🔥 Custom PCB Reflow Oven

Hack a toaster oven to solder SMD components using precise thermal profiles.

📋 Overview

Soldering tiny Surface Mount Devices (SMD) by hand is tedious. A reflow oven bakes the whole board following a strict temperature curve (Preheat -> Soak -> Reflow -> Cool) to melt solder paste perfectly.

What you'll learn: High-temperature K-Type thermocouples, Solid State Relays (SSR) for AC mains, and industrial PID temperature control.

Estimated time: 6-8 hours. Difficulty: ⭐⭐⭐⭐⭐ Expert.

🧩 Components Needed

Component	Specification	Qty	Notes
Toaster Oven	1500W+	1	Quartz heating elements preferred
Arduino Nano	5V	1
MAX6675 Thermocouple	K-Type	1	Reads up to 1024°C
Solid State Relay (SSR)	40A AC	1	Switches the oven heating element
LCD Display	16x2 I2C	1	To view temperature curve

📖 Step-by-Step Tutorial

Safety First

You will be modifying AC mains wiring inside a metal chassis. Ensure the oven is unplugged. Properly ground the chassis. Use thick gauge wires.

Thermocouple Placement

Drill a small hole and mount the tip of the K-Type thermocouple hovering exactly where the PCB will sit on the tray.

SSR Wiring

Cut the hot wire going to the oven heating elements and route it through the high-voltage side of the SSR. Connect the SSR control pins to the Arduino.

PID Profile

Program the Arduino to follow the standard lead-free reflow profile: Ramp up 1-3°C/sec, Soak at 150°C, peak at 240°C for 30s, then cool down.

💡

Mechanical relays cannot switch fast enough and will burn out quickly. You MUST use a Solid State Relay (SSR) attached to a large aluminum heat sink.

💻 Code / Configuration

reflow_oven.ino

INO

// Reflow Oven Profile (Conceptual snippet)
#include "max6675.h"

int thermoDO = 4;
int thermoCS = 5;
int thermoCLK = 6;
MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);

const int ssrPin = 9;

// Simplified state machine
enum State { PREHEAT, SOAK, REFLOW, COOL };
State currentState = PREHEAT;

void loop() {
  double currentTemp = thermocouple.readCelsius();
  
  switch(currentState) {
    case PREHEAT:
      if (currentTemp < 150) turnHeaterOn();
      else currentState = SOAK;
      break;
      
    case SOAK:
      // Keep around 150C for 90 seconds (use millis timer)

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