Photosensitive Module Wafer-Level Packaging Thickness Reduction
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Solution Overview
Problem
Conventional camera module fabrication using chip on board (COB) technology faces challenges in reducing die thickness, requires physical pressing which can cause damage, and involves costly wire bonding processes that need to be performed in a clean environment, leading to high fabrication costs.
Innovation Solution
A photosensitive module is formed using a wafer-level packaging process where a sensing device with a conducting pad and redistribution layer is bonded to a circuit board, eliminating the need for physical pressing and wire bonding, and featuring a cover plate that is removed to expose the redistribution layer for electrical connection, allowing for thinner modules and reduced fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If COB technology is used to attach die to PCB, then electrical connection is achieved, but die thickness cannot be reduced and physical damage may occur
Solution Approach 1:
The patent replaces the mechanical pressing process of COB technology with a wafer-level packaging process where the sensing device is bonded to the circuit board in a planar configuration. The conducting pad and redistribution layer are exposed on the same plane as the substrate surface, eliminating the need for mechanical pressing and allowing thinner dies without risk of physical damage.
2Ease of manufacture
If wire bonding processes are used for electrical connection, then electrical conductivity is achieved, but fabrication cost increases and clean room environment is required
Solution Approach 1:
The patent extracts and eliminates the wire bonding process from the fabrication sequence. Instead of using wire bonding to create electrical connections, the design exposes the conducting pad and redistribution layer directly on the substrate surface, allowing for direct bonding to the circuit board through solder balls or other direct bonding methods, thereby simplifying the manufacturing process and reducing costs.
3Ease of operation
If cover plate is present on sensing device, then conducting pad is protected, but electrical connection to circuit board is blocked
Solution Approach 1:
The patent segments the substrate into multiple functional regions: a first opening that exposes the conducting pad for electrical connection to the circuit board, and a second opening that exposes the sensing region. The cover plate is selectively removed or configured to allow exposure of the conducting pad while maintaining protection for other areas, enabling both connection ease and protection where needed.
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 enables the reduction of module thickness without physical damage, reduces fabrication costs by eliminating the need for clean room processes, and facilitates easier electrical connection through exposed redistribution layers, improving the efficiency and cost-effectiveness of camera module production.
Implementation Method 1
a redistribution layer formed in the first opening and electrically connected to the conducting pad
Implementation Method 2
bonding the sensing device to a circuit board after the removal of the cover plate
Data Source
AI summary
A method for forming a photosensitive module is provided. The method includes providing a sensing device. The sensing device includes a conducting pad located on a substrate. A first opening penetrates the substrate and exposes the conducting pad. A redistribution layer is in the first opening to electrically connect to the conducting pad. A cover plate is located on the substrate and covers the conducting pad. The method also includes removing the cover plate of the sensing device. The method further includes bonding the sensing device to a circuit board after the removal of the cover plate. The redistribution layer in the first opening is exposed and faces the circuit board. In addition, the method includes mounting an optical component corresponding to the sensing device on the circuit board. A photosensitive module formed by the method is also provided.