SurfaceMountDeviceRework

Introduction

What is SMD? SMD stands for Surface Mount Device, and the technology is what most manufacturers now use to put electronic components on circuit boards. SMD parts are generally smaller than their through-hole counterparts, and are soldered directly to pads of exposed copper on the circuit board. When a DIYer first encounters SMD, their initial reaction to these tiny components is often that they may be too small and delicate for hand assembly, or that it may be too difficult to modify a circuit without damage. But, as we'll see, working with SMD components can actually be faster and easier than through-hole construction. All that's required are the proper tools, and a little patience and perseverence to learn the techniques and get comfortable with them. For anyone who hasn't worked up the courage to venture into SMD construction, I highly recommend you give it a shot - I think you'll be pleasantly surprised!

Tools

Nothing is more important in SMD work than having the right tools. An experience with the wrong tools is enough to turn some people away from SMD for good. However, with the right tools, SMD work can become significantly easier than through-hole work. Here is a list of some essential items you'll need to to SMD work effectively:

- Fine-tipped soldering iron with beveled or bent tip. Temperature controlled irons are best.

- $25 DIY hot-air soldering pencil (see below)

- Liquid flux

- Liquid flux dispenser bottle or flux pen

- Quality, small diameter rosin core solder (eg. Kester or Multicore 0.025in., maybe even 0.010in.)

- Flux remover (rubbing alcohol or 100% pure acetone is best)

- Q-tips or other cotton swabs for cleaning

- Extra-fine solder wick - flat copper braid impregnated with flux

- Fine point tweezers

https://www.diyaudio.com/files/hifizen/supplies_all.jpg

There are a number of other tools which can make your life easier, but these are the essentials. Without the above items, your SMD experience could be downright miserable. Perhaps one of the most important if you're going to be removing SMD parts is the hot air pencil. This tool is cheap and easy to build, and will save you unbelievable grief when trying to desolder parts from a circuit board, especially larger components with many leads. Not to mention that hot air rework places much less thermal stress on components and circuit boards. I basically followed the directions posted [here]. I used #3 coarse steel wool, and silicone aquarium hose. The silicone tubing has better heat resistance than the plastic hose, and is also more flexible and easier to stretch onto the desoldering iron where the bulb was.

https://www.diyaudio.com/files/hifizen/airpencil.jpg

https://www.diyaudio.com/files/hifizen/swool_pump.jpg

A good soldering iron is also necessary. Temperature controlled stations with an adjustable temperature are best, but the tip shape makes the biggest difference in how well you can solder SMD parts. I prefer a bent tip like the Hakko [900M-T-0.2RB] or Metcal [SSC-X26A], but a basic chisel shape like the Hakko 900M-T-S7 is almost as good. The advantage of these tip shapes is that they give you a very fine point for working on individual fine-pitch pins, but also a larger flat surface you can use to contact multiple pins simultaneously, or to spread solder down a row of pads, or lay flat against solder wick. Note the cellulose sponge, which is kept moist with distilled or demineralized water. This is essential for keeping the tip clean. There are really no acceptable substitutes for this cheapo item, and it will pay for itself many times over with extended tip life and effort/frustration saved. Note that the solder sucker visible in the photo below is not a necessary item. In fact, I recommend against the use of solder suckers in SMD work, as they can suck SMD pads right off the PCB. In through-hole work, this is usually not a problem since the pads are anchored down by the through-plating. The only time you might find one useful is if you have a large blob of solder you need to get rid of.

https://www.diyaudio.com/files/hifizen/solder_station.jpg

The importance of flux is not to be underestimated. This is another absolutely essential item. Liquid flux will keep your solder joints clean and shiny, and ensure quick thermal transfer from an iron's tip to the solder joint, as well as adequate wetting and capillary action to draw molten solder into a joint. You can use either a flux pen to paint this on, or a needle dispenser (which I prefer) to deliver small quantities accurately. Of course, you don't want to leave flux hanging around on your board after it's done it's job. You can always buy professional aerosol flux remover, but this is expensive (not to mention messy with all that solvent spraying around), and there are excellent alternatives. One of the best flux removers I've used is pure acetone, which is available from cosmetics and drug stores as nail polish remover. Try and get the "professional" 100% pure stuff, which doesn't have the other additives they put into most low-grade nail polish remover. Another decent flux remover is ordinary isopropyl alcohol, also available from drug stores. You may be able to get pure denatured alcohol from a paint supply store as well, and this will be better than the 70% first-aid stuff. Cotton swabs are useful for applying and subsequently soaking up the contaminated flux remover, as well as for some light scrubbing to help remove hardened deposits of burnt flux.

