Electroless Plating for LED Bond Pads
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Solution Overview
Problem
Conventional methods for forming bond pads in light-emitting diodes using metal deposition result in excessive material coverage and inefficient recycling, with only 50% to 70% of the deposited metal being reusable due to the omni-directional nature of deposition processes like CVD or PVD.
Innovation Solution
The method employs electroless plating without external voltage, using a seed layer and insulating layers to control metal ion deposition, reducing metal usage by two-thirds and ensuring uniform thickness by managing the attraction and repulsion of metal ions by semiconductor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal deposition is used to form bond pads, then bond pads can be formed with sufficient thickness to bear wire-bonding impact, but excessive material coverage occurs and recycling efficiency is low
Solution Approach 1:
The patent applies local quality by creating different surface properties in different areas. The bond pad area is treated with a catalyst layer that promotes metal deposition, while the spinner area is kept free of catalyst. This ensures metal is deposited only where needed (bond pads) rather than uniformly across the entire spinner surface, reducing material waste while maintaining sufficient bond pad thickness.
Solution Approach 2:
The patent extracts the harmful omni-directional deposition characteristic from the metal deposition process. By introducing a catalyst layer that selectively binds metal ions only at the bond pad locations, the unwanted radial deposition across the spinner is eliminated. This allows precise control of metal placement, reducing waste material while ensuring adequate bond pad formation.
2Ease of manufacture
If metal deposition is used to form bond pads, then bond pads can be formed, but material covering 80%-90% of chip area is redundant and needs removal
Solution Approach 1:
The catalyst layer is applied selectively to the bond pad areas, creating local zones with enhanced metal deposition properties. This ensures metal is deposited only at the required bond pad locations rather than uniformly across the entire chip area, eliminating the need to remove redundant material from 80-90% of the chip surface.
Solution Approach 2:
The catalyst layer on the bond pad areas acts as a self-selecting mechanism that automatically attracts and binds metal ions from the electrolyte. This self-service property eliminates the need for subsequent removal processes, as metal is deposited only where the catalyst is present, directly forming bond pads without creating redundant material elsewhere.
3Loss of substance
If electroless plating is used, then metal usage is reduced by two-thirds, but control of metal ion deposition requires managing attraction and repulsion by semiconductor layers
Solution Approach 1:
The catalyst layer serves as an intermediary between the semiconductor substrate and the metal ions in the electrolyte. It mediates the deposition process by providing specific binding sites that attract metal ions, while the insulating layer acts as a mediator to prevent unwanted attraction of metal ions by the semiconductor layers. This intermediary approach enables electroless plating with reduced metal usage while controlling deposition patterns.
Solution Approach 2:
The patent changes the chemical parameters of the deposition system by introducing a catalyst layer with specific chemical properties that promote metal ion reduction. By modifying the chemical environment at the bond pad locations (through catalyst presence) versus the spinner area (no catalyst), the deposition behavior is controlled without requiring external voltage, achieving electroless plating with reduced metal consumption.
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 significantly reduces the amount of plating metal required and achieves uniform bond pad thickness by optimizing metal ion deposition, enhancing recycling efficiency and reducing material waste.
Implementation Method 1
immersing at least part of the pre-covering layer into an electrolyte having metal ions which tend to reduce and deposit on the pre-covering layer under no bias voltage
Implementation Method 2
a surface impurity concentration of the p-type semiconductor layer and the n-type semiconductor layer distributes unevenly on the area
Data Source
AI summary
One embodiment of the invention relates to a method of manufacturing a light emitting diode. The method includes forming an insulating layer on an area, not covered by a seed layer, of at least one of a p-type semiconductor layer and an n-type semiconductor layer, wherein the impurity concentration varies on the surface of the area; and immersing at least part of the seed layer into an electrolyte having metal ions which tend to reduce and deposit on the seed layer under no bias voltage.