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.

One thought on “Mounting passive SMT components

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  1. Tom, I used the same sequence assembling a JUMA-RX1 DC receiver. The tricky parts were the discrete transistors with two leads on one side and one on the other, and the multi-lead chips. The transistors were hard because of the non-symmetrical side-to-side layout (2 versus 1 pin on a side) and needed more patience on my part to get them correctly positioned. The multi-lead chips basically went down like resistors and capacitors — tin everything and then zot one lead on one end. I then went to the opposite end and taked it down which put all the pins into correct alignment before soldering each of the individual pins.

    I still have the JUMA-TX1 companion transmitter to assemble but am waiting for time to try the solder paste and a portable convection oven my wife bought for doll-making projects. I’m told the paste is quite manageable and that, with an aluminum foil “roof” over the board to guard against the overhead coils coming on with too much infrared, that a simple toaster oven can actually be used. The paste is expensive, however, and I’m looking for someone to split the “minimum size” order with.

    73s

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