TABLE OF CONTENTS Metal packages are almost always a sealed enclosure type that is classified as fully hermetic. The cavity can be formed by machining a billet or block of metal using traditional metal shop procedures like milling, drilling, and grinding. These classical methods are time-consuming and require high skill levels, but they produce precise custom parts with almost no tooling. This method is ideal for prototyping but is used for production, especially for optoelectronic modules, and military RF modules in limited volume. The relatively higher cost makes it a less desirable process for MEMS. Material manufacture and packaging fabrication are two separate processing steps: (1) the fabrication of the material in a billet or sheet and (2) machining of the billet into the desired shape. For all but the simplest shapes, the cost associated with packages fabricated in this manner are associated with the machining to the desired geometry and the billet stock, most of which is lost to machining. Often these packages require additional assembly operations to add functional components such as seal rings, feed-through ports, and substrates that add to the total packaging cost.
Metal injection molding (MIM), also called powder injection molding (PIM), is also being applied to manufacturing electronics parts. MIM can produce 3D solid metal parts, including cavities, and is the metal analog to plastic injection molding. MIM is capable of producing an almost limitless array of highly complex geometries in many different alloys ranging from stainless steels,...
