Semiconductor Light Emitting Device Mounting Substrates With Conductive Leads
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Solution Overview
Problem
Semiconductor light emitting devices face reliability issues due to high thermal impedance and thermal mismatch among different materials in multipart packages, leading to assembly complexities and encapsulant delamination problems during temperature cycles.
Innovation Solution
A thermally conductive mounting block with a cavity for mounting semiconductor light emitting devices, featuring conductive leads isolated from the block, a reflective coating, and a flexibly fitted lens with phosphor coating, which provides improved thermal spreading and optical coupling, enabling surface mount technology compatibility and reduced delamination risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-piece package with different materials (alumina substrate and silver plated copper substrate) is used, then external electrical connections and heat sinking are provided, but thermal impedance increases and thermal mismatch causes reliability problems
Solution Approach 1:
The patent combines multiple functions (mounting, heat sinking, electrical connection) into a single substrate integrated with conductive leads, eliminating the two-piece structure. The substrate includes a mounting surface for the LED and has conductive leads extending through it, integrating what was previously separate components into one unified structure that reduces thermal impedance and thermal mismatch.
Solution Approach 2:
The substrate is made of a material that provides both mechanical support and thermal management properties, potentially using composite or specially formulated materials that balance thermal conductivity, mechanical strength, and electrical isolation properties to resolve the thermal mismatch issue between different materials.
2Ease of manufacture
If a two-piece package structure is used, then electrical connections are provided, but assembly becomes more complicated due to increased piece part counts
Solution Approach 1:
The patent integrates the substrate and conductive leads into a single component, reducing the piece part count from multiple separate components (substrate, leads, mounting block) to a more integrated structure. This simplifies assembly by reducing the number of parts that need to be handled and positioned during manufacturing.
3Reliability
If a molded plastic body is used to wrap around the heat-slug, then the package structure is formed, but the package cannot withstand solder reflow temperatures
Solution Approach 1:
The patent removes the molded plastic body that cannot withstand high temperatures and replaces it with a substrate structure that can. The conductive leads are electrically isolated from the substrate, allowing the substrate to be made of temperature-resistant material while still providing electrical connection functionality.
Solution Approach 2:
The substrate material properties are selected to withstand solder reflow temperatures, changing the thermal and mechanical parameters of the package structure. The conductive leads are isolated from the substrate to prevent thermal stress transmission, allowing the package to survive high-temperature soldering processes without delamination.
4Adaptability or versatility
If a sheet metal optical cavity is used, then light reflection is achieved, but the cavity depth and shape configurations are limited
Solution Approach 1:
The substrate integrates the optical cavity function with the mechanical support function, using materials and structures that allow greater design flexibility for cavity depth and shape compared to traditional sheet metal construction. The conductive leads extending through the substrate provide electrical connection without constraining the cavity geometry.
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 enhances thermal performance, reduces thermal impedance, and improves reliability by allowing the semiconductor light emitting device package to withstand solder reflow temperatures and maintain optical coupling integrity during temperature changes.
Implementation Method 1
a cavity that is configured to mount a semiconductor light emitting device therein and to reflect light that is emitted by the semiconductor light emitting device that is mounted therein away from the cavity
Implementation Method 2
A conductive lead inserted into the mounting block extends into the cavity. The conductive lead is electrically isolated from the mounting block and has an exposed contact portion in the cavity
Implementation Method 3
A thermally conductive mounting block... enhances thermal performance, reduces thermal impedance
Implementation Method 4
a flexibly fitted lens with phosphor coating, which provides improved thermal spreading and optical coupling
Data Source
AI summary
A mounting substrate for a semiconductor light emitting device includes a thermally conductive mounting block. The mounting block has, in a first face thereof, a cavity that is configured to mount a semiconductor light emitting device therein and to reflect light that is emitted by the semiconductor light emitting device that is mounted therein away from the cavity. A conductive lead inserted into the mounting block extends into the cavity. The conductive lead is electrically isolated from the mounting block and has an exposed contact portion in the cavity. The conductive lead may be a plurality of conductive leads each having an exposed contact portion at different locations in the cavity. Related packaging methods also may be provided.