FAB

Friction Acoustic Bonding (FAB)

Friction Acoustic Bonding is a method of making lap welds in thin metals as well as many non-metallic materials. The process was originally developed and patented over 20 years ago when it was known as Friction Seam Welding. Successful demonstrations of the process were given but the restrictions placed upon the applications by the patent holder at the time prevented its commercial application. The patent on the process has now expired and there is a renewed interest in the commercial advantages offered by the process.

The FAB technique uses a rapidly rotating disc or wheel to impact on the surface of the materials to be bonded. The process can be used to produce linear lap welds between thin sheets of metals with thicknesses in the range 0.01mm to 3mm. The welding action comes about through mechanical agitation caused by the tool which results in the interface between the two materials becoming plastically bonded. The result is a welded joint where the materials have remained well below their melting point. The resulting continuous weld has a width of about 1 - 2mm.

Examination of the welds indicates that elements of both friction welding and ultrasonic welding are involved. The rotating disc causes oscillating frictional forces to be established at the interface between the two materials which generates ultrasonic vibrations. The ultrasonic vibrations break down the oxide layers and other surface contaminants which then enables welding to occur at high speed. Welding speeds are typically between 100 and 500mm/second.

Materials which have been joined by this process include copper, aluminium, and steel joined to themselves or in dissimilar combinations. Copper braid has also been welded to copper sheet using this approach. Other welds have been made in titanium, nickel, brass, gold, silver, lead, tin, carbon, and plastic films.

Applications include the joining of foil sheathing in screened cables, the seam welding of cans, and the joining of copper leads to aluminium capacitors. The process is particularly useful in the micro-welding of electronic assemblies because the low heat input avoids damage to heat sensitive components. Welds have also been made through water or oil based liquids.

Dissimilar combinations of materials can also be welded using FAB which may not be possible using any other technique.

Diverse have undertaken a number of projects using FAB. Any application would require tests to investigate the feasibility of using FAB, before suitable welding equipment can be specified.

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