How to choose Resistor and Capacitor SMD packaging sizes?

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dann11

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Hi! I am creating my BOM for a SMD project board.. I am trying to choose among SMD Resistors and Capacitors. And I will be using 1206 for the ease of assembly. But I am just wondering if it is really the primary reason for choosing a certain SMD packaging size. As I have also checked the internet, I've read the same reasons, for manufacturing purposes. But does it has any other effect in the circuit board aside for the assembly?
 

If you're hand placing the parts by hand, then 0805 or larger parts should be used. Careful, though, because a lot of manufacturers are discontinuing these larger sizes (but they still exist in the market). I find the 0805s to be easy to place by hand (and they are relatively cheap).

If you're machine placing, then the smaller parts are just fine, because they take up much less space and thus enable a smaller PCB.
 
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Hi,

For resistors: power dissipation, temperature rise, noise...

For capacitors: physical limitations in regard of dielectric type, voltage, capacitance...

Klaus
 
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For old timers like me, the first move from through-hole to SMD can be intimidating. I chose to go with 1206 for the same reason as with many others - ease of placement. Later on, I found that I could deal with smaller sizes too. So now I stock both 1206 and 0805 sizes.

Personally I don't have any pressing need to use 0603 and smaller sizes. On those rare occasions when I need to replace such parts on existing boards, there's usually a workaround. As KlausST mentioned, there are times when the larger sizes are needed for their higher power rating.
 
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First you have to see dissipation of resistors and voltage on capacitors;
second the possibility ( or the need ) to pass under the component with one or more traces
Third price of the components
fourth the availability of codified components on your company.


This is what we do.
 
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Price, the smaller parts are cheaper.
The draw back, shelf life. smaller parts have a shorter shelf life.
 
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