Instructables

Desoldering components with rubbing alcohol

Picture of desoldering components with rubbing alcohol
    I've heard the saying before that when theirs a need there's a solution. its the same here i have a need to desolder a box of pcb's and not an easy way to desolder in bulk  without a neck-ach. so in this instructable i'm going to show you a new way to desolder that almost anyone can do.
edit:
         ​This should be done in a well ventilated area and protective gear worn while doing this so you don't burn yourself or cause a fire.

edit #2:
          this is purely informational and i do not have any other ways to desolder surface-mount components easily and i wanted a cheep way to do this.also to put your concerns at rest i dont know if the components are unuseable or not most end up as keychains or refrigerator magnets.lastly i dont want to use an oven because the fumes from the PCB(Printed Circuit Board) could be harmful and cook into what ever gets baked in that oven.

 
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Step 1: Materials

most people have these if not it will cost you about 5 bucks at most.
  • tin lid (if you don't have one than use something non-flammable and wont melt)
  • pcb's (kind of necessary to be able to desolder)
  • 70% rubbing alcohol  (you can get it for $2 at dollar general or a pharmacy)
  • pliers (you dont want to get burned)
  • ignition source(matches, a spark, jacobs ladder, whatever floats your boat  :)

Step 2: Light

pour a fair amount of rubbing alcohol in the tin and light it if you use a spark like i did you cant have the probes below the surface or the spark will not light a fire and you'l get alcohol all over you. another thought you could use just about any fuel i think just be careful i am not responsible for you hurting yourself.

also do this outside or in a well ventilated area i did mine in the fireplace.

Step 3: Desolder

Picture of desolder
grip the pcb of your choice in a a pair of pliers and hold it close to the flame .try not to putout the fire.
hold it over the flame until you see solder starting to melt once that happens remove it from the flame and smack it upside down on the floor or on the side of a box to dislodge the components

you may need to repeat this several times
so thats that a new way to desolder pcbs
if you have any comments, criticisms, or questions please leave them in the comments or pm me.
maxhuey6 months ago
for single chip removal, I use a spring board under the chip and small pencil torch to heat up the pins quickly, .
mwacuff maxhuey6 months ago
I'm not familiar with the term "spring board". Could you provide specific details? Thanx.
maxhuey mwacuff3 months ago

Its a simple piece of thin metal, about 1/2" wide by 6" long, usually made from stainless still, there's a bend of about 20 degrees 1" from one end, this is the end that is inserted under the chip, you press down the long side to keep the chip under tension to pull up and start heating the pins.

Tanbam7 months ago
This is a novel idea, but it has some safety risks. If someone is holding the circuit board above a flaming bowl of alcohol and the board slips from their grasp, they could splash fire all over themselves!

A safer and a much more controlled method would be to use your oven. Preheat the oven to 380 degrees F, then bake the board on an cookie sheet lined with aluminum foil for about nine minutes. The solder will melt, and you can either whack them all off like you mentioned, or use tweezers to pluck a specific component.

umm some pple will want to cook in thier oven again ok.
Trelligan Tanbam6 months ago
I won't put PCBs (with unknown solvents, plasticizers, combustion products) into an oven I cook food with.

The OP's method has the advantage of speed (less damage to chips), and is an excellent way to harvest and reuse chips - especially if the boards are free and you can test before using in your own circuit.
I do firearms work, and there are several metal finishes that are baked on that I use, I have a fairly large "toaster oven" that I use for curing the finishes... and have used it to repair HP laptop mainboards.
carlos66ba Tanbam7 months ago
Or get a gas flame. I agree that doing with alcohol is dangerous because of the risk of splashing.
Eletruk6 months ago
Any problems with soot buildup? Usually holding stuff over an open flame is a good way to get stuff all black and sooty.
antioch Eletruk6 months ago
Incomplete combustion and the resulting soot occurs with wood, rubber, wax, etc.
Burning alcohol doesn't produce mentionable soot.
as long as its alcohol and water. any thing else it will soot up.
Ryan Hebron (author)  Eletruk6 months ago
a small problem but most of it washes off afterwords. most pcbs i desolder are onesided
baecker036 months ago
you should look into a solder pot... wouldn't be that much of a hassle and would save your pcbs and other components.
or a heat gun would would as well.
DragonDon6 months ago
A simple solution. Great!
gpavlovsky6 months ago
Is this method ESD-safe? LOL
frikkie6 months ago
the thing is you can damage the components also with the flame.
MCUman6 months ago
Why not just get an alcohol lamp for 6 bucks?

http://www.sciencecompany.com/Angular-Alcohol-Burner-120ml-P16029C689.aspx

Save yourself from peril.
Ryan Hebron (author)  MCUman6 months ago
i am 15 and have verry little money
The day you wish to trade your youth and exuberance for my wisdom, experience and decrepitude, let me know.
sublingual MCUman6 months ago
My thought exactly!
FrankenPC7 months ago
So, the chips are still viable after the intense heat?
Given they normally go through an oven for about two minutes to solder them on, I suspect this will be well within their thermal spec.
ac-dc Minifig6666 months ago
Two minutes? Goodness no, many are spec'd for only 10 to 20 seconds, at not much higher than the solder melting point.