A high-quality fine braid solder wick is indispensible for removing solder bridges between pins of fine-pitch SMD devices, and for cleaning solder pads. A good solder wick can restore the pads to factory-fresh condition - the efficacy of this simple item is truly amazing.

Fine-point tweezers. This one speaks for itself. Most SMD components are very small and require delicate handling. A pair with fine, needle-like curved tips is best for several reasons as I'll describe later, but a good starting point is the 7-SA-SE tweezers from Selecta. These are just the right geometry for SMD work, and have a nice, light springiness so that you get good feel and don't have to squeeze too hard to grip a part.

https://www.diyaudio.com/files/hifizen/tweezers.jpg

There are a couple of other items which may come in handy, but these are optional... tip tinner to keep your soldering iron's tip in top condition, and a set of dental picks / probes for lifting components, fixing bent component leads, and scraping between fine-pitch pads. Beau Tech has some nice probes made just for SMD electronics work. ChipQuick? low-temperature soldering compound also comes in handy from time to time, especially if you're working with larger components. A toaster oven can also be handy in certain situations, and a vacuum pick-up tool is useful for handling larger parts without damaging the pins. If you don't have a vacuum pick-up tool but need to move a large SMD part, a short length of Scotch tape will work, so long as you're careful not to damage the pins when separating the tape from the part.

Lastly, a good magnifier can be very useful. This goes hand-in-hand with good lighting, so first avoid unnecessary strain on your eyeballs by making sure your work area is well lit. I am still relatively young, and blessed with good eyesight (at least for now), so I generally do not use a magnifier. I do however use one of the stereo microscopes in the lab at work for some fine-pitch work, but this is an expensive instrument, and therefore not really within range of the hobbyist workbench. Perhaps someone else can comment more on what kind of magnifiers work best?

Removing SMD Parts

If you're ever in the position of modifying some commercial gear, or perhaps just re-thinking some of your prior art (assuming of course that you used SMD parts in the first place), then you'll need to be proficient at removing SMD parts - preferably without damage to either the part or, more importantly, the printed circuit board. Without the proper tools, this can be a daunting task. However, once you learn the proper way to get the job done, you'll think removing through-hole parts is a major pain by comparison!

There are two general rules which apply to SMD work: #1 - the more pins it has, the more difficult your work will be, and #2 - the more flux you apply (within reasonable limits of course), the easier your work will be. Let's have a look at some specific examples:

According to rule #1, a small 0402 (0.04 inch by 0.02 inch footprint - verry tiny!) sized resistor or cap is going to be the easiest SMD type part to remove. This turns out to be true, although parts of this size will likely be toast once you're done (it will probably burn up on the tip of your soldering iron). For parts up to about 0805, or maybe 1208 or larger depending on your iron, you can touch both ends of the part simultaneously with the tip of a soldering iron. This is where a hook shaped or chisel style tip comes in handy. That longer flat surface will allow you to approach a part from the side, simultaneously touching both soldered ends, and slide the part sideways off the pads once the solder becomes molten. If you've followed rule #2, and applied a small droplet of flux over the part (or maybe a larger amount for the 1208 sized parts), then the flux will instantly transfer heat from your iron into the solder joint, and you should be able to remove the part in mere seconds. The flux will also prevent the formation of oxides, leaving a nice shiny solder-covered pad behind. Keeping the tip of your iron clean with regular wipings on a moist cellulose sponge, and occasional use of tip tinner to remove tough oxide and crud build-ups will go a long way in ensuring that this operation (and indeed any other SMD soldering job) will go smoothly. There is, perhaps, one superior technique for removing these sort of small two-pad parts, and we'll get to that in just a moment.

