Amschl, Dominik

Bösch, Wolfgang

Freidl, Philipp Franz

Gadringer, Michael Ernst

Holweg, Gerald

Mühlmann, Ulrich

Sattler, Sebastian

TUGraz OPEN Library

The commercial deployment of radio frequencysystems in the mm-wave regime is a driving forcefor the implementation of planar structures onprinted circuits boards (PCB).The characterization of such structures on a mm-wave PCB requires a well defined transition from aco-axial interface of a measurement device to aplanar interface of the device under test (DUT).One solution on the market which provides thesetransitions is a probe station with RF probes. Theinitial costs for a probe station are significant, but asingle RF probe can endure several thousandtouchdowns. Another advantage of this approach isthe highly repeatable contacting process.The design of the landing pads has a significantimpact on the overall performance of themeasurement system using RF probes. To ensuremaximum measurement accuracy the landing padshould provide a low reflective, low-loss and lowdispersive transition between the probe tips andthe microstrip interface of the DUT. While thedesign of landing pads up to mm-wave frequenciesfor on-wafer measurements is a well investigatedtopic, there is little literature available whichfocuses on landing pads for PCB applications atmm-wave frequencies.IntroductionPCB RF Probe Landing Pads for mm-Wave MeasurementsMeasurementsMicroelectronic Systems Symposium28-29 April 2016 • WienInput matching of the fixture Attenuation of the through configurationParameter sets for the different variants (μm)Picture of the landing pads (#1) in aThrough configuration Variation of the input matching for different realizations of #1Philipp F. Freidl1,3, Sebastian Sattler1 , Michael Gadringer1 , Dominik Amschl1 ,Ulrich Mühlmann2 , Gerald Holweg3 , Wolfgang Bösch1*1 Institute of  Microwave and Photonic Engineering, Graz University of Technology, Graz, Austria2 NXP Semiconductors, Gratkorn, Austria  3 Development Center Graz, Infineon Technologies Austria AG, Graz, Austria* wbosch@tugraz.at, www.ihf.tugraz.at variant via1-x via2-x via1-y via-d g#1 150 150 400 600 55#2 100 200 400 600 55#3 200 100 400 600 55#4 150 150 370 600 55#5 150 150 430 600 55#6 150 150 400 600 50#7 150 150 400 600 55f (GHz)0 20 40 60 80-50-40-30-20-10#1, 1#1, 2#1, 3The presented design of the landing pad consistsof three areas: (1) a grounded coplanar waveguide(GCPW) which provides a suitable landingstructure for the coplanar like mode of a ground-signal-ground (GSG) probe and transforms it into agrounded CPW mode, (2) a transition area whichtransforms the grounded CPW mode into amicrostrip mode, and (3) a microstrip area, wherethe landing pad structure connects to the DUT.The initial structure was derived from thelimitations imposed by the probe and the selectedsubstrate material (Rogers RO3003, 127 μm thick).Thereafter the dimensions as well as the numberand positions of the vias were then optimized using3D-EM simulations. The resulting distances aresummarized in the table below named variant #1.Additionally, landing pads with different designparameters were manufactured (#2 - #7 in thetable).DesignDesign of the landing padDimensions of the landing pad structure for the parameter variationPhotograph of the landing padcpw-ltrans-lvia1-x via2-xvia-d via1-y g|S11| (dB)|S21| (dB)The input matching of the seven landing padvariants were measured over the frequencyrange DC – 90 GHz. In the plot variant #1 isindicated by the bold red trace. Over theconsidered frequency range a minimum returnloss of -13 dB can be recognized. Additionally, aresonant behavior between 70 – 80 GHz wasaccomplished supporting the operation in themm-wave regime.The insertion loss measurements wereaccomplished arranging the landing pads in aThrough configuration. All variants show aresonant behavior around 45 GHz and 75 GHzwhich corresponds to the zeros in the inputmatching measurements. Compared to all othervariants, #1 shows the most linear behavior overthe considered frequency range.To investigate the sensitivity of the selecteddesign (#1) to production and probing tolerancesthe input matching for three landing pads locatedat different positions of the PCB are compared.Deviations in the behavior can be recognized atthe zero around 45 GHz and above 75 GHz.ConclusionThis poster summarizes design andoptimization of landing pads for PCB probingapplications. Measurements of the landing padsshowed a minimum input matching of -13 dBand a maximum insertion loss of 1.4 dB overthe frequency range DC – 90 GHz.Investigations are ongoing to identify thesources for the variation between the individualrealizations of the launching structure toimprove the repeatability especially in thefrequency range above 70 GHz.AcknowledgmentsThis work was funded by the Austrian ResearchPromotion Agency (FFG) under the K-Project SecureContactless Sphere – Smart RFID-Technologies for aConnected World.The authors would like to express their gratitude formanufacturing the prototypes to Erich Schlaffer fromAT&S (Austria Technologie & SystemtechnikAktiengesellschaft).

PCB RF Probe Landing Pads for mm-Wave Measurements

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PCB RF Probe Landing Pads for mm-Wave Measurements

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