Hi Joyce - the barrier layer can be either nickel or copper depending on
the component supplier. Obviously nickel is a better materials choice for
soldering process robustness but in terms of electrical characteristics,
some circuit designs work better with copper.

Dave

On Wed, Sep 6, 2017 at 4:58 PM, Yuan-chia Joyce Koo <[log in to unmask]>
wrote:

> http://www.electronicdesign.com/boards/rohs-implementation-challenges
> see the cross section of Ceramic cap - metallization got Ni layer... not
> seen on your image.  hopefully, it is not MFG missing a process (or cheap
> stuff for low temp/ Ag adhesive potting type).
> On Sep 6, 2017, at 3:01 PM, Yuan-chia Joyce Koo wrote:
>
> did it missing a Ni plating?  http://www.johansondielectrics
>> .com/understanding-ceramic-capacitor-terminations
>> best of luck.
>> jk
>> On Sep 6, 2017, at 12:25 PM, Giamis, Andy wrote:
>>
>> Hi TechNetters,
>>>
>>> Here’s something I have not seen before.
>>> I have seven different ‘theories’ for what’s happening here.
>>> Three of which do not involve mythical creatures, illegal substances or
>>> the alignment of celestial bodies.
>>>
>>> This capacitor is on a path that sees a lot of RF power.
>>> The unit went through 20 cycles of -70C to +115C while at nominal
>>> power.  Temperature sensing suggests this device could be hitting 170C.
>>> No, we normally don’t test to these extremes.
>>> The PCB has ENiG finish and the solder is SAC.   This is normal SMT, no
>>> rework.
>>>
>>> I think I know in general what happened, but I am surprised.
>>> I don’t have an explanation for the formation of the big pocket on the
>>> right.
>>> Has anyone ever come across any solder joints like this?
>>>
>>> Thanks Steve for uploading the pictures (links below).
>>>
>>> http://stevezeva.homestead.com/pockets_25.jpg
>>>
>>> http://stevezeva.homestead.com/Pockets_CS.jpg
>>>
>>> http://stevezeva.homestead.com/Pocket-left.jpg
>>>
>>> http://stevezeva.homestead.com/Pockets-right.jpg
>>>
>>>
>>> Best Regards,
>>> Andy
>>> Andrew C. Giamis
>>> Senior Failure Analysis Engineer
>>> CommScope
>>> 2601 Telecom Pkwy
>>> Richardson, TX, 75082, USA
>>>
>>>
>>>