Laser-Pulsed FPC-to-Busbar Welding With a Nickel Contact Layer
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Solution Overview
Problem
Existing methods for connecting flexible printed circuits (FPC) to busbars, such as rivet pins and laser welding, often result in damage to the metal sheet and FPC, and do not provide a strong, reliable, and durable connection.
Innovation Solution
A method involving a metal sheet with a thickness between 0.15 mm and 0.25 mm, preferably made of nickel, is laser-welded to the busbar using laser pulses to create welding joints in a contact region containing nickel, ensuring a strong mechanical and electrical connection without damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rivet pins are used to connect the busbar and flexible printed circuit, then electrical conductive connection is realized, but damage occurs to the metal sheet and FPC
Solution Approach 1:
The patent replaces the mechanical rivet pin connection system with a laser welding system. The laser welding process uses optical energy to melt and fuse the metal sheet to the busbar, eliminating the need for mechanical fasteners that cause damage through punching, pressing, or clamping forces. This substitution of mechanical connection with optical-thermal connection resolves the contradiction by achieving reliable electrical connection without mechanical damage to the FPC and metal sheet.
Solution Approach 2:
The patent utilizes the phase transition of metal from solid to liquid and back to solid during laser welding. The laser light heats the contact region until the metal melts, then cools and solidifies to form a strong weld joint. This phase transition mechanism allows for a connection process that is fundamentally different from mechanical fastening, avoiding damage while ensuring reliable electrical and mechanical connection between the busbar and FPC.
2Strength
If laser welding with continuous irradiation is used, then welding line is formed, but damage occurs to the metal sheet and FPC
Solution Approach 1:
The patent employs periodic pulsed laser irradiation instead of continuous irradiation. The laser delivers energy in controlled pulses with specific duration and intervals, allowing heat to dissipate between pulses and preventing excessive heat accumulation that would damage the FPC and metal sheet. This periodic action maintains strong weld joints while avoiding thermal damage to sensitive components.
Solution Approach 2:
The patent optimizes multiple laser welding parameters including pulse duration, pulse frequency, laser power, and spot size to achieve the desired balance between weld strength and damage prevention. By carefully controlling these parameters, the process delivers sufficient energy for strong mechanical connection while limiting peak temperatures and heat affected zone to prevent damage to the metal sheet and FPC.
3Adaptability or versatility
If metal sheet thickness is reduced for flexibility, then connection to FPC is improved, but welding reliability decreases due to gaps
Solution Approach 1:
The patent introduces a nickel-containing contact region as an intermediary layer between the metal sheet and the busbar. This nickel layer fills gaps and irregularities in the contact interface, ensuring consistent and reliable laser welding even with thin, flexible metal sheets. The nickel intermediary improves wetting and adhesion, allowing for dependable electrical and mechanical connection while maintaining the flexibility and thinness required for FPC compatibility.
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
The method achieves a peel force of over 110 N and resistance of 0.5 to 5 mOhm, providing a reliable, durable, and time-efficient connection between the busbar and FPC, reducing the risk of damage and improving adherence.
Implementation Method 1
welding the metal sheet to the busbar by using laser light for forming at least one welding joint within the contact region
Implementation Method 2
welding the metal sheet to the busbar by using laser light for forming at least one welding joint within the contact region
Data Source
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AI summary
A method for connecting a flexible printed circuit to a busbar (1), comprising - providing a metal sheet (2) having a thickness between 0.1 mm and 0.5 mm, preferably between 0.13 and 0.3 and more preferably between 0.15 and 0.25 mm, wherein the metal sheet (2) is connected to the flexible printed circuit (FPC), and providing the busbar (1), - arranging the metal sheet (2) at least partially on the busbar (1) for forming a contact region (CR), - welding the metal sheet (2) to the busbar (1) by using laser light (5) for forming at least one welding joint (7) within the contact region (CR), wherein laser pulses are used for forming the at least one welding joint (7) and wherein the contact region (CR) includes nickel.