Step 1: Building the CubeSatSim STEM Payload SMT Part 1

These are the instructions for building the STEM Payload Board and Solar Board as full Surface Mount Device (SMD) Boards

Here's what the board looks like when finished:

STEM Payload PCB

These are the instructions for building the v1.3.2b STEM Payload board with SMT Components.

Here's the v1.3.2.1 PCB:

Schematic

Here's the schematic for the v1.3.2.1 STEM Payload board for reference:

https://github.com/alanbjohnston/CubeSatSim/blob/1879cfcc7c7107f493e8788ce71393240aeb0311/hardware/beta-v1.3.2/cubesatsim-STEM-b1.3.2.1_schematic.pdf

Assembly

The optional SMT component D11 is not mounted, so you don't need to apply solder paste to these pads. If you do, it doesn't really matter.

You will need these tools:

• Safety glasses (to protect eyes while soldering or trimming leads)
• Solder Rework Station (a fine tip soldering iron and a hot air wand)
• Fine solder
• Solder paste
• Reflow oven
• Flux pen
• Tweezers
• Needle nose pliers (to bend leads and hold parts)

Assembly

The best way to do SMT soldering is to use solder paste with a stencil and run the board through a reflow oven. The instructions here will cover this approach.

Stencil

Start with your SMT stencil setup. You will need three blank PCBs of the same thickness, a backing board, the metal stencil, and some tape to secure it all together:

The PCB should slide in securely but not be loose. When the stencil is laid on top, you should only see the PCB pads. Apply the solder paste to the stencil and spread.

Spread until all pads are evenly filled:

Open the stencil and remove the PCB:

Mounting Components

The components can be mounted in any order. Sometimes it is easier to attach the PCB to cardboard or a board so you don't have to touch the PCB to move it around.

Resistors do not have a polarity. Check resistor values before mounting and double check with a meter if you are unsure.

All capacitors except one do not have a polarity.

Some of the components have a polarity - those components will be shown here.

The polarity of diode D7 is indicated by a white line on the component:

Here's how it looks mounted on the PCB:

The polarity of diodes D5 and D6 is indicated by a white line on the component:

Here's how they look installed on the PCB:

The capacitor C7 has a polarity indicated by a bar on the component which is the plus side.

The PCB has a + labeled, so the plus side with bar should be down:

The SR_FRS FM Module U6 is difficult to handle since it is too large for tweezers. Also, try to align the pins with the pads. When mounted, it looks like:

Here is the complete board before going through the Reflow oven:

Here is the board after running through the reflow oven:

After the reflow oven, the board is ready to have the through hole components installed.

The next step is the STEM Payload PCB Through Hole Soldering in V2 STEM Payload SMT 2