DIY Reflow Hot Plate

I often work on electronics projects that involve SMD soldering, and while a soldering iron works for basic tasks, it becomes tricky and time-consuming when dealing with many small surface-mount components. I started looking for an SMD reflow hot plate, but most of the available options were quite expensive for a hobbyist budget. Instead of buying one, I decided to build my own DIY reflow hot plate. This way, I could customize it to my needs, learn more about the process, and save money while still achieving professional-quality soldering results for my projects.

I built a DIY Reflow Hot Plate using a PTC (Positive Temperature Coefficient) heating plate and an Arduino Nano. This compact and affordable setup makes it easy to solder SMD components at home without specialized equipment.

Unlike traditional soldering irons, which can be tricky for small surface-mount devices, a reflow hot plate evenly heats the entire PCB, allowing solder paste to melt and components to be soldered all at once. By integrating an Arduino Nano, I was able to control the heating profile, monitor the temperature, and ensure a safe and reliable soldering process.

This project is perfect for electronics enthusiasts, students, and DIY makers who want to explore surface-mount soldering on a budget. With just a few common parts, you can build your own hot plate reflow station and take your electronics prototyping to the next level!

You just need to buy the components and follow the steps below. But before making your hand dirty, please enjoy the demo video of my reflow hot plate.

The following hardware components are required for making the reflow soldering plate:

1. Arduino Nano (Aliexpress)
2. 1.3 Inch OLED Display (Aliexpress)
3. Hi-Link 220V AC to 5V DC Module (Aliexpress)
4. Solid State Relay (Aliexpress)
5. MAX6675 Thermocouple Module (Aliexpress)
6. PTC Heater Plate 220V, 300W (Aliexpress)
7. PCB Copper Board (single layer) (Aliexpress)
8. Resistors (100 ohm and 4.7K) (Aliexpress)
9. Tactile Button Switch (12x12) (Aliexpress)
10. M3 Screw and Nuts (Aliexpress)
11. Fiber Board

The following Tools are required:

1. Soldering Iron (Aliexpress)
2. Soldering Lead (Aliexpress)
3. Wirecutter (Aliexpress)
4. Screwdriver Set (Aliexpress)
5. Wires
6. 3D Printer (optional)

[Note: Some of the links in the parts list are affiliate links. If you choose to buy through them, it won’t cost you anything extra, but it helps support my projects. Thanks for your support!]

Reflow soldering is the process of melting solder paste to permanently attach electronic components to a printed circuit board (PCB). In professional environments, this is done inside large reflow ovens that precisely control heating stages. But for hobbyists and makers, those ovens are often too expensive and impractical. That’s where a DIY reflow hot plate comes in.

🔥 Why a PTC Hot Plate?

A PTC (Positive Temperature Coefficient) heating element is ideal for this project because it is self-regulating. Unlike traditional heating elements that keep getting hotter as long as power is applied, a PTC heater naturally limits its maximum temperature. Once it reaches a certain threshold, its electrical resistance increases, reducing the current and preventing overheating. This makes it safer and simpler to use in a home-built hot plate reflow system.

⚡ Power Supply with Hi-Link Module

To keep the project compact and safe, I used a Hi-Link 220V AC to 5V DC converter module. This small but powerful module takes in mains AC voltage (220V) and outputs a stable 5V DC supply to power the Arduino Nano, OLED display, MAX6675 sensor module, and other low-voltage components. By integrating it directly on the PCB, the entire project can be powered from a single AC input without needing an external adapter. Since the Hi-Link is an isolated converter, it also adds an extra layer of safety when working with mains voltage.

🧠 The Role of the Arduino Nano

The Arduino Nano acts as the brain of the system. It continuously reads the temperature of the hot plate using the MAX6675 thermocouple module. Based on this feedback, the Arduino decides whether to turn the heating element ON or OFF using a solid state relay (SSR) or MOSFET driver.

This creates a closed-loop control system:

1. Arduino measures the hot plate temperature.
2. If the plate is cooler than the target, Arduino switches the heater ON.
3. If the plate is hotter than the target, Arduino switches the heater OFF.
4. This cycle repeats rapidly to maintain the correct heating profile.

For more accuracy, a PID (Proportional-Integral-Derivative) control algorithm can be used instead of simple ON/OFF switching. PID helps stabilize the temperature and follow the reflow soldering curve more closely.

