| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 96 === In addition to the qualities of light-weight, mini-size, low costs, and excellent electrical and thermal performances, electronic products are further required to have qualities such as multiple functions and high capacity to meet the demand of the market in recent years. With this view, the 3D packaging technology facilitated to above purposes has been gradually noticed. By incorporating with the 3D packaging technology, this study focuses on quad flat lead-free package which is widely used in portable electronic products to further analyze the stacked die QFN package.
This study adopts ANSYS9.0 software for analysis. Based on the JEDEC code, the stacked die QFN is loaded by a temperature cycle of -40℃~125℃. The solder paste is assumed to be Anand’s model. The Coffin-Manson fatigue life formula is applied to predict the fatigue life of the solder paste in the stacked die QFN package.
The single-factor experiment is conducted to predict the impact on the fatigue life of the stacked die QFN in which factors such as the amplitude of temperature cycling range, the average temperature of temperature cycling range, die size, thickness of die, thickness of PCB, CTE of PCB, CTE of mold compound, CTE of adhesive, the shape of solder paste, CTE of die pad and Young’s modulus of die pad are analyzed. Accordingly, the Taguchi Method is applied to obtain the optimal parameter combination to improve the reliability of the stacked die QFN package.
The single-factor analysis shows that the solder fatigue life increases along with the reduction of the amplitude of temperature cycling range, die size, thickness of PCB, CTE of die pad, CTE of PCB as well as the increase of CTE of mold compound, Thus other factors have no significant effects on the solder paste fatigue reliability.
Finally, the optimal design derived from the Taguchi Method results in the fatigue life of 8124 cycles which shows a 4.21 times increase compared to 1926 cycles of the original design. Therefore the reliability of the stacked die QFN module package has been efficiently improved.
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