LED Lead Frame Anchoring Structure for Reflow-Resistant Molding
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Solution Overview
Problem
The existing light emitting devices with a molding unit formed only on the top surface of the lead frame face issues with separation due to increased ambient temperature during the reflow process, leading to potential damage from exposure to air or moisture and bending issues, which compromises the adhesive force between the lead frame and the molding unit.
Innovation Solution
The design incorporates fixing spaces through the lead frame with outer and inner fixing holes and stepped or inclined sidewalls, allowing the molding unit to be integrally formed on the top surface and within the lead frame, enhancing the adhesive force by creating a secure monolithic bond between the molding unit and the lead frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the molding unit is formed only on the top surface of the lead frame, then the manufacturing process is simple, but the adhesive force between the lead frame and molding unit is insufficient causing separation
Solution Approach 1:
The invention transitions from forming the molding unit only on the top surface (2D) to forming it through the entire lead frame body including bottom and side surfaces (3D). The molding unit is formed by injecting molding compound into cavities that penetrate through the lead frame, creating anchor points that extend into the lead frame body, thereby dramatically improving adhesive force and preventing separation.
2Device complexity
If the molding unit is formed only on the top surface, then the structure is simple, but the boundary surface widens due to separation under thermal stress
Solution Approach 1:
The molding unit is nested within cavities that penetrate through the lead frame body. These cavities create interlocking anchor points where the molding compound is embedded within the lead frame structure itself, forming a nested configuration that prevents separation and maintains boundary surface stability under thermal stress during reflow processing.
3Device complexity
If the molding unit separates from the lead frame, then the structure becomes loose, but the light emitting diode chip and wires are exposed to air and moisture
Solution Approach 1:
By forming the molding unit through the entire lead frame body using penetrating cavities, the invention creates a three-dimensional protective enclosure that completely seals the light emitting diode chip and wires. This 3D molding structure eliminates gaps and exposure to harmful environmental factors such as air and moisture, providing comprehensive protection.
Data Source
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Figure 3A~3B
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AI summary
Provided is a light emitting device. The light emitting device includes: a plurality of lead frame units spaced apart from each other, each of the lead frame units being provided with at least one fixing space perforating a body thereof in a vertical direction; a light emitting diode chip mounted on one of the lead frame units; and a molding unit that is integrally formed on top surfaces of the lead frame units and in the fixing spaces to protect the light emitting diode chip.