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SMT electronics assembly manufacturing forum.


Electroless Nickel/Gold finish

Geertjan de Beijer

#5975

Electroless Nickel/Gold finish | 17 April, 2001

My name is Geertjan de Beijer and I am new on this forum. I have a question about Electroless Nickel/Gold finishes.

Until now we always use a HAL finish on our PCB's. Since we are using compontents with pitches of 0.5mm we notice that the HAL finish isn't flat enough and our PnP assembler complained about that. Our PCB manufacturer advised us to use a Electroless Nickel/Gold finish. We don't have any experience with this and we wan't to know if we can expect some problems in our production process.

Can anyone tell me more about this.

With kind regards,

Geertjan de Beijer gdebeijer@adimec.nl

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#5981

Electroless Nickel/Gold finish | 17 April, 2001

Welcome to SMTnet.

Awww, those assemblers are always whining about something. Just tell him to shut-up and build the blankin� boards. Jeesh!!!

We used to have copious archives on the topic on SMTnet and our friend Brian is working his fingers to bloody stubs figuring-out how to convert them from the older format, but until then the paltry 30 or so threads will be a good point to start.

As you would suspect, the ENIG solderability protection that your supplier proposes is going to make board assembly a wonderful place, tulips won�t be eaten by the deer before they blossom, and the bartenders will start cleaning the glasses down at Jimbo�s. Yippie!!

As with all things, the good brings bad and you just have to balance the trades. As a starting point in understanding those trades, go to http://www.merix.com/, goto the Resource Center, and find "Comparison of Electroless Ni/Immersion Au vs. Electrolytic Ni/Au" and "Alternatives to HASL: Users Guide for Surface Finishes" These papers are fairly unvarnished and will be a good starting point for our conversations.

Ask your supplier to explain the issues surrounding black pad in ENIG, report back, and we'll talk.

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genny

#5982

Electroless Nickel/Gold finish | 17 April, 2001

Hi, ENIG finish is the same reason I came to this forum for the first time a few months ago. I found a bunch of useful information by searching the archives. Check it out. ENIG has some good properties like flatness, and the process control has improved in recent years with a lot more companies using it, but one of the biggest concerns is something called 'black pad'. If the nickel gets oxidised before the gold plates on, the gold won't bond properly to the nickel. Then when components get soldered to the board, they can sometimes be flicked off very easily leaving a black pad behind. Most board vendors can test for this before it gets to the component installation stage, by doing a tape test. Also, the reflow temperature must be properly controlled so that a true intermetallic bond can be formed. If not, only a tin-gold bond may form which is quite brittle. That's a quick summary of what I learned.

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PCB contract manufacturer