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Printed Circuit Board Assembly & PCB Design Forum

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QFN Rework

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QFN Rework | 23 May, 2008

Does anyone have any great ideas and suggestions for the rework of small package (5 x 7mm) QFNs with raised pads (3 mils off of the bottom of the package). IO count is 36.


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QFN Rework | 23 May, 2008

We've used hot-air guns in the past to rework QFN's and DFN's.

Cheers ..rob

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QFN Rework | 23 May, 2008

Well if you are getting bridges under, one thing that we used to do was flood the part with flux and then run it back through the reflow. Keep in mind we were not a High reliability manufacturer. This practice didn't hurt OUR boards, and most of the time it would fix the problem. Hot air, or a good BGA rework station also works. We found that most of our trouble with those little guys were that we had to reduce the apperature size to 70% of the pad size to reduce the amount of paste being applied. Good luck, Wayne

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QFN Rework | 24 May, 2008

Bill Our suggestion removing small QFN is: * Heat the board be from the bottom side using a convective heater. * Use a hot gas or air on the top side of the component. A good starting point is air velocity of 15 to 20 liters per minute. * Select a nozzle to direct the heating in the component area. * Take steps to minimize the heating of adjacent components.

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Matt Kehoe


QFN Rework | 28 May, 2008

Wayne, lets talk about QFN's off line. Matt Kehoe SIPAD Systems INc. 770-475-4576

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QFN Rework | 3 June, 2008


I think what you are describing is a half-etch QFN, which causes the 3 mil gap. In our process, we don't require solder to bridge this gap as it's internally connected to the bottom lead. I'm not sure if this is the question you're asking, but it proved to be difficult for our rework personnel as well. We started ordering our QFN's in full etch which eliminates this gap and makes the rework a lot easier. Other than that, our rework process is the same as DaveF describes.

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QFN Rework | 11 June, 2008

yes I have - at first you should read the following application note: - afterwards you can use the contact form on the right side of the webpage or just take a call and ask for dominik 0049 30 9366810 he can answer your questions Regards, Daniel

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