材料期刊网

很久以前就有用于印制线路板通孔壁镀覆金属的工艺,现在这些工艺开始采用所谓的"直接电镀"方法以取代早先昂贵而又复杂的金属化学镀.由于金属可以桥接塑料件与挂具接触的距离,所以在塑料上的电镀就更加困难.其中存在许多不同的可能性能提供足够的导电性而间隔微小的距离.人们进行了多种尝试,金属硫化物体系至今仍然在使用,该体系有不少缺点,如工艺步骤过长、挂具绝缘.有一项发明采用含铜离子的碱性溶液浸渍处理,将沉积了胶体钯颗粒的表面转变为导电层,这项发明已获得了市场应用而且对于铸模ABS塑料镀覆金属效果不错.这项以 "Futuron"命名的工艺,由与胶体钯共沉积的亚锡将铜还原,铜填充于胶体颗粒间的空隙.所形成的导电层其化学稳定性足以抵御酸铜镀液中的硫酸,因而可适用任何一种酸铜镀液.Futuron工艺节省时间,有利于环境保护;而且因操作容易,电镀车间整体废品率下降.

Processes which were used to plate metal on the walls of drilled holes in printed circuit boards long time ago have started to make use of so called' direct electroplating' in order to get rid of expensive and complicated electroless metal deposition. There are a lot of different possibilities existing meanwhile to provide with sufficient conductivity to gap the small distances. Direct plating on plastic parts is much more difficult because the metal has to bridge the distance between the contacts of the plating rack. There were many attempts and even today metal sulphide-based systems are used. But they have lots of disadvantages like a long process with many steps, or plating of the rack insulation. An invention which converts surface-deposited colloidal palladium particles to a conductive layer using an alkaline copper ion containing post-dip is meanwhile in the market and works not too bad for the metal plating on moulded ABS plastic parts. This process, called Futuron, uses the stannous tin co-deposited together with the palladium colloid to reduce copper which then fills the gap between the colloidal particles. The chemical stability of the conductive layer resists the sulphuric acid in the copper electrolyte, and the layer therefore can electroplated from any acid copper electrolyte. The process saves some time, is environmentally very friendly, and because of its easy handling reduces the overall reject rate in plating shops.