Printed Wiring Board Seed Layer Geometry for Width-Controlled Circuits

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Solution Overview

Problem

Existing printed wiring boards face challenges in achieving precise control over the width and thickness of conductor layers and via conductors, leading to issues with adhesion and electrical resistance, particularly due to uneven surfaces and inconsistent etching rates during manufacturing.

Innovation Solution

The implementation of a structured seed layer with a first layer having a greater width than a second layer, and an electrolytic plating layer with an even wider width, combined with a smooth inner wall surface formed by controlled etching of inorganic particles, ensures precise conductor layer formation and improved adhesion, reducing electrical resistance and stress concentration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a conventional single-layer seed layer is used, then the manufacturing process is simple, but the control over conductor width and thickness is imprecise

Engineering Contradiction:

Improvecontrol over conductor width and thicknessVSAvoidseed layer structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The seed layer is divided into two distinct layers: a first seed layer and a second seed layer. The first seed layer has a first width and the second seed layer has a second width that is smaller than the first width. This segmentation allows independent control of each layer's dimensions, enabling precise control over the final conductor width and thickness that cannot be achieved with a single-layer seed layer.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the conductor layer width is reduced to achieve finer circuits, then the circuit density increases, but the adhesion and electrical resistance become problematic

Engineering Contradiction:

Improveconductor circuit widthVSAvoidadhesion and electrical resistance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The segmented two-layer seed layer structure enables the first seed layer to provide a wider base for better adhesion and the second seed layer to define the narrower final conductor width. This separation of functions allows fine conductor circuits to be formed while maintaining adequate adhesion and electrical properties through the wider first layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the seed layer structure are given different widths and properties: the first seed layer has a larger width optimized for adhesion and electrical connection, while the second seed layer has a smaller width optimized for the final conductor dimensions. This local differentiation of properties allows simultaneous optimization of adhesion and conductor precision.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If etching is used to form via openings, then the via conductors are formed, but the surface becomes uneven and causes stress concentration

Engineering Contradiction:

Improvevia conductor formationVSAvoidsurface smoothness and stress distribution

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The via openings are formed by etching the resin insulating layer before the conductor layers are deposited. By performing this etching operation in advance, the subsequent plating process can fill the pre-formed openings without requiring additional etching steps that would create surface unevenness. This preliminary action separates the via formation from the conductor formation processes.

Inventive Principle:

Principle #10Preliminary action

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 allows for the formation of conductor circuits with controlled widths and reduced electrical resistance, enhancing connection reliability and stress management, while maintaining a smooth surface finish.

Implementation Method 1

a second conductor layer formed on a surface of the resin insulating layer and including a conductor circuit, and a via conductor formed in an opening formed in the resin insulating layer such that the via conductor is connecting the first conductor layer and the second conductor layer. The second conductor layer and the via conductor include a seed layer and an electrolytic plating layer formed on the seed layer

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS12495489B2Printed wiring board

Publication Date: 2025.12.09 IBIDEN CO LTD

AI summary

A printed wiring board includes a first conductor layer, an insulating layer formed on the first conductor layer, a second conductor layer formed on a surface of the insulating layer and including a conductor circuit, and a via conductor formed in an opening formed in the insulating layer and connecting the first and second conductor layers. The second conductor layer and via conductor include a seed layer and an electrolytic plating layer formed on the seed layer such that the seed layer has a first layer and a second layer formed on the first layer, the first layer has a width greater than a width of the second layer in cross section of the conductor circuit in the second conductor layer and that the electrolytic plating layer has a width greater than the width of the first layer in cross section of the conductor circuit in the second conductor layer.