Printed Circuit Board (PCB) Assembly Tips
A Printed Circuit Board (PCB) is a flat piece of metal or plastic, which is mounted with computer chips and connectors. These are used inside electrical appliance like computers, digital cameras and television.
Irrespective of the fact as to what materials are used, the generic standard for printed circuit board is IPC-2221A which has defined the rules for quality of material properties, surface plating, thickness of the conductor, placement of components and tolerance rules. But at the end of the day, no standard can tell you how to design a printed circuit board effectively. You will have to understand and implement many concepts including basic concepts like circuit operation and advanced concepts like coupling of signals across circuits, radio transmission and much more.
To build an electronic circuit, the various types of circuit board available. The three most common types of circuit boards available are:
- Bread Board: can be used to make temporary circuits for testing or trying out new ideas. No soldering is required and all components can be reused.
- Strip Board: has copper strips running parallel to each other. These strips can be used as a crude replacements to PCB in case of emergency or testing purposes.
- Printed Circuit Board: have copper strips running along the holes where the components are connected. These are designed specifically for a circuit with a lot of planning and optimization. Special equipment are required to make a printed circuit board and these are generally used for mass production of a product. You will also need a soldering iron to solder each component into its respective hole.
Tips on Printed Circuit Board Assembly
The entire process of producing printed circuit boards is known as circuit board assembly. Some of the tips that you should use while assembling your PCB are:
- Reserve space in the top corner of the board to mark the assembly name, the part number and the revision name if any.
- A surface mount assemble is preferable over a thru-hole assembly as it helps increase accuracy and quality and also works out far cheaper.
- Ensure efficient use of panels which will help you reduce cost of boards, components and process time.
- In some cases you may have to consider placing the components on both sides of the board. This may see to be a feasible solution, but it is important to remember that the cost of the assembly will increase.
- Components should be oriented in the same direction and should be spaced out evenly on the board, else the placement and the inspection process becomes very complex and tiresome.
- Attention should be given to height relationships when placing the components. For example, placing a chip between two high connectors can turn out to be pretty difficult.
- Although it may seem tiresome, trace routing to prevent any acid pockets that may rise during the fabrication process.
- Pre-coated positive photo resist fiberglass board (FR4) of a good quality should be used.
- Too much heat while soldering the components can actually damage the board and the components. The heat handling capacity basically depends on the width of the cross-section of the board. Look up the allowed wattage for the board that you are assembling on before you begin.
- Symmetrical routing should be used for parallel power devices.
- Decoupling is an expensive process which is used when voltage regulation is not feasible and should be used only in critical applications.
- Maximum thought should be given to all power and grounding tips during the design phase and it should be implemented all the way during the assembly process.
- Sockets on surface mounted PCB are expensive and should be used only on prototypes and not in production.
- Precaution should be taken when you are working with PCB that are directly connected to power plug points.
