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February 2004

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Subject:
From:
karpinski <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 19 Feb 2004 10:37:23 +0100
Content-Type:
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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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>-----------------------------------------------------
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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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