Ken Kozicki from our BISCO division recently led a discussion with one of our resellers, the Grogan Group (based in Australia), that highlighted some key design considerations for engineers when it comes to choosing seat cushion materials in rail cars. Ken highlighted the differences between Rogers MF-1 silicone foam for seat cushions vs. typical molded polyurethane cushions and their advantages for rail and transit authorities.  Fortunately the discussion was videotaped (thanks to the folks at Grogan Group!) and you can watch it at your leisure.   However we wanted to capture some of the key points Ken made during his talk.  He shared that while silicone foam is a bit more expensive than polyurethane materials, there are some intangibles that need to be considered:

About Molded Polyurethane Seating

Typical seating cushions in rail cars are a molded polyurethane that has a low performing compressibility rate when it comes to cushion comfort.  What this means is that a polyurethane seat wears out quicker over time, and it loses its “spring-back” force that helps make the seat comfortable.  Over time the foam actually shrinks and flattens out, the upholstered material covering the cushion stretches out, gets loose, and the seat’s comfort declines as more passengers sit on it.  This material also needs to be treated with fire retardant chemicals, which adds to the production cost.

About Silicone Foam

The production of silicone foam is a more sensitive process than polyurethane.  There are precise control factors that come into play when manufacturing silicone foam because it creates a chemical reaction, and if the recipe is slightly off or there is added humidity or temperature changes, it can change the nature of the end product and be out of spec ranges.  This complex process tends to keep the price higher than polyurethane when comparing the two materials side by side.

But on the flip side, silicone foam has many advantages that polyurethane does not.  It will not lose its “spring-back” force, and does not require fire retardant treatment.  And, the issues that happen with molded polyurethane don’t happen here:  the upholstery doesn’t loosen, the seat does not lose shape from long wear and the cushion does not shrink in height.  As a result, the life of a silicone foam seat cushion is much longer (getting back to those intangible benefits).  There is also less repair and refurbishment costs for a transit authority (and these are very tangible benefits).

To learn more about Rogers MF-1 Silicone Foam and how it provides better, long-lasting comfort in rail car seating, sit back and watch the video:

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We are always on the lookout for interesting engineer communities, and we recently found one by following the Twitter stream just after DesignCon 2011 ended.  The community we found was the SemiWiki project, a few folks from DesignCon had shared their trip reports from the show.  The community  is described as:

The SemiWiki Project provides in-demand content for semiconductor design and manufacturing, facilitating peer-to-peer communications using Web 2.0 technologies.

This group is serious about collaboration and creating a valuable community for semiconductor engineers.  What is cool is that they are running a contest to encourage and reward participation for becoming a “top influencer“, and the prize is an Android Tablet.  Winners will be revealed at the Design Automation Conference (DAC) June 5-12 2011 so there is still time!  There is a running list of those “influencers” with their points accumulated so far. Nothing like a little competition!

Beyond encouraging participation, this appears to be a growing, active community with Forums, various Wikis that includes a wealth of information being shared. Check it out if you’re a semiconductor engineer…

SemiWiki Project

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This post is by the Human Resources Department, US Career Center

As a business or engineering professional, you are most likely already an active member of a social network or a professional group online. Over the last few years, the number of online networking groups has grown exponentially. On LinkedIn, for example, there are currently more than 480,000 groups for professionals. Facebook and Twitter also offer opportunities to connect with peers by joining professional interest groups.

How you decide which online group to follow and to contribute your ideas to the discussions? What are specific benefits of joining a group?

  • Follow Your Interests: Social networking sites allows to search for groups by interest, location, membership (public or by invitation). Decide on key areas that interest you and start searching for online discussions that are currently happening in your field.
  • Content & Quality:  Signing up to a new group is easy. Membership in too many groups could be overwhelming. Before joining, scan for the selected group’s member base, content quality and frequency of postings. You might find that a certain group has a lot of members; however, it is not very active. Other groups might have an overwhelming number of posts that are irrelevant to the topic and purpose of the group.
  • Focused Discussions: Networking groups focused on specific topics and/or industries allow finding subject matter experts, connecting with companies offering products and services in your industry. You might find niche networks that are very active in your particular market and target industry.
  • Affiliations: Many industry associations and publications have established professional networking groups online. You might find it easy to connect with people who are already engaged in the same membership organizations as you and your company.

