Semi-Automatic Copper Foil Surface Roughness Detection from PCB Microsection Images

Abstract

Characterization of surface roughness of printed circuit board (PCB) conductors is an important task as a part of signal-integrity analysis on high-speed multi-GHz designs. However, there are no methods to adequately quantify roughness of a signal trace or a power/reference plane layer within finished PCBs. Foil roughness characterization techniques currently available can only be applied to the base foil, prior to its incorporation into a finished board. In a finished PCB, a foil surface is not directly accessible, as it is embedded in the dielectric of the board, and attempting to expose the surface will damage the board and the surface of interest. In this paper, a method of surface roughness quantification from microsectioned samples of PCBs is presented. A small, non-functional area, e.g., a corner of the PCB, can be removed, and the surface roughness of the circuit layers can be assessed without impairing the function of the PCB. In the proposed method, a conductor (a trace or a plane) in the microsectioned sample is first digitally photographed at high magnification. The digital photo obtained is then used as an input to a signal- and image-processing algorithm within a graphical user interface. The GUI-based tool automatically computes and returns the surface roughness values of the layer photographed. The tool enables the user to examine the surface textures of the two sides of the conductor independently. In the case of a trace, the composite value of roughness, based on the entire perimeter of the trace cross-section, can be calculated.

Meeting Name

IEEE International Symposium on Electromagnetic Compatibility (2012: Aug. 5-10, Pittsburgh, PA)

Department(s)

Electrical and Computer Engineering

Research Center/Lab(s)

Electromagnetic Compatibility (EMC) Laboratory

Keywords and Phrases

A-Plane; Characterization Techniques; Copper Foils; Digital Photos; Foil Surfaces; Image-Processing Algorithms; Non-Functional; Plane Layers; Semi-Automatics; Signal Integrity Analysis; Signal Traces; Surface Textures; Electromagnetic Compatibility; Graphical User Interfaces; Surface Roughness; Printed Circuit Boards

International Standard Book Number (ISBN)

978-1467320610; 978-1467320603

International Standard Serial Number (ISSN)

2158-110X; 2158-1118

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2012 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Aug 2012

Link to Full Text

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