Printed Wiring Board Seed Layer for Reliable Via Adhesion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing printed wiring boards face challenges in achieving stable adhesion between conductor circuits and resin insulating layers, particularly in via conductors, leading to potential breakage and reduced connection reliability under thermal stress.
Innovation Solution
A printed wiring board design featuring a seed layer with specific thickness distributions in its portions, including a first layer composed of an alloy containing copper, aluminum, and a specific metal, and a second layer of copper, ensuring strong adhesion and reduced stress concentration, while allowing for efficient electrolytic plating and minimizing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional seed layer with uniform thickness is used, then the manufacturing process is simple, but adhesion between conductor circuits and resin insulating layer is unstable leading to breakage under thermal stress
Solution Approach 1:
The seed layer is designed with non-uniform thickness distribution where the first portion (on resin insulating layer) has greater thickness than the second portion (in opening). This local quality variation enhances adhesion at the critical resin-conductor interface while maintaining structural integrity, directly resolving the adhesion stability issue without requiring complex multi-layer structures throughout the entire seed layer.
Solution Approach 2:
The seed layer comprises a composite structure with a first layer containing copper, aluminum and specific metals (nickel, zinc, gallium, silicon, or magnesium), and a second layer of pure copper. This composite material design optimizes both adhesion to the resin insulating layer and electrical conductivity, while the specific alloy composition enhances resistance to thermal stress and prevents breakage.
2Reliability
If the seed layer thickness is increased throughout to improve adhesion, then connection reliability improves, but manufacturing cost and material usage increase
Solution Approach 1:
Instead of uniformly increasing seed layer thickness, the invention applies greater thickness only at the first portion where adhesion to the resin insulating layer is critical. The second portion within the opening maintains adequate but reduced thickness, optimizing connection reliability while minimizing material consumption and manufacturing cost.
3Reliability
If electrolytic plating is applied to improve conductor properties, then electrical conductivity improves, but stress concentration increases leading to potential breakage
Solution Approach 1:
The two-layer seed layer structure with specific alloy composition (copper, aluminum, and 0.01-5 mass% of specific metals) provides optimized electrical conductivity while the gradient thickness design reduces stress concentration. The alloying elements enhance ductility and stress distribution, preventing breakage even after electrolytic plating is applied to improve electrical properties.
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
The design enhances adhesion and connection reliability, reduces stress concentration, and maintains signal integrity and power supply stability, even under thermal shock, thereby improving the overall quality and reliability of the printed wiring board.
Implementation Method 1
the seed layer has a first portion formed on the surface of the resin insulating layer, a second portion formed on an inner wall surface in the opening of the resin insulating layer, and a third portion formed on the first conductor layer
Implementation Method 2
the second conductor layer and via conductor include a seed layer and an electrolytic plating layer formed on the seed layer
Data Source
AI summary
A printed wiring board includes a first conductor layer, a resin insulating layer, a second conductor layer, and a via conductor formed in an opening of the insulating layer and connecting the first conductor and second conductor layers. The second conductor layer and via conductor include a seed layer having a first portion formed on the surface of the insulating layer, a second portion formed on an inner wall surface in the opening, and a third portion formed on a portion of the first conductor layer exposed by the opening. A thickness of the first portion is greater than a thickness of the second portion and a thickness of the third portion. The seed layer includes a first layer including an alloy including copper, aluminum and one or more metals selected from nickel, zinc, gallium, silicon, and magnesium, and a second layer formed on the first layer and including copper.