An ultra-high vacuum eutectic furnace for optoelectronic chip packaging

Abstract

This utility model relates to the field of vacuum engineering, and more specifically to an ultra-high vacuum eutectic furnace for optoelectronic chip packaging. It includes: a heating furnace body with a vacuum chamber; a vacuum system, a two-stage vacuum unit consisting of a forestage mechanical pump and a main pump, used to provide an ultra-high vacuum environment for the vacuum chamber; a heating system disposed within the vacuum chamber, the heating system including a multi-layer assembled heating plate, the multi-layer assembled heating plate integrating heating tubes, cooling pipes, and a workstation positioning structure, the heating tubes and cooling pipes being embedded inside the multi-layer assembled heating plate; a heat insulation device, a multi-layer reflective heat insulation structure surrounding the heating system, the reflective heat insulation structure including a reflective layer facing the multi-layer assembled heating plate and an external water-cooled plate; and a reducing atmosphere supply unit connected to the vacuum chamber via multiple gas pipelines. This application achieves efficient, safe, and intelligent chip packaging under high vacuum conditions.

Description

Technical Field

[0001] This utility model relates to the field of vacuum engineering, and more specifically to an ultra-high vacuum eutectic furnace for optoelectronic chip packaging. Background Technology

[0002] In traditional optoelectronic chip packaging processes, conventional eutectic furnaces, due to insufficient vacuum (generally only reaching the level of 10^-2 Pa), cannot meet the ultra-high vacuum environment requirements of high-end chips (above 10^-4 Pa), resulting in high solder void rates and limited yield. Furthermore, traditional equipment uses a single heating plate structure, which has low heat conduction efficiency in high vacuum environments, slow heating and cooling rates, and poor heating uniformity, severely impacting packaging efficiency. Weak thermal insulation design leads to excessively high furnace shell temperatures, posing safety hazards. Complex valve controls and dispersed operating interfaces further increase operational difficulty and maintenance costs. These shortcomings severely restrict the large-scale industrial production of high-precision optoelectronic chips. Utility Model Content

[0003] The purpose of this invention is to provide an ultra-high vacuum eutectic furnace for optoelectronic chip packaging, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the following technical solution is adopted.

[0005] An ultra-high vacuum eutectic furnace for optoelectronic chip packaging includes:

[0006] The heating furnace body is equipped with a vacuum chamber;

[0007] The vacuum system is a two-stage vacuum unit consisting of a backing mechanical pump and a main pumping molecular pump, used to provide an ultra-high vacuum environment for the vacuum chamber;

[0008] A heating system is provided in the vacuum cavity. The heating system includes a multi-layer assembled heating plate. The multi-layer assembled heating plate integrates heating tubes, cooling pipes and a workstation positioning structure. The heating tubes and the cooling pipes are embedded inside the multi-layer assembled heating plate.

[0009] A heat insulation device, comprising a multi-layer reflective heat insulation structure surrounding the heating system, the reflective heat insulation structure including a reflective layer facing the multi-layer assembled heating plate and an external water-cooling plate;

[0010] The reducing atmosphere supply unit is connected to the vacuum chamber via multiple gas pipelines.

[0011] Optionally, the two-stage vacuum unit includes a forepump mechanical pump, a main pump molecular pump, and a valve assembly; the forepump mechanical pump is connected to the vacuum chamber via a first pipeline; the exhaust end of the main pump molecular pump is connected to the forepump mechanical pump via a second pipeline, and the pumping end of the main pump molecular pump is connected to the vacuum chamber; the valve assembly includes a pre-pump baffle valve disposed on the first pipeline, a forepump baffle valve disposed on the second pipeline, and a gate valve disposed between the pumping end of the main pump molecular pump and the vacuum chamber.

[0012] Optionally, the multi-layer assembled heating plate includes a lower heating plate and an upper heating plate for placing the workpiece, wherein the upper heating plate and the lower heating plate are mechanically connected and their end faces are tightly fitted.

[0013] The lower heating plate has a mounting cavity for the heating tube, the heating tube is embedded in the mounting cavity, and the mounting cavity completely covers the heating area of ​​the heating tube, so that the heat of the heating tube can be conducted to the upper heating plate through the lower heating plate.

[0014] The cooling pipe is embedded in the lower heating plate by slotting and is flush with the surface of the lower heating plate. The cooling pipe is used to quickly remove heat in a vacuum environment.

[0015] Optionally, the cooling pipe is a serpentine pipe and is connected to an external circulating cooling device.

[0016] Optionally, the surface of the upper heating plate is provided with a matrix-type workstation slot and distributed temperature sensors. The workstation slot is equipped with elastic positioning pins for quick fixation of the chip carrier and thermal expansion compensation.

[0017] Optionally, the reflective layer includes a first reflective heat insulation plate and a second heat insulation plate. The first reflective heat insulation plate is disposed on the upper cover of the heating furnace body and is made of mirror metal material, used to cover the outer surface of the heating system. The second heat insulation plate is disposed below the multi-layer assembled heating plate, is made of ceramic matrix composite material, and is spaced with the first reflective heat insulation plate to form an air insulation cavity.

[0018] The external water-cooled plate covers the outer wall of the vacuum chamber and forms a parallel heat dissipation network with the cooling pipes of the lower heating plate through a circulating water channel.

[0019] Optionally, the reducing atmosphere supply unit further includes:

[0020] The gas mixing chamber is connected to a nitrogen source, a hydrogen source, and a formic acid source via a vacuum four-way valve.

[0021] The gas injection nozzles are located at the bottom of the vacuum chamber and are distributed in a ring array. The nozzle outlet direction is inclined at an angle to the plane of the multi-layer assembled heating plate to enhance the uniformity of airflow.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention proposes an ultra-high vacuum eutectic furnace for optoelectronic chip packaging. This eutectic furnace employs a two-stage vacuum system, providing an ultra-high vacuum environment and effectively solving the problems of low vacuum levels, high solder void rates, and low packaging efficiency in existing technologies. Specifically, the eutectic furnace of this invention includes a heating furnace body, a vacuum system, a heating system, a heat insulation device, and a reducing atmosphere supply unit. The vacuum system consists of a two-stage vacuum unit composed of a forestage mechanical pump and a main pump molecular pump, which can raise the vacuum level within the vacuum chamber to the 10^-7 Pa level, significantly reducing the solder void rate and improving product yield and quality. The heating system uses a multi-layer assembled heating plate, integrating heating tubes, cooling pipes, and a workstation positioning structure, achieving efficient heat conduction and uniform temperature field distribution, while improving packaging efficiency and quality. Furthermore, the multi-layer reflective heat insulation structure and external water-cooled plate design of the heat insulation device effectively reduce heat loss, lower energy consumption, and improve the safety and stability of the equipment. The reducing atmosphere supply unit is connected to the vacuum chamber through multiple gas pipelines, providing a reducing atmosphere during the packaging process, further improving soldering quality. In summary, the ultra-high vacuum eutectic furnace of this invention has significant beneficial effects in improving vacuum level, reducing welding void rate, and improving packaging efficiency and quality, providing an advanced technical solution for the field of optoelectronic chip packaging. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of an embodiment of an ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to this utility model.

[0025] Figure 2 This is a schematic diagram of the overall structure of an ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to another perspective of this utility model.

[0026] Figure 3 This is a schematic diagram of the overall structure of the heating system of an ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram showing the disassembled structure of the heating system of an ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to an embodiment of this utility model.

[0028] Explanation of reference numerals in the attached drawings: 1. Heating furnace body; 2. Upper heating plate; 3. Top cover; 4. External water-cooled plate; 5. Control panel; 6. Human-machine interface; 7. First layer of reflective heat insulation plate; 8. Main pump molecular pump; 9. Fore-stage mechanical pump; 10. Vacuum monitoring module; 11. Heat insulation device; 12. Mass flow controller; 13. Multi-channel gas pipeline; 14. PLC controller; 15. Temperature monitoring module; 16. Heating tube; 17. Lower heating plate; 18. First heat insulation plate; 19. Second heat insulation plate; 20. Ceramic insulation layer; 21. Copper pipe. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0030] The following detailed description is exemplary and intended to provide further detailed explanation of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention.

[0031] like Figures 1-4 As shown, the ultra-high vacuum eutectic furnace of this invention is a high-end device specifically designed for the packaging of optoelectronic chips. Its design aims to solve the problems of low vacuum, low heating efficiency, poor heat dissipation performance and complex operation in the existing technology.

[0032] The vacuum system of the eutectic furnace consists of a two-stage vacuum unit comprising a backing mechanical pump 9 and a main pumping molecular pump 8. The backing mechanical pump 9 is a rotary vane oil pump, capable of rapidly pumping air at a lower vacuum level, quickly reducing the pressure inside the vacuum chamber from atmospheric pressure to approximately 10. -2 Pa. Subsequently, the main pump molecular pump 8 was activated, further increasing the vacuum level to 10. -7 Pa level. This two-stage vacuum system design effectively solves the problems of low vacuum level, high leakage rate, and low vacuuming efficiency in existing technologies. Through optimized valve and sealing components, the system can stably achieve ultra-high vacuum levels, significantly reducing the void rate in eutectic welding and improving product yield and quality.

