Ultrasonic-field-assisted low-temperature hot-pressed sintering method for chip packaging
The ultrasonic field-assisted low-temperature hot pressing sintering method solves the problems of poor sintering effect of traditional hot pressing sintering on easily oxidized metals and damage to chips due to high temperature and high pressure. It enables the formation of high-strength interconnects under low temperature conditions, improving the reliability and performance of packaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-17
AI Technical Summary
Traditional hot pressing sintering processes are not effective for easily oxidized metals, and the high temperature and pressure can easily damage the chip. It is difficult to achieve efficient and controllable intervention of ultrasonic energy at the micro-nano scale sintering interface, which makes it difficult for the thermal conductivity, electrical conductivity and mechanical strength of the interconnect to meet the requirements of high reliability packaging.
The ultrasonic field-assisted low-temperature hot-pressing sintering method uses ultrasonic vibration to break the oxide layer under low-temperature conditions by delaying the start of hot pressing. This promotes atomic diffusion and metallurgical bonding. Combined with precise control driven by a servo motor, the synergistic effect of the thermal field, force field and ultrasonic field is achieved.
It significantly reduces the risk of thermal stress damage to the chip, improves the interface bonding strength and density, enhances the electrical conductivity, thermal conductivity and mechanical properties of the interconnects, and ensures the stability and yield of high-reliability packaging.
Smart Images
Figure CN121693221A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor packaging manufacturing, and in particular relates to an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging. Background Technology
[0002] In the field of power semiconductor packaging manufacturing technology, the interconnect quality between the chip and the substrate is a key factor determining the final performance, reliability, and lifespan of the device. Achieving high-strength, high-conductivity, high-thermal-conductivity, and stable interconnects has always been a core pursuit in this field. Hot pressing sintering is a widely used chip interconnect technology. It applies a certain temperature and pressure to induce the densification and sintering of metal micro / nano particles filling the interface, thereby forming a reliable metallurgical bond. However, traditional hot pressing sintering processes face significant limitations in practical applications. First, to obtain sufficiently dense sintered necks and good interfacial bonding strength, the process usually relies on high sintering temperatures and high sintering pressures. Sintering temperatures are typically greater than 250°C. High-pressure environments can introduce significant thermal and mechanical stresses into sensitive semiconductor chips, easily leading to microcracks, lattice damage, or performance degradation within the chip. This problem is particularly prominent for miniaturized, thinner, and heat- and force-sensitive advanced chips. Furthermore, with the increasing demand for highly conductive and low-cost materials, sintering pastes of easily oxidized metals such as copper have received widespread attention. However, traditional hot pressing sintering is not effective in treating sintering pastes of easily oxidized metals. During the sintering process, the natural oxide layer on the surface of copper particles is difficult to remove effectively at conventional low temperatures, severely hindering atomic diffusion and metallurgical bonding between particles. This results in high porosity and poor density in the sintered body, ultimately making it difficult for the thermal conductivity, electrical conductivity, and mechanical strength of the interconnects to meet the requirements of high-reliability packaging.
