Rigid-Flex PCB Solder Joint Structure for Stronger Connections
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Solution Overview
Problem
Existing techniques for joining flexible printed wiring members to rigid printed wiring members with solder do not adequately address the issue of improving the strength of the connection between these components.
Innovation Solution
The electronic module design includes a configuration where the solder member has specific height variations and overlapping regions with the electrodes, forming a fillet-like structure that enhances the connection strength by increasing the volume of solder at the connection points, thereby distributing load effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional solder joining is used between rigid and flexible printed wiring members, then the connection is simple to manufacture, but the connection strength is insufficient
Solution Approach 1:
The solder member extends in the width direction (lateral dimension) beyond the electrode width, creating a fillet-like structure. This dimensional extension increases the solder volume and creates a tapered profile that improves mechanical interlocking and load distribution, thereby enhancing connection strength without complicating the manufacturing process
Solution Approach 2:
The solder member's width is designed to be larger than the electrode width, and its height varies across the width direction with a tapered profile. These parameter changes create a fillet-like structure that increases the effective bonding area and improves stress distribution, resolving the contradiction between connection strength and structural complexity
2Strength
If solder volume is increased to improve connection strength, then the mechanical strength improves, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The solder member is designed with specific dimensional parameters: width larger than the electrode width and a tapered height profile. These controlled parameter changes increase solder volume for better strength while maintaining manufacturability through well-defined geometric constraints that are easier to control than irregular fillet shapes
Solution Approach 2:
By extending the solder laterally beyond the electrode edges and creating a tapered profile in the height direction, the design increases solder volume in a controlled manner. This dimensional approach provides predictable stress distribution and improves manufacturing precision compared to traditional fillet formations
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 design significantly improves the mechanical and electrical connectivity between the rigid and flexible printed wiring members, enhancing the module's durability and load-bearing capacity.
Implementation Method 1
a solder member joined to each of the first electrode and the second electrode
Data Source
AI summary
An electronic module includes a rigid printed circuit member having a first electrode, a flexible printed wiring member having a second electrode, and a solder member having first, second, and third portions. A first direction is perpendicular to, and a second direction is parallel to, a joined surface between the first electrode and the solder member. In the first direction, a second region of the first electrode partially overlaps a leading edge of the second electrode. In the second direction, the second portion is located between the first portion and the third portion and is continuous to each of the first portion and the third portion. A height of the third portion from a reference surface including the joined surface is larger than a height of the second portion from the reference surface and is smaller than a height of the first portion from the reference surface.