Large scale desoldering?

[HarveyH42]

After desoldering a few trim pots off junk boards, and realizing that I could probably order some quicker then finding something close to what I was looking for, I though there has to be a quicker way.

Mostly, I've only used the wick/braid or sucker method, occasionally the propane torch/5 gallon bucket method (outdoor activity). Just wondered if anybody has come up with a better method of removing the parts from junk PCBs in mass.

Was kind of thinking about using a clothes iron and a shop-vac. Don't know if it gets hot enough, pretty sure its over 300 degrees (laser toner transfer). Figure if I could drill some holes through the bottom for airflow, cut a big hole in the side for the shop-vac hose. When the solder liquidfies, it gets pulled off the board, parts should basically fall off the board.

Yeah, I get some wierd ideas sometimes when doing slow, boring tasks. Sometimes they really aren't this bad.

Recycling parts can't be completely taboo. I know some parts don't tolerate heat, and mostly will be destroyed or altered. But there many good parts that can be reclaimed and used. Like these trim pots, usually 2-3 for a dollar (US$), but usually the ones you want are a dollar or so each...

 

[Andy1845c]

occasionally the propane torch/5 gallon bucket method (outdoor activity).

Never tried that...... Do you hold the board upside down over the pail and just let components rain into it?

It seems I save every board I come across. Its always fun when you can mine enough parts out of stuff that was in the trash and make a circuit.

I could sure clear up some closet space if i could find a way to remove them faster then one at a time.....

 

[philba]

I used to use a small butane kitchen torch to do this. clamp a corner of the board to a table (in my shop) so it mostly hangs over the edge with the component side down. Put a newspaper on the floor under it, gently heat the board and "pluck" the board. you will get a shower of solder and parts. Suprisingly effective.

I've single gotten a heat gun and a hot air station. the heat gun is more controlled than the torch so not as much burnt fr4.

The hot air station is good for selectively removing parts though through hole components are best done with an iron and solder wick.

 

[JimB]

I have used a heat gun instead of a propane torch. Again best done outside as the board can scorch and start to smell a bit.
Most components can stand quite a bit of heat before going off to silicon heaven.
My biggest problem in that area is legs coming off ceramic capacitors while trying to recycle them.

JimB

 

[HarveyH42]

Have to try the heat gun next time, had it for years, but don't think I've ever used for anything other than shrink tubing.

Mostly I don't worry too much about the small cheap parts, takes too long to sort through (wish I had some kids, knew they would be good for something...).

Tried a few searchs, but mostly coming up with single component tips, using junk boards for practice. I drive by electonic stuff all the time on trash day, get tempted to stop sometimes, but I've got too much stuff as it is.

Will keep looking for a better way, of desoldering large quantities of parts. Maybe the heat gun is significantly better. Maybe try it tomorrow.

 

[justDIY]

the heat-gun I use is a cheapo wagner paint stripping gun ... I harvest plenty of through-hole ICs and connectors using it, smt's as well. haven't tried fragile components like caps, I figure the electrolyte inside probably won't like the heat

originally I did this without water, and parts falling to the floor melted into the cheap carpet (don't worry, ugly workshop area). so I use a pan of water now, get a quick hiss when big ic's fall in ... so far none of them have been damanged due to thermal shock, but probably took years off their service life.

 

[Dean Huster]

When I was younger, I would hold terminal strips (hey, this was before PCBs) in pliers, heat them up and then fling or whip them toward a piece of safety glass from an old TV. Then I'd use long-nose pliers and dikes (diagonal side cutters) to unwrap component leads from the terminals. I'd save the solder splashes and melt them down for use as "lead" weights and other such things.

With PCBs and thru-hole components, I primarily use a solder sucker bulb (faster than a plunger solder sucker, less expensive than a vacuum-powered desoldering station) and desolder a bord that way.

Present common sense, especially with large boards chock full of ICs is to leave the components there, give the board a number or cute name, inventory the ICs on the board into a word processor with the board number attached and alphabetize. No sorting to worry about, you've not spent time desoldering an IC that you'll never use and the board stores about as handily as any other system. A lot less work.

