Rapid Tooling for High Reliability Transfer Molded Devices

In the field of microelectronics encapsulation transfer molding is the process of choice for high volume and high reliability encapsulation of microelectronics devices. The materials used for transfer molding are highly filled epoxy based systems, with typically good CTE matching to encapsulated components and high media and temperature resistance. Especially harsh environment applications as automotive, industrial or outdoor communication electronics can benefit from the intrinsic advantages of this technology. For the development of such transfer molding processes it is necessary to design and manufacture a precision mold tool, adapt it to the transfer molding system, set up the process parameters and eventually modify the mold tool to yield improved results, e.g. by a variation of the flow fronts. These processes are not only time consuming but also costly, as high precision tooling is needed. To shorten process development times or to allow a larger variation of geometrical variations a rapid tooling process would be helpful. Within the project PowerSmart such a rapid tooling process has been developed using a 3D micromachining system and selected aluminum alloy as tool material. This rapid tooling process was used to manufacture a system in package that has been developed within PowerSmart. This SiP integrates a flip chip and various SMD components; package form factor was a quad flat non leaded [QFN] package, so an area molding process with subsequent singulation by sawing was used. Within the paper the development of a prototyping technology is described and demonstrated with the development of an adapted SiP packaging technology - this is done from concept development and material selection to manufacturing process development