Wiring Board Via Conductor Alloy Buffer Layer
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Solution Overview
Problem
The recent refinement of design rules in wiring boards has led to reduced via diameters, resulting in increased concerns over connection reliability between insulating layers.
Innovation Solution
The implementation of an alloy layer containing the same metal as the first wiring conductor layer, tin, and nichrome between the first via land and the first base layer, which is formed of nichrome, to act as a buffer material and facilitate crystal connection between different metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If via diameter is reduced according to refined design rules, then wiring board miniaturization is achieved, but connection reliability between insulating layers deteriorates
Solution Approach 1:
The invention uses a composite base layer structure consisting of a first base layer containing nichrome and a second base layer containing the same metal as the via conductor. This composite structure provides both adhesion strength and stress distribution capabilities, enabling reliable connections in reduced-size vias
Solution Approach 2:
An alloy layer containing the same metal as the first wiring conductor layer, tin, and nichrome is introduced as an intermediary between the via land and the first base layer. This alloy layer facilitates crystal connection and reduces stress concentration, maintaining connection reliability despite smaller via dimensions
2Device complexity
If different metal layers are directly connected without intermediate layers, then manufacturing process is simplified, but stress concentration and crack occurrence increase
Solution Approach 1:
The alloy layer acts as a mediator between the via land and the nichrome base layer, enabling gradual transition of crystal structures and reducing stress concentration. This intermediate layer prevents direct contact between dissimilar metals, reducing thermal and mechanical stress
Solution Approach 2:
The invention changes the material parameters gradually from the via land through the alloy layer to the base layer. The alloy layer has intermediate properties that bridge the gap between the via land metal and the nichrome base layer, facilitating smooth stress distribution
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 alloy layer reduces stress and crack occurrence between the via land and the via conductor, enhancing the connection reliability by ensuring continuous crystal orientation across metal boundaries.
Implementation Method 1
forming, by sputtering, a first base layer formed of nichrome on the inner surface of the via hole and the upper surface of the first via land; forming, by sputtering, a second base layer on the upper surface of the first base layer
Data Source
AI summary
A wiring board includes: first and second insulating layers; a first wiring conductor layer located between the first and second insulating layers and including a first via land; a second wiring conductor layer located on the second insulating layer and including a second via land; a via hole penetrating from the upper to lower surfaces of the second insulating layer; and a via conductor located in the via hole and electrically connecting the first second via lands. The via conductor is located on the inner surface of the via hole and on the first via land via a first base layer containing nichrome and a second base layer located on the upper surface of the first base layer and containing the same metal as the via conductor. An alloy layer containing tin and nichrome is located between the first via land and the first base layer.