Spacing between resistors/diodes/caps? - Page 1
Forum section: electronics / general

author: Falcon69
author_rank: Super Contributor
timestamp: March 27, 2014, 01:44:25 am
content: 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

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 27, 2014, 05:09:01 am
content: 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

author: Falcon69
author_rank: Super Contributor
timestamp: March 27, 2014, 04:08:08 pm
content: 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.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 28, 2014, 12:52:44 am
content: 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) provides rules for surface mount design and process.Tim

author: Falcon69
author_rank: Super Contributor
timestamp: March 28, 2014, 02:10:16 am
content: Found this:http://www.ami.ac.uk/courses/ami4945_dpb/restricted/u08/supplementary/sup_14.htmlAccording 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

author: Dago
author_rank: Frequent Contributor
timestamp: March 28, 2014, 08:11:14 am
content: Quote from: T3sl4co1l on March 28, 2014, 12:52:44 amI also suggest looking in to the IPC-7351 standard which specifies a "courtyard" (not sure if that was the term used in the standard) for the footprints which is the are which should not have tracks or pads from different nets in it.

author: ConKbot
author_rank: Super Contributor
timestamp: March 31, 2014, 11:52:32 am
content: Quote from: Falcon69 on March 27, 2014, 04:08:08 pmHow thick are your tweezer tips? I'd suggest not going narrower then that