islands of powder with irregular spaces between them the contact pieces produced in accordance with the invention exhibit advantageous properties in many of their applications they can be manufactured economically as mass produced articles and permit the use of contact materials having a considerable capacity for resisting fusion since the parts to be connected are not heated to any considerable extent during sonic welding the original mechanical properties of the carrier and the contact piece are for the most part retained a small contact piece in the form of a plate made of agcdo in which were incorporated non metallic cadmium oxide components in a silver matrix material had a diameter of 4 5 mm and a thickness of 1 4 mm after a pure aluminium foil having a thickness of 0 1 mm had been interposed this contact piece was joined by sonic welding to a carrier consisting of a brass strip 8 mm in width and 0 7 mm in thickness the output of the sonic oscillator was 1200 w and the frequency 18 khz a compressive force of approximately 736 n was applied during the welding operation the welding time was 1 5 sec during welding the residual portion of the aluminium foil became detached at the edge of the surface over which the joint was made and was removed the.