Step 4
–
The Linear Regulator & Dual NPN Transistor
The Linear regulator (U2) and dual NPN transistor (Q1) are both SOT23 packages and are both
soldered in the same way. Tin 1 pad on the PCB footprint of each device, ideally one corner of the
package.
Hold the part in a pair of tweezers and position it in the correct orientation and alignment above its
PCB footprint. The Linear regulator (U2) is easy to orient as it has a missing pin on one side. The
Transistor (Q1) must be oriented by matching the pin 1 indicator on top of the package with the
marking on the PCB.
Use the soldering iron to stick the part to the tinned pad. Once the part is soldered in place, press on
the top of the package with the tweezers and then touch the soldering iron to the tinned pad a
second time. This will ensure that the part is flat and that all its legs are making contact with their
pads on the PCB.
Apply the soldering iron and a small amount of solder to each of the remaining pins one at a time.
Extra flux should not be needed for these parts as the solder has some flux in its core. If the part is
not soldering cleanly, extra flux may be applied to help the process.
