ICSR (Soldering and Reliability) Conference Proceedings


Characterization And Prediction Of Pad-Crater Fracture In Lead-Free Compatible PCBs

Authors: Siva P.V. Nadimpalli and Jan K. Spelt
Company: Brown University and University of Toronto
Date Published: 5/4/2011   Conference: ICSR (Soldering and Reliability)


Abstract: Epoxy-based printed circuit board (PCB) laminates that are compatible with higher lead-free reflow temperatures can be more brittle than earlier materials. These epoxies can have an increased propensity for pad-cratering in lead-free assemblies. In this study, padcrater fracture was characterized in terms of the critical strain energy release rate, Jci, measured at various mode ratios, (psi). Specimens were prepared from lead-free CTBGA package-PCB assemblies and fractured at low and high loading rates in various bending configurations to generate a range of mode ratios. The specimens tested at low loading rates all failed by pad cratering, while the ones tested at higher loading rates fractured in the brittle intermetallic layer of the solder. The Jci of pad cratering increased with the mode ratio of loading (or phase angle, psi), but was independent of surface finish (OSP and ENIG) and reflow profile (time above liquidus 60 s and 120 s). The generality of the J=Jci(psi) failure criterion to predict pad-cratering fracture was then demonstrated by predicting the fracture loads of single lap-shear specimens made from the same lead-free assemblies.

Key Words: pad cratering, PCB fracture, epoxy, chip scale package, bending, finite element, lead-free solder, pad, circuit board



Members download articles for free:

Not a member yet?

What else do you get when you join SMTA? Read about all of the benefits that go along with membership.

Notice: Sharing of articles is restricted to just your immediate work group. Downloaded papers should not be stored on an external network or shared on the internet.


Back


SMTA Headquarters
6600 City West Parkway, Suite 300
Eden Prairie, MN 55344 USA

Phone +1 952.920.7682
Fax +1 952.926.1819