Tag Archives: push pin

What is The Thermal Performance of Straight Fin, Pin Fin and Other Heat Sink Geometries?

Posted on March 27, 2014 by | 23 comments

This article discusses the effects of air flow velocity on the experimentally determined thermal resistance of different heat sink designs. To be able to compare these designs, we need to first review basic heat transfer theory as applied to heat sinks. Previously published work is discussed, along with heat sink selection criteria.

A device’s temperature affects its operational performance and lifetime. To achieve a desired device temperature, the heat dissipated by the device must be transferred along some path to the environment [1].  The most common method for transferring this heat is by finned metal devices, otherwise known as heat sinks.

Resistance to heat transfer is called thermal resistance. The thermal resistance of a heat sink decreases with more heat transfer area. However, because device and equipment sizes are decreasing, heat sink sizes are also growing smaller. On the other hand, device heat dissipation is increasing.  Therefore, designing a heat transfer path in a limited space that minimizes thermal resistance is critical to the effective design of electronic equipment.

thermal peformance of straight fin heat sinks

The heat transfer rate of a heat sink, Q-dot, depends on the difference between the component case temperature, Tc, and the air temperature, Ta, along with the
total thermal resistance, Rt. This relationship is shown in Equation 1. For a basic heat sink design, as shown in Figure 1, the total thermal resistance depends on the sum of the heat sink resistance, Rhs, the spreading resistance in the heat sink base, Rsp, and the thermal interface resistance from the component to the heat sink base, Rtim, as shown in Equation 2.

heat transfer rate equationEquation (1) and Equation (2)

Therefore, to compare different heat sink designs, the thermal interface resistance, RTIM, and the spreading resistance, Rsp, was similar among the heat sinks tested.

For this study, the same thermal interface material (TIM) was used with all heat sinks. This minimized the difference in the thermal interface resistance, RTIM, between heat sink tests. As is normal, the spreading resistance of a heat sink’s base, Rsp, increased with decreasing base thickness and conductivity. It also increased with an increasing difference in the heat sink base area and the heat dissipation area [2].  To read the full study and recommendations, please click here for the PDF.  No cost or registration is required.  Also, ATS has a family of straight fin heat sinks for sale, with dimensions from 15mm to 45mm in length, 15mm to 45mm wide, and 9.5mm to 4.5mm high, see them all here:  ATS Push Pin Heat Sink Family.

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Which Heat Sink Family Is Designed For A Wide Array of Spring Compression and Air Velocity Applications?

Posted on March 19, 2014 by | 1 comment

Alot of thought went into creating the ATS line of Push Pin Heat Sinks.  Some of the key questions that were considered included:

  • How do we create a heat sink family where a set of applications might be either low air flow or high air flow?
  • What type of environments, including shock and vibration, will a given application have and how do our engineers insure the right compression springs and hardware for a wide range are available.
  • What are the widest array of semiconductor package sizes that we will need to be accommodate?

The Push-Pin 2-minute video gives a quick overview of the product line with these key design points in mind:

Also available through Digi-Key!

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Why Blue and Green Color Anodization for Push Pin Heat Sinks?

Posted on March 18, 2014 by | Leave a comment

ATS’s push pin heat sink line has a number of important characteristics but you’d think the least of them would be their color.   Why the colors and how do they help heat sinks be better heat spreaders – or do they?

First off, why the colors?   Are they there for marketing purposes or do they have a more engineering centric mission?  The colors are actually part of the anodization itself.    But first what is anodizing?   The Aluminum Anodizers Council has the key definition:

Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized.

But most heat sinks are themselves inside electronic systems such as computers, telecommunications equipment.  Any electronic component that generates heat can benefit from a heat sink (also known as a heat spreader).   So, do heat sinks inside computers need to be protected by anodizing them?  The short answer is no.  There are use cases of course but in general, protection is not the reason heat sinks in general (and ATS’s Push Pin line of Heat Sinks) are anodized.  In many cases the anodization color makes it easier to brand the heat sink from a particular manufacture or to distinguish between different branches of a heat sink family.  In the case of ATS’s Push Pin Line, the green anodized heat sinks use ATS’s  ultra performance maxiFLOW™ fin geometries while the blue anodized heat sinks feature straight fin or cross-cut fin designs.

So anodization is just about marketecture?   Well, no.  While the colors are convenient and helpful the real answer is a technical reason.  As we’ve noted in our 2010 article series, “How Heat Sink Anodization Improves Thermal Performance (see them on qats.com at these links, part 1 and part 2)”  anodization is about treating the surface of the heat sink to improve the radiation heat transfer of the heat sink:

Radiation heat transfer can be as important as convection heat transfer in electronics cooling, especially in natural convection and low-airflow applications.  Depending on the type of surface treatment used, radiation heat transfer is enhanced in two distinct ways: by increasing the emissivity of the surface or by increasing the surface area.  Anodization is one such way to treat the surface area.

Various protective benefits and aesthetically pleasing colors have extended the use of anodization to many industrial and commercial applications. For electronics cooling, however, the advantages of surface anodizing are the dielectric isolation of the cooling components from their electronics environment, and the significant increase in their surface emissivity. The increase in the emissivity coefficient on the anodized surfaces of heat exchangers, electronics cabinets and enclosures, heat sinks, etc. is typically on the order of 0.83 to 0.86 [4]. When compared to the emissivity coefficient of bare aluminum, 0.04 to 0.06 [5], the importance and significance of enhancement of radiation heat transfer would become evident.

So for ATS’s push pin heat sinks and for other firms who anodize their heat sinks the reason is really for the purpose of improving the thermal performance of the heat sink.  Also available through Digi-Key!

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