选择性有机可焊保护剂在印制电路板铜金表面选择性沉积机理

通过紫外分析有机可焊保护剂（OSP）膜厚、SEM形貌观察和EDS元素分析等方法研究了不同OSP工艺流程对印制电路板铜金选择性沉积的过程和机理。结果表明：取代苯并咪唑衍生物和1价铜化合物的OSP配合反应需要一定的活化能；2价铜离子、3价铁离子以及苯并咪唑小分子均可以降低该反应的活化能，具有正向催化作用，而锌离子不具备催化OSP反应的能力；利用铁离子的催化特性和不参与成膜的特点可以使OSP在铜、金之间形成选择性，利用苯并咪唑小分子不与金原子络合的特点也可以使OSP在铜、金之间形成选择性；配套预浸前处理的含锌离子OSP体系的选择性显著优于含铁离子OSP体系的选择性；OSP成膜反应不会改变铜表面和金表面的微观形貌。

Depositing mechanism of selective OSP on copper and gold surface of PCB board

In order to develop better Cu-Au selective OSP (organic solderability preservatives),the procedure and principle of depositing of several selective OSP on printed circuit board(PCB) were studied for the first time. The mechanism of OSP reaction and selective depositing were investigated with UV thickness measure,SEM morphology survey and EDS element-composing analysis. The results indicate that the complexation reaction between substituted benzimidazole derivatives and copper (Ⅰ) compound needs some activation energy. The copper (Ⅱ) ion,ferric (Ⅲ) ion and benzimidazole all can lower this activation energy and have positive catalytic effect,while the zinc (Ⅱ) ion has no such capacity. Employing the catalytic property and no participating in OSP film formation of the ferric ion can endow OSP the selectivity between copper and gold. And no complexation between benzimidazole and gold atom can also be used to make this kind of selectivity as well. The selective OSP containing zinc ion plus pre-treatment process is obviously better than the selective OSP containing ferric ion. The OSP film formation procedure does not change the surface morphology of copper and gold.