Aug 03 , 2020
How to fix the SMD parts in the proper position when soldering? This is a predicament that everyone will encounter. So am I. Whenever I have PCB's that need to be filled with SMD parts I have to double check this, and as the pin spacing gets tighter this has become an issue.
Modifying some bent tweezers with rubber bands to improve grip is able to help hold the components in place until 1 or 2 pins can be soldered. This method works, but it can be very tricky. We can also try a variety of glues and place a small drop of glue in the center of the assembly placement. Sometimes this means works, but all the glues I've tried have make me either waste my time waiting for it to dry, or grabing more glue when it dried out (peeled) too quickly. To make matters worse, even a small drop of glue often spreads all over the mat board and then I have to waste even more time cleaning things up.
However, on the advice of a friend, I finally found a better way to make it! The method is as follows.
Step 1.Use a small piece of duct tape or painter's tape on one side of the part to press it down.
Step 2.To fix a few leads with solder.
Step 3.Remove the tape and solder properly
Step 4.For smaller parts (e.g. SOT23)...
Tin pads (usually intermediate pads).
Use the tweeter to secure the part in the correct position.
Use a soldering iron to quickly touch the leads on the tinned pads to secure them.
Solder the other pins correctly and then return to the fixed pins.
A nice feature of this technique is that you can rotate the part precisely by moving your elbow (your arm is like a big leaver). Even if you're a little wobbly, you can wait until the part is exactly aligned and then lock it in place with the big pin.