PCB Tin Plating Peel Length Control for Corrosion Prevention
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Solution Overview
Problem
Printed circuit boards face disconnection issues due to corrosion of the conductive pattern caused by electroless plating solutions, leading to unreliable connections with electronic components.
Innovation Solution
A printed circuit board design featuring a conductive pattern with a tin plating layer and a coating layer, where the average peel length of the coating layer from the conductive pattern is less than or equal to 20 μm, and a tin copper alloy layer with a thickness between 0.1 μm and 0.5 μm, along with a manufacturing method involving room temperature and heated electroless tin plating, to prevent corrosion and ensure reliable bonding with electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electroless plating solution is applied to form tin plating layer, then bonding strength with electronic components is improved, but corrosion of conductive pattern occurs leading to disconnection
Solution Approach 1:
A coating layer is introduced as an intermediary between the electroless plating solution and the conductive pattern. This coating layer selectively peels off in controlled regions to expose the conductive pattern for tin plating while protecting other areas from corrosion by the plating solution, thus enabling bonding strength improvement without causing harmful corrosion to the entire conductive pattern
Solution Approach 2:
The coating layer is designed with spatially varying properties - it has different peel lengths in different regions. By controlling the peel length to be less than or equal to 20 μm in specific areas, the invention enables localized tin plating only where needed for bonding, while other areas remain protected from corrosion through the intact coating layer
2Reliability
If coating layer peel length is reduced to prevent corrosion, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The coating layer is pre-formed with controlled adhesion properties before the electroless plating process. The peel length is predetermined by the coating layer design and processing conditions, allowing the corrosion protection function to be achieved without requiring high-precision control during the actual plating operation
Solution Approach 2:
The invention controls the peel length by adjusting processing parameters such as coating layer thickness, composition, and processing conditions rather than requiring precise mechanical control. By setting the peel length to be less than or equal to 20 μm through parameter optimization, the invention achieves reliable corrosion protection while maintaining manufacturing feasibility
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 prevents disconnection of the conductive pattern and enhances bonding strength with electronic components through controlled tin plating, reducing the risk of corrosion and whisker generation, thereby ensuring reliable electrical connections.
Implementation Method 1
immersing a layered structure including the base film, the conductive pattern, and the coating layer in a room temperature electroless tin plating solution; and an electroless plating step of immersing the layered structure including the base film, the conductive pattern, and the coating layer in a heated electroless tin plating solution
Data Source
AI summary
According to one aspect of the present invention, a printed circuit board includes: an insulating base film; a conductive pattern that is partially layered on a surface side of the base film; a coating layer that is layered on a surface of a layered structure including the base film and the conductive pattern and having an opening portion that partially exposes the conductive pattern; and a tin plating layer that is layered on a surface of the conductive pattern exposed from the opening portion, wherein an average peel length of the coating layer from the conductive pattern with an inner edge of the opening portion as a base end is less than or equal to 20 μm.