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PIM - Passive Intermodulation
Jim Francey
Technical Service Manager
Taconic has a market-leading position in the design and supply of woven-
glass PTFE laminates. Taconic was the first laminator to introduce long-format
laminates for cellular base-station infrastructure, and indeed with the TLC
range was the first to introduce low-cost PTFE substrates for commercial
wireless applications.
Taconic's core-competency is the manufacture of PTFE-coated woven glass
fabrics; it's these fabrics that form the basis of Taconic's PTFE laminates. As a
commitment to the RF/Microwave industry and for security of supply, Taconic
ADD manufacture identical coated-fabrics and laminates at its three manufacturing
locations in the South Korea, Europe and USA. With forty years coating
expertise Taconic laminates typically exceed industry specifications.
Customers worldwide have made Taconic the world's largest woven-glass PTFE
laminate manufacturer giving a leadership position with suppliers. This has
helped Taconic create unique solutions including the industry's premier PIM
response. For example product evaluations at several antenna manufacturers
have demonstrated the choice of copper foil has a significant role in PIM
performance. The studies show rolled-annealed (RA) copper yielded better
passive intermodulation (PIM, IMD) performance than electro deposited (ED)
copper foil. The downside of RA foil is its comparatively higher cost.
Scrutiny of RA foil shows a smaller "tooth structure" than standard
ED foil:
RA foil is also free of metallic zinc. The application if zinc on ED foil is largely
historical; to prevent copper migration associated with FR4 epoxy. Copper
migration is not an issue with PTFE substrates and is potentially problematic
as it affects PIM (copper and zinc are of course dissimilar with divergent
positions in the electrochemical series).
Working in close cooperation with foil suppliers, Taconic's response was to
look to a solution with ED copper economies. Today Taconic offers CL copper
foil; a "low-profile", zinc-free ED foil.
Successive comparative studies show the improvements of the lower-profile
ED foil. The following charts of a case study show one set of results, whereby
CL1 copper foil is outperforming RA copper foil:
Taconic's engineers understand the entire process from design to assembly
and are best placed to offer advice on product selection. Furthermore Taconic
enjoys close relations with PCB [PWB] processors worldwide enabling seamless
new-product introduction through to steady state manufacture. Taconic offer
their on-line ERP window that allows partners to track order progress.
In short, Taconic is best placed to satisfy the RF-Microwave industry
requirements for low-loss, stable dielectric-constant laminates. What's more,
Taconic's PIM solutions can be applied to ALL Taconic material grades TLY,
TLX, TLC, RF-30, and RF-35.
All these laminates are available in trimmed sheet sizes ranging from 36" x 48" (914 x 1220 mm) up to
36" x 102" (914 x 2590 mm).
For more information please contact Taconic Customer Service.
and also view
 CL1 Very Low Profile ED Copper Foils for Minimising Passive Intermodulation
*For an explanation of PIM we suggest you visit Summitek at:
http://www.summitekinstruments.com
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