Few questions about SMD?

Question

I have an assignment but I can't find answers to a few questions though i tried a lot... can u pls help me?

1) What is the difference between hand soldering of through hole component and hand soldering of surface mounted devices?

2) Why is the wattage of soldering iron recommended as less? Give Reason.

3) Why it is not possible to develop PCB having only SMDs?

Answer 1

SMD/SMT Surface mounted devices or Surface mount technology.
1. Difference between hand soldering analog and digital devices on PC boards and SMD components on plasma etched boards are incredibly different. Capacitance or density is against SMD devices verses the sear size and density of analog and digital devices. SMD devices can not stand the heat from a regular soldering iron. That is why they do auto-insertion and machine spot welding on SMD technology.
2. I believe I answer part of the question as to why the wattage needs to be less if you intend to de-solder or solder SMT devices.
3. There are some components that are not invented yet to be used as SMD components and also current is the issue as well. Input power will exceed any SMD component, and have a thermal run-away. I have to have a wheat stone power supply to break down the operating voltage and current value. The pf capacitance is to low to deal with higher voltages and current inputs.

Answer 2

Ans,no.1,
Hand soldering in through hole components is easy as compare to surface mount devises, because in through hole component just put in their appropriate position and solder it .But for smd components is is very difficult to place their proper place and second thing their solder leg not enough big to solder it.There for some fluxwith stiky material come in market to fix it and than solder it.
Ans no.2, less wattege iron is recommended,due to components are sensitive to heat,if we solder with more wattege then it will either short or open the component.
ansno.3only smd's used inpcb design is difficult as due to these components place on surface &small chip hard to design.

Answer 3

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