Old School Ram

[rmi2416]

Hey again guys,
Want to start off saying that I joined a little bit ago and so far the amount of information here is amazing and the people that make up this forum are something great. Thanks.
Back to my ?
I have some old ram sticks 88-94is maybe they have all silver colored contacts on back and on the fingers. Now I am still waiting on some acids in the mail so I cant test to see what one of them dissolves in but even if it is silver it still will dissolve in some basic nitric acid from what I have learned.

Does anybody have any clue as to what the PM here is if any. These dont seem to get higher than 16megs you know back when 112 was OMG
Pics included

 

[Claudie]

I think those fingers are tin, not silver. They say that if you rub the finger on a piece of paper and it leaves a streak behind, it's probably tin.

 

[element47]

The purpose of gold on those fingers is to prevent corrosion in air that would possibly make the connection at the socket flaky. I have never seen *any* such fingers where the gold plating was tinned, eg, soldered over. If the mfr's intended finish surface was solder, then there's little sense to them tinning over the extra-cost gold plating. So if what you see isn't gold, I'd be skeptical of any gold on the contacts. Now whatever might be inside the chips is a different story. I don't know about that aspect.

OTOH, some of the RAM strips you show on the desktop, in the background, clearly are of the gold-plated type.

 

[rmi2416]

Hmm well I have been stripping the PCBS out of a lot of units lately and it seems around 92ish they started using gold contact on ram pcb's is there anyone that confirm this and if so the older ones are indeed tin. Do I use just regular white paper? Also searching on the internet and not really finding much info on the subject. Is there a Database out there on the net that I can cross reference older parts with PN or SN to get a spec sheet?

Regards,
Ross

 

[jimdoc]

Yes they are tin, but I still get the same price as the memory with gold fingers
when I sell them. So don't trash the tin ones.

Jim

 

[rmi2416]

Thanks Jim. Will do.

Ross

 

[dtectr]

Hmm well I have been stripping the PCBS out of a lot of units lately and it seems around 92ish they started using gold contact on ram pcb's is there anyone that confirm this and if so the older ones are indeed tin. Do I use just regular white paper? Also searching on the internet and not really finding much info on the subject. Is there a Database out there on the net that I can cross reference older parts with PN or SN to get a spec sheet?

Regards,
Ross

www.datasheetarchives.com & http://www.alldatasheets.com for starters.

Just type the part number into google, you may have to try different combinations, & if online datasheets exist, they should show up in the search. A feww hours spent there can literally pay for itself 20 times over in lost time & chemicals.

EDIT: correct link address

 

[goldsilverpro]

Silver has a notorious problem with migration. On adjacent fingers, under certain conditions over a period of time, the silver can migrate through the adhesive and board material and cause a partial short.
https://encrypted.google.com/search?hl=&q=silver+migration+circuit+boards&sourceid=navclient-ff&rlz=1B3MOZA_enUS408US409&ie=UTF-8&lr=all

For this reason, silver is rarely used for fingers or traces. There have been improvements made in recent years, but you still won't find silver used that often (or, ever). Usually, if the fingers are coated with a white (non-gold) metal, it is tin.

 

[Acid_Bath76]

Silver has a notorious problem with migration. On adjacent fingers, under certain conditions over a period of time, the silver can migrate through the adhesive and board material and cause a partial short.
https://encrypted.google.com/search?hl=&q=silver+migration+circuit+boards&sourceid=navclient-ff&rlz=1B3MOZA_enUS408US409&ie=UTF-8&lr=all

For this reason, silver is rarely used for fingers or traces. There have been improvements made in recent years, but you still won't find silver used that often (or, ever). Usually, if the fingers are coated with a white (non-gold) metal, it is tin.

Thanks for this posting! I recently got my hands on about seven pounds of RAM, and a lot of it was "silver". I didn't pay for it, so I can't really complain too much. I'm glad I haven't processed them yet though. What a waste of chemicals that would have been. Next step is to figure out what kinds of metals are in the flatpacks. For that matter, I need to find out as much as I can about flatpacks in general. They're adding up by the pound and I need to figure out the best way to process them as efficiently and effectively as possible.