Now, as we progress towards larger parts with more legs, the challenge becomes greater, and one must employ different techniques to achieve satisfactory results. I've seen, and tried, many different methods for removing multi-legged SMD parts. One of the first techniques I tried was quite desructive: clip off all the leads and remove the main body of the part, and then go around with a soldering iron and "solder sucker" cleaning up each pad individually. This method is slow and prone to board damage, and of course the part becomes practically useless. A similar method involves using either a length of fine-guage wire, or perhaps a small piece of very thin stainless steel shim. As each pin is heated, a fine wire or shim is slid between the pin and it's pad, effectively keeping them separated while the solder re-solidifies. A key part of this technique is to move the wire or shim only parallel to the surface of the PCB, thus avoiding any vertical lifting forces which could pull a pad or trace up from the fiberglass board. Even an invisible lift at the edge of a trace or pad will expose the copper underside of that pad to possible corrosion, leading to eventual degredation or failure of the circuit. So here's another good rule to remember: try to avoid applying any vertical forces which could pull up a copper pad or trace.

In any case, all of the above methods pale in comparison to the true professional's method of choice: hot air. There are several reasons why hot air works better than the old fashioned iron, not the least of which is that you can simultaneously heat all of the pins on a device. My eyes nearly bugged out the first time I witnessed the use of hot air for SMD parts removal... After just a minute or so of heating, the technician lifted a 208-pin TQFP (0.5mm pitch!) off the board like it had never been attached in the first place. Subsequent examination of the cooled down part revealed not one single bent or damaged pin. Indeed the part looked nearly indistinguishable from a brand new one! This very large and expensive part could have easily been soldered directly on another board with no repair work necessary! There is another reason why hot air is superior to direct heating: thermal stress. Hot air gently and evenly heats a component, whereas heating with a soldering iron causes very small localized hotspots around the solder joint being heated. This causes the most problems with SMD ceramic capacitors, which can fail very easily due to thermal shock, which can crack and delaminate the layered construction of these tiny parts. The failure may be totally invisible to the naked eye, and will only show up when it's time to debug the circuit. Worse, it may not show up at all until later in the life of the circuit. for this reason, re-use of small SMD capacitors is not recommended, especially if soldered with an iron. There are only so many thermal cycles those little parts can take, and they are usually only designed for ONE.

So, if you've taken the time to construct the $20 hot air pencil mentioned in the parts section, you now have a very powerful tool for working with SMD parts. Although this small hor air pencil will not be large enough to handle big parts like the 208-TQFP, it goes a long way, and a little creativity will get you the rest of the way.

For larger parts, a very reasonably priced heat gun which works very well is the Ideal Tools '101 Plus' or 'ESD Plus'. I use it with the 46-922 nozzle. A word of caution when using a powerful heat gun: beware of excessive heating of electrolytic caps - they will explode violently if you heat them too much! If you have any electrolytic caps near the area you're heating, either shield them with some aluminum foil, or remove them before applying the heat gun. You've been warned...

The basic technique for working with hot air, is to heat up the whole component (just the leads, acually), to the point where the solder on every pin is molten. At that point, the chip has zero mechanical adhesion to the board, and would just fall off if you were to tilt the board on it's side. Of course, you'd probably rather lift it carefully off with a vacuum pick-up tool or a pair of fine tweezers. And that's it! And, if you remember rule #2, you'll find that the application of liquid flux over all the pins before heating helps ensure an even and efficient transfer of heat (yes, even from hot air), and will prevent the formation of oxides. For small components like SO-8 devices, the $20 hot-air pencil should be sufficient to heat all the leads at once, and gentle nudge every now and then will confirm when the solder is all molten. For larger components with only two sides that have pins, you may be able to heat one side at a time. A very gentle lifting action from beneath the chip with a dental pick or fine-point tweezers will reveal when the solder is all molten, at which time you can bend the part up slightly, with the leads at the other side of the package acting as the hinge. Then, go heat the other side till the part falls off. For the very largest of packages, you may need to get clever... toaster ovens are good for heating up a whole board gently, and preventing areas from cooling too quickly after you've passed over them with the hot air pencil. ChipQuick? may also be useful since it will allow the solder joints to remain liquid to a much cooler temperature. With big parts like QFPs and on up, investing in a hand-operated vacuum pick-up tool will make the manouvering and handling of the parts much easier.

