LED Assembly Liquid Transfer Molding Wafer-Level Dam Formation
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Solution Overview
Problem
The typical LED assembling process is costly, inefficient, and has low yield due to the need for repeated steps on small silicon panels, resulting in slow throughput and low placement accuracy.
Innovation Solution
The method involves using liquid transfer molding to form multiple phosphor holding dam structures on a whole silicon wafer, allowing for concurrent formation of dams and domes, which replaces the single dam attachment and single dome dispensing steps, enabling better adhesion and precision in LED assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single dam attachment and single dome dispensing steps are used on each silicon chip, then the LED assembling process can be performed on singulated chips, but the manufacturing cost is high, throughput is slow, and placement accuracy is low
Solution Approach 1:
The patent combines multiple dam formation operations and multiple dome dispensing operations into single batch operations. The liquid transfer mold simultaneously forms dams for multiple LED chips in one step, and subsequently dispenses domes for all chips in another single step, replacing the traditional sequential single-chip processing approach
Solution Approach 2:
The liquid transfer mold serves multiple functions: it acts as a dam formation tool, a positioning fixture, and a dome dispensing template. This single device handles what traditionally required multiple separate machines and process steps, reducing overall process complexity while increasing throughput
2Reliability
If repeated single-chip assembling steps are performed on every singulated chip, then each chip can be individually processed, but the manufacturing cost increases and yield decreases
Solution Approach 1:
The patent processes entire silicon wafers containing multiple chips simultaneously through dam formation, wire bonding, and dome dispensing operations. This batch processing approach reduces the number of handling steps and inspection points compared to individual chip processing, thereby improving yield while reducing per-unit manufacturing cost
Solution Approach 2:
The liquid transfer mold is pre-configured with the exact dam geometry and positioning information before the process begins. This preliminary preparation ensures that all subsequent operations (dam formation, phosphor dispensing, dome placement) are performed with high precision in a single pass, eliminating the need for repeated adjustments and rework on each chip
3Manufacturing precision
If single dam attachment step is used on each chip, then the process can be simple, but placement accuracy is low and more inspection steps are needed
Solution Approach 1:
The liquid transfer mold contains a precise replica (copy) of the desired dam structure in its cavity. This mold copy is transferred onto each chip location with high fidelity, ensuring consistent and accurate dam placement across all chips without requiring complex active control or inspection systems
Solution Approach 2:
The mold is designed with segmented cavities that correspond to individual chip locations on the silicon wafer. Each cavity is independently formed but part of a unified mold structure, allowing precise positioning of dams on each chip while maintaining the simplicity of a single batch operation
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 manufacturing costs, increases productivity, and improves yield by enhancing placement accuracy and eliminating unnecessary steps, with a four-fold increase in production rate and precision within ±10 micrometers compared to traditional methods.
Implementation Method 1
a liquid transfer mold is used to form dams on the whole silicon wafer by pressing the top and bottom molds against each other
Implementation Method 2
forming multiple phosphor holding dam structures on a whole silicon wafer using a liquid transfer mold
Implementation Method 3
adding phosphor to an area enclosed by the multiple phosphor holding dam structures; curing the phosphor
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A method of and a system for making LED comprising concurrently forming multiple dam structures on a whole silicon wafer using a liquid transfer mold, attaching dies to the silicon wafer inside each of the dam structure, performing flux reflow, cleaning flux, performing wire bonding, dispensing phosphor, curing the phosphor, concurrently forming dome structures by using a liquid transfer mold on all of the dam structures, mounting wafer, and using a saw for single or multiple LED(s) singulation.