Anatomy of a Copper Clad Laminate. Part I: Introduction

“A printed circuit board (PCB) mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched from copper sheets laminated onto a non-conductive substrate. PCBs can be single sided (one copper layer), double sided (two copper layers) or multi-layer (outer and inner layers).” [Wikipedia]

“FR-4 glass epoxy is the primary insulating substrate upon which the vast majority of rigid PCBs are produced. A thin layer of copper foil is laminated to one or both sides of an FR-4 panel. Circuitry interconnections are etched into copper layers to produce printed circuit boards.” [Wikipedia]

DP/19

DP/19

The materials needed for the manufacture of laminates are glass fabric (filler), epoxies (resin), solvent and copper foil.

Fibre-glass Cloth

“Glass cloth acts as the main structural reinforcement in most laminates. The rigidity and strength offered by glass compliments the binding, encapsulating and insulative properties of the epoxy resin.  The singular fibre-glass filament is the building block with which glass clothes are constructed. These thread-like fibres are put together to form a yarn or bundle. Subsequently, like weaving of any other type of cloth, numerous yarns are woven together in the manufacture of cloth. Various combination of filament and bundle diameters, filament counts and weave density, among other variables, will resist in a multiplicity of glass cloth thicknesses and weights. Finally, glass clothes are coated with a finish that facilities resin impregnation of and bonding to the cloth.”

ISOLA7628

Epoxy Resins

“The function of the resin is to act as a ‘glue’ to hold the laminate together. Epoxy resins can be purchased from various vendors at various steps of manufacture. Epoxy resin can be had in a liquid form so that it can be concocted to upstaged resin using proprietary recipes and processes.  It can also be purchased in the advanced or upstaged state, wherein the solid resin, complete with hardness and catalysts, is ready for use in treating.”

Copper Foils

“Most foils used in FR-4 manufacture are electrodeposited type foils. These are manufactured by plating copper onto slowly revolving drum-shaped cathodes that are partially immersed in the plating solution. As the drum revolves, the plated copper deposit is removed from the cathode drum at one continuous speed. Varying the drum speed and current density helps to vary the copper deposit and consequently, the resulting foil thickness.”

Post Processing

“At this stage, the ‘raw’ foil becomes available, which is then subjected to various processes designed to increase the roughness of the matte side, thereby increasing its mechanical adhesion to the substrate. In addition, the foil is coated with a micro-thin film of protective coating to prevent oxidation of the copper during lamination and storage.”

Copper

REFERENCES

Copper Clad Laminates

Understanding the PCB Laminate (ISOLA)

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