Otherwise, it's not length of time as much as how hot they get. The trick to getting this to work well is you can't expect every chip you harvest to be viable, that you heat an area and are waiting for the moment the particular chip you want has molten solder pads which may result in adjacent parts overheating and being damaged.

Though personally, I used a blow torch before I got a hot air gun, and with it I was heating the back side of the board not the component side.
Well they tend to go through a 'soak' time. If you use the RSS model (Ramp-Soak-Spike) you generally want a temperature rise of between 2 and 4 degrees C per second, then hold at about 150C, just below the solder melting spec for a period of time, to allow the board to thermally soak. This helps prevent any warping as the thermal expansion coefficients for the board and the components might be different, so rapid heating of large components can literally rip your pads off the board. I usually soak for a good 2-3 minutes. Then after soak, you take the temperature above the melting point of the solder (I aim about 220C for leaded) just for a few seconds, then gradually cool down. With a commercial cooking oven its pretty much impossible to achieve these temperature ramp rates, but just try to stick as close as possible to them. Thats for paste soldering techniques at least, though for small boards with parts up to say 1206 size, I go for the hot air gun method and have had few problems.

Also the glue used on PCBs (usually red stuff) tends to soften at solder melting point anyway, at least sufficiently to pull the IC's off with some tweezers.

They tend to use the fire-removing technique in China on scrap boards, where most of our electrical waste ends up. Not sure what happens with all the components they take off - probably make there way back into the supply chain in cheap electrical goods...
I have "repaired" a few laptops by stripping them to the motherboard and putting them in a kitchen oven preheated to 400 degrees for 10 minutes to reflow the solder (usually under the graphics chip) and then turning the oven off and partly opening the door to let it cool off slowly.. Every laptop I have done this to has run afterwards! The original problem recurred or was not cured in some of them, but not of them 'burnt' in the oven!! Do note that without doing this, the laptops were already 'useless' so other than the labor of tear-down and rebuild, nothing can be 'lost,' the mother board is already scrap unless you wanna spend the beaucoup bucks to have this done professionally, and since they were 2 or 3 hundred dollar laptops, none were worth it. Saved by the oven is the bonus, otherwise they would be stripped for parts anyway..
This is what can be used to fix Xboxes with the red ring of death and many other problems with printer IO or power boards, intermittent celphone problems, etc. I tend to go with a lower temp for longer though - 350 for 15 minutes, but have seen many different temp combo's that work.
You've had to deal with those HP's too? Something most people are not aware of on many of the pcbs that they are going to try this trick on, is that most of the chips are GLUED in place first and THEN soldered, so that the chips are soldered onto the proper pads on the board.
Most chips will be, as the last person said, but tantalum capacitors and Photo-resistors don't seem to like it...
Landroo6 months ago
Took me awhile to decipher "pcb" as meaning printed circuit board. It's good form to write the whole word and keep the acronyms to a minimum, especially in a how-to article.
It would also be good form to ACTUALLY learn about specific components and the accompanying terminology.
PCB is a standard abbreviation. I wonder what someone who does not know PCB = Printed Circuit Board would be able to do with desoldered components in the first place.
Reclaimed components can be used for DIY projects where cost of new supplies are an issue for some. They could also be used in the teaching community for students who are interested in electronics.
Hey, PCB could mean Polychlorinated Biphenyl - and you could use 70% isopropanol to remove them - but you are right, it's obvious to anyone who would want the components what it means here.
Technically, PCB is an initialism, not an acronym. Acronyms must be pronounceable as words. ;)
imperio6 months ago
Good idea!
In Italy we can replace alcohol with grappa!

Imperio da Firenze
ninjuhplease6 months ago
Yeah, I'd like to echo the comment by PhilKE3FL... I'm an EE and do a lot of soldering for my job, and the best thing you can do DIY style is use a toaster oven at the appropriate temperature. In manufacturing environments they just use a special oven, but the idea is the same.

Also, be careful of what components you put near a flame. Especially electrolytic capacitors (look like little soda cans, most PCBs have them), which are full of ACID and will pop open if they exceed their rated temperatures. Or Tantalum capacitors which could possibly explode.

Just... be careful.
Hot plates tend to be easier and they don't melt plastic components like toaster ovens do. And it's simple to pluck the components off as they reflow.

For fast stripping, a heatgun to the rear of the board is usually good enough.

ccotton16 months ago
This is a bad way to do this, and it'll shave most, (if not all) of the life the component being removed MAY have been useful for.... Uncontrolled heat is a killer and holding an open flame is... about the same result as using a sledge hammer to remove the chips, most likely ruined. Use wicking and a heat shield and a little time if you want to actually USE what you're removing.
darrennie6 months ago
Would it not be easier to use a Bernz-o-matic propane torch instead? Your then able to control your temperature, time of heat and location to some degree.
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