A Chinese automobile manufacturer identified an issue with water leaking into the brake light of one of its models, causing short circuits and potentially a fire. The deterioration of the EPDM material originally used to seal around the brake light caused the leakage. As the material aged, its capacity to seal out moisture significantly decreased. Once water entered the brake light housing it flowed downward to the light’s battery located directly beneath the brake light module. At a minimum it would cause a short circuit, in a worst case scenarios it could cause a fire.

The OEM evaluated six options for sealing materials, among them EPDM and rubber. The selected material would have to pass two stringent tests conducted by the OEM; a water-tight test and an assembly test.

The car manufacturer chose Rogers’ BISCO® HT-800 silicone, assured that the material will provide reliable, long-term performance. They also chose to add HT-870, another of Rogers’ silicone formulations, to its material list. Find out more…

Case Study: Rogers Partners with Chinese OEM on Automotive Brake Light Gasket 

Designers can quickly find the silicone material that’s right for their gasketing, heat shield, and sealing applications here: BISCO® Silicone materials.

Unlike the baseball or baseball bat, the baseball glove was initially not part of the game. Back when most of the throwing was underhand, players used their hands. Fast forward to today and it’s a very different ball game. The Guinness World Record for the fastest baseball pitch is 105.1 mph, thrown by Aroldis Chapman for the Cincinnati Reds vs the San Diego Padres on September 24, 2010. Enter the need for impact protection.

Speeds of over 100 mph are not uncommon in baseball, resulting in players often experiencing high levels of impact to their gloves when catching a baseball. The positions of first baseman or catcher receive the largest percentage of throws, so having a glove that provides a high level of protection from such impacts is important to protect the players’ hands and their ability to continue playing in the sport.

Traditional baseball gloves provide limited protection due to the simple materials of leather and wool which do not provide any meaningful shock absorption. One baseball glove manufacturer, Shoeless Joe Ballgloves, needed a way to improve upon their standard gloves. They turned to Rogers XRD® Material to reduce injuries and increase playing time. Here’s how…

Read the Case Study: CONSUMER – Shoeless Joe (PDF)

Designers can quickly find the appropriate XRD Material that fits their sports apparel, equipment, and accessories needs here: XRD Technology Products and Applications.

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This post authored by John Coonrod, Technical Marketing Manager, and team originally appeared on the ROG Blog hosted by Microwave Journal.

Much of the buzz on the show floor at the 2017 IMS in Honolulu was about millimeter-wave devices and circuits. At one time, frequencies above 30 GHz were considered “exotic” and only for military or scientific applications. But times have changed, and available spectrum is scarce. Millimeter-wave frequencies are now used in commercial vehicular radars, and big plans are being made for these small wavelengths in Fifth Generation (5G) wireless communications networks, in support of moving massive amounts of data quickly. More and more design engineers are faced with developing practical millimeter-wave circuits to 77 GHz and beyond. But first, they must decide upon the best transmission-line technology for those high frequencies as well as the circuit material that can support those circuits with quality, low-loss signal propagation. Drivers and cell-phone users everywhere will be counting on them!

At microwave frequencies, microstrip is by far the most popular transmission-line technology, compared to stripline and coplanar waveguide (CPW). It has a signal plane on the top copper layer and bottom ground plane. It is relatively simple and cost-effective, and allows surface mounting of components for ease of construction.

Unfortunately, as signal frequencies move into the millimeter-wave range, microstrip circuits can behave like antennas, radiating electromagnetic (EM) energy away from a desired signal propagation path and resulting in much higher radiation losses than at lower frequencies. Microstrip radiation losses are also dependent upon the thickness and dielectric constant (Dk) of the circuit substrate material. Thinner substrates suffer less radiation loss than thicker substrates. Also, circuit materials with higher Dk values have less radiation loss than circuit materials with lower Dk values.

In microstrip, the effective Dk is a combination of the Dk of the substrate material and air, since EM waves in a microstrip transmission line propagate in part through the dielectric and in part through the air above it. In contrast to microstrip, stripline is like a flattened coaxial cable. It consists of a conductor surrounded by top and bottom dielectric layers which in turn are covered by ground planes. The Dk of stripline is the same as that of the dielectric material, since air is not involved in the propagation process.

CPW circuits are fabricated with a number of variations, including as standard, grounded coplanar waveguide (GCPW), and conductor-backed coplanar waveguide. Standard CPW metallizes parallel conductors (in the form of a flat waveguide) on the top of a dielectric layer, with ground metal areas just beyond the conductors. GCPW adds a bottom ground-plane layer but requires plated-through-hole (PTH) viaholes through the dielectric substrate material to connect the top and bottom ground planes. The extra ground planes on the top copper layer helps GCPW achieve high isolation between signal lines and can be designed to minimize spurious wave propagating modes. Placement of the PTH viaholes is critical, and can impact transmission-line impedance and loss.

Like microstrip, GCPW has an effective dielectric constant as the result of EM waves propagating through the dielectric material as well as through the air around the conductors. GCPW, like microstrip, also allows surface-mounting of components for ease of fabrication, in contrast to stripline where PTH vias need to connect the components on the outer circuit layers to the inner signal layer. In terms of millimeter-wave frequencies, GCPW has lower dispersion than microstrip, with less radiation loss, and is capable of supporting higher-frequency propagation than microstrip circuits. GCPW also achieves more effective suppression of spurious propagation than microstrip, and is more amenable to practical signal-launch configurations (such as from waveguide, cables, and connectors) at millimeter-wave frequencies than microstrip.

