Processing Equipment

Printed Wiring Boards. Electroless copper process equipment consists essentially of a juxtaposed series of tanks, typically 380 to 1135 L (100 to 300 gal) in size (or as high as 3800 L, or 1000 gal), including process chemistry tanks, rinse tanks, and load/unload stations, with all associated heaters, chillers, air spargers, and so on. The panels are transported vertically through the system in a rack that typically holds panels representing a surface area of 25 to 735 cm2/L (0.1 to 3 ft2/gal) of copper bath. (Other process tanks may be sized appropriately to most efficiently hold the rack.) An automatic hoist system is used, except in the smallest installations.

In the past, electroless lines were designed for two-sided boards only. The multilayer desmear process was entirely separate, thus requiring additional unracking and reracking between segments. Most electroless copper plating lines now being built include tanks for the desmear process as well.

Recently, considerable interest has developed in applying conveyorized horizontal processing to part, or all, of the electroless copper process, as there are a number of technical and operational benefits to this approach. At present, horizontal desmear is being used in select facilities worldwide, and several facilities are also successfully operating in production using horizontal equipment for electroless copper itself (Ref 69).

Plating-on-Plastic. Plating equipment for POP typically involves tank volumes of about 3800 L (1000 gal), but tanks of up to 26,500 L (7000 gal) have been used. The plating process in decorative POP is carried out in one of two modes: designated straight-through or semibulk. Straight-through processing is carried out in a continuous system, where the preplate, electroless, and electroplating steps are carried out with no interruption for reracking. In semibulk processing, two separate fixtures are used, one for the pretreatment/electroless steps and the other for electroplating. There are numerous advantages for each type of system (Ref 28). Advantages of straight-through processing are evident: only one piece of equipment, fewer processing steps, less handling, and so on. Semibulk processing, however, offers a number of advantages, including much higher capacity, more degrees of freedom in choosing racking systems and chemicals, and flexibility in processing sequences.

0 0

Post a comment