Radiused Bend Forming Apparatus for Flexible Flat Cable Impedance Control
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Solution Overview
Problem
Conventional flexible flat cables (FFCs) face challenges in handling and installation due to their stiffness, which causes a spring effect and increased impedance when bent, leading to potential lifting of printed circuit boards and undesirable creases that alter electrical impedance.
Innovation Solution
An apparatus with a radiused portion and clamp mechanism is used to shape the FFC, determining a controlled bend radius and preventing creases, ensuring the FFC is securely attached to circuit boards without applying spring forces or straining connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the FFC is formed with a bend to interconnect adjacent PCBs, then the connection between PCBs is achieved, but the spring effect causes handling difficulty and may lift PCBs away from locator posts
Solution Approach 1:
The apparatus uses a radiused portion with a specific curvature radius to form a controlled bend in the FFC. This curved geometry allows the cable to flex smoothly between PCBs without creating excessive spring force, while still achieving the necessary connection. The radiused portion ensures the bend follows a predictable arc that accommodates the stiffness of the FFC.
Solution Approach 2:
The apparatus controls the bend radius parameter of the FFC by constraining it within the radiused portion. By maintaining the bend radius within a specific range (greater than or equal to the radius of the radiused portion), the spring force is reduced to acceptable levels while still achieving functional connection between PCBs.
2Force
If a crease is formed in the FFC to overcome spring load, then the spring load effect is reduced, but the impedance of the FFC increases to greater than 100 Ohms
Solution Approach 1:
Instead of creating a sharp crease that disrupts impedance, the apparatus forms a smooth curved bend using the radiused portion. This gradual curvature maintains the continuous geometry of the FFC, preventing impedance discontinuities while still reducing spring load through controlled flexibility.
Solution Approach 2:
The apparatus controls the bend radius parameter to be sufficiently large (at least equal to the radiused portion radius), which prevents the formation of sharp creases. This parameter control ensures that the FFC maintains its impedance characteristics (keeping it at or near 100 Ohms) while still achieving the necessary flexibility to reduce spring load.
3Volume of moving object
If the FFC is bent sharply to fit tight spaces, then space utilization is improved, but creases form that alter electrical impedance
Solution Approach 1:
The radiused portion of the apparatus enforces a minimum bend radius, ensuring that the FFC follows a smooth curved path rather than sharp angles. This curved geometry allows the cable to navigate tight spaces while maintaining continuous electrical pathways, preventing impedance alterations.
Solution Approach 2:
By controlling the bend radius parameter to be at least equal to the radiused portion radius, the apparatus ensures that even in tight spaces, the FFC maintains a geometry that preserves its impedance characteristics. The constrained curvature prevents crease formation while achieving space-efficient routing.
Data Source
AI summary
An apparatus (10) is configured to shape a flat flexible cable (FFC (12)). The apparatus (10) is configured such that a first end (14) and a second end (16) of the FFC (12) can be positioned, respectively, at a first location (18) and a second location (20) of a circuit board assembly (CBA (22)). The apparatus (10) includes a radiused portion (30) configured to determine a bend radius (28) of the FFC (12) when the FFC (12) is installed into the apparatus (10). The apparatus (10) also includes a clamp portion (32) configured to urge the FFC (12) around the radiused portion (30) when the FFC (12) is installed into the apparatus (10).