Laminate Resistance To Pad Crater Defects: Comparative Spherical Bend TestingAuthors: John McMahon, P.Eng. and Brian Gray, P.Eng.
Date Published: 1/18/2011 Conference: Pan Pacific Symposium
Celestica has been conducting an ongoing testing program to assess lead free (Pb-free) compatible materials in combination with area array packages against the currently accepted levels of process strain which were established when the dominant and limiting failure mode was interfacial fracture (IFF) in complex intermetallic compound (IMC) layers at the solder / package interface. This program has identified “Pad Crater / Pad Lift” as the dominant failure mode in Pb-free materials and as a result Celestica has modified internal guidelines for process strain limits which reflect an increased sensitivity to strain rate. The next phase of testing is intended to compare various Pb-free compatible laminates currently in production to assess their resistance / susceptibility to the Pad Crater phenomenon. Test methods, test results, and failure analysis are discussed.
Key words: Pad Crater, Spherical bend test, Mechanical Failure Mode, Laminate Testing, Process Strain.
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