从IC封装产品可靠性谈封装冲切模具优化设计

随着电子产品市场日益升温,电子产品朝超薄、超小等方向发展,产品量的需求越来越大,产品可靠性越来越高,塑料封装模具的冲切工艺产生的分层现象是影响产品可靠性的主要原因之一。文章首先叙述了冲切过程产生的分层情况,其次从模具结构方面说明冲切产生分层的原因,并针对产生分层的原因提出冲切模具的优化设计,最后总结从实际生产过程中防分层要求设计冲切模具和框架,可避免在实际生产过程中IC胶体分层导致产品可靠性问题。

Upper bound solution of supporting pressure for a shallow square tunnel based on the Hoek-Brown failure criterion

To analyze the stability of a shallow square tunnel, a new curved failure mechanism, representing the mechanical characteristics and collapsing form of this type of tunnel, is constructed. Based on the upper bound theorem of limit analysis and the Hoek-Brown nonlinear failure criterion, the supporting pressure derived from the virtual work rate equation is regarded as an objective function to achieve optimal calculation. By employing variational calculation to optimize the objective function, an upper bound solution for the supporting pressure and the collapsing block shape of a shallow square tunnel are obtained. To evaluate the validity of the failure mechanism proposed in this paper, the solutions computed by the curved failure mechanism are compared with the results calculated by the linear multiple blocks failure mechanism when the Hoek-Brown nonlinear failure criterion is converted into the Mohr-Coulomb linear criterion. The influences of rock mass parameters on the supporting pressure and collapsing block shape are discussed.