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Wire Bond vs Flip Chip: 7 Differences

  • The choice between wire bond vs flip-chip in semiconductor packaging is not black or white. Engineers must consider cost, performance and end-application.
  • Wire bonding is the cheapest and most established semiconductor packaging method, used for 90% of IC´s in the world.
  • Flip-chip offers shorter interconnection lengths and allows vertical stacking of chips, but the manufacturing process is more complex.

Flip chip

Wire bond

Higher i/o density, resulting in smaller, more compact chip packages. Results in higher data transfer rates and bandwidth.

Lower i/o density, requiring larger chip package sizes. Lower data transfer rates, bandwidth and ability to process multiple data streams.

Shorter interconnection lengths, resulting in improved electrical performance. Flip-chip results in lower parasitics (resistance, inductance and capacitance)

Longer and thinner interconnection lengths due to wires, resulting in poorer electrical performance. Higher parasitics.

Better heat dissipation, reducing the risk of overheating.

Poorer heat dissipation due to limited surface area for heat transfer.

Smaller chip packages allow size reduction in electronic devices. Vertical stacking and 3D IC integration are possible.

Wires between the chip and the bond pad can be lengthy, creating a larger chip footprint. Vertical stacking of ICs is complicated.

Design is more complex due to higher interconnection density. It requires precise alignment of pitch pads and solder bumps.

Simpler design due to fewer i/o connections and less precision needed when attaching the wires to the bond pads.

Cost comparisons are case-specific, but at high volume and manufacturing yields flip-chip can be more cost effective. Lower die area allows to fit more dies per wafer, reducing unitary cost.

For non cutting-edge applications wire bonding is probably the most cost-effective packaging solution. 

Can be used for advanced process nodes like 7nm or 5nm.

Used for more mature process nodes, like 28nm or 14nm.

Wire Bond: Cheap and Reliable Semiconductor Packaging

Wire bond is a semiconductor packaging process that uses thin wires made of gold, aluminium or copper to make interconnections between the bonding pads of an integrated circuit and the pads of a chip package or substrate. It is a proven semiconductor packaging technology that is more cost-effective than other alternative methods. However, for advanced applications it has been replaced by other alternatives technologies which offer higher density interconnections and occupy less space, such as flip-chip or thermo-compression bonding.

There are two main types of wire bonding: ball bonding and wedge bonding.

Ball bonding: this process normally uses gold. A small ball or sphere is formed at the end of the write and attached to the bond pad using heat and pressure. The other end of the wire is connected to the chip package using ultrasonic energy.

Wedge bonding: this process normally uses aluminium. The wire is threaded through a capillary and then it is pressed against the bond pad. It does not need a ball at the end of the wire like ball bonding, and can be done at room temperature.

Flip-Chip: Enabler of Smaller Packages

Flip-chip uses solder bumps instead of wire bonds to connect the IC to the substrate. In the final semiconductor packaging step, tiny solder bumps are deposited on the chip pads. These bumps will serve as the interconnection between the chip and the substrate. The chip is then flipped upside down (hence the name flip-chip) and its active side with the bumps faces downwards. The flipped chip is aligned with the complementary pads on the substrate. Both parts are then attached and soldered until they melt, making the dense interconnection.

One of the main advantages of flip-chip technology is that it allows dies to be stacked on top of each other. With wire bonded chips this is more challenging due to the wires, whereas flip-chip can create dense interconnections in a smaller area.

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