Multi-Layer Via Pad Tapered Width for Fine PCB Patterns
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Solution Overview
Problem
The challenge is to implement fine circuit patterns with a line/space (L/S) ratio of 5/5 or less on printed circuit boards without increasing costs, while ensuring the stability of via pads and external solder connection pads, as thick dry film resist can hinder this process and lead to defects.
Innovation Solution
The solution involves a printed circuit board design with a via pad composed of multiple layers, where the second layer has a decreasing width in the stacking direction, allowing for a thicker via pad to be formed simultaneously with the fine circuit unit, using techniques like tenting and plating to prevent defects during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick dry film resist is used to ensure via pad thickness, then the via pad stability is improved, but the circuit pattern resolution deteriorates
Solution Approach 1:
The via pad structure is segmented into multiple layers: a first via pad layer embedded in the insulating layer and a second via pad layer disposed on the first via pad layer. This segmentation allows the first layer to provide thickness for stability while the second layer can be formed with precise patterns for fine circuits, resolving the contradiction between via pad stability and circuit pattern resolution
Solution Approach 2:
The solution transitions from a single-layer via pad to a multi-layer via pad structure in the vertical dimension. The first via pad layer provides the necessary thickness embedded in the insulating layer, while the second via pad layer is formed on top with precise patterning, allowing both thickness requirements and fine circuit resolution to be satisfied simultaneously
2Stability of the object's composition
If a thick dry film resist is used to maintain via pad thickness, then the via pad structural integrity is improved, but the L/S ratio implementation becomes difficult
Solution Approach 1:
The via pad is divided into a first via pad layer for structural integrity and a second via pad layer for fine pattern formation. This segmentation enables the first layer to be formed with sufficient thickness for structural stability while the second layer can be precisely patterned to achieve L/S ratios of 5/5 or less, making fine circuit implementation feasible
Solution Approach 2:
The first via pad layer is formed preliminarily as an embedded structure in the insulating layer before forming the second via pad layer. This preliminary action establishes the structural foundation and thickness requirements, allowing subsequent fine circuit patterns to be formed with precise L/S ratios without compromising via pad integrity
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 design enables the stable implementation of fine circuit patterns with a high L/S ratio of 5/5 or less, preventing defects in via pads and ensuring reliable solder connections, while maintaining a thin dry film resist for efficient circuit formation.
Implementation Method 1
the second layer has a width decreasing in a direction away from the first layer in a stacking direction
Implementation Method 2
a via pad including a first layer embedded in the first insulating layer and a second layer disposed on the first layer
Data Source
AI summary
A printed circuit board includes: a first insulating layer; a via pad including a first layer embedded in the first insulating layer and a second layer disposed on the first layer; and a first via layer disposed on the via pad, wherein the second layer has a width decreasing in a direction away from the first layer in a stacking direction of the first and second layers.