I love gadgets but I hate cables – they make things so untidy. As a result, anything that can go wireless in our house has – even our light switches are on remote control. I used to think this was just plain silly when we were going through the retrofit until I realized I could turn off the kitchen lights from the comfort of our sofa. I’ve only used this “power” once but I tell you knowing that I can do it any time I wanted is priceless!
Wireless gadgets are everywhere around us … PDAs, game controllers and mobile phones. Looking around our living room I can see 9 wireless devices (and that’s just one room). We are so used to relying on these devices that we no longer stop to think about what goes into making sure those devices work when you really need them. Ok so I won’t be in a world of pain if my wireless PS3 controller stops working in the midst of a Tekken fight tournament. But I could be in real danger if my car breaks down on the freeway and I can’t call for help because my mobile phone has stopped working due to interference from an outside source. Have you even tried finding a landline phone anywhere lately?
Thankfully there are mobile/wireless device manufacturers who do think about these kinds of issues. Normally, in this blog we talk about all matters relating to fluid flow and thermal but I thought it would be nice to expand the realm for this week to electromagentic interference shielding (EMI) as well.
Due to the reduction in electronics form factors and the need to include more and more radios into each device, many OEMs have started to combine EMI and thermal solutions into single assemblies. As expected, this combination introduces additional complexities in the thermal design process such as the need for multiple layers of thermal interface materials whose performance interacts with each other. Most recently, one of our clients, Laird Technologies, had a project encompassing just such a scenario. Laird Technologies designs and manufactures customized, performance-critical products for wireless and other advanced electronics applications. The company is a global market leader in EMI shielding, thermal management products, mechanical actuation systems, signal integrity components, and wireless antenna solutions, as well as radio frequency (RF) modules and systems across a wide variety of industries including IT/telecommunication, medical, automotive, consumer electronics as well as military/aerospace.
Most recently the Laird Technologies engineering team worked with an OEM customer on a custom solution consisting of a printed circuit board with a heat source and an EMI shield consisting of a metal plate that also serves as a heat spreader. The heat source is separated from the EMI shield by a layer of thermal interface material. The heat sink is mounted to the EMI shield and separated from it by another layer of thermal interface material. As you can see it is a complex design. As a result, many design parameters can be modified thus increasing the number of design alternatives that must also be considered in an effort to achieve an optimized solution.
Shahi Riaz, Thermal Develoment Engineer at Laird, used FloTHERM CFD simulation software to learn more about the performance of their initial concept. The first model allowed the heat source package temperature to exceed the maximum value of 90° C which was above specifications. So Mr. Riaz used FloTHERM’s design optimization functionality which enables the software to automatically vary parameters such as the number of heat sink fins, fin thickness, base thickness and more. One of the parameters considered was cost which was applied implicitly by setting absolute limits on particular variables. Through this process Mr. Riaz explored the entire design space and reduced the package temperature by 13° C and brought the device within accepted design guidelines. What really made me stand up and notice was the fact that the design was optimized in only a few days compared to the weeks it would have taken to run iterations while changing one variable at a time. But we’re not done yet! When the hardware prototype was built, its thermal performance closely matched the simulation predictions. And that’s what we like – fewer respins and faster design translates into higher productivity and cost savings for everyone involved. BTW, the thermal/EMI solution is now in manufacturing and the customer feedback is very positive.
There’s a lot more to this story so if you’d like to read more technical details about Mr. Riaz’s design as well as learn more about Laird Technologies please follow this link.
Until next time,
PS. Happy Easter everyone!