|Application Note AP8170|
|The RIE loss / attenuation measurement method and PCB manufacture|
Note: The RIE (Root Impulse Energy) loss measurement technique is a loss measurement technology that was explored but is no longer supported by Polar Instruments – this note is included in the Polar Signal Integrity Application Note series for historical interest. RIE has been superseded by the SET2DIL methodology (see AP8168 – PCB fabrication techniques for lossy transmission lines) as used in Polar's Atlas PCB lossy line test system.
The RIE loss /
method and PCB manufacture
In practice, the measurement trace will be aligned so as to avoid the trace running with the warp or weft of the material, thus minimizing the effect of dielectric variation sometimes caused by trace alignment with the fibre weave. A typical zigzag measurement trace routing is shown in the sample coupon below. The test coupon was generated using the Polar Instruments' CGen Coupon Generator.
Using Polar's CGen Coupon Generator the PCB designer or fabricator can create test coupons from scratch or take impedance controlled stackup information directly from Speedstack PCB or Speedstack Si and generate the appropriate impedance test coupon containing all the required PCB controlled impedance transmission line structures.
The coupon is tested with a TDR tester in much the same way as for controlled impedance.
The RIE test does not replace conventional impedance control techniques that are currently in
use; in fact one of the tests conducted is designed to make sure the coupon is
a 50 Ohms impedance. The TDR waveforms are sent as a data file to the computer and processed using complex maths to analyse and extract the changes which have occurred to the pulse as it
travelled down the
coupon (and back). The final outcome is a number which is a figure of merit for the board related to its loss characteristics. Use different material in the stack up and you will get a different
number; a bigger number means more loss.
Tests conducted by Polar
and Intel show that RIE testing is a practical and achievable test method; it is easily deployed and offers,
for example, repeatable, reliable discrimination between PCBs fabricated with a range of varying base material loss characteristics.