I have notice that many attribute determine the pull strength of A BGA, #of bumps, Pwr/Gnd/signals, pad configuration, edge glue, copper foil tooth treatment.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, November 28, 2011 8:38 AM
To: [log in to unmask]
Subject: Re: [TN] Mechanical testing of joints
Dave is correct. Pull testing should be done using an Ametek pull tester or something similar. However, just because pull testing a given component type establishes a mean tensile stress of 3200 grams does not mean that a single component that broke at 2000 grams is a reliability "failure".
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Monday, November 28, 2011 7:13 AM
To: [log in to unmask]
Subject: 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
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Ioan Tempea <[log in to unmask]>
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Subject
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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