The recent development in the power electronics industry regarding power densification, power increase, and device miniaturization has affected the overall reliability of microelectronics devices. Reliability challenges occur from thermal and mechanical stress concerns which is concurrent with power densification. In order to effectively counter these concerns, nonconventional designs, and features that can mitigate thermomechanical strains that occur within devices and packages especially in critical regions. One of the main challenges hindering the densification of power systems arises from the reliability of the device due to thermomechanical stresses and strains at semiconducting devices and substrate interfaces which are typically enhanced in harsh environmental conditions such as in electric vehicle applications, where extreme temperatures are common. Gordon Moore, the co-founder of Intel, predicts a steady increase in the number of semiconductors on a miniaturized substrate. This would inevitably increase reliability concerns within power devices due to increased heat generation from the devices subsequently causing thermomechanical strain challenges. Consequently, this has caused a paradigm shift in interconnection methods and encouraged integrating strain management technologies in devices, therefore, eliminating conventional interconnection methods such as wire bonds as there are many demerits associated with using wire bonds. Flip-chip bonding methods were initially designed and integrated to improve the semiconductor device's reliability by changing the orientation of the geometry allowing for increased interconnect density whilst also offering better thermal management subsequently improving reliability. Newer approaches exist to further improve the reliability of higher power devices beyond the conventional flip-chip method by integrating enhanced structures in the orientation of the flip-chip method. This new technology includes compliant interconnect either by fabricating higher mechanical strength interconnecting balls such as metalized polymer spheres or by having compliant features support regular solder balls that give allowance for thermomechanical expansion.  These interconnects have a relatively close coefficient of thermal expansion to the commonly used FR4 printed circuit boards (PCBs) reducing the overall time to failure and rate of failure due to interfacial stress at the first interconnect level. Compliant interconnects are generically designed to comply with expansion that occurs thermomechanically within a device effectively allowing the device to withstand extreme conditions such as thermal cycling, thermal shocks, vibrations and curb possible device warpage. Complaint interconnects advantages are not fully utilized in industrial applications because of the difficulty of fabrication i: e many steps are needed in current fabrication approaches. We have developed an additive approach to fabrication that effectively reduces the number of steps required in the fabrication of interconnects. In this paper, we would be discussing this method and analyze the properties of additively manufactured interconnects. We have incorporated designs for mechanical enhancement of power devices at strategic locations and we would be discussing the results of a parametric experimental study involving reliability enhancing interconnects in comparison to conventional interconnects methods.


Additive Fabricated Compliant Interconnects: Design, Fabrication & Reliability Effects

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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