A mobile phone circuit & normal circuit both are parallel same but little different in there are normally PCB (printed circuit board)& every component which are fitted in normal PCB all are fixed with in whole also its always single layer pcb means one side we can fit the by pushing component leg in pcb & fix it opposite side by solder wire ,But mobile phone circuit are multilayer, and the mobile phone components are different from the general component those components are known as SMD (surface mount device) . They can be mounted of the surface of the PCB,
The surface mount device means the components mount on the surface only. The component which those soldered that is called PCB; it’s also had multiple layers. That’s why it’s called multi-layer PCB, every mobile phone pcb are multiplayer pcb. Now clear defiance between PCB and PBA.
Before the install any components its call PCB (printed circuit Board).After install components it’s called PBA (printed board assembly)
Te technique of utilizing SMD components it’s called SMT (Surface Mount Technology), smd type are components use for several resign like low wait , saving space the size of mobile phone has been significantly reduced due to using smd components . It’s also consuming low current & working low voltage, the voltage loss of this components are very low.