RF Probing With Rohde & Schwarz ZNB VNA PacketMicro, Inc. 1900 Wyatt Drive, Suite 9, Santa Clara, CA 95054 www.packetmicro.com
Outline Why RF Probing Page 3 4 S-Probe Overview Page 5-8 RF Probing Tips Page 9 Tools: Probes, Positioners, and Microscopes Page 10-12 Probe Planarization with Mylar Page 13-21 Probe Planarization with Marker Page 22-24 RF Probing in a Box Page 25 Import TCS70xx.calkit file Page 26-28 SOLT Calibration Page 29-42 Manual Entry of TCS70 into VNA Page 43-52 www.packetmicro.com 2
Why RF Probing? Necessity: Constant shrinking size of circuit components makes soldering semi-rigid RF cables to test gigahertz circuits impractical. Accuracy: RF probes and calibration substrates allow engineers to perform probe-tip calibration for accurate, repetitive measurements. Productivity: Any engineer can do RF measurements in minutes without being a master in soldering semi-rigid cable www.packetmicro.com 3
Measurements of RF Low-Pass Filter SMA-SMA RProbe - SMA Soldered Cable - SMA RF probe is almost as good as SMA connector! www.packetmicro.com 4
S-Probe Features High Bandwidth: DC to 20 GHz Low Insertion Loss: < 3 db @ 20 GHz Ruggedness: Beryllium Copper tips Probe-tip Calibration: TCS 60 Cal Substrate High Repeatability: No moving part S-Probe Part No. SP-GR-2015025 20 GHz, 0.25 mm/10 mil pitch SP-GR-201504 20 GHz, 0.4 mm/16 mil pitch SP-GR-201505 20 GHz, 0.5 mm/20 mil pitch SP-GR-181508 18 GHz, 0.8 mm/32 mil pitch SP-GR-181510 18 GHz, 1.0 mm/40 mil pitch SP-GR-161512 16 GHz, 1.2 mm/48 mil pitch Un-calibrated S21 for 3 probe pitches Un-calibrated S11 for 3 probe pitches www.packetmicro.com 5
Thru Measurement with Probe-Tip Calibration Thru Measurement Calibrated at probe tips (20 GHz) (20 GHz) Calibrated at probe tips Calibrated at SMA connectors Calibrated at SMA connector (20 GHz) (20 GHz) Probe-tip calibration (0.5 mm S-Probe) www.packetmicro.com 6
S11 Measurements of a 50Ω Load Calibrated at SMA connectors Calibrated at probe tips (0.5 mm S-Probe) (20 GHz) Probe-tip calibration allows accurate, repetitive measurements. www.packetmicro.com 7
Probe Planarization Tips Good contact of both probe tips with the DUT is essential to accurate calibration and measurements. Mylar tape provides leveling guidance on flat, even surface (bare PCB). Color marker helps on uneven surface (solder bump). A good microscope is important. You might damage the probe if you cannot see its tips well. GND Tip skid marks Mylar indentation caused by both tips Signal www.packetmicro.com 8
Tools - Accessories Optical Microscope (~ 90 x magnification) USB Digital Microscope (~ 90 x magnification) TCS70 Calibration Substrate Mylar Tape Using a good microscope is essential. You might damage the probe if you cannot see its tips well. (Make sure to use a long working range (5 cm @ 90x) microscope!) www.packetmicro.com Fine-tip Sharpie pen 9
Precision TP250 Positioner www.packetmicro.com 10
Probe Planarization Tips Good contact of both probe tips with the DUT is essential to accurate calibration and measurements. Mylar tape provides leveling guidance on flat, even surface (bare PCB). Color marker helps on uneven surface (solder bump). A good microscope is important. You might damage the probe if you cannot see its tips well. GND Tip skid marks Mylar indentation caused by both tips Signal www.packetmicro.com 11
Probing Test Pads on Even Surfaces Use the Mylar tape on the back of the plastic cap for probe planarization by observing the indentation caused by the tips. Remove the plastic cap and perform probing Affix a Mylar tape next to test pads if there is not enough space for placing the plastic cap. GND Mylar indentation caused by both tips Signal Mylar www.packetmicro.com 12
Signal tip touches down first GND Signal Mylar indentation caused by signal tip Step 1: Land the probe tips on the tape and observe the probe-tip footprint. Above image shows that signal tip touches the surface first. www.packetmicro.com 13
GND tip touches down first Mylar indentation caused by GND tip GND Signal Step 2: Adjust the planarization knob on the TP150 positioner to lower the GND tip. Above image shows that GND tip touches the surface first. www.packetmicro.com 14
