Reflowable Camera Module Solder Joint Reliability
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Solution Overview
Problem
Reflowable camera modules in Chip Scale Packages face reliability issues due to shear forces on solder joints, particularly in corner regions, where underfill encapsulants are costly and often omitted in high-volume manufacturing, leading to potential BGA ball shear failures.
Innovation Solution
Incorporating additional localized mechanical supports, such as dummy solder joints or leads, around the camera module's corners to provide mechanical protection without using underfill encapsulants, which can be formed during the reflow process and do not couple electrical signals or power, thereby enhancing the reliability of solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill encapsulant is used to improve solder joint reliability, then solder joint reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by placing mechanical support structures (dummy solder joints or reinforcement elements) specifically at corner regions where shear forces are most critical, rather than using uniform underfill encapsulation across the entire module. This localized approach provides necessary mechanical support where needed most while avoiding the high costs and complexity of complete underfill encapsulation.
Solution Approach 2:
The patent employs dummy solder joints made from inexpensive materials that provide mechanical support but do not carry electrical signals. These dummy structures serve as sacrificial mechanical reinforcement elements that can be formed using standard solder paste or balls during the reflow process, replacing the need for expensive underfill encapsulant while maintaining solder joint reliability.
2Reliability
If underfill encapsulant is used to protect solder joints, then solder joint reliability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential protective function from the complex underfill encapsulation process and implements it through simpler dummy solder joints or corner reinforcement structures. By separating the mechanical support function from the electrical connection function, the patent eliminates the need for complex underfill material application and curing processes while maintaining solder joint protection.
Solution Approach 2:
The patent replaces complex underfill encapsulation with simple dummy solder joints that can be formed using standard reflow processes. These dummy structures provide the necessary mechanical reinforcement without requiring additional manufacturing steps, materials, or quality control procedures associated with underfill encapsulation.
3Reliability
If dummy solder joints are added for mechanical support, then solder joint reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent makes the reflow process universal by having it perform both electrical connection (through functional solder joints) and mechanical reinforcement (through dummy solder joints) in a single operation. The dummy solder joints are formed using the same solder paste and reflow conditions as the functional joints, eliminating the need for separate placement processes and reducing overall manufacturing precision requirements.
Solution Approach 2:
The patent merges the formation of functional solder joints and dummy mechanical support joints into a single reflow process. By combining these functions, the patent reduces the number of manufacturing steps and aligns the precision requirements, allowing both types of joints to be formed simultaneously under identical process conditions rather than requiring separate high-precision placement operations.
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 additional mechanical supports effectively protect solder joints from shear forces, improving their reliability and preventing BGA ball shear failures, even without underfill encapsulants, thus enhancing the durability of reflowable camera modules in consumer devices like camera phones.
Implementation Method 1
A reflowable camera module utilizes solder joints to form electrical power and signal connections between an image sensor and a printed circuit substrate
Implementation Method 2
reflowing a Ball Grid Array (BGA) of solder balls to form solder joints with a printed circuit board
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3C
AI summary
A reflowable camera module has a set of solder joints formed on a bottom surface of the camera module that provide electrical signal and power connections between the camera module and a printed circuit substrate. The solder joints are susceptible to failure caused by shear forces, particularly in corner regions. Additional localized mechanical supports are provided to protect those solder joints carrying power and electrical signals for the camera module. The localized mechanical supports are formed outside of a region containing the solder joints carrying power and electrical signals. The localized mechanical supports may include dummy solder joints formed in corner regions and/or dummy leads used to support the camera module. Solder joint reliability is enhanced without requiring the use of an underfill encapsulant.