[0003] Existing technologies include methods for introducing ultrasonic vibration to assist in material forming. However, ultrasonic vibration is mostly used for welding or material processing. It is not possible to efficiently and controllably introduce ultrasonic energy into the micro-nano scale sintering interface of chip packaging and achieve precise temporal and spatial coordination with the thermal and force fields. If the ultrasonic vibration is not properly processed after introduction, disordered or excessive ultrasonic energy may have a superimposed effect with high temperature, which may exacerbate the potential damage to the chip's functional structure. At the same time, there is currently no mature and efficient solution for designing the process timing so that ultrasound can be precisely intervened at key stages of the sintering process to break the oxide layer, reduce the sintering activation energy, and avoid damaging the already formed fragile sintering framework. Summary of the Invention
[0004] In view of this, the present invention aims to propose an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging, in order to solve the problems that traditional hot pressing sintering is prone to chip damage due to high temperature and high pressure and has poor sintering effect on easily oxidized materials.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: an ultrasonic field-assisted low-temperature hot-pressing sintering method for chip packaging, comprising the following steps: S1: Apply sintering slurry between the workpieces to be connected, and then dry it to form a pre-sintered layer; S2: Start the heating device of the hot pressing sintering device to make the heating temperature reach the sintering temperature, transfer the workpiece forming the pre-sintered layer to the support platform of the heated device after heating, and then control the ultrasonic composite pressure head to move downward through the pressure application mechanism so that the ultrasonic composite pressure head contacts the workpiece and applies sintering pressure to start the sintering process. The ultrasonic composite pressure head does not have an active heating element for heating the workpiece. S3: When the preset ultrasonic start time is reached after the sintering pressure is applied, the ultrasonic application mechanism is activated. The ultrasonic start time is within 1 to 2 minutes after the sintering pressure is applied. Ultrasonic vibration is applied to the workpiece through the ultrasonic composite pressure head. S4: After the ultrasonic vibration ends, maintain the sintering pressure and sintering temperature until the predetermined total sintering time is reached, then stop heating and remove the pressure head to complete the sintering.
[0006] Furthermore, the predetermined total sintering time is 10 minutes.
[0007] Furthermore, the sintering temperature is 180℃~240℃, and the sintering pressure ranges from 5MPa to 25MPa.
[0008] Furthermore, the duration of ultrasonic vibration is 1 to 60 seconds.
[0009] Furthermore, the ultrasonic composite pressure head has a power of 300~1200W and a frequency of 20KHz.
[0010] Furthermore, the sintering slurry is a copper-based slurry.
[0011] Furthermore, in S2, the movement of the ultrasonic composite pressure head is driven by a pressure application mechanism, which is controlled by a servo motor drive mechanism.
[0012] Furthermore, the servo motor mechanism, pressure application mechanism, ultrasonic application mechanism, and heating device are all electrically connected to the control box, which controls the parameters of sintering pressure, sintering temperature, ultrasonic start-up time, and ultrasonic vibration time.
[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention adopts a thermal management mode of bottom heating and upper pressure head maintaining room temperature, so that the front side of the chip that is in direct contact with the ultrasonic composite pressure head is in a relatively low temperature state, avoiding the severe and uneven thermal shock caused by double-sided heating in traditional hot pressing sintering. This significantly reduces the thermal stress and thermal damage risk that the chip is subjected to during the packaging process. The actual average temperature of the workpiece is lower than the set temperature of the bottom heating stage, thus realizing low-temperature sintering. Under the condition of ensuring sintering drive, the compatibility and safety of the process for heat-sensitive chips are further improved, which helps to improve the packaging yield and long-term reliability. 2. This invention addresses the core problem of the oxide layer on the surface of easily oxidized materials such as copper hindering atomic diffusion. By controlling the delayed start of the ultrasonic field after the start of hot pressing, the ultrasonic vibration is introduced at the appropriate time when the organic carrier is properly volatilized and the particles are in initial contact. The high-frequency energy and acoustic cavitation effect generated by the ultrasonic vibration can effectively break and peel off the oxide film on the surface of the metal particles, exposing a clean and active metal surface. This creates the necessary conditions for subsequent metallurgical bonding and fundamentally solves the problem of weak interfacial bonding and high porosity caused by the presence of oxide layer in traditional low-temperature hot pressing sintering. 3. While breaking the oxide layer, the ultrasonic vibration energy applied by this invention can reduce the diffusion activation energy of atoms, significantly promote the interdiffusion and recrystallization process of atoms at the interface, and enhance the plastic flow capacity of the material under pressure and temperature. This ultrasonic-assisted activation effect can improve the bonding strength and density of the sintering interface at temperatures of 180℃~240℃ and pressures of 5MPa~25MPa, which are much lower than those of traditional hot pressing sintering processes. 