Wiring Substrate Seed Layer Thickness Control
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Solution Overview
Problem
Existing methods for forming wirings on insulating layers by electrolytic plating face challenges in achieving fine pitch wiring patterns with reliable insulation and low conductor resistance, often resulting in short circuits or deterioration of electrical characteristics due to excessive seed layer thickness and inadequate removal of exposed seed layer portions.
Innovation Solution
A wiring substrate is manufactured with a conductor layer having a polished surface, comprising a plating film and a seed layer, where the seed layer's thickness is limited to 2.5% of the total conductor layer thickness, and the wiring patterns are formed with a minimum width of 5 μm or less and an aspect ratio between 2.0 and 4.0, using a method that includes forming a seed layer, applying a plating resist with groove-shaped openings, electrolytic plating, and polishing to ensure adequate removal of the seed layer not covered by the plating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrolytic plating is used to form wirings on an insulating layer, then conductor resistance is reduced, but short circuits occur due to excessive seed layer thickness and inadequate removal of exposed seed layer portions
Solution Approach 1:
The patent严格控制种子层厚度占导体层总厚度的比例在2.5%或更小，通过精确控制这一关键参数，既保证了电解电镀的质量，又避免了种子层过厚导致的短路问题，同时确保了露出部分能够被充分去除
Solution Approach 2:
在电解电镀之前，预先形成厚度精确控制的种子层，为后续的电镀和抛光工艺奠定基础，确保最终导体层能够满足绝缘要求和电气性能要求
2Productivity
If fine pitch wiring patterns are formed with minimum wiring width of 5 μm or less, then wiring density is improved, but manufacturing precision requirements increase
Solution Approach 1:
通过控制线宽在5μm或更小、线间距在7μm或更小、高宽比在2.0至4.0范围内，实现高密度布线的同时，通过抛光工艺控制表面粗糙度，确保制造精度
Solution Approach 2:
采用电解电镀工艺替代传统的电镀方法，通过电场作用实现更精确的金属沉积控制，配合化学机械抛光（CMP）工艺，实现高精度表面处理
3Reliability
If the lower layer (seed layer) thickness is reduced to 2.5% or less of the conductor layer thickness, then insulation is improved, but the complexity of controlling layer thickness increases
Solution Approach 1:
通过建立种子层厚度与导体层总厚度的比例关系（2.5%或更小）作为控制标准，形成可量化的反馈机制，确保在多层结构中种子层厚度始终处于合理范围内，平衡了绝缘性能与工艺可控性
Solution Approach 2:
将种子层厚度从绝对值控制转变为相对值控制（占总厚度的2.5%或更小），使控制标准更加灵活和可操作，降低了工艺复杂度
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 enables the formation of wiring substrates with fine pitch wiring patterns that maintain desired insulation and electrical characteristics, reducing the risk of short circuits and ensuring low conductor resistance, thereby improving signal transmission efficiency.
Implementation Method 1
forming, in the groove-shaped openings, an electrolytic plating film
Implementation Method 2
polishing the electrolytic plating film and the plating resist such that a thickness of the electrolytic plating film and a thickness of the plating resist are reduced
Data Source
AI summary
A wiring substrate includes an insulating layer, and a conductor layer formed on a surface of the insulating layer and including wiring patterns such that the conductor layer has a polished surface on the opposite side with respect to the insulating layer and includes an upper layer including a plating film and a lower layer including a seed layer for the plating film and directly formed on the surface of the insulating layer. The conductor layer is formed such that a ratio of a thickness of the lower layer to a thickness of the conductor layer is 2.5% or less, the wiring patterns have the minimum wiring width of 5 μm or less and the minimum inter-wiring distance of 7 μm or less, and each of the wiring patterns has an aspect ratio in a range of 2.0 to 4.0.