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Layer Stack for 6L PCB with 0.8 mm thickness

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#75360

Layer Stack for 6L PCB with 0.8 mm thickness | 16 February, 2016

We are designing board which have to plug in M.2 connector and thickness is limited to 0.8 mm

The board is very complex with many BGAs and DDR3 memory chips and we will need 6 layers for routing.

The problem is that we will need signals with 50, 90 and 100 ohm characteristic impedance and all calculations we make require less than 3.5-4 mils tracks/spaces to match the impedance. This will be expensive option.

I would love to hear if someone did something like this before and what layer stackup is used?

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#75361

Layer Stack for 6L PCB with 0.8 mm thickness | 16 February, 2016

When faced with a problem like this I sometimes look at competitive products and see what they have done. You may be able to get away with 4 layers if you have the space, however if it is jammed up that will not be an option. I presume that the total board thickness was 0.8mm. Reverse engineer an old memory stick with a random orbital sander. and photograph each layer this will quickly give you a workable stackup. 6 layers sounds unworkable if you wish to impedance match all your lines using microstrip.

regards sarason

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