Hi Victor - I don't have an example of what happens to a QFP as Ian
detailed but Doug and I have the same phenomenon for a BGA. Hey Doug -
can ya send Steve one of the BGA pictures?
Dave Hillman
Rockwell Collins
[log in to unmask]
From: Victor Hernandez <[log in to unmask]>
To: <[log in to unmask]>
Date: 09/13/2013 05:50 AM
Subject: Re: [TN] Gull wing solder joints and minimum electrical
clearance
Sent by: TechNet <[log in to unmask]>
Can you share this phenomenon photo?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Fox, Ian
Sent: Friday, September 13, 2013 2:39 AM
To: [log in to unmask]
Subject: Re: [TN] Gull wing solder joints and minimum electrical clearance
Here's a phenomenon that can occur Richard. On fine pitch QFPs with a
generous volume of solder in the joint or a bulging joint, the presence of
a reasonable thickness of acrylic conformal coating (say 100um) between
the feet of the device, together with regular extended periods of time
below zero degC (say -10 degC) can result in the solder being extruded out
of the joint thus forming a short to the adjacent lead. The modulus of the
acrylic is greater than that of the SnPb at sub zero temps so the solder
is under compression and flows.
Been there and got that particular T-shirt
Regards
Ian
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 11 September 2013 20:03
To: [log in to unmask]
Subject: Re: [TN] Gull wing solder joints and minimum electrical clearance
Joyce, how would it affect reliability?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Wednesday, September 11, 2013 1:18 PM
To: [log in to unmask]
Subject: Re: [TN] Gull wing solder joints and minimum electrical clearance
More likely effect your reliability than electrical clearance.
Joyce Koo
Researcher
Materials Interconnect Lab
Office: (519) 888-7465 79945
BlackBerry: (226) 220-4760
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Wong
Sent: Wednesday, September 11, 2013 2:06 PM
To: [log in to unmask]
Subject: [TN] Gull wing solder joints and minimum electrical clearance
We have assemblies where gull wing solder joints have so much solder that
along the side joint, the solder connection extends out to the adjacent
leads similar to Figure 5-1, Image C from IPC-A-610E. "the solder
connection to a termination may exhibit a wetting angle exceeding 90
degrees when it is created by the solder contour extending over the edge
of the solderable termination area or solder resist" (We will be modifying
our stencils to reduce the amount printed on these parts in the future).
There is no IPC-610 spec for this condition so we were thinking that if
the spacing between the solder joints does not violate Minimum Electrical
Clearance, they are acceptable.
Is this a correct acceptability criteria?
Thanks,
Peter
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