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A Brief Guide to Flexible Circuit Boards
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 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 the flexible circuit board 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.
Flex PCBs are simple to make and versatile in use. However, sophisticated equipment requires top-quality PCBs that will hold together for a long time. The right material, right drill, and technical expertise make all the difference. Therefore, entrust the job only to an expert.
About the Author
Visit the given link for more information about flex printed circuit boards and flex PCB circuits. We offer high-quality flexible circuit boards of all types at competitive prices for prototypes to large volume production Flexible PCBs.
How do you mount a 20W LED 1000 LM LUMEN ENERGY SAVING POWER LAMP into a circuit?
I only have the 20W led. I want to know if there's anything special besides a transformer and 2 wires to light it up..?
If it is 20W for 1000 Lumen then it is 50 lumen per watt - about the same as fluorescent lamps (50-100lm/W).
The first link shows one type, limited data found, but note the comments on heat-sink issues.
The second link is a data sheet, showing one type that needs 12-15V @up to 1.4A. The biggest issue is temperature. Surprisingly there is no thermal resistance spec. However the Tjmax (max junction temperature) is 120C, so allowing that we don't want it that high, if the ambient is 50C and the Tj is 100C, that means 50C rise is allowable, and that means an overall thermal resistance of 1 degree C/W, including whatever the junction to case is. A heat-sink with 1C/W on its own is a large multi-finned thing about 150 x 150 x 50mm, so this LED needs something like that with a fan, to run at full power. The connecting leads are apparently also the heat-sink (thermal) connections, so you will need to devise a way of splitting and insulating the heat-sink, so the electrical connections can be made while the heat is also conducted away. The heat-sink will be close to boiling water without a fan, so no bits of plastic around. A fan is essential, unless the power (current) is less than the full power..
The driver circuit:
This will be a constant current supply that provides > 14V DC on no load, with the current limited and controlled to 1.4A or less, preferably adjustable. The voltage will pull down to the LED voltage when connected. It is definitely not a transformer, or the normal wall adaptor that produces a constant voltage. It will need a special device. I did find some Omron units (Farnell) but they were > $100 and rated for 24V so not sure they would even be suitable. However this is an indication of the price.
It would be possible to use a constant voltage 24V x 2A (using up to 1.4A) supply with a series resistor as the ballast. This resistor would be calculated using ohms law as (24V-12.8V) / 1.4A = 8 ohms so an 8.2 ohm power resistor using standard value. The power rating of the resistor would be V x I so about 16W. At least a 25W resistor size is needed so it won't get too hot. This method is wasteful, but it will work so you can see how hot it all gets. An old DC type power supply for a lap-top might suit this if the resistor is recalculated for the actual voiltages (could be 18V)
A true supply for this needs to be a switch mode regulator using an inductive ballast, running from 24V (derived from a wall outlet) and designed as a current regulator.
Tiny Slayer Exciter mounted on a circuit board.ASF
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