Manufacturing test and measurement technology for wideband interconnects using transient thermal pulses

A new technique is being developed in which high-speed interconnects are tested for impedance tolerances and time of flight parameters by analyzing the measurements obtained with an IR camera of the propagation of a laser-delivered thermal pulse. This new technique is unlike any existing electrical interconnect characterization method in that it involves no physical contact with the circuit under test, facilitating measurements during manufacturing. It also has a high spatial resolution compared with TDR technology. It is capable of resolving the impedance profile of interconnects with very short lengths due to the rapid decay of thermal, as opposed to electrical, pulses. Through quantitative analysis of thermal pulse decay, relevant information about the interconnect geometry can be inferred which can be used to calculate electrical impedance. In addition, the technique can provide a direct estimate of the interconnect capacitance due to the analogy between electrostatic and steady-state thermal fields.