Infrared Gas Sensor Terminal Layout to Limit Substrate Warping
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Solution Overview
Problem
Warping of semiconductor substrates in gas sensors due to thermal expansion during device mounting causes characteristic variation, particularly in small sensors, which affects the performance of infrared light-receiving and emitting elements.
Innovation Solution
The gas sensor design includes a substrate with a light-emitting element and a light-receiving element positioned such that they are not on a line linking any two external connection terminals, with a redistribution layer and external connection terminals arranged in a specific direction to minimize substrate deformation, and a light guide to direct light between the elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external connection terminals are arranged on the substrate, then electrical connection is achieved, but substrate warping occurs due to thermal expansion stress
Solution Approach 1:
The patent applies asymmetry by arranging external connection terminals non-symmetrically on the substrate, specifically positioning them away from the optical path region. This asymmetric layout balances the thermal expansion stress distribution across the substrate, preventing warping while maintaining electrical connection functionality.
Solution Approach 2:
The patent resolves the contradiction by transitioning from a one-dimensional linear arrangement of terminals to a two-dimensional distributed arrangement. By placing terminals at multiple positions across the substrate surface rather than along a single line, the thermal stress is distributed more evenly, preventing warping while ensuring electrical connectivity.
2Adaptability or versatility
If light-emitting element and light-receiving element are positioned on the substrate, then optical detection function is achieved, but they become vulnerable to substrate deformation effects
Solution Approach 1:
The patent extracts the optical elements (light-emitting element and light-receiving element) from the general substrate area and positions them in a dedicated optical region. This separation isolates the sensitive optical components from the areas subject to thermal expansion stress, reducing the impact of substrate deformation on optical detection accuracy.
Solution Approach 2:
The patent applies local quality by creating a distinct optical region with different structural characteristics from the rest of the substrate. The optical elements are positioned in this specialized zone where the substrate structure is optimized to minimize deformation, ensuring stable optical detection performance while other parts of the substrate accommodate electrical connections.
3Device complexity
If terminals are arranged in a line, then electrical connection is simplified, but substrate warping is exacerbated due to concentrated stress
Solution Approach 1:
The patent segments the terminal arrangement from a single continuous line into multiple discrete positions distributed across the substrate. This segmentation breaks up the concentrated stress pattern that would occur with linear arrangement, allowing electrical connections to be made while distributing thermal expansion forces to prevent substrate warping.
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 configuration suppresses characteristic variation caused by substrate deformation, ensuring stable performance of the gas sensor by preventing hardening or pulling forces on the elements during thermal cycling.
Implementation Method 1
an infrared light-emitting element (infrared light-emitting diode (LED)) that emits infrared light in response to input electrical power
Implementation Method 2
A quantum infrared light-receiving element detects infrared light through photoelectric current generated when a semiconductor having a pn junction or pin junction absorbs infrared light
Implementation Method 3
An NDIR gas sensor can measure gas concentration using an infrared light-receiving element that receives infrared light of an absorption wavelength band in accordance with a detection target gas
Data Source
AI summary
Provided is a gas sensor that can suppress characteristic variation caused by deformation of a semiconductor substrate. The gas sensor (1) includes a substrate (redistribution layer 30), a light-emitting element (11) provided at a front surface (30a) or embedded in the substrate, a light-receiving element (12) that is provided at the front surface or embedded in the substrate and that receives light emitted from the light-emitting element, and a plurality of external connection terminals (40) at a rear surface (30b) that is an opposite surface to the front surface of the substrate. At least a portion of the plurality of external connection terminals is electrically connected to the light-emitting element and the light-receiving element. The plurality of external connection terminals is arranged such that, in plan view, the light-emitting element and the light-receiving element are not present on a line linking any two external connection terminals.