High density packaging for automotive applications

In order to match high power density and large counts of I/Os with the need for smaller-sized automotive electronic devices and low cost, new solutions have to be developed without any concessions to reliability. The authors describe the so-called i²Board concept, developed by Schweizer Electronic AG and used in the VISA project, funded by the German Government. VISA is an abbreviation and means "fully integrated power electronic systems for automotive electronics" [1]. A micro processor with 231 very dense interconnects and high power dissipation is embedded into a demo transmission control unit (TCU) from Continental. First the die is mounted on an organic interposer which also acts as fan-out for the I/Os. Then the component is embedded into the final board and the interconnection with the complete circuit is formed by a combination of via laser drilling and metallisation steps. No special steps except those of standard PCB processing are necessary. However, very precise manufacturing has to be assured. This way, high density packaging and very short signal paths are enabled. Three interconnecting technologies (Cu pillars, solder balls, and Au stud bumps) are discussed with respect to their applicability for high precision chip mounting. Further technological details like the choice of suitable materials are outlined.