TECHNET Archives

November 2005

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:
- Bogert <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, - Bogert <[log in to unmask]>
Date:
Sun, 13 Nov 2005 09:11:44 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (95 lines)
Thanks for the info.
  ----- Original Message ----- 
  From: Wenger, George M.<mailto:[log in to unmask]> 
  To: [log in to unmask]<mailto:[log in to unmask]> 
  Sent: Saturday, November 12, 2005 4:00 PM
  Subject: Re: [TN] SV: [TN] Seeking Tantalum Chip Capacitor Reliability Information


  DITTO!

  Our experience is identical to Ingemar's.  We essentially ban the use of tantalum capacitors.  If a designer wants to use them he needs to get sign off from a VP showing that he doesn't have a choice and that he has made sure that he's used at least a 50% derating 


  Regards,
  George
  George M. Wenger
  Reliability / FMA Engineer
  Base Station and Subsystems Group
  Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask]<mailto:[log in to unmask]>

  -----Original Message-----
  From: TechNet [mailto:[log in to unmask]] On Behalf Of Ingemar Hernefjord
  Sent: Saturday, November 12, 2005 11:47 AM
  To: [log in to unmask]<mailto:[log in to unmask]>
  Subject: [TN] SV: [TN] Seeking Tantalum Chip Capacitor Reliability Information

  We have had problems with exactly same cap one year ago, they broke down electrically, even exploded! I think you have a derating problem.
  Reported failures had to do with inrush current and heat dissipation (internal losses). We used recommended formulas for calculating correct application of series resistors, peak voltage, max reverse voltage etc.
  Finally, we gave up and did this: two in parallel, another two in parallel and these in series. Clumsy, yes, but we have had no problems since that. I've written a report, let's see if I can find it. 

  Of course, various brands show different failure rates. We performed accelerated life test on two new brands. Some hundreds of each, max DC voltage at room temperature. 1 kOhm in series for each cap in order to follow leakage current and avoid direct shorts. While our standard cap began to show failures after 1 day (!!) and showed several failures to 1,000 hs, the other brand had <1 uA leakage all the way! All old caps were sent for destruction and the new brand was introduced immediately.
  BUT, as I said, this was a tough design with high demands on the caps, so we still got some, but very few, failures. And as the application is military, no failures are accepted the first five years in field. The above described parallel/series version has worked perfectly now for one year, not one single failure reported even after tough environmental and electrical testing.

  Inge

  -----Ursprungligt meddelande-----
  Från: TechNet [mailto:[log in to unmask]] För - Bogert
  Skickat: den 12 november 2005 14:26
  Till: [log in to unmask]<mailto:[log in to unmask]>
  Ämne: [TN] Seeking Tantalum Chip Capacitor Reliability Information

  November 12, 2005

  Folks, we are experiencing large number of failures of tantalum surface-mount chip capacitors (CWR06 style).  The capacitors are a modified version of MIL-C55365 parts to give an extended CV range.  The parts are modified 35 Volt rated parts to yield 22 microfarad, 50 volt rated parts.  Reverse peak voltage for these parts is 2.5V at 85C and 5V at 25C.  The failed parts were installed correctly.  We checked voltage ratings, ripple current, etc. and all are OK for the application.

  There is a problem with board layout since the vendor hand soldered the parts to the board by applying soldering iron directly to the top surface of the capacitor rather than to the pad area (the capacitor manufacturer indicated this is not recommended).  This is because the layout was flawed since the land area was not larger than the part so the pad could not be heated via the soldering iron.  The vendor subsequently changed method of soldering to implement pre-heat and reflow soldering and no longer uses hand soldering.  However, even with these changes, the parts are still failing.

  This part is a commercial version of a MIL-C-55365 part.  The vendor does no burn-in electrical screening testing on the parts so we suspect our failures may be due to the normal bath-tub curve in that we are not weeding-out premature failures.

  Does anyone have reliability data showing what failure rates can be expected for these type capacitors for both non-electrically screened tested vice electrical screened tested parts.  Also, what are the most likely failure modes for this type part and what are the failure
  ---------------------------------------------------
  Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest
  Search the archives of previous posts at:
  http://listserv.ipc.org/archives<http://listserv.ipc.org/archives>
  Please visit IPC web site
  http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100
  ext.2815
  -----------------------------------------------------
  mechanisms?

  ---------------------------------------------------
  Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100 ext.2815
  -----------------------------------------------------

  ------------------------------------------------------------------------------------------------
  This message is for the designated recipient only and may
  contain privileged, proprietary, or otherwise private information.  
  If you have received it in error, please notify the sender
  immediately and delete the original.  Any unauthorized use of
  this email is prohibited.
  ------------------------------------------------------------------------------------------------
  [mf2]

  ---------------------------------------------------
  Technet Mail List provided as a service by IPC using LISTSERV 1.8e
  To unsubscribe, send a message to [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest
  Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives>
  Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100 ext.2815
  -----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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