Stress balanced composite laminate material

Abstract

A composite laminated structure is provided which includes a thin copper or other conducting material laminated to a polyimide having a relatively high coefficient of thermal expansion which in turn is bonded to a polyimide which has a relatively low coefficient of thermal expansion (CTE). This polyimide is in turn bonded to a relatively thick base such as stainless steel. The thicknesses of the polyimide and copper and the specific coefficients of thermal expansion of all of the material are so selected that in the absence of support from the stainless steel the stresses between the various layers are balanced in such a way that the two layers of polyimide and the copper remain essentially flat. This allows for a stainless steel substrate to have a portion etched away or otherwise removed so as to form a hinge region; and when the stainless steel is removed, the remaining structure will remain essentially flat and not curl either toward the stainless steel or toward the copper. From this a desired bend angle can be formed in the resulting trilayer structure comprised of two polyimide layers and one copper layer.

Dependencies are inferred from the claim text.