Eric Bogatin's Blog: What I Learned This Month

I got a note from John Stolp of Rogers Corp about a new material system Rogers Corp is coming out with called Heatwave. This is an aluminum base material with small silicon carbide (SiC) particles dispersed. The key feature of this new material is that its TCE can be varied from about 5 to 16 ppm/degC, while achiving a thermal conductivity about 1/3 to 1/2 that of copper and being considerably lighter than CuW. This could be used as a lid material for flip chip die, or a substrate base material for sequential build up in GaSa or InP circuits. Its light weight is particulary attractive for aerospace and satellite applications.

On Jan 1, 2008, I was appointed a distinguished lecturer for the IEEE EMC society. I get to go around giving talks on Signal Integrity and EMI to any local EMC society group that invites me. As sort of the kickoff action, Prof Jun Fan of The Missouri University of Science and Technology, formerly UM Rolla, invited me to come down for the day and video tape a few of my lectures.

I presented two lectures, The Ten Habits of Highly Successful Designers, and The Three Most Confusing Topics in Signal Integrity. The slides from both of these talks are available for download on my web site. This was my first chance to use a blue screen in giving a talk and boy was it cool.

It was the first time I could “be the signal” and literally walk along the transmission line on the screen, asking what the impedance the signal sees. If anyone is interested in having me present to their local EMC society group, drop me an email. I can present any of the talks I have on my web site.

I spent a week in Sweden visiting friends recently and visited the Vasa Museum in Stockholm. There is a facinating story behind the Vasa, a state of the art warship built in 1628. I wrote up my SI-Insights column for June about the Vasa and the lessons we can learn in any advanced deevlopment porject from the legacy of the Vasa.

At DesignCon 2008, I ran into Don DeGroot who has started up a new company to perform high bandwidth and high quality measurements using TDR and VNA instruments. I just got a note from him that he has opened up a new web site and has his shingle officially out.

He has a TDR and VNA and analysis software tools and can perform high bandwidth measurements for you, or show you how to do your own measurements. The work he does nicely compliements the content of our Signal Integrity Characterization Techniques class, which we are offering in San Jose on Aug 12-13. If you are looking for measurement services, check out his web site.

This month, I published a paper in PCD&F titled “Don’t let your vias stub their toes“, about how the residual via stub in a thick board, like a backplane, can cause hugh problems in high speed serial links. One way to tame this problem is to backdrill the via stub. In fact, all high speed serial link backplanes use backdrilled vias.

I got a note from Tom Paur of PerfecTest, who told me about a small hand tool they created to test the drill depth of back drilled vias. Here’s an example of it:

Preset, precision pins are inserted into the backdrilled hole and a light idenicates the pass-fail for the drilled hole depth. As backdrilling becomes more common, this is a handy, quick test for the quality of the drill depth without having to cross section the board.

I went to school for 20 years, and earned 3 degrees. I’ve been in industry for 30 years and have made a zillion professional contacts. As I talk to folks, read the literature and explore the web, rarely a day goes by that I am not learning something new. (Unfortunately, as I’ve gotten older, it sometimes feels like as one new item comes in, an old one seems to leave. ;=)

For example, I’ve taught our Essential Principles class about 30 times. Yet, one of the recent times I taught this class, I came to a new realization. It struck me that there is a common belief that a signal exists as a voltage on a line and just sits there. In fact, signals are dynamic and constantly propagate up and down a line. It’s their dynamic nature that gives rise to reflection noise and cross talk. You can’t really solve cross talk problems unless you fully grasp the dynamic nature of signals.

Our new web site has attracted a lot of interest and comments from engineers around the world. I’ve gained new insights and heard about new technologies to help solve signal itnegrity problems from many of my colleagues out there.

This blog is a forum for me to share some of my new insights collected over each month, and a chance for all my fellow signal integrity engineers out there in cyber space to share your comments, questions and insights with me.

Welcome!