4. This invention utilizes the ultrasonic field to remove the oxide layer at the interface and promote atomic diffusion and material flow, making the bonding between metal particles during sintering more complete and rapid. This significantly improves the electrical conductivity, thermal conductivity, and mechanical properties of the interconnect, thereby ensuring the long-term stable operation of power chip interconnects under high-load and high-reliability application scenarios. 5. This invention precisely controls the application of ultrasonic energy at key stages of the sintering process by presetting the ultrasonic start time, such as 1-2 minutes after the start of hot pressing, and the ultrasonic action time, such as 1-60 seconds. This controllability of timing and parameters enables the ultrasonic field to achieve efficient synergy with the thermal and force fields, maximizing the sintering-assisted benefits of ultrasound while avoiding the adverse effects that ultrasonic energy may bring in the early or late stages of sintering. Moreover, all parameters can be integrated and controlled through the control box, resulting in good process stability and repeatability. Attached Figure Description
[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a process flow timing diagram of an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 2 This is a first-view axial side view of the sintering apparatus for an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 3 This is a second-view axial side structural diagram of the sintering apparatus for an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 4 This is a schematic diagram of the internal axial structure of the sintering apparatus for an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 5 This is a front view of the internal structure of the sintering apparatus for an ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 6 This is a partial front view of the internal structure of the sintering apparatus of the ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 7 This is a schematic diagram of the axial structure of the ultrasonic application mechanism of the sintering apparatus in the ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention. Figure 8 This is a front view schematic diagram of the ultrasonic application mechanism of the sintering apparatus in the ultrasonic field-assisted low-temperature hot pressing sintering method for chip packaging according to the present invention.
[0015] In the picture: 1. Outer shell; 2. Base; 3. Servo motor; 4. Control box; 5. Bearing seat; 6. Electric cylinder housing; 7. Flange; 8. Upper plate; 9. Middle plate; 10. Transmission rod; 11. Fixing frame; 12. Guide column; 13. Ultrasonic application mechanism; 14. Heating device; 15. Transducer; 16. Amplifier rod; 17. Tool head; 18. Support plate; 19. Heat insulation plate; 20. Pressure sensor; 21. Base plate; 22. Display screen. Detailed Implementation
[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.
[0017] Detailed Implementation Method 1: See Figure 1-8 This embodiment describes a low-temperature hot-pressing sintering method for chip packaging assisted by an ultrasonic field, comprising the following steps: S1: Apply sintering slurry between the workpieces to be connected, and then dry it to form a pre-sintered layer. The workpieces to be connected are chips and substrates or two layers of copper sheets. The workpieces to be connected are dried on a drying table at 80℃~120℃ to form a pre-sintered layer with a certain mechanical strength. S2: Start the heating device 14 of the hot pressing sintering device to bring the heating temperature to the sintering temperature, transfer the workpiece forming the pre-sintered layer to the support stage 18 of the heated device 14, and then control the ultrasonic composite pressure head to move downward through the pressure application mechanism so that the ultrasonic composite pressure head contacts the workpiece and applies sintering pressure to start the sintering process. The ultrasonic composite pressure head does not have an active heating element for heating the workpiece, so that the front side of the chip that is in direct contact with the ultrasonic composite pressure head is in a relatively low temperature state, avoiding the severe and uneven thermal shock caused by double-sided heating in traditional hot pressing sintering, thereby significantly reducing the risk of thermal stress and thermal damage to the chip during the packaging process. S3: When the preset ultrasonic start time is reached after the sintering pressure is applied, the ultrasonic application mechanism 13 is activated. The ultrasonic start time is within 1 to 2 minutes after the sintering pressure is applied. The ultrasonic composite pressure head applies ultrasonic vibration to the workpiece. The preset ultrasonic start time is set based on the physical stage of the sintering process. Usually, within 1 to 2 minutes after the sintering pressure is applied, the organic carrier in the slurry has basically volatilized, and the metal particles form preliminary mechanical contact and heat transfer. However, the oxide layer on the particle surface has not yet broken, and the sintering neck has not yet grown significantly. Ultrasonic vibration is introduced at this time to use ultrasonic energy to most effectively break the oxide layer and activate the interface for atomic diffusion. At the same time, it avoids interfering with the stability of the slurry by applying ultrasonic too early or damaging the sintering neck that has been formed by applying it too late. This time window is determined through pre-experimentation based on the specific slurry formula and the heat capacity of the workpiece. S4: After the ultrasonic vibration ends, maintain the sintering pressure and sintering temperature until the predetermined total sintering time is reached. Stop heating and remove the pressure head to complete the sintering. That is, after the ultrasonic vibration ends, continue to maintain the temperature and pressure at the sintering pressure and sintering temperature until the predetermined total sintering time is reached. Finally, release the pressure, remove the ultrasonic composite pressure head, and remove the workpiece to complete the entire packaging interconnection process.