Both tips touch down simultaneously GND Signal Mylar indentation caused by both tips Step 3: Adjust the planarization knob on the positioner to land both probe tips. Above image shows the two probe tips touch the surface evenly. www.packetmicro.com 15
Use VNA to Verify Probe Contacts Both tips touching Short Both tips leave light probe marks VNA Smith Chart shows Short www.packetmicro.com 16
Tip skid marks Probing Test Pads on Uneven Surfaces Color solder bumps with a Sharpie Use the probe skid marks to confirm good tip contact Clean up the solder bumps with industrial alcohol after probing Fine-tip Sharpie www.packetmicro.com 17
Use Probe Skid Marks on Solder Bumps GND Tip Mark Left GND tip touches down first Signal Tip Mark Right signal tip touches down first www.packetmicro.com 18
Both Tips Touch Down Simultaneously 2 Tip Marks Both tips touch down simultaneously Clean up solder bumps with industrial alcohol after probing www.packetmicro.com 19
RF Probing in a Box FP40 Positioner AM4115ZTL Dino-Lite Microscope TP50 TP250 Positioner TP60 PH100 S-Probes TP60 TP250 Positioner www.packetmicro.com 20
Two-Port Probe-Tip Calibration Import TCS70 coefficients (probe dependent) into VNA (TCS70_0.5MM.calkit, TCS70_0.8MM.calkit, TCS70_1.0MM.calkit) Perform 2-port SOLT calibration www.packetmicro.com 21
Import TCS70xx.calkit file Press hard Cal button -> Cal Devices -> Cal Kits -> Import Cal Kit www.packetmicro.com 22
Import TCS70xx.calkit file cont. User Conn 1 connector type and User Conn 1 Ideal Kit are generated in addition to the TCS70_x.xmm cal kits. www.packetmicro.com 23
2-Port Probe-Tip Calibration Reflection calibration (Short, Open, Load calibration for two ports) Transmission calibration (Thru calibration) S G Thru G S Short Open www.packetmicro.com 24
Start Manual Calibration Press hard Cal button -> Start Cal -> Start (Manual) www.packetmicro.com 25
Select Cal Kit Select User Connect 1 connector -> Cal Kit ->Start www.packetmicro.com 26
Set Marker to Lowest Frequency Use 180 change in phase to detect short. www.packetmicro.com 27
Reflection Calibration - Short Perform Short first to verify probe planarization 180 phase change Short Pattern www.packetmicro.com 28
Reflection Calibration - Open Open Open Pattern www.packetmicro.com 29
Reflection Calibration - Load Load Load Pattern www.packetmicro.com 30
Perform Reflection OSM Cal for Port#2 www.packetmicro.com 31
Transmission Calibration - Thru Make sure that both probes touch down GND SIG Two probes measure the Thru standard. Thru standard on TCS70 www.packetmicro.com 32
Transmission Calibration - Thru At least one probe does not touch down. At least one probe does not touch down www.packetmicro.com 33
Transmission Calibration - Thru Both probes touch down Both probes touch down Both probes touch down www.packetmicro.com 34
Correct Thru Calibration S21 should be flat www.packetmicro.com 35
Completion of SOLT Calibration 0 db 10 db/div 0 db 10 db/div 0 db 0.01 db/div 0 db 0.01 db/div www.packetmicro.com 36
S11 Measurements of a 50Ω Standard 0 db 10 db/div S11 after probe tip calibration www.packetmicro.com 37
Appendix Manual Entry of TCS70 Press hard Cal button -> Cal Devices -> Cal Connector Types Need to add connector type before adding the Cal Kit! www.packetmicro.com 38
Select Connector Type Select Sexless and 50Ω for connector type www.packetmicro.com 39
Add Cal Kit A User Conn 1 Ideal Kit is generated automatically. www.packetmicro.com 40
Add and Rename Cal Kit Add and rename Cal Kit to TCS70_x.xmm www.packetmicro.com 41
View or Modify Cal Kit Standards Define or modify Cal Kit Standards www.packetmicro.com 42
Add Cal Kit Standards Add Open, Short, Match and Through standards www.packetmicro.com 43
Enter Open Coefficient Enter coefficient for Open standard www.packetmicro.com 44
Enter Short Coefficient Enter coefficient for Short standard www.packetmicro.com 45
Enter Match (Load) Coefficient Enter coefficient for Match (Load) standard www.packetmicro.com 46
Enter Through Coefficient Enter coefficient for Through standard www.packetmicro.com 47
Thank You We help make your high-speed probing projects successful! Flex Probe Stations Rugged 20 GHz RF Probes Laboratory Rental Engineering Services Signal Integrity Consulting Contact: support@packetmicro.com Office: 408-675-3900 www.packetmicro.com 48