The 2 main type of PCB Assembly process is between : Surface mount (SMT) components, whose terminations are soldered to the pads on the surface
of the PCB, and Through-hole components, whose terminations are inserted through holes into the
interconnecting PCB, and soldered on the opposite side of the board from the component, The choice and mix of components will determine which assembly sequence and processes are
used. SMT Assembly 1. Solder paste is applied to PCB via solder paste stencil.
2. SMT components are placed on to the solder paste deposit, where the component will be held by the ‘tack’ of the paste.
3. Heat is then applied by way of reflow solder to form the solder paste into permanent
joint with the component.
4. During reflow soldering, surface tension on solder will always self align the component
to its correct center location. Through-hole Assembly 1. Through-hole components are bent and formed where necessary. 2. Components are inserted on to the board. When components are properly formed, it will prevent movement during handling and soldering process. Sometimes retention jigs
may be used to hold the components in place during soldering 3. Molten solder is applied to termination legs of the through hole component by way of either wave soldering process or manual soldering process. (type of soldering process
will be determine by type and mix of components) 4. Excess termination legs on the component is removed by cutting. Silvtronics uses ultrasonic cleaning to clean the completed assembled PCB to remove all flux
residues. Final board will be put through a detail visual inspection to ensure proper component placement
and good solder joint. | 
