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Adhesiveless – Adhesiveless materials fall into 2 general categories – cast dielectric on copper and sputtered copper on dielectric film. These materials have gained popularity for several reasons. The absence of an adhesive layer results in a thinner, more flexible construction and in some cases the ability to manufacture flex using different techniques. Adhesiveless materials generally have superior electrical properties but that advantage is negated if an adhesive based coverlayer is applied.
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| A. Cast Dielectric – The manufacture of cast dielectric materials starts with .5, 1 or 2 oz. (rolled annealed or electro-deposited) copper and a thin layer of polyimide is cast onto the surface. It is available with copper on one or both sides of .001 or .002" polyimide. |
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| B. Sputtered Cu – Sputtered materials start with conventional .001 or .002" polyimide film. Angstrom thick copper is sputtered over a Ni-chrome or monel barrier layer. Copper is then plated to a thickness of 200 microinches. Sputtered adhesiveless material has a unique advantage in that it can be used in the manufacture of semi-additive circuits. |
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Adhesive Based – Adhesive based materials fall into two main categories, acrylic and epoxy.
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A. Cover Layers – Polyimide with acrylic or epoxy adhesive are the most common choices for coverlayer material. Polyimide thickness ranges from .0005" to .005" are available with .001 or .002" thickness as typical. Adhesive thickness is a function of circuit material thickness and is usually left to the discretion of the manufacturer. Photoimagable coverlayers (PIC) can be used in applications requiring high density access to circuit layer.
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| B. Stiffeners – Areas of a flex circuit can be stiffened for component attach, strain relief or mounting surfaces. Polyimide, Cirlex ® or FR-4 can be used to produce a range of flexibility or stiffness. Standard flex circuit adhesives or pressure sensitive adhesives can be used to provide varying performance alternatives. |
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C. Alternate Materials
Exotic and thick metal – Tech-Etch’s photo-etching experience gives us the ability to manufacture flex using a variety of conductor materials, including copper alloys, nickel, kovar, steel, and resistance alloys. Consult with engineering if you have specific requirements. |
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