Ioan,
A photograph would go a long way to determining what happened. Looking at the SM fuse in the link you sent my assumption is that what happened is that the ceramic body of the fuse either broke or separated from the end cap termination. I assume the end cap remained soldered to the PCB pad. This isn't surprising for this type of SM fuse. The end cap terminations are only glued on to the ceramic body and the glue joint is typically weaker than the solder joint
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Giamis, Andy
Sent: Thursday, November 24, 2011 10:10 AM
To: [log in to unmask]
Subject: Re: [TN] Mechanical testing of joints
Hello Ioan
How much force was applied? How was the force applied (tensile, shear, etc)?
Was it less force than you expected? (How much less?) How did the solder wetting appear before the test?
Were there any other test factors, such as aging?
What was the solder?
Did the component actually break or was it a solder / intermetallic failure?
My first thoughts are that if you apply enough force, sooner or later, something is going to break.
If the pads are really well-designed and firmly anchored into a well-built board, the pads may tolerate more force than you'd expect.
________________________________________
From: TechNet [[log in to unmask]] On Behalf Of Ioan Tempea [[log in to unmask]]
Sent: Thursday, November 24, 2011 9:40 AM
To: [log in to unmask]
Subject: [TN] Mechanical testing of joints
Dear Technos,
Force was applied to an SMT passive part, just to see when and how it will break. It happened that it broke on the component side, rather than tearing the pad apart. And now we have a controversy, some say the soldering was not good, since the pad should always lift before ripping the component. Is it true, or the damage can occur just anywhere depending on so many factors, like the footprint, size of part (we're talking here of a rather thick part, 2.7 mm)?
See the part here http://www.littelfuse.com/searchresults.html?NttP=0451002.MRL&Ntt=0451002.MRL
So, again, is it the pads that should always rip under mechanical shock, or just anything in the joint could break?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer T | 450.967.7100 ext.244 E | [log in to unmask] <mailto:[log in to unmask]> W | www.digico.cc <http://www.digico.cc/>
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