Image Sensor Module Adhesive Thermal Expansion Warpage Control
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Solution Overview
Problem
The warpage phenomenon in image sensors with reduced thickness, caused by adhesive curing during attachment to a substrate, leads to deteriorated optical performance and reduced resolution in subminiature camera modules.
Innovation Solution
An image sensor module is designed with an adhesive layer having a coefficient of thermal expansion of 130 ppm/°C or more at the glass transition temperature, applied between the image sensor and a substrate with a higher coefficient of thermal expansion, using a copper clad laminate substrate and an epoxy-based adhesive, and cured at a temperature range of 120° C to 160° C with pressure applied for 1 to 2 seconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the image sensor thickness is reduced to achieve miniaturization, then the camera module size is reduced, but warpage phenomenon occurs during adhesive curing
Solution Approach 1:
The patent changes the thermal expansion parameter of the adhesive layer by selecting materials with specific coefficients. The image sensor has a thermal expansion coefficient of 3-7 ppm/°C, the substrate has 10-15 ppm/°C, and the adhesive layer is designed to have 120-180 ppm/°C, creating a gradient that compensates for warpage during curing
Solution Approach 2:
The patent uses a composite structure consisting of three distinct materials with different thermal expansion properties: the image sensor (3-7 ppm/°C), the substrate (10-15 ppm/°C), and the adhesive layer (120-180 ppm/°C). This composite design allows the adhesive layer to act as a buffer that compensates for differential thermal contraction, preventing warpage while enabling thin sensor design
2Strength
If adhesive curing is performed to attach the image sensor to the substrate, then the attachment strength is improved, but warpage deformation occurs due to thermal expansion differences
Solution Approach 1:
The patent optimizes the thermal expansion parameter of the adhesive layer to be 120-180 ppm/°C, which is significantly higher than both the image sensor (3-7 ppm/°C) and substrate (10-15 ppm/°C). This high thermal expansion coefficient allows the adhesive to expand more during heating and contract more during cooling, compensating for the contraction of the sensor and substrate, thereby maintaining attachment strength while preventing warpage
Solution Approach 2:
The patent exploits thermal expansion by designing the adhesive layer with a thermal expansion coefficient (120-180 ppm/°C) that is 10-20 times higher than the image sensor (3-7 ppm/°C). During the heating and cooling cycles of adhesive curing, this differential expansion and contraction creates a compensatory effect that prevents warpage while ensuring strong attachment
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 significantly reduces warpage deformation, maintaining lens focus and enhancing image resolution by minimizing the difference in thermal expansion rates between the image sensor and the substrate.
Implementation Method 1
an adhesive layer disposed between the image sensor and the substrate and including an adhesive having a third coefficient of thermal expansion of 130 ppm/° C. or more at a glass transition temperature Tg or more
Data Source
AI summary
There is provided an image sensor module, including: an image sensor having a small thickness of 175 μm or less and having a first coefficient of thermal expansion; a substrate having the image sensor mounted thereon and having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion; and an adhesive layer disposed between the image sensor and the substrate and including an adhesive having a third coefficient of thermal expansion of 130 ppm/° C. or more at a glass transition temperature Tg or more.