I would like to ask you all what suggestions you would have for a hot air rework tool. I wouldn't be using it often but occasionally I get a pc board with smd (leaky) caps that need replacing. I see inexpensive ones on eBay in the $60-$100 range. I wouldn't mind spending a bit more, if necessary, to get something of quality. It sure would be nice to have a tool that makes it easier to remove these parts without damaging pc traces.
Thanks for your replies.
-- David Farber Los Osos, CA
You can't do SMT rework very well without a hot air gun. The days of solder wick and solder suckers are over.
I bought a Saike 852D+ on eBay for about $75. That was 3 years ago and it's still working nicely. Something like this, but with a different assortment of 4 tips: My logic was similar to yours. I wanted to buy something cheap so I could see what was really needed in an SMT rework station. I would then buy something better, and sell this one. The 852D+ turned out to be good enough, so I never upgraded. There are updated models now available.
You'll probably need to buy an assortment of different nozzle tips. At about $10/ea, a few of those can cost more than the hot air rework station. Note that the nozzles are different for BGA packages. For example:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Why would you use hot air on leaky caps? Only 2 connections. Plus they have a tendency to explode. Use 2 good soldering irons. You are more likely to need a good binocular microscope to check for dissolved traces and to check your work afterwards. You DO need hot air for smd chips however and buy one that displays the air temps, (unlike me wot didn't and then had to buy another better one).
I was following the advice on this site.
I just bought the 852D model shown on eBay for under $60.. You make a good point about using a microscope. I'll look into that as well.
Thanks for your reply.
-- David Farber Los Osos, CA
I use the HAKKO 950 SMD HOT TWEEZER as part of my Soldering workstation. Very easy to use and no damage to PCB.
I Have a friend that used a hot air gun on his board, and blew half of the components off!
Colin
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I have the 852D+. It's fine on small stuff, but nowhere near big enough to desolder a GPU.
I bought a cheap USB endoscope on ebay. I was surprised how well it worked as a low power microscope. Much easier to manage than an optical one. I have a stereo zoom microscope with the lens that extends the distance between the scope and the work. It's still hard to get tools in the available space, and the depth of field is miniscule. The endoscope camera solves both those problems.
Still need the microscope if you are looking for fractures on a flat surface, but the endoscope can easily go where a huge microscope can't.
I have some boards, mostly through-hole, that I want to salvage parts off of. I tried using my Milwaukee 750 heat gun (looks like
About how much (like, how many square inches) of the PCB do you heat up at once? With the hot air gun, I found that I couldn't get the whole PCB hot enough at once (it was about 2" x 3"); I had to work in smaller sections.
Thanks!
Matt Roberds
But the trick is, the adjacent area is "prewarmed" so it will take less time to heat up than the initial area. It seems to take "forever" (not literally) for the first area to heat up enough, but then the rest goes relatively fast, so long as you keep at it.
I started witha propane torch, but it tended to burn the board (which I don't care about, but I didn't like the smoke or smell). Even a heat gun is hot enough to do that if you hold it in one place too long. But then I ran out of propane in the tank, and either bought the heat gun to continue, or switched to the heat gun I'd already bought, I can't remember.
I bought a little butane torch, and that's been handy a few times for getting something specific off a circuit board for the part, but it doesn't hold enough butane to do much work.
Michael
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Tried the 2 soldering iron idea and it wasn't very good. For SMT 'lytics we grab the top with cutters, push down and twist 1/8 to 1/4 turn. Clean the solder residue, hit it with a flux pen and attach the new cap. Fast and rel iable. Hot air gun for caps is way too slow and causes more damage than sim ply twisting them off. I use this technique when re-capping the servo board s in Sony SRW machines. I've damaged a total of 4 pads from 1008 caps and t hose were from the first few boards. A good soldering iron like a Metcal is far more useful to me.
That heat gun is made for shrink tube, which runs at a lower temperature range. You want one that will go to about 1000F so that you can stand back away from the PCB. Solder melts at about 400F.