[0018] The predetermined total sintering time is 10 minutes.
[0019] The sintering temperature is 180℃~240℃, and the sintering pressure ranges from 5MPa to 25MPa.
[0020] The duration of ultrasonic vibration is 1 to 60 seconds.
[0021] The ultrasonic composite pressure head has a power of 300~1200W and a frequency of 20KHz.
[0022] The sintering slurry is a copper-based slurry, which typically contains micro- and nano-sized copper particles as the main functional phase and is mixed with a specific organic carrier. The organic carrier is generally composed of solvents, dispersants, binders, etc., and its function is to form suitable rheological properties for coating and to volatilize or decompose during the drying process. The copper particles can be spherical, flake-shaped, or a combination thereof, with a particle size range, for example, between 0.1 micrometers and 10 micrometers, to facilitate filling and sintering densification. By introducing ultrasonic vibration, the obstacle of the oxide layer on the surface of the copper particles to atomic diffusion can be effectively overcome, thereby achieving effective metallurgical bonding between copper particles at a low temperature of 180℃ to 240℃.
[0023] See Figure 2-8 This embodiment describes a hot pressing sintering apparatus that includes a frame, a control system, an ultrasonic application mechanism 13 and a heating device 14 that are coordinated by the system.
[0024] The frame is the support and guide structure of the hot pressing sintering device, mainly including a shell 1, a base 2, an upper plate 8, a middle plate 9, a bottom plate 21 and multiple guide columns 12. The shell 1 is covered on the outside, the base 2 serves as the foundation, the bottom plate 21 is installed on the base 2, the upper plate 8 and the middle plate 9 are parallel and spaced apart, the multiple guide columns 12 are vertically fixed on the bottom plate 21 and slide through the corner area of the middle plate 9, and the upper plate 8 is fixed on the top of the guide columns 12.
[0025] The ultrasonic application mechanism is used to provide precise pressure and introduce ultrasonic vibration. The ultrasonic application mechanism is driven by a servo motor 3, which is connected to an electric cylinder. An electric cylinder housing 6 is provided on the outside of the electric cylinder. The electric cylinder housing 6 is installed on the upper plate 8 through a bearing seat 5 and a flange 7. The output end of the electric cylinder is connected to a transmission rod 10. The transmission rod 10 passes through the upper plate 8 and is connected to the middle plate 9, thereby transmitting the driving force to the middle plate 9. A pressure sensor 20 is sleeved on the outside of the transmission rod 10 for real-time pressure monitoring. The ultrasonic application mechanism 13 is installed at the bottom of the middle plate 9 through a fixing frame 11. The ultrasonic application mechanism 13 includes an ultrasonic composite pressure head. The ultrasonic composite pressure head itself does not have an active heating element for heating the workpiece. The ultrasonic composite pressure head includes, from top to bottom, a piezoelectric ceramic transducer 15, an amplitude transformer 16, and a tool head 17 connected through a threaded interface. The ultrasonic generator is connected to the piezoelectric ceramic transducer 15 through a high-frequency cable to provide ultrasonic vibration.
