There is ABSOLUTELY NOTHING wrong with the appearance of those solder joints. Even though a later if IAu was on a thin side, it did prevent E-Ni from oxidation,as a sound layer of intermetallics was formed.

It's definitely not Black Pad.‎ 

It could be though that there was touch of P in the layer.

Regards,

Vladimir
SENTEC

Sent from my BlackBerry 10 smartphone.
  Original Message  
From: Deng RongJun
Sent: Saturday, October 10, 2015 06:30
To: [log in to unmask]
Reply To: TechNet E-Mail Forum
Subject: Re: [TN] Solder joint peel off from ENIG board

Agreed with Joyce, the gold is too thin for Ni protection, minimum 0.05um in IPC-4552. This might cause "black pad" or affect solder joint strength, right?
Do you know which test can show correct P content in Ni layer? Is the rich P in between Ni layer and IMC layer?



RongJun Deng
Electronics Engineer
Design Link
BB Electronics (Suzhou) Co., Ltd., EMS - from idea to solution

Block E, No.58 Yangdong Road, Loufeng, Suzhou Industrial Park- 215122 Suzhou - P.R.China
Office: +86 512 6956 2880 - Direct: +86 512 6956 0125 - Fax: +86 512 6715 7266
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Friday, October 09, 2015 11:37 PM
To: [log in to unmask]
Subject: Re: [TN] Solder joint peel off from ENIG board

opps, Many thanks for Wayne to point out. I did calculation mistake. 
0.038 micron is 1.5 micro-inches. still thin. my apology... getting really old.
jk
>
Concur, IMHO, below 2uin, and depending on it's porosity, Au is unlikely
> to protect the Ni from passivating. A traditional spec would be on 
> the order of 6 +/- 4uin with suppliers typically shipping at between 2 
> and 3uin..
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
> Sent: Friday, October 09, 2015 5:53 AM
> To: [log in to unmask]
> Subject: Re: [TN] Solder joint peel off from ENIG board
>
> does not like to have that much gold... 0.038 micron is less than 1 
> micro-inch of gold. you might have Ni oxide on surface to prevent 
> good joint... you might also have some Cu oxide on the surface, if 
> your Ni plating is crappy and porosity is high... can't see picture... 
> did you buy cheap? (based on the amount of gold you are having).
>> EDS doesn't normally show the correct P content you begin with.Ã,
>>
>> I can not see any images.
>>
>> ââ,¬Å½Regards,
>>
>> Vladimir
>> SENTEC
>>
>> SentÃ, fromÃ, myÃ, BlackBerryÃ, 10Ã, smartphone.
>> Ã,  Original Message Ã,
>> From: Deng RongJun
>> Sent: Friday, October 9, 2015 10:13
>> To: [log in to unmask]
>> Reply To: TechNet E-Mail Forum
>> Subject: [TN] Solder joint peel off from ENIG board
>>
>> Hi all:
>>
>>
>> I have got a solder joint strength issue on ENIG board, the cables 
>> soldered on board can be easily detach from pads by a small external 
>> force(1kg), the cable mounting process is hand soldering. Failure 
>> rate is about 20%.
>>
>>
>>
>> We have made SEM and EDS test for solder joint and peel off surface, 
>> P Wt% is high than normal. And we have also made SEM test for 10pcs 
>> bare board, the Au thickness is 0.038-0.05um, Ni thickness is 2.8-4.0um.
>>
>>
>>
>> As I know high P Wt% will affect solder joint strength, what issue is 
>> happened during PCB fabrication process? Anybody know anything about 
>> this?
>>
>> Here comes pictures:
>> http://pan.baidu.com/s/1sjl7Ynb
>>
>> Best regards
>> Deng
>>
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