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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Au Plating

Jacob Lacourse

#20126

Au Plating | 29 May, 2002

Hi, All

Our board design requires us to selectively plate some connector pads with gold. The problem is we have changed board houses and they charge a heafty amount to mask the rest of the board. One option is to allow them to plate the whole board. I was wondering if anyone could tell me if there is a down side to doing this. We are currently using a water soluable paste with a 63/37 composition. Thanks Jake

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RDR

#20130

Au Plating | 29 May, 2002

If Gold gets to thick you will end up with brittle joints that break! Hard gold plating is usually about 50 microns thick (is that right?) whereas gold immersion is around 7-13 from what I have seen. i once use gold plating on an entire board and had many reliability issues.

Russ

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#20134

Au Plating | 29 May, 2002

Russ is spot on!!! [Although, he maybe talking uin rather than micron.] Search the fine SMTnet Archives for more.

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ianchan

#20157

Au Plating | 31 May, 2002

why not use "flash Au plating"?

its supposed to be somewhere in the thin layers of 3-5um Au thickness... then again I never used it before either, might want to check with your original parts supplier is this feasible?

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RDR

#20159

Au Plating | 31 May, 2002

uin. would be correct sorry about that chief.

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#20171

Au Plating | 31 May, 2002

'Flash' is too thin to bear the traffic of most wear surfaces like Jake is talking about. Follow-up with the fretting corrosion discussion over on the current [Jim Zanolli / Teka] OnBoard forum.

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ianchan

#20180

Au Plating | 3 June, 2002

Fair greetings,

just a thought on flash gold plating... stubborn brat am I?!

thou shalt need to know whether the selective gold plating is for solderability enhancement purpose? or any other undisclosed purpose? at least thy hast not received any information to thine Au plating purpose?

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#20181

Au Plating | 3 June, 2002

Selective plating is exactly what Jake is complaining about as being too expensive.

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ianchan

#20185

Au Plating | 3 June, 2002

Ok let's start backwards abit, and move progressively from a common understanding.

So this originator thread-slinger bloke is asking for advise to Au plate his connector pads.

We have a cuppa ideas bounced around which leads to my ignorance based question : "why is flash gold not going to work?". General comment is: Coz flash Au is too "thin to bear traffic" and currently may qualify as a valid point.

However this leads to another question, is this thread-slinger bloke intending to have Au plating as part of his solderbility ehancement programme? or is there some other reason why he wanted to have Au plating on em' connector pads? am trying not to "ass-u-me" here.

Yep, sure we know selective Au plating is expensive. For my case I juz wanna know why flash plating is not going to work?

in my "dis-orientation" state, I cannot see how "thin Au flash plating" is not acceptable unless the root reason for Au plating is to enhance solder adhesion to connector pads that dislike solder?

PS: do not intend any disrespect to anyone's opinion, juz trying to master my navigation points through this crazy constant-evolution world. If I express error, pls guide me along with your wisdom. Cheers!

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#20210

Au Plating | 4 June, 2002

First, �flash gold� is very loose language. It means different things to different people.

�Flash� gold is a thin coat of immersion gold. Imm gold self-limits at ~0.3um[12uin]. And fabs put-down �flash� prior to electroplating thicker gold for wire bonding or wear surfaces. So, this flash is as thin as 1uin in many cases.

IPC-2221 says something like ... For edge connectors and areas not to be soldered: * Nickel - 2.5um [~100uin] min [Class 2 & 3]. * Gold - 0.8um [~30uin] min [Class 2], 1.3um [~50uin] min [Class 3].

Further, we have discussed thickness of gold that are required for different amounts of wear, here on SMTnet. Search the fine Archives.

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