[Text / high-tech LED Yue Mengdi] Recently, Guangsong's entry into Foshan Lighting has become a hot spot in the industry. Guoxing Optoelectronics (002449.SZ), another LED subsidiary of Guangsheng, has also been followed by the industry.
Guoxing Optoelectronics is one of the industry's largest industrial chain layouts in the LED industry. From upstream chips, midstream packaging, to downstream lighting applications, there are related layouts. And packaging is the main business of the company.
The "New Composite Electrode Flip Chip and Thin Film Substrate CSP Package" proposed by Guoxing Optoelectronics has opened up a new direction in packaging principle (ultra-thin substrate preparation and packaging). It is an innovative technical route and has been applied for. A number of invention patents can be applied to backlights, high-density lighting, projection equipment, high-end indications and other fields.
Dr. Li Cheng, deputy general manager of Guoxing Optoelectronics, introduced that there is a large thermal expansion mismatch due to GaN (expansion coefficient less than 5ppm/K) under the flip chip and multi-layer metal structure and MCPCB (expansion coefficient 18-23ppm/K). After the solid crystal is formed, a large leakage current appears, and after the power is stopped, the leakage current decreases with the cooling time of the chip. It can be inferred that the stress generated by the thermal expansion mismatch of the material easily damages the GaN layer and introduces a transition substrate. Conduction can be suppressed or blocked from being conducted to the GaN layer.
How to ensure the reliability of CSP? It is understood that the addition of a transition substrate in a flip chip CSP device is currently the most effective means of blocking the thermal mismatch stress of the MCPCB to the chip. Li Cheng said that the thickness of the transition substrate used by China Star Optoelectronics is 100 μm thin film ceramic, The finite element simulation results show that the stress in the refining zone is reduced by 71.2% and the GaN layer is reduced by 91.2% after the introduction of the transition substrate, which effectively ensures the high reliability of the CSP device."
The thermal shock (-40 ° C ~ 100 ° C) experiment further confirmed the above inference, the straight welded structure failed in 100 cycles, the failure rate was up to 70% after 300 cycles, and the thickness of the solid crystal layer was increased by solder paste. Stress transmission can be suppressed, but its reliability still has a high risk. Failure occurs after 100 cycles. The failure rate reaches 30% after 3000 cycles. Only the transition substrate structure maintains 0 failure.
Dr. Li Cheng believes that CSP must be a trend, but it can only achieve its optimal cost performance if it is applied to the most suitable place.
Guoxing Optoelectronics is one of the industry's largest industrial chain layouts in the LED industry. From upstream chips, midstream packaging, to downstream lighting applications, there are related layouts. And packaging is the main business of the company.
The "New Composite Electrode Flip Chip and Thin Film Substrate CSP Package" proposed by Guoxing Optoelectronics has opened up a new direction in packaging principle (ultra-thin substrate preparation and packaging). It is an innovative technical route and has been applied for. A number of invention patents can be applied to backlights, high-density lighting, projection equipment, high-end indications and other fields.
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Dr. Li Cheng, deputy general manager of Guoxing Optoelectronics, introduced that there is a large thermal expansion mismatch due to GaN (expansion coefficient less than 5ppm/K) under the flip chip and multi-layer metal structure and MCPCB (expansion coefficient 18-23ppm/K). After the solid crystal is formed, a large leakage current appears, and after the power is stopped, the leakage current decreases with the cooling time of the chip. It can be inferred that the stress generated by the thermal expansion mismatch of the material easily damages the GaN layer and introduces a transition substrate. Conduction can be suppressed or blocked from being conducted to the GaN layer.
How to ensure the reliability of CSP? It is understood that the addition of a transition substrate in a flip chip CSP device is currently the most effective means of blocking the thermal mismatch stress of the MCPCB to the chip. Li Cheng said that the thickness of the transition substrate used by China Star Optoelectronics is 100 μm thin film ceramic, The finite element simulation results show that the stress in the refining zone is reduced by 71.2% and the GaN layer is reduced by 91.2% after the introduction of the transition substrate, which effectively ensures the high reliability of the CSP device."
The thermal shock (-40 ° C ~ 100 ° C) experiment further confirmed the above inference, the straight welded structure failed in 100 cycles, the failure rate was up to 70% after 300 cycles, and the thickness of the solid crystal layer was increased by solder paste. Stress transmission can be suppressed, but its reliability still has a high risk. Failure occurs after 100 cycles. The failure rate reaches 30% after 3000 cycles. Only the transition substrate structure maintains 0 failure.
Dr. Li Cheng believes that CSP must be a trend, but it can only achieve its optimal cost performance if it is applied to the most suitable place.
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