Reflower Temperature Control System Design And Optimization

In Surface Mounted Technology(SMT) Production line of Electronic craftworks technology field, reflower is very a Important Equipment, Ultimately determines the quality of electronic products. In recent years, With the large number of electronic products to small, light weight, high density development, especially the use of handheld equipment, In the components of materials technology are the original SMT technology presents a major challenge, also make SMT got rapid development opportunities. Development of IC to 0.5mm,0.4mm.0.3mm pitch; the BGA has been widely used, CSP also cut a striking figure, and is also the trend of rapid rise. Cleaning free low residue solder paste, lead-free technology has been widely used by most enterprises are recognized and accepted. All of these have given the reflow process put forward new request, a general trend is to ask the reflower with more advanced, more precise control, to achieve energy saving, uniform temperature, suitable for double panel PCB and new devices encapsulation welding requirements, at the same time on the reflower process control ability to have higher requirements.First,major work1.Reflow machine control and optimization is one of the most important theoretical basis for reflow profile study.2.Design uses a five-zone reflow temperature profile of the theoretical division of the rules, study the rules of this division research has been the test of practice, to adapt to the majority of small and medium enterprises and laboratories, have broad market prospects; the same time improve the poor and down-zone temperature control theory, the difference between the upper and lower zone temperature control is conducive to a good double-sided PCB soldering.3.It was designed with high-power tungsten hot air convection heating and a combination of design, with eight heating-zone heating, hot air convection selected 16 of the same model fan through the Panasonic inverter to complete. 4.Control areas selected Siemens S7-200 CPU224XP controller, EM221. EM223 port, the temperature control module. RS485 bus and other equipment and devices to make the actual temperature curve temperature curve approximation to the theory;While flexible use of contactors, relays, thyristor control programs; through different frequencies to improve the fan temperature changes, to improve the flexibility and reliability of welding, to achieve temperature difference between the upper and lower temperature zone control.5. Appropriate choice of temperature measurement programs; for welding time from 2min-60min controlled, Panasonic A4 series servo motor controlled by frequency control technology accurately guide the chain speed; select the appropriate over-voltage current protection; insulation design; UPS configuration.6. Using PID algorithm, the minimum time control theory optimal reflow temperature.Second, innovation1.TheoryFive-zone reflow profile division of the theoretical study of the rules, the upper and lower zone reflow machine differential temperature control theory.2. Application PartReflower with thyristor control scheme.