PM on white old simm memory connectors?

[Stowmaster]

What are the white metal used to cover 30-, 68-, 72-pins simm connectors on the old motherboard? Can be used rhodium or palladium? Or Ni/Ag only?

 

[jimdoc]

Tin

Jim

 

[Stowmaster]

Thank you, really tin -)))

 

[jimdoc]

Yes, search the forum if you don't believe me. I was disappointed to find that out as well. They still sell for the same price as the gold fingered ones, maybe the chips have more gold in them?

Jim

 

[Stowmaster]

Now I checked. Tin acid is hard to miss.

 

[a_bab]

Since it's obvious that the gold in these "tin sticks" must be hidden in the chips, and we have in average 1 pound of chips/2 pounds of sticks, that translates to more then 1g of gold/kg of such chips (2 kilos of ram sticks = aprox 4 pounds = aprox. 50$ value) - in theory.


On the other hand here in Europe these "tin sticks" are paid by half the price of the golden counterparts. It's easy to extrapolate that the value we can get from the ram fingers must also be found in the chips, at least by half. Since in average we can get 0.5 grams/kg of RAM (60 sticks in average), it's safe to assume the real gold content in the ram sticks must be AT LEAST 0,6 grams to 1 gram depending on the type.


In other words, the sums paid by the buyers must represent around 75% of the gold content, give or take 5%.
e-bay in exchange usually ranges from 100% to 150% or more. Not a good business for sure, at least to the buyer.

 

[etack]

I often wonder why cut ram is bought at a discount. tin ram is the same as cut ram.

Eric

 

[jimdoc]

I snapped a memory stick in half and one of the chips split with it, and it looked like a silver colored metal inside the chip.
It stuck to a hard drive magnet with a snap. I was told before that there is gadolinium in memory chips, so my guess is that is what it is. I will have to heat up that same chip and see if it is still magnetic above 68 degrees, that should give me my answer.

http://en.wikipedia.org/wiki/Gadolinium
Gadolinium is ferromagnetic at temperatures below 20 °C (68 °F)[3] and is strongly paramagnetic above this temperature. Gadolinium demonstrates a magnetocaloric effect whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field. The effect is considerably stronger for the gadolinium alloy Gd5(Si2Ge2).[4]

As with boards, it isn't only the gold that has value, especially in large quantities. Maybe it is gadolinium in the chips?

Jim

Edit;
I heated the chip up, and it is still magnetic, but maybe slightly less than before. Will have to look for a better way to test for gadolinium. I have some gadolinium in my element collection, and I seem to remember trying the magnet test with that.

 

[g_axelsson]

As this topic just faded out without any real answer I thought I would add some for any future reader.

The metal in the legs of ram chips is no different from other IC:s, it is copper, iron or an iron alloy (kovar). It is not gadolinium.

Gadolinium is a rare earth metal and a lot less common than gold. Gadolinium is mined at a rate of circa 400 tons/year while gold is 2500 tons/year. (Numbers pulled from a couple of google searches). Gadolinium is also sensible to humid environments and turns into a white oxide. In other words, gadolinium would be a very bad metal to use in such a high volume product as the legs of dram memory IC:s.

Göran

 

[jimdoc]

As this topic just faded out without any real answer I thought I would add some for any future reader.

The metal in the legs of ram chips is no different from other IC:s, it is copper, iron or an iron alloy (kovar). It is not gadolinium.

Gadolinium is a rare earth metal and a lot less common than gold. Gadolinium is mined at a rate of circa 400 tons/year while gold is 2500 tons/year. (Numbers pulled from a couple of google searches). Gadolinium is also sensible to humid environments and turns into a white oxide. In other words, gadolinium would be a very bad metal to use in such a high volume product as the legs of dram memory IC:s.

Göran

I wasn't talking about the "legs" of the chips, I was talking about the "inside the chip" metal.

Jim

 

[patnor1011]

Ag or AgPd alloy. That is your "white" part of inside of RAM IC Chip. It is usually on part where this metallic part is close to Si core.
Not in every IC. Some do have gold plating.
After number of different size batches of mixed RAM IC Chips I can say that I recovered about 0.8-1g of gold from bonding wires, another 0.2-0.3 from plating on pins where bonding wires were attached. I did not milled or crushed Si core as I collect them preferably intact however there may be another 0.X g left on sides or parts where wires were attached, well I will try to give them hot AR bath.

 

[g_axelsson]

Jim, the metal parts inside the chip is called a "lead frame". It is made of kovar, nickel-iron alloys, copper alloys or pure nickel. It is a continuous piece of metal from the pins into the bonding wires.
Surface treatments include silver, nickel, gold, or tin plated entirety or selectively.
Ag or AgPd braze isn't magnetic. If it is magnetic it is an iron or nickle alloy. Not gadolinium.
The only references I've found about gadolinium in memories is in bubble memory, and old technology from early 1980, and in experimental flash memories. No mentioning about it being used in dram and not as a pure metal.

Patnor1011, 0.8-1g but how much material did you start with?

For a good article on how a chip is built with alloys and techniques I recommend this one :
http://www.electroiq.com/articles/ap/print/volume-13/issue-4/features/the-back-end-process/die-attach-in-lead-frame-packages-step-4.html

Göran

 

[patnor1011]

Sorry Goran if I did not mentioned it. It was from one kilogram of RAM IC chips.
So my personal conclusion based on my experiments and observations is 1gAu/kg of (mixed different types of) IC RAM chips.