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From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 4 May 2010 07:14:06 -0500
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Hi Bev - my personal opinion is that a void neither enhances (i.e. acts as 
a crack stopper) nor degrades solder joint reliability unless you reach a 
threshold where the void has physically reduced the overall solder joint 
area thus making the distance a crack has to progress to fail a solder 
joint critically short. There are a number of published industry reports 
that would support that hypothesis. I would follow the logic path that 
George does for his RF applications - what size or total amount of voiding 
impacts the functionality of the product application. In your case, you 
are looking for a solder joint area for a variety of component styles that 
can withstand the rigors of dropping a hand held device. The drop test 
idea that Ioan proposed could be a way to derive a data set. And you avoid 
(yes, that was an intentional pun) having to make voids by creating solder 
joints of different areas for testing. And it would be a really good co-op 
project! Good Luck.

Dave



Bev Christian <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
05/03/2010 07:24 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Bev Christian <[log in to unmask]>


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Subject
Re: [TN] Question about Voids in Solder Joints






Thanks, George. Most detailed answer yet.

At Nortel we never had a void spec for leaded components either. And, as I
think I have said on TechNet before, we would find many joints after pull
testing or cross-sectioning that looked like Swiss cheese, but we never 
had
field failures as a result.  BUT we were manly concerned about the
possibility of failures due to thermal cycling.

Now I worked for a company where the main concern is customers dropping
their product onto hard edges.  We do a lot of work to try and design and
build products to survive multiple drops in different orientations, but
occasionally a switch is going to come down on a pointed rock or a 
customer
is going to rip a charging cable out of a connector at a 45 degree angle
(yikes).  These are the things I am talking about.  I was leaning towards
25% for leaded components, so you and I are in the same ball park, George.
Others have suggested a higher number, but without some encouraging words 
in
that direction from fellow TechNetters, I ain't goin' there.
Bev
RIM 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Monday, May 03, 2010 5:57 PM
To: [log in to unmask]
Subject: Re: [TN] Question about Voids in Solder Joints

Bev,

We're in a similar position to Dave Hillman.  We basically follow IPC
standards (where there are standards).  We do not have a company standard
for leaded components.  A couple of small voids is okay, more or large 
voids
are not.  Having said that you'll probably ask how many is a couple and 
what
is small and what is large.  We don't have a really good answer.  Since we
do a lot of RF power component work we've adopted a voiding specification
that has worked well for IC packages.  They typically use a criteria of
total die attach voids <20% with no single void >5% is okay. We don't
actually measure voids in leaded devices but if we were to see 20% voiding
in a leaded component solder joint we'd be concerned. 

Regards,
George
George M. Wenger
Senior Principal FMA  / Reliability 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 Bev Christian
Sent: Monday, May 03, 2010 3:48 PM
To: [log in to unmask]
Subject: [TN] Question about Voids in Solder Joints

TechNetters,
I was thinking about just putting "Voiding" as the e-mail title, but I
contemplated what I might get in responses and amended my title
accordingly.

My question is the following: do any of your companies have upper limits
on the amount of voiding in SMT solder joints of components that
customers have access to - like connectors and switches?  These of
course are leaded components.  I am not talking about Pb, but the form
of the interconnect between the component body and the board.

If so, are you willing and can you share?

Bev
RIM

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