Even the best soldering iron may not be able to solder at a fast pace. So what if the board itself is soldered?this is the goal Carl Bugejaand you can solder this PCB itself before soldering other boards!
Bugeja’s approach is illustrated using a pizza analogy. The PCB is the fabric, the solder paste is the source, and the topping is the circuitry. Throw all this in the oven and your —t—a—s—t—y—p—i—z—z—a— PCB is ready.
For those unfamiliar with surface mount electronics, a large stencil is placed on top of the prefabricated PCB. Next, a layer of solder paste (think toothpaste, not typical solder) is applied through the stencil. A pick-and-place machine is then used to drop the components into the solder paste, and the entire board is placed in his reflow oven, where the components are baked into place. If you need to create thousands of boards, this is the way to go.
Bugeja uses one of the PCB’s many layers as a means of heat transfer. Rather than one large copper ground plane, Bugeja reconfigured the layers into tracks that provide some resistance and heat the board. This heat reflows the solder paste and solders the components in place.
Bugeja deliberately kept the resistance low. This allowed the board to be self-soldered at 165 degrees Celsius (328 degrees Fahrenheit) using just 9 volts. The magic 165°C is the temperature needed to melt the low temperature solder paste (Chipquick TS391LT50 if you know). Bugeja has chosen a PCB construction that is good up to 170°C. This provided a robust medium for the board as it was a one shot and she was soldering for 5 minutes.
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The downside to this process is that it’s a one-time process, but Bugeja is prepared for this, making this layer a ground (GND) plane by soldering a zero ohm resistor from the track to the GND connection. use. An elegant solution, if we say so.
The circuit was designed using Altium Designer, and Bugeja used this to his advantage, routing wavy self-soldering tracks around the many vias that functioned between the layers of the circuit. Input of the soldering force is through his two extensions to the PCB. These extensions power around the track and are easy to remove when the job is done. Is there such a thing? It uses “mouse bite vias”, ie small nibbles built directly into the structure of the PCB. They can be easily broken and polished, leaving little or no trace of their existence.
The first test worked fine. It certainly wasn’t perfect. It had some soldering clumps and needed a bit of tinkering, but it didn’t damage the board. All I needed was a bootloader, some component modifications, and a custom Arduino sketch to control the next part. business.
Initially, Bugeja controlled the temperature manually by gradually increasing the voltage, but Bugeja felt that a computer would work better. Which technique allows another circuit to self-solder accurately using the exact temperature profile of the solder paste, and that is his PCB that Bugeja just self-soldered. Yes, on the newly created board he has an Atmel MEGA32U4 (often used in the Arduino world) and a temperature sensor (thermocouple). All the user has to do is connect a compatible board to her PCB, press a button, and the PID controller will cook her PCB exactly to order.
A second version of the board (Bugeja called it “daughter”) was attached to the original (mother) using two machine screws. Then I taped the thermocouple to the underside of the board. After pressing the button, the Arduino sketch started executing, controlling the temperature profile to 165°C and allowing the components to settle into their final positions. Daughter her board was a success and Bugeja celebrated by creating another board, the granddaughter of the original.
Bugeja’s project is an excellent approach to surface mount soldering and proves to be attracting the attention of many electronics professionals looking to push the boundaries of what is possible in the field. Currently, either buying expensive equipment to reflow surface mount builds, or MHP30 hot plate or go DIY yourself reflow oven toaster.
You can read more about Bugeja’s project and download the PCB file below. their GitHub repository.