Thanks to those that responded and belated Happy Thanksgiving to my southern neighbours!
When customers sting you with a screwdriver you need to answer, so this is why I've asked this rather ridiculous question. I had browsed my new library and indeed, both Wassink and Perry Martin say damage should not occur in the joints, without mentioning the fact that testing should be appropriate. So simply showing the paragraphs to the concerned person would have left a shadow of doubt.
I believe things are clearer now.
Best regards,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
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De : [log in to unmask] [mailto:[log in to unmask]]
Envoyé : November-28-11 8:13 AM
À : TechNet E-Mail Forum; Ioan Tempea
Cc : [log in to unmask]
Objet : Re: [TN] Mechanical testing of joints
Hi Ioan - what you describe is not a test, it is someone playing around with a screwdriver. The failure location of a solder joint is a combination of many factors - Andy just touched the top of the list of things that need to be characterized and documented. Force on solder joints do not always result in the pwb pad being the failure location. If someone wants to test the solder joint strength, then they should put the screwdriver down and conduct a test with the appropriate equipment.
Dave
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
11/24/2011 09:21 AM
Please respond to
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Ioan Tempea <[log in to unmask]>
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Re: [TN] Mechanical testing of joints
Hi Andy,
The test was simply like that: somebody took a screwdriver and manually applied a force until something broke. No control, no aging, nothing else and, on top of it, I did not see the tested samples yet, so I have no clue whether the separation is interfacial part-solder or in the solder. The main reason was that the end caps of the fuse are gold plated and the solder (SAC305) doesn't go uphill much.
Based on the assumption that a good joint means pads will lift before anything else yielded, this screwdriver test came up and it turns out the lands did not lift, but the component came off, I believe (seeing a couple of pictures) with some solder on it, which rather points to failure in the solder.
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask]
W | www.digico.cc
N'imprimer que si nécessaire - Print only if you must
-----Message d'origine-----
De : Giamis, Andy [mailto:[log in to unmask]]
Envoyé : November-24-11 10:10 AM
À : TechNet E-Mail Forum; Ioan Tempea
Objet : RE: 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/>
N'imprimer que si nécessaire - Print only if you must
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