Lead-free Reflow Profile: Soaking type vs.Reflow oven zone temperature set up and thermal profile Reflow Soldering in PCB Assembly Infra-Red (IR) Reflow Soldering is a SMT process in PCB assembly manufacturing, in which a solder paste is used to temporarily attach one or thousands of tiny SMD components to their contact pads on bare printed circuit board, after which the entire SMT assembly is subjected to controlled heat.Save optimized parameters as per the target board’s reflow specification.Adjust the parameter setup and test several times to find the upper limit and bottom line of the real-time reflow profile.Compare real-time thermal data with the virtual profile.Burn-in a test board with thermal shock and mechanical shock to check the board’s reliability.Check the solder joint quality, PCB and component status.Reflow the board and measure the real time thermal profile simultaneously.So, you must analyze your target board first before creating a unique reflow profile.Ī virtual reflow profile is based upon soldering theory, the recommended solder profile from the solder paste manufacturer, size, thickness, cooper weight, layers of the board and size, and the density of the components. Big components may need more time to heat up than small ones. It is also quite different when the components absorb the heat to warm up. When the temperature reaches that value the reflow process begins with a set temperature for a brief amount of time (about 180-200☌). First one is the preheat where the whole board rises towards a certain temperature (about 120-150☌). Benefits of PCB preheating Allows outgassing of volatile solvents. During the preheat and soaking phases, volatile solvents in the solder paste are burned off and the solder flux is activated. It would work just like a 3D-printers heated bed and the aim. There are 3 stages of this reflow soldering process. This is then followed by the reflow phase which initiates solder joint formation. The cooling slope rate should be about twice the preheat slope rate to avoid PCB parts bending and burrs on the solder joints. The PCB thermal capacity is different according to the material type, thickness, copper weight and even the shape of the board. This project by Carl Bugeja is an attempt for making a PCB Hot-Plate that reflows other PCBs. The reflow cooling stage is the step where the solder consolidates as the reflow oven zones' temperatures get down from the peak to 75C, and the components and PCB pads are well soldered. Does it mean that every spot in this GREEN area should fit your board reflow application? The answer is absolutely NO! The GREEN area is the acceptable range for the whole reflow process.
According to the recommendation by the IPC association, the generic Pb-free solder reflow profile is shown below.
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