多层印制板的凹蚀与负凹蚀

Etchback and Negative Etchback in MLB

多层板孔金属化包括去钻污处理和化学沉铜,去钻污过程是对孔壁非导电材料的蚀刻,而沉铜前处理中的微蚀是对内层导电铜箔的蚀刻,当前者的量大于后者时为凹蚀,当后者大于前者时为负凹蚀。本文通过对凹蚀与负凹蚀的形成过程进行分析,提供了两种蚀刻量的测定方法,对航天标准、国军标以及IPC标准中关于凹蚀与负凹蚀的规定进行对比,阐述了如何控制凹蚀与负凹蚀的深度,防止产生过度的凹蚀与负凹蚀,从而保证孔金属化的质量。

PTH of MLB includes desmear and electroless copper. Desmear is for etching the insulated material in the hole,but electroless copper is for etching the copper of innerlayer. When the former is greater than the later, it is called etchback, otherwise it is called negative etchback.Through analyzing how etchback and negative etchback forms, this paper offers the testing methods about two etching speeds, carries through contrasts between QJ831A-98 and GJB362A-96 and IPC-600F about etchback and negative etchback,expatiates how to control the depth of MLB's etchback and negative etchback,so as to avoid excessive etchback or negative etchback and assure its PTH's quality.