The Impact of AuSn Preforms Thickness on Solder Joint Reliability

Abstract A hurdle that prevents widespread use of semiconductor lasers is that their performance is negatively impacted by thermal management. New products like stack layer diodes have a large number of lasers that work all at once in the condense area. When semiconductor laser dies' operational heat increases, the power of the laser decreases. A technique that is helping users overcome this hurdle is the application of a thinner 80Au20Sn solder joint for the die-attach to aid in thermal transfer to copper heat sinks. The paper looks at a variety of different preform thicknesses, ranging from 0.0002″ to 0.0015″, and it also reviews voiding percentages. Our study tested shear strength and looked at how preform thickness impacts joint integrity. Further, we took a more in-depth look at the intermetallic thickness on ultra-thin preforms and observed how it affected the solder joint strength. Finally, we looked at other factors like surface tension and at what thickness preform this starts to impact voiding and performance. The paper will help engineers gain insight into what preform thickness will be the optimal choice for laser diode applications as well as other die-attach applications.