[0033] In practical implementation, the fore-stage mechanical pump 9 is connected to the vacuum chamber via a first pipeline, and the exhaust end of the main pump molecular pump 8 is connected to the fore-stage mechanical pump 9 via a second pipeline. The pumping end of the main pump molecular pump 8 is also connected to the vacuum chamber. The valve assembly includes a pre-pump baffle valve on the first pipeline, a fore-stage baffle valve on the second pipeline, and a gate valve between the pumping end of the main pump and the vacuum chamber. This not only improves the system's flexibility and reliability but also reduces the complexity of the pipeline connections.

[0034] The heating system employs a multi-layer assembled heating plate, integrating heating elements, cooling pipes, and a workstation positioning structure. The lower heating plate 17 has an embedded serpentine cooling pipe connected to an external circulating cooling device for rapid cooling. The cooling pipe can be serpentine or made of copper tubing 21. The upper heating plate 2 has a matrix-style workstation slot and distributed temperature sensors on its surface. The workstation slot uses elastic positioning pins to quickly fix the chip carrier and compensate for thermal expansion. This design not only improves heating efficiency but also optimizes heat dissipation, significantly reducing the solder void rate and improving soldering quality.

[0035] The heating element is a heating tube 16, embedded inside the heating plate, and zoned temperature control is achieved through a branch control module. Each group of heating elements is connected to a programmable solid-state relay, and the current in each circuit is monitored by a Hall current sensor. The relay cuts off the corresponding branch when a short circuit or over-limit is detected. This ensures the safety and reliability of the heating system and prevents damage to the entire system due to localized faults. Ceramic insulation layers 20 are provided on both sides of the heating element.

[0036] The heat insulation device 11 surrounds the heating system and includes a multi-layer reflective heat insulation structure. The first layer of reflective heat insulation plate 7 is made of mirrored metal material and covers the outer surface of the heating system, effectively reflecting heat and reducing heat loss to the outside of the furnace. The second layer of heat insulation plate includes a first heat insulation plate 18 and a second heat insulation plate 19, which are stacked and made of ceramic matrix composite material. They are spaced apart from the first layer of reflective heat insulation plate 7 to form an air insulation cavity, further enhancing the heat insulation effect. The external water-cooled plate 4 covers the outer wall of the vacuum chamber and forms a parallel heat dissipation network with the cooling pipes of the lower heating plate 17 through a circulating water channel. This design not only improves heat dissipation efficiency but also makes the temperature distribution of the entire furnace more uniform, providing a stable environment for the encapsulation process.

[0037] The reducing atmosphere supply unit is connected to the vacuum chamber via multiple gas pipelines 13 and is equipped with a mass flow controller 12 for the selective mixing and precise injection of nitrogen, hydrogen, and formic acid gases. The gas mixing chamber is connected to the nitrogen, hydrogen, and formic acid sources via vacuum four-way valves, and the mass flow controller 12 dynamically adjusts the mixed gas ratio according to a preset process curve. The gas injection nozzles are located at the bottom of the vacuum chamber and arranged in a ring array. The nozzle outlet direction is inclined at an angle to the heating plate plane to enhance airflow uniformity. This design provides a reducing atmosphere during the encapsulation process, reducing the oxide film on the workpiece surface, improving solder wettability, and further reducing the solder void rate.

[0038] The control system includes a control panel 5, a PLC controller 14, and a human-machine interface 6. The PLC controller 14 synchronously controls the power of the vacuum system and heating system, gas flow rate, and temperature monitoring module 15 through an integrated communication module. The human-machine interface 6 provides process parameter setting, real-time status display, and manual operation functions, enabling operators to conveniently perform process control and equipment monitoring.

[0039] The control system further includes an adaptive temperature control module and a vacuum level linkage module. The adaptive temperature control module adjusts the heating element power in real time based on feedback signals from distributed temperature sensors and eliminates regional temperature differences through a PID algorithm. The vacuum level linkage module automatically triggers the main pump molecular pump 8 speed-up mode when it detects that the vacuum level is lower than a set threshold, and simultaneously reduces the heating system power to maintain thermal balance. This linkage mechanism can effectively cope with vacuum level fluctuations that may occur during the packaging process, ensuring the stability of the packaging process.

