described in any one of claims 1-5, characterized in that: The upper surface of the wafer stage is covered with a heat insulation layer.

8. The hot reflux apparatus for microlens fabrication as described in any one of claims 1-5, characterized in that: The box includes a frame, and the frame has side panels on its sides, wherein at least one side panel is openable and closable.

9. The hot reflux apparatus for microlens fabrication as described in any one of claims 1-5, characterized in that: The wafer carrier is provided with horizontal bubbles.

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