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Solder bridging on one corner of BGA

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dd

#53237

Solder bridging on one corner of BGA | 16 January, 2008

Any one got experience on handling solder bridging under one corner of BGA?

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#53242

Solder bridging on one corner of BGA | 17 January, 2008

HI, I have ran into this a time or two, and what I did before we got the BGA rework station was to run some flux under the component, and since the flux that was in the solder on the other solder joints has at least part of the way burned off in the original reflow, I would go ahead and apply (I used spray bottle) flux to the rest of the board, and then RE-reflow the board. This is not the greatest way to fix the problem, but if you are in a pinch It worked for me. as far as how to prevent the problem, the only thing I can think of is to look at the problem area of BGA prior to placement and make sure that there is no irregularity in Ball Diameter, then just make sure that your Paste looks perfect before placing, and before I would worry about it, I would take a look at the schematic for the board, alot of times there are un-used balls or common grounds and what not, that would make it where it really wouldn't matter(other then cosmetic) that there is a bridge. not really sure what you were looking for, Handling/fixing the bridge or handling/preventing the bridge. Good Luck, Wayne

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dd

#53320

Solder bridging on one corner of BGA | 22 January, 2008

Thanks, I am working on to prevent solder bridging.

Tried fine tuning reflow profile, solder printing looks fine.

Any further ideas??

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GSx

#53347

Solder bridging on one corner of BGA | 23 January, 2008

Hi,

are you dealing with Leaded or Lead Free P-BGA ? soldering by Lead or Lead Free paste ?

Any way, some time, bridges can be caused by moisture entrapped in the BGA body. Make sure if is respected the correct MSL's allowed flore exposure time, otherway need to bake them.

GSx

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#53348

Solder bridging on one corner of BGA | 23 January, 2008

In addition to the pre-emptive steps mentioned above, in my experience there are certain BGA package designs that seem more prone to that corner bridging. I have seen some packages that will essentially "curl" down at one corner as the package begins to approach the peak temperature in the reflow profile. The packages I am referring to are PBGAs with a larger proportion of FR4 exposed on the perimeter of the BGA. The times that I have encountered this, I have modifed the speed of the belt, rather than the temperature peaks. A bit longer soak before flux activation, and a slower climb to reflow has help alleviate this in a number of cases. Somethimes the BGA has enough mass that it does not heat very evenly, so slowing down the heating process will allow the cooler parts of the BGA to "catch up" to the hotter parts, reducing the delta T across the package. Large temperature deltas across the package are a likely culprit for this type of defect.

'hege

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