LED Lead Frame Coplanar Design for Thermal and Mechanical Stability
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Solution Overview
Problem
Conventional LED light emitting devices face issues with lead terminal bending, oxidation, and mechanical stability, leading to poor adhesion, increased thickness, and reduced efficiency due to the need for long lead terminals, which can cause misalignment and damage during mass production.
Innovation Solution
A semiconductor light emitting device design featuring a package with a recessed opening, a first lead for thermal conduction, and a second lead with a peripheral region for wire bonding, where the leads are formed with outer projections to reduce the need for bending and minimize cut surface exposure, enhancing adhesion and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the lead terminal portion is bent to extend along the side and bottom surfaces of the package, then the alignment along side and bottom surfaces is adjusted, but the device thickness increases and the lead terminal portion resistance increases
Solution Approach 1:
Instead of bending the lead terminal portion to achieve alignment, the patent inverts the approach by making the lead terminal portion coplanar with the bottom surface of the package. This eliminates the need for bending while maintaining proper alignment, thereby reducing device thickness and lead resistance.
2Ease of operation
If the lead terminal portion is made long to allow bending, then the alignment adjustment is possible, but the lead terminal portion may be bent at undesired angle or cut off during mass production
Solution Approach 1:
The patent eliminates the need for bending operations by designing the lead terminal portion to be coplanar with the package bottom surface from the outset. This inversion of the traditional bending approach prevents production issues such as undesired bending angles or accidental cutting during mass production, while still achieving proper alignment.
3Reliability
If the lead terminal portion is bent to extend along the side and bottom surfaces, then the electrical connection is established, but the number of leads that can be arranged in patterns in one sheet of lead frame decreases
Solution Approach 1:
By inverting the traditional bent lead configuration to a coplanar configuration, the patent reduces the space required for each lead terminal portion. This allows more leads to be arranged in patterns on a single lead frame sheet, thereby improving production efficiency while maintaining reliable electrical connections.
4Productivity
If the lead terminal portion is cut to separate individual light emitting devices, then the devices are separated, but the cut surface is not plated and prone to oxidation
Solution Approach 1:
The patent applies plating to the lead terminal portion before the cutting process. This preliminary action ensures that the cut surfaces, which will be exposed after separation, already have a plated protective layer. This prevents oxidation and maintains good adhesion properties, eliminating the need for post-cutting plating operations.
5Reliability
If the lead terminal portion is made long and bent, then the electrical connection is established, but the sharp cut surface may damage other semiconductor light emitting devices
Solution Approach 1:
By inverting the traditional bent lead configuration to a coplanar configuration, the patent eliminates the sharp edges that would be created by bending and cutting long lead terminals. The coplanar lead terminal portions have smoother edges that are less likely to damage other semiconductor devices during handling and assembly.
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 design improves thermal conductivity, reduces the risk of oxidation, and increases production efficiency by eliminating the need for lead bending, resulting in a more stable and cost-effective LED light emitting device with improved alignment and reduced defects.
Implementation Method 1
a first lead (101) having a top surface which the light emitting element is mounted thereon
Data Source
AI summary
A light emitting device includes a first lead and a second lead. The first lead has a top surface which a light emitting element is mounted thereon and a bottom surface opposed to the top surface. The second lead has a lead peripheral region where a wire connected to an electrode of the light emitting element is bonded therewith. The first lead includes a lead middle region where the semiconductor light emitting element is mounted thereon to thermally conduct therewith. A bottom surface of the lead middle region is exposed from a package. The second lead has an outer lead region that is projected outwardly from the both side surfaces of the package. The bottom surface of the first lead middle region is substantially coplanar with a bottom surface of the outer lead region.