> -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf > Of Moshe Valdman > Sent: Monday, June 29, 2009 9:34 AM > To: '[email protected]' > Subject: On board flat ferrites breaking > > Hi all, > > We have DC/DC supplies on boards which include flat ferrites > mounted side to side (i.e. the PC conductors go through the > ferrites) When we test the boards for NEBS, including 10 cm > drop the ferrites tend to break (Interestingly during HALT or > other vibrations the ferrites survuve > well) > > Do you know this phenomenon? Is there some way to protect the > ferrites? > > thanks in advance for your inputs, > > regards, > Moshe
Moshe: Ferrites are inherently brittle. I assume you are describing surface-mount ferrite components, which are essentially a block of ferrite attached to the board with a couple of soldered joints. Any sudden shock will concentrate forces at the joints, making fracture failures reasonably expectable. The fractures might be caused by the inertia of the ferrite mass, or by flexing of the substrate board. You need a mechanical engineer's expert answer, but I could speculate that you try epoxying the ferrite mass to the board. Might help or might make it worse. As I said, I'm no vibration expert, but epoxy is cheap. Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
