LED Lead Frame Assembly with Segmented Insulated Bars
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Solution Overview
Problem
Conventional lead frame assemblies for QFN packages face issues with warping due to thermal expansion coefficient differences between metal and plastic materials, leading to high damage rates and difficulties in testing individual LED packages, as they are mutually connected and require singulation for testing.
Innovation Solution
A lead frame assembly design featuring spaced-apart insulated bars and electrically isolated lead frame sets, which reduces residual stress and material consumption, allowing for direct testing and adjustment of phosphor layer distribution, thereby minimizing warping and enhancing testing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If insulated housings are formed by injection molding on the metallic substrate, then the lead frame assembly structure is completed, but warping is generated due to thermal expansion coefficient difference between plastic and metal materials
Solution Approach 1:
The patent divides the insulated housing into multiple separate insulated bars instead of forming a single large interconnected housing. Each insulated bar is positioned between adjacent lead frame sets and is electrically isolated from others. This segmentation reduces the overall area of plastic material in contact with the metal substrate, thereby reducing residual stress and warping caused by thermal expansion coefficient differences.
2Stability of the object's composition
If lead frame sets are mutually connected to form a complete assembly, then the assembly structure is intact, but electrical connection between adjacent LED packages prevents direct testing of individual packages
Solution Approach 1:
The patent electrically isolates adjacent lead frame sets by positioning insulated bars between them and designing the lead frame sets with disconnected adjacent sides. This allows each LED package to be electrically independent while remaining structurally part of the same assembly, enabling direct testing of individual packages without requiring singulation.
Solution Approach 2:
The insulated bars serve as intermediary elements that provide both mechanical support and electrical isolation between adjacent lead frame sets. These bars allow the assembly to maintain structural integrity while preventing electrical interference between neighboring packages, thus enabling independent testing.
3Area of stationary object
If a large area plastic structure is used for insulated housings, then complete coverage is achieved, but material consumption increases and cost rises
Solution Approach 1:
The patent uses multiple small insulated bars instead of a single large plastic housing to achieve the same protective coverage. This segmented approach reduces the total volume of plastic material required while maintaining adequate insulation and structural support for all lead frame sets in the 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 solution effectively reduces warping and material costs, enables direct testing of LED packages, and improves the accuracy of color coordinates by allowing electrical isolation of lead frame sets, facilitating efficient packaging and testing processes.
Implementation Method 1
Since the thermal expansion coefficient of a plastic structure made of plastic material differs from metallic substrate made of a metal material, during formation of the insulated housings, warping of the lead frame assembly is likely to be generated
Data Source
AI summary
A lead frame assembly includes a surrounding frame and a plurality of lead frame sets arranged in a matrix. Each lead frame set includes spaced-apart first and second lead frames and a connecting structure interconnecting one of the lead frame sets to an adjacent lead frame set. Each lead frame set is further connected to the surrounding frame through the connecting structure thereof. A plurality of insulated bars are spacedly formed on a lead frame panel. Each insulated bar covers a corresponding row of the lead frame sets and exposes bottom surfaces of the first and second lead frames. Each insulated bar further covers portions of the surrounding frame that are adjacent to two opposite outermost ones of the lead frame sets.