[0026] The heating device 14 is used to support the workpiece and provide the heat energy required for sintering. The heating device 14 includes a support platform 18, in which a heating tube is embedded. It is mounted on a base plate 21 via a heat insulation plate 19. A temperature sensor is provided on the support platform 18 for temperature measurement. The heating device 14 is controlled by a heating control box.
[0027] The control system includes a main control box 44 and a controller installed inside the control box 4. The controller is electrically connected to the servo motor 3, pressure sensor 20, ultrasonic generator, heating control box 4, and temperature sensor. The controller coordinates and controls the timing and parameters of the application of pressure, temperature, and ultrasonic field according to a preset program. A display screen 22 is installed on the outer shell 1 of the hot pressing sintering device for displaying and setting process parameters.
[0028] In step S2, the movement of the ultrasonic composite pressure head is driven by a pressure application mechanism, which is controlled by a servo motor 3 drive mechanism. The servo motor 3 drive mechanism receives instructions from the control system and controls the movement of the pressure application mechanism, thereby driving the ultrasonic composite pressure head to move, thus achieving smooth and precise downward and upward movement. The servo drive system has a closed-loop control function, which can monitor and precisely control the displacement of the pressure head and the applied pressure in real time. In step S2, when it is necessary to press the ultrasonic composite pressure head down to contact the workpiece and apply a preset pressure, the control system sends an instruction to the servo motor 3 to drive the ultrasonic composite pressure head to move downward at a controllable speed. After the ultrasonic composite pressure head contacts the workpiece, the system switches to pressure control mode. Through the real-time feedback signal from the pressure sensor 20, the servo motor 3 drive mechanism continuously performs fine adjustments to dynamically stabilize the sintering pressure at the preset sintering pressure within the set total sintering time.
[0029] The servo motor 3, pressure application mechanism, ultrasonic application mechanism 13, and heating device 14 are all electrically connected to the control box 4. The control box 4 controls the parameters of sintering pressure, sintering temperature, ultrasonic start time, and ultrasonic vibration time. During the process, the control box 4 issues synchronization or timing commands according to the preset program to control the heating device 14. Through temperature sensor feedback, it achieves precise closed-loop control and stabilization of the sintering temperature of the substrate 18. In step S2, the control box 4 sends motion and pressure commands to the servo motor 3 drive mechanism to drive the pressure application mechanism and ultrasonic composite pressure head to complete precise pressure reduction and stabilization. In step S3, when the preset ultrasonic start time is reached, the timing unit inside the control box 4 automatically sends a trigger signal to the ultrasonic application mechanism 13 to control it to output ultrasonic vibration according to the set power, frequency, and time. Throughout the entire process cycle, the control box 4 ensures that each parameter is maintained according to the program until the total sintering time ends.
[0030] This invention achieves a high degree of coordination between the thermal field, force field, and ultrasonic field in terms of timing and magnitude through centralized automated control, ensuring extremely high repeatability, consistency, and reliability of the process, while significantly reducing the uncertainty caused by manual operation, enabling the stable reproduction of the low-pressure, low-temperature, and high-strength sintering process.
