Saturday, September 19, 2015

Making of Surface Mounted (SMD) DIY PCB TNC


In my learning process of making my own DIY PCB and after ordering some common SMD components ( capacitors, LEDs &, resistors ), I decided to design a small and functional TNC that only need 4 connections to handy and a few jumper wires to Arduino.

*** This is the first time I ever successfully made a DIY PCB.

Let's start with the design on EagleCAD ..

I designed this small 28x23mm board for fun and to learn on how to solder SMD parts on DIY PCB. I made everything on a single layer. The only drawback is the two red and green LEDs are at the bottom where the copper traces are located.

Generate gerber and do a 3D view of the board. This method is easier to spot any errors.

3D Gerber view

Printed out for UV transfer to UV PCB
This is the tracing paper before the UV treatment. Thanks to Uncle Chow, 9M2CF made me a nice photo frame to hold the UV sensitive PCB and tracing circuit in place.

PCB holder / cover

UV lightbox

UV lightbox UV LED turned on

UV lightbox and photoframe cover
After like 15mins ( long duration was due to the diffused and evenly distributed UV light ), I drop the PCB into sodium hydroxide 0.7%. This is removed whatever parts exposed to the UV light and leaving the green part for second steps.

Exposed copper after Sodium Hydroxide bath
 Once the Sodium Hydroxide bath was done, I wash it and dump into the second solution - Ferric Chloride to eat away all those exposed copper.

Ferric Chloride bath
After a few shakes and turns, all the copper were wash away leaving the green portion of the copper traces.

I use thinner to clean away the green stuff and leave you with a shiny copper traces. Not bad for a first timer doing SMD PCB.

Now for the drilling and soldering part. A tip from 9M2CF, always solder before drilling as the solder will guide the drill bit into the holes to be drilled.

Drilling holes
Soldering SMD resistors
With too much solder at the pads, those SMD 1206 resistors are uneven on top ... or I was using a really fat tip.

SMD SVTrackR TNC back

SMD SVTrackR TNC front
After a while, got all the SMD and through-hole parts soldered. Need to find the SMD parts for the 100K POT. This is the one I currently have in my part inventory.

Add caption

Comparing sizes between the old MicroModem with Mini Pro and the new SMD TNC that will run from either Arduino Mini Pro or Arduino Nano.


  1. Thanks for sharing such a descriptive blog. I learned so much from this blog.

    M83513 connectors

  2. Hi Stanely, My name is Dave (VE4NEG). I'm very interested in APRS. I would like to learn how to build a TNC from salvaged parts.
    Our ham radio club purchased a NET51TNC but didn't get the needed software. Would you happen to have a copy of the NET51TNC software?
    All the best
    73 Dave

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