Electroplated Conductive Structure for Fine Pitch Circuit Boards
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Solution Overview
Problem
The existing methods for forming solder bumps on circuit boards face challenges in achieving uniform height control, leading to bridging issues and failure in providing fine pitch electrical conduction, while also being environmentally harmful due to excessive solder material usage.
Innovation Solution
A method involving the formation of a circuit board with insulating protection layers, metal adhesive layers, and conductive layers, followed by electroplating to create metal posts and conductive structures, allowing for precise control of solder bump formation and avoiding bridging through accurate material deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stencil printing technology is used to form solder bumps, then the process is simple and fast, but the height control becomes difficult and bridging phenomenon occurs
Solution Approach 1:
The patent replaces the mechanical stencil printing process with an electroplating process. Instead of physically printing solder material through a stencil, the invention uses electrochemical deposition to form metal bumps through electroplating, eliminating the height control issues and bridging problems associated with mechanical printing methods
Solution Approach 2:
The patent changes the fundamental process parameter from mechanical deposition to electrochemical deposition. By controlling electroplating parameters such as current density, plating time, and electrolyte composition, precise control over bump height and uniformity is achieved, resolving the height control difficulty of stencil printing
2Reliability
If more solder material is used to ensure coverage, then the electrical conduction is improved, but the bridging phenomenon and short problems increase
Solution Approach 1:
The patent applies local quality by using a resist layer with precisely patterned openings to control where solder material is deposited. Each opening is isolated from its neighbors, ensuring that solder material is deposited only in specific locations with exact dimensions, preventing bridging while ensuring adequate coverage for electrical conduction
Solution Approach 2:
The electroplating process inherently provides better material distribution control compared to stencil printing. The electrochemical deposition naturally fills the openings uniformly without the material flow and merging issues that cause bridging in mechanical printing, achieving reliable conduction without harmful side effects
3Ease of manufacture
If stencil printing is used for bump formation, then the process is straightforward, but fine pitch electrical conduction cannot be provided
Solution Approach 1:
The patent replaces stencil printing with electroplating, which enables fine pitch capability. The electroplating process can deposit metal in very close proximity without the physical constraints of stencil thickness and material flow, allowing for finer pitch dimensions while maintaining process simplicity through standardized electroplating equipment
4Reliability
If excessive solder material is used in printing, then the coverage is sufficient, but environmental harm increases due to material waste
Solution Approach 1:
The resist layer with precisely controlled openings ensures solder material is deposited only where needed, with exact dimensions and spacing. This localized deposition provides sufficient pad coverage while minimizing material usage, eliminating the waste associated with excessive material application in stencil printing
Solution Approach 2:
Electroplating inherently provides better material efficiency compared to stencil printing. The electrochemical process deposits metal atom-by-atom with high utilization efficiency, reducing material waste while ensuring adequate coverage for reliable electrical conduction
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 enables the formation of electrical conductive structures with fine pitch capabilities, overcoming the limitations of stencil printing by ensuring uniformity and reducing material waste, thus enhancing electrical conduction and environmental sustainability.
Implementation Method 1
electroplating in the openings of the resist layer to successively form a metal post and a conductive structure on the conductive layer on the second electrically conductive pads
Data Source
AI summary
A method for fabricating an electrical conductive structure of a circuit board is disclosed. The method includes providing a circuit board having a plurality of first and second electrically conductive pads; forming on the circuit board an insulating protection layer having a plurality of openings for exposing the first and second electrically conductive pads; forming a metal adhesive layer on the first and second electrically conductive pads; forming a conductive layer on the insulating protection layer and on the metal adhesive layer formed on the first and second electrically conductive pads, the conductive layer being electrical conductive to the first and second electrically conductive pads; forming on the conductive layer a resist layer having a plurality of openings for exposing the conductive layer on the second electrically conductive pads; and electroplating a conductive structure on the conductive layer on the second electrically conductive pads exposed from the openings.