reveal the PCB with solder paste accurately placed at a
uniform thickness (Figure 14). Figure 15 shows this even
distribution of solder paste.
The next step is to put any excess solder paste back
into the original container and to clean up any residual
paste. Be careful not to put any contaminating material
into the solder paste as it could affect the spreadabilty in
subsequent applications. I used a paper towel and some
isopropyl alcohol to clean the stencil and the spatula. I
noticed that Beta now sells a wet wipe product for this
Now for the fun part: placing the surface-mount
components on the board. I used the included tweezers
and a finer tipped pair of tweezers I already had to
remove the SMD parts from their paper tape and plastic
carriers, and place them carefully on the PCB. Orientation
of polarized parts such as LEDs, diodes, and capacitors is
important. The solder paste is sticky enough to hold the
components in place. You just have to be careful not to
bump any components while reaching towards the center
of the board to place some other part. Figure 16 shows
the components placed on the solder paste.
Once all the parts are placed, it’s time to put the
board in the oven and power up the controller. I attached
the thermal sensor to the test PCB for the first run;
thereafter, I attached it to a similar sized PCB (also placed
in the oven) so that it senses the same temperature as the
kit PCB. I chose to use high temperature polyamide tape
to affix the thermal sensor to the board (ee Figure 17).
I did find that the tape was less sticky after a few cycles,
so I also used a piece of wire inserted though the PCB to
hold it in place on later runs.
With the thermal sensor attached and the kit PCB
placed in the oven, I closed the oven door, powered up
the controller, and started the cycle (Figure 18). The first
thing I noticed was a couple of yellow LEDs at the bottom
of the controller. Yellow and red LEDs make me a bit
nervous, but these were only showing the status of the
USB connection to the controller (Figure 19). A USB
connection is not needed to use the controller, but it is
provided to allow firmware updates, etc.
Temperature calibration, temperature units (degrees
Celsius or Fahrenheit), backlight brightness, and many
Figure 12. Solder paste applied to mask, but not yet spread out.
Figure 16. SMD components placed on PCB pads with solder paste.
Figure 13. Solder paste spread across the stencil.
Figure 14. Solder stencil flipped up after paste application.
50 January 2015
Figure 17. Board placed in oven with thermal sensor attached.
Figure 15. Solder paste applied to the pads on the board.