Process-n-Flip-Chips

The flip-chip process removes the integrated circuit from plastic carriers and mounts it upside-down on a substrate. The chips (or “dice”) are attached using solder bumps or conductive adhesives. However, high temperatures associated with solder operations can damage sensitive, exposed circuits. Thermally-induced stresses and rigid mounting can lead to joint fatigue and fracture in solder-based flip-chip attachment. Reliable, thermally-stable non-conductive adhesives can act dually as an underfill and to maintain contact pressure between the die and PCB, thereby insuring stress-free contact in the event of TCE mismatches.

Gold-on-Gold flip-chip processing from Valtronic USA, Inc., Solon, OH, relies on a low-impedance, direct metal-to-metal contact between die and PCB pads. Virtually zero lead length in flip-chip packaging, greatly reduces the resistive, inductive and capacitive effects of traditional wire lead systems, resulting in greater bandwidth and power efficiency. No special pre-metallization of chip contacts is required, as the contact system uses gold stud bumps that can be deposited on the contact pads of ordinary chips individually, in wafer packs, or before the chips are sawed from the wafer. Thus the process is workable and cost-effective for prototyping and small to large manufacturing runs.

Other electronic assembly and miniaturization methods can be combined with Gold-on-Gold flip chip processes. Chip-on-chip design places two ICs, one on top of the other using Chip-on-board methods, allowing a more compact 3D assembly. When combined with flexible PC boards, flip-chip circuits can fold into extremely dense electronic modules to achieve the smallest possible assemblies.

These miniaturization methods provide smaller (spacial) volume for hearing aids and other ultra-miniature electrical devices.

—SG

For more information:

Circle 155—Valtronic, or connect directly to their website via the Online Reader Service Program at www.RSLeads.com/?112df-155