RF Cable Assemblies Signal Growth
By Lynda Nolen, Bishop & Associates Inc.

RF assemblies, including coaxial and semi-ridge coaxial assemblies, represented approximately $6.8 million in shipments in 2006, and accounted for approximately 6.9 percent of all cable assemblies shipped. Used in all end-use equipment sectors, RF assemblies are most predominate in the telecom/datacom, automotive, and the mil-aero sectors.

Although RF assemblies are manufactured through a variety of channels, national market suppliers and large global EMS suppliers presently represent the two largest channels. Connector companies and specialty cable suppliers follow respectively. It is anticipated, as a result of technical efficiency, particularly in the area of transmission system design and performance validation that the greatest growth over the next five years will be in the global automotive specialty manufacturers and connector companies. For connector companies, this is good news. As explained by John Studebaker, Huber+Suhner vice president of sales and marketing, “Having your assemblies supplied by the connector manufacturer offers a great number of advantages. The most important advantage is the level of ability we have to test the completed assembly prior to shipment. Since Huber+Suhner manufactures both the cable and the connector, assemblies are consistently manufactured in accordance with the customer’s specifications and requirements in mind, and then 100 percent tested to assure all (specifications and requirements) are met. This is especially important with the higher digital speeds driving the need for higher frequency in testing connectors.” In addition to extensive testing capabilities, using a connector supplier to manufacture your cable assemblies also eliminates logistics issues, the need for capital equipment expenditures or personnel training, and can alleviate inventory issues.

The primary function of an RF cable assembly is to channel an RF signal from one source to another source, with as little as possible change in the signal. Although this basically sounds like a very easy task, there are generally a multitude of components involved, all of which affect how well the signal is carried and received at the source. These components include:

• Cable

- Inner Conductor
- Dielectric/Insulator
- Outer Conductor
- Jacket
- Length of the Cable

• Terminated Connector

• Mating Connector

In addition, other factors, such as environmental requirements (ingress protection level, resistance to corrosion, vibration, etc.), ease of use, flexibility, and number of mating/unmating cycles must also be reviewed.

It is not surprising, with all of these components and factors involved, that over the last several years RF assembly manufacturers have changed the way they market their products. Studebaker says, “Not only is there more competition in the commodity products, but there is also a push by target customers to provide local suppliers.” For this reason, many suppliers have set up various operations, all geared towards supporting a specific market or group of customers, in different regions around the world. For instance, Huber+Suhner has established a manufacturing facility on each continent where they have a major customer or where they are serving a major market. It is important to note that this does not preclude Huber+Suhner from utilizing the expertise of one manufacturing facility just because it is not located in a specific area. If after evaluating things, like additional transportation costs, support costs, and access to raw materials, as well as the expertise offered by another facility, the manufacturer finds it is still more cost-effective to manufacture in another location, then that location will be utilized.

RF assembly manufacturers have improved their offerings in the production of test cables for high-performance equipment. Requirements for extreme flexibility and repeated mating and unmating have created a need for this change. One of the ways manufacturers have addressed the need for assemblies that can withstand high cycles of mating and unmating is by using RF connectors with improved surface component plating. Studebaker says, “The ability to maintain low dielectric constant, extreme flexibility, and high mating cycle counts are all driven by plating.”

Surface plating of the connector, in addition to giving the assembly an aesthetically appealing appearance, also addresses the issues of:

• Corrosion Resistance

• Mechanical Strength

• Abrasion Resistance (number of mating cycles)

• Magnetic Properties (PMI)

Although gold, silver, and nickel are still widely used, proprietary platings have been developed by many manufacturers that combine these materials, as well as add additional materials to provide improved plating options. Huber+Suhner’s Sucoplate™ and Sucopro™ are examples of this. As described by Craig Thornton, regional sales manager, “Sucoplate™, which is a tri-metallic plating containing copper, tin, and zinc, is a great alternative to nickel/gold platings. Because of the lack of nickel, it is non-allergenic, a concern expressed more frequently today, and yet offers low-contact resistance, over 1,000 mating cycles, and reasonable corrosion resistance. It is also non-magnetic, so its PIM characteristics are comparable to silver.” For even more abrasion and corrosion resistance, Huber+Suhner also offers Sucopro™, a non-magnetic nickel-phosphorus base material with a thin plating of gold. This unique mix provides for twice as many mating cycles as components with standard gold plating, stable, low contact resistance, and additional protection against oxidation and corrosion.

