Side-Mountable LED Package SMT Compatibility
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Solution Overview
Problem
Existing semiconductor light emitting device packages are not surface mount technology (SMT) compatible due to packaging materials that cannot withstand solder reflow temperatures and often experience encapsulant delamination or bubble formation, which affects device reliability, and they lack the ability to provide narrow angle illumination necessary for applications like cellular phone screens.
Innovation Solution
A side-mountable semiconductor light emitting device package design featuring an electrically insulating substrate with conductive contacts and a reflector cavity, using a thermally conductive dielectric material, and encapsulant with additives for optical properties, allowing for selective angular orientation and mounting on an underlying surface with a narrow angle of illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a molded plastic body with soft encapsulant is used to package the semiconductor light emitting device, then the device provides environmental protection and structural support, but the packaging materials cannot withstand solder reflow temperatures and the encapsulant tends to form bubbles or delaminate, adversely affecting device reliability
Solution Approach 1:
The patent changes the material parameters by replacing the soft encapsulant with a rigid or semi-rigid epoxy compound that has higher thermal stability and structural integrity. This epoxy compound can withstand solder reflow temperatures without deforming or delaminating, thereby eliminating the reliability issues associated with soft encapsulants while maintaining environmental protection and structural support functions.
Solution Approach 2:
The patent employs a composite packaging structure consisting of a rigid substrate, epoxy compound encapsulant, and optional lens material. This composite construction combines the thermal stability and mechanical strength of the epoxy with the optical properties of the lens, creating a package that simultaneously achieves high reliability, bubble-free encapsulation, and proper light transmission.
2Adaptability or versatility
If conventional packaging materials are used, then the device structure is simple and manufacturing is easier, but the packaging materials generally cannot withstand solder reflow temperatures, making the device incompatible with surface mount technology
Solution Approach 1:
The patent changes the thermal parameter of the packaging materials by selecting an epoxy compound with a glass transition temperature and curing characteristics that exceed solder reflow temperatures. This allows the package to withstand the thermal stress of SMT processing without softening or deforming, enabling surface mount technology compatibility while maintaining structural integrity throughout the manufacturing process.
3Illumination intensity
If a standard LED package design is used, then the manufacturing process is straightforward, but the device cannot provide narrow angle illumination necessary for applications like cellular phone screens
Solution Approach 1:
The patent employs a lens with a specific curved surface geometry mounted on the LED chip. This spherical or aspherical lens design focuses and directs the emitted light into a narrow beam, achieving the required narrow angle of illumination for applications like cellular phone screens. The curved surface optimizes light extraction and directional control without requiring complex multi-element optical systems.
Solution Approach 2:
The patent applies different material properties and structural characteristics to different regions of the package. The lens region is optimized for optical performance with specific curvature and material composition to achieve narrow beam emission, while the epoxy encapsulant region provides structural support and environmental protection. This localized optimization allows the package to achieve narrow angle illumination without unnecessarily increasing overall structural complexity.
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
The solution enables SMT compatibility, improves reliability by preventing delamination, and provides a narrow angle of illumination suitable for applications like cellular phone screens, while maintaining structural integrity and optical performance.
Implementation Method 1
using a thermally conductive dielectric material
Implementation Method 2
A reflector assembly is mounted on the front face of the substrate that includes a plurality of reflector cavities
Data Source
AI summary
Side-mountable semiconductor light emitting device packages include an electrically insulating substrate having a front face and a back face and a side face extending therebetween. The side face is configured for mounting on an underlying surface. An electrically conductive contact is provided proximate an edge of the substrate on the back face of the substrate and/or on a recessed region on the side face of the substrate. The contact is positioned to be positioned proximate an electrical connection region of the underlying surface when the semiconductor light emitting device package is side mounted on the underlying surface. A conductive trace extends along the front face of the substrate and is electrically connected to the contact. A semiconductor light emitting device is mounted on the front face of the substrate and electrically connected to the conductive trace.