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Solder void underneath the mosfet

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#61454

Solder void underneath the mosfet | 24 March, 2010

Hi all,

Anyone used to come across solder void underneath mosfet as shown in the attached file? Will this pose any reliability issue, such as get burnt during functional test? How to over come this problem? As far as I know there is no acceptable IPC criteria that cater for solder void that happen to mosfet..If you know it, pls share with me...Thanks in advance..Sean

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#61455

Solder void underneath the mosfet | 24 March, 2010

Hello Sir I faced the same problem for QFP in DTH product in India. IPC stated that void should not be more than 25% of solder joint. But this type of void definatly create problem during functional test. Please check the folloeing point... 1.Check the open via below mosfet. 2.Check the solder paste heght. 3.Rethink about the stencil aperature design.

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#61466

Solder void underneath the mosfet | 25 March, 2010

Hello Rajeshwara,

If not mistaken, the 25% solder void specification is for BGA...As I I as know, no specification given to mosfet component yet..I think you are right, I need to look at the stencil aperture in order to reduce the air trap underneath the component..

About the reliability wise, I just completed run in test for 24 hours with such solder void entrap beneath..The board is still pass functional test..Its look to me the board is still functioning well even with solder void more than 50% of the total solder available.

Rgds, Sean

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#61469

Solder void underneath the mosfet | 25 March, 2010

the voids will cause a long term relability problem as the part will not be correctly heatsinked. Change your stencil aperature to a "+" sign 15-20 mils wide in the center of the pad.

___________ : | : : | : :----|----: : | : :____|____:

As the solder melts it will force the flux out and not let it get trapped. It has worked for me.

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#61474

Solder void underneath the mosfet | 26 March, 2010

Hello Sir. We also have faced a same problem. At that time, we had to repair it because we could not find any solution. But in our experience, the void underneath FET was more severe whenever we used the FET that have been made long time ago. It is also estimated that the void may be affected by oxidation or contamination. To use a new lot and compared to old lot will give you some information. Please try it. Thanks Ju-young.Jeong

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#61475

Solder void underneath the mosfet | 26 March, 2010

Hi, yes we used to see this kind of problem our customer end. This due to stencil aperture opening.these kind of issues we will overcome thorough our stencil process. please contact. ravikumar@asahitec.in

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#61479

Solder void underneath the mosfet | 26 March, 2010

What about thermal cycling and/or vibration over the long term? My guess is that with the voids the joint would not be as reliable long term as a joint without the void. Am I thinking correctly?

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