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Solder flow Ni/Au

Views: 4953

Mark

#48175

Solder flow Ni/Au | 5 March, 2007

Hello,

We are having issue with one of the customer board. This is 10 layer PCB FR4 with black solder mask. Coating Ni/Au. Soldering leadfree.

We are using 7 zones air reflow oven (zones top&bottom).

We have bed solder flowing for this boards. The solder is only where was printed. We tested couples of diffrent solder pastes (flux, activation) but not improve. We also made a print a leaded paste and solder is bahaving the same as lead free not covering the pads. We used diffrent reflow profile RSS and RTS not improve. We suspect the contamiantion of Ni layer (not activation).

What is the proper thickness of Au layer and Ni?. What if Ni layer is too thick or too thin?.

How can I prove customer that PCB is rubbish?

Mark

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#48182

Solder flow Ni/Au | 5 March, 2007

On your ENIG thickness requirements, search the fine SMTnet Archives for previous discussions, like: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=33661

On determining if your board will solder properly: ANSI/J-STD-003, Solderability Tests for Printed Boards

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#48196

Solder flow Ni/Au | 6 March, 2007

Hi Mark,

Solder paste will not flow on Ni like it appears on HASL. Where you print it is where it will reflow. Has been like that for years. As a CM you should re-engineer / recut your stencil to provide proper solder joints. I seriously doubt if there is anything wrong with the boards.

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Mark

#48232

Solder flow Ni/Au | 7 March, 2007

Hello,

We replated the boards with new Ni and Au and the soldering flow is excellent. There is 100% covarage of the pad even for reduced appertures.

Mark

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#48233

Solder flow Ni/Au | 7 March, 2007

Well there ya go, this proves you can't engineer from your desk, thru a computer, miles away! I'm also surprised you answered back - most don't. Thanks Mark.

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#48243

Solder flow Ni/Au | 8 March, 2007

ENig can vary in quality, but I've never seen an ENiG board that's been downright unsolderable. At a CM where I worked, I had to prove a QE wrong. He was flippin' out (*no offense*) about black pad, something commonly seen on ENig boards, so what I did, I printed a board, with no components, reflowed it, and then observed the wetting spread across it. We ran tin-lead Indium paste there as well, and as Chunks states below, ENig, by nature, will only wet where there's paste. This wetting spread (or lack of) is even more prevalent when running lead-free. On this "test board" there were no "non-wetting" conditions anywhere.

That being said, you have to go by overall joint quality and not just judge quality by wetting spread. If the solder joint has flowed up the component termination and somewhat across the pad, you gots a good solder joint.

Now..if you did all this above, and you DO in fact have a solderability issue with boards, you have to consult with your PCB supplier (or have your SQE do this..it is her job after all..ha-ha-ha)...'cause when it comes to ENiG or Immersion Ag, which supplier they use is everything...there's only a couple of good suppliers of this coating.

Too bad SMTNet doesn't allow picture posting. You'd be able to post your .jpg right in this winder, and all the guwu's here would tell you...good or bad.

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abjason

#48317

Solder flow Ni/Au | 11 March, 2007

There is nothing to argue if you had found Ni above or togather with Gold, definitly you got poor wetness and awful solderbility for sure.

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