Thanks. I had the same difficulty, that's why I did it. To everyone else, sorry for the interruptions and thanks for your patience. . and now, back to our regularly scheduled broadcast: SIGNAL INTEGRITY!!!! j . On Thu, Jan 14, 2010 at 9:59 AM, Arjun Bingipur < arjun.bingipur@xxxxxxxxxxxxxx> wrote: > Thanks Jack. Personally, I feel without the modifier charts, it would > have been a difficult task analysing the temperature curve on its own. I was > on it for a quite some time without much clarity. But with modifiers > and temperature curves together, it becomes so much simpler. It would have > helped if it was part of the the IPC spec. > > Regards, > Arjun > > ------------------------------ > *From:* Jack Olson [mailto:pcbjack@xxxxxxxxx] > *Sent:* 14 January 2010 15:11 > *To:* Arjun Bingipur > *Cc:* Doug Brooks; SI-LIST > *Subject:* Re: [SI-LIST] Re: IPC-2152 trace current/temperature calculator > > No, I created those charts myself, using the data in the new spec (which > was obtained from the Lockheed Martin and Naval Surface Warfare Center, > Crane Division experiments) > > The reason I created the "modifier" system is because the way the document > is laid out, you have to read all kinds of extra stuff (including the > Appendix!!!) just to get a decent result. The charts give you a starting > number, but then the text describes all kinds of things that can influence > the number. I tried to condense what was there into an introductory approach > to deriving a better answer than the historical charts could have ever > provided. It is the SIMPLEST, in other words. > I couldn't put too many charts in the article (and PCDesign magazine was > already complaining about the length!) so for example I showed how to use > the universal chart (based on 3oz copper) and modify the result for any > other copper > thickness to get a decent approximation, but of course you will NOT have to > do this if you have all of the temperature curve charts in the spec itself, > because it contains ALL the copper thicknesses for both internal and > external. > > And maybe I don't have to say this, but there are other considerations that > may influence your result. For example, this data is provided for traces in > STILL AIR, and since most of our designs are in sealed housings these > numbers are good enough for us, but if you have designs with good air flow, > you may get better results with even smaller traces. On the other side of > the coin, if you use a specific distance to your nearest plane but your > nearest plane is chopped and split, > your results may vary. And finally, I didn't even address parallel traces > at ALL, and just about every design has those. > > so... > > To summarize I can only say > 1) this is a better starting point than IPC has ever provided before > 2) It is only an approximation, so add some derating "wiggle room" > 3) You may need thermal simulation to prove your own results > 4) get the spec, it contains much more than I could put into that little > article > > (that's why I don't envy Doug the task of trying to make a calculator. > everything needs a disclaimer!) > > http://pcdandf.com/cms/magazine/209/6850/ > > hope that helps, > Jack > > > . > On Thu, Jan 14, 2010 at 5:06 AM, Arjun Bingipur < > arjun.bingipur@xxxxxxxxxxxxxx> wrote: > >> Jack, >> >> As per your document, If we are trying to obtain the final trace width >> using the new universal chart rather than the conservative chart, we >> need to be able to modify the values according to the modifier charts. >> But, having gone through IPC 2152, I do not find the modifier chart >> information. However, I'm currently having access only to the IPC 2152 - >> final Draft document, dated December 2008. Does the released IPC 2152 >> spec contain this information or am I missing anything here? >> >> Regards, >> Arjun >> >> -----Original Message----- >> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >> On Behalf Of Jack Olson >> Sent: 13 January 2010 19:38 >> To: Doug Brooks >> Cc: SI-LIST >> Subject: [SI-LIST] Re: IPC-2152 trace current/temperature calculator >> >> Doug, >> I apologize for using the word WRONG in my last post. >> >> You have my sincere gratitude for the papers you have written and the >> tools you have developed and shared so unselfishly. I really appreciate >> those contributions and I intend to make good on my promise to buy you a >> lunch someday for letting me use your utilities for FREE for so long >> (smile) >> >> While I agree that it would be very difficult to implement all the new >> data in IPC-2152 into a simple tool, the one thing that jumped out at me >> was the proximity to planes. Most of the other factors can't influence >> the result by more than a few percent. And I'm not a programmer either, >> but it seems like it would be easy to add the distance to nearest plane, >> even if you want to derate it somewhat for safety margin. Although I'm >> not a "thermal guy", I was on the IPC committee (did you see my name on >> page iii? twice? My mom did! Ha) anyway (sorry about that shameless >> puffery) I would cheerfully help you any way I can, if you ever try to >> implement more of it into your tool. I even have a few formulas that >> were interpolated (?) from the curves in an excel spreadsheet. >> By the way, we were considering incorporating the fusing data on your >> (UltraCAD.com) site into the standard, but we didn't want to delay the >> publication. maybe next revision.... >> >> Finally, I totally agree with you that the historical chart has >> withstood the test of time (because in most cases it is very >> conservative), but what is need is a safer way