Making Our Own PCB – Soldering On the Parts

Our Boulder, CO members went back to Solid State Depot the following week to learn how to solder stuff on our newly etched copper board.  If you remember from the previous post on Making Our Own PCB – Etching Copper Clad Boards, we ended up with a copper clad board, etched out with a circuit design (including a shout out!)

Ready for soldering!
Ready for soldering!

The next workshop focused on actually soldering on the resistors and LEDs to prepare the board for programming.  Let’s first show the circuit design from the white board.

Where the parts are supposed to go
Where the parts are supposed to go

For us to be able to use the board, we needed to remove the border.  Before soldering on any parts, we had to use a bandsaw to remove the excess, all while keeping the usb end the correct size to go into a usb port (for programming the board later).

Using a bandsaw made it easy to cut the board to the right size.
Using a bandsaw made it easy to cut the board to the right size.

In order to put the parts on the board, we first had to put down soldering paste.  This made it much easier than soldering each individual part, as using the soldering iron would have been extremely difficult, if not impossible, for the very small positions on the board.  In order to make the application of the paste easier, we used a stencil over the board and spread the paste on.

Spreading paste with the stencil made it easier for the small board.
Spreading paste with the stencil made it easier for the small board.

With the paste on, we then put the resistors on the board, and the LED, according to the whiteboard diagram (make sure you put the notch of the LED in the right place).  This was actually pretty difficult.  A magnifying glass is best for making sure you put the resistors over the right place and it’s important to not press them down.  You have to keep the paste from touching the ground plane.

The paste is dark grey before being heated.
The paste is dark grey before being heated.

With all of the parts in place, now we’ll bake!  Using a convection oven works great and you want to bake it at 400° F until the dark grey paste turns shiny silver.  Some of ours didn’t turn, but it was easy to fix with a third hand and soldering iron.  Just hold the iron on the spots that were still dark grey until they change.

If all of the paste doesn't turn silver, its a quick fix with the soldering iron.
If all of the paste doesn’t turn silver, its a quick fix with the soldering iron.

Now for the test!  We used a 5V power supply on the resistors leading to the LED to ensure that the different color lights all worked.

And we have light!
And we have light!

Our final board is ready for programming, which is the next workshop.  The microcontroller will be needed for the next step.  Our next post will detail what we did to program the board.

Our soldered board, ready for the microcontroller.
Our soldered board, ready for the microcontroller.

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