Investigation, analysis and determination of inclusions in high‐tolerance board design

This paper outlines the inclusions in laminates that can cause the false rejection in printed circuit board (PCB) manufacture. Laminate inclusions are now becoming prevalent because of the higher resolution required for the inspection of reduced track and gap widths. Visual methods have been used to identify four main types of inclusions; these are: tadpoles, resin burnt, metal, and others. Tadpoles have been identified for the first time, and are small black‐tailed formations. Metal inclusions contain three main metallic components: chromium, iron and titanium. The paper also outlines the possible sources of these inclusions. For tadpole inclusions, the paper discusses the use of Scanning Electron‐Microscope Energy Disperse X‐Ray analysis to identify their constituent elements. Other methods of analysis are also discussed, such as Fourier Transform Infra‐Red analysis.