A new process for assembling flip chips promises to reduce warpage, eliminate voids and cut cycle times by 50 percent.



Henkel Corp.’s electronics group (Irvine, CA) has developed a new process for assembling flip chips that promises to reduce warpage, eliminate voids and cut cycle times by 50 percent.

Called accelerated cooling, the process is used in conjunction with two of the company’s underfill encapsulants, Hysol FP5000 and Hysol FP5001. These nonconductive pastes were developed to provide an alternative to traditional, mechanical soldering by bonding bumps to the substrate through a thermal compression process. This simplifies flip chip assembly by eliminating the need for flux application, reflow and cleaning, in most cases.

Now, the effectiveness of these materials has been enhanced with the introduction of the new accelerated cooling flip-chip assembly process. The introduction is timely, since packaging companies are beginning to migrate away from face-up, wire-bonded applications to flip-chip processes in order to gain footprint and performance efficiencies.

In a conventional thermal compression process, the nonconductive paste is applied to the substrate, and then the device is heated and compressed. In the accelerated cooling process, the device is heated while it is secured by the flip-chip bonder head. It is then rapidly cooled during compression onto the paste-coated substrate. This rapid cooling process allows the assembly to be completed before the device can be exposed to excessive heat. This reduces package warpage, decreases moisture-related voids, and lowers cycle times. Whereas a typical thermal compression process-including alignment of the integrated circuit-can take as long as 13 seconds, the accelerated cooling process is completed in 7 seconds, a savings of nearly 50 percent.

“We are very excited about this advancement in flip-chip assembly,” says Robert Chu, Henkel’s global product manager for chip-scale packaging underfills. “This is arguably one of the most significant developments in packaging technology in recent years and we fully expect the AC process to facilitate rapid adoption of flip-chip assembly, enabling increased signal transfer rates and higher assembly densities. It is truly a breakthrough.”

For more information, call 949-789-2500 or visit www.henkelelectronics.com.