PCB Connection Pad Surface Treatment for Line Width Control
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Solution Overview
Problem
The expansion of nickel and gold plating on copper connection pads in printed circuit boards makes it difficult to secure a desired line width, especially in fine pitch applications, and the existing Ni/Au plating process complicates the securement of line width when pads are embedded through the embedded trace substrate method.
Innovation Solution
A printed circuit board structure is designed with a surface treatment layer disposed only on the upper surface of the connection pad, not extending to the side surface, allowing for a partially protruding and partially embedded connection pad configuration, which secures the line width and prevents short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni/Au plating is applied to both upper surface and side surface of the connection pad, then surface treatment and protection are improved, but line width is reduced and short circuit risk increases
Solution Approach 1:
The patent applies surface treatment selectively only to the upper surface of the connection pad, not the side surface. This local differentiation allows the upper surface to have protective plating while the side surface remains exposed, maintaining line width and preventing short circuits between adjacent pads.
2Ease of manufacture
If connection pad is completely embedded in the insulating layer, then integration is improved, but wire bonding becomes difficult and line width control is compromised
Solution Approach 1:
The connection pad is divided into two parts: an embedded portion within the insulating layer for integration, and an exposed upper surface for wire bonding. This segmentation allows both embedding and wire bonding to coexist effectively.
3Ease of manufacture
If Ni/Au plating is performed after pad formation in ETS method, then manufacturing process is completed, but line width expansion occurs making fine pitch difficult
Solution Approach 1:
The patent restricts plating to only the upper surface of the connection pad, preventing plating expansion on the side surfaces. This local application maintains precise line width control even after plating is performed in the ETS manufacturing process.
Data Source
AI summary
A printed circuit board includes: an insulating layer; a first circuit layer disposed on one surface of the insulating layer, and including a first circuit pattern and a first connection pad; and a surface treatment layer disposed on one surface of the first connection pad. The other surface of the first connection pad is covered by the insulating layer, and at least a portion of a side surface of the first connection pad is spaced apart from the insulating layer.