that Alpha report sure does hold alot of information....

what we clearly need to understand is the following:

a) if the EN bath is operated at it's optimum condition..the bath will deposit an 8-10% phos in the nickel.

b) as metal turnovers are created in the plating process; if    you have the know-how; it is quite simple to create a 
   device which will measure the actual bath electro-   potential. as the bath ages; the electro-potential decreases - this then can be correlated back to - thickness and deposit  purity and phos content

c) the electro-potential of the bath will be affected by metal    turnovers - due to organic build-up in by-product - thus the 
   pH must be adjusted

In their report Alpha states that the gold baths are highly acidic - this is incorrect - IG baths operate somewhere in the area of 4.8 - 5.1 pH, and there is nothing like a minimally corrosive gold bath.

Exert from their report:

5. Discussion and Conclusions 

In our extensive investigations we have accumulated a very strong body of evidence to support the hypothesis that the 'Black Pad' phenomenon is very likely the result of a number of plating and subsequent assembly process parameters working in concert to produce a very perplexing failure mechanism. This mechanism is seemingly very random in nature and usually fairly difficult to confirm without full knowledge of the materials, processing parameters, and service environment conditions involved with the failed connections. More often than not, destructive testing of a fair number of samples is required to gather the necessary evidence to identify this type of failure. It appears that the formation of a P rich layer at the surface of the EN plating is at the root of the failures. The P rich layer can begin to form during IG plating and lead to poor connection formation at the time of soldering. It can also begin or continue to form as a result of Ni-Sn IMC growth during thermal excursions in the processing, assembly, and service life of the product, resulting in the weakening and premature failure of the connection. 

Longer Term Solutions - Plating Parameters 


  1.. 1. Reduce the P content in EN coating (7-11%P has been analyzed on materials exhibiting no such failures) [5]. Usually a minimum of 9.5%P has been recommended for good corrosion resistance [1] 


  2.. 2. Minimize metallic and organic plating solution contamination from drag-in or other sources [1,3] 


  3.. 3. Maintain proper vendor specified plating parameters for good bath control (pH, chemistry, and temperature) [1] 


  4.. 4. Assure EN coating is active/solderable immediately prior to applying subsequent protective soluble coatings [5]. 


  5.. 5. Deposit protective gold coating from a minimally corrosive neutral gold bath [8] 
  All that they have stated is exactly what I had previously stated; if the board is not processed properly before the OEM receives it; further complications will arise in populating them. The whole difference between a good batch of boards and a a batch with major complications can be something as minute as the pH.



  Rick Fudalewski

  Target Technology





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