Chip on flexible substrate （COF） is a new packaging technology for light emitting diodes （LED）. This paper investigated the effect of Cu-pillar in the polyimide （PI） layer on the thermal properties of COF LED pa...Chip on flexible substrate （COF） is a new packaging technology for light emitting diodes （LED）. This paper investigated the effect of Cu-pillar in the polyimide （PI） layer on the thermal properties of COF LED pack- ages by finite element analysis. The thermal distribution and thermal resistance were studied in both COF LED packages with and without Cu-pillar. The PI layer showed the highest thermal resistance in the typical package and led to a high chip temperature. With the addition of Cu-pillars, however, the thermal resistance of the PI layer sig- nificantly decreased due to the improvement of vertical thermal dissipation under LED chips. Based on the results of simulation and calculation, the relationship between the amount of Cu-pillar and thermal resistance of the COF package has been built. For the packages studied in this research, an 8 × 8 Cu-pillars array was adequate to improve the thermal performance of COF packages.展开更多
The addition of Cu nanoparticles into the solder pastes by mechanical mixing method creates a positive effect on the microstructure refinement of the LED solder joints. The grain size of β-Sn and Cu6Sn5 decrease obvi...The addition of Cu nanoparticles into the solder pastes by mechanical mixing method creates a positive effect on the microstructure refinement of the LED solder joints. The grain size of β-Sn and Cu6Sn5 decrease obviously due to the increasing concentration of the nanoparticles in the solder pastes. However, the addition of nanoparticles facilitates the formation of voids in the solder joints, especially when the concentration of nanopar- ticles is higher than 0.5 wt% in the solder pastes. Both the microstructure refinement and void percentage affect the shear strength of the solder joints. Since the increase of the void percentage is limited when the concentration of nanoparticles increases from 0 to 0.5 wt%, the microstructure refinement shows a dominant effect on the shear performance and thus improves the shear strength of the solder joints from 49.8 to 55 MPa. Further addition of nanoparticles in the solder pastes leads to a sharp increase of the void percentage. Consequently, the shear strength of the solder joints decreases from 55 to 48.8 MPa when the concentration of doped particles increases from 0.5 to 1 wt% in the solder pastes.展开更多
基金Project supported by the Research and Scientific Foundation of Heilongjiang Education Department(No.12541112)
文摘Chip on flexible substrate （COF） is a new packaging technology for light emitting diodes （LED）. This paper investigated the effect of Cu-pillar in the polyimide （PI） layer on the thermal properties of COF LED pack- ages by finite element analysis. The thermal distribution and thermal resistance were studied in both COF LED packages with and without Cu-pillar. The PI layer showed the highest thermal resistance in the typical package and led to a high chip temperature. With the addition of Cu-pillars, however, the thermal resistance of the PI layer sig- nificantly decreased due to the improvement of vertical thermal dissipation under LED chips. Based on the results of simulation and calculation, the relationship between the amount of Cu-pillar and thermal resistance of the COF package has been built. For the packages studied in this research, an 8 × 8 Cu-pillars array was adequate to improve the thermal performance of COF packages.
基金supported by the National Natural Science Foundation of China(No.51604090)the Zhejiang Province Key Laboratory of Soldering&Brazing Materials and Technology(No.1402)
文摘The addition of Cu nanoparticles into the solder pastes by mechanical mixing method creates a positive effect on the microstructure refinement of the LED solder joints. The grain size of β-Sn and Cu6Sn5 decrease obviously due to the increasing concentration of the nanoparticles in the solder pastes. However, the addition of nanoparticles facilitates the formation of voids in the solder joints, especially when the concentration of nanopar- ticles is higher than 0.5 wt% in the solder pastes. Both the microstructure refinement and void percentage affect the shear strength of the solder joints. Since the increase of the void percentage is limited when the concentration of nanoparticles increases from 0 to 0.5 wt%, the microstructure refinement shows a dominant effect on the shear performance and thus improves the shear strength of the solder joints from 49.8 to 55 MPa. Further addition of nanoparticles in the solder pastes leads to a sharp increase of the void percentage. Consequently, the shear strength of the solder joints decreases from 55 to 48.8 MPa when the concentration of doped particles increases from 0.5 to 1 wt% in the solder pastes.
