An electronic circuit assembly comprising: i) a circuit card assembly (CCA) having circuits integrated on a circuit surface; ii) a housing having an upper surface and a lower surface disposed on the CCA circuit surface, the housing comprising a via extending from the lower surface to the upper surface; and iii) a waveguide assembly disposed in the via. The waveguide assembly comprises: a) a first waveguide having a first dielectric value, a contact end of the first waveguide configured to make contact with the CCA circuit surface; b) a second waveguide having a second dielectric value, wherein the first dielectric value is greater than the second dielectric value; and c) a carrier for holding the first waveguide in contact with the second waveguide. The electronic circuit assembly further comprises: iv) a wave washer disposed in the via on a support surface of the carrier; and v) a third waveguide having a third dielectric value that is less than the second dielectric value. The third waveguide is disposed in the via between an end of the second waveguide and the upper surface of the housing. The wave washer presses apart the third waveguide and the waveguide assembly such that the contact end of the first waveguide is pressed into contact with the CCA circuit surface and the third waveguide is pressed into contact with an external circuit disposed above the housing.