Silver coloured fingers
- Thread starter bodger
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bodger:
I'm kinda new here myself, been a lurker for a wile though.
I beleve here on the forum someware that the silver colored fingers were determined to be tin or tin alloy.
Someone correct me if i'm wrong. Any silver content ?
Ray
I'm kinda new here myself, been a lurker for a wile though.
I beleve here on the forum someware that the silver colored fingers were determined to be tin or tin alloy.
Someone correct me if i'm wrong. Any silver content ?
Ray
wop1969
Well-known member
Sodbuster said:
I will say, without 100% garentee it might be tin, as tin is very corrsion resistant.
Most probably tin. In rare, rare, rare cases, rhodium.
Juan Manuel Arcos Frank
Well-known member
Yeah...It seems tin...the good news is that they are RAM memories..they worth as spare parts better than recycling.
Regards.
Manuel
Regards.
Manuel
goldsilverpro said:
Have you ever seen rhodium plated memory fingers? What benefits would it have over gold plate?
For a simple test, just rub it with a piece of writing paper or a white envelope. Tin is soft and paper often contain minerals (limestone) as filler material and rubs off some tin.
If you get a black streak it is tin.
This test works well on other tinned surfaces, for example silvery colored pins.
I have seen Rh plated fingers. In fact, I have actually plated fingers with Rh. The company I worked for sold the best Rh plating solutions in the industry and I plated lots of samples for large electronic companies that were interested in converting from Au to Rh. I think that Zerox was one of these companies. This was way back in about 1970 or 1971. At least 2 companies did convert to Rh for a year or two.
Why they did this, I don't exactly remember. Most probably, it was because they could get away with much thinner deposits, due to the extreme hardness of Rh. The thin Rh would wear much better than the thicker soft gold. I think it all stopped when they found that Rh and other PGMs tend to act as a catalyst to polymerize organics from the air, after a period of time, and this produced an undesirable thin non-conductive coating on the surface which was light brownish in color. After the boards had been in service for awhile, you could ball up this coating and move it around with a pointed tool. This was very visible under a scope. It reminded one of rubber cement. Of course, this would wreck havoc at the points of connector contact.
At that time, large computers utilized "memory disks." These were large record-shaped aluminum disks about 1/4" thick. Some were as large as 3 or 4 feet in diameter. They were first plated with a magnetic coating of electroless nickel or cobalt. On top was a thin protective layer of plated Rh (although some companies used hardened gold plating). The same thing happened. When they discovered this polymerized organic thing, they had to come up with something different. My first partner in the plating business had formerly owned a memory disk manufacturing company. I met him while troubleshooting his Rh plating problems.
There are always rumors that some more modern fingers are Rh (or other PGMs) plated. This was discussed several times in the early days of the forum. I would doubt that these rumors are true, due to the reason given above.
To test for the indication of PGM plating on anything, I would probably first look for this organic coating with a tool and a scope. Also, fresh Rh plating often has a bluish cast. Rh plating will break up into a jillion bright shiny slivers when the underlying metal(s) is dissolved in nitric.
Why they did this, I don't exactly remember. Most probably, it was because they could get away with much thinner deposits, due to the extreme hardness of Rh. The thin Rh would wear much better than the thicker soft gold. I think it all stopped when they found that Rh and other PGMs tend to act as a catalyst to polymerize organics from the air, after a period of time, and this produced an undesirable thin non-conductive coating on the surface which was light brownish in color. After the boards had been in service for awhile, you could ball up this coating and move it around with a pointed tool. This was very visible under a scope. It reminded one of rubber cement. Of course, this would wreck havoc at the points of connector contact.
At that time, large computers utilized "memory disks." These were large record-shaped aluminum disks about 1/4" thick. Some were as large as 3 or 4 feet in diameter. They were first plated with a magnetic coating of electroless nickel or cobalt. On top was a thin protective layer of plated Rh (although some companies used hardened gold plating). The same thing happened. When they discovered this polymerized organic thing, they had to come up with something different. My first partner in the plating business had formerly owned a memory disk manufacturing company. I met him while troubleshooting his Rh plating problems.
There are always rumors that some more modern fingers are Rh (or other PGMs) plated. This was discussed several times in the early days of the forum. I would doubt that these rumors are true, due to the reason given above.
To test for the indication of PGM plating on anything, I would probably first look for this organic coating with a tool and a scope. Also, fresh Rh plating often has a bluish cast. Rh plating will break up into a jillion bright shiny slivers when the underlying metal(s) is dissolved in nitric.
