Coplanar transmission lines which make use of coaxial cables or parallel arrayed signal conductors and ground conductors are widely used for high-frequency signal transmission lines which transmit high-frequency signals with minimum attenuation.
These high-frequency signal lines are used selectively either to connector or to disconnect the signal lines. For example, in the performance characteristic evaluation device for semi-conductors which is known as the "IC tester" or "wafer prober", a great number of high-frequency signal paths are required to supply test signals to multiple test points of semiconductor devices and to receive them as well. In this type of device, a great number of test boards are provided depending on the dimensions, shape and in particular, the pin array and the number of devices being tested, coupled with the fact that the test device itself must be switched depending on the device being tested. It is effective in that when a great number of high-frequency connectors are used at this time, the time consumed for such operations as soldering is reduced which explains its popularity.
When the device being tested puts out more high-frequency signals and high performance, the connector being used naturally must put out more high-frequency signals and higher performance. If it does not, the device being tested cannot be relied on to produce accurate performance results and the reliability of the test itself is adversely affected.
A high-frequency signal connector which is used for these objectives is described in Japanese Patent Publication No. 51-44757. In this conventional electrical connector, the end of the coaxial cable is stripped so that the center signal conductor is exposed at a certain length of several mm. The braided outer conductor is folded backward and metallic sleeve is secured thereover. Next, a small socket pin is soldered to the signal conductor on the strip line which is formed on the circuit substrate. At the same time, legs of a resilient cylindrical ground socket are soldered and connected to the strip line ground conductor, the socket is set in place over the socket pin. A coaxial cable which has been stripped is inserted and connected to the socket pin and the ground socket.
The above-mentioned coaxial connector makes it possible to connect high-frequency signals to the strip line on the circuit substrate from the coaxial cable using the discontinuity of the minimum characteristic impedance. However, this was found to be defective in that a comparatively long socket pin and cylindrical ground socket were required so that miniaturization, in particular several hundreds of coaxial cables, could not be formed in a high density manner. In addition, a certain degree of discontinuity of the characteristic impedance due to the socket pin was unavoidable.
Therefore, it is an object of the present invention to provide a high-frequency connector which is capable of small-scale, high-density formation using the discontinuity of the minimum characteristic impedance on the strip line from the coaxial cable and a method for manufacturing this high-frequency connector.