LED Encapsulation Molding With Separated Filler and Matrix Injection
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Solution Overview
Problem
Vacuum injection molding (VIM) faces challenges with high coefficient of thermal expansion (CTE) in semiconductor devices, leading to substrate bending, reliability issues, and limitations in filler content due to increased viscosity, which restricts material selection and component layout.
Innovation Solution
A method involving separate steps for introducing filler and matrix material into a mold under negative pressure, allowing for high filler content and flexible particle size selection, with the filler being free-flowing and comprising materials like spherical SiO2 particles, and the matrix material being low-viscosity silicone or epoxy resins, to achieve improved fill levels and reduced delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If filler content is increased to reduce CTE, then thermal expansion matching improves, but viscosity increases significantly making complete encapsulation impossible
Solution Approach 1:
The encapsulation process is divided into two separate steps: first introducing filler material to achieve high filler content (80-98%) for CTE matching, then separately introducing matrix material to complete the encapsulation. This segmentation allows each material to be optimized independently without the viscosity constraints of a pre-mixed high-filler compound.
Solution Approach 2:
The filler material is introduced and positioned in the mold cavity before the matrix material. This preliminary action ensures that the high-filler-content material is already in place to provide CTE matching, while the subsequent matrix material introduction completes the encapsulation without being constrained by the high viscosity that would result from pre-mixing both materials.
2Stability of the object's composition
If high filler content is used to adapt CTE, then thermal expansion is reduced, but closing forces and filling pressure increase considerably
Solution Approach 1:
The mold filling process is segmented into two separate material introductions: first the filler material (which provides CTE adaptation) and then the matrix material. This segmentation allows the filler to be introduced without the need for high closing forces that would be required if both filler and matrix were pre-mixed at high filler content, as the matrix material is introduced separately after the filler is in place.
3Illumination intensity
If smaller filler particles are used to improve optical properties, then light guide performance improves, but viscosity of mold compound increases
Solution Approach 1:
The introduction of filler and matrix material is segmented into separate steps. This allows small filler particles to be used to achieve high optical contrast and good light guide properties without being constrained by viscosity issues, since the filler is introduced separately before the matrix material rather than being pre-mixed at high concentrations.
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 enables high filler content exceeding 80% with reduced closing forces and filling pressure, allowing for better fill distribution and adaptation to local requirements, while minimizing delamination and mechanical stress, and providing flexibility in filler selection and size distribution.
Implementation Method 1
Negative pressure is then generated in the cavity of the mold and a matrix material is introduced into the filler. The negative pressure distributes the low-viscosity matrix material completely into the cavities between the filler.
Implementation Method 2
The matrix material is cured and the auxiliary carrier with the light-emitting devices is formed.
Data Source
AI summary
In an embodiment a method for manufacturing a plurality of light emitting devices includes arranging, fixing and wiring several semiconductor elements on a substrate, optional fastening of the substrate via an adhesive layer on an auxiliary carrier, introducing a filler into spaces between the semiconductor elements, inserting the substrate with the semiconductor elements attached thereto and the filler into a cavity of a molding tool, generating a vacuum in the cavity of the mold, introducing a matrix material into the filler, curing of the matrix material, molding the substrate with the light-emitting devices and separating the devices.