Multilayer Circuit Board Via Structure for Crack-Resistant Interconnects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multilayer circuit boards face issues with cracks in interlayer connection conductors due to high vertical loads during manufacturing, and using Ag-based conductive paste increases the risk of migration and manufacturing costs.
Innovation Solution
The multilayer circuit board design incorporates interlayer connection conductors with a first portion made of Cu and a second portion made of Ag-based alloy, featuring intermediate Cu-Sn layers to enhance malleability and reduce migration risk, while minimizing Ag usage to control costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cu alloy-based conductive paste is used for the second via portion, then the interlayer connection conductor has high strength and good malleability, but cracks are likely to occur under vertical load during collective pressing
Solution Approach 1:
The patent applies composite materials by creating a multi-layer conductive structure consisting of a first via portion made of Cu alloy-based conductive paste and a second via portion made of Ag alloy-based conductive paste. This composite structure combines the high strength and malleability of Cu alloy with the excellent malleability and crack resistance of Ag alloy, allowing the interlayer connection conductor to withstand vertical loads during collective pressing without cracking.
Solution Approach 2:
The patent applies local quality by using different materials for different portions of the interlayer connection conductor. The first via portion (lower section) uses Cu alloy-based conductive paste for strength, while the second via portion (upper section) uses Ag alloy-based conductive paste for superior malleability and crack resistance. This localized material optimization ensures each portion performs its specific function effectively under collective pressing conditions.
2Reliability
If Ag alloy-based conductive paste is used for the second via portion, then malleability is excellent and cracks are reduced, but migration risk increases and manufacturing cost increases
Solution Approach 1:
The patent applies local quality by using Ag alloy-based conductive paste only in the second via portion where it is most needed for crack resistance, while using Cu alloy-based conductive paste in the first via portion. This localized application of expensive Ag material minimizes the total amount of Ag used, thereby reducing migration risk and manufacturing cost while still achieving the desired reliability improvement in the critical upper section.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the thickness and composition parameters of the Ag alloy-based conductive paste in the second via portion. By optimizing these parameters, the patent achieves sufficient malleability and crack resistance with the minimum necessary amount of Ag material, thus balancing reliability improvement with cost control and migration risk reduction.
Data Source
AI summary
A multilayer circuit board includes an insulating base including insulating layers, and first and second main surfaces stacked in a stacking direction, conductor layers between the insulating layers and on the first and/or second main surfaces, and interlayer connection conductors penetrating at least one of the insulating layers. The conductor layers include first, second, third, and fourth conductor layers, each including Cu foil. The interlayer connection conductors include a first interlayer connection conductor between the first and second conductor layers, and a second interlayer connection conductor between the third and fourth conductor layers. The first interlayer connection conductor includes a first portion including Cu as a main component and a second portion including a single metal or an alloy including Ag as a main component.