Flipchip

Flip-chip, or flip chip, is a semiconductor packaging technique in which an integrated circuit die is mounted face-down on a package substrate and interconnected by solder bumps or microbumps that form direct electrical connections to the substrate pads. By flipping the die, the active circuitry is positioned close to the substrate, enabling short interconnect paths and higher I/O density.

In a typical flip-chip assembly, solder bumps or redistribution layer connections are formed on the die pads. The die is then flipped so its pads align with matching pads on the package substrate or printed circuit board, and the assembly is reflow soldered. After bonding, underfill epoxy is often dispensed between the die and substrate to improve mechanical reliability and thermal performance. Variants and terminology include FC-BGA (flip-chip ball grid array), FC-LGA (landing grid array), and FC-PGA (flip-chip pin grid array).

Advantages of flip-chip packaging include reduced interconnect length and inductance, enabling higher speed and bandwidth for high I/O densities. The approach also supports better thermal dissipation since heat can be conducted more directly from the die to the substrate, and it accommodates finer interconnect pitches in compact form factors.

Disadvantages encompass higher manufacturing complexity and cost, greater challenges in rework and testing, and stress from mismatched coefficients of thermal expansion between die and substrate that can affect solder joints. Reliability depends on careful process control, robust underfill, and proper material selection.

Applications are common in high-performance processors and graphics devices, memory modules, and specialized ASICs and sensors, where high I/O density, electrical performance, and thermal management are critical.