Flip-Chip
Flip-chip assembly is an upcoming technology used in different applications for bare die packaging.
Cross-section through a chip mounted in MID hollow with NCA flip-chip
In this method, the chip is flipped over, and the chip pads are electrically connected directly to the feed lines below.
Different assembly processes with solder and electrically conductive and non-conductive adhesives were developed for a wide range of applications.
HARTING has qualified a NCA (non-conductive adhesive) flip-chip process on the MID substrates.
The chip pads here are provided with so-called Au stud bumps, which are created with an Au wire bonder.
Si chip with Au stud-bumps on connection pads
In the assembly process, these Au stud bumps are pressed onto the MID conductive lines through the adhesive, which was already applied, and then the adhesive is hardened in 10 - 20 seconds, using pressure and heat.
The adhesive shrinkage guarantees a reliable electric contact and mechanical fixation.
One large advantage of this process is therefore that electrical contacting, mechanical fixation and protection of the chip surface and electrical connections take place in one step.