If I can find the spreader nozzle used for paint stripping, I attach that to cover a larger area. For a heat gun, I use some piece of no-name junk I bought for about $20. It's major feature is that when it's cold, the power cord is incredibly stiff and difficult to handle. Something like this: However, I prefer the propane torch and paint stripper spreader nozzle. The idea is to NOT produce a hot spot that will destroy everything in its path if you momentarily stop moving the heat source. The propane torch is very good at scorching the board, so I use a spreader.
I think the biggest PCB I've done was about 8x10. I couldn't do the entire board at once. I heated about 2 inches of the edge of the PCB until the solder melted, and just banged it on the table to remove most of the big parts. I then finished the job with a scraper. That gave me a clear area to clamp into the bench vise. I then heated about a 4"x4" area and launched the parts by bending and releasing the PCB. Eventually, I moved my way around the board until everything was removed. Small and thin boards are a PITA because they don't offer much spring tension, so I have to scrape them clean (with a stainless scraper).
You'll need to continue applying heat while launching the parts. The problem is that the PCB will cool down very rapidly (very little thermal mass) if you stop.
Biggest headache was cleaning up the solder spatter on the wall or carpet if I missed the cardboard box. 2nd biggest was cleaning off the excess solder from the tiny SMD parts.
Reminder: Welding gloves, face shield, safety glasses, and ventilation.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I found this page really interesting about parts recycling:
Beginning:
So, now you know where I buy my phone repair parts. My dead phone collection isn't as impressive. Photos later.
Locally, there's actually a demand for old phones. I was getting phones for about $5/ea from the local recycler, until someone offered them more money. Since I wasn't making much money fixing phones, I declined to start a bidding war.
Note the heat guns in the photos. They look brand new and recently installed with tape. My guess(tm) is that these burn out rather often. They're not made for continuous operation. It's NOT a cheap heat gun and includes an LCD display for monitoring temperature: at $300 list price.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I paid $20 on sale for my Black & Decker heat gun, sometime in the early nineties.
I've used it heavily from time to time, but no, not full time.
But what I have noticed is the metal where the heat comes out has corroded, I think I've lost some of the metal already. I assume that's not from the heat, but from something coming off the circuit boards to corrode the metal.
Michael
I have mixed feelings of Black and Decker quality. Some products are quite good while others suck. B&D also owns DeWalt, Porter Cable, and Dustbuster, all with similar mixes of quality and junk.
Chome plated nozzle or stainless? The idea is to have a shiny nozzle so that it will reflect heat, instead of absorbing heat. Chome plating is porous and will pass some water, which accellerated by the heat, eventually rusts the underlying steel. Usually the chrome plating flakes off first, possibly due to differences in thermal expansion rates. I can't check today, but I think my nozzles are all stainless.
I don't believe it's from anything smoking or outgassing on the PCB. The air intake for the heat gun is far enough away from the PCB to not suck in any gasses.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I gave up on B&D hot air guns 20 years ago. They may have changed but then they used mica as the matrix for the heater wire. If the heater broke it was impossible to repair by crimping a bit of stainless steel nicad strip over the join as the mica broke to flakes. I went for Bosch which use/used? ceramic matrix. Incidently not had to repair the heater on it for many years. Perhaps heater is Kanthal wire and now the Al component has fully migrated to the surface and no hot spots left
My rework station arrived a couple of days ago. I watched several instructional videos to get an idea of how to use it properly. I found that using the smallest diameter air flow nozzle and a temperature of around 280C worked very well on the leaking caps. I had to remind myself to be patient until the solder was hot enough before attempting to pull the cap off of the board. I also noticed that if you increase the temperature too much, it's quite easy to unintentionally remove neighboring components. All in all, this is a big time saver and a very safe way to keep the pads from getting ruined.
Thanks for your replies.
-- David Farber Los Osos, CA
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