🌡️ The Reflow Profile

Reflow soldering isn’t just about heating up and melting solder—it requires a specific temperature profile to avoid damaging components. The typical stages are:

1. Preheat – Gradually warm up the board to prevent thermal shock.
2. Soak – Hold at a moderate temperature to activate flux in the solder paste.
3. Reflow (Peak) – Rapidly heat to the solder’s melting point, allowing it to flow and form strong joints.
4. Cooling – Controlled cooldown to solidify the solder and prevent cracks.

By programming these stages into the Arduino, the hot plate can follow a proper reflow curve. Even if the system is simpler than an industrial reflow oven, it’s good enough for prototyping and small-scale projects.

🖥️ Extra Features (Optional)

1. OLED display → shows real-time temperature and status.
2. Buttons → allow the user to start/stop the process or select profiles.
3. Buzzer/LED → provides feedback when the reflow cycle is complete.

⚡ In short: the Hi-Link module powers the control electronics, the PTC hot plate provides the heat, and the Arduino Nano + MAX6675 sensor provide the brains. Together, they make professional-style SMD soldering possible right on your workbench.

⚠️ Safety Note: Working with 220V AC

This project involves direct connection to 220V AC mains, which can be extremely dangerous if not handled properly. Please keep the following in mind:

1. Always double-check wiring before powering the system.
2. Use proper insulation and enclosures to cover exposed AC connections.
3. Never touch the PCB, hot plate, or wiring while it is connected to mains power.
4. If possible, use a fuse or circuit breaker for added protection.
5. Only attempt this project if you are familiar with working safely around AC mains.
6. Keep the project away from flammable materials and ensure good ventilation.

The Hi-Link AC to DC converter provides electrical isolation for the 5V control circuit, making it safer to power the Arduino and other low-voltage parts. However, the AC input pins of the module are still connected to mains and must be handled with extreme caution.

To make the reflow hot plate more compact and robust, I decided to build a custom PCB for the project. Instead of using messy jumper wires on a breadboard, the custom PCB neatly integrates the Arduino Nano, MAX6675 module, Hi-link AC to DC Power Module, OLED display, buttons, and control connections to the solid-state relay.

I designed the schematic and PCB layout using EasyEDA, a beginner-friendly online PCB design tool. It allowed me to arrange components, define traces, and check for errors before finalizing the design. Once satisfied with the layout, I exported the PCB artwork for fabrication.

Since I wanted to build it at home quickly, I used the toner transfer method for PCB making:

1. Print the PCB design on glossy paper using a laser printer.
2. Place the printout face-down on a copper-clad board.
3. Apply heat (using a household iron or laminator) to transfer the toner onto the copper.
4. Etch the board in ferric chloride (or another etchant) to remove excess copper.
5. Drill component holes and clean the board.

The final result was a clean, reliable, and professional-looking PCB that made the project easier to assemble, more durable, and less prone to wiring errors.

👉 Tip: If you don’t want to make PCBs at home, you can also send the Gerber files from EasyEDA to a PCB manufacturer for professional fabrication.

After etching the PCB using the toner transfer method, the next step was to drill holes for the through-hole components. Since most of the components like the Arduino Nano, OLED header pins, buttons, resistors, buzzer, and terminal connectors require holes, this step is essential for proper assembly.

🛠️ Tools Used

1. Mini hand drill or PCB drill machine
2. Small drill bits (typically 0.8 mm – 1.0 mm for resistors, headers, and IC modules, and 2.0 mm – 3.0 mm for screw terminals and power modules)
3. Safety glasses and proper lighting for accuracy

📍 Drilling Process

1. Secure the PCB on a flat surface with clamps or tape.
2. Use a center punch or sharp pin to lightly mark the drill points—this prevents the drill bit from slipping.
3. Start drilling with a small drill bit for the fine holes (resistors, IC headers, switches).
4. Switch to larger drill bits for terminal connectors, mounting holes, and the Hi-Link module.
5. After drilling, gently clean the board to remove any copper dust and burrs.

✅ Result

With all the holes drilled, the PCB is now ready for component placement and soldering. Proper drilling ensures that components fit perfectly into their pads, making soldering easier and the final board more reliable.

