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September 2013

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From:
"Wenger, George M. [Contractor]" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M. [Contractor]
Date:
Wed, 11 Sep 2013 13:59:49 -0500
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Richard makes a very good point about checking to see if the bulge might be a wetting issue.  Have you inspected the gull wing leads on any of the non-soldered components to see what the sides look like or have you run any solderability tests on the gull wing leads?  Unless you are using a very thick stencil or have a very wide aperture I would think that the heel of the gull wing leads, which are usually more solderable than the sides of the lead would allow the excess solder to wick up the heel and keep the side bulge to a minimum.

George
George M. Wenger
Failure Signature & Characterization Lab LLC
609 Cokesbury Road, High Bridge, NJ 08829
(908) 638-8771 Home (732) 309-8964 Mobile
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, September 11, 2013 2:48 PM
To: [log in to unmask]
Subject: Re: [TN] Gull wing solder joints and minimum electrical clearance

If the bulge is clearly due to excess solder, and good wetting away from the bulge is apparent (in other words, the bulge is not caused by a wetting issue), and minimum electrical clearance is not violated, then I do not see why they would need rework. The bulge of solder along the edges of the pad at the PWB level certainly is not going to affect the compliant portion of the lead above the heel.
You may also wish to look at the reflow profile. It is possible that a slightly hotter profile on top will draw more of the solder into the heel fillet, which is always good.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Wong
Sent: Wednesday, September 11, 2013 1:06 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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