Laser sintering apparatus and sintering method

Abstract

This invention proposes a laser sintering apparatus and a laser sintering method. The laser sintering apparatus includes: a laser, a temperature sensor, a pressure sensor base, a motion platform, a light-transmitting plate, and a weight load. The laser sintering apparatus and method proposed above control the sintering temperature in real time, avoiding damage to the chip and substrate caused by excessively high sintering temperatures, while improving the overall mechanical strength and fatigue resistance reliability of the sintered body.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging, and more particularly to a laser sintering apparatus and sintering method. Background Technology

[0002] As electronic products evolve towards higher power, higher density, and higher integration, higher demands are being placed on interconnect materials in power devices. Due to its nanoscale effect, silver nanoparticle paste offers advantages such as low sintering temperature, high thermal conductivity, and suitability for high-temperature environments, making it more suitable for high-temperature, high-power, and high-power-density packaging. It is gradually replacing tin-lead solder as the preferred interconnect material for high-power electronic devices in high-temperature applications. Currently, hot-pressing sintering is the primary method for interconnecting large-area chips with silver nanoparticle paste. This requires external pressure and complex temperature profiles, sometimes necessitating an inert gas atmosphere. The sintering process is complex, resulting in long sintering times, low efficiency, and high requirements for automated production equipment. Furthermore, prolonged sintering not only easily leads to severe growth of silver nanoparticles, reducing the performance of the sintered joint, but excessive heating can also affect the mechanical and electrical properties of electronic components. Therefore, the development of rapid sintering methods for silver nanoparticle paste used for chip interconnects is attracting increasing attention.

[0003] Existing technologies employing laser low-temperature sintering offer a rapid, high-energy sintering process with a simple design. Automation can be achieved by controlling irradiation time and laser power parameters. Due to its non-contact heating and small laser spot diameter, laser sintering allows for precise selective sintering, avoiding thermal shock to surrounding materials, especially sensitive components. Combining flexible substrates with laser sintering to fabricate flexible hybrid electronics not only significantly improves manufacturing efficiency but also produces flexible devices with good flexibility and repeated bending performance, showing broad application prospects in wearable electronics, electronic skin, implantable electronics, and soft robotics.

[0004] However, rapid laser sintering at low temperatures generates a large amount of heat in a short time, causing the sintering temperature to rise sharply. Excessively high sintering temperatures can easily ablate the flexible substrate and are also detrimental to the formation of a pure silver sintered body with low porosity and high electrical conductivity. Conversely, excessively low sintering temperatures result in low mechanical strength in certain areas of the sintered flexible substrate and chip, ultimately affecting the fatigue resistance and reliability of the sintered joint. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that excessively high or low laser sintering temperatures affect the packaging quality, and the present invention provides a laser sintering apparatus and a sintering method.

[0006] To address the aforementioned problems, this invention provides a laser sintering apparatus, comprising a base for placing a substrate with a chip attached; a light source for sintering the chip; a temperature sensor for monitoring the temperature signal of the chip sintering area during the sintering process and transmitting it to an external computer, wherein the light source adjusts the sintering light intensity and sintering time based on the detection results of the temperature sensor; and a light-transmitting plate disposed in the optical path of the light source for buffering the thermal shock of the light source and placing a weight load.

[0007] To address the aforementioned problems, this invention provides a laser sintering method, characterized by the following steps: providing a substrate, wherein a chip is bonded to the surface of the substrate using a paste; placing the substrate on a pressure sensor base; irradiating the chip surface to sinter the chip region; monitoring the sintering temperature, sintering pressure, and sintering time of the chip sintering region; adjusting the laser power to stabilize the sintering temperature of the chip sintering region; and cooling to obtain a packaged device.

[0008] The laser sintering apparatus and method proposed in the above technical solution, by controlling the sintering temperature in real time, avoid damage to the chip and substrate caused by excessively high sintering temperatures, while simultaneously improving the overall mechanical strength and fatigue resistance reliability of the sintered body. It enables rapid sintering of the paste in the chip area, significantly reducing potential thermal shock damage to the chip and other temperature-sensitive components. It also achieves low-temperature and robust bonding sintering of nano-paste, improving connection strength. This allows for the fabrication of sintered bodies with good electrical conductivity and mechanical bending properties for chip interconnection, showing broad application prospects in flexible electronics and power electronics packaging. Attached Figure Description

[0009] Appendix Figure 1 The diagram shown is a structural schematic of a specific embodiment of the laser sintering apparatus of the present invention.

