Controlled impedance test system for complex, high-speed PCBs

September 02, 2014 // By Graham Prophet
PCB signal integrity tools company Polar Instruments is adding to its offering by adding a feature called Launch Point Extrapolation (LPE), for improved impedance control.

Polar's CITS880s Controlled Impedance Test System (CITS) introduces Launch Point Extrapolation (LPE), enabling PCB fabricators to improve impedance control for the latest high-speed PCBs which use finer trace widths and thinner copper compared to conventional boards. The increased accuracy and repeatability of the instantaneous impedance measurement optimum impedance control and manufacturing yields for complex PCB builds. LPE is a line-fit technique deployed on thinner traces which exhibit significant slope arising from DC and AC resistance along the trace. LPE “projects the impedance back” to a point close to the start of the trace where the influence of the DC and AC resistance on the measurement is minimal. Using the CITS880s in conjunction with 2D field solvers such as the Polar Si8000m, or Speedstack PCB, can yield a significant improvement in the correlation between measured and modelled impedance.

The CITS880s design focuses on further optimising pulse flatness. This, together with Polar’s latest robust high-speed IPS probes, means that fabricators can now test trace lengths 5 – 8 cm shorter than the minimum length imposed by previous generation CITS. For additional flexibility in high-volume applications, the CITS880s can output reports using CITS DRG Pro report generation software as well as directly outputting results in an Excel-compatible format. Forward compatibility and a step-by-step guide will help users to update legacy CITS test programs for use on the CITS880s.

Polar Instruments;