3D Electroform Stencil for LED Solder Deposition
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Solution Overview
Problem
Existing LED manufacturing methods face challenges in preventing solder bridging and ensuring precise deposition of high-melting-point solders like gold-tin, which is crucial for automotive applications where thermal conditions are extreme.
Innovation Solution
A 3D electroform stencil is used to deposit gold-tin solder patterns on metal pads within an LED package, utilizing apertures to prevent bridging and ensure precise solder distribution, allowing for efficient attachment of the LED die in constrained spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional stencil printing is used to deposit solder, then the process is simple, but solder bridging occurs and deposition precision is poor
Solution Approach 1:
The patent transitions from conventional 2D flat stencils to 3D electroform stencils with vertical walls and reservoirs. This dimensional change allows solder paste to be contained in reservoirs and released through controlled apertures, preventing bridging while maintaining deposition precision. The 3D structure enables the stencil to engage with sidewalls of the reflector cup, providing mechanical stability and precise positioning.
Solution Approach 2:
The stencil is divided into multiple reservoirs, each containing solder paste for specific pads. Each reservoir has its own apertures that align with corresponding metal pads. This segmentation allows independent control of solder deposition for each pad, preventing bridging between adjacent pads while maintaining simple manufacturing processes.
2Reliability
If high-melting-point solder like gold-tin is used for automotive applications, then thermal reliability is improved, but solder bridging becomes more difficult to prevent
Solution Approach 1:
The stencil design provides different local structures: vertical walls at the reservoir boundaries to contain solder paste and prevent bridging, and controlled apertures at the bottom surface for precise solder release. The lip structure engages with sidewalls to provide localized mechanical support. This local quality differentiation allows the use of high-melting-point solder while maintaining deposition precision.
3Manufacturing precision
If a 3D electroform stencil with reservoirs is used, then solder bridging is prevented and deposition precision is improved, but the device complexity increases
Solution Approach 1:
The 3D electroform stencil structure serves multiple functions simultaneously: the vertical walls and lip engage with sidewalls for self-positioning and mechanical support, the reservoirs automatically contain solder paste, and the apertures provide self-aligned solder release paths. This self-service capability reduces the need for additional positioning mechanisms and complex control systems, offsetting the increased 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 method effectively prevents solder bridging and ensures reliable electrical connections, enabling LED packages to operate under high thermal conditions, such as those found in automotive headlights, while maintaining precision and reliability.
Implementation Method 1
performing reservoir stencil printing to deposit a respective solder pattern on each of the metal pads
Implementation Method 2
performing reflow soldering to attach the LED die to the metal pads
Data Source
Figure 1A~1B
Figure 2A~3B
Figure 4
AI summary
A method for manufacturing light emitting devices, comprising: providing a package body including: (i) a reflector cup defining a cavity and (ii) a plurality of metal pads disposed at a bottom surface of the cavity; performing reservoir stencil printing to deposit a respective solder pattern on each of the metal pads, the reservoir stencil printing being performed using a 3D electroform stencil that is placed over the reflector cup, the 3D electroform stencil including a lip configured to engage one or more sidewalls of the reflector cup, and a reservoir extending away from the lip and into the cavity; placing an LED die on the solder patterns that are formed on the metal pads and performing reflow soldering to attach the LED die to the metal pads.