3 ms·

S1000-2 is quite cheap and lossy (Df 0.016), slightly better than Isola 370HR (0.021) but nowhere near the stuff I usually use. At my usual Chinese board house

S1000-2 is quite cheap and lossy (Df 0.016), slightly better than Isola 370HR (0.021) but nowhere near the stuff I usually use. At my usual Chinese board house it's one of the lowest cost substrates available for prototypes since it's always in stock and there's no need to special order. For higher end digital work I typically reach for Taiwan Union TU872SLK (Df 0.009) which also has a better range of prepregs and glass styles available to help minimize fiber weave effect. Still quite a bit lossier than e.g. RO4350B but far less expensive and if you have decent equalizers on your SERDES the difference is typically not significant unless you're making some kind of humongous backplane. I get wide open eyes with just a tiny bit of post-cursor emphasis on the TX FFE at 10.3125 Gbps on TU872SLK for my typical shortish high speed tracks (FPGA to SFP+ cage).

15155 2y ago
Curious who you are using in CN for higher-speed FPGA boards, if you can share! I haven't seen these as directly-advertised options at any of my usual suspects.
- azonenberg 2y ago
  Multech (multech-pcb.com) is my preferred manufacturer these days for high end stuff. I've done six layer HDI any-layer via stackups, ten layers with filled via-in-pad, RO4350B, TU872SLK, flex, 75 micron trace/space, etc. And that's nowhere near the limit of their capabilities, I just haven't needed higher end yet. I have some 25/100G stuff in the pipe for probably some time next year that I plan to make with them too. Their website undersells, I get the impression most of the actual sales contacts are word of mouth. I talk to my sales rep by skype mostly (the alternatives are expensive international phone calls or wechat). The really cool thing is that you get a 10+ page QA report with every order including measured copper/dielectric/soldermask thicknesses, hole sizes, ionic contamination measurements, and a ton of other metrics. And they send the TDR strips and polished cross section with every order as their way of saying "look, we actually did the QA, double check our measurements if you don't trust us". (I actually have repeated some of the measurements to spot-check and got results within a few percent of their QA department, no surprises there). And they don't make silent gerber changes or anything. They do a full CAM review and send you working gerbers and a list of suggested DFM tweaks for you to sign off before beginning manufacture. If something doesn't look right you have a chance to say "wait there's a problem". For example, one time they wanted to make a really large width adjustment for impedance on some RF traces that I had carefully modeled in an EM solver. But they didn't make a bad board without telling me, they flagged it on the CAM review and we went back and forth before realizing the mistake was on their end (they had calculated impedance assuming solder mask over the traces, while they were actually exposed copper). They re-ran the numbers which then closely matched my simulations, I signed off on the modified design, and the board was manufactured without issue.
buescher 2y ago
Also S1000-2 is not rated/controlled past 1GHz. It shouldn't vary that much so for small runs the risk is minimal. But for volume production that's exactly the sort of thing you never want to have to investigate in hindsight.

15155 2y ago

Curious who you are using in CN for higher-speed FPGA boards, if you can share! I haven't seen these as directly-advertised options at any of my usual suspects.

azonenberg 2y ago
Multech (multech-pcb.com) is my preferred manufacturer these days for high end stuff. I've done six layer HDI any-layer via stackups, ten layers with filled via-in-pad, RO4350B, TU872SLK, flex, 75 micron trace/space, etc. And that's nowhere near the limit of their capabilities, I just haven't needed higher end yet. I have some 25/100G stuff in the pipe for probably some time next year that I plan to make with them too. Their website undersells, I get the impression most of the actual sales contacts are word of mouth. I talk to my sales rep by skype mostly (the alternatives are expensive international phone calls or wechat). The really cool thing is that you get a 10+ page QA report with every order including measured copper/dielectric/soldermask thicknesses, hole sizes, ionic contamination measurements, and a ton of other metrics. And they send the TDR strips and polished cross section with every order as their way of saying "look, we actually did the QA, double check our measurements if you don't trust us". (I actually have repeated some of the measurements to spot-check and got results within a few percent of their QA department, no surprises there). And they don't make silent gerber changes or anything. They do a full CAM review and send you working gerbers and a list of suggested DFM tweaks for you to sign off before beginning manufacture. If something doesn't look right you have a chance to say "wait there's a problem". For example, one time they wanted to make a really large width adjustment for impedance on some RF traces that I had carefully modeled in an EM solver. But they didn't make a bad board without telling me, they flagged it on the CAM review and we went back and forth before realizing the mistake was on their end (they had calculated impedance assuming solder mask over the traces, while they were actually exposed copper). They re-ran the numbers which then closely matched my simulations, I signed off on the modified design, and the board was manufactured without issue.

buescher 2y ago

Also S1000-2 is not rated/controlled past 1GHz. It shouldn't vary that much so for small runs the risk is minimal. But for volume production that's exactly the sort of thing you never want to have to investigate in hindsight.