LED Flip-Chip Package Asymmetric Electrode Thermal Stress
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Solution Overview
Problem
LED packages face thermal stress due to heat generation during operation, which can lead to mechanical stress on electrodes and pads, affecting the reliability and performance of the device.
Innovation Solution
A light-emitting diode (LED) package with a flip-chip bonding structure that includes a package substrate, electrode pads, and insulating layers to reduce thermal stress, where the upper insulating layer is strategically positioned between the first and second electrode pads, and the second electrode extends perpendicular to the upper insulating layer, minimizing thermal expansion forces on the LED chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LED package structure is used, then the LED chip can be packaged and used, but thermal stress is exerted on the electrode or pad due to heat generation and thermal expansion
Solution Approach 1:
The second electrode pad is designed with an asymmetric structure featuring a protruding portion that extends into the groove of the first electrode pad. This asymmetric configuration allows the second electrode pad to bear thermal expansion forces more effectively, directing the forces away from the LED chip and reducing thermal stress on critical components
Solution Approach 2:
The electrode pad structure transitions from a conventional planar configuration to a three-dimensional structure with grooves and protruding portions. This dimensional change enables the electrode pads to interlock and better withstand thermal expansion forces in multiple directions, improving thermal stress resistance
2Reliability
If the upper insulating layer is positioned between the first and second electrode pads, then thermal stress on the LED chip is reduced, but the structural complexity increases
Solution Approach 1:
The upper insulating layer serves multiple functions: it provides electrical insulation between the first and second electrode pads, mechanically supports the asymmetric electrode pad structure, and helps direct thermal expansion forces away from the LED chip. This multi-functionality reduces the need for additional components, offsetting the increased structural complexity
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 effectively reduces thermal stress on the LED chip by directing thermal expansion forces away from critical components, enhancing the package's reliability and workability while maintaining excellent electrical connectivity.
Implementation Method 1
an upper insulating layer for insulating the first electrode pad from the second electrode pad on the package substrate
Implementation Method 2
When the LED chip in the LED package is operated, heat is generated
Implementation Method 3
each element is thermally expanded. Accordingly, a thermal stress is exerted on an electrode or a pad in the LED chip
Implementation Method 4
an LED chip including a first electrode and a second electrode which are respectively electrically connected in the form of a flip-chip to the first electrode pad and the protruding portion of the second electrode pad
Data Source
AI summary
A light-emitting diode (LED) package includes a package substrate, a first electrode pad, a second electrode pad, an upper insulating layer and an LED chip. The first electrode pad is disposed on an upper surface of the package substrate and includes a groove. The second electrode pad includes a protruding portion disposed in the groove of the first electrode pad. The upper insulating layer insulates the first electrode pad from the second electrode pad on the package substrate. The LED chip includes a first electrode and a second electrode which are respectively electrically connected in the form of a flip-chip to the first electrode pad and the protruding portion of the second electrode pad.