Low CTE Substrate Sensor Package Prevents Warpage
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Solution Overview
Problem
Conventional sensor package structures experience warpage and reduced reliability due to thermal stress when large-sized sensor chips are packaged, which compromises their sensing sensitivity and logic processing performance.
Innovation Solution
A sensor package structure incorporating a substrate with a low coefficient of thermal expansion (CTE) less than 10 ppm/°C, a sensor chip, metal wires, a glass cover with an annular supporting body, and an adhesive layer, which surrounds an enclosed space to reinforce structural strength and prevent warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of the sensor chip is increased to improve pixel resolution and light sensitivity, then sensing performance is improved, but the package structure size increases and thermal stress causes warpage
Solution Approach 1:
The patent changes the material parameter of the substrate by selecting a material with a coefficient of thermal expansion (CTE) less than 10 ppm/°C, which is lower than conventional substrates. This parameter change allows the substrate to better match the thermal expansion characteristics of the large-sized sensor chip, reducing thermal stress and preventing warpage during temperature changes while maintaining the large chip size needed for high pixel resolution and light sensitivity.
Solution Approach 2:
The patent employs a composite package structure consisting of multiple materials with different thermal expansion properties: a low-CTE substrate material, a sensor chip, a glass cover, and an adhesive layer. This composite structure is designed to manage thermal stresses through the coordinated thermal expansion characteristics of each layer, allowing the package to accommodate large sensor chips without warpage while maintaining structural integrity and sensing performance.
2Measurement precision
If the size of the sensor chip is increased to improve light sensitivity, then sensing performance is improved, but thermal stress increases causing warpage
Solution Approach 1:
The patent changes the thermal expansion parameter of the substrate by selecting a material with CTE less than 10 ppm/°C. This parameter change reduces the differential thermal expansion between the substrate and the large sensor chip, thereby minimizing thermal stress generation during temperature cycling while maintaining the large chip size necessary for high light sensitivity.
Solution Approach 2:
The patent applies local quality by using a substrate material with specifically optimized thermal expansion properties (CTE < 10 ppm/°C) in the critical region where thermal stress occurs. This localized material property optimization addresses the thermal stress issue at the substrate-chip interface without affecting the overall sensing performance of the large sensor chip.
3Ease of manufacture
If conventional substrate materials are used, then ease of manufacture is maintained, but warpage occurs due to high CTE mismatch
Solution Approach 1:
The patent changes the CTE parameter of the substrate material to be less than 10 ppm/°C, which is a significant departure from conventional substrate materials. This parameter change maintains ease of manufacture through established low-CTE material fabrication processes while effectively preventing warpage by matching the thermal expansion characteristics of the sensor chip, thereby preserving package flatness.
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 solution effectively prevents warpage and enhances the reliability of the sensor package structure by reducing thermal stress and maintaining high sensing sensitivity and logic processing performance.
Implementation Method 1
The substrate is made of a material with a coefficient of thermal expansion (CTE) that is less than 10 ppm/° C.
Implementation Method 2
The adhesive layer connects the annular supporting body to the substrate.
Implementation Method 3
The board body has a light-permeable portion and an annular portion arranged around the light-permeable portion. The sensing region of the sensor chip faces the light-permeable portion of the board body.
Data Source
AI summary
A sensor package structure includes a substrate, a sensor chip disposed on the substrate, a plurality of metal wires electrically connecting the substrate and the sensor chip, a glass cover disposed on the sensor chip, and an adhesive layer connecting the glass cover to the substrate. The substrate is made of a material having a coefficient of thermal expansion (CTE) that is less than 10 ppm/° C. The glass cover includes a board body and an annular supporting body connected to the board body. The annular supporting body of the glass cover is fixed onto the substrate through the adhesive layer, so that the glass cover and the substrate jointly surround an enclosed accommodating space. The sensor chip and the metal wires are arranged in the accommodating space, and the sensing region of the sensor chip faces the light-permeable portion of the board body.