Vacuum desoldering gun vs Hot air station

[PurpleAmaranth]

I got a METCAL SP-PW3-11 desoldering unit for free. Seems to work by heating the solder, pressing the trigger and then it vacuums it up? Not sure the unit fully works, but I'll have to play around with it more. I've never seen one of these before, I've always used either copper braid (annoying) or hot air to desolder. I'm considering selling this to buy a hot air station (I only have an iron currently). Is there an advantage to a system like this over hot air? Seems like hot air is more versatile, and works just fine for desoldering, so why buy these apparently rather expensive units?

[dorkshoei]

Seems like hot air is more versatile, and works just fine for desoldering, so why buy these apparently rather expensive units?

If you have to remove a significant number of thru hole components you'll quickly find the above comment isn't true.

If you are not careful you can also easily damage the PCB with hot air trying to remove thru hole.

Hot air can be useful for final state of removing thru hole where the vacuum can't quite clear the hole. 

And obviously hot air is good for smd.

[J-R]

I use the Hakko FR-301 for clearing through-holes and the Hakko 850 for SMD.  I'll never give either of those up.  Before that it was just a solder-sucker or braid and a conventional soldering iron.

I've been watching this guy lately and he seems to have some mad skills as well as a decent mix of equipment: https://www.youtube.com/@northwestrepair

[tooki]

I got a METCAL SP-PW3-11 desoldering unit for free. Seems to work by heating the solder, pressing the trigger and then it vacuums it up? Not sure the unit fully works, but I'll have to play around with it more. I've never seen one of these before, I've always used either copper braid (annoying) or hot air to desolder. I'm considering selling this to buy a hot air station (I only have an iron currently). Is there an advantage to a system like this over hot air? Seems like hot air is more versatile, and works just fine for desoldering, so why buy these apparently rather expensive units?

Equating hot air and vacuum desoldering tools is like equating a stovetop and oven: they’re both heat-based cooking devices, but there is very little overlap in their applications.

Continuous-vacuum desoldering is more or less the only way* to reliably desolder multipin devices from PCBs with plated through-holes. (And even then, only with proper technique. Just melting and sucking won’t do it, you need the right motion at the right time, too.) Every other kind of solder sucker or wick leaves residual solder in the plated hole, frequently leaving the pin stuck by a tiny amount of solder. Continuous-vacuum desoldering with the right technique lets you melt the joint, suck of the solder, and then cool the joint while the leg is free, preventing it from soldering itself back on.

Hot air is great for SMD, and as a source of auxiliary heat for vacuum desoldering (like when a ground plane is sucking away all your heat).


*OK, technically it can also be done with a small solder bath, or with special desoldering blocks that are basically special tips that heat every pin simultaneously. I don’t think anyone makes the latter anymore. But both of these methods leave the holes filled with solder, leaving you with an extra step to clear the holes. There are also “desoldering needles” that are basically stainless steel tubes you shove into a melted solder joint, around the pin. Never used them, no idea if that method is any good or not.

[wraper]

Seems like hot air is more versatile, and works just fine for desoldering, so why buy these apparently rather expensive units?

Hot air does not work for large TH parts, nor it should de used on phenolic PCBs (FR2) due to very high chance of causing damage. These are very different tools for very different uses. If the question is which one of two you should get if you must chose only one, then it's a hot air as it's a must for SMD. However hot air has barely any use where desoldering iron is used.

[tooki]

As for proper technique, I refer you to what I wrote in another thread:

Watch this video from PACE. It’s part of a video manual for an old model of theirs, so you can ignore the product-specific bits, but the technique shown is applicable to any continuous-vacuum desoldering device. The actual THT desoldering process is at 17:55–22:25, but I recommend at least skimming through the whole video.

https://youtu.be/IqE1KA0OAnM

I’ll also add a reminder that desoldering irons are a bit fickle, in that they need more care and maintenance than a soldering iron. Clean them before they clog up, make sure filters are clean (they get gummed up with flux vapors; you can often clean filters a few times by soaking them with solvent, squeezing them out, and then letting them dry fully, rather than buying expensive filters every time.), and TIN THE TIP!! People often forget to tin the tip, then it oxidizes, which in turn dramatically reduces heat transfer, so then people turn up the temperature, which in turn accelerates oxidation… TIN THE DAMNED TIP, thoroughly and frequently!

