Circuit Board Solder Resist Structure for Fine Trace Stability
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Solution Overview
Problem
Conventional circuit boards with fine circuit patterns face issues of pattern collapse and reliability due to exposure at the outermost portion, especially in high-frequency applications like 5G communication systems, where the patterns are prone to external impacts and require stable integration and protection.
Innovation Solution
A circuit board structure with a solder resist layer that supports the outer layer circuit pattern, featuring varying heights and surface coverage to stabilize and protect the circuit pattern, using a primer layer to enhance bonding and minimize deformation during etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the circuit pattern is disposed at the outermost portion to achieve fine circuit integration, then the circuit line width can be reduced, but the circuit pattern easily collapses due to external impacts
Solution Approach 1:
A solder resist layer is formed to cover and protect the outermost circuit pattern, providing mechanical support and preventing collapse while maintaining the fine circuit line width. The solder resist acts as a protective film that reinforces the fragile outermost circuit traces.
Solution Approach 2:
The circuit pattern is embedded within the insulating layer rather than being disposed on the outermost surface, transitioning from a two-dimensional surface arrangement to a three-dimensional embedded structure. This embedding provides mechanical support from the insulating layer while maintaining fine circuit integration.
2Reliability
If the circuit pattern is embedded in the insulating layer to prevent collapse, then the circuit stability is improved, but the circuit pattern cannot be effectively protected from external impacts
Solution Approach 1:
The solder resist layer serves as a protective shell covering the embedded circuit pattern, providing dual functionality: mechanical support to prevent collapse and protection against external impacts such as oxidation and physical damage.
3Reliability
If the solder resist covers the entire outer layer circuit pattern to provide protection, then the circuit pattern stability is improved, but the electrical connection is compromised
Solution Approach 1:
The solder resist layer is selectively formed to cover only specific portions of the outer layer circuit pattern, such as signal transmission lines, while leaving pad regions exposed. This local differentiation provides protection where needed while maintaining electrical connection at pad areas for component mounting and signal transmission.
4Productivity
If the circuit pattern is made fine to increase integration density, then the degree of circuit integration is improved, but the circuit pattern becomes more susceptible to collapse and external impacts
Solution Approach 1:
The solder resist layer provides a protective envelope around fine circuit patterns, enabling high integration density while compensating for the reduced mechanical strength of finer traces through the reinforcing protective layer.
Solution Approach 2:
Embedding fine circuit patterns within the insulating layer structure provides three-dimensional mechanical support, allowing higher integration density while the insulating layer itself acts as a structural matrix preventing collapse of delicate fine traces.
Data Source
AI summary
A circuit board according to an embodiment includes: an insulating layer including first to third regions; an outer layer circuit pattern disposed on an upper surface of the first to third regions of the insulating layer; and a solder resist including a first part disposed on the first region of the insulating layer, a second part disposed on the second region, and a third part disposed on the third region, wherein the outer layer circuit pattern includes: a first trace disposed on an upper surface of the first region of the insulating layer; and a second trace disposed on an upper surface of the third region of the insulating layer; wherein a height of the first trace is different from a height of the second trace; and an upper surface of the first part of the solder resist is positioned lower than an upper surface of the first trace.