Printed Wiring Board Pad Bump Height Uniformity
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Solution Overview
Problem
Existing printed wiring boards face challenges in achieving high connection reliability when forming metal bumps on conductor pads of different sizes, as the shape and size variations can lead to inconsistent bump formation and potential connection failures.
Innovation Solution
A printed wiring board design featuring a coating insulating layer with specific opening portions exposing conductor pads of varying diameters, where metal bumps are formed to protrude equally in height from the surface, with the second metal bump covering the surrounding area, ensuring uniform connection reliability across different pad sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If metal bumps are formed on conductor pads of different sizes using conventional methods, then the conductor pads can accommodate varying design requirements, but the bump heights become inconsistent leading to connection reliability issues
Solution Approach 1:
The patent applies local quality by forming the second metal bump to cover the area of the coating insulating layer surrounding the second opening portion, creating a localized extension that compensates for the smaller pad size. This ensures that despite different pad diameters, both metal bumps achieve substantially equal protruding heights from the coating insulating layer surface, thereby maintaining consistent connection reliability across varying pad sizes
2Manufacturing precision
If the second metal bump is extended to cover surrounding areas, then uniform bump heights are achieved, but the manufacturing complexity increases
Solution Approach 1:
The patent employs asymmetry by designing the second metal bump with an extended configuration that covers the coating insulating layer area surrounding the second opening portion, while the first metal bump on the larger pad has a more conventional shape. This asymmetric design compensates for the size difference between pads and achieves uniform protruding heights without requiring complex additional manufacturing steps
Data Source
AI summary
A printed wiring board includes a conductor layer including first and second pads, a coating layer covering the conductor layer and having first opening exposing the first pad and second opening exposing the second pad, and metal bumps including a first bump on the first pad and a second bump on the second pad such that the first and second bumps protrude from the coating layer. The first and second openings are formed such that diameter of the second pad is smaller than diameter of the first pad. The first and second bumps are formed such that height of protruding portion of the first bump from the surface of the coating layer is substantially equal to height of protruding portion of the second bump from the surface of the coating layer and that the second bump covers an area of the coating layer on the surface surrounding the second opening.