10-03-2019 07:13 AM
The design files of kc705 evaluation board show that the material of PCB core is NELCO 4000-13EP SI. But I don't find any descriptions to illustrate the material of pre-preg.
So I want to know what material is used as pre-preg.
In addition, what's the unit of the thickness of board 0.062" ?
10-03-2019 09:28 AM
Ive not seen that doc before,
but it does seem to be broken ,
look at the top copper, its direct onto a pre preg.
this sort of implies they made the copper without a core, and aligned it to the layer below !
Sort of wrong ..
10-03-2019 10:32 PM
10-03-2019 11:54 PM
Is that the picture of the structure you posted,
If so , its wrong due to the comment above.
10-04-2019 12:15 AM
10-04-2019 12:41 AM
0.062" has units. ["] means inches. Also expressed as 62 mil (mili inches) and is about 1.5 - 1.6 mm, the standard thickness for a PCB
10-04-2019 12:47 AM
You are lucky for having so many details. You can work out the prepreg details with the specified impedance.
If you use Altium Designer, for example, you can set up a layer stack as that one and specify copper thicknesses and core thicknesses and material (epsilon, the dielectric constant). Then you specify impedances on different layers to match those in the doc. Then you try different dielectric materials and thicknesses to match everything (even total thickness)
10-04-2019 12:56 AM
Agree with your quesotion about what pre preg, sorry I dont have answer to that,
as others say , you could reverse engineer the material properties to some degree off of the impedane and size given,
My question to you is more on lines of please talk to your PCB manufacturer,
I've seen alot of baords over 40 years, and I'm always willing to learn , but I have not seen foil directly attatched directly to pre preg,
prepreg is horrible "gungey" stuff, more akine to hunney than a board. It sticks like babies output to nappies... !!
the foil has to be etched and drilled, and I cna not see a sheet thinner than aluminium kitchen foil being etched and drilled on a pre preg backing.
Pleae let us have more details , but I don't think even laser cutting would work in this situation,
I have only ever seen copper on core material.
which is why your layer stacke layer is normaly
10-04-2019 01:48 AM
Thank you for replying the second question! About the first question, I will try what you said. I think there should be some fixed compositions of lamination & prepreg materials when use NELCO 4000-13EP SI as PCB core. I really want to know what materials is used as adhesive when using NELCO 4000-13EP SI as PCB core? By the way, what do you mean about "lucky"? I just download a zip file from xilinx official website for free named as XTP133 in which there is a PDF file that depict the KC705 PCB layout information and stack structure.
10-04-2019 02:05 AM
10-04-2019 02:26 AM
With "lucky" I meant that such PCB details are not frequently available. Actually... cloning that PCB is not much useful, you probably won't make it cheaper, so they are safe in that sense. Also, Xilinx's business is not making and selling dev boards.
10-04-2019 02:39 AM
10-04-2019 02:40 AM
I stand amazed,
thank you , as I said I'm always open to learn, technology of PCB's has moved on ..