3 Flip Ship on Lead Package Introduction

Flip chip assembly is the direct electrical connection of face-down (hence, flipped) electronic components onto substrates, circuit boards, or other components, by means of conductive bumps on the chip bond pads. While in contrast, bonding wire uses face-up chips with an individual wire connected to each bond pad. Figure 3-1 is a conceptual view of a flip chip and substrate.

Figure 3-1 Simplified Structure of Flip Chip on Lead Package

The continuing boom in flip chip packaging results from flip chip’s advantages in size, performance, flexibility, reliability, and cost over other microelectronic assembly methods:

1. Smallest Size – Eliminating bond wires and cumbersome individual packages reduces the required board area per chip by up to 95% and the height by more than 50%. Weight can be less than 5% of the packaged device weight. Flip chip is the simplest minimal package, smallest because it is very close to chip size.
2. Highest Performance – Because of its small size, flip chip offers the highest speed electrical performance of any assembly method. Eliminating bond wires reduces the delaying inductance and capacitance of the connection by a factor of 10, and shortens the signal path by a factor of 25 to 100. The result is high speed off-chip interconnection.
3. Greatest Connection Flexibility – Flip chip gives the greatest input/output connection flexibility. Wire bond connections are limited to the perimeter of the die, driving die sizes up as the number of connections increases. Flip chip connections can use the whole area of the die, accommodating many more connections on a smaller die, and placing them most efficiently. Area connections also allow 3-D stacking of die and other components.
4. Most Rugged – Flip chip is mechanically the most rugged interconnection method. Flip chips, when completed with an adhesive underfill, are solid little blocks of cured epoxy. They have survived laboratory tests simulating the forces of rocket liftoff and of artillery firing, as well as millions of cumulative total hours of actual use in computers and under automobile hoods.
5. Lowest Cost – Flip chip can be the lowest cost interconnection for high volume automated production, with costs of a fraction of a cent per connection. This explains flip chip’s longevity in the cost-conscious automotive world, and growing popularity in smart cards, RFID cards, cellular telephones, and other cost-dominated applications.