Patent Application
20050081905
The present invention relates to a thermopile IR detector package structure and, more particularly, to a technique making use of the silicon micro-electro-mechanical processing technique to fabricate devices and encapsulations. This kind of package structure can fabricate thermopile IR detection surface mount devices to match automatic production trend of the surface mount technology (SMT).
Using a thermocouple for temperature measurement is a well-known technique. When two different kinds of metals (conductors) make up a loop, a voltage will be generated if the temperatures of two joints are different. This thermoelectric characteristic is called the Seebeck effect. The temperature difference of two ends of a thermocouple can be known by measuring the magnitude of the Seebeck voltage.
Through a special structure design, a thermocouple can be used for thermal radiation measurement by the temperature difference of two joints caused by absorption of thermal radiation. Early thermocouple is usually made of metal filaments (e.g., Cu-Constantan). It is found later semiconductor materials have higher thermoelectric constants. Therefore, semiconductor thermocouples have been developed for weak thermal radiation measurement. However, the thermoelectric voltage provided by a single thermocouple is much limited. Several tens or hundreds of thermocouples are thus series-connected to form a so-called thermopile for enhancing the thermoelectric voltage signal. This thermoelectric voltage is proportional to the number of thermocouples, the thermoelectric constant of material, the temperature difference of cold and hot joints and so on.
In recent years, along with popularity of the silicon micro-electro-mechanical processing technique, high-performance thermopile structures with low thermal capacities and high thermal insulating characteristics have been disclosed. These structures makes use of semiconductor fabrication materials (e.g., poly-silicon and aluminum) as thermocouples and the semiconductor mass production technique for providing thermopiles of high quality and low cost. Thermopile IR detectors mainly apply to temperature measurement and monitoring such as ear thermometers, hair dryers, microwave ovens and the car industry and gas detection based on IR absorption characteristics.
Conventional thermopile IR detectors are mainly packaged with the standard TO-5 or TO-18 metal transistor package, as shown in
Accordingly, the present invention proposes a thermopile IR detector package structure to solve the problems in the prior art.
The primary object of the present invention is to provide a thermopile IR detector package structure, which makes use of an encapsulation formed by the silicon micro-electro-mechanical technique to seal a detector. In addition to having the sealing function, this encapsulation has also the function of detecting the spectrum and the field of view.
Another object of the present invention is to provide a thermopile IR detector package structure, which can match a substrate to form a surface mount device (SMD) for facilitating mass production and reducing the fabrication procedures, material, volume and weight.
Yet another object of the present invention is to provide a thermopile IR detector package structure, which can form a thermopile IR detector SMD to be in agreement with existent automatically produced electronic components. Manufacturers can thus adopt automatic production equipments to reduce the production procedures and time and lower the cost of system manufacturing, hence facilitating mass production and effectively solving the problems in the prior art.
To achieve the above objects, the present invention proposes a new thermopile IR detector package structure, which comprises a detector and an encapsulation. Thermoelectric components are formed on a substrate of the detector. The encapsulation is installed above the substrate of the detector to seal the thermoelectric components thereon. This encapsulation is formed by etching a cavity in a silicon substrate.
Moreover, the present invention further coating an anti-reflection multi-layer film on the inner and outer surfaces of the encapsulation. A metal shield layer is then coated on the outer surface of the encapsulation. The field of view (FOV) of the detector is controlled through the thickness of the encapsulation and the metal shield layer. Besides, the FOV of the detector can also be controlled through the size and etched depth of the encapsulation.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which:
The present invention provides a new thermopile IR detector package structure, which makes use of an encapsulation formed by the silicon micro-electro-mechanical technique to seal a detector, and a carrier substrate is matched to form an SMD for facilitating mass production and reducing the fabrication procedures, material, volume and weight. The conventional TO-5 or TO-18 package can thus be replaced.
As shown in
Next, a mold 28 is used to install the encapsulation 30 formed by etching a cavity in a silicon substrate on the surface of the insulating layer 24 on the substrate 14 of the detector 12 for sealing the thermoelectric components 20 thereon. Anti-reflecting multi-layer films 32 and 34 are coated on the inner and outer surfaces of the encapsulation 30, respectively.
The cavity is etched in the silicon substrate by using silicon anisotropic etching technique or silicon isotropic etching technique. Although the shapes of the formed encapsulations are different, their functions are the same. In addition to using the mold 28 for sealing the encapsulation 30 and the detector 12, solder or low-temperature glass can also be used.
In the present invention, a silicon substrate of an appropriate thickness is used to make the encapsulation 30. IR rays incident to the inner bevel edges of the encapsulation 30 won't be absorbed by the detector 12 due to total reflection. Therefore, the viewing angle of the detector 10 is mainly determined by the size of the thin board region of the encapsulation 30 and the distance from the thin board to the detector 12. The distance from the thin board to the detector 12 is mainly controlled by the etched depth. Moreover, in order to have a better effect of the viewing angle, a metal shield layer 36 can be coated on the surface of the anti-reflection multi-layer film 34 on the outer surface of the encapsulation 30, as shown in
Besides, along with the trend of compactness of electric products, components used in existent circuit boards are mainly packaged with SMD regardless of active or passive components to facilitate quick automatic production and mass production. The thermopile IR detectors disclosed in the present invention can be easily packaged into various types of SMD to conform to the present technique trend.
As shown in
A ball grid array (BGA) type SMD can also be formed in the present invention. As shown in
A thermo-sensitive resistor or diode can further be arranged on the above carrier substrate for temperature measurement of the main body.
To sum up, the present invention makes use of an encapsulation formed by the silicon micro-electro-mechanical processing technique to seal a detector. Next, anti-reflection multi-layer films are respectively coated on the inner and outer surfaces of the encapsulation to enhance the transmittance and limit the spectrum of the detector. The size of a thin board of the encapsulation, the etched depth of a cavity, and the size of a metal shield layer are properly designed to control the field of view of the detector. A carrier substrate is simultaneously matched to form a thermopile IR detector SMD. Through the thermopile IR detector package structure of the present invention, the fabrication procedures, material, volume and weight can be reduced. Moreover, manufacturers can adopt automatic production equipments to decrease the production procedures and time and lower the cost of system manufacturing, hence facilitating mass production and effectively solving the problems in the prior art.
Although the present invention has been described with reference to the preferred embodiments thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
