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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Mark Chapman
Date posted: Tue Jul 12 7:43:19 US/Eastern 2005
Subject: Connection/Interconnection FR
Message:
I need some help please. I am doing a 217F N2 prediction using MILSTRESS and there are different component connection failure rates that are being generated. One is IR (interconnection rate) and the CR (connection rate). I know that CR is dependant upon the number of pins and whether the components connection is through hole or SMT and it is what I have always used. My customer is asking me to create a separate block category keyword ST - IA,Surface Mount Tech and then put all of the components under it. This automatically creates a FR of 0.592 fpmh and does not take into consideration the component-board soldering. Section 16.2 of 217F N2 states that this failure rate does not include soldering!! IMHO I would have thought that the components should be created in the normal way taking into consideration soldering and then the SMT board FR of 0.592 fphm added at the end. Can anyone please comment on this. Thanks.


Reply:

Subject: Connection Reliability Models
Reply Posted by: bwd (bdudley@alionscience.com )
Organization: RAC
Date Posted: Wed Aug 3 11:40:58 US/Eastern 2005
Message:
Mil-Hdbk-217 has seperate models for connections (solder, etc) and for circuit boards. The connection model is very exact in that the type of connection is identified for each failure rate. So, all you have to do is sum the different connections and types (Model 17.1) The circuit board models (16.1 and 16.2) are specified for through hole leaded connections and surface mount connections. If two technologies are used both models are added together. If the board only uses one technology then only one failure rate is utilized as is stated in the direction in Mil-Hdbk-217.


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