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Are there any standard component clearance guidelines/rules/best practices (for SMD parts)? Or does one have to talk to the EMS every time for all the components' clearance?

For example how close can two 0402 be to each other?

How close can you put an 0402 or a crystal to a BGA?

How close can you put an 0402 to the edge of the board, etc.?

Are there any "default," commonly used rules one can use?

JYelton
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mr dude
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    The maximum component density in part depends upon the amount of heat generated by your circuit. Since circuits can vary quite a bit in their heat generation, the answer will depend on the specifics of the circuit. – Math Keeps Me Busy Oct 17 '23 at 23:32

2 Answers2

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Every single of your questions depend on which components you place, carrying which current, being exposed to which voltages, at which frequencies, and being near which signals being used by which circuitry.

Sure, there's limits on how accurately a pick and place machine can work. These are rarely the limits of how closely you pack components.

So, no, you don't talk to the EMS all the time when designing a board – you talk to yourself (or colleagues) and figure out what the physical limits on placement actually are – that might be

  • geometry dictated by the fact that you're not placing components on the board for fun, but to fulfill a specific purpose. For example, a 90Ω differential microstrip line has a specific distance between the two conductors. When you add AC coupling capacitors to these lines, it's not the components that limit your spacing - it's the physics of transmission lines.
  • creepage distances or clearances due to high voltage needing to be handled safely (and what these are depends on the voltages, the operating conditions, the safety requirements and the targeted reliability)
  • signal integrity considerations: place a high \$\frac{\mathrm d}{\mathrm dt} i(t)\$ line of your SMPS parallel and close to your sensitive analog signal line for long enough, and you've built a transformer for noise coming from the former to the latter. That of course also works with power inductors and signal capacitors, for example.
  • thermal considerations might say that your resistor can be cooled well enough through the board if there's not too much heat dissipated by surrounding components. You can't thus put it close to your power transistor, but very close to your other transistor that doesn't dissipate much power in your application

These couple of examples serve to illustrate that you need to understand what you are making a component do, and only from that can derive distance bounds.

Marcus Müller
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  • But if you need to lets say position to low voltage (lets say fornets of 1.5v, simple DC) 0402 cap between each other. what are the limitations? becuase it is not heat and it is not eletrical. so how then do I decide the values in the rules in Altium or any other CAD software for clerance checking? no standard clearence values exist? – mr dude Oct 18 '23 at 06:52
  • Sure, there's standards for courtyards. You've gotten another answer about that already. – Marcus Müller Oct 18 '23 at 09:25
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IPC-7351 gives courtyard dimensions for many components. There used to be a Mentor product called "LP Viewer" which showed data for various components, but it looks like Siemens rolled that in to PADS.

qrk
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  • Not really looking for component dimensions but more physical limitations. like how close can a pick and place position etc. – mr dude Oct 18 '23 at 06:50
  • @mrdude "Courtyard dimensions" are just that. When we have questions about tricky placement, we call or visit the assembly houses. – qrk Oct 18 '23 at 12:51