A sticky situation: Sometimes, a manufacturer will glue SMD parts down to the board before soldering them in place. This is usually for the purpose of holding the parts in place while they're wave soldered, or moved from the pick-n-place robot to the reflow soldering oven. Unfortunately, this glue is usually very strong and heat resistant, so it seems like it might be a big pain to remove the part. Of course, the glue manufacturers have taken into account the possibility of rework, and made the glue just heat-resistant enough to withstand a pass through a reflow oven or wave soldering machine, but weak enough to break down after prolonged exposure to heat, but before the PCB starts to burn. When dealing with glued parts, patience is the name of the game. Start by applying a steady stream of hot air directly on the glue, and hold it there for some time. As the glue heats up, it should soften somewhat before starting to crumble. You can probe at it periodically to check if it's starting to fall apart, and when it is, then you can proceed with making sure that the solder joints are molten and the part should lift off without too much effort. Beware of applying too much force to remove a component, or you may rip up traces or pads from the board! Also note that this type of component glue will often re-harden if it is allowed to cool. The trick in many cases is to try and direct some hot air under the component, where a blotch of glue might be hiding. In the photo below, you can see the red glue left behind after removal of an 8-pin opamp. In the next photo, you can see the results of applying further hot air and gently scraping the glue away with the narrow but blunt tip of a pair of tweezers.

https://www.diyaudio.com/files/hifizen/rework_demo1.jpg

https://www.diyaudio.com/files/hifizen/rework_demo2.jpg

Clean-up is the last step in SMD part removal. In the usual case, small bumps of solder are left behind on the pads after the part has been removed. However, to ensure the best possible surface planarity and easy positioning of the new part, you'll want nice, flat, shiny pads like those in the above picture. This is best done using solder wick. Simply place the end of the fine copper braid flat over the pads, and put the broadest, flattest surface of your soldering iron's tip down on top of it. The heat will transfer down through the braid, eventually melting the flux in the braid and the underlying solder. Capillary action will draw the molten solder up into the braid, and you can then "wipe" off the pad by moving the braid and iron tip together, leaving a nice flat, shiny pad. When the end of the braid becomes saturated with solder, simply clip it off and work with the next section which will still draw flux up into it's braid. Once again, the application of extra liquid flux can be a help, and certainly won't hurt. You want to make sure that the pads are oxide-free and shiny so that solder will flow nicely onto the pad when you return to install the new part.

As a final step before inserting the new part, you may find it necessary to remove any burnt flux deposits. Simply apply the solvent of your choice (I prefer 100% acetone, but alcohol also works nicely) to a cotton swap and scrub away. For maximum effectiveness, you can leave a small pool of solvent on the board to dissolve tough deposits, perhaps with the assistance of a dental pick to carefully scrape away the really thick deposits. Once the old flux and deposits are dissolved, you should soak up the loaded solvent with a tissue or blow it off the board to prevent re-deposition when the solvent evaporates. While we're talking about flux removal, a useful tip comes to mind: flux residue can make many IC part numbers difficult to see, even invisible (despite being transparent). A quick cleanup with some acetone can make that part number much easier to see.

Soldering SMD Parts

Now, the easy stuff: soldering SMD parts. Quite possibly the easiest SMD parts to solder are chip parts... basically your typical two-terminal devices: resistors, capacitors and inductors, diodes, LEDs, etc. Almost no preparation is necessary to install one of these. Simply apply some liquid flux to the solder pads, then place the component down with a pair of tweezers. Use a fine-tipped iron, and wipe the tip clean on a damp sponge so there is little more than a thin film of molten solder left on it. Pick up a small droplet of molten solder by touching the tip to the end of some fine solder. Now, while holding the part in place with the tweezers, simply touch the little ball of molten solder you just picked up to the L-shaped soldering surfaces formed by the part and it's pad. For most SMD parts, the iron need only remain in contact with the pad for a fraction of a second. The liquid flux already in place will almost instantly heat and wet both surfaces, and the solder should flow onto them both. When you pull the iron away, a nice little fillet of bright, shiny solder should be left behind. Touch the other side, picking up more solder first, if necessary. So long as the little bead of solder at the tip of your iron is relatively fresh, it will flow quickly and effortlessly onto both surfaces of the joint. When the iron tip has accumulated enough oxides to lose it's nice wetting properties, simply wipe it again on your damp sponge, and you're ready to go for another round.

A slight variation on the above method involves depositing a small mound of solder onto the pad before applying the flux and positioning the component. In this case, the solder already present, perhaps with the addition of a little more from the tip of the iron, will simply reflow and form the joint. The presence of liquid flux is important here, as it will coat the surfaces to be joined and help the solder to flow into place. However, I prefer the previous method, since it can sometimes be difficult to position a small component over these bumps of solder. The other method will ensure that the component sits flat down against the board, giving a better joint and a neater appearance. If given the choice, clean the pad off with solder wick first, and then solder the part in place.

