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Nickel-gold plating a whole board

J

Joerg

Jan 1, 1970
0
Hi Folks,

Anyone familiar with soldering issues on a Ni-Au plating like this? The
usual ENIG.

http://en.wikipedia.org/wiki/Gold_plating

Thing is, for the mounting holes gold plating would of course be good
because solder tends to creep away and the connection could loosen. It's
a thru-hole board, wondering how the solder bond qualities will be with
gold plating, versus the usual solder-plating.

It'll be assembled with leaded solder, not RoHS. Initially hand
soldered, later maybe wave-soldered.
 
J

Joerg

Jan 1, 1970
0
Dave said:
When I worked on the avionics and cal lab benches at the Navy base in
Jacksonville, FL, we had tons of equipment failures that were easily traced
to mechanical joint failures caused by brittle solder-gold contact. The
gold on the component leads would delaminate and leave the leads floating
open or intermittent inside the soldered connection.
As a result, the microminiature soldering training program there issued a
requirement that on all repairs requiring replacement of a component having
gold plated leads, the leads must be tinned with solder, then the solder
wicked off with a fluxed braid or dipped into a solder pot several times to
leach all the gold from the leads.
I remember that a lot of HP equipment having Ni-Au plated boards had this
problem, resulting in a lot of the older equipment going to the salvage yard
to avoid the cost of troubleshooting and repair.

Oh-oh, that doesn't bode well then. The gold is nowadays extremely thin
so wouldn't likely saturate anything. But who knows, I sure don't want
to see a repeat of that HP issue.

My favorite would be nickel-only but they don't seem to do that anymore.
So that would make it a boutique process.
 
J

Joerg

Jan 1, 1970
0
Artemus said:
Have you looked at IPC-4552?


Sure, and it talks about solderability and all that:

http://www.circuitexpress.com/pdf/IPC-4552IF ENIG Spec.pdf

However, statements like these (page 17, under aging) didn't exactly
instill confidence in me, quote "These samples were now 240 plus days
old since plating, (I knew there was a reason I don’t clean my office)".

Now the gold layer thickness these days is in the tens of nanometers.
Not sure if the HP boards Jeff was mentioning had much thicker gold. If
you have too much gold dissolving into the solder then all sorts of evil
things can happen.
 
T

TTman

Jan 1, 1970
0
Joerg said:
Hi Folks,

Anyone familiar with soldering issues on a Ni-Au plating like this? The
usual ENIG.

http://en.wikipedia.org/wiki/Gold_plating

Thing is, for the mounting holes gold plating would of course be good
because solder tends to creep away and the connection could loosen. It's
a thru-hole board, wondering how the solder bond qualities will be with
gold plating, versus the usual solder-plating.

It'll be assembled with leaded solder, not RoHS. Initially hand
soldered, later maybe wave-soldered.

For mil/aerospace stuff, we de-guild everything... I guess you can't do
selective gold then....
 
S

Spehro Pefhany

Jan 1, 1970
0
Hi Folks,

Anyone familiar with soldering issues on a Ni-Au plating like this? The
usual ENIG.

http://en.wikipedia.org/wiki/Gold_plating

Thing is, for the mounting holes gold plating would of course be good
because solder tends to creep away and the connection could loosen. It's
a thru-hole board, wondering how the solder bond qualities will be with
gold plating, versus the usual solder-plating.

It'll be assembled with leaded solder, not RoHS. Initially hand
soldered, later maybe wave-soldered.

Have had no problems with a number of batches (SMT reflow + a few
parts hand soldered, Sn63Pb37). Gold got a bad reputation because they
actually used to put some on, now that the dollar is worth 5.5E-4 oz
of gold, it's just a protective layer on the nickel.
 
J

Joerg

Jan 1, 1970
0
Phil said:
There are gold intermetallics, but that's what's supposed to happen.
Gold boards are the bee's knees for solderability. Use 2% silver solder
to protect the gold if you feel a need.

This has to work with regular leaded solder. So you think ENIG for the
whole board will be ok then?
 
J

Joerg

Jan 1, 1970
0
Spehro said:
Have had no problems with a number of batches (SMT reflow + a few
parts hand soldered, Sn63Pb37). Gold got a bad reputation because they
actually used to put some on, now that the dollar is worth 5.5E-4 oz
of gold, it's just a protective layer on the nickel.

$1,782 per ounce yesterday. Depressing :-(

That's what I thought, maybe HP had the really lay it on there. Nowadays
you get 50 nanometers or so. Like whatever flakes off of a nugget flying
across the fab at supersonic speed.

I don't even want to think about what the next gold crown will cost
should I ever need one ...
 
J

Joerg

Jan 1, 1970
0
TTman said:
For mil/aerospace stuff, we de-guild everything... I guess you can't do
selective gold then....

Unfortunately I can't on this one, it's either all ENIG or none of it.
 
F

Fred_Bartoli

Jan 1, 1970
0
Phil Hobbs said:
There are gold intermetallics, but that's what's supposed to happen. Gold
boards are the bee's knees for solderability. Use 2% silver solder to
protect the gold if you feel a need.

Cheers

Phil Hobbs

IIRC the problematic phase exists only above 0.8% gold content, which won't
happen with ENIG ultrathin 0.2um plating. All the surface gold gets easily
dissolved, so no pb with the intermetallics transition, and no pb with the
joint too thanks to the very low gold content.

I've a customer that uses exclusively ENIG process for his sensors (SMDs
down to 0201) with no pb at all 'til now.

No pb with refusion SMDs, but the solderwave guys don't like gold plated
boards because that makes gold concentrating over time, rendering their bath
unusable.
 