[KungFuJosh]

I have an Aoyue 2703A+ station that has both hot air, and a similar desoldering vacuum. They're simply different tools for different jobs. Hot air is better on SMT, and the gun is better for THT. There's some overlap, but not much.

I've seen people that tried to use hot air for THT stuff and left large bubbles in the PCB. That won't happen with the gun.

Either device requires proper technique, and PACE videos are usually a win.

[coppice]

Seems like hot air is more versatile, and works just fine for desoldering, so why buy these apparently rather expensive units?

Hot air does not work for large TH parts, nor it should de used on phenolic PCBs (FR2) due to very high chance of causing damage. These are very different tools for very different uses. If the question is which one of two you should get if you must chose only one, then it's a hot air as it's a must for SMD. However hot air has barely any use where desoldering iron is used.

There is a reason hot air tools only appeared as surface mount techniques started to take off. They are pretty useless in a through hole world. Through hole may be less important these days, but it isn't going away. When you need robust mounting of something tall, through hole is still the way to god. Try getting a large through hole connector out of a board with just a hot air gun, without excessively roasting everything. This is truer now than in the heyday of through hole, as lead free solder means we have to get things to an even higher temperature than in the past.

[shapirus]

Try getting a large through hole connector out of a board with just a hot air gun, without excessively roasting everything.

Or a heat sink!

[joeB]

I think it really depends on what you are trying to do. I have all 3 systems available, but 95% of the time I use the copper braid. However, when you need the hot air for a chip, there is really no alternative. The FR-300 is probably the least used of the three for me, but you reduce the risk of damage to the pcb and it is significantly faster for through-hole.

[nctnico]

Seems like hot air is more versatile, and works just fine for desoldering, so why buy these apparently rather expensive units?

Hot air does not work for large TH parts, nor it should de used on phenolic PCBs (FR2) due to very high chance of causing damage. These are very different tools for very different uses. If the question is which one of two you should get if you must chose only one, then it's a hot air as it's a must for SMD. However hot air has barely any use where desoldering iron is used.

I don't think you can say it like that (except for FR2). I'm using all techniques and it depends on the board and the part which way is the best one. For example: at some point I desoldered a pentium 1 processor with the heatsink stuck on from a 6 layer board. There was no alternative other than hot air (1500W heatgun) to get it off. It just takes carefully heating the board gradually.

For reworking multilayer PCBs with lots of copper, a hotplate or pre-heater is an essential tool to make a board suck away the heat at a slower rate. Recently I had to replace a large QFP with thermal pad on a 10 layer board (each layer almost full copper) and with the use of a hotplate (and hot air), this is a quick & easy job to do.

So far my experience with solder sucking irons (even with an upgraded vacuum pump) has not been stellar. I have not used mine (Ersa) in ages. I'm using desoldering braid from Chemtronics. Still, the Hakko unit mentioned by J-R looks like it is worth trying but the continuous vacuum system Tooki mentions sounds like the real solution. But likely expensive.

[tooki]

So far my experience with solder sucking irons (even with an upgraded vacuum pump) has not been stellar. I have not used mine (Ersa) in ages. I'm using desoldering braid from Chemtronics. Still, the Hakko unit mentioned by J-R looks like it is worth trying but the continuous vacuum system Tooki mentions sounds like the real solution. But likely expensive.

FYI, I found Ersa’s current vacuum desoldering iron (X tool Vario) to be disappointing, because it’s not reeeeeeeeaaaallly continuous vacuum. For those who haven’t used it:  The handpiece has a mechanical valve which is normally closed. The vacuum pump has a pressure sensor and automatically pumps a vacuum, and re-pumps whenever the vacuum is lost, be it by leakage or by pressing the trigger, which opens the valve. So basically, everything behind the nozzle is kept at a vacuum until you press the trigger. The idea is that this creates a big rush of air when you press the trigger. But IMHO it’s just not strong enough, and then it takes a split second before the pump realizes “oh, the vacuum is gone, let me pump again”. And the pump isn’t that strong, so the continuous vacuum it draws is quite anemic. Given its very high cost, I’d expect way, way better.

In contrast, the other three brands I’ve used (Weller, Den-On, and Pace) all use more powerful pumps that act directly when you press the trigger, and continue to pump until you let go. In the case of newer Pace gear, the pump is initially overdriven to double voltage for about a half second to create a big initial pulse of vacuum before continuing at normal suction, and the vacuum will always run a minimum of about 2 seconds even if you just tap the trigger briefly.

