Stacked FFC Busbar Welding for High-Current Flexible Terminals
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Solution Overview
Problem
Existing FFC bus bars suffer from weak fixing forces between conductor wires and high current terminals, leading to easy separation, which is exacerbated by increased current demands in electric vehicles.
Innovation Solution
An FFC bus bar design featuring a cable stack structure with terminal access portions of flat flexible cables welded to a high current terminal, using silver-plated copper welding sheets arranged in alternating layers, and secured with a compression band, eliminating the need for rivets or brackets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rivets or brackets are used to fix conductor wires to the high current terminal, then the connection structure is simple to manufacture, but the fixing force is weak and conductor wires easily separate
Solution Approach 1:
The patent replaces the mechanical fastening system (rivets or brackets) with a welding system to join the terminal access portion to the high current terminal. This substitution provides significantly stronger fixing force through metallurgical bonding while the welding process itself remains a standard manufacturing technique.
Solution Approach 2:
The patent uses silver-plated copper welding sheets that combine copper's high electrical conductivity with silver's excellent weldability and oxidation resistance. This composite material structure enables strong welding bonds while maintaining high current capacity.
2Power
If the cross-sectional area or thickness of flexible bus bars is increased to handle higher current, then the current capacity increases, but the bending process becomes impossible
Solution Approach 1:
The patent divides the conductor into multiple thin flat flexible cables (11) that are stacked together. Each individual cable remains thin and flexible, but when stacked in layers, they collectively provide high current capacity. This segmentation allows the system to achieve both high power and flexibility simultaneously.
Solution Approach 2:
The patent transitions from a single thick conductor to multiple thin conductors arranged in a stacked configuration. By utilizing the vertical stacking dimension, the system achieves high current capacity through increased effective cross-sectional area without compromising the flexibility of individual cable layers.
3Reliability
If a bracket structure is used to cover and fix stacked conductor wires, then the connection is secured, but the terminal portion becomes large in size
Solution Approach 1:
The patent merges the conductor wires and the terminal into a single integrated structure through welding. The terminal access portions are formed directly from the conductor wires themselves, eliminating the need for separate bracket structures and reducing the overall terminal portion size while maintaining secure connection.
Solution Approach 2:
The patent extracts and eliminates the bracket component from the traditional FFC bus bar structure. By using welding to directly join the conductor wires to the terminal, the bracket is removed entirely, reducing the terminal portion size while improving connection reliability through direct metallurgical bonding.
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
Provides a firm connection between conductor wires and the high current terminal, enhancing mechanical rigidity and reducing the size of the terminal portion, while maintaining flexibility and high current capacity.
Implementation Method 1
the terminal access portion is welded to the high current terminal
Data Source
Figure 1
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AI summary
An FFC bus bar includes: a cable stack structure formed by stacking a plurality of flat flexible cables; and a high current terminal connected to at least one end portion of the cable stack structure, wherein each flat flexible cable comprises a terminal access portion including strands of conductor wires at at least one end portion thereof, and the terminal access portion is welded to the high current terminal.