With the PCB ready, it was time to assemble and solder the components. To make assembly easier and avoid mistakes, I followed this order, starting with the smaller components and moving to the larger ones:

🛠️ Sub-Steps for Assembly:

1. Start with the smallest components
2. Solder the resistors first. They are flat and easier to place when the board is empty.
3. Add signal and user interface components
4. Solder the two tactile switches for user control.
5. Place and solder the buzzer, which provides audio feedback.
6. Mount the display
7. Position the OLED display (0.96" SSD1306 I²C).
8. Ensure the pins match the correct footprint on the PCB before soldering.
9. Install the main controller
10. Place the Arduino Nano on its footprint or pin headers.
11. This will serve as the brain of the project.
12. Attach the sensor module
13. Solder the MAX6675 module to the PCB.
14. Make sure the thermocouple connector faces outward for easy access.
15. Add the power module
16. Mount the Hi-Link 220V to 5V power supply module.
17. Be careful while soldering this part since it handles mains voltage.
18. Secure external connections
19. Install the terminal screw connectors for the hot plate, relay, and power input.
20. These provide strong and safe wiring connections.
21. Final check
22. Inspect all solder joints.
23. Look for bridges or cold joints.
24. Verify correct orientation of components (especially Nano, OLED, Hi-Link).

By following this order, the assembly process stays organized, and each component has enough clearance while soldering. The finished PCB makes the project much more durable and professional compared to a breadboard-based prototype.

After soldering everything in place, I double-checked the connections to ensure there were no shorts or cold joints. The finished PCB not only made the wiring neat and organized but also gave the project a more professional look and improved long-term reliability.

In this step, I included some more pictures of my complete PCB assembly and the back side of the soldered PCB. Here are some quick tips for PCB assembly and Soldering if you are new to this:

Start Small → Go Big

1. Solder the smallest, flattest components first (resistors, diodes), then move on to larger ones (IC sockets, headers, capacitors, connectors). This keeps components from getting in the way.

Use Proper Soldering Technique

1. Heat the pad and the lead together for 1–2 seconds, then feed solder into the joint—not directly onto the iron tip.
2. A good joint looks shiny and cone-shaped, not dull or blobby.

Check Component Orientation

1. Double-check polarized parts (diodes, electrolytic capacitors, modules, Arduino Nano, Hi-Link power module) before soldering. Desoldering is harder than checking twice!

Trim Leads After Soldering

1. Cut excess component leads close to the solder joint with side cutters to avoid shorts and keep the board neat.

Avoid Cold Joints

1. If solder doesn’t flow well, reheat the pad and apply a bit more solder. Cold joints often look grainy or cracked.

Keep the Tip Clean

1. Wipe the iron tip on a damp sponge or brass wool regularly and apply a bit of solder (tinning) to keep it shiny.

Secure the Board

1. Use a PCB holder, helping hands, or even tape to hold the board steady while soldering.

Inspect Your Work

1. After assembly, use a magnifying glass or loupe to check for solder bridges, missed pads, or cold joints.

Test Before Full Assembly

1. If possible, test critical connections (power rails, ground, signal lines) with a multimeter before plugging in sensitive components.

To give the project a sturdy and professional finish, I mounted the PCB, the PTC hot plate, and the solid-state relay onto a wooden (or acrylic/metal) base board. First, I marked the hole positions on the board by aligning the PCB and hot plate, then transferred the mounting hole locations using a pencil. With the help of a drill press, I carefully drilled holes that matched the mounting points of each component. Finally, I used M3 nuts, bolts, and screws to securely fasten the PCB, hot plate, and relay to the base board. This not only keeps the setup organized but also ensures that the components stay firmly in place during operation, reducing vibration and the risk of loose connections.

With the hot plate, solid state relay, and PCB securely mounted to the base board, the next task was wiring them together. I connected the hot plate’s AC wires to the high-voltage side of the solid state relay, ensuring the terminals were tightened firmly. Then I wired the relay’s control input to the designated pins on the PCB so the Arduino Nano could switch the hot plate on and off automatically. The thermocouple wires were connected to the MAX6675 module, which in turn feeds accurate temperature data to the Arduino.

Once all the wiring was completed, I carefully routed the cables to avoid tangling or crossing over critical components. To keep the assembly neat and safe, I used zip ties for cable management, bundling the wires together and securing them to the base board. This not only improved the overall look but also reduced the risk of accidental pulls or shorts during operation.

Since the PTC hot plate operates directly from a 220V AC supply, I needed a safe and practical way to power the system. Instead of soldering or using long wires, I added a 3-pin AC socket, similar to the ones used in laptop power adapters. This socket was connected to the PCB’s screw terminals with short insulated wires, ensuring a clean and reliable connection.

