LED Module Overmolding with AuSn Alloy to Prevent Barrier Yellowing
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Solution Overview
Problem
Conventional silicon-based adhesives in LED modules have low thermal conductivity, leading to heat dissipation issues and efficiency degradation, while epoxy-based silver paste improves heat dissipation but affects light output, and the Au x Sn y alloy used for bonding can yellow and cause gaps, reducing luminous flux and service life.
Innovation Solution
The method involves attaching LED dies to substrates using Au x Sn y alloy before overmolding with a molding material, avoiding high temperature exposure that causes yellowing and gaps, and using a mold to protect the dies during overmolding, ensuring effective thermal conductivity and minimal light output impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Au x Sn y alloy is used for bonding LED die to substrate, then thermal conductivity is improved, but yellowing phenomenon occurs and gaps form during high temperature melting process
Solution Approach 1:
The LED die is attached to the substrate before the overmolding process, so the bonding process occurs at lower temperature without requiring high temperature melting. This preliminary attachment prevents the yellowing phenomenon and gap formation that would otherwise occur during high temperature processing, while still achieving effective thermal conductivity through the Au x Sn y alloy bonding layer.
Solution Approach 2:
The invention changes the processing temperature parameter by attaching the LED die before overmolding rather than requiring high temperature melting of the Au x Sn y alloy. This parameter change allows the bonding to occur at lower temperatures that do not cause yellowing of the barrier material or formation of gaps, while maintaining the high thermal conductivity benefit of the Au x Sn y alloy.
2Strength
If high temperature is applied to melt Au x Sn y material, then bonding is achieved, but barrier material turns yellow and gaps form
Solution Approach 1:
The LED die attachment is performed as a preliminary step before the overmolding process that would otherwise require high temperature. This allows the Au x Sn y alloy to bond the LED die to the substrate at lower temperatures, achieving sufficient bonding strength without exposing the barrier material to temperatures that cause yellowing and gap formation.
3Temperature
If silver paste is used to improve heat dissipation, then thermal conductivity is improved, but light output is significantly influenced
Solution Approach 1:
The invention uses Au x Sn y alloy specifically for the bonding layer between LED die and substrate where thermal conductivity is needed, while keeping other parts of the module (such as the barrier and optical paths) free of materials that would affect light output. The Au x Sn y alloy provides the required thermal management locally at the bonding interface without compromising the optical performance of the overall module.
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 enhances heat dissipation in LED modules with Au x Sn y bonding, maintaining light output and extending service life by preventing yellowing and gap formation, while allowing for efficient mass production of LED modules.
Implementation Method 1
the material of Au x Sn y is a good substitute... Au x Sn y usually has a relatively high thermal conductivity, e.g., for an alloy of Au 80 Sn 20, it has a thermal conductivity of about 58W/mK
Implementation Method 2
overmolding the patterned plate with the LED dies by a molding material for creating barriers bridging the first gaps
Data Source
Figure 1a~1f
Figure 1g~1j
Figure 1k~3
AI summary
The present invention generally relates to a method for manufacturing a plurality of LED modules. The method comprises: providing a plate (10); performing a patterning process to the plate (10) to obtain a patterned plate comprising a plurality of substrates (20) for the plurality of LED modules, the patterning process at least creating first gaps (G1) between the plurality of substrates (20); attaching LED dies (30) on the plurality of substrates (20); placing the patterned plate with the LED dies (30) into a mold; overmolding the patterned plate with the LED dies (30) by a molding material for creating barriers (40) bridging the first gaps (G1), the barriers (40) protruding from first surfaces of the substrates (20) where the LED dies (30) are attached, and singulating the plurality of substrates (20) with the LED dies (30) into the plurality of the LED modules by dicing at the first gaps (G1).