Lead Frame Curvature Radii for Burr Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lead frame manufacturing processes result in burred edges, which can cause damage and reduce mountability of light emitting devices due to exposed burrs and resin penetration during resin molding, leading to adverse effects on adhesion to circuit boards.
Innovation Solution
The lead frames are designed with specific curvature radii for electrodes and hanger leads, and a method involving press-punching and resin molding where burred faces face inward, preventing burrs from forming on the mounting surface and ensuring the resin does not penetrate, thus enhancing mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If press-punching is used to manufacture lead frames, then manufacturing efficiency is improved, but burred edges are generated on the metal sheet
Solution Approach 1:
The patent applies different curvature radii to different locations of the lead frame components. Specifically, the electrode has a first curvature radius at its corner while the hanger lead has a second curvature radius at its corner, where these radii are deliberately different. This local differentiation allows the electrode to have a larger radius that prevents burr formation and exposure, while the hanger lead can have a smaller radius optimized for its function of biting into the support member.
2Object-affected harmful factors
If burred faces are oriented to face away from support members, then burrs are exposed and can damage other members, but orienting them toward support members causes resin penetration and adhesion issues
Solution Approach 1:
The patent creates different curvature characteristics at different locations: the electrode corner has a first curvature radius that is larger than the hanger lead corner's second curvature radius. This local differentiation ensures that when the burred face is oriented away from the support member, the electrode's larger radius prevents burr exposure and damage, while the hanger lead's smaller radius maintains its ability to bite into the support member effectively.
3Ease of operation
If hanger leads have small curvature radius, then they can bite into support members effectively, but they may generate more burrs
Solution Approach 1:
The patent assigns different curvature radii to different functional elements: the hanger lead has a second curvature radius at its corner that is smaller than the electrode's first curvature radius. This allows the hanger lead to maintain a sharp edge for effective biting into the support member, while the electrode has a larger radius that prevents burr exposure. The differentiation resolves the contradiction by optimizing each element's radius for its specific function.
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 approach results in packages and light emitting devices with improved mountability by preventing burrs and resin penetration, ensuring a flat mounting surface and reducing the risk of adhesion issues during assembly.
Implementation Method 1
press-punching a metal sheet to form the lead frame such that a radius of curvature at a corner of a lower face of each of electrodes is larger than a radius of curvature at a corner of an upper face of each of the electrodes
Implementation Method 2
a method involving press-punching and resin molding where burred faces face inward, preventing burrs from forming on the mounting surface and ensuring the resin does not penetrate
Data Source
AI summary
A method for producing a lead frame includes press-punching a metal sheet to form the lead frame such that a radius of curvature at a corner of a lower face of each of electrodes is larger than a radius of curvature at a corner of an upper face of each of the electrodes while a radius of curvature at a corner of a lower face of each of hanger leads is smaller than a radius of curvature at a corner of an upper face of each of the hanger leads. The lead frame includes the electrodes, the hanger leads spaced apart from the electrodes, and an outer frame attached to the electrodes and the hanger leads. The lead frame partially defines a box-shaped package that defines a first recess having an opening defining by the support member and a bottom face at least partially formed by the electrodes.