THIN FILM Innovative Technology

Innovative Technology THR-UM-THIN FILM THERMOELECTRIC 1212 Any information furnished by Laird Technologies, Inc. and its agents is believed to be accurate and reliable. All specifications are subject to change without notice. Responsibility for the use and application of Laird Technologies materials rests with the end user. Laird Technologies makes no warranties as to the fitness, merchantability, suitability or non-infringement of any Laird Technologies materials or products for any specific or general uses. Laird Technologies shall not be liable for incidental or consequential damages of any...

Revision History Revision 1 Description 8/30/2012 – Initial Version Laird Technologies

Thin Film Thermoelectrics As components, packages and systems continue to shrink in size, the heat generated in these dense electronic systems can be quite large and can lead to a significant rise in temperatures that in turn can cause device and system-level failures. Heat has always been an issue for system designers, but only recently has the problem become so severe that thermal management solutions can no longer be introduced as an afterthought. Thermal management must be considered from the beginning of the design process in order to avoid causing severe problems at the system level. This...

Advantages of Thin Film Technology Conversely, thin film thermoelectrics target the source of the heat flux to provide thermal management and control. These embeddable TEMs use semiconductor processing techniques to create a nano-structured thin film used for the P and N legs. Thin film TEMs are typically 5 to 20µm thick, versus 200µm for conventional bulk TEMs, resulting in several differences. The heat flux, which is inversely proportional to the thickness of the thermoelectric material, is more than 20 times greater than bulk TEMs. Thin film TEMs can also pump a maximum heat flux of 100 to...

System Level Considerations The TEM, being an active thermal device, creates a thermal inversion that dramatically changes the thermal profile inside the package. Figure 3 shows a comparison of the thermal profile through the cross section of the module in two cases, a) with no TEM, or in other words, a passive solution only, and b) with a TEM actively cooling the junction. It can be clearly seen that the introduction of the TEM provides a substantial net cooling benefit. Figure 3: Temperature profiles through the cross section of a package from the junction to the case (θJC), and case to ambient...

Thin Film Thermal Management Design In order to understand the design challenges facing engineers in the electronics industry, we need to first look at the way heat moves or flows through a material system, and to do this we need to look at the forces that govern that movement. Heat has always been an issue for system designers, but only recently has the problem become so severe that thermal management solutions can no longer be introduced as an afterthought. Heat flux must be looked at from the beginning of the design process. Heat flowing through a material will always create a temperature...

Passive Cooling The primary systems used for passive cooling of electronic and optoelectronic systems are materials configured as thermal interface materials (TIM), heat spreaders and heat exchangers. Each perform a different function for removing heat from a system. Heat exchangers may be an environment (e.g. liquid or air) or object that absorbs and then dissipates heat while in physical or thermal contact. This may occur in different ways including direct and radiant transfer of heat. A heat exchanger’s performance is a function of material, geometry, and the overall surface heat transfer...

An active thermal management device, such as a thermoelectric module (TEM), has been employed to provide this additional heat pumping and temperature stabilization capability. A simple example of the type of heat pumping and temperature control offered by a TEM and its ability to cool a device is shown in Figure 5. Figure 5: TD is the temperature of the device to be cooled; TC is the temperature of the cold side of the TEM; TH is the temperature of the hot side of the TEM; and TA is the temperature of the ambient or surrounding environment where the heat is to be dumped. A Comparison of Active...

This can be illustrated by looking at the coefficient of performance (COP) of a TEM, which is defined as: COP = A TEM will pump a certain amount of heat, Q, and add an additional amount of heat, Q*COP to move this heat. This is a result of the inherent inefficiency in all engines. As a result, bulk TEMs are often sold as systems that include the TEM and a heat transfer mechanism such as a fan and heat sink or liquid heat exchanger. The value of the TEM in this case is that it can deliver sub-ambient temperatures and provide active temperature control but at the cost of increasing the system level...

Module Handling and Assembly 2 Thin film thermoelectric modules have extremely small form factors with footprints smaller than 10 mm . These devices are only 0.6mm high, making them the thinnest thermoelectric modules available on the market today. Due to their small form factor, care must be taken when handling and assembling modules into sub-assemblies for validation testing and production use. Figure 6 shows a typical thin film thermoelectric module. Please note the location of the primary and secondary headers, which are referenced in the assembly instructions that follow. Figure 6: Typical...

The assembly procedure that follows describes a method for fabricating a thermoelectric assembly as shown in the figure above where a thin film thermoelectric device is packaged between thermally conductive plates. These plates could represent separate heat-spreaders or could be an integral part of the heat-exchangers or temperature controlled target. The package has been optimized to meet the conflicting requirements of highly conductive thermal interfaces while allowing for mechanical isolation TM of the eTEC . Suggested Parts and Supplies List Solder – available from Indium Corporation in...