PCB Assembly Solder Joint Stress Distribution via Recessed Cavities
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Solution Overview
Problem
In printed circuit board assemblies, particularly in 5G mobile communication devices, the increasing power consumption and space constraints lead to inadequate PCB area, resulting in high stress on single solder joints, making them failure-prone due to inadequate space for solder flux volatilization and increased risk of electromigration.
Innovation Solution
The solution involves a printed circuit board assembly with multiple solder joints and recessed cavities arranged in a predetermined direction to disperse stress, provide electromagnetic shielding, and increase gaps between solder joints in X, Y, and Z directions, ensuring effective stress distribution and solder flux volatilization, thereby enhancing electromigration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If multiple PCBs are stacked in the Z-axis direction to expand usable area, then PCB area is improved, but stress on single solder joint increases and reliability deteriorates
Solution Approach 1:
The patent divides the single solder joint into multiple solder joints (first solder joint and second solder joint) that are sequentially arranged in the Z-axis direction. Each solder joint independently connects corresponding solder pads on adjacent PCBs, distributing the mechanical stress and reducing the load on any single joint, thereby improving reliability while maintaining the stacked PCB configuration.
Solution Approach 2:
The patent transitions from a single-point connection to a distributed connection along the Z-axis dimension. By arranging multiple solder joints sequentially in the Z-axis direction rather than relying on a single joint, the connection becomes three-dimensional, allowing stress to be distributed across multiple locations and improving overall joint reliability.
2Volume of moving object
If solder joints are closely arranged to save space, then device compactness is improved, but space for solder flux volatilization decreases and electromigration risk increases
Solution Approach 1:
The patent segments the solder joint arrangement into distinct first and second solder joints with specific spacing requirements. The first solder joint connects solder pads on first PCBs, while the second solder joint connects solder pads on second PCBs, ensuring adequate separation between joints to allow solder flux volatilization and reduce electromigration risk while maintaining compact overall assembly.
Solution Approach 2:
The patent applies different spatial requirements to different regions: solder joints are arranged closely in the Z-axis direction to maintain compactness, but sufficient spacing is maintained in the X-Y plane to allow flux volatilization. This local differentiation of spatial constraints optimizes both compactness and reliability.
Data Source
AI summary
A printed circuit board assembly and a terminal are provided. The printed circuit board assembly includes: a first printed circuit board and a second printed circuit board, where the second printed circuit board is electrically connected to the first printed circuit board through at least four solder joints; the at least four solder joints include a first solder joint, a second solder joint, a third solder joint, and a fourth solder joint, the first solder joint communicates with the second solder joint, the third solder joint communicates with the fourth solder joint, and at least one solder joint and/or at least one printed circuit board cavity is provided between the second solder joint and the third solder joint; and the printed circuit board cavity is a recess structure that is recessed inwards from a surface of the printed circuit board.