to "push the envelope" if >> the designer needs to use smaller features. >> >> Do you have any interest in developing a free thermal simulator for us? >> (grin) >> >> thanks, Doug >> >> Jack (aka "the new guy") >> >> p.s. PLEASE accept my apology for implying that your calculator is wrong >> >> >> >> . >> On Wed, Jan 13, 2010 at 1:13 PM, Doug Brooks >> <dbrooks9@xxxxxxxxxxxxxxx>wrote: >> >> > Thanks for the link to your paper. Its a good contribution. Well done. >> > I'll consider trying to implement some of it in the next version of >> > the calculator. >> > >> > But please understand that this is now the third version of our >> calculator. >> > We have never ever suggested that it is *RIGHT* or *WRONG*. In fact, >> > given that there are almost an infinite number of combinations of >> > stackups layer dimensions trace dimensions and form factors swiss >> > cheese effects component placement component thermal effects >> > environmental effects materials properties etc >> > >> > anyone would be a little foolish to suggests they even knew or could >> > know what *RIGHT* and *WRONG* really was. >> > >> > Also, note that we did not help write the standard, nor were we a >> > member of any subcommittee >> > >> > We don't even necessarily endorse the standard (and the IPC doesn't >> > necessarily endorse our calculator, at least as yet) >> > >> > The calculator merely makes using the standard (right or wrong, >> > somehow >> > defined) easier. >> > >> > The calculator is actually based on 5, user selectable data sources. >> > These sources differ by as much as 40%. The new IPC-2152, Vacuum, is >> > the most conservative. The old IPC-D-275 is the most aggressive. The >> > old standard has been criticized through the years (with some >> > justification) BUT nevertheless many people think that it HAS >> > withstood the 50-year test of time! The data from another study, >> > reported in Design News in 1968, provides results that are in between >> > the other standards. The final decision of what results to use are the >> >> > system designer's responsibility, based on the risks he/she >> > understands and is willing to take. We don't endorse any one of the >> data sources. >> > >> > The trace current/temperature calculations are one of four >> > capabilities of the calculator. Others include an estimate of fusing >> > current (see an article on our web site), skin effect calculations >> > (including skin depth, crossover frequency, and frequency and >> > temperature adjusted trace resistance, see an article on our web >> > site), and basic Ohm's Law calculations for traces. The trace >> > current/temperature calculations and fusing current calculations can >> be automatically adjusted for skin effects. >> > >> > Again, we never suggest our calculators are *RIGHT* or *WRONG*. Just >> > that they make working with already established formulas and >> > relationships easier. We developed them for our own use, and make some >> >> > of them available to others --- as is and as represented. >> > >> > Doug >> > >> > >> > >> > >> > At 08:45 AM 1/13/2010, Jack Olson wrote: >> > >> >> Not to complain (kudos for developing the calculator!) but since >> >> proximity to planes has the most drastic effect over any of the other >> >> >> factors, and it is a fairly linear relationship, I'm curious why you >> >> didn't incorporate it. >> >> (only one extra box!) of course, not knowing about splits and "swiss >> >> cheesiness" of the plane, maybe you were simply afraid? (grin, >> >> kiddin' ya) There is a graph in this article if you are interested: >> >> http://frontdoor.biz/PCBportal/HowTo2152.pdf >> >> >> >> Unless I'm misunderstanding your calculator, I think your result will >> >> >> be about 50% WRONG in most cases (since most boards have planes these >> >> >> days) >> >> >> >> just trying to help, >> >> keep up the good work, >> >> Jack >> >> >> >> >> >> >> >> > From: dbrooks9@xxxxxxxxxxxxxxx >> >> > Subject: [SI-LIST] Re: IPC-2152 trace current/temperature >> >> > calculator >> >> > Date: Tue, 12 Jan 2010 22:38:19 -0700 >> >> > >> >> > I don't know if you have read the standard. There are a couple of= >> >> pages >> >> > that address thermal modeling, planes, alternative dielectrics, >> >> > etc,= in >> >> a >> >> > very general manner. There are no quantitative adjustments included >> >> >> > (= >> >> with >> >> > the possible exception of how to treat parallel conductors which is >> >> >> > pr= etty straightforward, and pretty obvious.) There is a Figure >> >> > A-13 that rela= >> >> tes >> >> > to some estimated factor adjustments that can be used based on the >> >> > dist= ancebetween the conductor and a plane for 1 Oz traces in .070 >> >> >> > thick >> >> Polyim= >> >> > ide Board (and a single curve for 2 Oz traces). The calculator >> >> > does n= >> >> ot >> >> > incorporate these adjustments in its calculations. But these >> >> adjustments= >> >> > caneasily be made to the calculated results if desired. Overall, >> >> > the >> >> gene= >> >> > ralities included in the Standard apply equally well to the >> >> > calculated resu= lts from the calculator. >> >> > The Calculator is based o= n Conductor Sizing Charts contained in >> >> > the Appendix (from Figure A-17, p 35= to Figure A-86, p83). >> >> > >> >> > Doug >> >> > >> >> >> >> >> >> ------------------------------------------------------------------ >> >> 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 >> >> >> >> >> > Check out our resources at http://www.ultracad.com >> > >> >> >> ------------------------------------------------------------------ >> 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