Hi Kerry,
A commonly targeted P level in eless Ni is 8-10%. Higher levels are
generally purposely made for high corrosion resistance to acidic
environments. Electroless Ni with about 12% P is a high P materials so used
for acidic corrosion resistance. The higher the P, the higher the
resistivity, and the more amorphous the deposit becomes. At the levels you
report the material is at the high edge of P content and would be the most
resistive, most amorphous, and least solderable. Au plating on high P eless
Ni may also result in a lower Au uniformity and this may not be good when
the Au thickness is as low as 2 - 4 micro-inches. Since high P electroless
Ni is susceptible to corrosion by Alkaline solutions, if the Au plating is
spotty it is possible that Ni may be exposed through random voids in the Au
film, leading to Ni corrosion in alkaline cleaning.
It is also interesting to note that Ni-Phosphide can begin to
precipitate from electroless Ni-P deposits with heating above about
260-280C. This may suggest some concern with PbFree reflow, but I have no
data, pro or con, on this actually occurring with PbFree SMT reflow at 260C.
It is possible that the solder will not wet well to any nickel phosphide
grains formed in the surface of the nickel.
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
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-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, June 23, 2005 8:11 AM
To: TechNet E-Mail Forum; Leo Higgins
Subject: Re: [TN] BGA Intermittent Saga, part 2
Hi Leo,
You are correct. The 13% P really scared me. Normally, it should be zero,
right? I understood that any P will cause none wetting. Am I correct?
Thanks,
Kerry
Leo Higgins <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/23/2005 02:53 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Leo Higgins <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] BGA Intermittent Saga, part 2
These photos I sent in are ENIG. I believe Kerry meant that his problematic
boards were not ENIG, but were in fact tin plating over electroless NI with
13% P.
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
The information contained in this electronic message is CUSTOMER/SUPPLIER
PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the
individual or entity named above. If the reader of this message is not the
intended recipient, you are hereby notified that any dissemination,
distribution and copying of this communication is strictly prohibited. If
you have received this communication in error, please immediately notify the
sender by electronic mail. Thank you.
-----Original Message-----
From: Ingemar Hernefjord (KC/EMW)
[mailto:[log in to unmask]]
Sent: Wednesday, June 22, 2005 9:02 AM
To: TechNet E-Mail Forum; Leo Higgins
Subject: RE: [TN] BGA Intermittent Saga, part 2
Nickel corrosion? Under tin plating? I don't understand.
I would rather suggest tin plating over bad wetting. In all metalurgical
handbooks, nickel has the grade 'poor' , when talking solder wetting.
I've had several incidents with bad tin plating on nickel the last year.
E.g. a multipin plastic package, on which we could shear off the tin by
pulling the component legs between your thumb and index finger nails!!
If it's really nickel corrosion, what caused that? This is not a ENIG
nickel corrosion situation. Is it possible to get a SEM cross section
image?
Good Luck
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Leo Higgins
Sent: den 22 juni 2005 06:18
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent Saga, part 2
I will send a pair of pictures from an Amkor paper showing optical
micrographs showing Ni corrosion and a pad with no Ni corrosion to Steve to
see if he can put up on his web site. Published studies on Black Pad issues
often show similar structures. Steve can you post the 2 photos? I will
send after this note.
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
The information contained in this electronic message is CUSTOMER/SUPPLIER
PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the
individual or entity named above. If the reader of this message is not the
intended recipient, you are hereby notified that any dissemination,
distribution and copying of this communication is strictly prohibited. If
you have received this communication in error, please immediately notify the
sender by electronic mail. Thank you.
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, June 13, 2005 2:16 PM
To: [log in to unmask]; [log in to unmask]
Subject: RE: [TN] BGA Intermittent Saga, part 2
You state to look for Au cyanide etching in the eless Ni. With what
instrument or is this under a high power micro scope (1000X). Can you
describe what to look for or perhaps you can share a photo of the
artifact you are suggesting.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins
Sent: Monday, June 13, 2005 1:39 PM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent Saga, part 2
Excessive stress from pneumatic presses used to bond heat sinks to BGAs
after board level assembly has been shown to induce failure at the
solder to
BGA pad on packages that meet pre-SMT assembly quality specs in all
ways.
Subsequent analyses may show no evidence of black pad (cross sectioning
to
look for Au cyanide etching into the eless Ni, etc.).
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
The information contained in this electronic message is
CUSTOMER/SUPPLIER
PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the
individual or entity named above. If the reader of this message is not
the
intended recipient, you are hereby notified that any dissemination,
distribution and copying of this communication is strictly prohibited.
If
you have received this communication in error, please immediately notify
the
sender by electronic mail. Thank you.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jana Carraway
Sent: Monday, June 13, 2005 1:01 PM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent Saga, part 2
Werner,
If it's black pad on the component side, how would Kerry prove or
disprove
it? Could he find the cause by using Auger or cross-section? What
would be
the appropriate tests to perform to find root cause? Should he send a
component back to the supplier for root cause analysis?
Thank you,
Jana Carraway
Jana Carraway
MSEI - Advanced Technology Group
6024 S.W. Jean Road
Lake Oswego, OR 97035
503.697.5291, ext 1180
email: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier
Sent: Monday, June 13, 2005 10:04 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Intermittent Saga, part 2
Hi Kerry,
You most likely have 'Black Pad' on the componet side. That, together
with
the stess concentration from the SMD-geometry, caused a briitle
ionterfacial
overstress failure.
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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