Flexible Circuit Board Securing Portion Strength
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Solution Overview
Problem
Flexible circuit boards in optical communication elements face structural strength issues due to increased thickness and hardness at securing portions, leading to potential breakage during bending and usage, resulting in low functionality and product waste.
Innovation Solution
A flexible circuit board design featuring a substrate body with a transmission metal layer, a strengthening layer, and a surface metal layer, where the surface metal layer constitutes a securing portion for external connections, reducing the need for direct soldering to the transmission metal layer and enhancing structural strength by distributing stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the ground layer and tin solder layer are joined through electroplating to increase thickness and hardness at the securing portion, then the structural strength at the securing portion is improved, but the flexible circuit board becomes prone to breakage at the transition line during bending due to excessive hardness increase
Solution Approach 1:
The patent applies different metal layers with different properties to different locations: a first metal layer (softer, more ductile) at the securing portion for strength and solderability, and a second metal layer (harder, more wear-resistant) at the connecting portion for flexibility and bend resistance. This local differentiation resolves the contradiction by providing hardness where needed for strength while maintaining ductility where needed for bend resistance.
Solution Approach 2:
The patent uses a composite structure with two different metal layers: the first metal layer (e.g., copper or copper alloy) provides electrical conductivity and solderability, while the second metal layer (e.g., nickel or palladium alloy) provides enhanced mechanical strength and wear resistance. This composite approach allows the securing portion to have both the strength from the second metal layer and the electrical properties from the first metal layer, preventing breakage during bending.
2Ease of manufacture
If the ground layer is exposed by removing cover film to enable soldering connection, then the ease of manufacture is improved, but the structural integrity deteriorates due to increased thickness and hardness at the securing portion
Solution Approach 1:
The patent applies the second metal layer selectively only at the securing portion where soldering is needed, while leaving the connecting portion with only the first metal layer and cover film. This local application maintains structural integrity in the connecting portion while providing solderability at the securing portion, resolving the contradiction between ease of manufacture and structural integrity.
Solution Approach 2:
The patent segments the metal layer structure into two distinct zones: the securing portion with both metal layers for soldering, and the connecting portion with only the first metal layer and cover film for flexibility. This segmentation allows different functional requirements to be met in different areas without compromising overall structural integrity.
3Reliability
If electroplating is performed to join ground layer and tin solder layer, then the electrical conductivity is improved, but the hardness increase causes stress concentration and potential breakage
Solution Approach 1:
The patent changes the material parameters by selecting a second metal layer with appropriate mechanical properties (high strength, controlled hardness) that can be electroplated onto the first metal layer. This parameter optimization ensures that the electroplating process improves electrical conductivity while the second metal layer's controlled hardness prevents excessive stress concentration and breakage during bending.
Data Source
AI summary
A flexible circuit board, and an optical transceiver assembly and an optical module that have such flexible circuit board. The flexible circuit board includes a substrate body, a transmission metal layer formed on at least one surface of the substrate body, a strengthening layer formed on the transmission metal layer, and a surface metal layer formed on a portion of an outer surface of the strengthening layer. The surface metal layer constitutes a securing portion for securing and connecting to an external element. A portion of the flexible circuit board that is not covered by the surface metal layer constitutes a connecting portion that connects to the securing portion. The surface metal layer is electrically connected to the transmission metal layer.