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PCB Design good practices

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sandbox

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Hi all,

I am designing a circuit board for a batch of 10000 boards, I have a few questions about good practices in PCB design, mostly pertaining to reliability and manufacturability. It would be really helpful if you could give me advice or direct me to any resources .

The first 3 are related to via's and PCB design :

  1. How reliable are via's , from a manufacturing standpoint do you end up with a lot of failed via's or are they generally reliable ?
  2. On the same note if you can route a short trace with a via and a longer trace without one, which one should be preferred ?
  3. i have a via as shown in the picture below, is that a good practice to have a junction at a via?


Screen shot 2013-01-01 at 6.50.18 AM.png

These questions below are related to mass production :

  1. How should I choose the material of the PCB ? considering its properties and eco friendliness ?
  2. How should I choose the thickness of the PCB?
  3. How much extra stock should I order considering some PCB's might fail, for example if i need to produce 100 boards how many more should I order as buffer to account for improperly produced ones?
  4. How do i optimize boards for pick and place assembly?

Please help me out
Thanks in advance,
sandbox
 
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sandbox

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Thanks ! will go through the material posted on the mentioned thread, but it seems its all about PCB design, is there anything similar for PCB manufacturing and mass production?
 

mtwieg

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Consider that modern motherboards have thousands of vias, each of which is presumably vital to its function, so obviously they can be very reliable. When you really need good reliability, you generally either have to either do post manufacturing verification (mass E-testing) or do some special manufacturing specs (plugging, extra plating, etc).

I would only consider vias a risk if they have to conduct a great deal of current (amps or more), and then you just put lots of vias in parallel to deal with that.
 

sandbox

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@mt weig,

I am not transmitting a lot of current, all under 100mA on 8 mil mil traces, would i need multiple via's for that?

@tpetar

I will be looking around for fab houses that offer xray inspection, is it an expensive process?

- - - Updated - - -

@mt weig,

I am not transmitting a lot of current, all under 100mA on 8 mil mil traces, would i need multiple via's for that?

@tpetar

I will be looking around for fab houses that offer xray inspection, is it an expensive process?
 

Ow@i$

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as long as you can route a net without making loop and breaking other rules of designing don't use vias.. but generally in big design you have to have vias in order to have connections on different layers... sure they are reliable , however reliability depends upon perfectly the manufacturer is working with them
 

cyberrat

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Hi all,

I am designing a circuit board for a batch of 10000 boards, I have a few questions about good practices in PCB design, mostly pertaining to reliability and manufacturability. It would be really helpful if you could give me advice or direct me to any resources .

The first 3 are related to via's and PCB design :

  1. How reliable are via's , from a manufacturing standpoint do you end up with a lot of failed via's or are they generally reliable ?
  2. On the same note if you can route a short trace with a via and a longer trace without one, which one should be preferred ?
  3. i have a via as shown in the picture below, is that a good practice to have a junction at a via?
1) Very - if you use a reputable manufacturer
2) No via and no loop is preferred, however for a small insignificant signal then a via may be best as it might also allow other routes to be placed.
3) In general there is no problem with it, but it depends upon what signals are on that route - I would not do this on a data bus or clock signal.


View attachment 85048
These questions below are related to mass production :

  1. How should I choose the material of the PCB ? considering its properties and eco friendliness ?
  2. How should I choose the thickness of the PCB?
  3. How much extra stock should I order considering some PCB's might fail, for example if i need to produce 100 boards how many more should I order as buffer to account for improperly produced ones?
  4. How do i optimize boards for pick and place assembly?

Please help me out
1) Cost - electrical requirements - unless it MUST be anything else FR4 is the most common but the paper ones are the cheapest (and crappiest).
2) Mechanical requirements - cost - unless it MUST be anything else 1.6mm is the most common and cheapest.
3) Send your manufacturer a netlist with your data (if not using ODB++) and specify that you will not accept any faulty boards - they must all be electrically tested. Then on a batch of 100 about 2 should suffice.
4) Do this from the outset, when you place your components on the board, when you decide the board size, when you specify the panel for your manufacturer. Discuss it with assembly depts at all stages of the design before moving to another and certainly before sending the data to be made.
 

sandbox

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Thank you very much for all the helpful suggestions ! I im talking with my manufacturer to get things in order.
 

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