These two methods are very simple, and become almost effortless after a little practice. However, larger parts are not quite as easy...

When dealing with a multi-legged part, the best soldering method usually involves "tacking" the part in place with diagonally opposite corner pins to get it accurately positioned over the pads. Start with all the pads clean and flat. If there are solder bumps on the pads, you'll have a hard time positioning the chip, and getting it to stay where you put it. Apply some liquid flux to all the pads, then place your chip down. Once aligned, pick up a tiny speck of solder on the tip of your iron. A quick touch of the iron tip to the edge of the corner pad should pull some solder under the pin, bonding it in place. Getting this first pin positioned accurately is important, so if it's not positioned quite right, carefully heat that pad again and tweak the IC into alignment. When you get the chip right where you want it, you can now tack the opposite corner, and then work sequentially around the device to get all the remaining pins soldered down. Don't worry if you create a solder bridge between two pins in the process of tacking it in place, these will be taken care of later. The same goes for the tack joint... don't worry about it if it looks bad. The primary purpose is just to hold the chip in place for you. Once several other pins have been soldered, you can clean up any mess you may have made while tacking the chip down. Don't hesitate to use some good magnification and bright light while positioning the chip. This is the most important step, and you want to get it right.

Now, there's something of an art to soldering very fine pitch devices down, and there's two ways of doing it:

1. Use a very fine tipped iron, and go pin-to-pin, applying liquid flux and just touching the edge of the pad and pin with a small droplet of solder at the tip of the iron. Touch the pad first if you can, at the outer edge, and let the tip slide in till it touches the pin. With the help of the flux, the solder should flow nicely between the pad and pin, forming a perfect joint. If you had too much solder on the end of your iron, you'll get either a bridge to the next pin or pad, or you may just wind up with a large bump of solder on the joint. Too little, and you may get just a tiny column of solder between the pin and pad, not visible from the edge of the joint, or perhaps no connection at all. Once you've done a few pins, you'll get a feel for the limits.

2. This is a bit more of a brute-force method, and requires a little pratice to get right. Instead of a fine-tipped iron, you use a broad, angled chisel tip, maybe 5mm across! Apply liquid flux down the row of pins, and blob some solder on the length of the iron's tip, as usual. Now, just push the chisel edge into the row of pins (again, try and start by touching the pads first, then the chip pins at the very tips), and slide the chisel edge along. If done right, it should coat the pads and pins with solder, leaving perfectly formed joints behind, but won't leave bridges between pins. You can do a fairly large IC in just one or two minutes using this method and the tack positioning technique! Again, the amount of solder on the tip of the iron needs to be right... too much will leave shorts, and not enough will be, well, not enough.

Now, sometimes you will end up with a few solder bridges. Occasionally, you can just wipe off the iron tip on the sponge, and then simply touch the tip to the two bridged pins, sliding it away and in the process picking up the offending solder. But, if this isn't working, or if you have a bunch of pins close together which are shorted, some solder braid can be a great help. Just place the braid flad agains the row of pins, then heat the braid with a larger flat surface of your iron's tip. Same as cleaning up PCB pads. Once the braid is hot, it's flux will melt, conducting heat to the solder shorts, and then drawing them up into the braid. "Wipe" the braid away with the iron still in place, and if all goes well you should be left with clean pins, not shorted. Sometimes this will leave the joints a little solder deficient, so you may need to apply a bit more solder. However, don't overwork a solder joint. Sometimes, it's better to leave a slightly less than optimal joint instead of repeatedly heating the pin and trying in vain to perfect the joint.

So there you have it. That's pretty well everything you need to know about soldering SMD down to PCBs. Now, on to something even more fun: DIY techniques for using SMD parts...

DIY-SMD Construction Techniques

For DIY construction, we can improvise, since we're not constrained to a 2-dimensional PCB as commercial mass-production is. The following are a rough categorization of some of the techniques I've used, but they are really all one and the same, so feel free to mix'n match and improve upon them as needed. If you have additional tricks or things to try, by all means, please contribute your suggestions here in the wiki!

