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BGA and PCB finishing

emmanuel

#4662

BGA and PCB finishing | 14 March, 2000

I am to implement PBGA, and i am looking for PCB surface finish informations. A lot of technical reports are specifing NiAu finishing because of flatness property. Because of leads shape, I though that BGA doesn't need flat pads like QFP. Is it false ? When all is said and done, i don't know what to really specify; so i will appreciate any hints about this topic.

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JAX

#4663

Re: BGA and PCB finishing | 14 March, 2000

Emmanuel, The discussion on what finish to use whether it be HASL, Immersion gold over nickel, Organic Solderability Preservatives, ect...... is still ongoing. This is not the only decision you need to make. Do you plan on Soldermask Defined Pads? What will your Pad diameter be in relation to the ball diameter ( if applicable, mask diameter )? I personally do not think you need Ni/Au finish just because your placing PBGA.

That's just my opinion, I could be wrong

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#4664

Re: BGA and PCB finishing | 14 March, 2000

Emmanuel: Take Jax's word. NiAu (ENIG) primary (some would say only) redeeming characteristic is its flatness that you mentioned, but that flatness appeals to folk placing fine pitch devices, rather than BGA. Good luck. Dave F

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#4665

Re: BGA and PCB finishing | 22 March, 2000

Be careful if you use Ni/Au. The "black pad" phenomenum can be crippling. We moved from Ni/Au to OSP because of it. I also don't want to return to the lack of flatness of HASL.

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