These ICs are then placed on perfectly good PCBs. Removing Defective Parts - Sometimes, during the IC manufacturing process, errors can arise and go unnoticed. The part usually sticks strait up resembling a tombstone.Ĭold Joints - This is similar to a tombstone except the parts might not be sticking strait up, making it harder to see the connection that is not being made. Tombstone Parts - This is when a part (usually a resistor or capacitor) reflows only on one side. These include ICs, diodes, some capacitors, connectors, etc. Polarized Components - Parts that have been placed incorrectly (backwards, shifted x degrees off). Just think of it as doing any work to the board that wasn't involved in the actual production process. The term rework just means you are refinishing or repairing an already reflowed board, and it is a term commonly used in the electronics world. As mentioned above, they are a crucial tool when it comes to reworking a board. Hot-air rework stations can be very handy. The bigger nozzle is great if you are trying to focus hot air around a big area on the board. The smaller nozzle is good for focusing the hot air on smaller components. Nozzles - The 303D comes with 2x changeable hot-air nozzles. The indicator in the temperature box will twinkle when the desired temperature is reached. The LED output will display the setting temperature for 3 seconds and then return to the actual air temperature of the nozzle. You can adjust the working temperature by turning the temperature setting knob. Temperature Range - Output temperatures range from 100° ~ 480° Celsius. The LED output will display the setting air flow grade for 2 seconds and then return to the current air temperature of the nozzle. You can adjust the air flow by turning the air setting knob.

By default, the display will show your current temperature in degrees Celsius.Īir Flow Grade - Air flow grades range from A25 ~ A99. Many ovens can't warm up or cool down fast enough to exceed the maximum temperature rates specified on component profiles, so the feedback loop supplied by the thermocouple may only be telling the controller to turn on and then off anyway.Note: Temperature scale (Celsius vs Fahrenheit) is set during the manufacturing stage. I agree with other posters that the simple approach of turning on the oven, waiting for the last joint to reflow, and then opening the door is effective. Manufacturers often use multiple thermocouples while they're getting the process figured out. Try to monitor the hottest and coldest points. Typically, larger components will reflow last, as well as ones closer to the front glass of the oven where it is colder. If you want more assurance that the profile is correct, you should monitor several points with thermocouples that are attached with thermally conductive paste or epoxy. Although an airborne thermocouple won't be reading the exact temperature of a particular joint, it should still allow your controller to recreate a consistent profile on a run of boards. However, for hobbyist applications, you may not need the precision. So what is the best approach to monitor the temperature?Ĭomponent size, density, ground planes and placement in the oven will all greatly affect the temperature at a particular point, so putting a thermocouple on glass won't tell you much more than putting one in air. But it would still not be perfect for every board of varying sizes. I have thought about putting a small piece of glass inside my reflow oven and attaching a thermocouple to the glass and using that to monitor the temperature because glass has a specific heat capacity very similar to that of FR4. Everyone is trying so hard to follow a specific profile as close as possible but if your feedback temperature is bogus then your controller is useless, right? The temperature of the board and the solder is going to vary based on many factors, including board size, which change the heat capacity of the board.

The two profiles were very different, as expected. In my own reflow oven I soldered a thermocouple to a board and compared the board temp to a second thermocouple monitoring the air temperature. All of the DIY projects that I have read about, including the nice pre-made controller from sparkfun, utilize a simple thermocouple to monitor the air temperature. But you cannot monitor the temperature of easily unless you have an infra-red camera which is difficult to obtain on a budget. Unless I am mistaken, all of the recommended profiles that I have seen indicate the profile that the solder should undergo. I am having trouble understanding what is the best way to control the temperature. I have also seen many solder profiles as specified by the solder manufacturers, component manufacturers, and other self-proclaimed experts. I have read many website and forums about DIY reflow ovens for SMT soldering.

Solder reflow temperatures