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Infrared sensor with back side infrared filter

IP.com Disclosure Number: IPCOM000187581D
Publication Date: 2009-Sep-11
Document File: 6 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

An infrared sensor comprises a temperature sensor (4) at a top side of a substrate (1) and an infrared filter element (19) located at a bottom side of the substrate (1). A lead frame is placed above the substrate (1) and a housing is cast having a window (42) extending to the filter element (19). A recess (27) in the lead frame (25) provides a large distance between the temperature sensor (4) and the metal of the lead frame (25), thereby reducing thermal conductance. This type of device is easy to manufacture.

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Infrared sensor with back side infrared filter

Abstract

  An infrared sensor comprises a temperature sensor (4) at a top side of a substrate (1) and an infrared filter element (19) located at a bottom side of the substrate (1). A lead frame is placed above the substrate (1) and a housing is cast having a window (42) extending to the filter element (19). A recess (27) in the lead frame (25) provides a large distance between the temperature sensor (4) and the metal of the lead frame (25), thereby reducing thermal conductance. This type of device is easy to manufacture.

  The invention relates to an infrared sensor comprising a temperature sensor arranged on a membrane and an infrared filter, as well as to a manufacturing method of such a sensor.

  Infrared sensors for measuring radiation in the spectral range between 800 nm and 20 m have a variety of applications, such as for contact-less temperature measurement as well as infrared spectroscopy.

  A sensor of this type is described in DE 10 2004 002 163. It comprises a temperature sensor arranged on a membrane at the top side of a substrate. A bandpass filter plate is mounted above the temperature sensor. Infrared light passing through the bandpass filter reaches the temperature sensor and heats it up, which allows to measure the amount of light. The substrate is located on top of a lead frame. A housing is cast around this assembly. The housing has a top side window extending to the filter.

  The problem to be solved by the present invention is to provide a sensor of this type that is easy to manufacture, as well as a corresponding manufacturing method.

This problem is solved by the sensor and the method according to the independent claims.

Accordingly, the filter member is not arranged above the temperature sensor, but rather below the temperature sensor.

  This simplifies the manufacturing process because the filter element can be mounted from the bottom side of the substrate. The bottom side of the substrate can be accessed easily and does not contain any sensitive components.

  In an advantageous embodiment, the filter element is arranged at the bottom side of the substrate. In this case the substrate acts as a spacer that keeps the filter plate at a distance of, typically, several 100 m from the temperature sensor, thereby improving the thermal insulation of the temperature sensor.

  Advantageously, the sensor further comprises a lead frame, and the lead frame is located at the top of the substrate (i.e. at the side of the temperature sensor), which places the contact pads of the substrate right to the leads of the lead frame.

  Other advantageous embodiments are described in the dependent claims as well as in the following description. The description refers to the enclosed figures, wherein:

Fig. 1 is a top view of a first embodiment of a core sensor,

Fig. 2 is a secti...