LED Package Leads with Recess for Accurate Chip Mounting
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Solution Overview
Problem
Conventional light emitting devices with resin packages face issues such as burr formation during manufacturing, leading to reduced strength and accuracy in mounting light emitting elements, and difficulties in achieving high optical output and reliability at a low cost.
Innovation Solution
The light emitting device design features leads that are not exposed on opposing side surfaces but rather on surfaces perpendicular to them, with a curved or beveled cross-sectional profile and different slope angles for the resin and lead surfaces, enhancing strength and allowing for burr removal, and a method of manufacturing that involves coining the lead frame to prevent burr formation and ensure accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the recess portion is enlarged to accommodate burr, then the light emitting element can be mounted, but the overall package size becomes unnecessarily large
Solution Approach 1:
The patent applies preliminary action by forming a recess in the lead frame at the position corresponding to the light emitting element mounting area before the molding process. This pre-formed recess prevents burr formation during molding by providing a designated space for the element, thereby maintaining compact package dimensions while ensuring accurate mounting without requiring post-manufacturing burr accommodation.
Solution Approach 2:
The lead frame serves as an intermediary component that bridges the molding process and the final package structure. By incorporating a recess in the lead frame, it mediates between the molding pressure and the light emitting element, preventing burr formation while maintaining precise element positioning and compact overall package size.
2Manufacturing precision
If the recess portion is enlarged to accommodate burr, then the light emitting element can be mounted, but the strength of the package is reduced
Solution Approach 1:
The recess is preliminarily formed in the lead frame before molding, creating a precise cavity that accommodates the light emitting element without requiring excessive material removal or enlargement. This pre-defined space maintains the structural integrity of the package while ensuring accurate element mounting.
Solution Approach 2:
The recess creates a localized area with different geometric properties specifically at the element mounting position, while the rest of the package maintains its original strength characteristics. This local modification ensures precise element accommodation without compromising overall package strength.
3Illumination intensity
If the metal wiring is widely exposed at the bottom surface and the recess is formed as a reverse truncated cone, then light reflection is improved, but the bonding surface area between metal and resin is reduced
Solution Approach 1:
The lead frame is preliminarily formed with a recess and metal wiring configuration before the resin molding process. This preliminary structure ensures that the metal wiring is positioned to maximize light reflection while maintaining adequate bonding surface area with the resin, as the resin flows into and bonds with the pre-configured metal structures.
Solution Approach 2:
The patent creates a composite structure combining metal wiring, resin, and the light emitting element within the recess. The metal wiring provides both electrical connection and light reflection functions, while the resin provides structural support and bonding, creating a synergistic composite material system that achieves both optical performance and mechanical strength.
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 design results in a strong resin package that enables high-accuracy mounting of light emitting elements with a small pitch, improved bonding strength, and reduced production time, while minimizing burr occurrence and package size, thus enhancing the overall performance and cost-effectiveness of the light emitting device.
Implementation Method 1
a region constituting an inner bottom surface of the recess portion is formed lower than peripheral portions of the lead by strongly pressing the lead frame with a protruding portion of a mold
Implementation Method 2
a thermosetting resin composition for reflecting light is injected, then is molded by way of thermal pressure molding using a transfer mold apparatus
Implementation Method 3
a thermosetting resin compact is disposed on the printed-wiring board and lead frame having a flat plate shape which results in a small bonding surface area
Data Source
Figure 1
Figure 2A~2C
Figure 3A
AI summary
The light emitting device (100) includes a resin package (20) provided with a recess portion (27), a light emitting element (10) housed in the recess portion (27), a sealing member (30) filled in the recess portion (27) and covering the light emitting element (10), in which the resin package (20) has leads (22a, 22b) which are not exposed two opposing outer side surfaces (20d) but are exposed from two opposing outer side surfaces which are perpendicular with the outer side surfaces (20d) , a resin portion (25) is integrally molded with the leads (22a, 22b), the upper surfaces of the leads (22a, 22b) are exposed from the resin portion 25 to the inner bottom surface (27a) of the recess portion (27), and the top surfaces of the leads (22a, 22b) are formed such that the region constituting the inner bottom surface of the recess portion (27) are lower than their peripheral region.