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The Influence of                  RF Substrate Materials                            on                 Passive Intermodula...
What is Passive IM ?       • Passive Intermodulation Distortion              Created when two or more signals combine    ...
Why do we care ?          • Nonlinearity of passive components            causes power at transmit frequencies to         ...
How is Passive IM Specified ?        • Absolute Power (dBm)                  The Absolute IM Power (in dBm) of the       ...
How Is Passive IM Measured        •    Multiple signals are injected to device        •    High Power Amplifiers        • ...
Putting it in Perspective          • Typically looking to measure                  -110dBm or better with two +43dBm     ...
Typical PIM Causes       • Degradation Due to Environment              Contaminated conductors & Interfaces              ...
Typical PIM Causes         • Printed Circuits Boards                  Processing issues                  Laminate issues...
Typical PIM Causes    There are so many causes for PIM issues …    It is never related to one issue; it is usually a    st...
Laminates        • Not every laminate is suitable for          antenna pcbs!              Tightly-controlled DK tolerance...
Low PIM Material Solutions                 … for Base Station Antenna pcbs            (phase shifter, power splitter, powe...
Copper Foil         Copper foil is of huge influence on PIM                 Typical Laminate Construction: Copper foil PTF...
Very Low Profile ED Copper Foil                                                “Drum” or “shiny” side                 Stan...
Very Low Profile ED Copper Foil                                                   Copper treatment topography             ...
Very Low Profile ED Copper Foil      Incomplete      etching          VLP copper increases opportunity for              c...
SEM Photo of Microstrip (C1 copper)    copper debris left in at the    bottom of the etched track© Taconic 2012           ...
Reverse Treatment Copper Foil© Taconic 2007   www.taconic-add.com
Reverse Treatment Copper Foil© Taconic 2007   www.taconic-add.com
Reverse Treatment Copper Foil                                 CL1 copper shows                                 a lower sur...
Surface Protection  Attack from air and chemicals leading to underetching                                       and discol...
Surface Protection             Solder Mask leads to protection of side wall                      from air and chemicals© T...
Influence of protective coating                                                                       PIM [dBm]           ...
Low PIM Laminate Solutions      Selecting the most                          suitable laminate      together with the most ...
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The Influence of RF Substrate Materials on Passive Intermodulation (PIM)

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The Influence of RF Substrate Materials on Passive Intermodulation (PIM)

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Transcript of "The Influence of RF Substrate Materials on Passive Intermodulation (PIM)"

