Compression Molded LED Packaging with Front Contacts
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Solution Overview
Problem
Semiconductor light emitting devices face challenges with multipart packaging that leads to higher thermal impedance, reliability issues, and increased costs due to material mismatches and complex assembly processes, as well as limitations in optical cavity design and encapsulant degradation under blue light exposure.
Innovation Solution
The method involves compression molding an optical element directly onto the semiconductor light emitting device on a substrate with front-side electrical contacts, using silicone and a release layer to form lenses without damaging the contacts, and optionally adding a second optical element with different properties to enhance light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-piece package with separate substrates is used, then external electrical connections and heat sinking are provided, but thermal impedance increases and thermal mismatch occurs among components
Solution Approach 1:
The patent merges the first substrate (alumina/aluminum nitride with electrical traces) and the second substrate (silver plated copper heat sink) into a single integrated substrate structure. This unified substrate eliminates the interface between separate substrates, reducing thermal impedance and preventing thermal mismatch while maintaining both electrical connection and heat sinking functions in one component.
2Adaptability or versatility
If a sheet metal optical cavity is used, then the semiconductor device is enclosed, but the cavity depth and shape configurations are limited
Solution Approach 1:
The patent changes the manufacturing parameters and material properties by using compression-molded epoxy resin instead of sheet metal for the optical cavity. This allows the cavity to be formed with varied depths and complex three-dimensional shapes that are not achievable with sheet metal fabrication, while simplifying the manufacturing process through molding rather than mechanical fabrication.
3Strength
If epoxy is used to encapsulate the device, then structural strength is provided, but the epoxy degrades under blue light electromagnetic energy and becomes less transmissive
Solution Approach 1:
The patent uses a composite encapsulant material consisting of silicone resin combined with phosphor particles. The silicone resin provides the necessary structural strength and environmental protection, while the phosphor particles absorb the harmful blue light electromagnetic energy and convert it to lower energy wavelengths, preventing degradation of the encapsulant and maintaining optical transmissivity over time.
4Reliability
If pre-molded lenses are attached by adhesive, then optical functionality is achieved, but the manufacturing process is inconsistent and reliability is reduced
Solution Approach 1:
The patent merges the lens formation process with the encapsulant application by incorporating lens-forming particles into the encapsulant material itself. During the single-step compression molding process, both the encapsulant and the optical lens structure are formed simultaneously, eliminating the separate adhesive attachment step and ensuring consistent manufacturing with improved reliability.
5Ease of manufacture
If casting is used to encapsulate LED devices, then the process can be applied to open chambers, but the epoxy level adjusts freely during curing causing inconsistency
Solution Approach 1:
The patent applies preliminary action by pre-forming the encapsulant material with embedded lens particles in a mold cavity before placing the LED device. The compression molding process then consolidates the material under controlled pressure, ensuring the encapsulant reaches the precise desired level and shape without free adjustment during curing, thereby achieving both ease of manufacture and manufacturing precision.
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 reduces thermal mismatch, simplifies assembly, enhances optical properties, and improves the robustness and longevity of the packaged device by allowing direct contact molding and tailored optical elements, while minimizing encapsulant issues and costs.
Implementation Method 1
compression molding an optical element directly onto the semiconductor light emitting device
Implementation Method 2
using silicone and a release layer to form lenses without damaging the contacts
Data Source
AI summary
Methods of packaging a semiconductor light emitting device include providing a substrate having the semiconductor light emitting device on a front face thereof and a contact on a front face thereof, wherein the light emitting device is electrically connected to the contact on the front face of the substrate. The substrate is compression molded to form an optical element on the front face of the substrate over the semiconductor light emitting device and a residual coating over a region of the front face of the substrate including the contact. The residual coating over the contact may be removed without damaging the contact. Packaged semiconductor light emitting devices are also provided.