Wiring Board Dummy Pads for Plating Uniformity
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Solution Overview
Problem
Existing wiring boards with both high-density and low-density pad arrangements face challenges in achieving uniform electroless plating, leading to potential short-circuits in high-density regions and inadequate deposition in low-density regions due to difficulties in adjusting plating conditions optimally for both areas.
Innovation Solution
Incorporating dummy pads arranged outside the low-density region, juxtaposed to the outermost peripheral pads, helps in reducing the effects of reaction inhibitors and improving nickel deposition uniformity, thereby preventing short-circuits and ensuring uniform plating across different density regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plating conditions are adjusted for the low-density region, then adequate deposition is achieved on low-density pads, but plated layer protrudes between adjacent pads causing short-circuits in high-density region
Solution Approach 1:
The dummy pads create localized modifications in the low-density region that restrict reaction inhibitor diffusion and alter fluid flow patterns only where needed. This local intervention ensures adequate deposition on low-density pads without causing excessive plating growth in the high-density region, thereby preventing short-circuits while maintaining reliability
2Manufacturing precision
If pads are arranged at constant density, then uniform plating conditions are achieved, but adaptability to different semiconductor chip designs is reduced
Solution Approach 1:
The patent maintains constant pad density for uniform plating while introducing dummy pads as a local modification mechanism. This allows the wiring board to adapt to different semiconductor chip designs with varying pad density requirements by strategically placing dummy pads in low-density regions, thus achieving both plating uniformity and design adaptability
Solution Approach 2:
The patent segments the pad arrangement region into functional areas (high-density regions with actual pads and low-density regions with dummy pads). This segmentation allows different plating behaviors to be controlled in different zones, enabling the board to accommodate various chip designs while maintaining overall plating uniformity through the dummy pad mechanism
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 arrangement of dummy pads allows for improved nickel plating uniformity and prevents short-circuits between adjacent pads in high-density regions, while ensuring adequate deposition in low-density regions, thus enabling effective electrical connections.
Implementation Method 1
the surface treatment forms a plated layer on the pads by electroless plating
Data Source
AI summary
A wiring board includes an insulator layer having a top surface, and a plurality of pads arranged in a pad arrangement region on the top surface of the insulator layer. The pad arrangement region includes a first region in which a first plurality of pads among the plurality of pads are arranged at a first density, and a second region in which a second plurality of pads among the plurality of pads are arranged at a second density lower than the first density. At least one dummy pad is arranged juxtaposed to at least one of the second plurality of pads in the second region of the pad arrangement region.