Printed Wiring Board Pad Dam Structure for Underfill Containment
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Solution Overview
Problem
Existing printed wiring boards face challenges in preventing underfill material outflow and ensuring reliable connections to fine-pitch IC pads, with current dam structures either failing to adequately stop material flow or compromising connection reliability due to material mismatch and increased manufacturing processes.
Innovation Solution
A printed wiring board design featuring a dam structure integrated into the outermost resin layer that surrounds the pad group, formed using a mask and plasma treatment to expose metal posts, ensuring the dam is strong and reliable without separate connecting parts, thus preventing underfill material outflow and connection failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate dam structure is formed to prevent underfill material outflow, then underfill material containment is improved, but device complexity and manufacturing process count increase
Solution Approach 1:
The dam structure is merged with the outermost resin layer to form an integrated structure. The outermost resin layer is formed with a predetermined thickness that is thicker than the metal posts, creating a dam structure that is inherently part of the resin layer rather than a separate component. This eliminates the need for additional dam formation processes and reduces overall structure complexity while maintaining effective underfill material containment.
Solution Approach 2:
The outermost resin layer serves multiple functions simultaneously: it provides the dam structure for containing underfill material, protects the conductor circuit, and forms the final surface of the printed wiring board. By making the outermost resin layer thicker than the metal posts in specific regions, it performs both the protective function of a resin layer and the containment function of a dam structure.
2Reliability
If a separate dam structure is formed to prevent underfill material outflow, then underfill material containment is improved, but manufacturing cost increases
Solution Approach 1:
The dam structure is merged with the outermost resin layer to form an integrated structure. The outermost resin layer is formed with a predetermined thickness that is thicker than the metal posts, creating a dam structure that is inherently part of the resin layer rather than a separate component. This eliminates the need for additional dam formation processes and reduces overall structure complexity while maintaining effective underfill material containment.
3Manufacturing precision
If metal posts are exposed from outermost resin layer for fine-pitch IC pad connections, then connection precision is improved, but underfill material outflow risk increases
Solution Approach 1:
The outermost resin layer has varying thickness at different locations. In regions where metal posts are exposed for fine-pitch IC pad connections, the resin layer thickness is reduced to expose the metal posts. In surrounding regions, the resin layer maintains a greater thickness to form the dam structure. This local variation in thickness achieves both precise connections and effective underfill material containment.
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 integrated dam structure effectively prevents underfill material outflow and enhances connection reliability to fine-pitch IC pads, reducing manufacturing processes and costs by eliminating material mismatch and potential peeling issues, while maintaining robustness and reliability.
Implementation Method 1
forming a mask at a dam formation site for a dam structure of the outermost resin layer to surround at least part of a pad group including the metal posts on the outermost resin layer, and reducing a thickness of the outermost resin layer exposed from the mask
Data Source
AI summary
A method for manufacturing a printed wiring board includes forming metal posts on a conductor circuit formed on a resin insulating layer, forming the outermost resin layer on the resin insulating layer such that the metal posts is embedded in the outermost resin layer, forming a mask at a dam formation site for a dam structure of the outermost resin layer to surround at least part of a pad group including the metal posts on the outermost resin layer, and reducing a thickness of the outermost resin layer exposed from the mask such that end portions of the metal posts are exposed from the outermost resin layer, that the metal posts form the pad group, and that the outermost resin layer has the dam structure forming part of the outermost resin layer and formed to surround at least part of the pad group including the metal posts.