ADVANCED PACKAGING : Flip-Chip

A chip packaging technique in which the active area of the chip is "flipped over" facing downward. Instead of facing up and bonded to the package leads with wires from the outside edges of the chip, any surface area of the flip chip can be used for interconnection, which is typically done through metal bumps. These "bumps" are soldered onto the package and underfilled with epoxy. The flip chip allows for a large number of interconnects with shorter distances than wire, which greatly reduces inductance.

• Metal bumps can be made of
– solder (tin, or tin-lead or lead-free
alloys)
– copper
– gold
– Copper-tin or gold-tin alloys

• Package substrates are
– Epoxy-based (organic substrates)
– Ceramic based
– Copper based (leadframe substrates)
– Silicon or glass based

For a more comprehensive report on Flip Chip refer this report  i-micronews Flip-Chip Report.