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October 2005

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Subject:
From:
Vladimir Igoshev <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Vladimir Igoshev <[log in to unmask]>
Date:
Thu, 27 Oct 2005 11:07:24 -0400
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I think we've talked about it a few months back. There are several publications from Atotech, where they describe the properties of "modified" ENIG (Ni/Pd/Au) plating. You might want to take a look at the papers.

As far as so-called "brittleness" of solder joints on ENIG is concerned, then I've got an impression that there is a bit of confusion with the issue. 

First of all, "gold embrittlement" shouldn't be an issue at all, if we are talking about IMMERSION gold. I simply can not imagine what type of solder joints it should (stand-off wise) to contain the threshold level of gold due to its dissolution from the board. 

Secondly, the "Black Pad" does exist, but I' wouldn't say it is as common issue as it used to be and it has nothing to do with "brittleness of the solder joints", but we the process control (I think everyone would agree that any process can be screwed :-))

Thirdly, ENIG finished boards do prone to a particular a type of failure  called "Brittle Fracture". It has nothing to do with the "Black Pad", but has everything to do with the type of load the joints were exposed to An impact type of load is that what ENIG joints do not like. 

I think the confusion between the "Black Pad" and the "brittle Fracture" comes because the appearance of the fracture surface in both cases is sort of similar. However, two modes are different in nature and can be told apart, if not just planar analysis is used but also cross-sectioning is involved.

Regards,

Vladimir



Vladimir Igoshev, Ph. D.
Senior Materials Researcher
Research in Motion
451 Phillip St.
Waterloo, ON, N2L 3X2

Voice: (+1) 519-888-7465, ext. 5283
Fax: (+1) 519-886-0863
E-mail: [log in to unmask]


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ray, Carl (GE
Infrastructure)
Sent: Thursday, October 27, 2005 9:22 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG and brittleness


I got one for you guys....... I have a board house who claims to have created a process the eliminate the "Black Pad" issue while decreasing the gold brittle issues of ENIG finishes. They claim a thin layer of Palladium between the gold and nickel does the trick... I am not familiar with this process and have requested more data from the board supplier to support their claims.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier
Sent: Wednesday, October 26, 2005 11:25 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG and brittleness


Hi Eddie,
You will not find such information.
First, while ENIG can lead to brittle interfacial separations, it does not
lead to brittle solder joints--as in 'gold embrittlement.' the difference is in
the failur mode, the separation would be at the Ni/Ni-IMC interface, not the
solder per se.
Second, while some people claim to have suppliers who do not produce ENIG
suffering from 'Black Pad' brittle interfacial separations, many reports of
ENIG-'Black Pad' failures are documented.
Thus, the real question is why is your customer looking to convert to ENIG,
and what is he converting from?

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com

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