Wire Bonding vs Flip Chip: Chip Interconnect Compared
These are the two main ways to connect a chip to its package. In wire bonding, the chip sits face up and thin metal wires join its edge pads to the package. In flip chip, the chip is turned face down and solder or copper bumps on its surface connect directly to the substrate. Wire bonding is cheap and flexible; flip chip allows many more connections, shorter paths and better electrical performance.
| Aspect | Wire bonding | Flip chip |
|---|---|---|
| Connection | Thin wires (gold, copper or aluminum, roughly 15 to 50 µm) welded from chip pads to the package | Bumps of solder or copper on the chip surface joined directly to the substrate |
| Chip orientation | Face up | Face down |
| I/O location and count | Pads on the chip edge only; hundreds up to about a thousand connections | Bumps across the whole surface (area array); thousands of connections |
| Electrical performance | Long wires add inductance and resistance, limiting speed and power delivery | Short paths give low inductance and better signal and power integrity |
| Thermal path | Heat leaves mainly through the back of the chip into the die attach | The back of the chip can touch a heat spreader or heat sink directly |
| Process | Each wire is bonded one after another, which is slower | All bumps are joined at once by reflow, and underfill resin is added to relieve stress |
| Package size | Larger: space is needed around the chip for the wires | Smaller |
| Cost | Low: mature, flexible and needs no bumping of the chip | Higher: bumping, a finer substrate and underfill are needed |
| Typical uses | Memories, microcontrollers, analog chips, LEDs and low-cost products | CPUs, GPUs, SoCs and other high-speed, high-pin-count chips |
Figures are typical orders of magnitude and vary by process generation and product.