Nickel-gold plating a whole board

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When I was a graduate student, the professor of dental science separated from his wife and moved into the graduate student and visting scholar accomodation, and during that period I got hit in the face by a field hockey stick, and he guided me through the dental hospital's emergency services. I wouldn't say that we bonded, but I did get to hear odd stuff about dental alloys - they can have application in scientific instruments ...

The crowns at the front of my mouth have a ceramic cap - zirconia according to the dental student who put it in. The "see and be seen" brigade apparently now go in for setting a small - facetted - diamond into the visible face of their crown. I've yet to see one in real life.

They shouldn't corrode, but the tooth surface they are supposed to be protecting can be subject to decay.

Titanium really does ankylose. I've certainly not had any infections between the implant and the bone. Thirty years ago it was a different story.

-- Bill Sloman, Nijmegen

Joerg > If the gold price keeps climbing at the Joerg > current rapid pace maybe some Joerg > day they'll stop complaining :-)

I too was scratching my head about the UNWANTED solder and gold alloy.

I don't handle much gold but cleaned out some of the scrap metal in my garage and was amazed at what the scrap yard paid for copper.

Somebody told me that pollution regs made copper mining in the USA too much of a pain so now we buy copper from China.

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.

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.

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

-Lasse

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

Thanks, very good to know.

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

I'm finding gold plating a little bit more difficult to solder by hand than tinned board.

I have not tried hand soldering with ROHS solders yet. All the hand soldering we do so far is good old Kester 44 (activated rosin flux) Sn63Pb37 lead solder. We're exempt in many cases anyway because of the nature of the applications.

What's your experience with ROHS hand soldering? Aside from it looking dull- is it more gummy than the eutectic SnPb alloy?

The few times I had to do it the gold pad acted like a Labrador puppy. They literally inhale their food. Slurrrrrp ... gone.

NONE of ours are gold plated, except for the rare edge fingers (used for test fixtures). That part of the process has been no problem at all.

Boy, are you in for a surprise. I just refuse. I let our tech do the soldering on production stuff. If they want me to do it, it's going to use lead.

It's *terrible*. Even done by the best technician, it looks bad. Use *lots* of good flux!

I still solder mostly with SnPb since the most soldering I do is prototypes.

Soldering with 'pure' Sn is a bit harder than SnPb. The temperature of the iron and the tip size must be exactly right. The flux seems to wear off faster so you have to work quicker. Other than that its the same as soldering with SnPb.

...except that the solder doesn't flow (or wick), and the joint looks colder than hell even when it's perfect.

In that case your iron was probably to hot or too cold. I have no problem soldering multiple pins simultaneously on a 0.5mm pitch LQFP with a 3mm (0.12") chisel shaped tip without making shorts. Like I said: the right temperature and enough flux are essential. A good lead-free joint looks only slightly duller than a SnPb joint.

Ages ago ('70s or so) HP made their boards gold plated; even SexTronics did that. Problem is, many years later whisker problems (AKA "tin pest") cropped up at the solder end of the cathode wire of aluminum electrolytics, causing intermittents at minimum.

Furthermore, some ladies handling gold plated parts may leave etched fingerprints and a greenish growth on the gold during certain times of their period, proving that gold can corrode underrr the right conditions. .

Wrong. The "corrosion" was the medium left behind from her prints, and that was ALL. It attacked the Gold not one iota. It merely sat there on the surface. I guarantee it. Same thing for Platinum.

Sorry, but you are wrong.

Corrosion in mild acid indicates gold that's thin enough to be porous, or that doesn't adhere well, or that's alloyed, or that doesn't have good surface coverage of the base metallization. I bet those ladies' wedding rings don't leave green goo on their skin.

Otherwise you can dissolve it in aqua regia which is a mixture of conc HCl and conc HNO3, a similar mixture of HF and HNO3, KI/I2 solution, or sodium or potassium cyanide, and you can RIE it (very slowly).

Everything else, it ignores.

Cheers

Phil Hobbs