SRC Forum - Message Replies
Forum: Reliability & Maintainability Questions and Answers
Topic: Reliability & Maintainability Questions and Answers
Topic Posted by: Reliability & Maintainability Forum
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998
Posted by: Al Johnson
Date posted: Tue Nov 17 17:17:25 US/Eastern 1998
Subject: Theta (jc) by Package Type
I am a Reliability Engineer performing stress analyses on medical and computer equipment. Stress analysis requires Theta (jc) as a data entry field. Many specification sheets do not have Theta (jc), C/W. Also, 217F Theta (jc) by package type is very inadequate. Is there a current Theta (jc) by package type available?
Subject: Thermal Resistance, junction to case
Reply Posted by: Bruce Dudley
Organization: Reliability Analysis Center
Date Posted: Thu Nov 19 9:46:59 US/Eastern 1998
The Thermal Resistance values presented in MIL HDBK 217 are default values to be used as a last resort in estimating the thermal load on the device. Therefore, are very conservative. Part vendors have the best information on resistance factors based on their experience with the technology. If no information is available from one vendor, try another vendor with similar technology to see if they have a thermal resistance value. If they do, use it as substitute. The last published source of Thermal Resistances per package type was: RADC TR-86-97 Thermal Resistances of Joint Army Navy (JAN)Certified Microciruit Packages by Douglas Holzhauer. This document was produced in 1986, as result, it is probably useless for the new package and devices.
Subject: Theta Jc
Reply Posted by: Joe Ward
Date Posted: Fri Dec 4 15:44:13 US/Eastern 1998
Bruce covered it pretty well, I would just add that you have to call the component manufactuers and press them for an answer. They should be able to come up with it.
Subject: Theta jc
Reply Posted by: Mike Siegrist
Date Posted: Wed Jan 13 16:01:14 US/Eastern 1999
Another source for microcircuit theta jc is MIL-STD-1835B
" Interface Standard For Microcircuit Case Outlines ".
Subject: Theta (jc)
Reply Posted by: Brian Alphonso
Date Posted: Tue Mar 2 15:38:43 US/Eastern 1999
Just to note that the Theta jc values can often be found on the manufacturer's website, on either the parts spec sheet or sometimes as part of a general application note on thermal analysis or packaging reports.