Lead Frame Gap Reduction via Connecting Bar Deformation
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Solution Overview
Problem
The challenge in manufacturing lead frames for very small LED die packages is the difficulty in achieving narrow clearance between anode and cathode contact regions, as conventional stamping tools are limited by the need for heat dissipation and precision, leading to high costs and inefficiencies in producing lead frames with gaps of 150 µm or less.
Innovation Solution
A method involving a stamping tool that initially stamps lead frames with wider gaps, followed by deformation of connecting bars to reduce the gap width to 250 µm or less, allowing for precise and economical production of lead frames suitable for small LED die packages, using techniques like bending connecting bars out of the plane to shorten their length and using gauges to control the final gap width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional stamping tools are used to manufacture lead frames, then heat dissipation capability is maintained through sufficient sheet metal thickness, but the gap width between contact regions cannot be reduced below the sheet thickness limit
Solution Approach 1:
The lead frame is segmented into multiple components: a base structure with contact regions and separate connecting bars that can be independently formed and then assembled. This allows the gap width to be determined by the connecting bar dimensions rather than being constrained by sheet metal stamping limitations, enabling gaps smaller than the base thickness while maintaining manufacturability through standard stamping processes for each component.
Solution Approach 2:
The connecting bars extend in a direction perpendicular to the plane of the base contact regions, creating a three-dimensional structure. This vertical dimension allows the gap width (horizontal dimension) to be independently controlled by the connecting bar dimensions, decoupling it from the base thickness constraint and enabling narrow gaps while maintaining adequate heat dissipation through the vertical thickness of the base.
2Manufacturing precision
If stamping tools are redesigned to achieve narrow clearance, then gap width precision is improved, but manufacturing cost increases significantly
Solution Approach 1:
The connecting bars are pre-formed with precise dimensions using conventional stamping tools before assembly. This preliminary formation of the connecting bars with controlled gap widths allows standard equipment to achieve the required precision without tool redesign, as the precision is built into the pre-formed components rather than requiring precise positioning during final assembly.
Solution Approach 2:
The connecting bars serve as intermediary elements that mediate between the base contact regions. They provide the precise gap width control through their own dimensions, acting as a buffer that decouples the gap width precision requirement from the base stamping process, allowing conventional tools to be used while still achieving high precision in the final assembly.
3Manufacturing precision
If additional cutting or milling steps are introduced to create narrow gaps, then gap width precision is improved, but device complexity and production time increase
Solution Approach 1:
The lead frame is segmented into pre-formed components (base and connecting bars) that can be manufactured using standard stamping processes. This segmentation eliminates the need for additional cutting or milling steps to create narrow gaps, as the precise gap widths are achieved through the assembly of pre-formed components with controlled dimensions, reducing overall device complexity and production steps.
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 enables the production of lead frames with narrow, uniform gaps suitable for very small LED die packages at a lower cost and with greater efficiency, without the need for expensive tooling modifications, facilitating the use of small LED die packages in LED lighting devices.
Implementation Method 1
deforming at least one connecting bar of the stamped lead frame to reduce the gap width between complementary contact regions
Implementation Method 2
The lead frame also acts as a primary heat spreader, since it is directly connected to the LED package
Data Source
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AI summary
The invention describes a method of manufacturing a lead frame (1), comprising the steps of preparing a stamping arrangement (4) to stamp a lead frame (1) comprising a plurality of electrode contact regions (2), wherein complementary contact regions (2) are separated by an initial gap width (GS); and a number of connecting bars (10), wherein a connecting bar (10) extends between regions of the lead frame (1); using the stamping arrangement (4) to stamp the lead frame (1); and deforming at least one connecting bar (10) of the stamped lead frame (1) to reduce the gap width between complementary contact regions (2) to a final gap width (GD). The invention further describes a lead frame (1) comprising a plurality of LED electrode contact regions (2), manufactured using such a method, with a gap width (GD) of at most 250 μm between complementary contact regions (2) after the deformation step. The invention further describes an LED lighting device comprising such a lead frame (1) and at least one LED die package (6) mounted onto complementary electrode contact regions (2) of the lead frame (1).