Backside Photosensitive Chip Assembly for Compact Camera Modules
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Solution Overview
Problem
Existing camera modules face challenges in achieving high pixel, large chip, small size, and large aperture simultaneously due to limitations in imaging quality, space constraints in mobile devices, energy consumption, and defects in electrical connection methods such as ACF, which result in uncontrollable conduction performance, high process temperature, and excessive pressing force.
Innovation Solution
A photosensitive assembly where the photosensitive chip is electrically connected to a circuit board by a conducting medium with a non-conducting adhesive, allowing direct contact and bonding at a lower temperature, reducing signal loss and process complexity, and eliminating the need for traditional wire connections, while also enabling a smaller form factor and improved optical back focal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ACF (anisotropic conductive film) is used to electrically connect the hard board and flexible board, then electrical connection is achieved, but the electrical conduction performance is uncontrollable, process temperature is high, and pressing force is excessive
Solution Approach 1:
The patent extracts and eliminates the ACF intermediate layer from the electrical connection structure. By directly bonding the flexible board to the hard board without ACF, the patent achieves controllable electrical conduction performance while reducing process temperature and pressing force requirements, thereby resolving the contradiction between connection reliability and manufacturing ease
Solution Approach 2:
The patent introduces a conductive adhesive as a new intermediary material to replace ACF. This conductive adhesive provides controlled electrical conduction properties and can be applied at lower temperatures with reduced pressing force, thus improving both the reliability of electrical connection and the ease of manufacturing
2Manufacturing precision
If high pixel, large chip, and large aperture are implemented, then imaging quality is improved, but camera module volume increases
Solution Approach 1:
The patent repositions the photosensitive chip from the front surface to the back surface of the circuit board. This dimensional change allows the optical components (lens, aperture) to be arranged more efficiently in the vertical direction, enabling high pixel and large aperture configurations without proportionally increasing the overall camera module volume
Solution Approach 2:
The patent nests the photosensitive chip within the circuit board structure by mounting it on the back surface. This nesting approach allows the chip to be integrated into the existing board volume rather than adding external bulk, thus achieving high imaging quality components while maintaining compact module dimensions
3Reliability
If photosensitive chip is connected to circuit board by wires, then electrical connection is achieved, but conduction distance is long and signal loss occurs
Solution Approach 1:
The patent removes the wire connections from the electrical connection system. By establishing direct electrical contact between the photosensitive chip pads and the circuit board traces through back-side mounting, the patent eliminates long conduction paths and associated signal losses, thereby improving signal transmission quality while minimizing conduction distance
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 solution enhances conductivity and signal transmission, stabilizes electrical connections, reduces energy consumption, and allows for a more compact camera module design with improved imaging quality and reduced deformability, while maintaining low process costs and difficulty.
Implementation Method 1
a photosensitive chip in the photosensitive assembly is electrically connected to a circuit board by directly contacting a conducting medium disposed on the circuit board
Implementation Method 2
the photosensitive chip is bonded to the circuit board via a non-conducting adhesive disposed on the conducting medium
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
The present application relates to a circuit board assembly, a photosensitive assembly, a camera module, and preparation methods for the circuit board assembly and the photosensitive assembly. The photosensitive assembly includes a circuit board and a photosensitive chip. The circuit board includes a circuit board main body, a through hole formed through the circuit board main body, a set of circuit board electrical connecting terminals disposed on the lower surface of the circuit board main body, a conducting medium disposed on the circuit board electrical connecting terminals, and a non-conducting adhesive covering the conducting medium. The photosensitive chip includes chip electrical connecting terminals disposed in a non-photosensitive area. The chip electrical connecting terminals of the photosensitive chip is in contact with the conducting medium to be electrically connected to the circuit board electrical connecting terminals, and the photosensitive chip is bonded to the lower surface of the circuit board via the non-conducting adhesive, so that the photosensitive chip is electrically connected to the circuit board. In this way, the photosensitive chip is stably electrically connected to the circuit board with relatively low costs and relatively low process difficulty.