[0010] Appendix Figure 2 The diagram shows a step-by-step illustration of a specific embodiment of the laser sintering method of the present invention. Detailed Implementation

[0011] The specific embodiments of the laser sintering apparatus and sintering method provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0012] Appendix Figure 1 The diagram shown is a structural schematic of a specific embodiment of the laser sintering device of the present invention, including: a base 10, a light source 11, a temperature sensor 12, a light-transmitting plate 13, a motion platform 15, a pressure sensor 17, and a weight load 14.

[0013] The base 10 is used to hold the substrate 16 to which the chip is attached. The base 10 is a platform for holding the substrate 16, which is a substrate for semiconductor device packaging. In one specific embodiment, the base 10 is made of ceramic. In other specific embodiments, the base 10 may also be made of metal or other common materials used for semiconductor device packaging.

[0014] The light source 11 is used for sintering the chip. In one specific embodiment, the light source 11 is an Nd:YAG laser with a power range of 100W-200W, a scanning speed of 2m / s-5m / s, a spot diameter of 10μm-100μm, a pulse width of 5ns-24ns, a pulse frequency of 40kHz-100kHz, and a wavelength of 1064nm.

[0015] In other specific embodiments, the light source 11 can also be an Nd:YVO4 laser or a helium-neon laser. The power range can also be 10W-100W, the scanning speed can be 0.01m / s-2m / s, the spot diameter can be 10μm-100μm, the pulse width can be 50fs-5ns or 24ns-200ns, the pulse frequency can be 100kHz-300kHz, and the wavelength can be 355nm, 532nm, or 970nm. The aforementioned light source 11 can also be further connected to an external computer, through which the laser power and spot diameter can be adjusted.

[0016] Temperature sensor 12 is used to monitor the temperature signal of the chip sintering area during the sintering process and transmit it to an external computer. The light source 11 adjusts the sintering light intensity and sintering time based on the detection result of temperature sensor 12. In one specific embodiment, temperature sensor 12 is a non-contact infrared temperature sensor. In other specific embodiments, temperature sensor 12 can also be a contact sensor, including thermocouple sensors and thermistor sensors. To further adjust the sintering intensity, this specific embodiment further includes a light-transmitting plate 13, which is disposed in the light path of the light source 11 during sintering to buffer the thermal shock of the light source 11. In one specific embodiment, the material of the light-transmitting plate 13 is glass.

[0017] Optionally, a motion platform 15 is provided and placed below the base 10 to realize the planar displacement and vertical displacement of the substrate 16 during the sintering process. When there are multiple chips to be sintered on the substrate 16, the motion platform 15 can be used to move the substrate 16 on the plane, move the unsintered chips to the position of the beam irradiation, and sinter them one by one until the sintering of all chips is completed.

[0018] A pressure sensor 17, placed within the base 10, is used to monitor the pressure in the sintering region of the chip during the sintering process. To further adjust the sintering pressure, a weight load 14 can optionally be provided, positioned at the four corners above the light-transmitting plate 13. The pressure during the sintering process is adjusted by increasing or decreasing the weight of the weight load. In one specific embodiment, the weight load 14 is made of copper. In other specific embodiments, the weight load 14 can also be made of gold or silver.

[0019] In use, the light source 11 emits a beam of light that passes through the light-transmitting plate 13 and illuminates the chip. Heat is then conducted from the chip to the slurry, initiating sintering in the vicinity of the chip. A temperature sensor 12 detects the temperature of the sintering area and sends it back to an external computer. The external computer adjusts the light source 11 in real time based on the temperature feedback from the temperature sensor 12, stabilizing the temperature of the sintering area. The base 10 serves as a base, and its internal pressure sensor 17 monitors the pressure during the laser sintering process and places weights. The sintering pressure is adjusted by regulating the weight load 14. The movement of the motion platform 15 on a plane allows for the sintering of multiple chips on the same substrate 16. The temperature control loop formed by the light source 11, temperature sensor 12, and external computer regulates the temperature during sintering, preventing damage to the chip and substrate due to excessive temperature. It also ensures sufficient sintering strength, resulting in a high-strength sintered body.

