Practices of IC package reliability testing are reviewed briefly, and the application of transient thermal analysis is examined in great depth. For the design of light sources based on light emitting diode （LED） eff...Practices of IC package reliability testing are reviewed briefly, and the application of transient thermal analysis is examined in great depth. For the design of light sources based on light emitting diode （LED） efficient and accurate reliability testing is required to realize the potential lifetimes of 105 h. Transient thermal analysis is a standard method to determine the transient thermal impedance of semiconductor devices, e.g. power electronics and LEDs. The temperature of the semiconductor junctions is assessed by time-resolved measurement of their forward voltage （Vf）. The thermal path in the IC package is resolved by the transient technique in the time domain. This enables analyzing the structural integrity of the semiconductor package. However, to evaluate thermal resistance, one must also measure the dissipated energy of the device （i.e., the thermal load） and the k-factor. This is time consuming, and measurement errors reduce the accuracy. To overcome these limitations, an innovative approach, the relative thermal resistance method, was developed to reduce the measurement effort, increase accuracy and enable automatic data evaluation. This new way of evaluating data simplifies the thermal transient analysis by eliminating measurement of the k-factor and thermal load, i.e. measurement of the lumen flux for LEDs, by normalizing the transient Vf data. This is especially advantageous for reliability testing where changes in the thermal path, like cracks and delaminations, can be determined without measuring the k-factor and thermal load. Different failure modes can be separated in the time domain. The sensitivity of the method is demonstrated by its application to high- power white InGaN LEDs. For detailed analysis and identification of the failure mode of the LED packages, the transient signals are simulated by time-resolved finite element （FE） simulations. Using the new approach, the transient thermal analysis is enhanced to a powerful tool for reliability investigation of semiconductor packages in accelerated lifetime tests and for inline inspection. This enables automatic data analysis of the transient thermal data required for processing a large amount of data in production and reliability testing. Based on the method, the integrity of LED packages can be tested by inline, outgoing inspection and the lifetime prediction of the products is improved.展开更多
This study investigates laser sintering of Cu particle-free ink(Cu formate tetrahydrate—amino-2-propanol complex)as an alternative to conventional sintering in an oven(under inert/reducing atmosphere).Utilizing benef...This study investigates laser sintering of Cu particle-free ink(Cu formate tetrahydrate—amino-2-propanol complex)as an alternative to conventional sintering in an oven(under inert/reducing atmosphere).Utilizing benefits of high-speed localized heating using laser,substrate damage can be prevented for low-melting substrates such as Polyethylene Terephthalate(PET).Firstly,a suitable sintering process window is achieved based on energy density for two different flexible polymeric susbtrates:Polyimide and PET using different laser parameters(laser power,scan rate and spot diameter).Subsequently,characterization of laser sintered traces are also made using different laser optic profiles(Gaussian and top hat).Different methodologies for fabrication of metallized Cu layer were also demonstrated.A very low bulk resistivity of 3.24µΩcm(1.87 times of bulk Cu)was achieved on trace thickness of 0.85±0.15µm exhibiting good adherence to polymeric substrates.A promising fabrication process of low-cost and reliable flexible printed electronic devices is demonstrated.展开更多
文摘Practices of IC package reliability testing are reviewed briefly, and the application of transient thermal analysis is examined in great depth. For the design of light sources based on light emitting diode （LED） efficient and accurate reliability testing is required to realize the potential lifetimes of 105 h. Transient thermal analysis is a standard method to determine the transient thermal impedance of semiconductor devices, e.g. power electronics and LEDs. The temperature of the semiconductor junctions is assessed by time-resolved measurement of their forward voltage （Vf）. The thermal path in the IC package is resolved by the transient technique in the time domain. This enables analyzing the structural integrity of the semiconductor package. However, to evaluate thermal resistance, one must also measure the dissipated energy of the device （i.e., the thermal load） and the k-factor. This is time consuming, and measurement errors reduce the accuracy. To overcome these limitations, an innovative approach, the relative thermal resistance method, was developed to reduce the measurement effort, increase accuracy and enable automatic data evaluation. This new way of evaluating data simplifies the thermal transient analysis by eliminating measurement of the k-factor and thermal load, i.e. measurement of the lumen flux for LEDs, by normalizing the transient Vf data. This is especially advantageous for reliability testing where changes in the thermal path, like cracks and delaminations, can be determined without measuring the k-factor and thermal load. Different failure modes can be separated in the time domain. The sensitivity of the method is demonstrated by its application to high- power white InGaN LEDs. For detailed analysis and identification of the failure mode of the LED packages, the transient signals are simulated by time-resolved finite element （FE） simulations. Using the new approach, the transient thermal analysis is enhanced to a powerful tool for reliability investigation of semiconductor packages in accelerated lifetime tests and for inline inspection. This enables automatic data analysis of the transient thermal data required for processing a large amount of data in production and reliability testing. Based on the method, the integrity of LED packages can be tested by inline, outgoing inspection and the lifetime prediction of the products is improved.
基金supported by the Bavarian Collaborative Research Program(BayVFP)of the Free State of Bavaria,Germany within the project‘ADDIRA’’under the grant number DIE-2107-005//DIE0159/01Laser facility at Liverpool John Moore University,Faculty of Engineering and Technology funded through FET Pump Prime Awards 2023/2024.
文摘This study investigates laser sintering of Cu particle-free ink(Cu formate tetrahydrate—amino-2-propanol complex)as an alternative to conventional sintering in an oven(under inert/reducing atmosphere).Utilizing benefits of high-speed localized heating using laser,substrate damage can be prevented for low-melting substrates such as Polyethylene Terephthalate(PET).Firstly,a suitable sintering process window is achieved based on energy density for two different flexible polymeric susbtrates:Polyimide and PET using different laser parameters(laser power,scan rate and spot diameter).Subsequently,characterization of laser sintered traces are also made using different laser optic profiles(Gaussian and top hat).Different methodologies for fabrication of metallized Cu layer were also demonstrated.A very low bulk resistivity of 3.24µΩcm(1.87 times of bulk Cu)was achieved on trace thickness of 0.85±0.15µm exhibiting good adherence to polymeric substrates.A promising fabrication process of low-cost and reliable flexible printed electronic devices is demonstrated.
