Circuit Board Moisture Barrier Layer Against Corrosion
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Solution Overview
Problem
Conventional circuit boards are susceptible to oxidation and corrosion due to liquid or moisture permeation through the solder resist layer, leading to potential short circuits and reduced reliability.
Innovation Solution
Incorporation of a moisture barrier layer with a water vapor transmission rate (WVTR) of less than or equal to 1×10−2 g/m2·day to prevent liquid, moisture, or corrosive elements from permeating and protecting the circuit layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solder resist layer is used to cover the circuit layer, then the circuit layer is protected during manufacturing, but liquid or moisture can still permeate through the solder resist layer causing oxidation and corrosion
Solution Approach 1:
The patent applies composite materials by combining the solder resist layer with a moisture barrier layer having different functional properties. The moisture barrier layer uses inorganic materials or specific polymer compositions that provide superior moisture and corrosion resistance, creating a composite protective structure that addresses both manufacturing ease and long-term reliability
Solution Approach 2:
The moisture barrier layer serves as an intermediary between the solder resist layer and the circuit layer. This intermediate layer specifically targets moisture and corrosive substance permeation, which the solder resist layer alone cannot prevent, thereby mediating the protection function without compromising manufacturing processes
2Reliability
If the solder resist layer is made thicker to prevent permeation, then protection against oxidation improves, but manufacturing complexity and cost increase
Solution Approach 1:
The protective function is segmented into two distinct layers: the solder resist layer for basic manufacturing protection and the moisture barrier layer for specialized moisture and corrosion protection. This segmentation allows each layer to be optimized for its specific function with appropriate thickness and material properties, avoiding the need for an excessively thick solder resist layer
3Reliability
If a moisture barrier layer is added to prevent permeation, then reliability against corrosion improves, but device complexity increases
Solution Approach 1:
The moisture barrier layer is implemented as a thin film structure that provides effective moisture and corrosion protection without adding significant structural complexity. The thin film nature allows it to be integrated into existing circuit board manufacturing processes with minimal additional steps
Solution Approach 2:
The moisture barrier layer is designed to provide multiple protective functions simultaneously: preventing moisture permeation, blocking corrosive substances, and maintaining adhesion between layers. This multi-functionality reduces the need for additional specialized layers, thereby limiting the increase in device complexity
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 moisture barrier layer effectively blocks permeation, preventing oxidation and corrosion, thereby enhancing the reliability of the circuit board.
Implementation Method 1
The first moisture barrier layer covers the solder resist layer in such a way that the circuit layer and the solder resist layer are located between the substrate and the first moisture barrier layer. The first moisture barrier layer's water vapor transmission rate (WVTR) is less than or equal to 1×10−2 g/m2·day.
Data Source
AI summary
A circuit board includes a substrate, a circuit layer, a solder resist layer, and at least one moisture barrier layer. The circuit layer is provided on the substrate and covered by the solder resist layer. Inner and outer leads of the circuit layer are not covered by the solder resist layer. The moisture barrier layer covers the solder resist layer such that the circuit layer and the solder resist layer are located between the substrate and the moisture barrier layer. The moisture barrier layer is provided to block liquid or moisture such that liquid or moisture cannot permeate to the solder resist layer and the circuit layer to cause corrosion or oxidation of the circuit layer.