Modular Optoelectronic Package for Thermal Stress Relief
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Solution Overview
Problem
Large optoelectronic photomultipliers face durability issues due to thermal cycling, which can cause flexing and cracking, especially in harsh environments like vehicles, where they must operate over a wide temperature range (-55°C to +150°C, and have a high aspect ratio, leading to potential electrical and mechanical malfunctions.
Innovation Solution
An optoelectronic package design featuring a modular structure with ceramic substrate modules and a glass-reinforced epoxy laminate circuit substrate, allowing for flexibility through seams between modules, reducing stress and preventing cracking, and incorporating a staggered arrangement of pixel array circuits with glass lids for light detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-piece rigid carrier is used to support pixel array circuits, then structural strength is improved, but the carrier is prone to cracking during thermal cycling due to CTE mismatch
Solution Approach 1:
The carrier is divided into multiple discrete substrate modules (e.g., four 10mm x 10mm modules) that are separately attached to the circuit substrate. These modular segments can independently flex and accommodate thermal expansion differences, preventing cracks that would occur in a rigid monolithic structure during thermal cycling from -55°C to +150°C.
2Area of stationary object
If the circuit substrate has a high aspect ratio (e.g., 4:1) to accommodate a large field-of-view, then detection coverage is improved, but the substrate becomes more susceptible to curving and mechanical stress
Solution Approach 1:
The long-dimensional carrier is segmented into multiple smaller substrate modules arranged in a sequence. This segmentation reduces the aspect ratio of individual modules, making them more stable and less prone to curving, while the overall array still provides the required large field-of-view coverage through the combined area of multiple modules.
3Strength
If ceramic substrate modules are used to provide mechanical strength, then structural integrity is improved, but thermal expansion mismatch with glass-reinforced epoxy laminate causes stress during thermal cycling
Solution Approach 1:
The carrier is segmented into multiple ceramic substrate modules that are separately attached to the glass-reinforced epoxy laminate circuit substrate. This segmentation allows each module to independently accommodate thermal expansion differences, reducing overall thermal stress while maintaining structural integrity through the distributed modular architecture.
Solution Approach 2:
The design accepts and accommodates the thermal expansion parameter difference between ceramic (first CTE) and glass-reinforced epoxy laminate (second CTE) by creating a modular structure that can flex. The segmented carrier changes its physical state from rigid to flexibly rigid, allowing it to adapt to thermal cycling conditions without developing excessive stress.
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
The modular design enhances the durability of optoelectronic circuits by allowing flexing without cracking, ensuring reliable operation over a wide temperature range and maintaining detection sensitivity for applications like vehicle LIDAR systems.
Implementation Method 1
the circuit substrate is curved along the long axis due to a difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion during a thermal cycle
Data Source
AI summary
A segmented optoelectronic semiconductor package may help to alleviate stresses resulting from bending that can cause a mechanical defect (e.g., crack) in a detector circuit. The bending can result from thermal growth/shrinkage of parts used in the optical electronic package and may be more pronounced for high aspect ratio detector circuits. The segmentation of the disclosed semiconductor package can create seams that allow the parts to flex without breaking. As a result, the disclosed semiconductor package may facilitate high aspect ratio optical detection over a wide temperature range.