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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: Leroy Meyers (meyers@drs-fsc-comm.com )
Organization:DRS Communications
Date posted: Mon Feb 26 15:47:55 US/Eastern 2001
Subject: Press Fit Connectors
Message:
For a new design, we need a 160 pin connector for a motherboard. In the past, we used 96 pin MIL connectors that could be solder connected to the board. Now it seems that only the Press Fit style is available (a DIN variation). This is for a Military Aircraft application. 1. How would I model the connecTIONS in MIL-HDBK-217F (section 17.1)? Is this considered crimp? 2. I looked in Prism for RAC data, but there is nothing called Press Fit. Would 'Pressure Type' be appropriate? 3. From a practical standpoint, how would these press fit connectors hold up in my environment as compared to the solder version? Any experience out there? Note: I will be on vacation for the remainder of this week.


Reply:

Subject: Reliability Press Fit Connectors
Reply Posted by: B. W. Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Mon Mar 26 10:56:08 US/Eastern 2001
Message:
Reliability models for press fit connectors are not available in either MIL-HDBK-217 or the new PRISM program. This technology is claimed to be at least 20 years old, but has not been modeled for reliability purposes nor has a data base been established. The design of the press fit connection is such that the crimp connection model is not appropriate as a substitute. The crimp process is an external pressure connection and the press fit is an internal pressure connection. The press fit connection is an really an oversized pin that is forced into a socket or connection hole and the elasticity of the of the compliant pin deforms to make a connection without destruction of the drilled through hole. The potential failure mechanisms or problems that could be expected in a high stress environment are: fatigue failure of the compliant pin internal construction resulting in a open or intermittent connection, corrosion of the contact area resulting in intermittent performance, and quality control of the forces used in the assembly machine resulting in crushed pins that have intermittent connection. The manufacturers of the press fit connectors claim that this technology is known for high reliability and allows multiple pressing of the contact into the same hole for repair or replacement purposes. Without actual field data under stressful conditions, the reliability is questionable when compared to the well established solder joint process. If one intends to use this technology in high stress conditions, it would be advised to perform an accelerated life test to determine the failure characteristics and life limiting mechanisms.


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