[0020] Appendix Figure 2 The diagram shows a specific implementation of the laser sintering method of the present invention, including the following steps: Step S21, providing a substrate, wherein a chip is bonded to the surface of the substrate using a paste; Step S22, placing the substrate on a base; Step S23, irradiating the chip surface to sinter the chip area; Step S24, monitoring the sintering temperature and sintering pressure of the chip sintering area; Step S25, adjusting the light source power to stabilize the sintering temperature of the chip sintering area; Step S26, cooling to obtain the packaged device.

[0021] Reference Appendix Figure 1 Referring to steps S21 and S22, a substrate 16 is provided. A chip is bonded to the surface of the substrate 16 using a paste, and the substrate 16 is placed on the base 10. The chip can be any type of semiconductor chip, such as a single transistor, integrated circuit, or LED. The substrate 16 is a base used to carry chips in the field of chip packaging, and its material is a polymer substrate. As one specific embodiment, the substrate 16 is polyethylene terephthalate. In other specific embodiments, the substrate 16 can also be polyethylene naphthalate, polydimethylsiloxane, or polyimide.

[0022] In one specific embodiment, the slurry is a nano-silver paste, comprising silver nanoparticles and an organic solvent. The silver nanoparticles have a particle size of 10 nm-300 nm and are spherical or quasi-spherical in shape. In other specific embodiments, the slurry may also be a nano-copper paste, comprising copper nanoparticles and an organic solvent, with a particle size of 300 nm and a spherical shape.

[0023] In one specific embodiment, the base 10 is made of ceramic. In other specific embodiments, the pressure sensor base 10 may also be made of metal or other common materials that can be used for semiconductor packaging.

[0024] Continue to refer to the appendix Figure 1 And in step S23, the chip surface is irradiated to sinter the chip region. As a specific embodiment, prior to sintering, the slurry is further preheated at 532K for 60 seconds. Preheating increases the absorption rate of the laser on the slurry surface, thereby obtaining a sintered joint with high shear strength.

[0025] During sintering, a light beam is emitted from a light source 11, passing perpendicularly through a light-transmitting plate 13 and illuminating the chip. Heat is transferred through the chip to the slurry, initiating sintering near the chip. In one specific embodiment, the light source 11 is an Nd:YAG laser with a power range of 100W-200W, a scanning speed of 2m / s-5m / s, a spot diameter of 10μm-100μm, a pulse width of 5ns-24ns, a pulse frequency of 40kHz-100kHz, and a wavelength of 1064nm. The laser 11 is connected to an external computer, through which the laser power is adjusted. In other specific embodiments, the light source 11 can also be an Nd:YVO4 laser or a helium-neon laser. The power range can be 10W-100W, the scanning speed can be 0.01m / s-2m / s, the spot diameter can be 10μm-100μm, the pulse width can be 50fs-5ns or 24ns-200ns, the pulse frequency can be 100kHz-300kHz, and the wavelength can be 355nm, 532nm, and 970nm.

[0026] The transparent plate 13 reduces thermal shock and lowers the likelihood of damage to the chip and substrate 16. The transparent plate 13 is made of glass. In other embodiments, thermal shock can also be reduced by setting an increasing gradient in laser power.

[0027] Continue to refer to the appendix Figure 1And in step S24, the sintering temperature and sintering pressure of the chip sintering region are monitored. In one specific implementation, a non-contact infrared temperature sensor 12 is used to monitor the temperature of the chip sintering region and transmit the temperature signal to an external computer. In other specific implementations, a contact temperature sensor 12 can also be used to monitor the temperature of the chip sintering region.

[0028] Pressure sensor 17 is used to monitor the pressure in the chip sintering area and directly display the pressure data during the sintering process digitally. The pressure can be adjusted by increasing or decreasing the weight or number of weights 14.

[0029] In one specific embodiment, the weight load 14 is made of copper. In other specific embodiments, the weight load 14 may also be made of gold or silver.

[0030] Continue to refer to the appendix Figure 1 In step S25, the power of the light source 11 is adjusted to stabilize the sintering temperature of the chip sintering area. As a specific implementation, based on the real-time temperature of the chip sintering area transmitted by the temperature sensor 12, the power of the light source 11 is adjusted in real-time using an external computer, thereby controlling the temperature of the chip sintering area and stabilizing it at a certain level. This prevents excessive temperature from burning the chip and substrate 16, ensures sintering strength, and improves the overall mechanical strength and fatigue resistance of the sintered body. During the sintering process, all organic solvents in the slurry evaporate, resulting in a pure silver sintered product with high conductivity, giving the silver sintered body strong shear strength.

