Electronics > PCB/EDA/CAD

Spacing between resistors/diodes/caps?

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Falcon69:
Hello all.

I am working on a new PCB design.  I have some 0603 LED's and 0603 resistors, also some Logic Gates on my circuit.  My question is, would 0.27mm (10.6mil) spacing between the pads be sufficient enough?  How close can I get?  The resistors will carry less than 63mW through them at 5volts or less.  Same goes for the Logic Gates and Inverters.

I am using DipTrace.

I'm trying to make this circuit board as small as I can.

Thanks in advance,

Jason

T3sl4co1l:
Need small?  Go 0402, and use arrays where possible (they're cheap, and come in 0.65mm or less pitch!).

10 mil is possible, but beware it may be trouble if it ever goes into production.  You may get problems with pick-and-place, paste placement, and reflow.  I think more like 20-30 mil (0.5-0.8mm) would be safer.  There should be IPCC rules/guidelines on it or something.

Tim

Falcon69:
Well, I'll be placing these myself.

I will switch to 0402.  But I can't do a network.  For one thing, 0402 154ohm (for example) is .003/5000, a network of the same is .076/2500.  Also, those small networks are 31mW per resistor. That won't be enough. A single 0402 is 100mW.  They will be harder to place, but, using those, I can get them arranged and be 0.47mm apart from each other. Better, but still not at the .5mm you suggested.

Tim, ipcc rules/guidelines...what is that?  If you mean the rules for routing that can be set in DipTrace, I don't run the auto router.  I trace everything manually.  The autorouter for diptrace sucks imo. Nothing is ever uniform, and I've seen it put vias, where vias were not needed.

T3sl4co1l:
Well, rules are still helpful in manual placement, depending on what features your tools have.  Checking for collision and clearance (live while placing, or at least periodically to check your work) is good medicine.

IPC-7351 (oops, not IPCC :P ) provides rules for surface mount design and process.

Tim

Falcon69:
Found this:

http://www.ami.ac.uk/courses/ami4945_dpb/restricted/u08/supplementary/sup_14.html

According to this chart, that .27mm will be good for a 0402. NOT for a 0603.

However, if I switch to 0402, I will actually have 0.47mm distance between pads I can work with.

The reason I ask is because I am trying to keep resistors and LED's in line with the dip switch.  If they are off center from the dip switch, It will be hard to determine which switch is lighting what LED on my circuit board.

I did learn something on my google search of IPC-7351, I need to fix my vias, it says recommended spacing from pad for a via is > 0.5mm.  I have less then that.

Jason

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