Within the last couple of years, end-life-product recycling legislation and additional safety requirements have also had an impact on manufacturers of cable. Industry standard RG-type PTFE/FEP cable, although offering excellent overall characteristics, is extremely resistant to decomposition. With regulations initiated mandating that manufacturers recycle products at the end of their service life, the initial and present cost-saving benefits associated with the continued use of PTFE cable, will quickly dissipate. PTFE cables can also create major safety issues. The plastic insulation material on standard RG-type PTFE cables contains halogen. When halogen burns, it gives off highly toxic and corrosive gases. Not only can these gases cause human injury or death, but they can also damage adjoining circuitry.

In response to these issues, manufacturers are beginning to offer products that are not only totally halogen-free, but are composed of recyclable plastics that are not as resistant to decomposition as PTFE, and when incinerated do not produce toxic by-products. Huber+Suhner’s Enviroflex family of cable is dimensionally and electrically equivalent to RG-type cable and can be easily designed into existing RG-type cable applications. Additional benefits include increased flexibility over the relatively rigid PTFE, excellent solderablilty, UL-approval, and the ability to use standard RF connectors.

Other areas of improvement in cable include the use of low-loss flexible cable over standard corrugated copper cables in mobile phone base station applications, where the cost, weight, and low flexibility of copper can create problems. Handformable microwave coaxial cable, like Huber+Suhner’s Sucoform™ cable, which combine the characteristics of semi-rigid cable with the flexibility of coaxial cable, provide space-saving advantages without the use of handforming tools. Improvements have also been made in termination techniques. Techniques have been developed that not only reduce signal lost, but in a time where installation costs can greatly affect the overall assembly cost, more user-friendly semi-automatic tooling has been developed, increasing repeatability, and in turn, reducing errors.

With so many improvements in connector and cable construction, it is not surprising to learn that RF assemblies are anticipated to grow at a CAGR of 8.5 percent over the next five years. What is surprising are the markets and applications that RF assemblies will appear in. Although the use of RF cable assemblies in the telecom/datacom market will continue to grow substantially, with a CAGR of 11.8 percent, markets not traditionally associated with the high use of RF cable assemblies, like transportation and medical, will experience significant growth. As discussed with Huber+Suhner’s Craig Thornton, “RF assemblies are now being used increasingly in SCADA (Supervisory Control and Data Acquisition) systems, in connection with wireless monitoring in oil fields, and on factory floors. You are finding RF assemblies in the medical field, both in general and disposable applications.” Testing is presently underway on the use of radio waves sent via a probe that, once located, would destroy tumors inside the body. In the transportation market, with the use of antennas located atop rail cars, wireless communication between cars, providing not only internal monitoring of conditions, but also providing passengers with a variety of wireless options, is now in use. With the use of wireless communication between cars, the cumbersome job of un-connecting and reconnecting hard-wired railcars when changes are made becomes effortless. This same approach is being used to monitor things like temperature, weight, and other conditions in tractor-trailers. In passenger cars, work is in process to streamline video to cars, and improved sealing- and corrosion-resistance on both connectors and cable have allowed RF assemblies to be used more frequently in shipboard applications.

As indicated in the chart below, for those RF cable, connector manufacturers, and assemblers who are willing to devote time and money into research and new design, the future in RF cable assemblies looks extremely positive.

Lynda Nolen Product Specialist, Bishop & Associates Inc. Lynda Nolen has been in the interconnect industry for over 28 years. She has worked in sales, sales management, marketing, and product management for such companies as TRW Electronics Components Group, Sunbelt Components, Cinch Connectors, Arrow Electronics, PEI Genesis, and Delphi Interconnect. Nolen has extensive experience in competitive cross-referencing, drawing, web and catalog review, new product introduction programs, harness and connector assembly programs, account management, and customer service programs. Lynda received her Bachelor of Arts degree from Roger Williams University in Rhode Island in 1979, and has completed various electrical engineering courses.