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Reliability testing and stress measurement of QFN packages encapsulated by an open-ended microwave curing system

: Adamietz, Raphael; Desmulliez, Marc P.Y.; Pavuluri, Sumanth Kumar; Tilford, Tim; Bailey, Chris; Schreier-Alt, Thomas; Warmuth, Jens

Preprint urn:nbn:de:0011-n-5127618 (2.7 MByte PDF)
MD5 Fingerprint: 20021df79c00f74fe3737ab7fb836c82
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Erstellt am: 9.10.2018

IEEE transactions on components, packaging and manufacturing technology 9 (2019), Nr.1, S.173-180
ISSN: 2156-3950
ISSN: 2156-3985
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IPA ()
Fraunhofer EAS ()
Aufbautechnik; Mikroelektronik; Mikrowelle; Zuverlässigkeit; Konvektionsofen; Belastungsprüfung; Verbindungstechnik; encapsulation; microwave curing; microelectronic packaging; reliability testing; open-ended oven; residual stress; accelerated stress test; convection oven

In this paper, the influence of microwave curing on the reliability of a representative electronic package is examined by reliability testing and measurement of residual stresses. A LM358 voltage regulator die was mounted to an open Quad Flat No-leads package (QFN) for reliability testing. For the stress measurement, a specifically designed stress measurement die was mounted to the QFN package. The chips were encapsulated with ULHysol EO1080 thermosetting polymer material. Curing was performed using an open-ended microwave oven system equipped with in situ temperature control. Three different temperature profiles for microwave curing were selected according to the requested degree of cure and chemical composition of the cured material. A convection cure profile was selected for the control group samples. Thermal cycling and HAST tests were performed on a total number of 80 chips. 95 QFN packages with stress measurement chips were also manufactured. Increased lifetime expectancy of the microwave cured packaged chips was experimentally demonstrated and measured between 62% to 149% increased lifetime expectancy after Temperature Cycling Test (TCT), and between 63% and 331% after highly Accelerated Ageing Test (HAST) and TCT compared to conventionally cured packages. Analysis of specifically designed stress test chips showed significantly lower residual stresses ranging from 26 MPa to 58.3 MPa within the microwave cured packages compared to conventionally cured packaged chips which displayed residual stresses ranging from 54 MPa to 80.5 MPa. This article therefore provides additional confidence in the industrial relevance of the microwave curing system and its advantages compared to traditional convection oven systems.