Flip-Chip LED Package with HTCC Substrate for Low Etendue
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Solution Overview
Problem
Existing LED-based lighting devices are not optimal for theater lighting and other contexts requiring low etendue, as they often require a large number of LEDs to produce bright light, limiting the density of LEDs due to thermal and electrical performance constraints, which increases the light source area and etendue.
Innovation Solution
The use of flip-chip LEDs with all electrical contacts on the bottom surface eliminates the need for space between adjacent LEDs, allowing for closer spacing and independent current control of LEDs, combined with a multilayer HTCC substrate for thermal management and electrical connectivity, enabling reduced etendue and increased brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional wire-bonded LEDs are used with bonding pads on top and bottom surfaces, then electrical connectivity is achieved, but space must be left between adjacent LEDs to accommodate bonding pads, increasing the light source area and etendue
Solution Approach 1:
The patent inverts the conventional LED mounting approach by using flip-chip LEDs where all electrical contacts are disposed on the bottom surface opposite the light-emitting surface, rather than having bonding pads on top and bottom surfaces. This inversion eliminates the need for space between adjacent LEDs to accommodate bonding pads, allowing LEDs to be positioned closer together and reducing the overall light source area and etendue
Solution Approach 2:
The patent moves electrical contacts from the top surface to the bottom surface of the LED chip, utilizing the third dimension (vertical orientation) to resolve the spatial conflict between bonding pads and adjacent LEDs. This dimensional reorganization allows for closer LED spacing while maintaining electrical connectivity
2Area of stationary object
If LED density is increased to reduce light source area and etendue, then brightness control is improved, but thermal and electrical performance constraints are exceeded
Solution Approach 1:
The patent introduces a substrate with integrated heat sinking capabilities as an intermediary between the high-density LED array and the ambient environment. This substrate serves as a thermal management system that can dissipate the heat generated by closely spaced high-current LEDs, enabling increased LED density without exceeding thermal performance constraints
Solution Approach 2:
The substrate serves multiple functions simultaneously: it provides mechanical support for the LEDs, establishes electrical connectivity through conductive paths, and manages thermal dissipation through heat sinking capabilities. This multi-functionality allows the system to accommodate high LED density while maintaining both electrical and thermal performance
3Adaptability or versatility
If independent current control to different LEDs is implemented for color control, then lighting customization is improved, but separate current paths require more space and complexity
Solution Approach 1:
The patent segments the electrical connectivity structure into separate conductive paths on the substrate, with each path independently routing current to specific LEDs or groups of LEDs. This segmentation enables independent current control to different LEDs for color customization while organizing the electrical structure in a systematic manner that minimizes space requirements
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 configuration reduces the spacing between LEDs, decreases the non-luminous surface area, and allows for more efficient heat transfer, resulting in brighter light with lower etendue, enhancing control over lighting effects in theater and similar applications.
Implementation Method 1
The paths can be arranged such that current can be supplied independently to different subsets, or groups, of the LEDs
Implementation Method 2
An LED (or 'LED chip'), as used herein, refers to a light-emitting diode, i.e., a semiconductor device that emits light in response to electrical current
Implementation Method 3
In some cases, some or all of the light-emitting surface of the LED may be coated with a wavelength-shifting material (e.g., phosphor) that shifts some of the light emitted by the LED to a longer wavelength
Data Source
AI summary
An emitter for an LED-based lighting device can incorporate “flip-chip” LEDs, in which all electrical contacts are disposed on the bottom surface of the chip. The emitter base can be a multilayer high-temperature cofired ceramic (HTCC) substrate, with metal traces formed between the layers and vias through the layers to join traces in different layers, thereby providing electrical connectivity to each LED. The paths can be arranged such that current can be supplied independently to different subsets of the LEDs. The top layer of the emitter base is fabricated with exposed vias at the top surface. Metal pads are then printed onto the exposed vias on the top surface, and flip-chip LEDs are bonded to the metal pads, e.g., using solder.