Carlos,

It may or may not be the same thing but I once went through an issue
where gold tabs were visually fine, and were passing tape test at the
raw PCB inspection level, only to peel up in reflow during assembly. We
were able to peel the blisters partially off and expose large areas of
the interface where the delam occurred.  XPS analysis shows both
surfaces to be NiOH and H2O. Our theory was that there might have been a
porous nickel finish that was able to absorb water (from a rinsing
operation?), and the water boiled off during reflow causing the
blisters.

We never proved out theory for sure however.

A

Andy Heidelberg
Quality Assurance Engineer
Micron Custom Manufacturing Services
208-898-2784
[log in to unmask]


>----------
>From: 	Michael Barmuta[SMTP:[log in to unmask]]
>Sent: 	Friday,July 25,1997 3:40 PM
>To: 	[log in to unmask]
>Cc: 	[log in to unmask]
>Subject: 	Re: Gold peel after solder level
>
>	Carlos: I've seen this same type of adhesion problem after I.R 
>fusing. Depending on which interface is failing Au to Ni or Ni to Cu the 
>causes are different. Without knowing what your process chemistries and 
>sequences are for Sn strip,activation,and Deep/Tab Ni-Au electroplate I'll 
>take a couple of guesses. If the failure is Ni to Cu and you're using a 
>non-fluoride/peroxide Sn strip such as a nitric based system an intermetallic
>could be left behind. This could give you a sufficient enough bond of the 
>plated Ni to Cu to pass a tape test after plate but when subjected to the 
>thermal shock and stresses of HAL the Ni/Cu bond could be degraded. This 
>would result in a failure in a post HAL tape test. If the failure is Au to Ni
>I would suspect more of a passivation problem with the Ni or incorrect entry 
>amperage into the Au electroplate causing the adhesion problem after HAL.	
>									
>There's a long list of possible problems and solutions for "gold peelers" but
>the key piece of information in your problem is it's happening only after HAL
>and passing the post plate tape test fine. More information on the 
>type/severity of failure and additional process information would help to 
>further pinpoint the problem. You may also want to make sure the tape test is
>being conducted the same at both test areas. Old tape, incorrect type of 
>tape, technique of application and removal can all affect the results of the 
>test									
>						Regards			
>							Michael Barmuta	
>							Staff Engineer	
>							Fluke Electronics	
>							Everett Wa.	
>							425-356-6076  
>On Fri, 25 Jul 1997 09:50:24 -0700 [log in to unmask] wrote:
>
>> From: [log in to unmask]> Date: Fri, 25 Jul 1997 09:50:24 -0700
>> Subject: Gold peel after solder level
>> To: [log in to unmask]
>> 
>>      Hello!
>>      Has anyone experienced Deep or Tab gold plate passing tape test at the
>>      precious metal process, only to have gold peel after the Hot Air 
>>      Solder Level process.
>>      
>>      Thanks
>>      
>>      Carlos
>> 
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>
>
>
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