Temporary Test Pads for Wafer-Level MicroLED Pixel Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to electrically test microLED pixels without increasing the pixel size and/or damaging the pixel, as existing methods either skip testing at the wafer level or risk damaging the permanent contacts.
Innovation Solution
The solution involves creating micro-light emitting diode (uLED) devices with temporary, removable electrical test pads that allow for the measurement of absolute electrical properties without altering the pixel size or damaging it, and a testing apparatus that includes N-contact and P-contact test pad templates connected to testing buses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent test pads are integrated into microLED pixels, then electrical testing can be performed, but the pixel size increases and manufacturing complexity increases
Solution Approach 1:
The patent separates the test pad structure from the permanent contact structure by introducing a release layer that allows temporary test pads to be attached to the permanent contacts during testing, then removed afterward. This segmentation enables testing functionality without permanently increasing pixel area.
Solution Approach 2:
The release layer acts as an intermediary between the permanent contacts and temporary test pads, enabling the test pads to be attached and removed without damaging the permanent contacts or altering the pixel structure permanently.
2Productivity
If testing is performed at wafer level, then productivity increases, but risk of damaging pixels and contacts increases
Solution Approach 1:
The patent applies a release layer to the wafer before testing, creating a protective intermediary structure that enables safe wafer-level testing. This preliminary action allows multiple pixels to be tested simultaneously without the risk of damaging contacts, as the release layer facilitates controlled attachment and removal of test pads.
Solution Approach 2:
The release layer serves as a mediator that protects the permanent contacts during the testing process, allowing electrical contact to be made and removed without direct mechanical stress on the fragile pixel contacts, thereby enabling safe wafer-level testing.
3Area of moving object
If temporary test pads are used, then pixel size is maintained and damage risk is reduced, but device complexity increases
Solution Approach 1:
The patent extracts the test pad functionality from the permanent contact structure by using temporary test pads that can be attached and removed. This separation maintains the simplicity of the pixel design while adding testing capability through an external, removable component.
Solution Approach 2:
The temporary test pads are designed as disposable or reusable components that can be attached and removed multiple times. They serve their testing purpose and can be discarded or replaced without affecting the permanent contact structure, reducing the need for complex, durable integrated test pads.
Data Source
AI summary
Micro-light emitting diode (uLED) devices comprise: a plurality of micro-light emitting diodes (uLEDs), each of the uLEDs comprising: a pixel; an N-contact in contact with the pixel and having an N-contact top surface; a P-contact in contact with the pixel and having a P-contact top surface; an N-contact test pad on the N-contact top surface and having an N-contact test pad surface; and a P-contact test pad on the P-contact top surface and having a P-contact test pad surface; and a primary release layer positioned between all of the N-contacts and P-contacts of the uLEDs. Test apparatus and methods of making and testing the same are also provided.