Michael, A fab house only has to meet the specifications in the contract. I would say the company got what they specified. My point was that an impedance only specification is often inadequate. Aubrey On 1/5/12 1:16 PM, "Michael Greim" <mgreim001@xxxxxxxxx> wrote: >There needs to be an interlock between the fab house and >design team. If different construction methods are employed >and they aren't checked then offending engineer is really getting >what they deserve. Check twice, or more, and cut once is >a lesson often learned quite painfully. >-Michael > >On Thu, Jan 5, 2012 at 10:27 AM, Aubrey K Sparkman < >asparky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote: > >> Ken, >> >> What you say is true. What hasn't been mentioned is the risk behind >> specifying only the impedance. >> >> Mikhail makes a good point about specifying the board stackup >> CONSTRUCTION. I have seen failures when impedance only was specified. >> The design went out as a dual stripline with 4 mil cores between the >> signals and their respective reference planes and a 12 mil prepreg >>between >> the two signal layers. The pcb house was given permission to use 5 mil >> cores since they didn't have 4 mil cores in stock. For the 2nd build, >>the >> pcb house outsourced the design to another house which used 8 mil cores. >> Trace widths and prepreg thickness were adjusted appropriately so that >> both board thickness and impedance specifications were met. >> >> Any guesses about the performance of the boards in the 2nd build? >> >> Aubrey Sparkman >> SparkRight Solutions >> >> On 1/5/12 10:36 AM, "Ken Cantrell" <Ken.Cantrell@xxxxxxxxxxxxxxxx> >>wrote: >> >> >Mikhail, >> >I'm not disputing anything that you said, just pointing out that: >> >"If I, as a designer, know the process and materials used by the >> >particular >> >manufacturer >> >well enough" is a big If. That's a mature designer talking. Not >> >something >> >a relative beginner would know or even be able to accomplish. >> > >> >2cents >> >Ken >> > >> > -----Original Message----- >> >From: si-list-bounce@xxxxxxxxxxxxx >> >[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Mikhail Matusov >> >Sent: Thursday, January 05, 2012 9:05 AM >> >To: si-list@xxxxxxxxxxxxx >> >Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal >> >Board Production >> > >> > >> >I don't think those who responded understood the question correctly. I >> >think >> >the OP was asking whether some degree of impedance control can be >>achieved >> >by precisely specifying the board's stackup, width of the traces, and >> >process tolerances without explicitly asking the manufacturer to >>control >> >impedance. For some applications it just boils down to the cost. If I, >>as >> >a >> >designer, know the process and materials used by the particular >> >manufacturer >> >well enough I should be able to specify the board in such a way that >>the >> >impedance will end up in the right ballpark. In fact, I use this >>method >> >for >> >non-critical designs. >> > >> >======================= >> >Mikhail Matusov >> >Senior Hardware Design Engineer >> >Square Peg Communications >> >Tel.: +1 (613) 271-0044 ext.231 >> >Fax: +1 (613) 271-3007 >> >http://www.squarepeg.ca >> > >> > >> > >> > >> > >> > >> >----- Original Message ----- >> >From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx> >> >To: <si-list@xxxxxxxxxxxxx> >> >Sent: Thursday, January 05, 2012 10:22 AM >> >Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal >> >Board >> >Production >> > >> > >> >> Perhaps I'm the only one who is finding it ironic that, on a "Signal >> >> Integrity" reflector list, "Impedance Controlled" isn't considered >> >> "Normal". I haven't had the luxury of not specifying impedance >>control >> >> since a small 33MHz PCI card design, many years ago. >> >> >> >> I'm afraid Jayasuryan that you won't find the answer you're looking >>for >> >>on >> >> an e-mail thread, or it is going to be a long, drawn out, painful >> >>affair. >> >> You have a lot of work to do to understand what impedance control is >>and >> >> how it relates to signal integrity. I would recommend starting with >>the >> >> books that have been listed many times on this list. You can also >> >>search >> >> the archives for "impedance control" to find discussions about >>different >> >> opinions on how much is enough. >> >> >> >> Good luck in the new year, >> >> Jeff Loyer >> >> >> >> -----Original Message----- >> >> From: si-list-bounce@xxxxxxxxxxxxx >>[mailto:si-list-bounce@xxxxxxxxxxxxx >> ] >> >> On Behalf Of steve weir >> >> Sent: Monday, January 02, 2012 6:23 AM >> >> To: si-list@xxxxxxxxxxxxx >> >> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs >>Normal >> >> Board Production >> >> >> >> Suppose as you like. Hope as you might. What you don't contract is >>not >> >> guaranteed. >> >> >> >> Steve. >> >> On 1/2/2012 5:56 AM, Jayasuryan KG wrote: >> >>> Dear Experts, >> >>> >> >>> >> >>> >> >>> Happy New Year!! >> >>> >> >>> >> >>> >> >>> I have question regarding the impedance controlled board production! >> >>> Is there any special process to produce impedance controlled board >> >>> >> >>> rather than the normal production? >> >>> >> >>> >> >>> >> >>> Suppose if I go with normal production for a impedance controlled >> >>>board >> >>> (the design has been done to meet the impedance) what are the >>possible >> >>> issues can happen? >> >>> >> >>> >> >>> >> >>> Looking for your immediate response. Thanks in advance. >> >>> >> >>> >> >>> >> >>> Best Regards, >> >>> >> >>> - Jayasuryan >> >>> >> >>> ------------------------------------------------------------------ >> >>> To unsubscribe from si-list: >> >>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject >>field >> >>> >> >>> or to administer your membership from a web page, go to: >> >>> //www.freelists.org/webpage/si-list >> >>> >> >>> For help: >> >>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >> >>> >> >>> >> >>> List technical documents are available at: >> >>> http://www.si-list.net >> >>> >> >>> List archives are viewable at: >> >>> //www.freelists.org/archives/si-list >> >>> >> >>> Old (prior to June 6, 2001) list archives are viewable at: >> >>> http://www.qsl.net/wb6tpu >> >>> >> >>> >> >>> >> >> >> >> >> >> -- >> >> Steve Weir >> >> IPBLOX, LLC >> >> 150 N. 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Fleischmann > > >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >//www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > >List technical documents are available at: > http://www.si-list.net > >List archives are viewable at: > //www.freelists.org/archives/si-list > >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu