Large Image Sensor Chip Carrier with Ductile Adhesive
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Solution Overview
Problem
Large image sensors with chip areas greater than 100 mm² face issues due to thermal expansion coefficient mismatches between packages and substrates, leading to cracking, delamination, and thermo-mechanical stresses, as well as high thermal loads during assembly, which result in poor optical and mechanical properties.
Innovation Solution
The image sensor chip is glued to a chip carrier using a ductile adhesive, with wire bonding pads on the periphery, and the chip carrier is further attached to a circuit carrier using the same adhesive. A frame surrounds the chip, made of ceramic, glass, or silicon, with similar thermal expansion coefficients, enhancing mechanical rigidity and reducing chip curvature. The chip carrier can be recessed or positioned under the circuit carrier to minimize structural height and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If ceramic housings with large dimensions are used as carriers for large image sensors, then the chip area can be increased, but thermal expansion coefficient mismatch causes cracking, delamination, and high chip curvature
Solution Approach 1:
The patent introduces an intermediate carrier structure made of glass or silicon that serves as a buffer between the image sensor chip and the ceramic housing. This intermediary material has a thermal expansion coefficient matched to the chip, absorbing thermal stress and preventing direct transmission of expansion forces to the chip, thereby eliminating cracking and delamination while enabling large chip areas
Solution Approach 2:
The patent changes the material parameter (thermal expansion coefficient) of the carrier from ceramic to glass or silicon, which have coefficients matched to the image sensor chip. This parameter change ensures thermal compatibility, preventing the thermal expansion mismatch that causes structural failures and excessive chip curvature in large sensors
2Strength
If ceramic components with thickness >3 mm are used, then structural strength is improved, but the overall height becomes too large
Solution Approach 1:
The patent creates a composite structure combining a thin glass or silicon carrier with a separate ceramic housing. The glass/silicon carrier provides the necessary mechanical support for the chip with minimal thickness, while the ceramic housing provides external protection and mounting functionality. This composite approach achieves both strength and compact height by distributing structural requirements across different materials and components
3Ease of manufacture
If soldering process is used to assemble ceramic housings, then electrical connections are established, but high thermal load overloads adhesive connections between glass and housing
Solution Approach 1:
The patent segments the assembly process into two distinct stages: first, the image sensor chip is mounted on the glass/silicon carrier using adhesive at low temperature; second, the ceramic housing is attached to the carrier using soldering or other high-temperature methods. This segmentation isolates the adhesive bonding step from high thermal loads, preventing overload while maintaining electrical connectivity through the carrier's contact pads
4Device complexity
If direct assembly of large image sensors on PCB is performed, then device complexity is reduced, but thermal expansion mismatch causes warping and poor optical properties
Solution Approach 1:
The patent introduces the glass or silicon carrier as an intermediary substrate between the image sensor chip and the final PCB mounting location. This carrier acts as a stress-isolating platform that decouples the chip from PCB thermal expansion effects, preventing warping and maintaining precise optical alignment while adding only one intermediate assembly step
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 achieves a low-stress structure with minimal chip curvature, increased mechanical stability against bending forces, and reduced overall height, enabling cost-effective production and assembly of large image sensors with improved optical and mechanical performance.
Implementation Method 1
there is a significant mismatch in thermal expansion coefficients between the package and the substrate to which the package is soldered
Implementation Method 2
The image sensor chip is glued to the center of the chip carrier with a ductile adhesive
Data Source
Figure 1
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Figure 3
AI summary
The image sensor has an image sensor chip (2) which is arranged centrally on the chip carrier (7). A series of bond pads (4,9,13,14) are arranged in the outer periphery of the image sensor chip. A circuitry carrier (12) is secured between the image sensor chip and the chip carrier. The ductile adhesive agents (5) are provided between the image sensor chip and chip carrier. The circuitry carrier is provided with a cavity into which the chip carrier is let in.