All the name-brand desoldering stations are expensive. Pace’s single-channel desoldering station goes for around $1000, in the middle of the pack price-wise.

[wraper]

And the pump isn’t that strong, so the continuous vacuum it draws is quite anemic. Given its very high cost, I’d expect way, way better.

I have previous X-tool with CU 100 A vaccum pump. I don't find pump anemic at all. The trick is to preheat boards with heavier copper and let a few seconds for joint to heat up before pressing the vacuum button. If it cannot pull all of the solder out it's not due to lack of sucking force but because solder is not entirely molten in the hole to begin with. Once it sucked solder from the surface, there is no longer good thermal transfer, and strong air flow provides cooling too. So solder in the hole stays solid. In case of failure I apply fresh solder and try again.

[dorkshoei]

All the name-brand desoldering stations are expensive. Pace’s single-channel desoldering station goes for around $1000, in the middle of the pack price-wise.

I have a Weller WR3000M.  I picked it up lightly used for $500.  The desoldering pencil is excellent.    I tested and the vacuum produced meets the published spec.   It replaced an Aoyue that was useless,  the pump barely produced any vacuum (measured at the pump output).  The Metcal that use dedicated compressed air look nice assuming you have such a setup.    Cleaning, replacing consumables (seals) and tinning tip is important but so is good vacuum.

The one thing I dislike about Weller is that in the USA they've decided to not sell replacement parts other than consumables.  In Europe you can buy a replacement pump, in the USA they require you pay a flat fee exchange for a new unit (obviously you can still order parts from Europe)

[dorkshoei]

In case of failure I apply fresh solder and try again.

As previously mentioned ground planes can make certain pins on thru-hole challenging.  If I can't get vacuum to work after applying fresh solder I'll usually use hot air to heat the last solder remnants and free the component but you have to be careful to avoid board damage

[KungFuJosh]

I have a Weller WR3000M.  I picked it up lightly used for $500.  The desoldering pencil is excellent.    I tested and the vacuum produced meets the published spec.   It replaced an Aoyue that was useless,  the pump barely produced any vacuum (measured at the pump output). 

I've been using my Aoyue for nearly 7 years, and it's always worked great unless something was blocking the airflow and needed to be cleaned out (which was rare).

However, if I could get a $3000 Weller station for $500, I would too! 😉

[dorkshoei]

I've been using my Aoyue for nearly 7 years, and it's always worked great unless something was blocking the airflow and needed to be cleaned out (which was rare).

I'd have to go back and look at my emails to Aoyue USA (SRA) but my recollection was the values I was seeing were 70% of the Aoyue claimed spec,  but that spec was pretty poor to begin with.

My Aoyue unit was definitely never great though it did get worse over time

Hardly a surprise, $150 product vs $2000

[KungFuJosh]

My Aoyue unit was definitely never great though it did get worse over time

Hardly a surprise, $150 product vs $2000

Oh, were you using the standalone gun version? Those were never great IME, including the Hakko version.

I have the 2703A+ station, and it still works great. The only time it was really a problem, was related to me being lazy (not emptying solder chamber or wetting the sponge) and screwing up the tip. Oops! Good thing I always have extras. 😉

ETA: There was also an issue where flux or residue got through the tubing into the pressure gauge, and the ball got frozen. I had to whack it will a mallet to get it to move, it was hilarious. I told that to the local Aoyue reps, and they sent me a replacement gauge for free, even though it was years out of warranty already.

[bdunham7]

the continuous vacuum system Tooki mentions sounds like the real solution. But likely expensive.

I recently upgraded to the PACE SX-100 desolder tool after seeing one in person and yes, if you do any significant amount of repairs requiring desoldering this is the way to go.  It cost less than the latest budget scope or another bench meter that I don't need.  It works for SMD applications too, just click on the link for tips.

https://www.tequipment.net/Pace/SX-100-6010-0106-P1/Desoldering-Irons/

[dorkshoei]

Oh, were you using the standalone gun version? Those were never great IME, including the Hakko version.

701A++  solder, desolder. Yes gun for desokder (another poor design element).

The pump was a joke when I examined it, must have been a $5 part.  Fine for the solder fume extraction side but not for desoldering .

