What is a Flip Chip?
A flip chip" is a type of integrated circuit which has the leads and connections on the surface of the chip. Traditionally the connecting leads or bond wire protrude on the sides of the device, outside of the body of the chip itself. Flip chip connections are shorter, and may be made anywhere on the surface of the chip.
One surface of the flip chip has metallic connectors, usually solder bumps, and it is turned over and attached face down on a substrate. The substrate usually has a corresponding pattern of small bumps of solder or "flip chip bumps" on it, although attachment technology is evolving. The flip chips are bonded to substrate by running an epoxy encapsulant between the flip chip and the substrate with wafer bumps.
A flip chip possesses a shorter interconnect distance with the solder bumps as compared to the wire bonds or leads around the side of a traditional integrated circuit. Under the basic laws of electricity these shorter leads then can deliver lower inductance, resistance, and capacitance - and consume less power - yet are capable of delivering the signal integrity necessary for high performance systems.
Due to this design the input/output (I/O) from the flip chip device is not limited by the leads along the perimeter of a traditionally configured integrated circuit, allowing higher l/O density- i.e., more signal, power, less distortion, in less space. Flip chips can be 95% smaller than a traditional chip - a real important item for designers of future microprocessors and Application Specific Integrated Circuits (ASIC's).
In a nutshell, flip chips allow designers of electronic equipment to deliver more: (1) performance, (2) reliability, and (3) durability, yet in less space.
Flip Chip Advantages
The advantages in using flip chips versus other types of integrated circuits are summarized at the FCT Website :
-A smaller I/C footprint: flip chips allow tighter spacing, as devices are smaller and pick-and-place manufacturing equipment requires smaller keep-out areas;
-Reduced size and weight: flip chips are 95% smaller than an ordinary quad flat pack, giving designers many more design options;
-Increased functionality: flip chips have increased input/output, useful for microprocessors, telecommunications, and automotive electronics;
-Improved reliability: Epoxy underfill in large flip chips results in up to 10 times the reliability of a packaged device, and may also reduce the connections;
-Improved yields: Assembly yields for flip chips have lower deflect ranges per input/output than typical integrated circuits;
-Improved performance: Flip chips interconnects deliver superior electrical properties;
-Improved thermal capabilities: Since flip chips are not encapsulated, the system manufacturer can take full advantage of the silicon's thermal properties;
-Reduced capital investment: Flip chip technology eliminates intermediate interconnect processes and device encapsulation processes.
by Douglas V. Fant
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