Mounting passive SMT components

Just getting around to continuing assembly of NUE-PSK modem. Latest work included soldering SMT diodes (very small), electrolytic caps, and chip capacitors. These are all 2-lead packages. I found that the easiest way to mount all of these components was to do the following:

1.Put a drop of solder flux on each pad for the part

2. Put a very small amount of solder on one pad for the device

3. Position the board so you can see both of the pads for the device

4. Place the part, making sure both leads line up with the center of corresponding pads

5. Press down on the part, holding it in place and assuring contact between the leads and pads

6. Reheat the solder on the pad where solder was added (the part should now be holding to the one pad)

7. Add a very small amount of solder to the other pad

8. Press on the part and reheat the solder on the second pad

9. Return to the first pad and reheat briefly to make sure a good connection was achieved.

This sounds like alot of work but is really fairly easy. A good magnifying loop, small solder (.015″ or .020″ diameter), and a small soldering iron tip are indespensible for SMT work.

PSK Modem Assembly Update

Well I got most of the ICs onto the board. THe first three are fine-pitch (0.5 mm between pads). They were difficult to hand solder. The best approach seems to be the “drag solder” method, where you pull some excess solder across a whole row of pads, then use solder wick to remove any shorts.

The remainder of the assembly should be easy, it will just be a matter of finding the time. Building circuits is not the highest priority in the Summer time.

Surface Mount Assembly

I now have most of the parts for the NUE PSK modem, so it is time to setup for assembly. This uses SMT parts, so it will require some careful soldering. Instead of starting with the ICs (one-of-a-kind and many leads), I am trying the caps first. Starting witht the 1206 size caps, which are huge by SMT standards, should let me get going with minimal risk.

OK, I got about 10 done. My magnifying light is  piece of junk. It is hard to keep in one place. guess a $ 25 inspection lamp is not adaquate for SMT assembly. But I got the caps down. I had read that I might not need to add solder but that doesn;t work for me. I like to tack down one side, then go back and put some solder on bothe ends. Probably too much solder, but I don’t see how that can hurt anything,

Welcome

Today, March 23, 2008 I started this Blog. The main intention is to have a place to capture my activities in Ham Radio. My callsign is KG3V. I have been a Ham for many years, but just get “re-energized” in the past three years after a long inactive period.

So this will be my notebook for operaitng and experimenting. Hoepfully there is something useful for others as well. Feel free to leave coments – that is what this mode is all about.

Tom

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