Maybe they make higher end stuff but I doubt their entry level stuff is much improved from the above and this was my point/warning to others..

[KungFuJosh]

701A++  solder, desolder. Yes gun for desokder (another poor design element).

The pump was a joke when I examined it, must have been a $5 part.  Fine for the solder fume extraction side but not for desoldering .

Maybe they make higher end stuff but I doubt their entry level stuff is much improved from the above and this was my point/warning to others..

Oh, weird. That's similar design to mine, but with different parts. As I said, mine's been great. All the same, I don't expect a $300 station to work as well as a $3000 station...not that I've felt the need to upgrade at all. I'd buy the 2703A+ again. However, I actually don't care much for the fume extraction design. It's fine for what it is, but the solder/flux fumes cause build up in the line, and I'd rather use an external fume extractor than need to clean things. 😉

[tooki]

And the pump isn’t that strong, so the continuous vacuum it draws is quite anemic. Given its very high cost, I’d expect way, way better.

I have previous X-tool with CU 100 A vaccum pump. I don't find pump anemic at all. The trick is to preheat boards with heavier copper and let a few seconds for joint to heat up before pressing the vacuum button. If it cannot pull all of the solder out it's not due to lack of sucking force but because solder is not entirely molten in the hole to begin with. Once it sucked solder from the surface, there is no longer good thermal transfer, and strong air flow provides cooling too. So solder in the hole stays solid. In case of failure I apply fresh solder and try again.

I already know proper technique, it’s not that. I’ve used four different brands of vacuum desoldering equipment, and the Ersa was hands down the worst of them. (And I’m not anti-Ersa: I just chose and got a new Ersa soldering station at work.)

I don’t think you really understood the problem I described. The point is that the Ersa system relies on the pump drawing a vacuum and then turning off, so once that initial burst is gone, the pump isn’t ready to continue pulling. It takes time to detect the pressure change and turn the pump back on, and the pump isn’t as strong as others.

And proper de soldering technique is to keep a continuous, uninterrupted vacuum going while you keep the component leg moving, so that it’s kept away from the walls of the plated hole while cool air rushes by and cools it, preventing it from sticking. Watch the video I posted, please.

Also, with said proper technique, you never apply vacuum until you have already established that the joint is fully melted.

[tooki]

All the name-brand desoldering stations are expensive. Pace’s single-channel desoldering station goes for around $1000, in the middle of the pack price-wise.

I have a Weller WR3000M.  I picked it up lightly used for $500.  The desoldering pencil is excellent.    I tested and the vacuum produced meets the published spec.   It replaced an Aoyue that was useless,  the pump barely produced any vacuum (measured at the pump output).  The Metcal that use dedicated compressed air look nice assuming you have such a setup.    Cleaning, replacing consumables (seals) and tinning tip is important but so is good vacuum.

The one thing I dislike about Weller is that in the USA they've decided to not sell replacement parts other than consumables.  In Europe you can buy a replacement pump, in the USA they require you pay a flat fee exchange for a new unit (obviously you can still order parts from Europe)

That’s a shame. Availability of replacement parts is something where Pace and Weller generally excel. Or at least it was.

I got lucky: it took several years of patience, but I got a Pace ST-75 with SX-90 for about $115 shipped — and it came with about $100 worth of brand-new tips and consumables! All it needed to restore it to like-new performance was a $5 front seal.

[tooki]

Oh, were you using the standalone gun version? Those were never great IME, including the Hakko version.

FWIW, the Den-On SC-7000Z desoldering gun is excellent. But it also costs twice as much as the Hakko!

[tooki]

the continuous vacuum system Tooki mentions sounds like the real solution. But likely expensive.

I recently upgraded to the PACE SX-100 desolder tool after seeing one in person and yes, if you do any significant amount of repairs requiring desoldering this is the way to go.  It cost less than the latest budget scope or another bench meter that I don't need.  It works for SMD applications too, just click on the link for tips.

https://www.tequipment.net/Pace/SX-100-6010-0106-P1/Desoldering-Irons/

Of course, that’s the handpiece without a station to run it with, nor even the stand! (So really, that’s the part intended as a replacement.) If you don’t already have a station, it’s really $1000 to get started.

As far as I can tell, Pace has the best selection of desoldering tips, and from experience, they’re a joy to work with!