|1. The requirements for test coupons
for the single ended and differential wave impedance measurement
- The Pads for „Signal“ and „GND“ should have
a distance of 2.54mm
- In X-direction, the distance of the GND-Pads
to both Signal pads should be
minus 1.27mm respectively plus 1.27mm (pic.1).
- To reach a better distinguish, it is recommend to make the
Signal pads round,
and the GND-Pads – square (pic.1).
- Just one GND-Pad is sufficient as Reference
for Impedance measuring, for each group of tracks to be measured
- Just one group of test Pads at the ends of
test – tracks is sufficient
for Impedance measuring (pic.1).
- The length of the test tracks should be
between 130 mm and 145 mm (pic.2).
- In the centre of each pad there shall be
a hole into which the pins of the test adapter shall be put.
The drill – diameter of these hole at test-pads can be between
0.8mm to 1.2mm (pic.4).
- The outside dimension of the Coupon should
be 10.0mm x 160.0mm (pic.3).
- Several Coupons can be placed besides each other.
2.Number of different Test - pads
The groups of test pads (here: A, B, C) can
be located below each other or beside each other.
If we place the test pads besides each other
(case of multiple Impedance measuring) than we can use the space
more economically (pic.5).
3.You can download an example of Test-Coupon
GERBER-Data (Thanks to company Polar Instruments) here (.zip,