Texasgolden
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Trying to get an idea on value on these beauties
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Texasgolden
New member
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- Jan 16, 2018
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So they are stamped on top of box Gold Tin, AU SN
Hi,
Since it contains tin, what I would do is boil one of those squares in hot HCl to remove the tin, weigh it afterward to see what the gold / tin parity is in the mix. The remaining gold can be refined with HCL and Bleach to see how pure is the gold you have in the alloy. (it is not clear from the picture)
Then you can set a price for each item or for the entire lot.
Hope this helps.
Stay safe.
Pete
Edited: it also says Kovar on the box, it may well be that the support is kovar the plating is gold and the soldering is tin, HCL, could solve you with the tin and kovar.
Since it contains tin, what I would do is boil one of those squares in hot HCl to remove the tin, weigh it afterward to see what the gold / tin parity is in the mix. The remaining gold can be refined with HCL and Bleach to see how pure is the gold you have in the alloy. (it is not clear from the picture)
Then you can set a price for each item or for the entire lot.
Hope this helps.
Stay safe.
Pete
Edited: it also says Kovar on the box, it may well be that the support is kovar the plating is gold and the soldering is tin, HCL, could solve you with the tin and kovar.
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The lids can be upwards of 16g of gold per Kg (if the good ones.)
kurtak
Well-known member
These are the Kovar lids for 8031 ceramic micro possessors
On the box lid (first pic) it says --- ALLOY Au/Sn Au Kovar
The Au/Sn is referring to the solder which is a gold/tin alloy
The Au is referring the gold plating
Kovar is of course the actual lid
To get rid of the tin you can do a hot/warm HCl soak - it does not need to be boiling - a slight simmer/boil at most
Because the tin is alloyed with gold it takes a bit of time & heat to get the tin dissolved into solution resulting in an ultra fine undissolved gold dust/powder - this will likely still contain some (traces) of undissolved tin
To insure getting the most complete (but likely not fully complete) dissolving of the tin you need to do relatively frequent stirring of the lids so that fresh acid gets between the lids where they are setting/stuck on top of each other --- very time consuming pain in the butt
Then (if you go this route) you need to do "several" cold HCl washes to get the fine gold particles washed out that are stuck between the lids --- if you just try to do the washing with water the water diluting the dissolved SnCl (tin Chloride) will cause meta stannic acid (the nasty tin paste we all hate) to precipitate out - which will end up in the gold particles you are trying to wash out
Bottom line here is if are going to get rid of the tin & recover the gold in the solder it is a time consuming pain in the butt & tin is likely to follow the gold --- & you still have to go after the gold plating
My point here is that if you are going to try to process these by first trying to get rid of the tin - then get rid of the Kovar to recover the foils --- you are likely looking at a several day time consuming - LOTS of acid - pain in the butt process - with some tin following the gold anyway
IMO - you are better served to process these lids going direct to AR
Kovar is even "somewhat" resistant to AR - but nowhere near as resistant as just nitric - or just HCl
Because Kovar is somewhat resistant to AR (but less so then nitric - or HCl) you still need to boil the lids in the AR - but - it will take MUCH less acid & MUCH less time - you can have a kilo batch done in a day
Direct AR is a "down & dirty" process as you put Kovar & gold (from plating & solder) into solution - but it is done in MUCH less time with MUCH less acid --- the down side is that with AR you also end up creating the meta stannic acid - which is a matter of filtering
For what it is worth - I have done both - ridding base metals first - & direct AR
What I learned after trying to rid base metals the first time I tried processing these lids was that I am FAR better served going direct to AR
In other words - no matter which way you go with in processing these lid the tin is a problem & so though you have to deal with the meta stannic acid going direct to AR it is better then the time & acid consumed in trying to first get rid of the base metals
The other option is to cyanide leach/strip - but that is another story process
Kurt
On the box lid (first pic) it says --- ALLOY Au/Sn Au Kovar
The Au/Sn is referring to the solder which is a gold/tin alloy
The Au is referring the gold plating
Kovar is of course the actual lid
To get rid of the tin you can do a hot/warm HCl soak - it does not need to be boiling - a slight simmer/boil at most
Because the tin is alloyed with gold it takes a bit of time & heat to get the tin dissolved into solution resulting in an ultra fine undissolved gold dust/powder - this will likely still contain some (traces) of undissolved tin
To insure getting the most complete (but likely not fully complete) dissolving of the tin you need to do relatively frequent stirring of the lids so that fresh acid gets between the lids where they are setting/stuck on top of each other --- very time consuming pain in the butt