For example, if you are a member of IEEE, you might find many peers and colleagues who have already joined IEEE’s social networks online.

For Microwave Journal readers, the publication offers participation in the RF and Microwave Community LinkedIn group, which now has over 4,500 working professionals in engineering, management, sales & marketing.

Another example of a successful community is the EngineeringExchange, an online portal connecting engineering professionals from all over the word. It is administered by the DesignWorld publication. Over 50 groups provide active discussions on engineering subjects – from green engineering to manufacturing topics.

We would like to hear your stories about online groups and networks you found interesting. Which ones would you recommend joining?

The ACM Division of Rogers introduced two new laminates to the market at the IEEE Radio & Wireless Week Expo. The new products are geared for design engineers who need high speed or reliability for double-sided or multi-layer printed circuit boards (PCBs).  The new products are:  XT/duroid™ 8000 series high performance, halogen-free thermoplastic laminate materials and RT/duroid® 6035HTC high thermal conductivity laminates.

Let’s break this down a little…

About XT/duroid 8000 Series Thermoplastic Laminates

XT/duroid8100

XT/duroid 8100

The 8000 series covers the range for simple multilayer designs, up to 6 layers or more.  Both dielectric constant and dissipation factor are stable over a wide range of frequencies.

Features:

  • Thermally stable design with a melt temperature higher than PTFE materials
  • Stable dielectric constant and dissipation factor over a wide frequency range for high reliability and uniform electrical properties over frequency
  • Higher operating temperature and can be used in applications where high temperature stability is necessary
  • Excellent chemical resistance for ease of processing, and resistant to solvents and reagents used to process circuit boards.
  • Environmentally friendly, Halogen free, is inherently flame retardant, Lead-free solder capable with low smoke/toxicity

Typical Applications:

  • Flex-to-install applications
  • Conformal circuitry
  • Lightweight feed manifolds
  • Oil and gas exploration
  • Semiconductor burn-in

Visit the ACM web site and download data sheets for the XT/duroid 8000 and 8100 laminates

About RT/duroid 6035HTC Laminates

RT/duroid 6035HTC high frequency circuit materials are ceramic filled PTFE composites for use in high power RF and microwave applications. With a thermal conductivity of almost 2.4 times the standard RT/duroid 6000 products, and copper foil (ED and reverse treat) with excellent long term thermal stability, RT/duroid 6035HTC laminates are an exceptional choice for high power applications.

Features:

  • High thermal conductivity with improved dielectric heat dissipation, enabling lower operating temperatures for high power applications
  • Low loss tangent for excellent high frequency performance
  • Thermally stable low profile and reverse treated copper foil for lower insertion loss and excellent thermal stability of traces
  • Advanced filler system that improves drillability and extended tool life compared to alumina-containing circuit materials
RT/duroid 6035HTC Laminates

RT/duroid 6035HTC Laminates

Typical applications:

  • High power RF and microwave amplifiers
  • Power amplifiers, couplers, filter, combiners and power dividers

Visit the ACM web site and download data sheets with comparison charts for RT/duroid 6035HTC High Frequency Laminates

For more information, visit ACM High Frequency Laminates.

This post authored by John Coonrod originally appeared on the RogBlog hosted by Microwave Journal

Microstrip or stripline? That choice has been faced by high frequency designers for decades. Both transmission-line technologies are widely used in both active and passive microwave circuits, with excellent results. Is one approach better than the other? Before tackling such a question, it might help to know how each transmission-line technology works and what kind of demands each place on a printed circuit board (PCB) material.

Microstrip is a transmission-line format in which the conductor is fabricated on a dielectric substrate which itself has a bottom ground-plane layer. Conductors are usually formed by etching away unwanted metal from a conductor layer, such as copper.

Stripline is often compared to a flattened coaxial cable in that, like the cable, it consists of an inner conductor completely surrounded by dielectric material which is itself surrounded by a ground braid or foil. Of course, stripline circuits are planar, so that they appear as a sandwich of conductors in the middle, surrounded by dielectric layers, which in turn have parallel ground planes on the top and bottom.

Continue reading the full article on the Rog-Blog

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