薄型IC封装基板翘曲分析与设计优化

Design parameters optimization for thin IC package substrate warpage

两层布线薄型倒装封装基板易受材料及结构设计失衡影响而出现翘曲超标问题。分别采用板壳模型对称性计算与有限元分析,对基板布线层残铜率差与阻焊层开窗率差介于5%~15%的非平衡设计进行了优化,确定了最优结构参数用于基板制作。按板壳模型优化的顶阻焊厚度试制了基板,实测翘曲满足通行验收标准(<1. 25 mm)。板壳模型分析与有限元模拟所得基板顶阻焊厚度优化值较为一致,偏差为1μm左右。主效应分析显示,基板翘曲对阻焊层开窗率的平衡性更为敏感。采用板壳模型优化基板翘曲的方法计算简便、准确性良好,对于改善封装基板加工过程中的翘曲问题具有良好的参考价值。

The warpage of thin flip-chip package substrate is sensitive to the unbalanced material and structure design.Substrates with Cu remaining and solder mask opening difference between 5%and 15%were analyzed by the lamination theory and FEM,respectively.The optimal thickness of the substrate top solder mask was calculated.The warpage of the trial substrate with optimized structure by the lamination theory meets the general acceptance criteria(<1.25 mm).The optimized structure design by the lamination theory matches well with that by FEM with a deviation about 1μm.From the main effect analysis,the warpage of the substrate is more sensitive to the balance of the solder mask opening.The lamination theory provides a quite simple method to optimize substrate design with enough precise,which is significant for substrate warpage optimization during the manufacture.