Unpublished stackup details / RF performance of current cheap DIY PCB vendors?

[evb149]

Hi,

This is just a quick "poll" in case anyone has any particular tips to share about what recommended vendors / design options / characteristics they've discovered / learned about some of the currently better low cost DIY oriented PCB manufacturers.

I may do a few design runs that will in part be targeting 2.4GHz and +/- RF devices so my concern is of course getting the stackup related printed antenna (!) / microstrip / CPW / etc. trace design impedances dialed in as correctly as possible without having the guarantees of precisely specified PCB materials or stackup (absent from some/many vedors) controlled dielectric / controlled impedance processing.

If the vendor publishes easy to find and read (english) particular material datasheets and stackup geometry then of course I can just approximate based on that.  But IIRC several common cheap "front end" or pooling vendors are said to switch actual materials / stackups / fabrication factories now and then and not really specify what they're using hence my particular uncertainty.
Obviously better to avoid such vendors but price is a big factor at the moment so I'll see what PCBSHOPPER etc. leaves me with as lower cost but more optimal options..

I figured that some of you might have information like "Oh pooling / fabrication service X has lately been producing 2L or 4L PCBs with the following 'unpublished' measured characteristics or discovered stackup / materials ..." etc.

Also I'll probably be looking for some options for thinner 2L boards (0.8mm or less) to better suit smaller 50 ohm trace widths and provide better plane to trace coupling.

For 4L any currently cheap options that allow a thicker core with thinner inner plane ---> relatively thinner prepreg ---> external T/B trace layer would also be a good option for smaller lower impedance better shielded external layer traces though at the moment I am open to suggestions as to better alternative vendors wrt. cost / cheap and fast delivery time / good known stackup for RF and high speed stuff.  Yeah I know, cheap, good, fast, pick one / two...

Anyway I'll probably just end up guesstimating based on whatever info. I can find on their site or other sites but having more / better information never hurts!

PS I know for very short TLs and so on the differences won't be highly important but if I find enough information or cause to pick a particular vendor for present and many near term future options I'd be more likely to start sending them things that do depend much more on the material characteristics like PCB TLine based matching networks / filters / resonators etc.

Thanks if you have any notes / information / recommendations to share!