Signal Microwave’s line of 2.92 mm, high performance, edge-launch connectors was designed for the thinner substrates being used today, typically between 5 and 10 mils thickness (0.127 to 0.254 mm) with dielectric constants from 3.0 to 3.5. Previously, high frequency board materials were around 30 mils thick, and the dielectric constants were lower, from 2.0 to 2.5.
The trend to thinner substrates and higher dielectric constants follows the development of mmWave systems. Impedance matching and 50 Ω line widths on thinner substrates better accommodate the small geometries of mmWave components, although one trade-off is thinner materials with narrower microstrip lines will have more loss.
With Signal Microwave’s new 2.92 mm edge connector, no soldering is required to mount the connector. The design has a 12 mil center conductor and a 39 mil outer conductor, and a 6 mil pin sits on the top of the printed circuit board, creating an offset toward the top. On an 8 mil test board, there is a slight step of 3 mils between the substrate ground and the coaxial ground.
For the individual connector, the VSWR specification is 1.15:1 maximum (i.e., 23 dB return loss). Two edge-launch connectors mounted to a 1 in. long, 50 Ω microstrip line on an 8 mil RO4003 substrate with an FR-4 backer has a measured maximum VSWR of 1.2:1 through 40 GHz. The corresponding insertion loss gradually increases with frequency to less than 3 dB at 40 GHz, including the loss of the 1 in. microstrip line.
Signal Microwave can provide design support to optimize the interface on the board for best performance. Connector samples with data and test boards are available for evaluation.
Signal Microwave, LLC