  1. 1. The Influence of RF Substrate Materials on Passive Intermodulation (PIM) Manfred Huschka, HKPCA 2012© Taconic 2012 www.taconic-add.com
  2. 2. What is Passive IM ? • Passive Intermodulation Distortion  Created when two or more signals combine to generate new frequency products 2© Taconic 2012 www.taconic-add.com
  3. 3. Why do we care ? • Nonlinearity of passive components causes power at transmit frequencies to mix into the systems receive band  Channels are blocked  Phone calls can be dropped Reduced Capacity = Reduced Revenue ! 3© Taconic 2012 www.taconic-add.com
  4. 4. How is Passive IM Specified ? • Absolute Power (dBm)  The Absolute IM Power (in dBm) of the Intermodulation Signal • Relative Power (dBc)  IM Signal Power relative to the Standard Signal Carrier  Example : -110dBm IM signal generated by two +43dBm tones is a –153dBc IM level 4© Taconic 2012 www.taconic-add.com
  5. 5. How Is Passive IM Measured • Multiple signals are injected to device • High Power Amplifiers • Highly Sensitive Receiver (LNA) • Significant Filtering  +43dBm Tx Power  -140dBm Rx Noise Floor  …………….means 183dB Isolation ! 5© Taconic 2012 www.taconic-add.com
  6. 6. Putting it in Perspective • Typically looking to measure  -110dBm or better with two +43dBm carriers (-153dBc) • In Linear Terms…  Distance to sun = 150,000,000 km  -153dBc equates to approx 0.07mm 6© Taconic 2012 www.taconic-add.com
  7. 7. Typical PIM Causes • Degradation Due to Environment  Contaminated conductors & Interfaces (Dirt, Dust, Moisture)  Wind induced vibrations  Temperature cycles • Semiconductor Junctions (Assembly)  Poor alignment of parts  Inadequately torqued screws & fasteners  Bad solder joints 7© Taconic 2012 www.taconic-add.com
  8. 8. Typical PIM Causes • Printed Circuits Boards  Processing issues  Laminate issues 8© Taconic 2012 www.taconic-add.com
  9. 9. Typical PIM Causes There are so many causes for PIM issues … It is never related to one issue; it is usually a stacking of smaller issues … Let us look at the influence of LAMINATES 9© Taconic 2012 www.taconic-add.com
  10. 10. Laminates • Not every laminate is suitable for antenna pcbs!  Tightly-controlled DK tolerance  Dissipation factor < Df 0.0025 for most grades @ 2GHz  Mature manufacturing technology  Lowest moisture absorption (<0.02%)  Bromine-free & RoHS compliant  Withstand >280°C assembly conditions; lead-free compatibility 10© Taconic 2012 www.taconic-add.com
  11. 11. Low PIM Material Solutions … for Base Station Antenna pcbs (phase shifter, power splitter, power combiner, filter) Grade DK Df @ 2GHz TLC-32 3.20 ± 0.05 0.0018 RF-30 3.00 ± 0.10 0.0013 RF-301 2.97 ± 0.05 0.0012 TLA-6 2.62 ± 0.05 0.0012 TLX-8 2.55 ± 0.04 0.0009 TLP-5 2.20 ± 0.02 0.0006© Taconic 2012 www.taconic-add.com
  12. 12. Copper Foil Copper foil is of huge influence on PIM Typical Laminate Construction: Copper foil PTFE Film Prepreg Prepreg Prepreg PTFE Film Copper Foil© Taconic 2012 www.taconic-add.com
  13. 13. Very Low Profile ED Copper Foil “Drum” or “shiny” side Standard ED Foil “Matte” or “treatment” side Additional plating process applied to “grow” microcrystalline copper structure to increase effective surface area.© Taconic 2012 www.taconic-add.com
  14. 14. Very Low Profile ED Copper Foil Copper treatment topography (dendritic structure) Rz DIN [micron] C1 5 m-12 m CL1 3-4 m Rz is a measure of the roughness (or profile)© Taconic 2012 www.taconic-add.com
  15. 15. Very Low Profile ED Copper Foil Incomplete etching  VLP copper increases opportunity for complete copper dendrite removal  Etching process is isotropic  “Cleaner/straighter” conductor side-walls© Taconic 2012 www.taconic-add.com
  16. 16. SEM Photo of Microstrip (C1 copper) copper debris left in at the bottom of the etched track© Taconic 2012 www.taconic-add.com
  17. 17. Reverse Treatment Copper Foil© Taconic 2007 www.taconic-add.com
  18. 18. Reverse Treatment Copper Foil© Taconic 2007 www.taconic-add.com
  19. 19. Reverse Treatment Copper Foil CL1 copper shows a lower surface topography over the plastic than C1 copper. Note the “cleaner” interface www.taconic-add.com
  20. 20. Surface Protection Attack from air and chemicals leading to underetching and discoloration (85°C/85% rh/200 h)© Taconic 2012 www.taconic-add.com
  21. 21. Surface Protection Solder Mask leads to protection of side wall from air and chemicals© Taconic 2012 www.taconic-add.com
  22. 22. Influence of protective coating PIM [dBm] Surface Max Min Max Min Protection (fwd) (fwd) (bwd) (bwd) Immersion Tin 1.0 micron -114 -126.5 -113.5 -124.5 OSP 0.3 micron -92.2 -96.5 -99.5 -112.6 Immersion 0.2 - 0.8 -81.5 -92.5 -94.5 -108.6 Silver micron ENIG 0.05 - 0.1 -50.5 -53.5 -58.5 -61.5 micron Au/ 3-5 micron Ni HASL 3-25 micron -103.9 -123 -112.3 -123.8 Frequency for measurements f1 f2 IM frequency 960 MHz 927.5 MHz 895 MHz 960 MHz 932.5 MHz 905 MHz Source: Powerwave 960 MHz 937.5 MHz 915 MHz© Taconic 2012 www.taconic-add.com
  23. 23. Low PIM Laminate Solutions Selecting the most suitable laminate together with the most suitable copper foil ensures that the most critical variables of influence upon Passive Intermodulation are met. During pcb manufacturing process many more critical variables have to get addressed … Taconic is here to support your needs!!© Taconic 2012 www.taconic-add.com
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