Curved Lead Frame for Wide-Angle LED Emission
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Solution Overview
Problem
Conventional LED lamps with a flat substrate and hemispherical lenses inherently limit light emission to a Lambertian profile of 180 degrees, requiring additional secondary optics like reflectors to achieve wider emission profiles, which increases size and cost.
Innovation Solution
Bare LED dies are directly mounted on a curved lead frame strip for improved thermal conductivity, connected in series, and molded with lenses to enhance light extraction, allowing the lead frame strip to be bent for a wider emission profile exceeding 180 degrees, with a plastic body or rigid support maintaining the curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LEDs are mounted on a flat substrate with hemispherical lenses, then light extraction is improved, but the emission profile is limited to 180 degrees (Lambertian profile)
Solution Approach 1:
The patent applies curvature to the lead frame substrate, bending it into an arc shape to enable the LED array to emit light over angles greater than 180 degrees. This curved configuration allows the emission profile to extend to 270 degrees or more, resolving the limitation of flat substrates while maintaining effective light extraction through the curved geometry.
2Adaptability or versatility
If secondary optics like reflectors are added to achieve wider emission profiles, then the emission angle is increased, but the device size and cost increase
Solution Approach 1:
The patent extracts the need for secondary optics by using the lead frame substrate itself as the structural element that defines the emission profile. Instead of adding separate reflectors or optical components, the curved lead frame configuration alone achieves the wide-angle emission, eliminating additional parts and reducing device complexity.
Solution Approach 2:
The lead frame substrate serves multiple functions: it provides mechanical support for mounting LEDs, acts as a heat sink for thermal management, and through its curved configuration, defines the wide emission profile. This multi-functionality eliminates the need for separate components, reducing overall device size and complexity.
3Adaptability or versatility
If secondary optics like reflectors are added to achieve wider emission profiles, then the emission angle is increased, but cost increases
Solution Approach 1:
The patent merges the functions of the substrate, heat sink, and optical profile-defining elements into a single curved lead frame structure. This integration eliminates the need for separate secondary optics components, reducing part count, assembly complexity, and manufacturing cost while achieving the desired wide emission profile.
4Adaptability or versatility
If the lead frame strip is bent in an arc to achieve wider emission profile, then the emission angle exceeds 180 degrees, but continuous force is needed to maintain curvature
Solution Approach 1:
The patent applies the preliminary action principle by pre-bending the lead frame strip into the desired arc configuration during the manufacturing process before the LEDs are mounted and encapsulated. The encapsulant material is then molded over the pre-bent lead frame, locking the curvature in place. This eliminates the need for continuous force to maintain the arc shape during operation, as the structure is self-supporting.
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 solution enables a compact LED lamp with a light emission profile of up to 270 degrees, improving visibility from multiple angles without the need for additional optics, suitable for applications like motorcycle or automobile turn signals.
Implementation Method 1
bare LED dies have a bottom thermal pad or electrode directly bonded to a metal lead frame strip for good thermal conductivity
Implementation Method 2
Lenses are then molded over each of the LED dies and the associated lead frame strip portions to improve light extraction
Implementation Method 3
The LED dies or the lenses may include phosphor to create any color of emitted light
Data Source
Figure 1~5
Figure 6~7
AI summary
An LED lamp includes a metal lead frame strip (14) on which is directly mounted bare LED dies (12), such as in series. Therefore, there is excellent thermal conductivity to the lead frame (14). Lenses (24) are then molded over the LED dies (12) to encapsulate them. The lead frame (14) is then inserted into a mold for a thermally conductive plastic body (38) and is bent in an arc while in the mold so that the top surfaces of the LED dies (12) are not parallel to each other. The plastic body is molded, and the structure is removed from the mold. The curved lead frame causes the overall light emission to be very wide, such a greater than 270 degrees. In another embodiment, the lead frame strip is supported over a curved outer surface of a pre- molded plastic support. Ends of the lead frame strip are inserted into electrical connectors of the plastic support.