Bulged Via Structure for Multilayer PCB Drop-Shock Resistance
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Solution Overview
Problem
Conventional multilayer printed wiring boards face challenges in maintaining reliability and drop-shock resistance due to external stress, as conductor circuits are prone to cracking and separation under impact, and insulating layers can warp, leading to reduced reliability and component detachment.
Innovation Solution
The multilayer printed wiring board design features viaholes that bulge orthogonally to the insulating layer thickness, forming a multistage stacked via structure, which enhances electrical connectivity and prevents warping by acting as a stake within the insulating layers, maintaining flatness and reliability even under external stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional viaholes are used in multilayer printed wiring boards, then the manufacturing process is simple, but the viaholes are prone to breaking and conductor circuits can crack or separate under external stress
Solution Approach 1:
The viahole is designed with a bulged intermediate portion that curves outward in the thickness direction, transforming the conventional straight cylindrical viahole into a curved, barrel-shaped structure. This curvature distributes stress more effectively during drop shocks, preventing viahole breakage and conductor circuit cracking while maintaining manufacturing feasibility through controlled deposition processes
2Strength
If the viahole structure is simplified for easy manufacture, then manufacturing is easier, but the board lacks sufficient rigidity and warping occurs under external stress
Solution Approach 1:
The viahole structure transitions from uniform thickness to non-uniform thickness with a bulged intermediate portion. This local quality change concentrates material where stress occurs during drop shocks, enhancing interlayer connectivity and preventing warping without requiring complex manufacturing processes throughout the entire viahole structure
Data Source
AI summary
A method of forming a circuit board which includes generating laser light with a carbon dioxide laser and making a hole through an insulating substrate by irradiating the insulating substrate with the laser light. The hole includes a top opening in a top surface of the insulating substrate, a bottom opening in a bottom surface of the insulating substrate, and an inner wall extending from the top opening to the bottom opening along a thickness direction of the insulating substrate, the inner wall including a bulge which extends in a direction generally orthogonal to the thickness direction. A via hole is formed in the insulating substrate by providing metal in the hole such that the metal extends from the top opening to the bottom opening along the inner wall, and completely closes each of the top and bottom openings.