Reflow Overview

Before Reflowing

Always breadboard your circuit first to ensure proper functionality. Boards should be ready for completion because reflow is intended for creation of the final product. Exception is the use of hotplate reflow to attach a single IC onto a small board

Oven Reflow

The basic idea of oven reflow is to preset IC’s onto a PCB with solder paste and to heat the paste to its melting point, where the paste begins to “flow” which is why the heating processes containing solder paste is called reflow. During the reflow process, as the solder paste melts and transforms into the shiny solder we’re all familiar with, the surface tension of the molten solder helps center slightly mis-aligned IC’s or components. This makes the reflow process, sometimes, more forgiving than fine tip soldering. The rough steps for reflow using the Cuisinart Toaster Oven are listed below (for more detailed instructions refer to the Reflow Overview Powerpoint presentation available in the main page).

  1. Setting Components Click for image
    • Apply solder paste carefully, as how well this step is done, directly impacts the end result. Avoid excess use of solder paste, a very small amount will hold the IC in place and achieve an electrical connection. Set components onto solder paste after applying paste to PCB leads taking care to align pins properly. Click for image
  2. Oven Reflow
    • Preheating Click for image
      • Set oven to toast 4, press start on oven, and monitor temperature via the thermocouple meter.
      • Continue monitoring the thermocouple meter until the temperature reaches ~150-160 degrees Celsius.
      • Proceed to Drying phase.
    • Drying Click for image
      • Turn off the oven around 160 degrees for a 1 to 2 min duration, the temperature usually drops to around 150 during that time.
      • When the temperature drops to around 145 and about 1:30 has passed, proceed to the Heating phase.
    • Heating Click for image
      • Set the oven to "toast 6", press start.
      • Once the solder reflow can be confirmed visually or the thermocouple meter reads 200 degrees or higher, turn off the oven. Click for image
  3. Touch up Click for image
    • Merged pins and excess solder can be removed via de-solder braid.
    • Check all leads for errors such as shifted pins, and fix as necessary.

Your SMT circuit should be ready to go! Click for image