LED Array on LTCC Substrate with Thermal Vias for AC Operation
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Solution Overview
Problem
Existing AC light emitting devices face limitations in high packing density and production costs due to single LED failures and the need for expensive power supplies and driver circuitry when operated from high voltage AC sources.
Innovation Solution
A light emitting device comprising a plurality of LEDs mounted within recesses of an insulating substrate with a pattern of electrical conductors for connection, incorporating thermal vias for heat management and a phosphor material for wavelength conversion, allowing for high packing density and operation directly from AC supplies without additional rectification components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-chip integrated LED with series-connected individual LEDs is used for direct AC operation, then the device can be operated from high voltage AC supply without expensive power supplies, but the payload is only 50% since only one LED string is energized at a time
Solution Approach 1:
The LED array is divided into multiple independent strings, each capable of being energized during different half-cycles of the AC supply. This segmentation allows different portions of the LED array to be utilized alternately, increasing overall payload from 50% to potentially 100% or more depending on configuration.
Solution Approach 2:
The patent utilizes the periodic nature of AC power supply to alternately energize different LED strings during positive and negative half-cycles. By configuring multiple strings with appropriate polarity arrangements, the system achieves continuous operation with higher payload utilization across the entire AC cycle.
2Volume of moving object
If individual LEDs are spaced at 20μm separation on the LED wafer, then the fabrication is compact, but the packing density is limited
Solution Approach 1:
The patent transitions from two-dimensional planar spacing to three-dimensional stacked configurations, placing LED chips at different vertical levels. This dimensional change allows significantly higher packing density without increasing lateral footprint, effectively resolving the contradiction between compactness and quantity.
Solution Approach 2:
Multiple LED strings are nested within a single package structure, with multiple chips per string and multiple strings per package. This nesting approach maximizes the quantity of LEDs within a compact volume by utilizing vertical space and hierarchical organization.
3Quantity of substance
If multiple LEDs are interconnected on a single wafer, then packing density increases, but a single LED failure can affect the entire string
Solution Approach 1:
The LED array is segmented into multiple independent strings with separate electrical pathways. This segmentation ensures that a failure in one LED or one string does not propagate to other strings, maintaining system reliability while achieving high packing density through multiple parallel configurations.
Solution Approach 2:
Different regions of the substrate are allocated to different functional strings with independent electrical connections. This local quality approach allows selective operation and failure isolation, where each local region (string) can be independently managed, maintaining overall system reliability despite high density integration.
4Reliability
If expensive power supplies and driver circuitry are used for high voltage AC operation, then reliable operation is achieved, but production costs increase
Solution Approach 1:
The LED array configuration itself provides the rectification function through its opposing parallel string arrangement, eliminating the need for external rectifier circuits. The LEDs self-regulate their operation based on AC cycle polarity, achieving reliable AC operation without expensive driver circuitry or power supply components.
Solution Approach 2:
The LED string configuration serves multiple functions simultaneously: it acts as both the light-emitting element and the rectification mechanism. This multi-functionality eliminates the need for separate power conversion components, reducing production costs while maintaining reliable operation from AC supplies.
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 solution achieves a high packing density of LEDs per unit area, reduces production costs by allowing for efficient use of substrates, and enables continuous operation from AC sources with improved thermal management and color consistency.
Implementation Method 1
white LEDs include one or more phosphor materials, that is photo-luminescent materials, which absorb a portion of the radiation emitted by the LED and re-emit radiation of a different color (wavelength)
Implementation Method 2
incorporating thermal vias for heat management
Data Source
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AI summary
A light emitting device comprises: a plurality of light emitting diodes and an insulating (low temperature co-fired ceramic) substrate with an array of recesses each for housing a respective one of the light emitting diodes. The substrate incorporates a pattern of electrical conductors that is configured for connecting the light emitting diodes in a selected electrical configuration and to provide at least two electrical connections on the floor of each recess. Light emitting diodes can be electrically connected to the electrical connections by at least one bond wire or by flip chip bonding. Each recess is filled with a transparent material to encapsulate each light emitting diode. The transparent material can incorporate at least one phosphor material such that the device emits light of a selected color and/or color temperature.