Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

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Black Pad

Views: 2528

#38927

Black Pad | 10 January, 2006

Hi. We have experienced black pad phenomenon on a lot of 200 boards (immersion gold finish). This lot of boards has been completely assembled and we had about 20% fallout during functional test.

My question is this ... Is there a way to inspect the remainder of the boards to see if they have the black pad condition, or should I scrap them all? I have about $10K tied-up in these boards, so I would be willing to go to "some" lengths to do this.

As a side-note, what liability should I expect of my bare board house who concedes that this is black pad?

Thanks, Mike.

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JAX

#38928

Black Pad | 10 January, 2006

I am not sure how you know you have "Black Pad"... Did you have one of the boards Cross Sectioned and Analyzed by an outside source? If yes, I would go back to the Fab House for the total cost of the product you currently have at the full 200 piece qty. Total cost would be actual material and labor w/o markup. If no, I would send a board out for test... depending on results see above.

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Amol Kane

#38931

Black Pad | 10 January, 2006

I read a paper somewhere that outlines a non destructive test for black pad detection. it showuld be on my hard drive. Black pad is as a result of impurities in the plating bath and poor process control. I shall dig up the paper and mail it to you if you can give me your e-mail.

Amol

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JAX

#38938

Black Pad | 10 January, 2006

I don't believe I have ever seen a non-destructive test for "Black Pad" that I could take back to a Fab house and collect monetary losses with... But if this test method actually does hold merit then collect away. I would like to know how this method actually determines: 1.Corrosion cracks at the intermetallic layer. ( showing penetration into the nickel or spreading laterally across the surface) 2.Higher phosphorous levels in the correosion sites as compared to the rest of the nickel area.

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#38940

Black Pad | 10 January, 2006

There is a tape test from IPC in their TM-650 spec that can be downloaded for free from the ipc website. It will test for gold adhesion to the underlying nickel. Section 2.4.1E, I believe. It is quite simple to perform.

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#38950

Black Pad | 10 January, 2006

JAX:

Thanks for the reply. We did send one of the boards back to the bare board supplier and they do concede that it is black pad. When you inspect the assembled board under a microscope, you can easily move the entire solder joint away from the pad of the board. When you do so, there is a text book image of black pad phenomenon.

Thanks, Mike.

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#38951

Black Pad | 10 January, 2006

Amol:

Hi. Thanks for the reply. I would love a copy of the paper you mentioned! My e-mail is miked@sealevel.com

Thanks, Mike.

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#38952

Black Pad | 10 January, 2006

Hi. Thanks for the reply. I will download the test method. This will be a good test from this point forward at the bare board level. I do have a lot of assembled boards that potentially have this problem, however ...

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#38954

Black Pad | 10 January, 2006

Implementing a Simple Corrosion Test Method to Detect "Black Pad" Phenomenon in Electroless Nickel/Immersion Gold Plating ; BabHui Lee; Circuitree 11/1/03 http://www.circuitree.com/CDA/Archives/34f2b343900f7010VgnVCM100000f932a8c0

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#38956

Black Pad | 10 January, 2006

Muse

We don't believe that the IPC TM-650 Test Methods Manual, 2.4.1E, Adhesion, Tape Testing--5/04 [ http://www.ipc.org/4.0_Knowledge/4.1_Standards/test/2.4.1E.pdf ] that you refer to is a "black pad" test. We think it's a method for testing the adhesion quality of platings, marking inks or paints, and other materials to the underlying laminate.

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#38963

Black Pad | 11 January, 2006

This was the test method mentioned to me about 5 years ago, to use for testing for black pad, when we were evaluating the use of gold immersion for the first time. It is not practical for testing the entire surface of a PCB, but it should work well for a quick sample check. I got the suggestion from someone on the IPC technet forum at the time.

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