Premium
X‐ray determination of encapsulation stresses on silicon wafers
Author(s) -
Nguyen L. T.,
Noyan I. C.
Publication year - 1988
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760281602
Subject(s) - materials science , wafer , epoxy , curvature , composite material , silicon , internal stress , diffraction , composite number , x ray , coating , optics , optoelectronics , geometry , mathematics , physics
Preliminary results of a systematic investigation of the behavior of encapsulating materials used in electronic packaging are reported. In this study, the radii of curvature of silicon wafers encapsulated with a filled epoxy are obtained by X‐ray diffraction. The values recorded agree closely with Dektak scanning for thin coatings. However, deviations occur with thicker layers due to the fundamental difference in the parameter measured by both techniques. Analytical solutions are proposed for both one‐and two‐sided encapsulation. Results predicted for the one‐sided coating describe a more severe state of stress within the package, and a correspondingly higher curvature than observed. X‐ray radiographs and optical micrographs of molded packages reveal the presence of internal voids and surface cracks. Such defects relax the stresses within the composite system and may account for the discrepancy observed.