Electronics Made Easy - a Complete Introduction to Electronics - Martin Denny [18]
6) Small crocodile clips
7) Flexible test lead probe with crossover claws
8) Set of screwdrivers, terminal posidrive and flathead
9) Set of needle files
10) Soldering Iron 15 to 25w or temperature controlled soldering station.
11) Solder sucker
Probably the two most important tools in the list are the soldering iron and side cutters. All the other tools can be acquired quite cheaply. The soldering iron should be as small as possible with a range of replaceable tips, a 15 Watts rated iron is usually adequate. A simple stand can be fabricated using a block of wood and a piece of metal coathanger.
Soldering stations which use a low voltage temperature controlled heating element are available but in my opinion are overly cumbersome and expensive.
Most standard side cutters are generally too large and not able to cut close to a joint. For electronics work the cutters must be small and made of high quality steel with preferably a spring release. These are best purchased from an electronics supplier.
1.3 Disposables
1) Multicore Solder (electronics grade 18 SWG)
2) Fine Wet or Dry abrasive paper or fine glass paper
3) Flux cleaning solvent
4) Spare soldering iron bits
5) Printed circuit board lacquer
Construction Methods
Small prototype circuits not using integrated circuits can sometimes be constructed using tagstrip, but this construction method is severely limited. For larger designs a printed circuit board or prototype board is necessary.
Printed Circuit Boards
Printed circuit boards (PCB’s) comprise of an insulating board usually fibreglass with a copper film bonded on one or both sides. The part of the copper film required to make connections ie tracks and pads will be coated with an etch resistant coat, then the PCB will be placed in an acid bath to remove unwanted copper. The resulting board can then be drilled to facilitate the assembly of components. In recent years PCB’s have been designed to incorporate surface mounted components which are mounted on top of the tracks without drilling, this facilitates the automatic production process.
Most PCB’s will be cleaned then passed across a solder bath to coat or tin the copper film. This makes soldering components to the PCB far easier and the joints more reliable.
Whether the board is single sided ie copper film on one face only, or double sided, the faces are defined as copper side and component side. Although both sides may contain copper track it follows that to prevent construction errors the component mounting side must be defined.
When designing a PCB layout most designers will treat the design as a single sided board until the number of links required on the component side reaches 5 or 6, above this point it is more economical to produce a double sided board, where small numbers of PCB’s are required.
Gone are the days when PCB layouts were produced using different sized sticky tape and pads stuck to clear plastic or tracing paper. Computer programs have been available for the past 15 years which will produce accurate PCB layouts which can be passed to the PCB manufacturer in digital form. Before attempting a layout please check with the local PCB manufacturer to find out which programs are compatible with his system.
There are PCB prototyping systems available which enable small quantities of PCB’s to be produced. The process is still relatively expensive and the resulting boards generally of poor quality, these systems are best avoided.
Due to the set up process the cost for a PCB manufacturer to produce a small number of PCB’s is very high. The break even point between using a prototype board and designing your own PCB is of the order of five to ten units ie find five to ten people who also wish to build the circuit.
2.2 Prototype Boards
Prototype boards are effectively general purpose PCB’s and are available from most electronic suppliers. The boards are constructed of an insulating material with a 1oz or 2oz copper film bonded to one or both sides of the PCB. The boards are drilled to take components on a 0.1 inch