This post authored by John Coonrod originally appeared on the Rog-Blog hosted by Microwave Journal.

Dielectric constant (Dk) is one of the most essential of printed-circuit-board (PCB) material parameters. Circuit designers rely on it for determining such things as impedances and the physical dimensions of microstrip circuits. Yet, it is not unusual to see a laminate data sheet with different values of Dk for the same material, such as a process Dk and a specification Dk. A material supplier may even recommend an additional value of Dk, to be used in computer-aided-engineering (CAE) software simulators. Why all the different numbers and is there one value of Dk that is the one to trust when designing a circuit?

As detailed in the last several blogs, there are more than a few ways to determine the Dk of a microwave laminate, and these different measurement methods often yield different results for the same material. Some of the measurement techniques are based on the use of “raw” PCB materials—without circuits on them—while some of the methods use a well characterized circuit with predictable performance to then determine the Dk for the material. Materials suppliers may use terms like “process Dk” to refer to the target value for the material when it is being processed, and “specification Dk” to mean a value determined by means of one or more of the measurement methods described in the two previous blogs. Often, the process and specification Dk values are the same for a given laminate.

A more meaningful version of Dk is the “Design Dk” that is currently published in the Rogers’ Product Selector Guide and serves as the values for Dk in the MWI-2010 Impedance Calculator, available for free download (note that it does require sign-up). The Design Dk is a value that provides the most accurate and repeatable results when used for circuit design purposes, notably in commercial CAE circuit and system simulation programs.

For some materials, the process or specification Dk may have the same value as the Design Dk. For Rogers’ popular RT/duroid® 6002 microwave laminate, for example, the process Dk and the Design Dk are both 2.94 in the z-axis. One difference is that the process Dk is specified at 10 GHz on the data sheet, while the Design Dk is given for frequencies from 8 to 40 GHz. The values were determined using two different test methods.

At the same time, the Dk values may differ appreciably. Rogers RO3010™ laminate has a process Dk of 10.2 in the z-axis at 10 GHz, but a Design Dk value of 11.2 is recommended for use with commercial CAE software simulators for more accurate modeling purposes.

If process and specification Dk values are determined by measurements, why should there be a need for a “Design Dk” value? As mentioned in the previous two blogs, there are many test methods for determining the Dk of a laminate. As an example, the global trade organization IPC lists 13 different test methods to determine a material’s Dk. Materials suppliers use any number of these measurement methods for their own determinations of Dk, while laminate users may have their own, and different, methods for determining the Dk of a laminate before using it for design purposes. In the two materials mentioned above as examples, a different measurement was used in each case to find the process/specification Dk and the Design Dk: the clamped stripline method was used for the process/specification Dk and the differential phase length method was used for the Design Dk.

Within Rogers, for example, the X-band clamped stripline resonator test is used for standard quality assurance (QA) testing of specification or process Dk, although the full-sheet-resonator (FSR) measurement method may also be used for QA testing. The split post dielectric resonator (SPDR) method may also be used to characterize materials within Rogers. For determining the Design Dk, the microstrip differential phase-length method will be used for all materials.

While none of the test methods is ideal, the differential phase-length method is elegant in its simplicity. It relies on fabricating two microstrip circuits of significantly different lengths on the same laminate material, using the same connectors or test fixture to determine the phase angle differences between the circuits for a given test frequency. A value of Dk can be determined from simple calculations based on the differences between physical lengths and phase angles. The process is repeated for as many frequencies as is practical. It is not a fast method, but it does provide accurate results for Dk in the z-axis, with anisotropic material effects (Dk values in the x and y axes) having little impact on the measurements.

This test method uses microstrip circuits commonly used in actual applications. It is also performed at the high frequencies often used in applications, to account for “copper effects,” in which a laminate with rougher copper surface can test for a higher apparent Dk value than a laminate with smoother copper surface. Test methods using lower frequencies may not reveal the effects of the copper roughness on measured Dk value.

