电子封装中超声波线焊的三维/二维非线性有限元分析

3D/2D Nonlinear Finite Element Analysis of Ultrasonic Wire Bonding in Electronic Package

用三维和二维的有限元方法对超声波线焊进行了模拟,其间考虑了材料非线性、几何非线性和接触边界非线性的影响。实验显示,金线和焊接平台的接触界面为长椭圆形状,其中焊接部位发生在接触界面的周边。有限元模拟的结果显示,最大的接触压力以及由此导致的最大摩擦能密度也发生在接触界面的周边,从而解释了实验现象。分析了各工作参数对超声波线焊产生的影响。结果表明,并不是压碶按压力越高,接触压力就越大,这意味着提高压碶按压力不一定能提高焊接的可能性,有限元分析有助于确定合适的压碶按压力。

The ultrasonic wire bonding process was simulated by 3D and 2D finite element method. The non--linearity in geometry, material properties and contact boundary was considered in analysis. It shows in experiments that the contact area between the wire and the pad has possesses long elliptical shape, and the welded area was periphery of the contact area. The FEM analyses indicate that maximum contact pressure and maximum friction energy intensity caused by ultrasound also occurs always at the periphery of contact area, which explain the weld formation in experiments. Another focus was on how the operating parameters affect the ultrasonic wire bonding. It shows in analysis that the higher bond force does not mean higher contact pressure, and elevating the bond force is not always useful for the bondability, and FEM analysis can be used to determine the appropriate bond force.