MATERIALS: The basic ingredients of a copper clad laminate are:
FILLER: Fillers are incessant webs of materials like paper, glass, cloth, etc. And are used as reinforcing agents. The papers used are craft, alpha cellulose, rag or their combinations. The vast majority of printed circuits are made with paper based laminates are these are low prize and have easy mach inability. Amongst various papers, the rag paper provides an electrically better laminate that the one made of alpha cellulose paper. The glass filler is generally in the form of cloth woven of filaments. Glass cloth gives a laminate with a very high mechanical strength and very low moisture absorption when epoxies are used as a matrix.
RESIN: The filler described the above are embedded in a matrix of a resin laminated. Most extensively used among all the matrix materials are the phenol-formaldehyde resins. Long experience with these has lead to an almost perfect understanding to their behaviour. Epoxies, which are comparatively recent, are much costlier but they exhibits superior electrical and mechanical properties which are retained under hot and humid conditions. Polyesters, too, have good electrical and mechanical properties but they have restricted with respect to the type of filler applied. They also have a small chemical resistance.
COPPER FOIL: The copper foil which creates the surface of a copper-clad laminate is produced by the procedure of electro-deposition. A thin film of copper metal is deposited onto a slowly rotating corrosion resistance metal cylinder, whose lower portion is immersed in a copper rich electrolytic plating bath. As the cylinder slowly rotates in the bath, a thin copper deposited gradually builds up into an integral sheet of metal foil which can be gently peeled off from the cylinder surface at the point where the cylinder surface comes out of the plating bath. The rolls of foil, as separated from the plating machine, are generally known as raw foil. Further process steps are applied to both surface of the raw material foil in highly proprietary processes which increases the potential bond strength of that surface of the foil.