Flex circuit boards offer a high reliability replacement for cable and wire harness assemblies, while providing a significant cost savings without reducing your applications performance.
The Advantages of Using Flex PCBs
Flexible circuits have replaced hand-built wire harnesses in many applications. Because the track routing is determined by artworks, wiring errors are completely eliminated. Used in rigid flex combinations, the number of discrete interconnections in an electronic package is reduced: reliability engineers have often pointed out that when an electronic package of any type fails, it is usually at the point of interconnection. Standardisation and repeatability can be designed into the circuit. Electrical characteristics capacitance, impedance, and cross-talk are consistent from batch to batch.
- Packaging, reduced Weight and Space requirements :
The flat planar nature of flexible circuits, and the high track density achievable, offers considerable weight and space savings over traditional wire harnesses. Thickness can be as low as 0.004 inches (0.10mm), and weight reductions of over 75% have been achieved. Flex circuits have many packaging advantages. For example, unlike a rigid printed circuit board, which can only be positioned in two dimensions, flex circuits can be bent, twisted, and folded to utilize a 3rd dimension. This property can be utilized in complex and tight-fitting assemblies where it would be impossible to accommodate several rigid boards and harnesses.
- Surface Mount Technology :
Flexible circuits are particularly suited to surface mount technology (SMT) due to the ability of flex circuits to offer a strain-free bonding site for the SMT component. Thermo-mechanical fatigue due to thermal expansion is a chronic problem in bonding SMT devices to rigid PC boards. In flex circuits applications, the flexible base materials absorb the thermal stresses and thus decrease solder joint failure. In MIL-spec tests consisting of 1,000 thermal cycles from -55 to 125 deg C, flexible circuits showed no failures until 2,500 cycles while rigid boards failed after as little as 10 cycles. The light weight and compactness of flex circuits coupled with SMT makes them ideally suited to one another.
Flat conductors have a much greater surface to volume ratio than round wire. This extra surface area facilitates the dissipation of heat away from the circuit: heat is easily dissipated from both sides of the flexible circuits, the thin polyimide dielectric permitting a relatively easy thermal path. In rigid boards the dielectric substrate is a thermal insulator inhibiting the flow of heat, and this can be a reason to substitute using flex.
While other materials, such as flat ribbon cable, can be used where a limited number of flexures are required, only flexible circuits with correctly selected high elongation copper conductors have proven their worth as the primary method of providing reliable interconnection between moving parts, where millions of flexures are required.