Working with high voltage can be dangerous, so I also designed and 3D printed a protective case to cover the AC socket and wiring. This enclosure prevents accidental touches and reduces the risk of electric shock while keeping the assembly neat and secure. With the socket firmly mounted and the case in place, the board can be powered safely by simply plugging in a standard AC power cord.

I designed 3D case using Tinkercad and printed it with my Creality printer. The case was modeled with two M3-sized mounting holes, allowing it to be securely attached to the baseboard. After printing the case, I placed the AC socket inside and fixed it firmly into position.

Next, I aligned the case on the base board, just beside the solid state relay, and secured it using M3 screws and nuts. This placement keeps the high-voltage input isolated from the low-voltage control circuit, while still making the socket easily accessible for plugging in the power cord. The result is a much safer and more professional-looking setup, with the AC input properly enclosed and firmly fixed to the baseboard.

Covering the High Voltage Side of the Solid State Relay

The solid state relay (SSR) I used has two sides: one for the low-voltage control and one for the high-voltage AC input/output. On the high-voltage side, the screw terminals remain exposed, which can be very risky since accidental contact could lead to electric shock.

To eliminate this hazard, I designed a small protective case that fits over the high-voltage terminals of the SSR. The case works like a mask, covering the screws while still leaving enough room for the wires to connect properly. Once printed, I mounted the case securely in place, ensuring that no bare metal parts were accessible from the outside.

This simple but essential addition not only improves safety but also gives the entire assembly a more finished and reliable look. With the high-voltage terminals covered, I can operate the system confidently without the risk of accidental contact.

Both of the 3D files were designed in Tinkercad and attached in the previous step.

To bring the reflow hot plate to life, I developed an Arduino program that follows the standard reflow soldering profile, which includes the preheat stage, soaking stage, reflow stage, and cooling stage. Each stage is carefully timed and temperature-controlled to ensure reliable solder joints, even for fine-pitch SMD components. For displaying real-time temperature and process information, I used the Adafruit_GFX and Adafruit_SH1106 libraries to drive the OLED display. The MAX6675 library was used to read accurate temperature data from the K-type thermocouple. To maintain precise heating throughout the process, I implemented a PID controller, which adjusts the hot plate’s power output smoothly and avoids overshooting. With this setup, the hot plate can automatically follow a consistent reflow curve, making SMD soldering both safer and more efficient.

Understanding the Reflow Stages

Before diving into the code, it’s useful to understand the different stages of a reflow soldering profile and why they are important:

1. Preheat Stage
2. In this stage, the temperature of the PCB and components is gradually increased. This helps to reduce thermal shock and gently warms the solder paste, preparing it for the next stage.
3. Soaking Stage
4. Here, the temperature is held in a steady range for a period of time. This allows the solder paste flux to activate, removes oxides, and ensures the entire PCB reaches an even temperature before reflow begins.
5. Reflow Stage
6. The temperature is quickly raised above the melting point of the solder paste. This is when the solder liquefies and forms strong joints between the SMD pads and component leads. This is the most critical part of the profile.
7. Cooling Stage
8. After reflow, the temperature must drop at a controlled rate. Proper cooling helps the solder solidify correctly, preventing weak joints or thermal stress on sensitive components.

By following these stages automatically, the Arduino code ensures a reliable and repeatable soldering process, similar to what professional reflow ovens achieve.

The following code has been developed and uploaded to my project:

You can copy the code above or download the code file attached below directly.

With all the wiring, coding, and assembly completed, it was time to test the reflow hot plate in action. After uploading the final Arduino code, I powered up the system and verified that each stage of the reflow profile (preheat, soak, reflow, and cooling) was working as expected. The OLED display clearly showed the live temperature and process status, while the solid-state relay smoothly controlled the hot plate through the PID algorithm.

I also took some photos of the finished build—both when powered off and when running. These give a clear view of the final wiring, placement of components, and the hot plate in operation. It was exciting to see the project come together into a working tool that I can now use for my SMD soldering work.

This DIY reflow hot plate not only saved me the cost of a commercial unit but also gave me the satisfaction of building a fully functional tool with my own hands. I hope this guide inspires you to try making one yourself!

Conclusion

That wraps up my DIY reflow hot plate project! I really enjoyed making this tool, and it has already proven to be very useful for my SMD soldering work. If you found this project helpful or inspiring, feel free to leave a comment, share your thoughts, or ask any questions—I’ll be happy to help. And if you build your own version, I’d love to see how it turns out!