Forming of Micro Channels with Ultra Thin Metal Foils

The objective of this paper is to investigate the feasibility of producing micro scale structures by forming ultra thin metal foils. During this investigation, flat rolled foils of AISI 304 stainless steel (2.5μm in thickness) and pure copper (3.0μm in thickness) were formed into channels of varying shapes. The shapes of these channels were straight lines, concentric circles, crosses, and other curved shapes. The cross sections of the channels ranged from 10∼20μm wide and 5-10μm deep. Forming was done by cold isostatic pressing. Two types of micro dies were used. One was made of SU-8 photo resist on a Si wafer, the other of dry etched (DRIE) Si wafer. The die and metal foil were vacuum packed in a bag made of multilayered film. The forming was conducted with a 240MPa cold hydrostatic press. The formed structures were examined in terms of their dimensions, surface qualities, and potential for defect. The fabrication results show that the sheet metal forming process can be applied to the manufacturing of micro scale structures.