J

Joerg

Jan 1, 1970
0
Phil said:
There are a whole lot of gold plated boards out there, and have been for
a long time. I suspect that the Navy problem was something unusual, e.g
massive temperature cycling.

Good to know that there's a lot of those boards out there. Once
assembled it becomes impossible to see because the solder will have
eaten up the ENIG gold layer. It's more of a whiff than a layer.
 
F

Fred_Bartoli

Jan 1, 1970
0
Fred_Bartoli said:
IIRC the problematic phase exists only above 0.8% gold content, which
won't happen with ENIG ultrathin 0.2um plating. All the surface gold gets
easily dissolved, so no pb with the intermetallics transition, and no pb
with the joint too thanks to the very low gold content.

I've a customer that uses exclusively ENIG process for his sensors (SMDs
down to 0201) with no pb at all 'til now.

No pb with refusion SMDs, but the solderwave guys don't like gold plated
boards because that makes gold concentrating over time, rendering their
bath unusable.

IIRC, I found that documented on Xilinx site, in some appnote about fine
pitch BGAs

 
J

Joerg

Jan 1, 1970
0
Fred_Bartoli said:
"Fred_Bartoli"

You don't even get as much as 0.2um anymore these days.


If the gold price keeps climbing at the current rapid pace maybe some
day they'll stop complaining :)
IIRC, I found that documented on Xilinx site, in some appnote about fine
pitch BGAs

Thanks, guys, that helps me a lot. Looks like we can go the ENIG route
then. It also makes the board look rather posh but that's not the reason.
 
S

Sergey Kubushyn

Jan 1, 1970
0
Dave M said:
When I worked on the avionics and cal lab benches at the Navy base in
Jacksonville, FL, we had tons of equipment failures that were easily traced
to mechanical joint failures caused by brittle solder-gold contact. The
gold on the component leads would delaminate and leave the leads floating
open or intermittent inside the soldered connection.
As a result, the microminiature soldering training program there issued a
requirement that on all repairs requiring replacement of a component having
gold plated leads, the leads must be tinned with solder, then the solder
wicked off with a fluxed braid or dipped into a solder pot several times to
leach all the gold from the leads.
I remember that a lot of HP equipment having Ni-Au plated boards had this
problem, resulting in a lot of the older equipment going to the salvage yard
to avoid the cost of troubleshooting and repair.

It is not just that it delaminates. There is more :) Gold makes brittle
intermetallic alloys with solder that are prone to cracking. That is why
there are special solders for soldering gold. In50/Sb50 e.g. one of those
solders and I do even have a roll...
 
J

Joerg

Jan 1, 1970
0
John said:
We do a few of our boards that way, specifically boards that have BGAs
and must be ROHS. The surface is very planar, so BGAs like it.

You have to practically lock the boards and solder in separate rooms;
the solder almost leaps onto the boards. The gold is only around 10-15
micro-inches, so it quickly dissolves into the solder. That leaves the
solder sticking to the nickel, which I don't really understand.

But it works great, and the bare boards look cool.

ftp://jjlarkin.lmi.net/Gold_T564.jpg

Yes, it looks like a million Dollars. I also have two SMAs on there,
gold plated.

The solder up there at Y1 on your board looks very shiny. If it was
gold-choked it would look dull and cracked. Well, I just fired it all
off, we'll get golden boards out of Colorado.
 
T

TheGlimmerMan

Jan 1, 1970
0
As far as I know, all my crowns are chrome-cobalt alloy.

Doubtful. Both that you would know and that it is anything other than
basic stainless.
It doesn't
make them cheap.

Platinum would have been the right choice, if you are trying to do the
"see and be seen" thing.
I don't think I've ever needed to have one replaced.

Other than having one knocked loose, why would one need replacement?
They do not corrode. Unless you got tin.
There's also a titanium implant,

All of them are Titanium.
put in (at their cost) when the
dental hospital made a hash of doing a crown and post restoration on
my lower left canine, but that goes down into the jaw-bone.

Damn those antibiotics!
 
N

Nico Coesel

Jan 1, 1970
0
Joerg said:
Hi Folks,

Anyone familiar with soldering issues on a Ni-Au plating like this? The
usual ENIG.

AFAIK most SMT boards are already completely gold plated! Tin plating
(HAL) is usually not good enough for automated assembly + soldering of
SMT components.
 
J

Joerg

Jan 1, 1970
0
Nico said:
AFAIK most SMT boards are already completely gold plated! Tin plating
(HAL) is usually not good enough for automated assembly + soldering of
SMT components.

I got quotes and made a production decision yesterday. ENIG does add
cost but surprisingly little.
 
S

Spehro Pefhany

Jan 1, 1970
0
I got quotes and made a production decision yesterday. ENIG does add
cost but surprisingly little.

Consultants like to come up with gold-plated designs. ;-)

Actually, we've been using it pretty much exclusively for some time
(except for some prototypes and small volume items). I have not seen a
significant downside yet, at least in small to moderate volumes.
 
J

Joerg

Jan 1, 1970
0
Spehro said:
Consultants like to come up with gold-plated designs. ;-)

I can't wait to see their reaction when they unpack it :)

Actually, we've been using it pretty much exclusively for some time
(except for some prototypes and small volume items). I have not seen a
significant downside yet, at least in small to moderate volumes.

Thanks, very good to know.
 
J

Joerg

Jan 1, 1970
0
even the cheap proto pcbs from olimex are with gold, though they do
mention
that if you do not have soldermask it will be more expensive because
of
added the gold

don't think I can't remember using a board in the last 10 years that
didn't
have gold, I think for BGAs and the likes gold and chemical tin is the
only
options that are flat enough

I've had lots of boards without gold. But I sometimes do consumer stuff,
occasionally it's even ported to <gasp> phenolic. Every penny gets
turned around and around ;-)
 
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