The influence of plastic-package on the voltage shift of voltage reference in analog circuit

Bandgap references, packaged in plastic, have been known to shift in voltage, a pre-package to post-package voltage variation. The package shift has been analytically discussed and experimentally investigated in this paper. Once the reference is encapsulated, a package-induced stresses present, which lead to a systematic voltage shifts ranging from 3 to 7 mV. The variation is closely related to package type and processing. Two kinds of shifting have been discussed, one is systematic package shift, which can be trimmed and its temperature coefficient compensated. The other is random package shift. The method on how to decrease them has been discussed, too. Structure and method of minimizing package-shift effects in integrated circuits is implemented by using a thick metallic overcoat applied after the deposition and patterning of the conventional insulating protective overcoat.