Separating fingers from board

[jgreywolf]

In searching the forums I have gone through a few threads talking about different depopulation methods - but what I haven't seen are different methods for separating fingers from the rest of the board.

Snap them with a plier?
Snap/Cut with heavy duty "dikes"?
Some form of hand saw?
Maybe a powered saw - probably cut the wrong fingers

I've been able to remove most of the IC, though a couple are proving stubborn and tend to just shatter when I try to chisel/pry them off. Something to do with my hands while waiting for a build or deployment to complete

Thanks!

 

[Shark]

I used hand shears for cutting tin most often. A slot cut in a piece of hard wood just deep enough to snap the fingers off can be used as a mold. Even large cutting shears for paper work pretty good. It is mainly about how many you have and how much you want to invest in the tool. As the numbers grew for me I started using a small propane torch (cigar lighter). Then I started using a rotisserie oven with a basket on the turning arm. This even worked on some small boards and peripheral cards, but needed watching to avoid over heating (burning) the boards.

Edit:
The newer memory sticks that don't have wire legs most often need heat to avoid breaking them.

 

[jgreywolf]

After writing this I went out to my workshop and played with some smaller tin snips I have. They seemed to work pretty well for most of the ones that I have.

The heat is just to loosen them up a bit?

 

[markscomp]

I used hand shears for cutting tin most often. A slot cut in a piece of hard wood just deep enough to snap the fingers off can be used as a mold. Even large cutting shears for paper work pretty good. It is mainly about how many you have and how much you want to invest in the tool. As the numbers grew for me I started using a small propane torch (cigar lighter). Then I started using a rotisserie oven with a basket on the turning arm. This even worked on some small boards and peripheral cards, but needed watching to avoid over heating (burning) the boards.

Edit:
The newer memory sticks that don't have wire legs most often need heat to avoid breaking them.

A slot cut in a piece of hard wood just deep enough to snap the fingers off can be used as a mold

nice

 

[Shark]

After writing this I went out to my workshop and played with some smaller tin snips I have. They seemed to work pretty well for most of the ones that I have.

The heat is just to loosen them up a bit?

With the torch I hold the memory with heavy pliers and heat the chips. Once they are hot, I bang them on the edge of a metal pan that I use to catch the chips in. The downward force, if the solder is soft, will drop the chip straight down in the pan.

 

[Shark]

 

[speed]

I use a bench mounted hand shear.

 

[Bobby1MGRN]

If you have lots of boards to snip, are looking to go into this for a long period, and you have a work area to secure it to a bench it's worth investing in a sheet metal sheer (guillotine). For an entry level one you can get a cheap heavy duty one from vevor (I have no affiliation with these), it suits me very nicely, can remove approx 1000 ram fingers very tightly cut in 2-3 hours, no effort at all, cost me around 60GBP (70-80USD I believe).

 

[orvi]

I never had to do it myself in large volume, but for fingers, bench shear is best investment - both time and nerve saving, and also blister-hand avoiding

For components, I conveniently use heatgun with adjustable temperature.
I have setup when I use small vice (smallest junk-cast iron vice for few euros is more than sufficient) to hold the board in place. Then I heat the board on places where I want to remove the components, and when tin melt, I pull the desired components out with pliers. And as you are pulling the components from the other side, you do not burn your hand.
RAM´s, I used to do it with chisel and hammer. Place RAM vertically, so it is supported with hardwood or metal (placing it on some piece of wood against the wall for example, or making some L-shaped wooden tool for it) with two thick nails on the bottom to prevent slipping. Then with chisel, you conveniently hammer all components down. Too sharp chisel is not very good, and so is dull one. Something you do not cut yourself with is the best

 

[Alondro]

I use tin snips for taking off the foil strips, and various hand tools for the components. Most of the chips I can get off with an old knife I shaped into a chisel point. The trick is learning how to brace the board or RAM at just the right angle to knock the chips loose, and the attachment method of the chips plays a role too.

RAM chips attached with the little solder dots often pop off quite easily with the blade under the edge of the chip and a few taps on the back of the handle.

Whenever I'm watching TV or videos, I'm depopulating boards and dissecting interesting components.

 

[GoIdman]

I use tin snips for taking off the foil strips, and various hand tools for the components. Most of the chips I can get off with an old knife I shaped into a chisel point. The trick is learning how to brace the board or RAM at just the right angle to knock the chips loose, and the attachment method of the chips plays a role too.

RAM chips attached with the little solder dots often pop off quite easily with the blade under the edge of the chip and a few taps on the back of the handle.

Whenever I'm watching TV or videos, I'm depopulating boards and dissecting interesting components.

I use the same techniques, for BGA ram chips and legged ic ram chips i use a plain cutter, just cutting off the legs and the IC will fall from itself, or pop the BGA`s by the corner with the same cutter. The cutter is the metal framed one with multiple (10) blades inside. Works like a charm.

 

[Alondro]

I use the same techniques, for BGA ram chips and legged ic ram chips i use a plain cutter, just cutting off the legs and the IC will fall from itself, or pop the BGA`s by the corner with the same cutter. The cutter is the metal framed one with multiple (10) blades inside. Works like a charm.

The little thin-legged chips I can cut with one corner of the edge of my knife-chisel I fashioned. It works well for multiple types of chips. The only ones it can't get are the really tiny ones that are soldered tightly to the boards. I'm not sure if those are even worth pursuing, though. They're so tiny and modern, I can't imagine there's much value in them.

Other chips with little legs are thick enough I can grab them with fine-edged pliers and twist them right off the boards in seconds. It helps when the chips aren't glued on with epoxy (some are like that and it's more annoying to remove them).

