Reliability considerations for Peltier Modules - Karpagam Institute of Technology
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Reliability considerations for Peltier Modules

Peltier modules are solid-state devices that transfer heat when electrical power is applied. It is also known as thermoelectric coolers (TEC) or thermoelectric modules (TEM). The reliability of Peltier modules is important in applications, so the basic knowledge of their construction and proper implementation is vital. Read this interesting blog on the Peltier modules by the Best Electrical and Electronics Engineering Colleges in Coimbatore

Peltier Module Construction

Peltier modules are solid-state devices and also it has no moving parts and it can operate in a wide range of temperatures.

Peltier modules are made up of positive and negative doped semiconductor pellets sandwiched between two electrically insulating but thermally conducting ceramic slabs. This module arrangement connects all of the semiconductor pellets electrically and mechanically. The series power lines provide the essential thermal effects, while the parallel mechanical structure allows heat to be gathered by one of the metal plates (cool side) and discharged by some other metal tray (hot side).

Peltier Module Failure Mechanisms

The structure Mechanical fracture of the semiconductor pellets or the related solder connections is the most prevalent failure mechanism of Peltier modules. These fractures do not initially spread entirely through the pellet or solder junction and can be identified by an increase in the device’s series resistance. The increase in resistance of the Peltier module reduces its overall “efficiency,” but a full failure can occur if a fracture propagates entirely across a semiconductor pellet or solder connection.

Mechanical Tension or Shear

In most Peltier module applications, an object to be cooled is placed on the module’s cold plate and a heat sink is placed on the module’s hot side. Mechanical problems are probable if the heat sink and the cooled object are bonded to the ceramic plates with no extra mechanical framework to support the cooled object and heat sink. When just the Peltier device is used to support the item or heat sink, substantial shear or tension stresses may be generated across the module. Peltier modules cannot handle high tension or shear pressures between the heat sink and the cold plate and will shatter if such forces are applied. In most applications, the Peltier module is sandwiched between the heat sink and the item to be cooled. Because Peltier modules can tolerate substantial compressive pressures from the clamps, this mechanical setup is employed, while the clamps absorb any shear or tension stress created between the item and heat sink.

Mechanical Compression

 Although Peltier modules can withstand high compressive loads, heat sinks and cooling items must be mounted in such a way that the clamping force is distributed evenly over the Peltier module. Uneven clamping forces generate torques and compressive forces between the ceramic plates, which might result in mechanical failure. The mechanical limitations that provide the compressive clamping force across a Peltier module must be applied with care and consistency. This reduces the torque strains imparted to the module and hence the chance of damage. Research more on the field of Electrical and electronics engineering by reading more blogs from the Best Private Engineering College in Coimbatore.

Thermal Cycling

The thermal expansion coefficients of the ceramic plates and semiconductor pellets used in Peltier modules are well-known (CTE). When the module is heated or cooled, mechanical forces caused by misalignment of the ceramic and semiconductor CTEs can produce fractures in the semiconductor pellets and solder connections. Thermal gradients throughout the device and high rates of change in temperature produce mechanical strains owing to CTEs, in addition to the change in absolute temperature of Peltier modules. Extreme temperatures, huge temperature gradients, and rapid temperature slew rates all result in elevated mechanical strains, which can lead to device failure.

Contaminants

Peltier modules’ semiconductor pellets, solder connections, and metalized conduction routes can be contaminated from outside sources, leading to failures. A popular method for reducing contamination exposure is to put a bead of sealant around the circumference of the module, between the two ceramic plates. Because of its mechanical compliance, silicone rubber is a popular sealant; nevertheless, in harsh working situations, silicone rubber may not be effective as a vapour barrier. Epoxy can be used as a perimeter sealer in areas with high vapour concentrations. Epoxy, on the other hand, is not as mechanically compliant as silicone rubber.

Peltier Module Reliability Improvements

Mechanical pressures can produce cracks in a Peltier module’s solder connections and semiconductor pellets, as previously discussed. CUI Devices’ arcTEC structure, which is included in its Peltier module family, increases module performance, reliability, and cycle life by combating the impacts of thermal fatigue. It begins by using electrically conductive glue to replace the solder connections on the module’s cold side. Because this resin is more mechanically compliant than solder, it can aid to reduce stress and fracture in typical Peltier module architectures. The arcTEC structure’s remaining solder connections are created with high-temperature antimony soldering (SbSn, 235°C), instead of the more conventional and reduced temperature bismuth solder (BiSn, 138°C).

Antimony solder is more resistant to mechanical stress than bismuth solder, which aids Peltier module dependability. Peltier modules from CUI Devices also come with a silicone rubber vapour barrier, which improves mechanical compliance. On request, other vapour barriers, such as epoxy, are available.

The tests below show how the arcTEC structure outperforms traditional Peltier modules in terms of dependability. The graphic demonstrates the quick rise in resistance of traditional module construction contrasted to the more constant performance of the arcTEC structure across a higher number of heat cycles, with failures rising as resistance increases. Update yourself more in this emerging field of Electrical and electronics engineering by reading the latest blogs from the Top college in Coimbatore.