Tag Archives: thermal management

The Seven Factors Affecting LED Operating Temperature and Thermal Design

Posted on July 14, 2010 by | Leave a comment

At ATS we’ve done a good deal of basic thermal analysis and thermal design for LED lighting. While the “bulb” of an LED light is generally cool, the electronics to drive that light, behind the LED, are quite hot. Our engineers have identified seven factors that affect LED operating temperature. Engineers developing heatsinks or other thermal management solutions need to consider these:

  1. Input Drive Current
  2. Binning Variations in forward voltage
  3. Steady state, pulsed or conditioned light output
  4. Operating ambient conditions
  5. The degree of solar irradiation
  6. Thermal path (that is, thermal resistance) from the LED junction to ambient
  7. Wattage Output of the LED(s) per dissipating surface area

All of these are key factors that engineers should consider when developing an LED lamp or LED light display thermal management solution.

For more information on how to design a solid cooling solution for LED, our readers are invited to our LED thermal management webinar being held on September 23rd, 2PM. Click to the following link to register, “LED Thermal Management in Commercial and Consumer Lighting Applications“.

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Fujipoly releases new, high performance additions to its Sarcon line of Thermal Interface Material

Posted on June 30, 2010 by | Leave a comment

Fujipoly, a firm we featured in the ATS Thermal Interface Material Resource Roundup, have released a duo of additions to their fine line of Sarcon specially formulated thermal interface materials. Applicable to an aluminum heat sink, copper heatsink or other applications requiring low thermal resistance gap filler pad compounds, Sarcon 100GR-HL and SARCON XR-Um-Al are both available now from Fujipoly.

SARCON XR-Um-Al is a uniquely formulated gap filler compound that has a putty-like consistency. This physical property contributes to the material’s extremely low contact and thermal resistance while maintaining a thermal conductivity of 17 watt/m-k. The gap filler pad is manufactured with a thin aluminum carrier film for customer-friendly application. The low adhesion aluminum barrier enables users to remove the carrier film after installation with no pull-out effect. This thermal interface material is available in sheets up to 50mm x 50mm with thicknesses ranging from 0.2mm to 0.5mm.

SARCON 100GR-HL is a thermal gap filler pad manufactured with a hardened top surface. The unique, one-sided treatment is less tacky than the opposing surface allowing the thermal pad to consistently adhere to either the target electrical component or opposing heat sink. The hard surface allows for effortless removal without tearing or damaging the material during assembly and rework operations. Sarcon® 100GR-HL transfers heat with a thermal conductivity of 2.8 W/m°K and a thermal resistance of .44°Cin2/W at 72.5 PSI. This 1.0mm thick, flame retardant TIM is available in sheets up to 300mm x 200mm.

Thermal interface material is an important part of a thermal management system. So important in fact we’d like to point our readers to a couple of resources we’ve put together here at ATS. The first is our white paper, “When to use thermal interface material with your heatsink and why?” The second is an on-demand webinar we have made available to the thermal engineering community entitled, “Heat Sink Selection Made Easy“, in which we cover a bit about thermal interface material relative to heatsink selection. These materials are free of charge of course. If you’ve got questions or need a bit of help with your thermal engineering, give us a try, companies like Lucent, and Motorola already have. Call us at 781-949-2521 or email us at [email protected]

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Posted in Thermal Interface Material

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ATS Free Thermal Management Webinar: CFD as a Tool to Perform Heat Sink and System Modeling

Posted on June 18, 2010 by | Leave a comment

Computational Fluid Dynamics (CFD) tools have become simulation workhorses, enabling design engineers to tackle electronics cooling challenges on-the-fly. Some tips and tricks are invaluable in performing these analyses. Among them: the simplest methods of preparing a CFD model; the best techniques for meshing; and how to model a system’s components, such as fans and perforated plates. Attendees will learn about common and not-so-common issues in CFD, and how to overcome them.

You can sign up for our free thermal management webinar, being held Thursday, June 24, 2010 2:00 PM – 3:00 PM EDT at this link: “CFD as a Tool to Perform Heat Sink and System Modeling“

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New ATS Thermal Management White Paper: Understanding and Optimizing Thermal Via

Posted on June 16, 2010 by | Leave a comment

Working with challenging design constraints is an ever present problem for board designers. Increasing bandwidths and high clock speeds require that devices be placed closely together for signal integrity. Efforts to avoid signal degradation can have an adverse effect on thermal performance, as high powered devices become more tightly coupled together. In the past, when the power density was significantly less, it was possible to cool devices with a standard PCB. But, as new design and components evolve, the need for high performance heat sinks is accompanied by the need for more intelligent PCB design. A better-designed PCB will enhance heat transfer from a device to ambient through the board. To maintain acceptable junction temperatures, along with reducing the junction-to-ambient resistance through the component case, it is often necessary to dissipate some of the device power through the board. A standard PCB is often designed with electrical performance in mind; however, using thermal vias to improve thermal performance should not be overlooked.  In our new white paper, our engineers discuss just how to do that.   Download your copy here: “Understanding and Optimizing Thermal Via” .

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Is CPU Cooling best done with a Copper Heatsink or Aluminum Heatsink?

Posted on June 16, 2010 by | 1 comment

The topic of whether a CPU heat sink should be a copper heat sink or aluminum heat sink comes up in every thermal management design. And the short answer as to which material to use is:

“It depends.”

There are many variables in designing the right heat sink, some of which include:

  • Thermal management cost budget relative to BOM cost
  • Orientation of boards (vertical or horizontal)
  • How much weight or stress can be applied to the target chip
  • How much keep out around a chip exists
  • Air flow to the chip
  • Air flow in and through the system (maybe you don’t need a heat sink at all as noted in an earlier ATS White Paper)
  • Component dimensions
  • Component height
  • Target junction temperature
  • Target case temperature

Let’s just focus on the material question though, copper heatsink vs. aluminum heatsink. Chris Soule, Engineering Director at Thermshield, has done a nice one page write up on the topic. Some of his key points include:

  • Pure copper has about two times the conductivity of aluminum but that inherent advantage is only helpful when
  1. Air Flow speeds are 800 LFM
  2. The hot spot on the CPU or other semiconductor is small in comparison to the size of the chip itself.
  • When air flow is 400 LFM or lower or the hot spot on the CPU or semiconductor is spread throughout the chip, then Aluminum is a better choice.
  • The cost of a copper heat sink is often up to three times the equivalent sized aluminum heat sink

In our labs here at ATS, we’ve found that if an aluminum heatsink by itself does not have the necessary thermal condutivity, then using phase change thermal interface material (such as those listed in our Thermal Interface Roundup Post) with the proper pressure applied can make the difference in cooling.

So which do you use? Copper or Aluminum? It depends on the variables noted including your budget. One thing is for sure, there is no clear, one sized fits all answer and the thermal engineer should carefully decide. Hopefully before the electrical design is complete!

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Posted in heat sink, Thermal Interface Material

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