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QFN solder issues Lead Free

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#51175

QFN solder issues Lead Free | 24 July, 2007

We are currently have failures on one of our QFN components. We are running this product with lead free paste, lead free boards and lead free parts. They have done a pull test on this component and it showed that the solder joint mainly dissconnected from the leads and not pulling up any of the pads. The solder joint was still intact but you can tell where the part sat in the solder joint. I have checked the profile and everything looks great. I even tried 3 different profiles, but it still looked the same. I am somewhat convinced that the part did not want to adhere to the joint. If anyone can give me what direction to go to I would appreciate it. At this point I am not sure what to try next. Thanks for any input.

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#51176

QFN solder issues Lead Free | 24 July, 2007

It sounds like the QFN component is not solderable. * Use ANSI/J-STD-002, Solderability Tests for Component Leads, Terminations, Lugs, Terminals, and Wires * Contact your QFN component supplier for help * Consider a more active flux, since you might be stuck with these parts

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#51213

QFN solder issues Lead Free | 26 July, 2007

check your stencil design on the ground pad. You might have a big aperture opening that pushing the component away from the paste. Look alos the way your pcb warp. Prioritize side that has component that need flat pcb as much as possible. hope this helps..

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#51217

QFN solder issues Lead Free | 27 July, 2007

> We are currently have failures on one of our QFN > components. We are running this product with > lead free paste, lead free boards and lead free > parts. They have done a pull test on this > component and it showed that the solder joint > mainly dissconnected from the leads and not > pulling up any of the pads. The solder joint was > still intact but you can tell where the part sat > in the solder joint. I have checked the profile > and everything looks great. I even tried 3 > different profiles, but it still looked the same. > I am somewhat convinced that the part did not > want to adhere to the joint. If anyone can give > me what direction to go to I would appreciate it. > At this point I am not sure what to try next. > Thanks for any input.

I agree with Dave, did you check the solderability of the QFN? is this a noclean application or water sol?

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#51223

QFN solder issues Lead Free | 27 July, 2007

We have issues with these also. They need to be flat to solder well. Reduce the square under the part for the heat sink and youll improve yields. That pad keeps the part lifted high while the other smaller joints reflow and partially attach. You can change the square to smaller circles or a middle finger shape if that works better! haha I hate qfn's

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#51226

QFN solder issues Lead Free | 27 July, 2007

Well I agree with jdumont in the fact that you should reduce the center pad at least 50%. Generally the sides of the leaded ends are not plated and solder will not wick up. This means only the bottoms of the leads wil solder. Look in this area when yanking off the part to see if it soldered properly.

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