Working with SMDs will be a new experience for most engineers, hobbyists and constructors. By following the special yet simple handling and constructional techniques explained here most people will find SMDs easy to work with. A small work table is adequate, with a little space to store tools.

It is assumed that the constructor is familiar with the conventional ways of assembling circuits. So the emphasis is on the special equipment and techniques associated with working with SMDs. It is also assumed that the reader is new to this field and wants to find out as much as possible about SMT with the minimum of investment in books and equipment. As one reads on, the descriptions will make clear that the beginner needs very little special equipment, and the relevant skills are easily acquired.

Many SMDs do not have any marking to identify them; especially in the case of chip capacitors. Do not remove them from their sealed and labelled packets until you are ready to solder them.

The soldering iron is the item of equipment to which most attention must be given. The iron needs to be light and easy to handle and to have a fine bit. A 0.5mm bit is ideal but difficult to come by. It is, however, possible to solder satisfactorily with a bit up to 2mm diameter. To avoid danger of overheating the components, use a low wattage iron (18W or less)

The solder provided in our trainer kits is of 26SWG which is a very fine gauge and very good for soldering SMDs. The tin/lead ratio is 63/37 which has a melting point around 180° C; thus minimising overheating of components. The solder wire is flux cored.

A clean bit is essential, especially when soldering SMDs. A shallow tray holding a damp sponge is used for wiping the bit clean. Make it a habit of cleaning the bit often. Remember that the bit gets a little cool when dipped in the sponge; wait a few moments for the iron to heat the bit again and only then continue soldering.

A pair of fine-tipped bent-end tweezers is a very useful tool for picking and placing the SMDs on to the surface of the PCB, and to hold them in position when soldering.

The next essential item is a low-power magnifying glass of 3 or 4 inch diameter, with a magnification of about 4 times; with its own stand to allow your hands to be free. In addition to this, a high-power magnifier will be very useful to inspect PCBs for possible faults in soldered joints, pads or tracks. A watchmaker’s eyeglass with 8 to 10 times magnification will be found adequate.

The problem faced by most assemblers of SMD populated PCBs is to hold the SMD in place during soldering.

There are a couple of solutions to this...

• The SMD should be glued on to the PCB making it easy to solder. Clear nail polish, used by ladies on their finger nails, is a very good glue. Using a pin put a tiny dot of this nail polish on the PCB between the pads and put the component in place. It dries in a few moments holding the SMD in place for soldering.

Other tools and instruments you will need are...

A wire cutter, miniature long-nosed pliers, and a set of small screwdrivers. A multimeter, (digital multimeters have become very cheap and it is worth considering buying one), preferably with a built-in continuity checker and diode tester. The probes may need to be file down to fine points for testing SMT circuits. A set of trimming tools.