[0040] The human-machine interface 6 further includes a process recipe storage module, a fault diagnosis unit, and a data logging module. The process recipe storage module supports the rapid recall and modification of multiple sets of preset process parameters, allowing operators to quickly switch process parameters according to different packaging requirements. The fault diagnosis unit identifies vacuum leaks, heating anomalies, or gas flow deviations through feature codes and generates visual alarm prompts and handling suggestions. The data logging module automatically saves the temperature, vacuum, and gas flow rate change curves throughout the entire process cycle, providing data support for process optimization and quality traceability.

[0041] The vacuum chamber features a top cover (3) with a double-ring metal seal on the sealing surface, working in conjunction with a quick-release locking mechanism. This design not only improves sealing performance but also facilitates opening and closing of the top cover, enhancing operational efficiency. A knife-edge flange interface connects to the molecular pump and gas pipeline, utilizing an oxygen-free copper gasket sealing structure. This further strengthens the sealing of the connection points, ensuring reliability under high vacuum conditions. The inner wall of the chamber is polished and coated with an anti-oxidation coating consisting of alternating layers of titanium nitride and diamond-like carbon. This coating structure not only improves the chamber's oxidation resistance but also reduces the impact of impurities on the encapsulation process, extending the equipment's lifespan.

[0042] Specific steps of optoelectronic chip packaging method

[0043] The specific steps of the optoelectronic chip packaging method using the above-mentioned ultra-high vacuum eutectic furnace are as follows:

[0044] Chip carrier fixation and vacuum chamber closure: First, the chip carrier is fixed in the heating plate station slot to ensure the stability of the chip during the packaging process. Then, the vacuum chamber is closed, and a reliable seal is achieved through the top cover 3 and the quick-release locking mechanism.

[0045] Start the two-stage vacuum system: Start the two-stage vacuum system consisting of the forestage mechanical pump 9 and the main pumping molecular pump 8 to reduce the chamber pressure to the preset pressure. During the vacuuming process, the PLC controller 14 automatically adjusts the operating status of the forestage mechanical pump 9 and the main pumping molecular pump 8 according to the real-time data of the vacuum monitoring module 10 to ensure that the vacuum level can be quickly and stably reached the set value.

[0046] A reducing atmosphere is introduced: a nitrogen-hydrogen mixture is introduced through a reducing atmosphere supply unit, and the gas flow rate is precisely controlled by a mass flow controller 12. The ratio of the mixed gas is dynamically adjusted according to a preset process curve to reduce the oxide layer on the workpiece surface. The reducing atmosphere can improve solder wettability, reduce solder void rate, and improve packaging quality.

[0047] Heating according to a preset temperature rise curve: Based on the preset temperature rise curve, the heating system starts heating, gradually increasing the temperature to the eutectic welding temperature and holding it at that temperature. During the heating process, the adaptive temperature control module adjusts the power of the heating element in real time based on feedback signals from distributed temperature sensors, and eliminates regional temperature differences through a PID algorithm to ensure temperature uniformity in all areas of the heating plate, meeting the process requirements of eutectic welding.

[0048] Rapid cooling is achieved by activating the cooling pipes: After the required holding time is reached, the serpentine cooling pipes within the lower heating plate 17 are activated, rapidly dissipating heat through an external circulating cooling device, causing the temperature to drop quickly. During the cooling process, the PLC controller 14 automatically adjusts the flow rate and velocity of the cooling water based on temperature monitoring data to ensure the cooling speed meets process requirements. Once the temperature drops to a safe threshold, the vacuum is broken and the packaged finished product is removed.

[0049] The heating element can be either a resistance wire or a silicon carbide heating element, depending on the required heating efficiency and temperature range. Resistance wire is suitable for medium temperature ranges, while silicon carbide heating elements are suitable for higher temperature environments.

[0050] Cooling pipes can be designed in spiral, serpentine, or other optimized paths to improve cooling efficiency. For example, spiral cooling pipes can increase the contact area between the coolant and the heating plate, thereby improving heat dissipation.

[0051] The workstation slots can be designed in various shapes to accommodate chip carriers of different sizes and shapes, improving the versatility of the equipment. For example, workstation slots can be designed in circular, square, or other custom shapes to meet the specific needs of different customers.

[0052] Reflective heat insulation panels can be made of different mirror-finish metal materials, such as stainless steel and aluminum. The specific choice depends on the reflection efficiency and cost. Stainless steel has good corrosion resistance and reflective properties, while aluminum has lighter weight and good reflective properties.

[0053] Insulation panels can be multi-layered, with each layer using different insulation materials, such as ceramic fiber and glass fiber, to further improve the insulation effect.

