Seal rings are developed for packaging of circular openings of sensors and the fluidic flow based Micro Electro Mechanical Systems. Lead free technique based on isothermal solidification is used in this course of study. Thick film Au and high purity Cu substrates have been used during the development practice. Indium is used as the interlayer metal. Interconnections of high thermal and mechanical stabilities are fabricated for variable process parameters. The effects of temperature, pressure and reaction time on the ultimate tensile strength (UTS) and ultimate shear strength (USS) are presented and reported in this paper. The thermal stabilities of the specimen seal rings are obtained in the 700-900 K temperature range. Effect of ageing for various cycles and shelf life in different environments are discussed. (C) 2010 Elsevier B.V. All rights reserved.