MTD1N60E TYPICAL SOLDER HEATING PROFILE For any given circuit board, there will be a group of control line on the graph shows the actual temperature that might be settings that will give the desired heat pattern. The operator experienced on the surface of a test board at or near a central must set temperatures for several heating zones, and a figure solder joint. The two profiles are based on a high density and for belt speed. Taken together, these control settings make up a low density board. The Vitronics SMD310 convection/in- a heating “profile” for that particular circuit board. On frared reflow soldering system was used to generate this machines controlled by a computer, the computer remembers profile. The type of solder used was 62/36/2 Tin Lead Silver these profiles from one operating session to the next. Figure with a melting point between 177 −189°C. When this type of 17 shows a typical heating profile for use when soldering a furnace is used for solder reflow work, the circuit boards and surface mount device to a printed circuit board. This profile will solder joints tend to heat first. The components on the board vary among soldering systems but it is a good starting point. are then heated by conduction. The circuit board, because it Factors that can affect the profile include the type of soldering has a large surface area, absorbs the thermal energy more system in use, density and types of components on the board, efficiently, then distributes this energy to the components. type of solder used, and the type of board or substrate material Because of this effect, the main body of a component may be being used. This profile shows temperature versus time. The up to 30 degrees cooler than the adjacent solder joints. STEP 1 STEP 2 STEP 3 STEP 4 STEP 5 STEP 6 STEP 7 PREHEAT VENT HEATING HEATING HEATING VENT COOLING ZONE 1 SOAK" ZONES 2 & 5 ZONES 3 & 6 ZONES 4 & 7 RAMP" RAMP" SOAK" SPIKE" 205° TO 219°C 200°C PEAK AT DESIRED CURVE FOR HIGH 170°C SOLDER JOINT MASS ASSEMBLIES 160°C 150°C 150°C SOLDER IS LIQUID FOR 40 TO 80 SECONDS 100°C 140°C (DEPENDING ON 100°C MASS OF ASSEMBLY) DESIRED CURVE FOR LOW MASS ASSEMBLIES 50°C TIME (3 TO 7 MINUTES TOTAL) TMAX Figure 17.Typical Solder Heating Profile Motorola TMOS Power MOSFET Transistor Device Data 9
