Photosensitive Chip-to-Board Assembly for Low-Loss 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 while maintaining imaging quality, with issues in electrical conduction performance, high process temperatures, and excessive pressing forces in the connection between rigid-flexible circuit boards.
Innovation Solution
The photosensitive chip is directly connected to the circuit board via a conducting medium on the board, using a non-conducting adhesive for stability, and the connection is made at a low temperature (80-150°C) to reduce deformation and process difficulty, with an integral connecting structure that allows for simultaneous electrical and non-electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the photosensitive chip is electrically connected to the circuit board by wires, then the electrical connection can be established, but the conduction distance is long and signal loss is high
Solution Approach 1:
The patent extracts and eliminates the wire configuration from the electrical connection system. By removing the intermediate wire component and establishing direct contact between the photosensitive chip and circuit board through a conducting medium, the solution resolves the contradiction by shortening conduction distance while maintaining connection stability.
Solution Approach 2:
The patent introduces a conducting medium as an intermediary substance applied on the circuit board surface. This mediator enables direct electrical contact between the photosensitive chip and circuit board, achieving short conduction distance and low signal loss while providing stable electrical connection without requiring wire connections.
2Reliability
If the ACF (anisotropic conductive film) is used to connect the hard board and flexible board, then the electrical connection can be established, but the process temperature is high and pressing force is excessive
Solution Approach 1:
The patent replaces the expensive and complex ACF material with a simple conducting medium that can be applied as a thin layer. This conducting medium achieves the same electrical connection function at lower process temperatures and without requiring excessive pressing force, effectively substituting a simpler, more economical solution for the complex ACF system.
Solution Approach 2:
The patent changes the physical and chemical parameters of the connection medium by using a conducting medium with different properties compared to ACF. This conducting medium enables electrical connection at lower temperatures and with reduced pressing force, resolving the contradiction between connection reliability and process conditions.
3Volume of moving object
If the camera module size is reduced, then the mobile phone space is saved, but the imaging quality may be compromised
Solution Approach 1:
The patent repositions the photosensitive chip to be disposed on the back side of the circuit board, utilizing the z-dimension (vertical space) rather than expanding the planar area. This dimensional change allows the camera module to maintain compact size while preserving imaging quality by optimizing the optical path length and chip positioning.
Solution Approach 2:
The patent employs a flexible circuit board that can be bent to connect the front and back sides of the camera module. This dynamic configuration allows the electrical connection to adapt to the compact three-dimensional layout, enabling small module size while maintaining proper electrical connectivity and imaging performance.
4Length of stationary object
If the photosensitive chip is disposed on the back side of the circuit board, then the optical back focal length is increased, but the connection complexity increases
Solution Approach 1:
The conducting medium serves multiple functions simultaneously: it provides electrical conduction, acts as an adhesive to bond the photosensitive chip to the circuit board, and fills the gap between the chip and board surface. This multi-functionality simplifies the connection structure while enabling the photosensitive chip to be disposed on the back side for increased optical back focal length.
Solution Approach 2:
The patent merges the electrical connection function and mechanical bonding function into a single conducting medium layer. By combining these functions, the solution achieves simplified connection structure that enables back-side chip mounting and increased optical back focal length without adding complex connection mechanisms.
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 enhances conductivity, reduces signal loss, ensures stable electrical connections, and allows for a compact design with reduced overall height and increased optical back focal length, while minimizing process complexity and deformation.
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
Implementation Method 3
the process of electrically connecting the photosensitive chip to the circuit board is performed at a relatively low temperature, accordingly on one hand the difficulty of the process is reduced, and on the other hand the amount of expansion/contraction of a non-conducting adhesive disposed between the photosensitive chip and the circuit board is reduced
Data Source
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.