Low-Cost One-Port Approach for Testing Integrated RF Substrates

Low-cost testing of integrated RF substrates is necessary to reduce their production cost. In this paper a new low-cost test approach is proposed for testing an integrated RF substrate with embedded RF passive filters. As compared to a conventional test method the proposed test method reduces the test-setup cost by around 40%. The proposed method enables testing of embedded RF filters by one-port measurement. Also, this method does not require a vector network analyzer and allows testing of these embedded RF circuits without any external test stimulus. Hence, this method brings about a significant reduction in the test cost. The proposed method uses a shift in the oscillation frequency of the test setup for testing embedded filters, but it does not require reconfiguration or conversion of filters into an oscillator as it is done in conventional oscillation-based test methods. The core principle of the method is to include embedded passive filters through one-port substrate surface probe into an external RF oscillator, located on the probe card. Such one-port probing causes a shift in the oscillation frequency of the oscillator because of the loading from the RF filter. The failures in the RF filter are detected by monitoring the shift in the oscillation frequency of the RF oscillator. The test method is demonstrated with both simulations and measurements. Also, wafer-level testing of an integrated RF substrate is illustrated.