Mold Fixture for LED Die-to-Wafer Bonding Alignment
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Solution Overview
Problem
Conventional die-to-wafer bonding processes for LED devices suffer from significant die shifting, exceeding +/â38 microns, which affects the reliability and performance of smaller LED devices and limits the applicability of advanced packaging processes.
Innovation Solution
A mold fixture with concave recesses is used to restrict lateral displacement of LED devices during the bonding process, ensuring precise alignment and minimizing die shift to less than 10 microns by covering the devices and applying adjustable force through its weight or external mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional auto die-bonding machines with flux reflow oven or eutectic die-to-wafer bonders are used, then the bonding process can be completed, but the LED dies shift lateral positions exceeding +/â38 microns
Solution Approach 1:
The patent introduces a mold fixture as an intermediary device between the LED dies and the bonding process. This mold fixture includes positioning structures that physically constrain the LED dies during bonding, preventing lateral shifts. The mold fixture acts as a mediator that maintains precise alignment without requiring modifications to the LED dies or bonding pads themselves.
Solution Approach 2:
The patent implements preliminary positioning actions by pre-aligning LED dies within mold cavities before the bonding process begins. The mold fixture is designed with precise dimensional tolerances that establish correct positions in advance, eliminating the need for real-time alignment adjustments during bonding and preventing die shift throughout the process.
2Length of moving object
If LED die size continues to decrease, then device miniaturization is achieved, but die-shift becomes a bigger issue affecting reliability and performance
Solution Approach 1:
The patent divides the bonding process into separate functional components: the mold fixture handles positioning and alignment, while the bonding process handles material joining. This segmentation allows each component to be optimized independently - the mold fixture can provide high-precision positioning for small dies without being compromised by bonding process variations.
Solution Approach 2:
The mold fixture serves as an intermediary that decouples the alignment function from the bonding function. For miniaturized LED dies, this intermediary structure provides the necessary mechanical support and positioning that would be difficult to achieve through bonding process control alone, enabling reliable bonding of smaller devices.
3Manufacturing precision
If a mold fixture is used to restrict lateral displacement, then die shift is reduced to within 5 microns, but the device complexity increases
Solution Approach 1:
The mold fixture is designed to be self-aligning through its cavity dimensions and positioning features. Once placed on the substrate, the fixture automatically establishes correct positions for LED dies without requiring complex external alignment systems or multiple adjustment steps, reducing operational complexity despite adding a physical component.
Solution Approach 2:
The mold fixture serves multiple functions simultaneously: it provides mechanical support for LED dies, establishes precise positioning, prevents lateral displacement during bonding, and can be removed after bonding completes. This multi-functionality reduces the need for separate alignment tools and fixtures, offsetting the added complexity with consolidated functionality.
Data Source
AI summary
A plurality of conductive pads are disposed on a substrate. A plurality of semiconductor dies are each disposed on a respective one of the conductive pads. A mold device is positioned over the substrate. The mold device contains a plurality of recesses that are each configured to accommodate a respective one of the semiconductor dies underneath.