1. The personality of solder paste? Viscosity, vibration, thixotropy, melting point is usually lead 183, lead-free 217, etc. 2. The welding process of solder paste components? It can be divided into four stages: temperature rise, constant temperature, reflow, cooling and temperature rise: the printed PCB with good patch is added to reflow soldering, and the temperature rises gradually from room temperature, with the temperature rise rate controlled at 1-3 ℃/S. Constant temperature: By protecting the quiet temperature, the solder flux in the solder paste exhibits efficiency and evaporates moderately. Reflow: At this point, the temperature rises to * high, the solder paste liquefies, and an alloy is generated between the PCB pad and the part solder end. The welding is completed, and the time is arranged in 60s, depending on the solder paste. Cooling: When cooling the welded plate, controlling the cooling speed well can achieve beautiful solder joints, such as ROHS 6-7 ℃/S. 3. How to optimize process parameters? Optimization of profile curves? It is generally necessary to go through three methods: preset, measurement, and arrangement to obtain optimal parameters. Taking the furnace temperature curve as an example, the travel speed and temperature of each temperature zone of reflow soldering soldering should be preset according to the type of solder paste, PCB thickness, etc., and then the furnace temperature tester should be used to measure the intrinsic temperature curve of the PCB board, and then understand with reference to the usual body odor and the conventional process of solder paste soldering, and repeatedly arrange and revise the preset temperature and travel speed, so as to obtain * consistent curve documents. 4. The efficiency of solder paste, process parameters, and mechanical equipment in printing solder paste? How to innovate? At the beginning, because of its identity ratio and particle size, the solder paste probably used the molding, thixotropy, vibration and other personality defects that were not typically displayed, resulting in the display of collapse, short circuit, lack of tin and other situations during printing. Process parameters such as printing pressure, scraper speed, scraper angle, etc. can cause defects such as insufficient tin content, pinching, irregular forming, or solder bonding after solder paste. Hardware is important in terms of scraper hardness, steel mesh relaxation force, hole size, tooth shape, surface roughness, steel mesh thickness, and the support and fixation of the printing machine on the PCB, which can lead to poor printing. In short, there are many factors that determine the essence of solder paste printing. In essential consumption, based on essential questions, we can understand the reasons for the formation of defects and reconcile them to the best. 5. Creation of Profile DOE? The creation of CPK for SMT machines? DOE: Test arrangement. A statistical method for arranging and understanding experimental data. The creation of Profile DOE can be completed in the following steps: 1. According to the company's reflow soldering homework guide book, select the target to try: such as the set walking speed, the set temperature of each temperature zone, etc. 2. Refer to the Understanding Test Center and determine the appropriate trial status on the board as the trial status. 3. The expected (based on the experience of body odor) deadline for the experimental status to be displayed (such as bridging, solder joints, etc.), and the list is waiting for statistics. 4. After the preparation is completed, several sets of experiments are repeated, statistical deadlines are calculated, deadlines are understood, and optimal parameters are determined.