OSHPARK PCB Manufacturer - Page 1
Forum section: electronics / general

author: xzswq21
author_rank: Frequent Contributor
timestamp: January 31, 2018, 01:58:32 pm
content: HelloI'm designing a high speed PCB. I askedOSHPARK.comthat do you control the impedance?they answered me we haveIsola FR408material but we don't have impedance control option and if you want to have 50 Ohm or 100 Ohm impedance you should calculate the width and other spec using a PCB toolkit.is it enough? or it's necessary to measure the impedance?all the impedance should be 50 Ohm +/- %5 @ 2GHz and 100 Ohm +-%10 @ 2gHz.Thanks

author: xzswq21
author_rank: Frequent Contributor
timestamp: January 31, 2018, 07:33:34 pm
content: Quote from: blueskull on January 31, 2018, 07:26:06 pmAll of I want is the impedance at 2GHz that should be 50 Ohm +-%5.I don't use Lead free solder paste bcoz it's a prototype high speed PCB for my thesis. I'm soldering at home using an oven, hot air, soldering iron station.I have some high speed ADC/DAC on my PCB.

author: Yansi
author_rank: Super Contributor
timestamp: January 31, 2018, 07:38:02 pm
content: Then stop bitching and whining and have it manufactured then. If you won't be satisfied with the Z0, then manufacure a corrected PCB o account for error measured.

author: xzswq21
author_rank: Frequent Contributor
timestamp: February 01, 2018, 09:48:19 am
content: Even Eurocircuits.com doesn't have impedance controlled process! they told me you should calculate the parameters. we only provide the stack-up information.

author: AndyC_772
author_rank: Super Contributor
timestamp: February 01, 2018, 11:13:16 am
content: Controlled impedance boards are not within the capabilities of the super-cheap prototyping shops that hobbyists use and talk about a lot. You'll need to find a proper PCB shop that will make up a panel according to your specification, and will test the end result and give you a report to show what impedance has been achieved.The bad news is that this will undoubtedly be *much* more expensive than an equivalent board from a Chinese prototype shop. The good news is that controlled impedance is a common requirement which most high quality PCB suppliers can do. Start by doing a search for PCB supplier in your own country, pick up the phone, and ask what they can do. I can virtually guarantee you'll find someone easily who can do it.

author: xzswq21
author_rank: Frequent Contributor
timestamp: February 01, 2018, 01:57:27 pm
content: Quote from: AndyC_772 on February 01, 2018, 11:13:16 amactually most of cheap Chinese manufacturers have impedance control option. but the material is a big question. I checked the Chinese material datasheet the dielectric coefficient has a big variation over the frequency up to 2GHz.

author: maginnovision
author_rank: Super Contributor
timestamp: February 02, 2018, 02:23:48 am
content: You could always try WellPCB.com I haven't used the option but impedence control is there. PCBWay.com also does. They are a chinese company. Either way expect to pay for it.

author: dcarr
author_rank: Regular Contributor
timestamp: February 02, 2018, 03:06:21 am
content: Don't discount OSHPark here. Their FR408 has a tight dielectric constant range and they have pretty good line width control.Download the Isola FR408 datasheet, plug in the numbers and the geometry below, add 0.002" to the line width to compensate for the etching process, and have your PCB made. I think you'll get +/-5% on the first try.http://wcalc.sourceforge.net/cgi-bin/microstrip.cgiI have a TDR setup that can measure impedance fairly accurately past 10GHz. I've been able to use OSHPark's 4 layer process in this manner with good results. However, don't use the 2 layer processes! The PCB material there has significant dielectric constant variance.David

author: xzswq21
author_rank: Frequent Contributor
timestamp: February 02, 2018, 06:06:55 am
content: Quote from: dcarr on February 02, 2018, 03:06:21 amI really appreciate you for you attentions and recommendationsif you see I'm a little sensitive bcoz I have some ultra low jitter clock and high speed ADC/DAC (200MHz) on my board, actually any big reflections disturb the quality of clock signal.I'm using Saturn PCB Toolkit and Polar Instrument to calculate the width and other spec. as you told I should add 2 mils to line width. Yes?

