Partial Solder-Mask PCB Coating to Prevent Voids and Delamination
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Solution Overview
Problem
Conventional circuit board manufacturing methods using extensive solder-mask lead to voids and gaps under conformal-coatings, which can collect moisture and contaminants, leading to issues like corrosion and delamination, particularly in areas proximate to electrical connections.
Innovation Solution
Reducing and minimizing the use of solder-mask regions and introducing conformal-coatings to cover both solder-mask and adjacent mask-free areas, with specific material selections for improved adhesion and solder-wetting control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extensive solder-mask is used to control solder wetting during assembly, then solder-wetting control is improved, but voids and gaps are created under conformal-coating which lead to moisture and contaminant ingress
Solution Approach 1:
The patent applies local quality by differentiating the surface treatment into distinct regions: solder-mask regions where solder-wetting control is needed, and mask-free regions where conformal-coating directly contacts the substrate. This localized differentiation allows each region to serve its specific function optimally without compromising the other.
Solution Approach 2:
The patent segments the circuit board surface into multiple functional zones including solder-mask regions, mask-free regions, and conformal-coating regions. This segmentation enables independent optimization of each zone's properties and prevents the formation of continuous voids that would compromise encapsulation reliability.
2Manufacturing precision
If solder-mask is applied to the whole top surface to control solder wetting, then solder-wetting control is improved, but adhesion of conformal-coating becomes inconsistent due to uneven surface topology
Solution Approach 1:
The patent creates mask-free regions where the substrate surface is exposed and treated specifically for conformal-coating adhesion. These regions have optimized surface properties (cleanliness, roughness, chemical composition) that enhance coating bonding, while solder-mask regions maintain their original function of controlling solder wetting during assembly.
3Area of stationary object
If conformal-coating is applied over solder-mask regions to provide encapsulation, then encapsulation coverage is improved, but voids and gaps form at the edges of solder-mask regions
Solution Approach 1:
The patent extracts or removes the solder-mask material from specific mask-free regions where it would create voids and gaps. By taking out the solder-mask from these particular areas, the conformal-coating can make direct contact with the substrate, eliminating the harmful voids while maintaining encapsulation coverage in other areas where solder-mask is still needed.
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 enhances encapsulation reliability by minimizing voids and gaps, reducing moisture and contaminant ingress, thereby preventing corrosion and delamination, particularly in critical electrical connection areas.
Implementation Method 1
Encapsulation using one or more conformal layers is thus a critical component for the design of a medical device—it acts as a barrier between these ionic fluids and critical electronic/electric interfaces to reduce and/or prevent degradation of the implant electronics
Implementation Method 2
solder-masking is an essential step to control solder wetting during assembly
Data Source
AI summary
Circuit boards have a complex surface topology, which can lead to uneven coating thicknesses and inconsistent adhesion. To improve coating reliability, a circuit board is provided with a surface including a conductive-trace extending between a first solder-pad and a third pad. A solder-mask region covers a portion of the conductive-trace. A second solder-pad is provided, adjacent to a mask-free region arranged to be free of solder mask. The first solder-pad and second solder-pad are each arranged to retain at least one electrical connection of the same electrical component. A conformal-coating is provided to cover at least the solder-mask region and the mask-free region. By greatly reducing or minimizing the use of solder-mask in the region covered by the conformal-coating, encapsulation quality can be improved.