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surface mounting techniques

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windozeuser

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Hello :) What methods do you guys use for surface mounting components. Also, do you recommend any glue and other tools that work well from your experience. I personally am just starting to learn surface mounting, and hand soldering and gluing the components on the PCB. I can see why engineers and technicians shouldn't carry screwdrivers in their pockets, and they become bald real quck like... :lol:

I know two different methods, one is gluing then soldering, and the other is building up and placing the component leads on the built up solder. Then heating it until it adheres to the joint.

Thanks!
 
I never used glue. For a resistor, fine point soldering iron, tack one side while holding it down with a tool, then go back and hit the other pad. No need to wet the pad beforehand.

For devices with a lot of closely mounted pins, a lot of people using a rolling ball technique. They use a blunt tipped iron, start on one side, make a small blob of solder and drag the point and the blob along wetting the pads as it goes.

Others use solder paste (Zephyrtronics makes a good one) on the pads and use a blunt dry soldering iron to melt it along.

You can use solder paste and heat it in the oven. First mild heat to drive off the paste's water-based solvents, then a sudden heat up to the melting point of the solder. Some odd plastic components cannot survive this process.

Me, I like to oven dry the paste then use a Weller soldering iron with a heat blower (not blowtorch!) pencil tip. Very fine line of heat for doing very fine pins. I've got pkgs that have such fine pins I had no success with soldering iron methods.
 
Like Oznog said, for small components like resistors, hold the part down with tweezers and quickly heat the pad and any solder already on it will form a nice joint. If the joint doesn't look right, dab a bit of flux on it and reheat the pad. It will flow properly then.

For fine pitch packages like 80-pin TQFP and the like, I first tape the part down to the board making sure all of the leads and pads line up. I then smear a line of solder down one side of the pins to hold it down. I then take off the tape and smear solder down the remaining sides. I then go back with solder wick and quickly go over each side. All the excess solder is wicked up and you are left with perfectly soldered part. It may take a bit of practice so you don't pull up too much solder but once you get the hang of it, it goes very quickly. Almost forgot to say that I use a general purpose screwdriver tip in my iron even when soldering 8mil pitch devices.
 
windozeuser said:
Hello :) What methods do you guys use for surface mounting components. Also, do you recommend any glue and other tools that work well from your experience. I personally am just starting to learn surface mounting, and hand soldering and gluing the components on the PCB. I can see why engineers and technicians shouldn't carry screwdrivers in their pockets, and they become bald real quck like... :lol:

I know two different methods, one is gluing then soldering, and the other is building up and placing the component leads on the built up solder. Then heating it until it adheres to the joint.

Thanks!

If you use glue, you'll quickly get tired of dealing with the mess and extra time it takes for every component.

I use Tweezers, fine small soldering iron tip. That's it! Like someone else said, tack one side down then the rest flow nicely since you don't have to hold the part down. I've used this method to re-work fine pitch parts like TSSOP, VQ.. down to 0.5mm pitch. Lower than that & I use paste & heat gun for reflow.

One thing to be careful about is using too much solder. It doesnt require much and works better with as little as you can get away with.

For pulling parts off, use heat gun for most cases. But sometimes I also just hit the part with the soldering iron...
 
For IC's I wet one pad and tack the IC down so that everything lines up, then solder the rest with a decent amount of solder, not worrying about bridging. Then I go back with some solder wick and soak up all the excess. It's fast and easy and does an excellent job. I think Evandude on this board has a tutorial in his sig that shows something similar.

As for 0805 and 1206, I never even tried tacking them down without wetting the pad first. It doesn't seem like they have enough of anything to hold them to a pad without it. I'll try it next time.
 
What temperature is the iron? Solder wick would scare me, all the heat on the junctions..

And my eye site would kill me anyway.
 
I should be clear that you don't want to start by adding solder to more than one pad before the component, if you do this at all. If you put solder on 2 pads then the device will be left raised on top of whichever pad you didn't heat first. Once you do the first pad it'll fix it in that place, with the other end hovering over the pad.

I should also stress just how useful that Weller butane-powered soldering iron with the heat blower tip is. I mean, this is REALLY excellent for this work! You can get these kits on eBay for $20-$30 and they have dandy soldering iron tips and is a great tool for the toolbox anyways. But the heat blower tip make a very fine "pencil" of flameless heat, more than hot enough to melt solder, and it's very controllable. This thing does most of the work of $300-$1000 hot air blower SMD stations.
 
mramos1 said:
What temperature is the iron? Solder wick would scare me, all the heat on the junctions..

And my eye site would kill me anyway.
I do this quite often, though I worried about it at first I have never destroyed a chip, yet, and some of my earlier tries were rather messy. The soldering iron is usually set for 270degF or so.

I use reading glasses for soldering SMD stuff. I went to the local pharmacy and bought the highest magnification I could find. I like them far more than those giant magnifying glasses on arms.

**broken link removed**
 
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