Eutectic Bonding - What Does It Prevent?
Catastrophic Optical Damage (COD): damage to the mirror coating reflects energy back in to the laser and overheats over time
Reduced Device Longevity: poor thermal interface will require higher current input for desired light output
"Noise" Feedback: adhesive bonds provide noisy feedback at data rates > 40 Gps
Eutectic definition: Easily Melted
*Point "E" is the mixture point where heating the solder results in pure solid to pure liquid transition
How to Join with Solder: 2 Things Needed
HEAT and WETTING
1) Need sufficient heat to melt and reflow the solder
2) Don't want excessive heat that will damage the components OR the surrounding components
Wetting Vs. Non-Wetting
Solder droplet contact angle "0" affects wetting
It's important to keep in mind some of the process variables with Eutectic Bonding. Palomar Technologies' eutectic process can control the following:
Temperature, Time, Force Scrub, Gas Environment
Other variables, not controlled with Palomar's process:
Die material, Solder Material, Solder Size, Solder Presentation Method, Substrate/Bond Pad Material, Cleaning Methods
This is a large subject matter, so for the sake of time and space, I will be posting several additional blogs further explaining the eutectic bonding process. I will be covering Temperature Effects, How to Control Temperature (with Pulse Heat Profiling), Force Scrub Attach, Using Scrub for AuSn Solder and benefits of Eutectic Scrub Attach.
For more information on Eutectic Die Attach, download Automated Eutectic Die Attach article: