Introduction: Soldering Surface Mount Parts
The first thing you need to solder surface mount parts is confidence. It's not as hard as you think it will be. I need three different pair of glasses, one with bifocals, for my old eyes and I was able to get it right, on the second try.
I will be soldering a 555 timer to a Sparkfun eight pin SOIC breakout board.
You will need:
- Thin 60/40 solder wire .75mm or thinner
- Soldering Iron with a fine point tip
- Rubber mat so things don't slide around
- Magnifying glass
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Step 1: Position the Chip
Carefully position the chip on the solder pads on the board.
The notch and dot on the board indicate pin one.
Pin one on the chip is top left in the picture.
The line across the top of the chip indicates pin one.
Step 2: Soldering
Place the tip of the iron on the pad just next to the lead but not touching it.
Hold the iron vertical.
Apply a very little bit of solder and let it flow to make good contact.
Be careful but try to be quick about it. My first attempt was a fail. Everything looked good under a magnifying glass but the chip did not work. I probably took to long and got it too hot.
The breakout board has places for four chips and it is scored to make it easy to break it into four separate pieces.
Break up the board to remove your soldered part.
Cut two pieces with four pins each off of the strip of male headers and solder them. The square pad on the board indicates pin one.
Step 3: Testing
A not gate is the simplest 555 circuit I know of, so let's build one to see if the chip works.
You will need:
- The soldered 555 you just made
- 10 K pot
- Red LED
- Green LED
- 2 - 330-560 Ohm resistors
- 5-9 Volt power supply or battery
Build the circuit as shown in the photo and diagram.
When you turn the pot toward the ground side the input voltage will be low and the red LED should light.
When you turn the pot toward the positive side the input voltage will be high and the green LED should light.
The middle third of the travel is dead space, called hysteresis, this is what we expected to find.