OMRON develops MEMS non-contact thermal sensor utilizing wafer-level vacuum packaging

OMRON Corporation today announced that they have finished development work on the world’s first infrared sensor manufactured with wafer-level vacuum packaging technology to create a 16×16 element MEMS non-contact infrared thermal sensor capable of highly precise 90-degree area detection. OMRON says it will ship test samples beginning in October 2013.

In recent years, the demand for human presence sensors has been growing in tandem with the demand for energy-efficient "smart home" and "smart office" environments, in which lighting, heating, etc. is automatically controlled according to where people are positioned. Since conventional pyroelectric human presence sensors (motion sensors) are only able to detect people when they are in motion, they are not as suitable for detecting the number of people in a certain space or their relative positions as Omron’s new thermal sensor.

MEMS non-contact thermal sensors measure temperature by converting infrared energy radiated from target objects into heat with MEMS thermopiles and then measuring the thermoelectromotive force resulting from temperature differences that occur across the contact points of two different types of metal. However, up till now it has not been possible to create large temperature differences across the metal contact points because much of the heat generated by the thermopiles dissipates into the surrounding air, meaning that the resulting thermoelectromotive force is reduced thereby limiting sensitivity. Omron believes they solved this heat dissipation problem by vacuum sealing the thermopiles inside the chip – the first time this has been achieved. The reduction in heat dissipation leads to a greater temperature difference across the metal contacts thereby increasing sensitivity.

How non-contact thermal sensors work

MEMS thermal sensor wafer level packaging

Thermal sensors utilize the Seebeck effect in which thermoelectric force is generated due to the temperature difference at the contact points between two different kinds of metal. Thermopiles are created by serially connecting thermocouples consisting of N+ poly Si, P+ poly Si, and Al. By creating hot junctions on highly heat-resistant dielectric membranes, and cold junctions on highly heat-conductive silicon, it is possible to achieve high-energy conversion efficiency. Sealing thermopiles in a vacuum prevents the heat they create from dissipating into the air thereby increasing sensitivity. 

Omron will now also work on commercializing stand-alone human presence sensor modules by combining non-contact thermal sensors with algorithms that can accurately distinguish the number of people and their positions within a detected space.

Model versions of Omron’s new human presence sensors will be displayed at the "Nanomicro Biz" Exhibition at Tokyo Big Sight on July 3, 4, and 5.

The development of this new sensor was the result of research carried out in collaboration with Japan’s New Energy and Industrial Technology Development Organization.

 

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