Dead-Bug Construction

Dead bug construction using SMD components is done pretty much the same way as with through-hole stuff. Mount or glue the component upside-down to your substrate or maybe right on top of a larger IC, then attach your wires or other components directly to the device legs. A spot of cyanoacrylate adhesive (CA, superglue) works well, and will (somewhat slowly) dissolve in acetone should you need to remove any unwanted glue. One useful thing about dead-bug construction is that you can bend the pins to give you more clearance or orient a solder joint in a manner that makes it easier to construct. Just don't try bending SMD pins too much, since their delicate nature makes them prone to breakage if bent once too many times... Try the following trick if you just can't get your soldering iron in there: bend every other pin up 90 degrees, or even fold it flat against the belly of the device. Or, do both, so that you have a 3-pin repeating pattern of pins left pointing straight out, bent up 90 degrees and bent right around. This should give you lots of room to play with when soldering to the pins. Be sure to mark where pin 1 is located before you glue or otherwise mount the chip, and remember that the pin count will be a mirror image of the right-side-up chip.

For dead-bug construction, small chip resistors and capacitors can be soldered directly to the device pins, standing on end or whatever arrangement is convenient. Power supply decoupling caps can be soldered directly to the pins too, even larger electrolytics. You'll just have to be careful not to wiggle them too much after that. For point-to-point wiring, try some fine guage solid wire. Kynar, Teflon or Urethane coated (magnet wire) all work, and 30-32 awg is probably about the only size you'll need unless you expect the wire to carry a significant current, power, or an analog signal terminated in a lowish impedance. Don't forget the flux!

SMD-DIP Adapters

my random notes/reminders for this section: IC sockets / headers, "modules", draw'n quarter floating trick, photos?

Insulator and Magnet Wire Method

Visit this page of very cool examples at Takeshi Akamatsu's excellent website: https://elm-chan.org/docs/wiring_e.html

Here are some of my notes on the technique... For those who don't recognize it, UEW coated wire is just urethane coated magnet wire. There is a small trick to using this stuff, since it isn't immediately apparent how to "strip" the insulation. Don't bother with solvents and the like, or scraping and other such time consuming methods. The real trick is... you guessed it... lots of flux! ;) The clipped end of the wire will allow hot flux to get in under the urethane coating and break it down. Just dip the end of the wire in liquid flux and heat it up on the tip of a soldering iron which has a little blob of molten solder present to tin the wire as the insulation breaks up and comes off. It takes just a second, and this method should give you around 1mm or 2mm of bare, solder-tinned lead to work with, which is plenty for SMD work. The burnt and removed insulation may leave a little tiny mess on the tip of your iron, but a quick swipe on a damp sponge will remove the crud before you make the joint with your newly tinned wire.

Akamatsu-san uses Kapton tape as an insulator to mount the chip onto, but a little piece of mica works too, although mica is difficult to glue. Both Kapton tape (at least when purchased by the roll) and mica are a little expensive to put under every IC, so I need to do some more experimentation in this area. Lots of things should work here, including scrap PCB material... just be conscious of the material's melting/burning point, and it's potential to retain static charges which could damage sensetive ICs. I've considered using a small piece of plastic under the IC but not the pins. If it's thick enough, the pins will be raised up off the PCB, but you lose the ability to put downward pressure on the pins with your soldering iron tip.

House-o-Cards Construction

Just what it sounds like! If you're working with smaller SMD components like resistors, caps and single transistors, you can stack things and build little 3-dimensional structures. I've got some nifty and impressive reworks to photograph for this section... I think Peter Daniels will be jealous! ;)

Almost done... maybe just a few more comments and photos to add...

- hifiZen -

Further Comments and Suggestions:

- add your comments and ideas here!

- cbm5 - I have also found that an ordinary hot air gun can be used to remove the larger SMD parts. If you need to protect nearby components, you can use kitchen foil or use a nibbler tool to make a square mask in a piece of metal. If you use one of those little drill press stands for hand drills, you can spin the hot air gun down to the working surface and get the airflow just where you need it. The key is to heat the pins faster than the device. I use a dental pick to gently wobble one corner of the device while heating, so I know exactly when the device is loose. Then I use the dental pick to flip up the device where I can grasp it with tweezers, retracting the hot air gun at the same time. It really does work, and if you make sure that you only heat the device until the solder melts, you won't damage the part. I have successfully used this method to replace 208-pin QFPs.

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