Solid-State Image Sensor Package Cavity Pressure Relief
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Solution Overview
Problem
Existing solid-state imaging devices face issues with damage due to increased internal pressure in cavities during reflow, leading to cracks and unsticking of structural members, which can result in reduced performance and increased production costs, especially in compact WCSP configurations.
Innovation Solution
A solid-state imaging device with a concave portion on the semiconductor substrate and a filling resin portion made of thermoplastic resin, which is deformed to manage internal pressure and prevent damage, while maintaining the package structure's compactness and preventing dust entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a support made of resin is used to mount the cover member on the image sensor, then ease of manufacture is improved, but the support may crack or detach due to increased internal pressure in the cavity during reflow
Solution Approach 1:
A groove is formed in the support to create a reservoir that accommodates expansion of the filling resin during reflow processing. This beforehand cushioning structure prevents cracking and detachment of the support by providing a predetermined space for volume increase, thereby maintaining reliability while using resin materials that are easier to manufacture.
2Volume of moving object
If the package structure is downsized for compact devices like smartphones, then device size is reduced, but the cavity becomes more susceptible to pressure damage during reflow
Solution Approach 1:
The groove structure is integrated into the support of compact WCSP packages, providing a built-in expansion space that cushions pressure effects. This allows downsized devices to maintain reliability during reflow by accommodating resin expansion within the groove, preventing structural damage despite the smaller overall package size.
Solution Approach 2:
The groove is nested within the support structure itself, creating a space-efficient solution that accommodates resin expansion without increasing the overall device size. This nested design allows compact packaging while maintaining the pressure relief function needed for reliability.
3Reliability
If additional moisture-absorption members or complex air passages are added to prevent pressure damage, then reliability is improved, but device complexity and production costs increase
Solution Approach 1:
The filling resin itself serves the dual function of filling the cavity and providing pressure relief through its expansion into the groove during reflow. This self-service approach eliminates the need for separate moisture-absorption members or complex air passages, maintaining reliability while reducing device complexity and production costs.
Solution Approach 2:
The groove structure merges the support function with the pressure relief function into a single integrated component. By combining these functions in the support itself, the design avoids adding separate components, thereby reducing device complexity while maintaining reliability.
4Reliability
If the cavity is sealed to prevent dust entry, then reliability is improved, but internal pressure increases during reflow causing damage to structural members
Solution Approach 1:
The groove structure provides beforehand cushioning by creating an expansion space that accommodates filling resin during reflow. This allows the cavity to remain sealed for dust protection while the groove absorbs pressure buildup, preventing damage to structural members like the semiconductor substrate and cover member.
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 damage from increased internal pressure, maintains structural integrity, and reduces production costs by avoiding the need for additional moisture-absorption members or complex air passages, ensuring reliable performance and compact size.
Implementation Method 1
a filling resin portion made of a thermoplastic resin and provided to be filled into the concave portion, the filling resin portion being deformed with the semiconductor substrate
Implementation Method 2
a filling resin portion made of a thermoplastic resin
Data Source
AI summary
A package structure that includes a cavity between a solid-state imaging element and a cover member prevents damage caused due to an increase in the internal pressure in the cavity, for example, upon reflow. A solid-state imaging device includes a solid-state imaging element that includes a semiconductor substrate and of which a light-receiving side is a side of one of plate surfaces of the semiconductor substrate; a translucent cover member that is provided on the light-receiving side of the solid-state imaging element, and a support that is provided on the light-receiving side of the solid-state imaging element, and supports the cover member. The semiconductor substrate further includes a concave portion that is formed on another of the plate surfaces of the semiconductor substrate.