[0031] Continue to refer to the appendix Figure 1 And in step S26, cooling is performed to obtain the packaged device. In one specific implementation, after the chip sintering is complete, it can be cooled to obtain the packaged device. In other specific implementations, if multiple chips to be sintered are attached to the same substrate 16, the motion platform 15 can be used to move the plane of the substrate 16, moving the unsintered chips to the position irradiated by the light beam. Steps S23 to S25 are repeated until all chips are sintered, and then cooling is performed to obtain the packaged device.

[0032] The above technical solution, by setting a temperature control loop in the laser sintering apparatus and using a non-contact infrared temperature sensor 12 to monitor the sintering temperature of the chip sintering area, provides real-time feedback and adjusts the power of the light source 11. This not only avoids thermal damage to the chip and substrate 16 that may be caused by excessively high temperatures, but also improves the overall mechanical strength and fatigue resistance reliability of the sintered body. This laser sintering apparatus can achieve rapid sintering of the paste in the chip-compatible region, greatly reducing potential thermal shock damage to the chip and other temperature-sensitive components. It also achieves low-temperature and strong bonding sintering of nano-slurries, improving connection strength. This not only broadens the range of substrate materials to be selected but also simplifies the sintering process, resulting in a sintered body with high electrical conductivity. This method can produce sintered bodies with good electrical conductivity and mechanical bending properties for chip interconnection, showing broad application prospects in flexible electronics and power electronics packaging.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A laser sintering apparatus, characterized in that, include The base is used to hold the substrate on which the chip is attached; Light source, used for sintering chips; A temperature sensor is used to monitor the temperature signal of the chip sintering area during the sintering process and transmit it to an external computer. The light source adjusts the sintering light intensity and sintering time according to the detection results of the temperature sensor. A light-transmitting plate is set in the optical path of the light source sintering to buffer the thermal shock of the light source and to place the weight load. The weight load is placed at the four corners above the light-transmitting plate to adjust the pressure during the sintering process. A pressure sensor, placed inside the base, is used to monitor the pressure in the chip sintering area during the sintering process.

2. The apparatus according to claim 1, characterized in that, The device also includes The motion platform, located below the base, is used to realize the planar and vertical displacement of the substrate during the sintering process.

3. The apparatus according to claim 1, characterized in that, The light source is a laser, specifically selected from Nd:YAG lasers and Nd:YVO4 lasers.

4. The apparatus according to claim 3, characterized in that, The laser has a power range of 10W-200W, a scanning speed of 0.01m / s-5m / s, a spot diameter of 10μm-100μm, a pulse width of 50fs-200ns, a pulse frequency of 40 kHz-300kHz, and a wavelength of one of 355nm, 532nm, 970nm, and 1064nm.

5. The apparatus according to claim 1, characterized in that, The temperature sensor is a non-contact infrared temperature sensor.

6. The apparatus according to claim 1, characterized in that, The base is made of ceramic; the light-transmitting plate is made of glass.

7. A laser sintering method using the laser sintering apparatus of claim 1, characterized in that, Includes the following steps: A substrate is provided, and a chip is bonded to the surface of the substrate by means of a paste. Place the substrate on the base; The chip surface is irradiated, and the chip area is sintered. Monitor the sintering temperature and sintering pressure in the chip sintering area, and adjust the pressure by increasing or decreasing the weight or number of weights. Adjust the light source power to stabilize the sintering temperature in the chip sintering area; Cooling yields the packaged device.

8. The method according to claim 7, characterized in that, The slurry is a nano-silver paste, containing silver nanoparticles and an organic solvent. The silver nanoparticles have a particle size of 10nm-300nm and a spherical or quasi-spherical shape. The substrate is a polymer substrate, containing at least one of polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, or polyimide.

9. The method according to claim 7, characterized in that, Prior to the sintering step of the chip region, the slurry is further preheated at 532K for 60s.

10. The method according to claim 7, characterized in that, When sintering multiple chips onto the same substrate, the substrate is moved by a motion platform, and each chip is sintered one by one.

Images