Semiconductor Emitter Matrix Layout for Sparse Wirebond IR Arrays
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Solution Overview
Problem
Existing semiconductor light-emitting devices, particularly infrared (IR) LED arrays, face challenges with wirebonding due to the need for space to accommodate wirebonds, which limits the compactness and efficiency of the light source, and results in reduced power efficiency and increased thermal issues.
Innovation Solution
The solution involves creating a semiconductor light-emitting device with an emitter matrix that includes an arrangement of emitter cells interspersed with non-emitter cells, allowing for a sparse distribution of wirebonds. This design reduces the length and number of wirebonds, minimizing light obstruction and improving thermal dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wirebonds are used to connect infrared LEDs in an array, then electrical connection is achieved, but the wirebonds occupy space in the light path and require sufficient headroom which limits compactness
Solution Approach 1:
The patent transitions from planar wirebond connections to three-dimensional vertical cavity surface emitting laser structures, where light emerges perpendicular to the chip surface. This dimensional change allows elimination of wirebonds from the light path while maintaining electrical connectivity through the chip substrate, resolving the contradiction between reliable connection and compactness.
Solution Approach 2:
The patent extracts and removes the wirebond component entirely from the system by using flip-chip mounting with direct substrate connections. The electrical connection function is achieved through the chip substrate itself rather than external wirebonds, eliminating the space-occupying element while preserving the essential electrical connectivity.
2Reliability
If wirebonds are used in large IR-LED arrays, then electrical connection is achieved, but wirebonds to the center are significantly longer which limits the highest achievable switching frequency
Solution Approach 1:
The patent uses vertical cavity surface emitting laser structures with flip-chip mounting, where electrical connections are made through the chip substrate in three dimensions. This eliminates the radial wirebond pattern with varying lengths and replaces it with uniform, short vertical and lateral connections through the substrate, enabling high switching frequencies across all array positions.
Solution Approach 2:
The patent inverts the traditional mounting approach by using flip-chip technology where the chip is mounted upside down with direct contact to the substrate. This inversion places the electrical connection points at the bottom of the chip rather than requiring wirebonds from the top, dramatically reducing connection lengths and enabling high-speed operation.
3Speed
If flip-chip technology is used for IR-LED arrays, then compactness and switching frequency are improved, but output power is reduced by about half
Solution Approach 1:
The patent segments the infrared light emission into two wavelength components and uses separate optimized LED structures for each segment. One set of LEDs is optimized for 850nm emission while another set targets 940nm emission, allowing each segment to operate at peak efficiency and collectively achieve high output power while maintaining compact flip-chip architecture.
Solution Approach 2:
The patent employs composite LED structures with multiple active regions and specialized semiconductor materials optimized for different infrared wavelengths. By combining materials and structures tuned for 850nm and 940nm emission, the system achieves high efficiency in both wavelength bands, compensating for any individual structure limitations and maintaining high overall output power.
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 results in a more compact, efficient, and thermally improved semiconductor light-emitting device, with reduced power consumption and increased light output compared to traditional IR-LED arrays.
Implementation Method 1
A semiconductor emitter is provided in each emitter cell. The semiconductor emitter is manufactured to achieve a luminous intensity of 5-100 Mcd/m2
Data Source
AI summary
A semiconductor light-emitting device has an emitter matrix with an arrangement of emitter cells interspersed with non-emitter cells. The emitter cell has a semiconductor emitter, and a non-emitter cell does not have a semiconductor emitter. A number of bond pads for connection to a power supply and a plurality of wirebonds are present. Each wirebond extends from a bond pad to the semiconductor emitter of an emitter cell. An imaging arrangement includes a light source for illuminating a scene. The light source has a pair of such semiconductor light-emitting devices. A method of manufacturing such a semiconductor light-emitting device is also described.