Self-Scanning Light Emitting Thyristor Array Bonding Pad Reduction
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Solution Overview
Problem
The production of high-resolution light emitting element arrays for printers is limited by the large area of bonding pads and the resulting increase in chip size and cost, due to the need for numerous wire bonds in current LED-based systems.
Innovation Solution
A self-scanning light emitting element array using light-emitting thyristors with a pnpn structure, where the light-emitting-unit thyristors are sequentially triggered by a rectangular voltage applied to a single bonding pad, eliminating the need for individual bonding pads and reducing the number of wire bonds, and incorporating a current confinement structure to enhance light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LED-based light emitting element arrays are used, then light emission function is achieved, but chip area increases due to large bonding pads and numerous wire bonds
Solution Approach 1:
Multiple light-emitting elements share common bonding pads through the self-scanning mechanism. Instead of requiring individual bonding pads for each LED, the invention uses a single bonding pad that sequentially activates different elements, merging the electrical connection function across multiple components and dramatically reducing the total number of bonding pads and wire bonds required
Solution Approach 2:
The light-emitting thyristor structure enables self-scanning operation where the array automatically sequences through its elements using internal feedback mechanisms. The system serves itself by using the light emission and detection feedback to trigger sequential activation without requiring external control circuits for each individual element, thereby eliminating the need for numerous individual bonding pads
2Ease of operation
If numerous wire bonds are used for each light emitting element, then individual element control is achieved, but production cost increases
Solution Approach 1:
The invention merges the control function for multiple individual elements into a single bonding pad through the self-scanning mechanism. The sequential activation is achieved by combining the electrical connection and control functions, allowing individual element control to be maintained while using far fewer wire bonds, thereby reducing manufacturing complexity and cost
3Loss of energy
If current confinement structure is added to light-emitting thyristor, then light emission efficiency is improved, but device structure becomes more complex
Solution Approach 1:
The current confinement structure is implemented as a localized feature within the thyristor device, specifically positioning high-resistance regions and conductive regions in specific areas to confine carriers where needed. This local modification improves light emission efficiency by directing current flow through the light-emitting region while keeping the rest of the device structure relatively simple and compatible with existing fabrication processes
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 the chip area and production costs by eliminating unnecessary bonding pads and wire bonds while maintaining high light emission efficiency and output power.
Implementation Method 1
a driving current is applied to a gate to cause a current to flow between an anode and cathode to emit light
Implementation Method 2
The current confinement structure includes a high-resistance region and a conductive region, and confines carriers in the conductive region
Data Source
AI summary
A light emitting element includes a semiconductor substrate, and an island structure formed on the semiconductor substrate. The island structure includes a light-emitting-unit thyristor and a current confinement structure. The light-emitting-unit thyristor includes stacked semiconductor layers having a pnpn structure. The current confinement structure includes a high-resistance region and a conductive region, and confines carriers in the conductive region.