Light Emitting Device Lead Grooves for Adhesion and Burr Control
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Solution Overview
Problem
Existing light emitting device manufacturing methods face challenges in achieving effective heat dissipation and preventing soldering flux invasion due to burr formation and poor bonding between the molded resin and leads, leading to reduced adhesion and increased risk of resin separation during reflow soldering.
Innovation Solution
The method involves forming grooves on the leads within the molded resin package, with the grooves positioned under the corners of the metal mold's convex portions to prevent burr formation and enhance adhesion by creating a synergistic thermal expansion effect between the sealing resin and the molded resin, which increases the adhesion area and resistance against soldering flux invasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If grooves are formed on leads and filled with molded resin, then adhesion area between lead and molded resin increases, but burr formation occurs at corners of metal mold convex portions
Solution Approach 1:
The patent applies different surface treatments to different regions of the metal mold convex portions. Specifically, the corner portions are treated to have a larger radius of curvature than the central portions, creating local quality variations that prevent burr formation at corners while maintaining adhesion enhancement in groove regions through controlled resin filling.
Solution Approach 2:
The patent performs preliminary action by pre-forming grooves on the leads before the molding process. These grooves are positioned to correspond with the convex portions of the metal mold, allowing the molded resin to be pre-directed into these grooves during molding, thereby enhancing adhesion before any potential burr formation issues arise.
2Strength
If molded resin is filled into grooves on leads, then bonding between molded resin and leads is strengthened, but resin separation risk increases during reflow soldering due to poor adhesion in conventional methods
Solution Approach 1:
The patent changes the geometric parameters of the metal mold convex portions, specifically increasing the radius of curvature at corner portions. This parameter change modifies the flow and distribution of molded resin during the molding process, ensuring better adhesion and preventing resin separation during subsequent reflow soldering by eliminating poor adhesion zones that would otherwise form at sharp corners.
Solution Approach 2:
The patent creates a composite structure by filling grooves on the leads with molded resin, forming a composite material system that combines the metallic lead with the polymeric resin. This composite construction enhances the overall bonding strength and creates a more reliable joint that resists separation during thermal cycling in reflow soldering processes.
3Manufacturing precision
If chamfered corners are used on metal mold convex portions, then burr formation is reduced, but heat dissipation efficiency decreases
Solution Approach 1:
The patent applies local quality by differentiating the radius of curvature between corner portions and central portions of the metal mold convex portions. The corner portions have larger radii to prevent burr formation, while the central portions maintain smaller radii to preserve heat dissipation efficiency. This localized differentiation allows simultaneous achievement of both manufacturing precision and thermal performance.
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
This configuration effectively enhances heat dissipation, prevents burr formation, and strengthens the bonding between the molded resin and leads, reducing the risk of resin separation and improving the resistance against soldering flux invasion, resulting in a more reliable and efficient light emitting device manufacturing process.
Implementation Method 1
enhance adhesion by creating a synergistic thermal expansion effect between the sealing resin and the molded resin
Data Source
AI summary
A light emitting device including a molded package having leads including a pair of a first lead and a second lead, a molded resin, and a recess, where an upper surface of the leads is partially exposed from a bottom surface of the recess. The device further including a light emitting component mounted on the bottom surface, and at least one sealing member located in the recess to cover the light emitting component. At least one of the first lead and the second lead has a groove on an upper surface thereof, where the groove is positioned so as to correspond to a corner on the bottom surface of the recess in a cross sectional view. A portion of the molded resin located within the groove is exposed from the bottom surface. A surface of the corner is composed of a curved surface, and the sealing member covers the corner.