Flexible LED Foil Joining With Embedded Busbar for Low Voltage Drop
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Solution Overview
Problem
The existing joining technologies for flexible foils, such as mechanical fasteners, self-assembly, adhesive bonding, and heat welding, are inadequate for large area applications like Philips Large Luminous Surfaces, as they lead to voltage drops and efficiency losses due to electrical resistance in long lengths.
Innovation Solution
A method involving the embedding of a metal strip or wire between two flexible foils at the overlap, which acts as a busbar to minimize current loss and voltage drop, while also enhancing safety by being embedded and not directly touchable, using a high-frequency coil or other heating apparatus for melting the foils together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If flexible foils are joined using conventional methods (mechanical fasteners, adhesive bonding, or heat welding), then the foils can be connected for large area applications, but voltage drop and efficiency losses occur due to electrical resistance in long lengths
Solution Approach 1:
The patent replaces conventional mechanical joining methods (fasteners, adhesives, heat welding) with an electromagnetic induction system. A metal strip embedded in the foil serves as an eddy current busbar that is heated by electromagnetic induction from a coil, creating a molten pool that bonds the foils electrically and mechanically, eliminating voltage drop while enabling large area connections
Solution Approach 2:
The patent changes the electrical parameters by introducing a metal strip with high electrical conductivity as an eddy current busbar. This metal strip carries current with minimal resistance, and its electrical parameters are optimized through material selection and dimensional design to minimize voltage drop across long foil lengths
2Loss of energy
If a metal strip is used as busbar to minimize voltage drop, then electrical efficiency is improved, but safety risks increase due to direct exposure of conductive elements
Solution Approach 1:
The metal strip busbar is nested within the flexible foil structure, embedded between layers of the foil. This nesting configuration provides inherent insulation and protection, allowing the conductive element to perform its electrical function while being physically protected and isolated from direct contact, thus maintaining safety
Solution Approach 2:
The flexible foil itself acts as an intermediary protective layer between the metal strip busbar and the external environment. The foil material provides electrical insulation and physical protection, mediating between the high-current-carrying metal strip and users, eliminating direct exposure risks
3Ease of manufacture
If conventional joining methods are used, then manufacturing is simpler, but assembly must be discontinuous and structural integrity is compromised
Solution Approach 1:
The electromagnetic induction heating process enables continuous assembly operation. The coil continuously generates eddy currents in the metal strip as foils pass through, maintaining a continuous molten pool for ongoing bonding without interruption, thereby achieving continuous production and improved productivity
Solution Approach 2:
The metal strip undergoes phase transition from solid to liquid (molten pool) during the joining process, and then back to solid upon cooling. This controlled phase transition enables strong metallurgical bonding between foils while maintaining process simplicity and continuity
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 method effectively reduces voltage drop and efficiency losses over long lengths, while improving safety by embedding the metal strip or wire, allowing for continuous assembly and maintaining structural integrity.
Implementation Method 1
The apparatus may be a high frequency (HF) coil, wherein the high frequency coil is used for introducing an eddy current in the metal strip or wire to heat the metal strip or wire
Implementation Method 2
the heated metal strip or wire melts together the first flexible foil and the second flexible foil at the overlap
Implementation Method 3
the metal strip or wire electrically connects to the first and second sets of electrically conductive tracks
Data Source
AI summary
The present invention relates to a method for joining at least two flexible foils (10a-b). The method comprises the steps of (i) providing a first flexible foil (10a) having a first row (12) of light emitting diodes (14) and a first set of electrically conductive tracks (16) for supplying current to the first row (12) of light emitting diodes (14), (ii) providing a second flexible foil (10b) having a pot second row (12) of light emitting diodes (14) and a second set of electrically conductive tracks (16) for supplying current to the second row (12) of light emitting diodes (14), and (iii) joining the first flexible foil (10a) and the second flexible foil (10b) at an overlap (22) of the first flexible foil (10a) and the second flexible foil (10b), wherein a metal strip or wire (24; 24) gets embedded between the first flexible foil (10a) and the second flexible foil (10b) at the overlap, and wherein the metal strip or wire (24; 24) electrically connects to the first and second sets of electrically conductive tracks (16).