Impedance Control and Multiple Manufacturers

[mnpebm]

Greetings all,

If I make the choice to provide basic stackup and impedance needs to a given manufacturer, who then send me the specific geometries, what happens if I need to change manufacturers?

If what new manufacturer uses slightly different materials and processes, do I then need to change the Design Rules in my CAD Software to accommodate the new geometries?

Is there a way to make things generic enough?

Thanks in advance.
Mike

[robertferanec]

... who then send me the specific geometries...

Usually, you need to talk to your PCB manufacturer and sometimes it may take weeks to agree on a stackup.

... what happens if I need to change manufacturers? ...Is there a way to make things generic enough? ...

From my experience, if you get a stackup from a Chinese company, most of the other companies can make the PCB. Ask for standard materials. But you are right. There are companies what give you stackup from non-standard materials and then you need to re-define the stackup or you need to stick with them. So be careful.

Here are some ideas for the stackups which we use and can be manufactured by different PCB manufacturers: Download PCB Stackups – Free for your Projects >

If what new manufacturer uses slightly different materials and processes, do I then need to change the Design Rules in my CAD Software to accommodate the new geometries?

If your stackup is good, many manufactures can manufacture it with no changes - that should be the goal. If we notice, that there is a problem with manufacturing a PCB, we always update our documentation (you always want to be sure, that batches of your boards are always manufactured the exactly same way, otherwise you will not be able to guarantee quality - if every manufacturer adjust the PCB their way, your boards will be different between batches and may behave differently)

[mnpebm]

Very good. Just what I needed.

[koreshx]

Here are some ideas for the stackups which we use and can be manufactured by different PCB manufacturers: Download PCB Stackups – Free for your Projects >

I want to use file http://www.fedevel.com/welldoneblog/...4-6-Layers.pdf . As I understand L3 and L4 are symmetrical but L4 is not listed.
Can you explain what the difference between original and suggested geometery please?

I will try to modify this stackup using ICD stackup planner to improve density a bit.

[robertferanec]

Very good point. I think, in this case, L4 may be used for power planes, so L4 would be a reference plane for L3. martinmurin, please do you remember this stackup?

PS: Reference plane information is missing in the table, we should add that.

[JohnsonMiller]

In a project including DDR3 as well as SATA and some other standard (40 and 50 ohm), I asked for stack-up and final conclusion was that it is better to move from 1/2oz to 1oz, is there any comment? what we are missing and what is gain?

[robertferanec]

For signal layer it's not really important, but I think we normally use 1/2oz for signal layers, because that is what usually fits into our stackup to achieve the impedance and size we need. You may want to prefer to use thicker copper e.g. 1oz for power planes, because of possible higher currents.