Hi Michael,
Unfortunately, that does not tell me very much in terms of what material is soldered to, what its CTE is and what the resulting SJ geometry is.
Werner
-----Original Message-----
From: Forrester, Michael (H USA) <[log in to unmask]>
To: Werner Engelmaier <[log in to unmask]>; [log in to unmask]
Sent: Tue, Jul 20, 2010 12:14 pm
Subject: RE: [TN] SMT PAD Current Capability
Werner,
The part is actually a Ferrite chip bead between the power connector and the rest of the circuitry.
Best Regards,
Michael Forrester
Sr. Product Engineer
From: Werner Engelmaier [mailto:[log in to unmask]]
Sent: Tuesday, July 20, 2010 12:09 PM
To: [log in to unmask]; Forrester, Michael (H USA)
Subject: Re: [TN] SMT PAD Current Capability
Hi Michael,
There is an additional consideration—what is called 'local expansion mismatch' [see pp. 39-40 in IPC-D-279] between the solder and the material(s) to which the solder is attached.
The CTE of solder is about 24 to 26 ppm/C, FR-4 and Cu are not much of a problem, but soldering ceramics, Alloy 42, Kovar, Thermount could create reliability issues if the pads become too large.
Werner
-----Original Message-----
From: Forrester, Michael (H USA) <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Jul 20, 2010 11:34 am
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 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
-----------------------------------------------------
|
