A method and apparatus for a thermal stratification test providing
cyclical and steady-state stratified environments. In order to test an
electronic device, for example one having one or more levels of
ball-grid-array interconnections, e.g., connecting a chip to a flip-chip
substrate and connecting the flip-chip substrate to a printed circuit
board of a device, an apparatus and method are provided to heat one side
of the device while cooling the second side. In some embodiments, the
process is then reversed to cool the first side and heat the second. Some
embodiments repeat the cycle of heat-cool-heat-cool several times, and
then perform functional tests of the electronic circuitry. In some
embodiments, the functional tests are performed in one or more
thermal-stratification configurations after cycling at more extreme
thermal stratification setups. In some embodiments, a test that
emphasizes solder creep is employed.