Impedance method was developed for quality control of bonded and soldered structures. The fact that variety of materials used (metals, wood, plastics, etc.) makes it difficult to identify areas of bond and soldering failures effectively. Impedance testing method of bonded materials proposed in the USSR by Yu. V. Lange showed significantly better results.
Application of impedance method in bonded structures with metal and non-metal sheaths with a thickness of 1.2—1.5 mm (for steel) and up to 2.5 mm for aluminum, with light fillers -honeycomb structures, foam, etc., and search for of delamination in laminated plastics. Sensitivity of testing significantly depends on the thickness of the skin and the rigidity of internal elements with a decrease in thickness of the skin and increase in stiffness, the sensitivity increases.
Impedance method is used for flaw detection of bonded joints and is used in cases where reliable one-hundred-percent control of solder joints is required.