The Next Generation in Peltier Cooler Technology

Thermoelectrics are solid-state devices based on semiconductor materials that take advantage of the Peltier effect to cool. At room temperature, most thermoelectrics are based on n-doped and p-doped Bismuth-Telluride semiconductor materials. When current flows from the n-doped material to the p-doped material, heat is absorbed. When current flows from the p-doped material to the n-doped material, heat is dissipated. By constructing a device where the current flows from n-doped to p-doped on one side and from p-doped to n-doped on the other side, one side of the device will absorb heat (get cold) while the other side dissipates heat when DC current is applied. By reversing the direction of the current, the hot and cold sides can swap polarities (the hot side becomes the cold side and vice versa).

This is the typical structure for a single-stage thermoelectric. Traditional thermoelectrics are built by physically assembling discrete blocks of n-doped or p-doped thermoelectric elements onto electrical circuits. The circuits are typically on ceramic plates that have metal lines to route the electrical current. The thermoelectric elements are placed onto the ceramic plates using pick-and-place assembly equipment and attached to the metal lines on the ceramic plates using solder.

Based on this method of manufacturing, the ability to scale the size of the thermoelectrics to smaller scales has been limited. The use of extensive solder connections in the electrical current path within the thermoelectric cooler also leads to degradation in reliability.

Scaling to smaller size thermoelectrics is desirable for several reasons. The cooling density (watts per square centimeter that it can cool) of a thermoelectric is inversely proportional to the length (height in the above picture) of the thermoelectric element. By scaling to smaller geometries, higher cooling densities can be achieved. Higher cooling densities allow for cooling the same heat load within a smaller area or, conversely, allow higher cooling capacities using the same space. Higher cooling densities can also allow more rapid cooling and better temperature control in certain applications.

In order to scale down size and increase cooling densities, nanoCoolers has developed a proprietary wafer-scale manufacturing process to allow the thermoelectric to be built using thin-film materials. This allows the length of the thermoelectric element to be scaled from millimeters down to microns (an improvement of three orders of magnitude!). This allows significant improvement in cooling density and significant reduction in thermoelectric form factor.

nanoCoolers' manufacturing process is very similar to thin-film manufacturing processes used for silicon integrated circuits, but now using Bismuth Telluride materials. Since the circuit interconnections within the thin-film thermoelectric are based on standard CMOS metal layer processes, the solder is removed from the interconnects within the thermoelectric. This significantly improves device reliability.

nanoCoolers' thin-film thermoelectrics usher in a new era for thermoelectrics, reaching cooling densities, form factors and reliability previously unachievable with commercial devices. These can improve system performance (power efficiency, cooling times, and temperature control), reduce system form factors and improve system reliability. They also enable new applications for thermoelectrics previously impossible.

Advantages

• High cooling density
• High power efficiency
• Small form factor
• Lightweight
• High reliability
• Fast cooling times
• Excellent temperature control
• Silent performance
• Ability to cool and heat
• Environmentally friendly (no refrigerants)
• Orientation independent