Finding the Right Circuit Material

If GCPW is the optimum transmission line for millimeter-wave circuits, it should then be fabricated on a circuit material with optimum characteristics for millimeter-wave frequencies. Since signal power tends to decrease with increasing frequency, an optimum circuit material for millimeter-wave circuits should have low loss at those high frequencies. The insertion loss of millimeter-wave transmission lines is due mainly to the aforementioned radiation losses, conductor losses, and dielectric losses. Radiation losses tend to be design-specific, whereas conductor and dielectric losses will depend upon the choice of circuit material.

Dielectric losses are a function of the type of dielectric material, and usually well defined by a material’s dissipation factor (Df), with lower values indicating lower dielectric losses. A circuit material capable of consistent performance at millimeter-wave frequencies will also exhibit minimal variations in Dk, so that dielectric losses do not change dramatically with frequency.

In considering circuit materials for millimeter-wave circuit applications, the thermal coefficient of dielectric constant (TCDk) parameter provides reliable insight into the stability of a material’s Dk with temperature. The TCDk parameter provides an understanding of what to expect of a particular circuit material’s performance at millimeter-wave frequencies, with lower TCDk values indicating less change of Dk with temperature and less variations in frequency phase response resulting from variations in Dk with temperature.

Conductor losses can be traced to a number of variables at millimeter-wave frequencies, including the surface roughness of the copper conductors and the choice of plated finish for the conductors. Copper is an excellent conductor, but increasing surface roughness results in increasing conductor loss and greater propagation phase delays. The main area of concern for copper surface roughness is at the copper-substrate interface, with conductor loss due to the copper surface roughness increasing as a function of increasing frequency. The small wavelengths of millimeter-wave signals result in less skin depth in the circuit material as part of EM propagation, and circuit materials with greater copper surface roughness will more severely impact the insertion loss and phase response at millimeter-wave frequencies. The effect of copper surface roughness on insertion loss is also dependent upon the thickness of the circuit material, with thinner circuits affected more by copper surface roughness than thicker circuits.

At millimeter-wave frequencies, circuit materials with excessive copper surface roughness will have more impact on the conductor loss of microstrip circuits than on the conductor loss of GCPW circuits. Switching to a circuit material with smoother copper finish will bring less of an improvement in conductor-loss performance for a GCPW circuit than for a microstrip circuit, especially at millimeter-wave frequencies. In particular, tightly coupled GCPW circuits, which feature closely spaced conductors and ground areas, are less subject to the effects of copper surface roughness than loosely coupled GCPW circuits (with greater spacing between conductors and ground).

An optimum circuit material for millimeter-wave circuits should cause minimal phase angle variations, since such behavior can be critical to many millimeter-wave applications, such as 77-GHz vehicular radar systems. By minimizing variations in certain material-based attributes, such as copper thickness, Dk, conductor width, and substrate thickness, variations in phase angles can be minimized at millimeter-wave frequencies.

Additional details on finding the right combination of circuit material and transmission-line technology are available as part of the Microwave Journal webinar, “Design Considerations and Tradeoffs for Microstrip, Coplanar and Stripline Structures at Millimeter-wave Frequencies,” presented by John Coonrod. 

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Power electronics is changing rapidly. New packaging technologies are facing a rise in chip temperatures as seen in such applications as EVs / HEVs. Electronics increasingly need longer lifetimes to function in harsh conditions, such as wind turbines. Power electronics based on SiC components need to handle faster switching in the face of higher temperatures. While beneficial, the challenge is that these changes produce considerable stress on power systems and, consequently, result in reliability problems.

Traditional power module designs were primarily based on Al2O3 or AlN ceramics. But the need for higher performance is leading designers to choose more advanced substrates. substrates with Si3N4 ceramics use the excellent bending strength, high fracture toughness, and good thermal conductivity of Si3N4 to build substrates that can handle a variety of today’s challenges.

In the following video, the Power Electronics Solutions team at Rogers takes a look at how to make the right substrate choices to support demanding applications.

VIDEO: 3 Steps to Select the Right DBC / AMB Ceramic Substrate for Your Application

In this video, Olivier Mathieu, Product Innovation Manager, discusses how to use the latest substrates in power electronics designs. He walks us through: (a) How to select the right ceramic thickness and its influence on basic isolation voltage, (b) How to select the right ceramic grade and its influence on heat removal, and (c) How to select the right copper thickness and its influence on functional isolation, ampacity, and heat removal.

Watch the video, Selecting the Right DBC / AMB Ceramic Substrate.

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The end of summer is right around the corner in the Northern Hemisphere with the Autumnal Equinox on September 22nd. Happy Spring Equinox to all of you in the Southern Hemisphere 🙂

Did you know that equinoxes are not daylong events? They actually occur at the exact moment the Sun crosses the celestial equator, the imaginary line in the sky above the Earth’s Equator. At that instant, the Earth’s rotational axis is not tilted with respect to the Sun. In 2017, the Sun crosses the celestial equator from north to south on September 22nd at 20:02 UTC. Parts of Australia, New Zealand, and Russian will experience it on September 23rd due to time differences.

In the meantime, Rogers Corp. has had a busy summer. The Rogers Germany team won the Bosch Preferred Supplier of the Year Award. Congrats!

Rogers Elastomeric Material Solutions/Asia held their Preferred Partners Conference in July in Phuket, Thailand. About 140 people from 52 companies were in attendance. The conference theme of “Winning Partnerships” aptly describes the collaborative relationship between Rogers and its customers — partnering and working together to secure business.

Of course, there were also a few BBQs along the way, with happy, smiling Rogers employees around the world.

Evergem, Belgium

Rogers, Connecticut, USA

Eschenbach, Germany, Interns


 
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