PRISM Forum

Add Message About this forum

Newer messages are at the top

Previous 5 messages

Posted by: Barry Ives (barry.ives@lmco.com )
Organization:Lockheed Martin System Integration - Owego
Date posted: Thu Apr 18 8:52:35 US/Eastern 2002
Subject: Instantaneous failure time
Message:
What does "Instantaneous Failure Time" refer to and how is it used in the calculation of the infant mortality factor?

Replies:
Instantaneous failure time
David Dylis Thu Apr 18 9:41:25 US/Eastern 2002

Reply to this message


Posted by: Chris Wright (christopher.d.wright@baesystems.com )
Organization:BAE SYSTEMS
Date posted: Wed Mar 6 15:32:13 US/Eastern 2002
Subject: RACRates IC Model Questions
Message:
I have been evaluating the PRISM IC RACRates model for my company and have a few questions.
First, how is it that the pi-factors tend to go down for non-hermetic devices versus hermetic? This seems counter intuitive, especially for pi-RHT. The overall device failure rate ends up being lower for a non-hermetic part. Is this true? Second, it appears that pi-TO, pi-RHT, pi-DT and Lambda-SJ all vary with device temperature, but there is nothing in the manual which describes these relationships. I am also puzzled as to why pi-RHT would change when I add a junction temperature rise, since this is supposed to be a non-operating factor. The junction temperature rise should only apply to operating factors. When non-operating the device should be at its non-operating ambient temperature with no junction temperature rise since it wouldn't be dissipating power at that point.

Replies:
RACRates IC Model Questions
David Dylis Thu Mar 7 13:36:47 US/Eastern 2002

Reply to this message


Posted by: Boutbien Laurent (laurent.boutbien@mbda.fr )
Organization:MBDAM (Châtillon France)
Date posted: Wed Feb 27 10:21:13 US/Eastern 2002
Subject: similarity between software and paper guide
Message:
Using your own example for a system analysis, i was focusing on the study concerning the reliability calculation for the four resistance R1-R4 of A3A2 sub-assembly. The aim of this study was to identify the relation between the software and the tabulated figures within the paper guide. Keeping the original parameters (i.e element temperature calculation is based on ambient temperature and default temperature rise), I was not able to check the default tabulated parameter for the following factors : PiTO , PiTE , Pi DT and lambdaSJ. I am aware that choosing different options for the element temperature calculation will induce different Pi-factors. However I do not understand why selecting the default option is not leading to the selection of the default parameters (these summarised in the tables : table C5 page 192 version 1.2).
Can you please explain why the parameters are not corresponding to the ones expected (for ground stationary, indoors). Thank you for your help. Best Regards

Replies:
Resistor Pi Factors for PRISM
David Dylis Thu Feb 28 15:29:00 US/Eastern 2002

Reply to this message


Posted by: Boutbien laurent (laurent.boutbien@mbda.fr )
Organization:MBDAM (Châtillon France)
Date posted: Wed Feb 27 4:59:54 US/Eastern 2002
Subject: query on Process Grade Score
Message:
Morning,
First of all, thank you for your previous answer regarding the PRISM software guide. I am now able to have a better understanding of the PRISM philosophy analysis. However, I have now a new question concerning the relation between the Process Grade Score query and the corresponding Pi-Factor. Answering the different queries for the Process Grade Score, I have noticed that there is no corresponding between the software true figures and the expected tabulated figures summarised in tables I-4 (page 262) and H-10 (page 247). In order to illustrate this remark , please find herefafter the result of the simulation : Type Pi (software)Grade Pi (tables) Design 0,0419 78,3% 0,039 Manufacturing 0,0347 83,6% 0,034 Part Quality 0,0795 89,3% 0,075 Management 0,0020 89,5% 0,002 CND 0,1460 76,2% 0,134 Induced 0,0272 100% 0,009 Wearout 0,0229 100% 0,008 growth 0,927 100% not tabulated Infant Mortality 0,271 100% not tabulated please explain. Moreover, How can you justify constant value for the growth factor and infant mortality factor despite the existence of mathematical formulae for determining these factors (Pi function of time). Thank you for your assistance and help. Best Regards

Replies:
Query on Process Grade Score
David Dylis Thu Feb 28 14:36:33 US/Eastern 2002

Reply to this message


Posted by: BOUTBIEN (laurent.boutbien@mbda.fr )
Organization:MBDA (Châtillon FRANCE)
Date posted: Mon Feb 25 8:21:26 US/Eastern 2002
Subject: query for PRISM documentation
Message:
Hello,
My company had just purchased the PRISM toolkit (version 1.2). However, within the package, there is no manual documentation which i consider mandatory for a better understanding of your software. Is it possible to receive a official documentation (not only the on line help !)provided i give you all the detail necessary to proove the purchase ? Thank you in advance for your help and hoping an quick answer in my E-mail address. Yours faithfully.

Replies:
PRISM User's Manual
Tammy Sehn Mon Feb 25 8:47:11 US/Eastern 2002

Reply to this message


Next 5 messages

| 1...5 | 6...10 | 11...15 | 16...20 | 21...25 | 26...30 | 31...35 | 36...40 | 41...45 | 46...50 | 51...55 | 56...60 | 61...65 | 66...70 | 71...75 | 76...80 |

Add Message About this forum