Abstract
Wire ball open failure at the interface of the gold wire and bonding pad of a multi-stack package (MSP) under high temperature storage (HTS) condition of 150 °C is studied. Failure analysis using FIB-SEM was conducted by in-plane moiré interferometry and FEA to clarify the failure mechanism. The ball open failure due to Kirkendall void that results from metal diffusion at high temperature was accelerated by the tensile stress imposed at the gold wire. The tensile stress developed at the gold wire when packages showing different warpage behaviours were stacked. Mechanical interaction between top and bottom packages caused unstable warpage, readily twisted and saddled. The wire came in contact with the photo-sensitive solder resist (PSR) dam because of the unstable warpage and this contact resulted in tensile stress at the gold wires. Solder flux residues reacted with the encapsulant, and as a result, the encapsulant of the top package adhered to the chip of the bottom package, and this adherence created additional tensile stress at the gold wires. To reduce the tensile stress at the wires, the PSR dam was removed, loop shape was altered from 45° to 90°, water soluble flux was applied, and cleaning process was added. HTS reliability was significantly improved and guaranteed after reducing the tensile stress at the wires.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