[0031] Detailed Implementation Method 2: See Figure 1-8 This embodiment describes a low-temperature hot-pressing sintering method for chip packaging assisted by an ultrasonic field, comprising the following steps: S1: Copper-based sintering slurry is applied between the workpieces to be connected and then dried to form a pre-sintered layer. The workpieces to be connected are a chip and a basic or two layers of copper sheet. S2: The controller in the main control box 4 sends a command to the heating control box, which drives the M-type heating tube in the support platform 18 to work. The thermocouple monitors the temperature in real time and feeds it back to the display screen 22, so that the support platform 18 is heated to 180°C. When the temperature reaches 180°C and stabilizes, the workpiece with the pre-sintered layer is moved to the support platform 18. Then, the servo motor 3 is started through the main control box 4. The servo motor 3 drives the electric cylinder to move according to the command. The linear thrust output by the electric cylinder pushes the transmission rod 10 to the middle plate 9. The movement of the middle plate 9 drives the ultrasonic composite pressure head 13 to move vertically downward, so that the tool head 17 contacts the workpiece and applies a pressure of 25MPa. The pressure sensor 20 monitors the pressure in real time and feeds it back to the display screen 22. The sintering device enters the sintering stage. The sintering stage lasts for 10 minutes. The pressure and temperature remain unchanged during the sintering stage. S3: The ultrasonic generator is started at any time within 1 to 2 minutes after the start of the sintering stage. The ultrasonic generator generates a high-frequency electrical signal with a specific power, which drives the piezoelectric ceramic transducer 15 through a high-frequency cable. The mechanical vibration is amplified by the amplitude transformer 16 and transmitted to the working interface through the tool head 17. At this time, the synergistic effect of the coupling of heat, pressure and ultrasound is formed. The high-frequency micro-amplitude vibration can effectively break the oxide film on the surface of the slurry particles, promote the plastic deformation of the interface, and significantly enhance the atomic diffusion ability through cavitation and other effects. Thus, under the preset sintering temperature and pressure, the sintering densification process is greatly accelerated and optimized. The ultrasonic field has an action time of 1 second. The main control box 4 commands the ultrasonic generator to stop outputting. The start time of the ultrasonic generator is when the sintering interface has been initially formed but has not yet been fully densified. The ultrasonic start time needs to be determined according to the actual working conditions. S4: When the sintering stage reaches 10 minutes, the heating control box stops heating, the electric cylinder is raised, causing the ultrasonic composite pressure head 13 to rise, detach from the workpiece, and the interconnected workpiece is taken out. All components of the device are reset under the command of the main control box 4, ready for the next operation.
[0032] Detailed implementation method 3: See Figure 1-8 This embodiment describes a low-temperature hot-pressing sintering method for chip packaging assisted by an ultrasonic field, comprising the following steps: S1: Copper-based sintering slurry is applied between the workpieces to be connected and then dried to form a pre-sintered layer. The workpieces to be connected are a chip and a basic or two layers of copper sheet. S2: The controller in the main control box 4 sends a command to the heating control box, which drives the M-type heating tube in the support platform 18 to work. The thermocouple monitors the temperature in real time and feeds it back to the display screen 22, so that the support platform 18 is heated to 190°C. When the temperature reaches 190°C and stabilizes, the workpiece with the pre-sintered layer is moved to the support platform 18. Then, the servo motor 3 is started through the main control box 4. The servo motor 3 drives the electric cylinder to move according to the command. The linear thrust output by the electric cylinder pushes the transmission rod 10 to the middle plate 9. The movement of the middle plate 9 drives the ultrasonic composite pressure head 13 to move vertically downward, so that the tool head 17 contacts the workpiece and applies a pressure of 20MPa. The pressure sensor 20 monitors the pressure in real time and feeds it back to the display screen 22. The sintering device enters the sintering stage. The sintering stage lasts for 10 minutes. The pressure and temperature remain unchanged during the sintering stage. S3: The ultrasonic generator is started at any time within 1 to 2 minutes after the start of the sintering stage. The ultrasonic generator generates a high-frequency electrical signal with a specific power, which drives the piezoelectric ceramic transducer 15 through a high-frequency cable. The mechanical vibration is amplified by the amplitude transformer 16 and transmitted to the working interface through the tool head 17. At this time, the synergistic effect of the coupling of heat, pressure and ultrasound is formed. The high-frequency micro-amplitude vibration can effectively break the oxide film on the surface of the slurry particles, promote the plastic deformation of the interface, and significantly enhance the atomic diffusion ability through cavitation and other effects. Thus, under the preset sintering temperature and pressure, the sintering densification process is greatly accelerated and optimized. The ultrasonic field has an action time of 2 seconds. The main control box 4 commands the ultrasonic generator to stop outputting. The start time of the ultrasonic generator is when the sintering interface has been initially formed but has not yet been fully densified. The ultrasonic start time needs to be determined according to the actual working conditions. S4: When the sintering stage reaches 10 minutes, the heating control box stops heating, the electric cylinder is raised, causing the ultrasonic composite pressure head 13 to rise, detach from the workpiece, and the interconnected workpiece is taken out. All components of the device are reset under the command of the main control box 4, ready for the next operation.
