TECHNET Archives

July 2010

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Inge <[log in to unmask]>
Date:
Thu, 22 Jul 2010 12:53:08 +0200
Content-Type:
text/plain
Parts/Attachments:
text/plain (125 lines)
Forgot to tell you little more on high current conductors and pads. It's the
delta across the via plus the pad (or the truehole plus the pad) that
determines. From delta you can calculate on dissipation and by means of the
w/mK for the actual system you can get the temperature. Most use a margin
factor, which  I can't give, because it's often empirically based by the CAD
guy. But this is not the end. If you have to do with advanced boards, you
may also have to consider the impact of transients and start up current. As
we do not have a full picture of what you are designing, I think best advice
is that you contact a experienced CAD guy, they are the professionals, so
why not go to them..

/Inge


----- Original Message -----
From: "Inge" <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>; "Forrester, Michael (H USA)"
<[log in to unmask]>
Sent: Wednesday, July 21, 2010 10:23 AM
Subject: Re: [TN] SMT PAD Current Capability


> Michael,
>
> you should start with asking yourself what will the maximum temperature of
> the conductor be? To get an answer on that you need calculate the
> resistivity. If you got voltage, resistivity and current, it's just to use
> Ohm' law as you know. (It may be little more complicated if you have
> pulsed current with certain duty cycle.) Then how to get the resistivity?
> Lazy as I am, I use a Siemens nomogram with conductor width on Y axis and
> resistivity on X axis. The curves show the recommended copper thickness
> for various temperatures. I think it's simply from a Deutsche Industri
> Norm, but I don't have the actual number,
>
> I'll scan my copy and send it offline to you later this day.
>
> /Inge
>
>
>
> ----- Original Message -----
> From: "Forrester, Michael (H USA)" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, July 20, 2010 5:34 PM
> Subject: [TN] SMT PAD Current Capability
>
>
> I'm a bit confused on how to calculate the current capability of a SMT
> pad.  We have a 2220 size chip bead that has 8A flowing through it.
> Our pad geometry is built per IPC specifications but the manufacturers
> datasheet calls out for a PAD twice the width (part max is 10A).
> So the question came up, with our current pad geometry (to IPC), what is
> the current capability?  I understand that it is based on the
> cross sectional area of the copper.  The current density of copper is
> 4.02 A/sq-mm.  For a 1 oz copper trace the area is
> 1.4 mils x trace width.  But what do I use for a PAD?  I have an width,
> length, and thickness.  For instance I have a SMT pad that
> is 1.5mm X 6mm using 1 oz copper with multiple traces coming off of the
> pad.  What is the current carring capability of that pad?
> Or am I thinking about this wrong?  Thank you.
>
> Best Regards,
>
> Michael Forrester
> Sr. Product Engineer
>
> Siemens Healthcare Diagnostics
> 101 Silvermine Rd.
> Brookfield, CT  06804
> PH: (203) 740-6452
>
>
> -------------------------------------------------------------------------------
> This message and any included attachments are from Siemens Healthcare
> Diagnostics
> and are intended only for the addressee(s).
> The information contained herein may include trade secrets or privileged
> or
> otherwise confidential information. Unauthorized review, forwarding,
> printing,
> copying, distributing, or using such information is strictly prohibited
> and may
> be unlawful. If you received this message in error, or have reason to
> believe
> you are not authorized to receive it, please promptly delete this message
> and
> notify the sender by e-mail with a copy to
> [log in to unmask]
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815
> -----------------------------------------------------
>


______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2