Hi Waclaw,
It looks like it may be a case of "Black Pad" but you have to use SEM/EDS, as well as finer polishing to confirm. Another thing is that the intermetallic layer in your case is rather thick.
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] <mailto:[log in to unmask]>
-----Original Message-----
From: karpinski [mailto:[log in to unmask]]
Sent: Thursday, February 19, 2004 11:33 AM
To: [log in to unmask]
Subject: Re: [TN] Ni/Au solderability on kapton
Hello ,
Thank for your help.
I send you some pictures showing X-section of the solder joints.
I am not expert on this topic. Please comment on them.
Fig. 2
X-section through non soldered pad with Au layer showing very rough Ni
Layer
Fig. 6
X-section of a unseperated solder joint
Fig.8
X-section (etched) of a solder joint showing a strange Ni-solder interface
Fig. 10
Pictures of broken pads and peeled SMD resistor
regards
Waclaw
Leo Higgins schrieb:
>This sounds like either typical black pad problem, or a passivated Ni
>surface under the very thin immersion gold layer. A determination of the
>failure interface as suggested by another respondent is necessary. A
>cross-section of a failed interface and an unseparated interface from the
>same sample set would help in making a diagnosis (SEM / EDX map and line
>scans for O, Ni, Sn, P). A scanning Auger map of the surface can help in
>seeing if the Au deposit is low density or porous, and if it has allowed Ni
>to oxidize and prevent good wetting after the Au is dissolved in the solder.
>
>
>Regards,
>Leo
>
>------------------------------------
>Leo M. Higgins III, Ph.D.
>ASAT Inc.
>Central Region Mgr. / Director of Sales
>[log in to unmask]
>3755 Capital of Texas Hwy-So
>Suite 100
>Austin, TX USA 78726
>tel: 512-383-4593
>fax: 512-383-1590
>mobile: 512-423-2002
>------------------------------------
>
>
>-----Original Message-----
>From: karpinski [mailto:[log in to unmask]]
>Sent: Wednesday, February 18, 2004 3:38 PM
>To: [log in to unmask]
>Subject: Re: [TN] Ni/Au solderability on kapton
>
>
>Hi Vladimir,
>
>As I know it is Pd.
>regards
>
>Vladimir Igoshev schrieb:
>
>
>
>>Hi Waclaw,
>>
>>Do you know what material (Pd or Ru) your board supplier uses to deposit
>>
>>
>electroless Ni?
>
>
>>Vladimir Igoshev,
>>Research in Motion
>>
>>Voice: (+1) 519-888-7465, ext. 5283
>>Fax: (+1) 519-886-0863
>>E-mail: [log in to unmask] <mailto:[log in to unmask]>
>>
>>
>>-----Original Message-----
>>From: karpinski [mailto:[log in to unmask]]
>>Sent: Wednesday, February 18, 2004 4:15 PM
>>To: [log in to unmask]
>>Subject: [TN] Ni/Au solderability on kapton
>>
>>
>>Recently we have solderability problems with Ni/Au kapton flex boards
>>(0,1 µm Au, 3 µm Ni, 35m Cu).
>>We have produced and assembled large number of boards.
>>On 10 % of the boards we observe interconnection failures after final
>>assembly of the pcbs. If the suspected solder joints are lightly
>>stressed , the connections are easily broken, leaving an open circuits.
>>It is easy to peel these parts with solder material from the boards.
>>The pads below the removed parts are discolored dark gray and are sleek .
>>Some times the handsoldering of the broken joins was successful but
>>after small strain the joints broke again.
>>Additional vapor phase soldering did not improved the the strength of
>>the joints.
>>This is new problem for us. Does anyone have any experience with this?
>>How to rework the boards? How to determine when a board should be
>>reworked or
>>scrapped? What about reliability issues? Latent failures?
>>I would appreciate your help very much
>> regards
>>
>>--
>>Waclaw Karpinski
>>I. Physikalisches Institut
>>RWTH Aachen
>>D - 52074 Aachen
>>
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>
>--
>Waclaw Karpinski
>I. Physikalisches Institut
>RWTH Aachen
>D - 52074 Aachen
>Sommerfeldstr 14, Turm 28
>Tel.: +241 802 7181
>Fax.: +241 802 2623
>Mobil: 0049 173 70 22 548
>
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>847-509-9700 ext.5315
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--
Waclaw Karpinski
I. Physikalisches Institut
RWTH Aachen
D - 52074 Aachen
Sommerfeldstr 14, Turm 28
Tel.: +241 802 7181
Fax.: +241 802 2623
Mobil: 0049 173 70 22 548
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