MODELS FOR SOLDER-JOINT RELIABILITY OF COMPONENTS ON METAL-BACKED PRINTED CIRCUIT BOARDSAuthor: Pradeep Lall et al.
Company: Auburn University
Date Published: 9/26/2004 Conference: SMTA International
There have been several studies on electronic reliability for automotive environments [Lall 2003, Syed 1996, Evans 1997, Mawer 1999]. However, none of the previous studies address the damage mechanics of electronics on metal backed substrates. Published data on crack propagation has targeted ceramic BGAs [Darveaux 1992, 1995, 2000] and plastic BGAs on glass-epoxy laminate [Lall 2003]. In this work, the effect of metal-backed boards on the interconnect reliability will be evaluated. Other failure mechanisms investigated include - delamination of PCB from metal backing.
The test vehicle is a metal backed FR4-06 laminate. Metal backings investigated include - aluminum and beryllium copper. Three adhesive have been investigated for metal backing including - arlon, pressure sensitive adhesive and pre-preg. The use of conformal coating for reliability improvement has also been investigated. Component architectures tested include – plastic ball grid array devices, C2BGA devices, QFN, and discrete resistors. Reliability of the component architectures has been evaluated for HASL and electroless Ni/Au finishes.
Crack propagation and intermetallic thickness data has been acquired as a function of cycle count. Reliability data has been acquired on all these architectures. Material constitutive behavior of arlon and PSA has been measured using uni-axial test samples. The measured constitutive behavior has been incorporated into non-linear finite element simulations. Predictive models have been developed for the dominant failure mechanisms for all the component architectures tested.
Key words: Metal-back, Solder Joint, Reliability
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