The Design Dk values have been determined for all of Rogers’ high-frequency laminates and are being reported to all major developers of CAE simulation software tools. In addition, those values are now included in the MWI-2010 Microwave Impedance Calculator, the Product Selector Guide, and in the Slide Rule published in the November 2010 issue of Microwave Journal.

Tagged with:  

Need help determining which Rogers foam material to use for a specific application?

Check out our latest Industrial High Performance Foams Material Selection Tool,  a design tool intended to guide those unfamiliar with the breadth of solutions that PORON® Urethane and BISCO® Silicone materials can offer.

To learn more about using this tool, check out this video:

Access the tool by clicking on the image below:

Material Selection Tool by Rogers Corp

We are committed to helping our customers help solve their design challenges and try to make it easier to use our materials by developing a series of design tools.  Check out our PORON Urethanes Gap Filling Tool that helps engineers select materials which will fill both large and small spaces, such  as smart phones or industrial enclosures, or the Silicone Material Selection Guide for choosing the right silicone product for your application.

Tagged with:  

At the Materials, Manufacturing & Technology (MM&T) conference sponsored by the Asia-Pacific Leather Fair (APLF) held in Hong Kong, we were excited to learn that PORON® XRD™ extreme impact protection material was recognized with the “Best Component Award”.  The Rogers’ team was one of only five exhibitors honored with a materials-related award at the show.

PORON XRD Extreme Impact Protection material is a high-performance technology that continually surpasses the competition for impact absorption in a thinner, lighter-weight, contouring material.   While soft and flexible to the touch, the material instantly forms a protective shell on impact, providing reliable and long-lasting protection.

“PORON XRD Material has been a very successful addition to our PORON Cushioning family of products and has been incorporated in a variety of applications from footwear to helmets and back protectors,” said Vicky Zeng, Rogers Corporation Sr. Marketing Communications Specialist-Asia.  “We are honored to receive the recognition and prestigious award from APLF.”

Read the full press release on our PORON Cushioning Blog

Tagged with:  

Our very own Tom Sleasman from the newly formed Power Electronics Solutions Group was interviewed by Cliff Keys, Editorial Director at Power Systems Design while out at the PCIM Europe 2011 last week.  Tom explains some of the exciting developments happening at Rogers lately, starting with his new division which now combines three key areas of power electronics in Rogers:

Tom explained that the core of all Roger’s Power Electronics products are designed “to get rid of the heat” in power components.  He went on to discuss Roger’s plans in the Hybrid and Electronic Vehicle (EV) markets.  Rogers is already working on an advanced power generation product for release in 2015 – with a goal to reduce weight, size and increase power density so that Hybrids and EVs can be affordable and an option for anyone who wants one.

Hear more about what Tom has to say in this interview…

A special thanks to Cliff Keys and Power Systems Design!

By Human Resources Department, Rogers Corporation

Relay for Life

Relay for Life 2011

Rogers Corporation is participating in the Northeastern Connecticut Relay for Life for the third year in a row!

This year, we’re working towards our goal of $5,000 with a series of community events and fundraisers.  We had another successful year hosting a local Princess Tea, raising over $1,300.  We contributed to the Relay Goods & Services auction, providing a Nantucket Experience which included a plane ride, overnight stay, and dinner on Nantucket Island.  Current fundraising events include the sale of Terri Lynn gourmet nuts and treats, basket drawings and an upcoming bowling tournament.

The Relay for Life gives Rogers the opportunity to honor those in our community who have been touched by cancer, and to ensure that their struggles are not forgotten.

Take a moment to consider why you relay.  Whether it’s to support a friend or relative, to honor a loved one who’s been lost, or to give thanks for those who are healthy in your life, Relay is a chance to celebrate, remember, and fight back.

“The American Cancer Society Relay For Life represents the hope that those lost to cancer will never be forgotten, that those who face cancer will be supported, and that one day, cancer will be eliminated.”

Together, we can help to make our community a healthier place for today, tomorrow, and beyond!

Do you have an idea for an event or fundraiser?  Share it with our Rogers Community Network team (RCN)!  You can go to and join the Rogers’ team today.

Page 70 of 77« First...102030...6869707172...Last »