An interconnect structure with a plurality of low dielectric constant insulating layers acting as etch stops is disclosed. Detected are a first intensity at a particular wave number of infrared radiation reflected from a test-sample solder material by illuminating light to the test-sample solder material and a second intensity at the particular wave number of infrared radiation reflected from a comparative-sample solder material by illuminating light to the comparative-sample solder material. The permeated liquid water contributes to the withdrawal of the heat of reaction by evaporating at least in part inside the fuel cells. The magnetizing time is correlated to the enable period of the magnetizing voltage.