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SMT solder Covering component surface

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#69619

SMT solder Covering component surface | 27 June, 2013

We recently had a question come up regarding the amount of solder on a flat underside termination ( we referenced Flat Lug Lead in IPC 610). Judging by the photo you can see on the Left is a target solder joint, but on the right is one which had rework completed on it. There is no visible evidence of wetting to the lead, but it is pretty obvious this is a wetted solder joint. Some of the photos in the IPC book make it look as if a fully covered Lead is OK, while stating Fail for Class 1 if there is not evidence of proper wetting. The quoestion is, would this be acceptable seeing how it was a reworked solder joint using an Iron and not convention reflow?

Thank you for your input

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Pete B

#69660

SMT solder Covering component surface | 1 July, 2013

Do you have access to an x-ray system? If so you can determine if the solder wetting to the lead along it's length meets the criteria set out in IPC-610.

Pete B.

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#69661

SMT solder Covering component surface | 1 July, 2013

I do have access to an X-ray but it is only 2-D and it just appears as a black solder joint, not to impressive.. The main question though if it is a reowked solder joint does it still need to show wetting on the lead or can it be covered with solder such as the IPC photo of the SOT packages showing the solder to the body. It isn't touching the body as the photo, but it is covered the same.

Thanks for your input

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#69662

SMT solder Covering component surface | 1 July, 2013

I always look for a toe fillet if the design allows you to. Many times the pad design is close or exactly the size of the leads which makes people to touch it up right away. I told them hundred times not to but...Luckily I have 3D x-ray and I can tell that 90% of the joint is good(even though they don't see it from the side). I hate when people touch up the boards without need - make sure that's not your case. Other than that the joint looks fine - you have wetting all over.

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#69663

SMT solder Covering component surface | 1 July, 2013

I think it is wetted also but I cannot verifiy without actually seeing the toe, heel or side fillets. In this case, the lead was overhanging the pad and as with this type of lead it is not acceptable so they were reworked. Many times rework personel will cover the lead like this. In through hole it is not acceptable so the question was raised for SMT.

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#69664

SMT solder Covering component surface | 1 July, 2013

I am also not sure if the Electrolytic capacitor has a "flat lug leads". I think it is more like a coined lead. I hope other experts can advice.

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