2
\$\begingroup\$

I have completed my schematic design and started PCB layout. I am considering two layers and 45 mm x 95 mm. There are not any critical signals and according to current values of nets, I will draw power nets with 40 mils and 12 mils for others.

My desired board size is indicated at the bottom-left side of the image below. Do you think that this size is enough for these components? Thank you for sharing your ideas. I am trying to put it as at most 2 layers because of the cost of 4 layers is much higher than relative 2 layer board.

This is the layout;

enter image description here

\$\endgroup\$
  • 5
    \$\begingroup\$ What's the total area of all of the components (their outline)? What is the area of the PCB? A rule of thumb would be that PCB size is total components area + 20-30% to have a not-that-dense layout. \$\endgroup\$ – Eugene Sh. Aug 8 '17 at 18:13
  • 4
    \$\begingroup\$ I can tell you how we were doing it once. We have taken the physical components and measured them with a caliper :) \$\endgroup\$ – Eugene Sh. Aug 8 '17 at 18:22
  • 5
    \$\begingroup\$ On a 2-layer board you will want to allow more than 30% extra area beyond what the components themselves fill. Also, 12 mil tracks are very wide for signals. Most fabs have no issue with 4 mil nowadays. Maybe use 6 mil if you want to really good yield. \$\endgroup\$ – The Photon Aug 8 '17 at 18:43
  • 3
    \$\begingroup\$ Also, what size components are you using? If that long edge is 100 mm, I guess you must be using 0805 and larger parts. Smaller sizes will really hep you meet your size target. \$\endgroup\$ – The Photon Aug 8 '17 at 18:45
  • 1
    \$\begingroup\$ You don't indicate that the pcb size must remain at 45x95. Maybe you don't need to stress over this limitation yet. Start grouping components, and placing them in sections (based off your schematic). Then start squeezing the groups together to get a better idea of how much room they will take up. Can you place on both sides of the PCB? It's sometimes amazing how well the components compact. It's sometimes infuriating how much they don't. Good luck. \$\endgroup\$ – Chris Knudsen Aug 8 '17 at 18:46
2
\$\begingroup\$

The first thing would be to add up all of the areas (or group them in altium) and see what area they take up, your board needs to be bigger than this area.

You also need to account for via's and traces, I'd add 20% to 40% of the component area but this is what I do, and is design dependent. Remember that the time it takes you to route is also a cost, and on low quantity boards it might not save you any money to make the board smaller.

The last thing would be to remember that if you want a silkscreen with printed reference designators, this will take some additional room (although not much because you can print this over traces.)

\$\endgroup\$
  • \$\begingroup\$ Thank you. I will drop some components from schematic and also increase the board size. \$\endgroup\$ – layout789 Aug 9 '17 at 5:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.