And you both forgot that like water in a pipe, electrons will migrate to the side of the via in which the flow is occuring, further reducing the effective "trace width" of the via...
aj >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Brad Velander >Sent: Tuesday, August 02, 2005 1:23 PM >To: [EMAIL PROTECTED]; Protel EDA Discussion List >Subject: RE: [PEDA] Vias. > >Ivan, > With regard to your comments on the current carrying >capability of a via. You forgot one factor, with everything >perfect plating-wise the via typically will have approx. 1/2 - >2/3 the copper thickness/weight of a trace. This is dependant >of course on the initial copper foil and plated Cu spec.. Then >add in the typical restrictive nature of vias to plating and >you will have a gotcha! The plating of a typical via will >typically only be 35% - 50% copper weight of an external trace >in real world practice. > > I'll wait for the usual snappy response, your coffee >mustn't have kicked in yet this morning Ivan. > >Sincerely, >Brad Velander >Senior PCB Designer >Northern Airborne Technology >1925 Kirschner Rd., >Kelowna, BC, V1Y 4N7. >tel (250) 763-2329 ext. 225 >fax (250) 762-3374 > > >-----Original Message----- >From: Bagotronix Tech Support [mailto:[EMAIL PROTECTED] >Sent: August 2, 2005 9:47 AM >To: Protel EDA Discussion List >Subject: Re: [PEDA] Vias. > > >For Brad: >What is manufacturable depends on your fab house. Every place >(except the high volume super cheap fabs) should be able to do >18 mil hole with no price premium. Some places go down to 13 >mil with no premium. As far as relationship to track widths, >the effective width of the conductive material in the via is >the via diameter * pi. So, a 13 mil via has an equivalent >track width of 13 * 3.14 = 41 mil. That's wider than your >tracks, so there should be no problems with current carrying >capacity. As far as pad size, the IPC rules (can't remember >which one) state there should be a minimum of 2 mil annular >ring around the hole. You also need to account for >misalignment of the drilled holes, due to drill machine >tolerances. Typically this is 5 mils. Therefore, your >annular ring as designed should be at least 7 mils. And so, >the via pad diameter ends up >14 mils larger than the hole diameter. For example, a 32 mil >via pad with a 18 mil hole. > >Best regards, >Ivan Baggett >Bagotronix Inc. >website: www.bagotronix.com > > > >____________________________________________________________ >You are subscribed to the PEDA discussion forum > >To Post messages: >mailto:[email protected] > >Unsubscribe and Other Options: >http://techservinc.com/mailman/listinfo/peda_techservinc.com > >Browse or Search Old Archives (2001-2004): >http://www.mail-archive.com/[email protected] > >Browse or Search Current Archives (2004-Current): >http://www.mail-archive.com/[email protected] > > This e-mail transmission and its attachments may contain information from Avtron Manufacturing, Inc. that is proprietary, privileged and/or confidential and is intended exclusively for the person(s) to whom it is addressed. Any use, copying, retention or disclosure by any person other than the intended recipient or the intended recipient's designees is strictly prohibited. If you have received this message in error, please notify the sender immediately by return e-mail and delete all copies. ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
