The components are mounted onto the surface of the boards and this technology is known as surface-mount technology (SMT) and the components are known as surface mount devices (SMDs). SMT offers great deal with many important advantages during manufacture, and the use of SMT components enables far more electronics to be packed into a much smaller space and present in a compact mode.

THE NEED OF SMT
Electronic components can be divided into two categories:
1. Through-hole (TH)
2. And surface-mount (SM).

Through-hole are designed to be loaded on one side of a printed circuit board (PCB) and soldered on the other. Surface-mount components are loaded and soldered on the same side of the PCB. SMT is preferred over TH as there are many benefits using it:
1. SMT is faster for automatic machines to place.
2. SMT has a smaller physical size for the same electrical function.
3. SMT parts are cheaper than TH.

SIZE
To attain degree of uniformity, sizes of most SMT components conform to industry standards, many of which are JEDEC specifications. Obviously, different SMT packages are used for different types of components, but the fact that there are standards enables activities like PCB design to be simplified. The use of standard-size packages simplifies the manufacture because pick-and-place machines can use standard feed for the SMT components, considerably simplifying the manufacturing process and saving costs. SMT packages can be categorized by the type of component, and there are standard packages for each. The 0603 and 0402 are the most widely used SMT sizes. Diodes and transistors generally use a package called small outline transistor (SOT). Even though diodes have only two connections, these still use the same package. Having two leads on one side and one on the other enables the connections to be differentiated more easily.

USE OF SMT
SMT packages are used for most printed circuit designs. Although it is possible to use some SMT components for hobby construction, great care is required when soldering them. Additionally, even the ICs having wide pin spacing may be difficult to solder. Those with 50 or more pins cannot be soldered without using special equipment. These are intended only for large-scale manufacturing. Even when working on boards that have already been built, great care is needed. However, these SMT components offer great cost savings to manufacturers and this is why they have been adopted. SMT components can also be used for some home projects where they are applicable, where the SMT component leads and connections are not too small to manage with more traditional soldering irons and other tools.

THE PROCESS
Surface mount technology involves the following steps:
1. Design which comprises PCB design, which is conductor pattern design and
mounting pad design.

2. Parts and materials: Care and detailed knowledge of each item is required in the manufacturing of the parts.

3. Equipment: SMT employs eight different types of equipment in manufacturing process including solder printer, component mounted, soldering equipment, cleaning equipment, inspection equipment, reworking equipment and ancillary items like squeegee/metal mask.

4.Mounting: It includes solder supply, components mounting, soldering, cleaning, inspection and reworking.