Here's a write-up I did concerning harvesting SMT components:


A heat gun is one of the fastest methods of harvesting SMT components without causing damage. First, remove delicate thru-hole components that you wish to save using your normal thru-hole desoldering techniques. Then connect a ground clip to an obvious grounding point on the board and install an electrostatic discharge (ESD) wrist strap on yourself. Use a small heat gun such as the Ungar 6966C with an accessory tip that directs airflow to a very small point. Preheat a large area of the board without the accessory tip in place, then install the tip and begin removing components. Rather than directing the hot air directly at a component, direct it onto the PCB around the base of the part. Air flowing along the surface of the board will melt solder over a large area. Remove diodes, transistors and ICs in that order as you come to them in an area. Then remove the electrolytic capacitors, inductors, resistors and finally the ceramic capacitors in that order as you come to them. If you hold the gun at a 45º angle with respect to the board and start at one edge, work your way across the board in the direction of the heat flow. That way, future areas of the board will be preheated. Pluck the devices from the board with tweezers. Larger ICs can be placed on a wet sponge in a grounded tray to cool them down and to protect them from ESD.


Keeping ESD from SMT

While harvesting electrostatic-sensitive surface-mount devices from a board, the question always came up about what to do with the hot chips so that they're protected from electrostatic discharge (ESD). I've come up with two good ways to handle the problem.
One method is to lay out a flat sheet of galvanized sheet metal to which you've soldered a wire which is connected to earth ground along with your soldering iron, your grounding wrist strap, the circuit board from which you're harvesting and a pair of fine-tipped tweezers. You can get a new piece of scrap from nearly any heating/air conditioning shop around town. Make sure the metal is free from oil by rinsing with alcohol. Use a hot-air gun to melt the component from the board and then pluck the item from the board with the tweezers and deposit on the sheet metal to cool. If you'd like the device to cool down more rapidly than is obtainable by placing it on the sheet metal, place a wet cellulose sponge on the sheet metal and place the newly-desoldered components on that. Using a metal/sponge landing pad with a large surface helps you to organize your desoldered components a little better for later sorting.


Dean

 

[Hero999]

In my oppinion it depends on the componants when it comes to recycling. Most resistors and capacitors aren't worth it, some ICs and inductors are but you need to be careful with them.

Some small SMT capacitors aren't vented and have a tendency to explode when blasted with the heatgun.

 

[philba]

In my oppinion it depends on the componants when it comes to recycling. Most resistors and capacitors aren't worth it, some ICs and inductors are but you need to be careful with them.

Some small SMT capacitors aren't vented and have a tendency to explode when blasted with the heatgun.

If you blow hot air on the component side you'll often get a shower of 805s and 603s but if you heat from the opposite side of the board, many smts come off pretty well unscathed and it doesn't take very long to harvest them. I've got bunches that I just throw into 1 pint plastic containers. tants and smt electrolytics seem to be ok. sort through when I'm building a project and have an odd value I need. resistors are kind of a waste so I don't bother. I prefer using new stuff but they will do in a pinch. pre-tinned... lol Of course, I take the more valuable stuff off first.

 

[RODALCO]

Heatgun works best for me.
Do it outside or in a well vented room and heat the board from the tinned side. Most parts will fall off easily.
It works very well for IC's and IC feet if you recycle some of the better ones.
Sometimes you may have to tap the board on the working table which i usually cover with some old newspaper, saves the table and having to scrape off the solder splashes. The paper won't catch fire or make it a little damp if you are worried about it.
Sometimes with double layered boards put the circuit board in the vice and heat with the gun while trying to pull the wanted components off with a pair long nose pliers or tweezers.

 

[drage]

..is the burning smell of pcb bad for you?

 

[HarveyH42]

..is the burning smell of pcb bad for you?

I don't know for sure, but usually if it don't smell good, then its probably a bad thing. I do it outside, because I don't like to stink up the house (lasts for days), but its never made me sick or anything.

You only get a lot of smoke if you get a little careless with the heat. If you get it hot enough to burn the board, then you are likely damaging the parts you are trying to save.

 

[philba]

..is the burning smell of pcb bad for you?

yes it is, especially when your spouse gets in your face about stinking up the house. I know this for a fact.