LED Package Leadframe Segmentation for Resin Crack Prevention
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Solution Overview
Problem
Existing surface mount device (SMD) type light emitting diodes (LEDs) face issues with crack or fracture of the resin case due to external shocks or temperature changes, leading to detachment from the leadframe, particularly in packages with a long and narrow shape, which compromises long-term reliability.
Innovation Solution
A light emitting apparatus package design featuring first and second leadframes with extension portions of reduced width, arranged on either side of a third leadframe, where the resin portion is integrally formed with the leadframes, providing enhanced stress resistance and adhesive strength, and includes a recessed portion for efficient light emission and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a long and narrow package shape is used for the light emitting apparatus, then the package can achieve compact dimensions and efficient light emission, but the resin case becomes susceptible to cracks and fractures under external shocks or temperature changes
Solution Approach 1:
The leadframe is divided into multiple segments including a body portion and multiple extension portions that extend in different directions. This segmentation allows the leadframe to distribute and absorb external shocks and thermal stresses across different sections, preventing stress concentration that would cause resin case fracture in compact long-narrow packages.
Solution Approach 2:
The extension portions of the leadframe are strategically positioned at specific locations (such as corners and edges) of the resin case to provide localized reinforcement. This local quality enhancement strengthens the resin case at critical stress points without increasing the overall package volume, maintaining compact dimensions while improving reliability.
2Volume of moving object
If the resin case is made thinner to reduce package size, then the package becomes more compact, but the adhesive strength between the resin case and leadframe decreases, leading to detachment
Solution Approach 1:
The leadframe extension portions extend in multiple directions (length, width, and depth dimensions) to create a three-dimensional reinforcement structure. This multi-dimensional approach increases the bonding surface area and mechanical interlocking between the leadframe and resin case, compensating for the reduced resin thickness without increasing package volume.
Solution Approach 2:
The package combines the resin case material with the metal leadframe material in a composite structure where the leadframe extension portions are embedded within or bonded to the resin case. This composite construction provides both mechanical strength and adhesive bonding, maintaining compact package size while preventing detachment.
3Reliability
If extension portions are added to the leadframe to improve stress resistance, then the reliability of the resin case improves, but the device complexity increases
Solution Approach 1:
The leadframe extension portions serve multiple functions simultaneously: they provide mechanical reinforcement to prevent resin case fracture, act as bonding anchors to prevent detachment, and can also serve as mounting structures for additional components. This multi-functionality reduces the need for separate structural elements, maintaining relatively simple device complexity while improving reliability.
Data Source
AI summary
A light emitting apparatus includes a package having a long-length direction and a short-length direction perpendicular to the long-length direction as viewed in plan view. The package includes first and second leadframes and a resin portion. The first leadframe has a first leadframe main portion and a first leadframe extension portion which has narrower width than that of the first leadframe main portion. The second leadframe has a second leadframe main portion and a second leadframe extension portion which has narrower width than that of the second leadframe main portion. An inclined portion is formed between the first leadframe and the second leadframe as viewed in plan view. An upper end of the inclined portion is shifted from a lower end of the inclined portion.