By Mark Thompson | Published on: October 14, 2013
The lamination process bonds the cores and foils together with pre-preg or “b-stage” materials under heat and pressure. Once the pre-preg material reaches its Tg (glass transition temperature) and it becomes gelatinous, it needs a pathway to flow off the edges of the panel and distribute evenly across the surface of the layer.
Traditionally, fabricator’s such as Prototron add a “dot pattern” around the parts on the panel which is a series of offset dots in metal that allows a web path for the pre-preg to flow. This worked well when dielectrics of cores were .008 or thicker as they are not dependant on the configuration of the layer itself (plane, split plane, or signal) to add inherent stability to the layer. On thinner cores (.005 and below) we now add what is better known as a “starburst” type flow pattern. This still provides a path to move the pre-preg to the panel edges but also adds additional metal rigidity for the thinner cores that tend to move more through lamination. Each subsequent layer needs to have either the dot pattern or starburst pattern offset so that the metal “dots” do not reside over the top of each other when stacked.
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