气密性陶瓷封装内热应力的ANSYS分析

采用有限元方法,运用ANSYS软件,分析计算了气密性陶瓷封装管壳内温度及热应力分布,比较了4种粘接剂对芯片温度及热应力分布的影响。热分析表明,芯片中心处温度最高,边角处最低;不同粘接剂都因为厚度较薄,对芯片温度的分布无较大影响。热应力分析表明,由于热分布不均匀,使芯片与粘接剂的接触处有较大的热应力,主要集中在粘接剂与芯片的下底面,此处也是最容易导致芯片脱落失效的部分。对比4种粘接剂的结果发现:采用H35作粘接剂时,应力峰值为17.0MPa,但芯片与粘接剂和底座之间的热应力较大;采用PbSnAg焊料作粘接剂时,应力峰值为41.9MPa,但芯片与粘接剂和底座之间的热应力较小。

ANSYS Analysis of Thermal Stress in Air-Tight Ceramic Packages

Using finite element method,temperature and thermal stress distribution in air-tight ceramic packages were analyzed with ANSYS software.Effects of four types of solders on die temperature and thermal stress distribution were compared.Thermal analysis showed that the highest temperature was concentrated at die center,while the lowest temperature was distributed at die edge,and four solders had no great effect on chip temperature distribution.Thermal stress analysis indicated big thermal stress between die and solders due to uneven temperature distribution.Thermal stress was mainly concentrated between solders and chip bottom,which is the most likely cause for chip fall-off failure.The comparison of four solders showed that the maximum thermal stress was 17.0 MPa when H35 solder was used for die-attachment,which resulted in a larger thermal stress between chip and base,and when PbSnAg solder was used as solder,the maximum stress was 41.9 MPa,which resulted in a smaller thermal stress between chip and base.