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ENIG or flash?

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ENIG or flash? | 27 November, 2006

Dear all,

I'm having a friendly discussion with our chief manufacturing engineer.

To our PCB suppliers we specify the use of "chemical gold", imo this means we use ENIG, Our boards are all copper under the solderresist which imo further confirms we are using ENIG. However, our chief ME keeps pursisting chemical gold is flash and our boards are all flash gold. He is in charge of all PCB related stuff, he should be the specialist.

So, now I'm turing to the real specialist for advice, who is right here? And if it is me (please let it be me), is there an internet paper which I can shove under his nose to confirm this?

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ENIG or flash? | 27 November, 2006

Never heard the term chemical gold before. I would recommend using industry standard tems first hehehe, what is the proces sfor these boards?

I would hope that you are using ENIG if you are soldering to these baords by the way


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ENIG or flash? | 27 November, 2006

Chemical gold is a poorly defined [very sloppy] term that means various thing to different people [as you've demonstrated]. Commonly it is either: * ENIG: 5�m Ni, 0.1�m Au * Immersion gold

"Autocatalytic chemical gold plating" - Refers to "electroless gold plating" methods, where gold plating is carried-out without applying external electrical energy to the aqueous solution. It is also refered to as substitution gold plating and autocatalytic electroless gold plating.

Look here for more:

We have no relationship, nor receive benefit from the company referenced above.

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ENIG or flash? | 28 November, 2006

Flash gold usually refers to electrolytic gold with a short plating time. In other words gold plating that requires current to plate. If you have bare copper under your soldermask, the gold is probably ENIG. The only other way to have bare copper under the soldermask is if buss bars were used to connect the circuit conductors to a current source. In other words, the electrolytic gold was plated after the soldermask operation. You would see buss bars or conductors running out to your circuit borders. There are some other options but this all adds lots of labor to the plating process. If you have gold underneath the soldermask, could be that the panel was plated with electrolytic flash gold and then the plated conductors were used in place of etch resist. This can be identified as a conductor that look like an upsidedown volcano or a mushroom as opposed to a volcano shaped conductor where resist was used.

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ENIG or flash? | 30 November, 2006

Thanks for the replies, it is getting clearer now. We called a PCB supplier and acted if we didnt know what was what, he actually told us its all the same, chemical, flash, immersion, all the same... It is now getting clearer why we are sometimes getting soldering issues with matte looking gold plating, I'll have to digg in a little further now.

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