Printed+Circuit++Board

Manufacturing PCB's
PCB stands for **P**rinted **C**ircuit **B**oard. PCB's can be found in many household appliances, some of which include televisions, mobile phones and washing machines, and even you iPod. PCB's are used in some many appliances as they are cheap and easy to make they also reduce the amount of wires and cables used in connecting components together, this also reduces the chances of the wires touching, which could cause an electric shock.

Mega UK has now added a 17 minute video which is excellent and recommended viewing before you have your PCB's made, please watch below: media type="custom" key="4087679"

A PCB is comprised of four different layers. The first, or top layer is a protective black plastic film which prevents the second layer becoming exposed to ultra violet (UV) light. The second layer is a photosensitive coating often called photo resist which softens when exposed to UV light. The third is a layer of copper. The last, or bottom layer, which holds the rigidity of the board, is made from GRP, which stands for glass reinforced plastic.

The first step is to design suitable artwork for your PCB, the best option is to design the circuit on a computer and print artwork onto a transparent acetate sheet using a good quality laser printer, (or print two copies on a bubble jet printer). The next step is to remove the protective film and place the artwork (transparent sheet) onto the exposed light sensitive board. You must be careful to place the artwork the correct way up, otherwise when the circuit is etched it is possible for the tracks to be the wrong way around. Once the transparent sheet is located correctly, place in a UV light box for 2.5 to 3 minutes. The board is then placed into a developer solution for about 30 - 40 seconds (sodium hydroxide) to remove the remainder of the photo sensitive layer exposing the copper beneath with the circuit imprinted on it. Thoroughly wash with water to remove any trace of developer solution. When ready, place into the bubble etch tank which is filled with ferric chloride solution and heated to about 45°C. Leave the PCB in the solution until all the copper has been eaten away with the exception of the designed circuit, leaving the copper tracks exposed.This should take about 15 to 45 minutes - if left in the bubble tanks too long the PCB's can become damaged. The PCB is removed and wash thoroughly, and a PCB eraser, or steel wool is carefully used to remove any remaining film from the tracks.

To produce the holes for the components to fit into the finished PCB, you must use a PCB drill fitted with a tungsten carbide bit. A normal drill is slow and inaccurate. You are now ready to start soldering your components in place.

Copper is used, as it is a very good conductor of electricity, The GRP layer at the bottom does not conduct electricity therefore removing the risk of an electric shock.

Health and Safety

 * Using the UV light box appropriately ensuring the lid is closed before exposure.
 * The chemical for the developer and etchant are hazardous, they are corrosive and an irritant
 * When using the developer and etching solutions, goggles, rubber gloves and aprons must be worn.
 * Handling the PCB's with plastic tongs.
 * work in a well ventilated room.
 * Wash the PCB's thoroughly, to ensure that there is no chemical residue left on the PCB's

Quality Control

 * The tracks are checked that they are cleaned of any photo resist film.
 * Under a magnifying glass the tracks are checked for continuity, and closeness.
 * Any gaps may be repaired using wire but usually a new PCB has to be made.
 * Drilling the holes has to be done carefully using a PCB drill, so as to leave the copper pads and track intact.

Click on the image to find the eight safe and economical steps to producing a PCB form Mega UK.

= Task = Using the above data complete the following worksheet to find out more about flowcharts: msc-ks4technology.wikispaces.com

Here are some YouTube videos about creating a printed circuit board, but some of the materials are not the same as those that we use here at school, but the principles are the same. media type="custom" key="2752455"

Check out the following page from V Ryans website [|www.technologystudent.com] And here is some info from the internet: media type="custom" key="2752705" = Industrial Practices = Here is a link to an excellent site that shows all the different industrial machines that are used in the mass manufacture of PCBs. And from that site are some PDF documents:
 * [|www.pcb.ddiglobal.com/ Services/pcb_fab.cfm]
 * [[file:PCB-Equipment-Showcase.pdf]]