Anodized Aluminum PCB Substrate Stiffness and Moisture Resistance
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Solution Overview
Problem
Conventional printed circuit board (PCB) manufacturing methods are complex and costly due to the need for gold-plating lead wires, and they suffer from high moisture absorption and thermal expansion issues, making them unreliable and difficult to handle during assembly.
Innovation Solution
A method involving primary and secondary anodizing processes to electroplate bonding fingers with gold without lead wires and form insulating oxide layers, which also stiffens the substrate, eliminating the need for additional plates and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solder resist is used to prevent oxidation and provide electrical insulation, then the circuit pattern is protected, but the PCB has high moisture absorption rate and high coefficient of thermal expansion leading to low reliability
Solution Approach 1:
The patent changes the material parameter from conventional solder resist to anodized oxide layer. The oxide layer is formed through electrochemical oxidation of aluminum, creating a ceramic-like structure with fundamentally different physical properties: extremely low moisture absorption, low thermal expansion coefficient, and high thermal stability. This parameter change in material composition directly resolves the reliability issue.
Solution Approach 2:
The patent creates a composite structure by forming an aluminum oxide layer on the aluminum substrate. This composite material combines the advantages of aluminum (conductivity, flexibility) with aluminum oxide (insulation, moisture resistance, thermal stability), achieving both electrical insulation and protection against harmful environmental factors simultaneously.
2Ease of manufacture
If gold electroplating is performed using conventional lead wire method, then bonding finger can be electroplated with gold, but the manufacturing process becomes complicated and costly
Solution Approach 1:
The patent extracts and eliminates the lead wire component from the electroplating process. Instead of using lead wires to conduct electricity to the bonding finger, the aluminum substrate itself serves as the conductive path. This removal of the lead wire simplifies the manufacturing process and reduces costs while maintaining the electroplating function.
Solution Approach 2:
The aluminum substrate serves multiple functions simultaneously: it acts as the structural base, the electrical conductor for electroplating, and the material source for the protective oxide layer. This multi-functionality eliminates the need for separate lead wire components and simplifies the overall manufacturing process.
3Length of stationary object
If substrate thickness is reduced for small-sized electronic appliances, then the appliance size is reduced, but the substrate becomes too flexible requiring additional stiffened plates that complicate handling
Solution Approach 1:
The patent creates a composite structure where the aluminum substrate is combined with an aluminum oxide layer. This composite provides enhanced mechanical strength and stiffness-to-weight ratio, allowing thin substrates to maintain sufficient rigidity for handling without requiring additional stiffened plates.
Solution Approach 2:
The patent changes the mechanical properties of the substrate surface through anodization. The oxide layer formation alters the surface structure and increases the overall structural rigidity of the thin substrate, enabling it to maintain dimensional stability and ease of handling despite reduced thickness.
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 method simplifies the gold electroplating process, reduces moisture absorption and thermal expansion, and improves handling and reliability of PCBs by forming oxide layers that protect circuit patterns and insulate circuits effectively.
Implementation Method 1
forming a first insulating layer on the metal layer by primarily anodizing the metal layer
Implementation Method 2
electroplating a surface of the bonding finger by supplying power to the metal layer
Data Source
AI summary
A printed circuit board (PCB) and appertaining method of manufacturing are provided. The method includes: coating a metal layer on the entire surface of a substrate having an outer surface on which an interconnection pattern is formed; partially removing the metal layer from the surface of the substrate to form a window for a chip to be mounted therein and partially exposing the interconnection pattern to form a bonding finger; forming a first insulating layer on the metal layer by primarily anodizing the metal layer; electroplating a surface of the bonding finger by supplying power to the metal layer; and forming a second insulating layer disposed below the first insulating layer by entirely and secondarily anodizing the metal layer. A gold electroplating process can be performed without a lead wire, and an oxide layer formed by an anodizing process can protect circuits formed on the substrate and electrically insulate them.