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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: Lim (limth@cet.st.com.sg )
Date posted: Thu Jul 18 3:54:01 US/Eastern 2002
Subject: ESS for Fine Pitch SMT components
Message:
Hi, My company is currently using fine pitch SMT components in one of our products. We practise ESS whereby we subject products to Random vibration of 20-1000Hz with a Grms of about 6g. However, because of these fine pitch components used, we are concerned that the mentioned vibration profile will damage the product. Does anyone have any experience in this area whcih they can advise. Is there any specific profile to use? Tks.


Reply:

Subject: ESS Vib on SMT
Reply Posted by: Joe Dzekevich (jdzekevich@ieee.org )
Date Posted: Fri Jul 19 8:37:57 US/Eastern 2002
Message:
The correct process would be to do a HALT test on your product and find both the operational and destruct limits. Then, derating from the operational limits, set your ESS and/or HASS/HASA profiles. Then take a sample of products and do a proof of screen for 10-20 cycles and ensure no damage except for defects. Using this process, I have not had any problems with fine pitch SMT, even at levels higher than 6 Grms. Other components, like large profile caps, connectors, etc. will break first.


Reply:

Subject: ESS for Fine Pitch SMT components
Reply Posted by: Lim
Date Posted: Wed Jul 31 1:06:03 US/Eastern 2002
Message:
Hi, Joe, thanks for advice. I have done a vibration with increasing grms values starting with 1 thru 6. The product was still functioning. Therefore, we have decided that we will perform our vibration ESS at about 5grms and a ASD of 0.03g2/Hz on our production units and then analyze any failures and adjust the screen accordinly. Tks.


Reply:

Subject: ESS for Fine Pitch SMT
Reply Posted by: Andre Kleyner (andre.kleyner@delphiauto.com )
Organization: Delphi Corporation
Date Posted: Mon Aug 5 10:29:09 US/Eastern 2002
Message:
I think it depends on what kind of PCB you are going to mount it on. I don't think 6 Grms would be damaging to the component itself, but the PCB resonance can be harmful if the deflection of the circuit board is large enough. Generally in automotive environment, which is considered harsh enough, the product (component, PCB, at all) goes through 1.5 Grms 10-1000 Hz. This is considered as accelerated level. Let me know if you need more info. Andre


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