What is surface mounting?

Simply talking surface mounting is a soldering technology where the component is soldered directly to a series of solder pads called a footprint. It is different soldering technology from through-hole, where component leads are inserted into holes of the board. The footprint is a series of pads that conform to the lead layout of packages of surface mount devices (SMD).

Surface mounting has several advantages over through-hole technology. First of all the board become much smaller. So smaller boards and more dense placement of elements reduce costs. Because of higher placement density, traces between components becomes shorter. It lowers parasitic inductance and capacitance.

The table shows the changes while redesigning the through-hole board to SMT. We can see the board size was reduced by 59%, the number of layers was reduced from 6 to 4, and the costs were cut in half.

Now everyday new components are introduced. Probably there is harder to find some components in DIP packages rather than SMD. Now you can find all passive elements in SMD packaging like resistors, inductors, capacitors, ICs, switches, crystals, relays, transformers.

So if you decided to use SMD components in your design, remember that most SMDs are designed for automated pick and place equipment, so hands cannot easily manipulate them. First, what you will be is a magnifying glass because most SMD is extremely small. Laying out and etching an SMD board is much like the same as a through-hole board. The biggest difference is that there are no holes in PCB.

Hold breath while placing the components on the board, and be sure you won’t sneeze. If so, you will have a hard time finding them. It is better to use some glue to stick them to the board before soldering. Use smaller tweezers to handle components, then Iron them with less heat metalized ends.

After soldering is done – clean the remaining flux and inspect the board with a magnifying glass. Have fun with SMD.