Printed circuit boards (PCB) are of two types depending on their substrates – rigid printed circuit boards and flexible printed circuit boards.
Why Are Flexible Circuits Needed?
The PCBs of yesterday were mostly rigid. In this modern https://www.hemeixinpcb.com/rigid-flex-pcb/multilayer-flexible-pcb.html era of mobile technology where everybody is inching toward miniaturization, a need was felt for circuit boards that were lightweight, flexible, thin, small, and had high wiring density. Flexible printed circuit boards were invented to answer these requirements. These are printed boards that can be three-dimensionally wired and can be reshaped to fit available space.
What Are Flex Circuits?
A flexible PCB is made up of a flexible board, wirings provided on the flexible board, and connection pads to be conductive through wirings, which are provided on the edge of the flexible board. A copper foil is laminated to a resin substrate the layers and joined with adhesive or with the application of heat and pressure into an integral board. There can be more than one conductive layer for making circuitry on both sides. There are insulating layers, adhesive layers, and encapsulating layers between the conductive layers to ensure sufficient insulation. The plastic substrate of flexible printed circuit boards is formed of polyimide or similar thermoplastic material, such as polyetherimide.
The substrate is then coated with an adhesive and includes a cable with a plurality of embedded electrically conductive lines. Apertures may be formed in one of the insulation layers for electrical connection to other electronic components. Electronic devices are then connected to each other. In general, the front and rear surfaces of them are covered with insulating layers for preventing a wiring pattern from being conducted to other wiring pattern formed on other circuit board.
Six Step DIY Basic Flexible Printed Circuit Boards
* Take thin polyimide sheets that are copper plated on both sides. Cut the sheet into the required size. Ensure that the copper is not smudged and the edges of the sheet are not uneven, which can harm the printer later.
* Take a solid ink printer that prints in melted wax. Wax forms a layer on the copper that protects it later while etching.
Use Computer Aided Design (CAD) software to draw a diagram of your circuit.
* Use the printer to print this design on the polyimide sheet. The printed areas will come up as copper traces. Use dark, easily distinguishable colors, such as black or magenta.
* Soak the printed polyimide sheet in ferric chloride. We are now at the stage called etching, wherein ferric chloride is a copper etchant. It can take up to half an hour for the copper traces to dissolve and the polyimide to show up.
* The circuit is now ready for mounting. You can cut it into smaller circuits if needed or use it as it is. Holes are drilled with laser to mount electronic components. The circuit is now ready to solder.