[0054] Gas mixing chambers can be designed in various configurations to achieve more precise gas mixing and flow control.

[0055] Nozzles can be designed in different distribution patterns, such as ring arrays or linear arrays, to achieve a more uniform gas distribution.

[0056] The PLC controller 14 can integrate more functional modules, such as fault prediction modules and remote monitoring modules, to improve the intelligence level of the equipment.

[0057] The human-computer interaction interface 6 can add more functions, such as remote operation and data export functions, to improve the ease of operation.

[0058] As is known from common technical knowledge, this utility model can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this utility model or its equivalents are included in this utility model.

Claims

1. An ultrahigh vacuum eutectic furnace for optoelectronic chip packaging, characterized by, include: The heating furnace body (1) is equipped with a vacuum chamber; The vacuum system is a two-stage vacuum unit consisting of a backing mechanical pump (9) and a main pumping molecular pump (8) to provide an ultra-high vacuum environment for the vacuum chamber. A heating system is provided in the vacuum cavity. The heating system includes a multi-layer assembled heating plate. The multi-layer assembled heating plate integrates a heating tube (16), a cooling pipe and a workstation positioning structure. The heating tube (16) and the cooling pipe are embedded inside the multi-layer assembled heating plate. The heat insulation device (11) is provided with a multi-layer reflective heat insulation structure around the heating system. The reflective heat insulation structure includes a reflective layer facing the multi-layer assembled heating plate and an external water-cooled plate (4). The reducing atmosphere supply unit is connected to the vacuum chamber via a multi-channel gas pipeline (13).

2. The ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to claim 1, characterized in that, The two-stage vacuum unit includes a fore-stage mechanical pump (9), a main pump molecular pump (8), and a valve assembly. The fore-stage mechanical pump (9) is connected to the vacuum chamber through a first pipeline. The exhaust end of the main pump molecular pump (8) is connected to the fore-stage mechanical pump (9) through a second pipeline, and the pumping end of the main pump molecular pump (8) is connected to the vacuum chamber. The valve assembly includes a pre-pump baffle valve disposed on the first pipeline, a fore-stage baffle valve disposed on the second pipeline, and a gate valve disposed between the pumping end of the main pump molecular pump (8) and the vacuum chamber.

3. The ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to claim 1, characterized in that, The multi-layer assembled heating plate includes a lower heating plate (17) and an upper heating plate (2) for placing workpieces. The upper heating plate (2) and the lower heating plate (17) are mechanically connected and their end faces are tightly fitted. The lower heating plate (17) is provided with a mounting cavity for a heating tube (16). The heating tube (16) is embedded in the mounting cavity, and the mounting cavity completely covers the heating area of ​​the heating tube (16) so that the heat of the heating tube (16) can be conducted to the upper heating plate (2) through the lower heating plate (17). The cooling pipe is embedded in the surface of the lower heating plate (17) through a groove and is flush with the surface of the lower heating plate (17). The cooling pipe is used to quickly remove heat in a vacuum environment.

4. The ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to claim 3, characterized in that, The cooling pipe is a serpentine pipe and is connected to an external circulating cooling device.

5. The ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to claim 3, characterized in that, The upper heating plate (2) is provided with a matrix-type work station slot and a distributed temperature sensor. The work station slot is provided with an elastic positioning pin for quick fixation of the chip carrier and thermal expansion compensation.

6. The ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to claim 3, characterized in that, The reflective layer includes a first reflective heat insulation plate (7) and a second heat insulation plate. The first reflective heat insulation plate (7) is disposed on the upper cover of the heating furnace body (1) and is made of mirror metal material, used to cover the outer surface of the heating system. The second heat insulation plate is disposed below the multi-layer assembled heating plate, and is made of ceramic matrix composite material and forms an air heat insulation cavity with the first reflective heat insulation plate (7) at intervals. The external water-cooled plate (4) covers the outer wall of the vacuum chamber and forms a parallel heat dissipation network with the cooling pipe of the lower heating plate (17) through the circulating water channel.

7. The ultra-high vacuum eutectic furnace for optoelectronic chip packaging according to claim 1, wherein, The reducing atmosphere supply unit also includes: A gas mixing cavity is connected with a nitrogen source, a hydrogen source and a formic acid source through a vacuum four-way valve respectively; A gas injection nozzle is arranged at the bottom of the vacuum cavity and is distributed in an annular array. The outlet direction of the nozzle is at an inclined angle with the plane of the multi-layer assembled heating plate to enhance the uniformity of the gas flow.

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