A Fractional-Factorial Numerical Technique For Stress Analysis Of Glass to Metal Lead Seals
B. Mathieu and A. Dasgupta
Fracture of glass seals in metallic hermetic electronic packaging is
a significant failure mode because it may lead to moisture ingress and
also to loss of load carrying capacity of the glass seal. Seal glasses
are intrinsically brittle and their fracture is governed by the stress
generated. This study investigates stresses in lead seals caused,
by handling, testing, mechanical vibration, and thermal excursions.
Loads considered are axial tension, bending, and twisting of the lead.
More general loading can be handled by superposition of these results.
Factorial techniques, commonly used in multi-variable Design of Experiments
(DoE), are used in conjunction with finite element parametric simulations,
to formulate closed-form regression models which relate the maximum principal
stress within the glass seal to the type of loading and geometry.
The accuracy of the proposed closed-form equations is verified through
analysis of residuals. The analysis reveals the sensitivity of the
magnitude of the seal stress to design variables such as the materials
and geometry of the seal, lead, and package. Manufacturing-induced
problems such as defects and flaws are not considered. An additional
purpose for presenting this study is to illustrate the use of design of
experiment methods for developing closed-form models and design guidelines
from simulation studies, in a multi-variable problem
article is available to CALCE Consortium Members.