Hi Dave! Hi to you too Doug, got your picture. WOW. I had no idea that happens! http://stevezeva.homestead.com/SquishedBalls.jpg So when you coat a board that has BGA's, I take it that just a layer of coating won't cause this, but if the coating wicks beneath the BGA you can have problems? Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Friday, September 13, 2013 6:17 AM To: [log in to unmask] Subject: Re: [TN] Gull wing solder joints and minimum electrical clearance 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 ________________________________ The enclosed documents are proprietary items to Silicon Forest Electronics' (SFE) customers. They shall not be reproduced nor disclosed for any purpose except as specified in writing from an authorized agent of SFE. These documents may contain data restricted for export by the International Traffic in Arms Regulations (ITAR) section of the Arms Export Control Act (or the Export Administration Act). Violators are subject to severe criminal penalties. ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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