Stiffeners are added to rigidize areas of a circuit to strain relieve component attachment locations, provide a firm surface for mounting, or increase thickness of the circuit to correspond to the mechanical specifications (e.g. ZIF connector).
Polyimide film is used when the additional thickness required is .002"-.009". Polyimide stiffeners can have coincidental edges to the circuit outline.
Cirlex ® is also used to produce a range of flexibility or stiffness. FR-4 is used when the additional thickness required is greater than .010". The stiffener features are typically smaller than the corresponding circuit features by .015".
Other materials such as metal or molded plastic components can also be used as stiffeners for specific design requirements. Standard flex circuit adhesives or pressure sensitive adhesives can be used to provide varying performance alternatives.
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, stainless steel, and resistance alloys. Consult with engineering if you have specific requirements. Stainless steel and BeCu circuits pictured below.
Stainless Steel Circuit