[0033] Detailed implementation method 4: See Figure 1-8 This embodiment describes a low-temperature hot-pressing sintering method for chip packaging assisted by an ultrasonic field, comprising the following steps: S1: Copper-based sintering slurry is applied between the workpieces to be connected and then dried to form a pre-sintered layer. The workpieces to be connected are a chip and a basic or two layers of copper sheet. S2: The controller in the main control box 4 sends a command to the heating control box, which drives the M-type heating tube in the support platform 18 to work. The thermocouple monitors the temperature in real time and feeds it back to the display screen 22, so that the support platform 18 is heated to 230°C. When the temperature reaches 230°C and stabilizes, the workpiece with the pre-sintered layer is moved to the support platform 18. Then, the servo motor 3 is started through the main control box 4. The servo motor 3 drives the electric cylinder to move according to the command. The linear thrust output by the electric cylinder pushes the transmission rod 10 to the middle plate 9. The movement of the middle plate 9 drives the ultrasonic composite pressure head 13 to move vertically downward, so that the tool head 17 contacts the workpiece and applies a pressure of 10MPa. The pressure sensor 20 monitors the pressure in real time and feeds it back to the display screen 22. The sintering device enters the sintering stage. The sintering stage lasts for 10 minutes. The pressure and temperature remain unchanged during the sintering stage. S3: The ultrasonic generator is started at any time within 1 to 2 minutes after the start of the sintering stage. The ultrasonic generator generates a high-frequency electrical signal with a specific power, which drives the piezoelectric ceramic transducer 15 through a high-frequency cable. The mechanical vibration is amplified by the amplitude transformer 16 and transmitted to the working interface through the tool head 17. At this time, the synergistic effect of the coupling of heat, pressure and ultrasound is formed. The high-frequency micro-amplitude vibration can effectively break the oxide film on the surface of the slurry particles, promote the plastic deformation of the interface, and significantly enhance the atomic diffusion ability through cavitation and other effects. Thus, under the preset sintering temperature and pressure, the sintering densification process is greatly accelerated and optimized. The ultrasonic field has an action time of 3 seconds. The main control box 4 commands the ultrasonic generator to stop outputting. The start time of the ultrasonic generator is when the sintering interface has been initially formed but has not yet been fully densified. The ultrasonic start time needs to be determined according to the actual working conditions. S4: When the sintering stage reaches 10 minutes, the heating control box stops heating, the electric cylinder is raised, causing the ultrasonic composite pressure head 13 to rise, detach from the workpiece, and the interconnected workpiece is taken out. All components of the device are reset under the command of the main control box 4, ready for the next operation.
