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Gold Thickness

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kehoem@bellsouth.net

#42047

Gold Thickness | 9 June, 2006

We have a board calling out for 50 micro-inches of nickel over 30 micro-inches of gold. This is a solid gold board on Rogers material.

ENIG cannot be deposited that thick right? Electroplated gold (we thought) was usually 35-50 micro-inches and was usually applied to gold fingers, not smd pads. Am I reading this right? Can electroplated gold be used at 80 micro-inches thick and be soldered to??

mk

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Rob

#42049

Gold Thickness | 9 June, 2006

I know it's friday afternoon, and it's actually hot for once in this country, so my brain may not be working properly here, but isn't 30 micro inches of gold about 0.75 Microns? So that's dead in the middle for gold plating thickness (like gold fingers on pcb edges)?

Do you think it's possible that your customer has got his units mixed up & actually means 0.3 micro inches of gold over 0.5 micro inches of Nickel?

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kehoem@bellsouth.net

#42053

Gold Thickness | 9 June, 2006

Question; Do you think it's possible that your customer has got his units mixed up & actually means 0.3 micro inches of gold over 0.5 micro inches of Nickel?

That is what I said but their vendor says they are building to print which says 80 uM and it is not a card edge connector. This is a smd design that gets components soldered to it.

My confusion comes from my old days (many years removed) in the board shop plating gold tabs/fingers. Any surface or body gold we used to call it, was always EniG and not very thick. Gold tabs at the standard thickness were not used for soldering. Would solder stick to 80 uM of gold over nickel?

Still confused! mk

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Rob

#42054

Gold Thickness | 9 June, 2006

Yes you can solder on to it - just tried it with some 0603's across some gold fingers with tin lead paste & a heat gun. Don't know how many times you could rework it though.

Any chance you could get hold of an aold populated board from your customer to check it out?

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#42059

Gold Thickness | 9 June, 2006

You can not solder to 30 micro inches of gold over nickel and certainly not 80 microns. You can not with tin lead solder or SAC305 anyway. The upper limit is between 6 and 10 micro inches of gold. This is what ENIG plates to. If you solder to greater than 10 micro inches of gold with standard alloys, you will have gold imbrittlement of the solder joints. You might be able to get by hand soldering to thicker gold but not SMT. Hand soldering to gold tends to draw some of the gold to the iron tip and out of the solder joint. This is why the old Mil Spec used to say solder once to the gold pad, wick it clean, and then solder the lead wire on.

Unless you are using 80/20 Gold/Tin paste or Indium/Lead paste, you must avoid soldering to gold pads with greater than 10 micro inches of gold plating. You will have weak solder joints if you solder to gold that is 30 micro inches thick.

Chris

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RDR

#42067

Gold Thickness | 9 June, 2006

i agree with Chris

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mkehoe@sipad.net

#42097

Gold Thickness | 12 June, 2006

Can someone look this over and see if this helps?? ******************************************************

I read the e-mail threads and I think the respondents are all mixed up on the units of measure.

the print reads: Gold Plate (80 mocroinches min) over Nickel Passivation layer.

80 microinches = 2.032 microns = 2.032 micrometers (uM)

Is it possible that the measurement was mis-interpreted,, the 80 microinches for 80 microns. 80 microns would equal 3149 microinches.

Let me know what you think.

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