2

How many mm should the clearance be between the A and B pads in the picture below?

And clearance between C pad and D pad?

And clearance between E pad and F track?

And clearance between F track and G track?

Voltage: let's assume 300 volts AC.

PCB: Let's assume coated,(standart settings in jlcpcb or pcbway)

Note: I randomly created the circuit so that I could ask my questions.

I need help with the importance of clearance here and how much it should be.

enter image description here

JYelton
  • 32,302
  • 33
  • 134
  • 249
johny adv
  • 55
  • 4
  • 2
    The distance between A and B is already small due to H1 ... follow the tracks via the fuses –  Oct 18 '21 at 20:18
  • 2
    Hey Johnny, if my answer [here](https://electronics.stackexchange.com/questions/590318/in-the-pcb-design-how-should-the-a2-terminal-island-of-a-triac-in-the-252-sheat) helped you, it would be great if you could up-vote it. If it answered [that] question, also click the checkmark. That's how this Q&A site works - useful answers are up-voted and the best are chosen as the answer. Thank you. – rdtsc Oct 18 '21 at 21:05
  • why do you have two fuses in parallel? I've never seen that, and it sounds like a bad idea! – Marcus Müller Oct 18 '21 at 23:07

1 Answers1

1

Electrical Clearance information can be found in IPC-2221.

For 300VAC rms (424V peak):
Condition B1 (internal conductors): 0.25mm minimum
Condition B4 (external conductors w/ permanent polymer coating): 0.8mm minimum
Condition A6 (external component leads, uncoated): 1.5mm minimum

Personally, I would double the IPC recommendations.

Clearance tables can be found on various Web sites.

If this is mains power, you'll need to check the various codes (UL, VDE, CSA, ...) where the equipment is used.

qrk
  • 7,474
  • 1
  • 5
  • 20
  • let's think about STP25N80K5 Mosfet.It has TO-220 package.This mosfet is an 800 volt mosfet.But the lead-spacing are about 1.7mm for pins of mosfet.Even more interesting is that the footprint spacing is 0.5 mm.So,Where is the IPC-2221 clearance rules? – johny adv Oct 21 '21 at 14:38
  • 1
    @johnyadv It would be ill advised to use a TO-220 package at 800V. The D2PAK or TO-247 would be suitable. Then why have a 800V part in a TO-220 package? You could be using this in a lower voltage circuit but the transistor should withstand the occasional voltage spike. – qrk Oct 21 '21 at 20:07
  • What about,How many volts can be used for a transistor in a to-220 package? – johny adv Oct 22 '21 at 17:17
  • And what categories do you think the l1,l2,l3 and l4 values in the picture belong to in the ipc 2221 table? https://i.stack.imgur.com/A2Fkv.png – johny adv Oct 22 '21 at 19:58
  • @johnyadv Traces on the PCB fall under "Bare Board" category. The TO-220 package falls under "Assembly" category, more specifically A6. If you want better PCB clearance for your TO-220 pads, use a triangle pattern. In IPC-2221, Table 6-1, there is a guide telling you what each category means below the table. – qrk Oct 22 '21 at 20:09
  • yes i read it now but i am not sure if i understood correctly.Can you confirm which category the l1,l2,l3 and l4 in this link belong to? https://i.stack.imgur.com/A2Fkv.png – johny adv Oct 23 '21 at 09:06
  • @johnyadv If you read paragraph 6.3.4, the traces that have solder mask covering the traces fall under category B4. However, the exposed (uncoated) pads and traces fall under B2 or B3 (depending on altitude). The component leads fall under A6. Mind you, IPC-2221 is a best practices guide. You can disregard the numbers and make the clearances smaller, but reliability will be compromised. As stated before, for 800V I would double the suggested clearances, mainly because products I design are used in dirty conditions. – qrk Oct 23 '21 at 18:39