Flip Chip LED With Insulating Substrate To Prevent Short Circuits
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Solution Overview
Problem
Conventional LED packaging methods face issues such as misalignment, lower illumination efficiency, and increased manufacturing costs due to light blocking, as well as the risk of reverse current and short circuits caused by the close proximity of semiconductor layers to the substrate during eutectic bonding or reflow in flip chip type LEDs.
Innovation Solution
The use of a silicon substrate or electrically insulating substrate with a transparent substrate and semiconductor layers, featuring metallic conductive plugs and electrodes, which are bonded using the flip chip method to avoid short circuits and enhance illumination, with an optional Zener diode structure to manage high electric currents, and an insulating layer to prevent electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional eutectic bonding or reflow is used to electrically couple flip chip type LED to substrate, then electrical connection is achieved, but reverse current and short circuit occur due to close proximity between semiconductor layers and substrate electrodes
Solution Approach 1:
The patent introduces an electrically insulating substrate as an intermediary between the LED chip and the mounting substrate. This insulating substrate acts as a mediator that provides electrical isolation, preventing reverse current and short circuits while still allowing thermal and mechanical coupling. The insulating substrate with through-holes and conductive plugs creates a safe electrical pathway that eliminates the harmful electrical interaction between the LED semiconductor layers and substrate electrodes.
Solution Approach 2:
The patent segments the electrical coupling function into multiple independent components: the LED chip, the insulating substrate, and the mounting substrate. By dividing the electrical connection path and introducing the insulating substrate as a separate functional layer, the patent isolates the semiconductor layers from direct contact with substrate electrodes, thereby preventing short circuits while maintaining electrical connectivity through controlled conductive pathways.
2Reliability
If gold balls are used for electrical coupling in conventional LED packaging, then electrical connection is achieved, but misalignment occurs when bonding LED chips to substrate
Solution Approach 1:
The patent applies preliminary action by pre-forming conductive plugs within the insulating substrate before mounting the LED chip. These conductive plugs are positioned in advance at precise locations, and the LED chip is then bonded to align with these pre-positioned plugs. This preliminary placement of conductive pathways eliminates the alignment issues associated with conventional gold ball bonding, as the conductive connections are already established in the insulating substrate prior to chip mounting.
3Illumination intensity
If underfill is coated between LED chips and substrate to enhance reflectivity, then illumination is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies the self-service principle by designing the insulating substrate itself to provide the reflective function. The insulating substrate is configured with a reflective surface or reflective coating on its bottom side, which serves dual purposes: providing electrical insulation and enhancing light reflection. This eliminates the need for a separate underfill material, as the insulating substrate performs both the electrical isolation function and the optical reflection function, thereby reducing manufacturing cost while maintaining or improving illumination efficiency.
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 improves the alignment and illumination efficiency of LEDs, reduces manufacturing costs, and prevents short circuits and breakdowns due to high currents, resulting in a more reliable and efficient LED packaging solution.
Implementation Method 1
a plurality of first metallic conductive plugs traversing from a bottom surface of the silicon substrate to an N-type semiconductor layer, a plurality of second metallic conductive plugs traversing from the bottom surface of the silicon substrate to the P-type semiconductor layer
Implementation Method 2
uses eutectic bonding to electrically couple flip chip type LED chips with corresponding electrodes of the substrate
Implementation Method 3
by either eutectic bonding or reflow, the flip chip type LED is electrically coupled to electrodes on a substrate
Data Source
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AI summary
The present disclosure provides a flip chip type light emitting diode which comprises a substrate (20) and a light emitting diode chip (10). The substrate comprises a body (43), a plurality of third pads (23), a fourth pad (24), a first electrode (25), a second electrode (26), a plurality of first vias (21), and a second via (22). The body (43) has a first surface (20a) and a second surface (20b) opposite to the first surface. The third pads (23) and the fourth pad (24) are disposed on the first surface (20a) of the body (43). The first electrode (25)and the second electrode (26) are disposed on the second surface (20b) of the body (43). The first vias (21) traverse through the body (43) and are each electrically coupled to a respective one of the third pads (23) and the first electrode (25). The second via (22) traverses through the body (43) and is electrically coupled to the fourth pad (24) and the second electrode (26).