author: dcarr
author_rank: Regular Contributor
timestamp: February 02, 2018, 06:11:11 am
content: I can't say anything about the accuracy of the calculations from Saturn or other software, but yes in my experience the actual traces come out about 0.002" narrower than in my files.David

author: asmi
author_rank: Super Contributor
timestamp: February 03, 2018, 12:06:44 am
content: Quote from: blueskull on February 02, 2018, 06:20:13 amNot just me - darrel also posted his experience in my thread (he ordered 8 layer boards), and he seemed happy with the result. He also mentioned that he requested Iteq IT180 material which has very good frequency properties according todatasheet. They quoted me $140 for ten 10x10 cm boards 4 layers 0.1/0.1 mm traces, 0.2 mm min drills, ENIG and controlled impedance (+$30 shipping via DHL), I ended up ordering 6 layer boards with same specs for a little over $200 (shipping is again $30 extra).So while obviously not "$5 for 10" level of pricing, but I still think it's fairly cheap for the specs they have (darrel mentioned that he paid a bit over $300 for his order, while the same boards made in US would be $1800).

author: xzswq21
author_rank: Frequent Contributor
timestamp: February 03, 2018, 04:07:58 pm
content: Quote from: asmi on February 03, 2018, 12:06:44 amQuote from: blueskull on February 02, 2018, 06:20:13 amI really appreciate you for your answersyou can find summarized and useful information about the materials such as ISOLA FR408, standard FR4, IT180 and Rogers below:http://www.epectec.com/pcb/laminate-material.htmlI'm interested with sharing your experienceThanks

author: asmi
author_rank: Super Contributor
timestamp: February 03, 2018, 04:34:12 pm
content: I didn't specifically request any particular material for my boards, but they used ITEQ IT158 according to QA report. I didn't really have any important analog traces, but 5Gpbs USB 3 digital traces seem to work just fine, as do ~750 Mbps HDMI data traces and 400 MHz DDR3-800. This is more than good enough for my needs.

author: xzswq21
author_rank: Frequent Contributor
timestamp: February 03, 2018, 07:35:49 pm
content: Quote from: asmi on February 03, 2018, 04:34:12 pmDo you have their standard stack-up? I need the distances between layers for a 4-layer PCB (1.6mm thickness).I have heard most of 4-layer PCBs have 1mm of thickness. is it right?

author: asmi
author_rank: Super Contributor
timestamp: February 03, 2018, 11:08:23 pm
content: Quote from: xzswq21 on February 03, 2018, 07:35:49 pmThey don't have one - they can make whatever stackup you want. So you get to design one that fits your application best. That's their another advantage - they don't charge extra for custom stackup. Just make sure you use core/prepreg thickness that actually exist.

author: xzswq21
author_rank: Frequent Contributor
timestamp: February 04, 2018, 08:53:29 pm
content: Quote from: asmi on February 03, 2018, 11:08:23 pmAwesome!Thanksyou mean I can use 5 or 4 mils distance between the layers without any extra charge?! I have never seen such good manufacturerDo you have any pattern for LVDS vias? I'm using 10mils vias (10 mils diameter/20mils pad). I need Anti Pad size and Pitch to have 50 ohm impedance.did you order stencil for your PCB?

author: bson
author_rank: Unknown
timestamp: February 15, 2018, 06:15:57 am
content: Quote from: asmi on February 03, 2018, 11:08:23 pmAlso, realize that some asymmetric copper thickness stackups are very difficult to manufacture...https://signalhound.com/news/adventures-in-hardware-design-the-case-of-our-missing-20-ghz-spectrum-analyzer-the-sm200a/

author: xaxaxa
author_rank: Regular Contributor
timestamp: May 15, 2018, 04:44:22 am
content: jlcpcb seems to claim to do impedance control at no extra cost:http://club.szlcsc.com/article/details_11485_1.htmlNot sure if this applies only to orders on the chinese site or to jlcpcb as well.