Tapered Via Conductor Design for High-Density Circuit Boards
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Solution Overview
Problem
Circuit boards with multilayer wiring structures face issues with via conductor reliability due to vertical inner wall angles, leading to reduced film thickness and potential disconnection, which hinders high-density mounting.
Innovation Solution
The via conductor is designed with a tapered shape, featuring a greater diameter reduction per unit depth in the first section compared to the second section, alleviating the edge angle and increasing connection reliability while allowing for high-density mounting by bringing the semiconductor IC closer to the via.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tapered angle of the inner wall of the via is increased to improve connection reliability, then the film thickness of the conductor layer is maintained and disconnection is prevented, but the occupied area of the via increases, preventing high density mounting
Solution Approach 1:
The via is divided into two distinct sections: a first section with a larger tapered angle (greater diameter reduction per unit depth) and a second section with a smaller tapered angle (nearly vertical inner wall). This segmentation allows each section to fulfill different functions - the first section provides adequate conductor layer coverage and connection reliability, while the second section minimizes the occupied area for high density mounting.
Solution Approach 2:
Different portions of the via are given different geometric properties. The first section has a larger tapered angle to ensure proper conductor layer formation and connection reliability at the via entrance, while the second section has a smaller tapered angle to reduce the overall occupied area. This local differentiation of geometric quality resolves the contradiction between reliability and area occupation.
2Area of stationary object
If the inner wall of the via is made nearly vertical to reduce occupied area, then high density mounting is enabled, but the film thickness of the conductor layer is reduced and disconnection may occur
Solution Approach 1:
The via structure is segmented into two sections where the first section provides the necessary tapered geometry for reliable conductor layer formation, while the second section maintains a nearly vertical profile to minimize occupied area. This segmentation ensures that both requirements - adequate film thickness and small occupied area - are satisfied in different portions of the same via.
Solution Approach 2:
The via exhibits local quality variation with different tapered angles in different sections. The first section has a larger tapered angle to ensure proper conductor layer coverage and prevent disconnection, while the second section has a smaller tapered angle to reduce the occupied area, thereby enabling high density mounting without compromising connection reliability.
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 configuration enhances the connection reliability of the via conductor and enables high-density mounting by reducing the planar size of the circuit board, thereby improving overall performance.
Implementation Method 1
forming a via penetrating the insulating layer by applying laser processing to the center of the opening
Implementation Method 2
enlarging, after application of the laser processing, the diameter of the upper portion of the via by performing blasting with the first conductor layer as a mask
Data Source
AI summary
Disclosed herein is a circuit board that includes first and second conductor layers, an insulating layer positioned between the first and second conductor layers, and a via conductor formed inside a via penetrating the insulating layer and connecting the first and second conductor layers. The via has a shape in which a diameter thereof is reduced in a depth direction. The via has a first section positioned on the first conductor layer side and a second section positioned on the second conductor layer side. A reduction in the diameter per unit depth in the first section is greater than that in the second section.