Then (if you go this route) you need to do "several" cold HCl washes to get the fine gold particles washed out that are stuck between the lids --- if you just try to do the washing with water the water diluting the dissolved SnCl (tin Chloride) will cause meta stannic acid (the nasty tin paste we all hate) to precipitate out - which will end up in the gold particles you are trying to wash out
Bottom line here is if are going to get rid of the tin & recover the gold in the solder it is a time consuming pain in the butt & tin is likely to follow the gold --- & you still have to go after the gold plating
Though both nitric & HCl will dissolve the Kovar - Kovar is quite resistant to both acids when used alone - HCl works better then nitric - BUT - Kovar is still very resistant to HCl alone - it takes A LOT of HCL - it needs to be BOILING - & depending on the size of the batch (how much Kovar you are trying to dissolve) it can take 2 or 3 change outs (decant & start with fresh) HCl - & as well it can take as much as a couple of days (again depending on batch size) of boiling the Kovar in HCl to dissolve all the Kovar away for recovery of gold foils
My point here is that if you are going to try to process these by first trying to get rid of the tin - then get rid of the Kovar to recover the foils --- you are likely looking at a several day time consuming - LOTS of acid - pain in the butt process - with some tin following the gold anyway
IMO - you are better served to process these lids going direct to AR
Kovar is even "somewhat" resistant to AR - but nowhere near as resistant as just nitric - or just HCl
Because Kovar is somewhat resistant to AR (but less so then nitric - or HCl) you still need to boil the lids in the AR - but - it will take MUCH less acid & MUCH less time - you can have a kilo batch done in a day
Direct AR is a "down & dirty" process as you put Kovar & gold (from plating & solder) into solution - but it is done in MUCH less time with MUCH less acid --- the down side is that with AR you also end up creating the meta stannic acid - which is a matter of filtering
For what it is worth - I have done both - ridding base metals first - & direct AR
What I learned after trying to rid base metals the first time I tried processing these lids was that I am FAR better served going direct to AR
In other words - no matter which way you go with in processing these lid the tin is a problem & so though you have to deal with the meta stannic acid going direct to AR it is better then the time & acid consumed in trying to first get rid of the base metals
The other option is to cyanide leach/strip - but that is another story process
Kurt
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I agree with you, but since the question was about " Trying to get an idea on value on these beauties "determining the aproxximate value of the lids, that is why i wrote what i wrote. Probably you dont even need any acid, just some calculations to determine the aproxximate thickness and weight of the gold plating on the lids.
Yes it is a gross estimate, but still more than nothing.
Pete.
In the second picture, upper left corner, it seems that the lid is stamped(relief) whereas the lid on the bottom center is serigrafic painted. May be just the picture that deceives me, but I think you have 2 types of lids, one with kovar base (the serigrafic painted) and another with either copper base or karat (unlikely but not impossible).
I might be completely wrong allthough these lids were used for ceramic IC`s. (See picture below) and if it is military origin it might be karat easily.
Anyone any imput, i am just curious.
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anachronism
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The tiny military ones whilst not karat do run out at more than 25g per Kg
kurtak
Well-known member
To the best of my knowledge the VAST majority (if not all) ceramic IC chip lids are made of Kovar
That is because Kovar expands & contracts (during heating & cooling) at very close to the same rate as ceramic which prevents the lids from breaking free from the ceramic when the chips heat up &/or cool down
I believe (but could be wrong) that Kover was actually developed for applications where metal needs to be bonded to ceramic
They needed a metal that would expand & contract at a very close to same rate as each the metal & the ceramic
Kurt
Interesting stuff... thank you...
kurtak
Well-known member
https://www.engineeringclicks.com/kovar/
From that web page ------------
Main benefits of Kovar
The coefficient of thermal expansion is THE most important mechanical property of Kovar. The alloy is precisely formulated and controlled to produce a coefficient of thermal expansion that is very close to that of hard glass (e.g. borosilicate glass) or ceramic, meaning that it expands and contracts at a similar rate. It is therefore perfect in applications where it is used in conjunction with glass or ceramic materials, especially where a hermetic seal must be maintained across a wide temperature range. There are a vast number of products where metal and glass or ceramic are joined together. You can probably think of many examples of such products in daily life.Kurt
