[Moony] reasons that the IR filter is a waste anyway, since the luminous efficiency of halogen lights is so low: around 3.5%. And that means 96.5% heat! But there’s still a lot of light streaming out into a very small area, so if you’re going to look at the board as you de-solder, you’re really going to need a pair of welding goggles. Without, you’ll have a very hard time seeing your work at best, and might actually do long-term damage to your retinas.
So the next time you’re feeling jealous of those rework factory workers with their fancy IR soldering stations, head on down to the hardware store, pick up a gooseneck lamp, a 100 W halogen spotlight, and some welding goggles. And maybe a fire brick. You really don’t want your desk going up in flames.
We love make-do hacks, but we love doing it right, too. Just watch [Bil Herd] extol the virtues of a real IR desoldering station. And then giggle as you do the same thing with a few-dollar halogen bulb.
Curious what wavelength the IR desolders are operating at. If you stare at a IR light source of sufficient power or it’s reflection it’ll do just as much damage and possibly more becasue you don’t “see it” as visible light. You notice it when you start to feel a dull ache.
It would be the spectrum of a black body radiator. If you know the temperature you can calculate the exact wavelength distribution. However, most IR is blocked by the lenses of your eye, so the damage would happen there.
Tell you something: use a Fresnel lens from a overhead projector and the sun. works very well. you can make a system where the lens is just moved slightly to get it out of the hotspot when done.
I find that clouds present a problem with temperature control and result in me occasionally losing sight of the PC board through the smoke. To remedy the smoke issue, on cloudy days I only desolder when it’s windy.
I use linear short 600W halogen (old movie lightning stuff) in 100W halohen reflector. Has enough spread to evenly reflow those Termi GPUs or with more juice desolder everything from a board. Power is about 20-40% with triac phase regulation. Only fails were those Elpida plagued GPUs. I tried 100W linears, they did not reach enough temperature. And you need to preheat the PCB from the bottom so it will not eat the heat. Preheaters are thrown out everywhere, just be creative and Macgyver it together.
The filter is not a waste, because it acts like a heat diode. IR comes in at a shorter wavelenght through the glass, heats up the board, the board radiates heat back at a longer wavelenght, which gets reflected off of the glass and back onto the board – keeps the board hotter and the bulb cooler.
Dichroic filters reflect stop-band wavelengths. However, I guess (couldn’t find anything concrete) they’re reciprocal, so there’s no heat diode.
They are absolutely reciprocal (and angle dependent). The effect Dax described is more or less achieved by any plain glass sheet in front of the lamp. I am sure such a heat filter is transmissive over a broad spectrum of heat radiation, at least as much as the base glass allows.
GOD I love it. so simple. And like I have a lot of light bulbs every thing from sergical to reg. 6v to 150w 480v to 200w Stuff I never new existed. Hospital stuff. from old equipment but I always had to keep stock of the lights. now I know what to use some of them for. Thank you very much…
Got the “industrial” sort at work and no-one has yet managed to successfully desolder a BGA chip, or an LQFP for that matter.
I rely on using the hot air rework tools for the usual stuff and a paint stripper (Da Big Gunz) for the big chips.
Seen videos of people IR soldering like its bread and butter and this hack will make it cheap for houshold hobbyists to own.
What a waste. How many square feet is being cooked, to desolder one square inch. It’s likely to incinerate that 0805 smd, than desolder it.
“how many square feet?” Not many. Holding the light right up to the board, it’s probably only a couple square inches of surface affected. Just about right for a big FPGA or something. A little big for some chips, surely.
A couple of years ago I was tearing down larger laser printers for parts. The fuser has a full width quartz lamp, maybe 0.375″ in dia. I assume the output is higher on the faster printers. I haven’t found a use and have considered tossing them. Maybe they would be good for reflow? I’m thinking something like a modern pizza oven – lamp is stationary and a belt or similar pulls the board under the lamp. Any other ideas to put those to use? I don’t recall that wattage, and I suppose I should measure the cold impedance.
Some (semi)professional reflow ovens use just 2-4 of these lamps as heating elements. Some 30yrs ago we used a similar lamp (exposure from a photocopier, about 30cm long and 1kW) as floodlight for playing table tennis in the evening. Accompanied by the occasional smell of roasted meat, when a too-curious moth flow into the light. This was a very “basic” contraption consisting of the lamp, a piece of wood, two ceramic-base contact springs and a small reflector which was not completely able to prevent the wood from scorching. Of course it was advisable to position the lamp before plugging it in as there was no other protection against electric shock or getting burnt than “just don’t touch the dangerous parts”. But it worked.
In all fairness the IR thing I showed didn’t cost much more than an IR bulb, at least relatively speaking when comparing to “real” solderers. It also included ceramic preheater element and temp control… and a soldering iron lol.
Preheating is key IMHO in order to remove a BGA or a TQFP with one of those huge heatsink lands underneath it, Preheat is also key to not cooking the board as it reduces the actual exposure time to the IR,
With all of that said I use a piece of aluminum foil with a hole cut in it to expose just the target device.
I actually bought my IR station as I was working my expensive AV Receiver/amplifier and needed to replace an HDMI chip with a huge heatsink tab underneath, which worked perfectly in spite of my lack of experience.
Remember, IR is also absorbed differently than visible wavelenghts by the different materials on a typical PCB. It’s possible without the filter you won’t have as uniform heating, and may damage some parts before actually melting all of the solder, for example. I’m guessing efficiency is a big factor though.
Very hacky–I like it! I was most amused that at 00:14 you can see that he’s put the 100W bulb in a socket rated for 50W max.
rated for 50W continuous duty :-) In the few minutes necessary for desoldering it will work. And if not, it at least does not run unattended.
100w Par38 Heating Lamp Lamp Ray Bulb
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