RF Probing With Rohde & Schwarz ZNB VNA. PacketMicro, Inc Wyatt Drive, Suite 9, Santa Clara, CA

Transcription

1 RF Probing With Rohde & Schwarz ZNB VNA PacketMicro, Inc Wyatt Drive, Suite 9, Santa Clara, CA

2 Outline Why RF Probing Page 3 4 S-Probe Overview Page 5-8 RF Probing Tips Page 9 Tools: Probes, Positioners, and Microscopes Page Probe Planarization with Mylar Page Probe Planarization with Marker Page RF Probing in a Box Page 25 Import TCS70xx.calkit file Page SOLT Calibration Page Manual Entry of TCS70 into VNA Page

3 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 3

4 Measurements of RF Low-Pass Filter SMA-SMA RProbe - SMA Soldered Cable - SMA RF probe is almost as good as SMA connector! 4

5 S-Probe Features High Bandwidth: DC to 20 GHz Low Insertion Loss: < 3 20 GHz Ruggedness: Beryllium Copper tips Probe-tip Calibration: TCS 60 Cal Substrate High Repeatability: No moving part S-Probe Part No. SP-GR GHz, 0.25 mm/10 mil pitch SP-GR GHz, 0.4 mm/16 mil pitch SP-GR GHz, 0.5 mm/20 mil pitch SP-GR GHz, 0.8 mm/32 mil pitch SP-GR GHz, 1.0 mm/40 mil pitch SP-GR GHz, 1.2 mm/48 mil pitch Un-calibrated S21 for 3 probe pitches Un-calibrated S11 for 3 probe pitches 5

6 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) 6

7 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. 7

8 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 8

9 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 90x) microscope!) Fine-tip Sharpie pen 9

10 Precision TP250 Positioner 10

11 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 11

12 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 12

13 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. 13

14 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. 14

15 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. 15

16 Use VNA to Verify Probe Contacts Both tips touching Short Both tips leave light probe marks VNA Smith Chart shows Short 16

17 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 17

18 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 18

19 Both Tips Touch Down Simultaneously 2 Tip Marks Both tips touch down simultaneously Clean up solder bumps with industrial alcohol after probing 19

20 RF Probing in a Box FP40 Positioner AM4115ZTL Dino-Lite Microscope TP50 TP250 Positioner TP60 PH100 S-Probes TP60 TP250 Positioner 20

21 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 21

22 Import TCS70xx.calkit file Press hard Cal button -> Cal Devices -> Cal Kits -> Import Cal Kit 22

23 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. 23

24 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 24

25 Start Manual Calibration Press hard Cal button -> Start Cal -> Start (Manual) 25

26 Select Cal Kit Select User Connect 1 connector -> Cal Kit ->Start 26

27 Set Marker to Lowest Frequency Use 180 change in phase to detect short. 27

28 Reflection Calibration - Short Perform Short first to verify probe planarization 180 phase change Short Pattern 28

29 Reflection Calibration - Open Open Open Pattern 29

30 Reflection Calibration - Load Load Load Pattern 30

31 Perform Reflection OSM Cal for Port#2 31

32 Transmission Calibration - Thru Make sure that both probes touch down GND SIG Two probes measure the Thru standard. Thru standard on TCS

33 Transmission Calibration - Thru At least one probe does not touch down. At least one probe does not touch down 33

34 Transmission Calibration - Thru Both probes touch down Both probes touch down Both probes touch down 34

35 Correct Thru Calibration S21 should be flat 35

36 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 36

37 S11 Measurements of a 50Ω Standard 0 db 10 db/div S11 after probe tip calibration 37

38 Appendix Manual Entry of TCS70 Press hard Cal button -> Cal Devices -> Cal Connector Types Need to add connector type before adding the Cal Kit! 38

39 Select Connector Type Select Sexless and 50Ω for connector type 39

40 Add Cal Kit A User Conn 1 Ideal Kit is generated automatically. 40

41 Add and Rename Cal Kit Add and rename Cal Kit to TCS70_x.xmm 41

42 View or Modify Cal Kit Standards Define or modify Cal Kit Standards 42

43 Add Cal Kit Standards Add Open, Short, Match and Through standards 43

44 Enter Open Coefficient Enter coefficient for Open standard 44

45 Enter Short Coefficient Enter coefficient for Short standard 45

46 Enter Match (Load) Coefficient Enter coefficient for Match (Load) standard 46

47 Enter Through Coefficient Enter coefficient for Through standard 47

48 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: Office: