Infrared Sensor Package Thermal Isolation
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Solution Overview
Problem
Existing integrated infrared sensor devices face challenges in achieving compact integration, efficient encapsulation, and low profile packaging while minimizing the need for complex MEMS manufacturing steps and maintaining effective thermal isolation.
Innovation Solution
The integration of an infrared sensor device with a cavity on the back surface and a filter substrate that transmits infrared radiation while attenuating visible light, combined with a cap for protection and solder bumps for flip-chip connection, allows for compact, low-profile packaging using standard backside etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the infrared sensor device is packaged in a compact enclosure with low height profile, then the device size and integration are improved, but the thermal isolation between the absorber and surrounding material becomes more difficult to achieve
Solution Approach 1:
The package is segmented into distinct functional regions: an absorber region containing the infrared-absorbing material and thermocouples, and a heat sink region with thermal vias. This segmentation allows thermal isolation between the absorber and surrounding material while maintaining compact overall dimensions. The thermal vias are concentrated in specific areas to provide heat sinking without requiring the absorber to be extensively thermally isolated throughout the entire package volume.
Solution Approach 2:
Thermal isolation and heat sinking are applied locally rather than uniformly throughout the package. The absorber is thermally isolated from immediate surroundings using low thermal conductivity materials (air gaps, epoxy resin), while heat sinking is provided locally through thermal vias connected to the heat sink region. This local application of thermal management strategies enables effective thermal control in a compact package.
2Reliability
If MEMS processing techniques are used to create thin support structures for thermal isolation, then the thermal isolation performance is improved, but the manufacturing complexity increases
Solution Approach 1:
The complex MEMS thin support structure is extracted and replaced with simpler conventional materials and techniques. Instead of using etched membranes or bridge structures requiring advanced MEMS processing, the patent uses air gaps and epoxy resin fillers to provide thermal isolation. This extraction of the complex thermal isolation mechanism reduces manufacturing complexity while maintaining thermal performance.
Solution Approach 2:
The patent employs inexpensive, easily manufactured materials such as air gaps and epoxy resin to provide thermal isolation, replacing expensive and complex MEMS-processed thin support structures. These simpler materials achieve the necessary thermal isolation function without requiring advanced manufacturing capabilities.
3Reliability
If the absorber is arranged on a thin support structure to minimize contact with wafer material, then the thermal isolation is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The thin support structure requiring precise thickness control is extracted and replaced with air gaps of indeterminate thickness that naturally provide thermal isolation. The air gaps are formed by the packaging process itself rather than requiring precise fabrication, eliminating the manufacturing precision requirement while maintaining thermal isolation performance.
Solution Approach 2:
The thermal isolation mechanism changes from relying on a thin solid support structure with controlled thickness to using air gaps where the isolation performance is less sensitive to dimensional variations. This parameter change from solid material thickness to air gap distance reduces manufacturing precision requirements.
4Ease of operation
If a separate ASIC is used for signal processing, then the processing capability is improved, but the device integration and compactness are worsened
Solution Approach 1:
The signal processing functions are merged with the infrared sensing element into a single integrated device. The thermocouples directly generate voltage signals that can be processed by on-chip circuitry or simple external readout electronics, eliminating the need for a separate ASIC and reducing overall package size while maintaining full signal processing capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient encapsulation and compact integration of infrared sensor elements with reduced height profile, simplified manufacturing, and effective thermal isolation, while maintaining sensitivity and protection against mechanical and stray radiation.
Implementation Method 1
The filter substrate is adapted in shape and composition to transmit infrared radiation
Implementation Method 2
attenuate radiation in at least part of the visible light spectrum
Implementation Method 3
The cavity is adapted for thermally insulating the first temperature-sensitive element from the second temperature-sensitive element
Implementation Method 4
A temperature difference between this absorber and the surrounding material, which forms or thermally connects to a heat sink, may be used to generate an appropriate signal indicative of the incident radiation
Data Source
AI summary
The present invention relates to an integrated infrared sensor device, comprising a sensor substrate and a filter substrate. The sensor substrate has a back surface and a front surface opposite the back surface, in which the back surface has a cavity defined therein and the front surface has at least one infrared sensing element formed therein or arranged thereon, covered with a cap for protecting the at least one sensing element, e.g. against mechanical damage and dust, and/or against stray radiation. The filter substrate is arranged on the back surface of the sensor substrate such that the filter substrate at least partially covers the cavity. The filter substrate is adapted in shape and composition to transmit infrared radiation and to attenuate radiation in at least part of the visible light spectrum.