DOUBLE-SIDED FLEX CIRCUITS
Double-sided flexible printed wiring contains two conductive layers with plated through-holes, with or without stiffeners (see Figure above). They can also be fabricated without plated through-holes, though the plated through-hole variation is more common. When constructed without plated through-holes and with connection features accessible from only one side, the circuit is defined as a Type 5 according to military specifications. It is not a common practice, but it is an option.
Because of the plated through-hole, terminations for electronic components are provided on both sides of the circuit, allowing components to be placed on either side. Depending on design requirements, double-sided flex circuits can be fabricated with protective coverlayers on one, both or neither side of the completed circuit. While possible, omission of a protective cover film or coating for the circuits rarely occurs.
Double-sided flexible PCB can be divided into 4 categories according to plated holes and coverlayer:
- With PTH and coverlayer
- Without PTH or coverlayer
- With coverlayer, without PTH
- With PTH, without coverlayer
Double sided flex pcb without cover layer is seldom used
Double-Sided Flexible PCB Features:
- Two conductive layers
- Component assembly available on both sides
- Fingers are an integral part of the conductor patterns