[0034] Detailed implementation method 5: See Figure 1-8 This embodiment describes a low-temperature hot-pressing sintering method for chip packaging assisted by an ultrasonic field, comprising the following steps: S1: Copper-based sintering slurry is applied between the workpieces to be connected and then dried to form a pre-sintered layer. The workpieces to be connected are a chip and a basic or two layers of copper sheet. S2: The controller in the main control box 4 sends a command to the heating control box, which drives the M-type heating tube in the support platform 18 to work. The thermocouple monitors the temperature in real time and feeds it back to the display screen 22, so that the support platform 18 is heated to 240°C. When the temperature reaches 240°C and stabilizes, the workpiece with the pre-sintered layer is moved to the support platform 18. Then, the servo motor 3 is started through the main control box 4. The servo motor 3 drives the electric cylinder to move according to the command. The linear thrust output by the electric cylinder pushes the transmission rod 10 to the middle plate 9. The movement of the middle plate 9 drives the ultrasonic composite pressure head 13 to move vertically downward, so that the tool head 17 contacts the workpiece and applies a pressure of 5MPa. The pressure sensor 20 monitors the pressure in real time and feeds it back to the display screen 22. The sintering device enters the sintering stage. The sintering stage lasts for 10 minutes. The pressure and temperature remain unchanged during the sintering stage. S3: The ultrasonic generator is started at any time within 1 to 2 minutes after the start of the sintering stage. The ultrasonic generator generates a high-frequency electrical signal with a specific power, which drives the piezoelectric ceramic transducer 15 through a high-frequency cable. The mechanical vibration is amplified by the amplitude transformer 16 and transmitted to the working interface through the tool head 17. At this time, the synergistic effect of the coupling of heat, pressure and ultrasound is formed. The high-frequency micro-amplitude vibration can effectively break the oxide film on the surface of the slurry particles, promote the plastic deformation of the interface, and significantly enhance the atomic diffusion ability through cavitation and other effects. Thus, under the preset sintering temperature and pressure, the sintering densification process is greatly accelerated and optimized. The ultrasonic field has an action time of 4 seconds. The main control box 4 commands the ultrasonic generator to stop outputting. The start time of the ultrasonic generator is when the sintering interface has been initially formed but has not yet been fully densified. The ultrasonic start time needs to be determined according to the actual working conditions. S4: When the sintering stage reaches 10 minutes, the heating control box stops heating, the electric cylinder is raised, causing the ultrasonic composite pressure head 13 to rise, detach from the workpiece, and the interconnected workpiece is taken out. All components of the device are reset under the command of the main control box 4, ready for the next operation.
[0035] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.
Claims
1. An ultrasonic field assisted chip package low temperature hot press sintering method, characterized by, The method comprises the following steps: S1: applying a sintering paste between the workpieces to be connected, and then performing a drying treatment to form a pre-sintering layer; S2: starting the heating device of the hot-press sintering device to reach a sintering temperature, transferring the workpiece with the pre-sintering layer to a piece supporting table of the heating device after heating, and then controlling the ultrasonic composite pressure head to move downward by a pressure applying mechanism, so that the ultrasonic composite pressure head contacts the workpiece and applies a sintering pressure, and the sintering process is started, wherein the ultrasonic composite pressure head does not have an active heating element for heating the workpiece; S3: after the sintering pressure is applied, when a preset ultrasonic starting time is reached, the ultrasonic applying mechanism is started, the ultrasonic starting time is within 1-2 minutes after the sintering pressure is applied, and ultrasonic vibration is applied to the workpiece by the ultrasonic composite pressure head; S4: after the ultrasonic vibration is ended, the sintering pressure and the sintering temperature are maintained until a predetermined total sintering time is reached, the heating is stopped, and the pressure head is removed, and the sintering is completed.
2. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 1, characterized in that: The predetermined total sintering time is 10 minutes.
3. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 1, characterized in that: The sintering temperature is 180-240°C, and the sintering pressure ranges from 5 MPa to 25 MPa.
4. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 1, characterized in that: The ultrasonic vibration time is 1-60 seconds.
5. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 1, characterized in that: The power of the ultrasonic composite pressure head is 300-1200 W, and the frequency is 20 KHz.
6. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 1, characterized in that: The sintering paste is a copper-based paste.
7. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 1, characterized in that: In S2, the action of the ultrasonic composite pressure head is driven by the pressure applying mechanism, which is controlled by a servo motor driving mechanism.
8. The ultrasonic field assisted chip package low temperature hot pressing sintering method according to claim 7, characterized in that: The servo motor mechanism, the pressure applying mechanism, the ultrasonic applying mechanism, and the heating device are electrically connected with a control box, and the parameters of the sintering pressure, the sintering temperature, the ultrasonic starting time, and the ultrasonic vibration time are controlled by the control box.