Flip Chip TechnologyLane Ryan

Packaging Options

This presentation is going to focus on the advantages of the flip-chip method compared to wire bonding.

Manufacturing Process

• IC’s created on the wafer• Solder bumps are deposited on

metalized pads on the chip surface• Chips are then flipped so that the

solder bumps are touching the external circuitry

• Solder bumps are bonded to the connectors

• Insulating adhesive (underfill) is injected in the small space between the chip and the underlying mounting.

• Advantages– Increased signal speed– Reduced inductance (compared to wire

bonding)– Better thermal performance (in some cases)– Miniaturization

• Disadvantages– Difficult to troubleshoot– Difficult to remove or manually install– Mechanical issues

Flip Chip Advantages/Disadvantages

Comparison

• Wire-bonding interconnection inside the ADF7020 chip packaging vs. flip chip [1]

R1 L1 C L2 R2

Wire Bonding

0.057 Ω 1.28 nH 35.8 fF 1.28 nH 0.057 Ω

Flip Chip

0.001 Ω 8.33 pH 5.9 fF 8.33 pH 0.001 Ω

Comparison

[2] Total Insertion Loss

Noise Figure Output Power

Wire bonded -3.9 dB 9.0 dB 8.1 dBm

Flip chip -0.20 dB 5.4 dB 11.8 dBm

Underfill

• Technology is driving smaller bump pitch, bump diameter, and gap height. This creates challenges for injecting the underfill. [3]

• Small spaces affect the flow of the underfill material.• Maximum underfill particle size should be less than

one third of the gap height between the chip and substrate. This plays an important role in CTE.

• Underfill is used to reduce the impact of global mismatch in thermal expansion.

• Lower CTE underfill can decrease solder fatigue considerably.

References

• [1] L. Zheng, K. Rodgers, A. Mathewson, and B. O’Flynn, “A simulation-based design method to transfer surface mount RF system to flip-chip die implementation,” Electronic System-Integration Technology Conference, Berlin, Germany, pp. 1-5, Sept. 2010

• [2] G. Baumann, D. Ferling, and H. Richter, “Comparison of flip chip and wire bond interconnections and the technology evaluation on 51 GHz transceiver modules,” 26th European Microwave Conference, Prague, Czech Republic, pp. 98-100, Sept. 1996

• [3] T. Chen, J. Wang, and D. Lu, “Emerging Challenges of Underfill for Flip Chip Application,” Electronic Components and Technology Conference, pp. 175-179 Vol. 1, June 2004

Questions?