Experiment and numerical analysis for edge and corner bonded PoP bottom package assemblies under four-point bending

• Published in: Microelectronics and reliability Vol. 51; no. 9-11; pp. 1850 - 1855
• Main Authors: Shi, Hongbin, Che, Faxing, Ueda, Toshitsugu
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2011; Elsevier
• Subjects: Adhesive bonding; Applied sciences; Bend tests; Bonding; Corners; Design. Technologies. Operation analysis. Testing; Displacement; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; Failure; Integrated circuits; Packages; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Testing, measurement, noise and reliability; Performance evaluation; Printed circuit board; Numerical method; Failures; BGA technology; Finite element method; Integrated circuit bonding; Hardening; Four point probe; Ultraviolet radiation; Failure analysis; Electronic packaging; Soldered joint; Printed circuit; Damaging; Bending test
• ISSN: 0026-2714; 1872-941X
• DOI: 10.1016/j.microrel.2011.07.087

This paper presents the four-point bend test results for edge and corner bonded 0.5mm pitch lead-free package stackable very thin fine pitch ball grid arrays (PSvfBGAs) as package-on-package (PoP) bottom packages on a standard IPC/JEDEC bend test board. The tests were carried out based on the above standard with a 30mm loading span, 90mm support span and 7.5mm/s crosshead speed. The daisy chain resistance, strain, crosshead displacement and load of each PSvfBGA were measured and a 20% increase in the resistance was used as the failure criterion. Materials used in this study were a UV-cured acrylic edge bond adhesive, a thermal-cured epoxy edge bond adhesive and a thermal-cured epoxy corner bond adhesive. The test results show that all of them can improve the bend performance significantly; especially the edge bond high module epoxy increased the crosshead displacement, strain and bending force when mechanical damage occurred by 33.46%, 26.74% and 3.05% respectively. Failure analysis indicated that the predominant failure site was PCB pad lift/cratering regardless of with or without adhesives. The 3D quarter finite element model was also built to further study the improvement mechanism of bend performance by these adhesives.