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首页> 外文期刊>IEEE transactions on electronics packaging manufacturing >Thermal deformations and stresses of flip-chip BGA packages with low- and high-T/sub g/ underfills
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Thermal deformations and stresses of flip-chip BGA packages with low- and high-T/sub g/ underfills

机译：具有低和高T / sub g /底部填充的倒装BGA封装的热变形和应力

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The purpose of this paper is to experimentally, numerically, and theoretically investigate the thermomechanical behaviors of flip-chip ball grid array (BGA) packages with low- and high-T/sub g/ underfills under thermal loads, after 85/spl deg/C/85%RH conditions, and after solder reflow. The low- and high-T/sub g/ underfills all cured at 150/spl deg/C are with glass transition temperatures (T/sub g/) at 84/spl deg/C and 142/spl deg/C, respectively. The emphasis of the study is placed on the deformations and die stresses of the packages under these loading conditions. This paper has presented that Suhir's solution of a trimaterial assembly and finite-element method (FEM) can effectively predict the thermomechanical behaviors of both flip-chip BGA packages. It is also found from Twyman-Green experiments that the stress-free temperature is at underfill-curing temperature (T/sub c/) for both packages before solder reflow, but not after solder reflow. Furthermore, the relation between curvature and temperature is nearly linear for packages with high-T/sub g/ underfills, while bilinear (with turning point near T/sub g/) for those with low-T/sub g/ underfills. It is also discovered that the packages with low-T/sub g/ underfills during cooling processes suffer stress relaxation, and, thus, their deformations depend on cooling rate, but not for those with high-T/sub g/ underfills. The die stresses can be directly determined by Suhir's die stress solution associated with the curvature data from the experiments. The coplanarity of the packages with and without fillets has also been addressed by the FEM analyses combined with experiments. It is found that the fillet effect on the warpage is negligible for this flip-chip BGA and the 2-D axis-symmetrical model can be approximately used for addressing the global warpage. Regarding 85/spl deg/C/85%RH environmental effect, it is shown that the packages with high-T/sub g/ underfills are insensitive to this environmental effect, while those with low-T/sub g/ underfills are minor sensitive (about 10% decrease). It is also found that solder reflow process does affect the curvature of the packages by increasing 18% and 15% of the average curvature for those with high- and low-T/sub g/ underfills, respectively.
机译：本文的目的是通过实验，数值和理论研究在温度为85 / spl deg /之后，低热和高T / sub g /底部填充的倒装芯片球栅阵列（BGA）封装的热力学行为。 C / 85％RH条件下，以及回流焊之后。全部在150 / spl deg / C下固化的低T / sub g /底部填充胶的玻璃化转变温度（T / sub g /）分别为84 / spl deg / C和142 / spl deg / C。研究的重点放在在这些载荷条件下包装的变形和模应力。本文介绍了Suhir的三材料组装和有限元方法（FEM）的解决方案可以有效地预测两种倒装芯片BGA封装的热机械行为。从Twyman-Green实验还发现，两种封装的无应力温度均在回流焊之前（但在回流焊之后）处于底部填充固化温度（T / sub c /）。此外，对于高T / sub g /底部填充的包装，曲率和温度之间的关系几乎是线性的，而对于低T / sub g /底部填充的包装，弯曲和温度的关系是双线性的（转折点接近T / sub g /）。还发现，在冷却过程中具有低T / sub g /底部填充量的包装会受到应力松弛的影响，因此，它们的变形取决于冷却速率，但对于高T / sub g /底部填充量的包装则不然。模具应力可以通过与实验中的曲率数据相关的Suhir模具应力解直接确定。带有和不带有圆角的包装的共面性也已通过有限元分析和实验相结合来解决。已经发现，对于这种倒装芯片BGA，翘曲的圆角效应可以忽略不计，并且二维轴对称模型可以近似地用于解决整体翘曲。关于85 / spl deg / C / 85％RH的环境影响，表明具有高T / sub g /底部填充量的包装对这种环境影响不敏感，而具有低T / sub g /底部填充量的包装对敏感度较小（减少约10％）。还发现，对于高T / sub g /低T / sub g /底部填充的焊料，回流焊工艺确实通过分别增加平均曲率的18％和15％来影响封装的曲率。

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