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Bga replacement on ENIG Fabs.

mantis

#25275

Bga replacement on ENIG Fabs. | 26 July, 2003

All, Is it possible and reliable to replace bga's on Enig boards with out suffering from mass fallout due to blackpad defect.I have a couple of boards requiring bga replacment but i have been told that it is not possible to replace them reliable that blackpad defects will be inherent in every board i rework. Any thoughts would be welcome. Regards Mant.

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#25276

Bga replacement on ENIG Fabs. | 28 July, 2003

You are 100% correctomundo about ENIG. When it's good it's good, BUT when it's bad, you just want something else. You know you have black pad, when you see parts falling from the board.

First, there is not perfect solderability protection.

Second, most major fabs list comparions of various solderability protection materials on their sites. For instance, check here: http://www.merix.com/technology.php?section=add&page=secured/pdf/surface_finish_options.pdf

[We have no relationship nor receive benefit from the company referenced in the above link.]

Third, consider immersion tin or silver. They are: * Relatively inexpensive * Flat * Reliable * Easy to solder, if you do incoming inspection

Caveats: * Use a fab that turns his process, imm solutions that sit are not good * Do incoming inspection * Handle the boards properly * Train your troop on handling, slightly higher soldering temperature, and different appearance of solder connections * Turning your stock would be better, than not

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Ioan Tempea

#25277

Bga replacement on ENIG Fabs. | 28 July, 2003

Mant,

we are reliably replacing BGAs of all sizes and pitches on ENIG. The black pad is not something created through rework, but a defect that the PCB has from the very beginning.

Ioan

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RDR

#25284

Bga replacement on ENIG Fabs. | 29 July, 2003

Why would you get black pad from rework? I could be wrong but once the pad has accepted solder from the first reflow process wouldn't that eliminate the possibility of a latent finish defect? I am curious. We do perform rework on ENIG all of the time and I am not aware of any reliability or soldering issues.

Russ

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#25285

Bga replacement on ENIG Fabs. | 29 July, 2003

We agree with Russ and Ioan that rework does not cause black pad. It's caused during the board fabrication process.

On the other hand, we think: * Mantis wants to reduce the amount of reworking of boards that fail due to a black pad problem. * Someone told Mantis that rewoking black paded boards is a waste of time, because black paded pads cannot be reworked.

So, Mantis wants to consider an alternate solderability protection.

We agree with the point about rewoking black pad. We never found a good approach for reworking boards that failed due to black paded pads. A board with black paded pads is a scrap board.

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mantis

#25286

Bga replacement on ENIG Fabs. | 29 July, 2003

Thanks all for you input, Perhaps i wasnt making my point clear,I have some boards with black pad defect and i wanted to know could i rework them succesfuly with out incurring the wrath of this scourge,but from your commenst it seems i may as well send them to an early grave. Thanks again for your time. Mantis

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