scope:

This test method is to evaluate the insulation resistance of ceramic plated-through hole multilayer printed wiring boards before, during and after the deteriorative effects of the high humidity heat conditions, and low temperature thermal shock exposures. Hybrid ceramic multilayer boards are employed as the dimensionally stable interconnection media between conventional printed boards and a variety of hybrid packages. Tropical degradation results from absorption of moisture vapors by vulnerable insulating materials and surface wetting of both metal conductors and the insulating laminate material. These phenomena may produce corrosion of metals, distortion of the boards, leaching, and detrimental changes in electrical properties. This method by virtue of the temperature cycling provides alternate cycles of condensation and temperature changes which is essential to the development of the corrosion process, and in addition produces a ''breathing'' action of moisture. The low temperature thermal shock phase of the test reveals otherwise undiscernible deterioration. The stresses caused by freezing moisture tends to widen cracks and fissures. As a result the deterioration can be detected by insulation resistance or interconnection resistance of the plated-through hole barrels.