Eproms are a different story. The legs on those are so thick, I have to either pry them off the board or twist them until the legs snap.

 

[Alondro]

Out of curiosity, I cracked off some of the tiny chips stuck tight to the boards and looked at the fragments under a magnifying glass... and lo and behold, most DID have a ring of tiny gold bond wires in them surrounding the central silicon wafer.

Well, looks like I have to find an easy method to knock those off after all. With gold bond wires in such small chips, the recovery of gold per pound of them is going to be far higher than from, say, typical EPROMS, which have so much of their mass in epoxy and the long legs.

I think I'll use a plastic soda bottle top and a long-handle screwdriver with a sharp tip. Problem with the tiny ships is that cracking them apart to get them loose sends fragments flying most of the time, which means gold is being lost. If I can cover the chip with a little plastic 'hood', that should catch the pieces.

 

[Shark]

Hold the memory stick with heavy pliers, heat the chip with a small torch. When hot bang the pliers on a metal pan. The chip and some solder is caught in the pan. Less mess and speedy to boot. Once done a few times and you get a feel for it you will surprised how fast it can be and no broken pieces flying around to who knows where.

 

[orvi]

Hold the memory stick with heavy pliers, heat the chip with a small torch. When hot bang the pliers on a metal pan. The chip and some solder is caught in the pan. Less mess and speedy to boot. Once done a few times and you get a feel for it you will surprised how fast it can be and no broken pieces flying around to who knows where.

I personally hate that burning smell of plastic with fire retardants so I use heatgun instead. You can shape something like U or O "tunnel" from insulation wool (glass or ceramic), position the heatgun in line with U or O shape and place few pieces to warm up inside, as heatgun blows hot air through. Half a minute and they are nicely heated and ready to "knock-off" the chips.

 

[Shark]

Yes. It is a fine line between removing chips and choking on the smell. Progressing over time I used many different ways to remove the chips. The rotisserie oven has been a favorite for speed and lowering the smell. But you have to babysit both methods.

I have been curious about the method large electronic companies use. But find very little information on how they do it.

 

[orvi]

Yes. It is a fine line between removing chips and choking on the smell. Progressing over time I used many different ways to remove the chips. The rotisserie over has been a favorite for speed and lowering the smell. But you have to babysit both methods.

I have been curious about the method large electronic companies use. But find very little information on how they do it.

Semi-truck came to the gate of the hopper, unload the thing, they fire up the furnance, start incinerating it in shaft furnance... Material is mainly shredded and big ferrous metals chunks are removed by magnet. And as it goes down the hole, carbon is burned off, and it does not need that much external heating to get everything nice and hot. With charge, there is CaO mixed alongside with other proprietary mixes of fluxes, so glass (from fiberglass) mix and form nice and liquid slag (CaSiO3 and other stuff - around 1300°C). Molten metal and slag flow down, get separated (as slag and iron in iron smelter), and metal is next pyrometallurgically refined to eliminate Pb (as relatively volatile and liquid PbO - depends on the process), Sn (either oxidized away to SnO2 and passed to the slag and lost, or carefully oxidized to volatile SnO - lots of strictly proprietary techniques for this) and ferrous metals. Zn and Al burn/volatilize... So in the end you are left with relatively usable copper alloy, which is then electro-refined for copper recovery and PMs end up in slimes

Nice to imagine on the paper/screen, but hard to perform right on large scale and tight margin. Mostly the pyrometallurgical "clean-up" of the first metal alloy - that is the artistic thing Mainly to get rid of tin. Very stubborn element to have in melt as oxide

 

[Alondro]

Semi-truck came to the gate of the hopper, unload the thing, they fire up the furnance, start incinerating it in shaft furnance... Material is mainly shredded and big ferrous metals chunks are removed by magnet. And as it goes down the hole, carbon is burned off, and it does not need that much external heating to get everything nice and hot. With charge, there is CaO mixed alongside with other proprietary mixes of fluxes, so glass (from fiberglass) mix and form nice and liquid slag (CaSiO3 and other stuff - around 1300°C). Molten metal and slag flow down, get separated (as slag and iron in iron smelter), and metal is next pyrometallurgically refined to eliminate Pb (as relatively volatile and liquid PbO - depends on the process), Sn (either oxidized away to SnO2 and passed to the slag and lost, or carefully oxidized to volatile SnO - lots of strictly proprietary techniques for this) and ferrous metals. Zn and Al burn/volatilize... So in the end you are left with relatively usable copper alloy, which is then electro-refined for copper recovery and PMs end up in slimes

Nice to imagine on the paper/screen, but hard to perform right on large scale and tight margin. Mostly the pyrometallurgical "clean-up" of the first metal alloy - that is the artistic thing Mainly to get rid of tin. Very stubborn element to have in melt as oxide

I could actually build a simple shaft furnace. I found a 12-foot cast iron pipe 4" in diameter with 1/8th inch thick walls. I could build a kiln around part of it.

But before I do that, I need to fiddle around with electrorefining copper alloy to get it right on a small scale.

 

[jphayesjr]

In searching the forums I have gone through a few threads talking about different depopulation methods - but what I haven't seen are different methods for separating fingers from the rest of the board.

Snap them with a plier?
Snap/Cut with heavy duty "dikes"?
Some form of hand saw?
Maybe a powered saw - probably cut the wrong fingers

I've been able to remove most of the IC, though a couple are proving stubborn and tend to just shatter when I try to chisel/pry them off. Something to do with my hands while waiting for a build or deployment to complete

Thanks!

A sharp wood chisel or pneumatic chisel is fine.

 

[jphayesjr]

A sharp wood chisel or pneumatic chisel is fine.

A plate shears is also good-accurate and fast, but keep it very sharp.