Reliability Considerations in the STD Development

The structural features of the STD hybrid circuit building process are described. `Two features of this structure are unusual: first, the use of evaporated and electroplated metal contacts and, second, the use of a thermoplastic layer to separate two layers of metallization. Since the latter feature is unique to STD at this time, the adhesive properties of the plastic to the other circuit elements and the metal films to the plastic, together with the mechanical strains developed among the structural parts, are examined and discussed in detail. It is shown that the integral parts of the STD circuit adhere well and that the lateral strains, caused by thermal expansion, are insignificant. Also, any vertical strains in the system do not adversely affect contact continuity.