![]() The increased static pressure increased the peak temperature by about 5☌ and TAL by about 10 sec. The oven was reset to the baseline parameters and the pressure varied from 0.7 to 1.3 IWC. Peak temperature and TAL increased with the higher zone temperature settings and the uniformity decreased ( Table 5). The oven was reset to the baseline parameters, and the temperatures in zones 6 and 7 were increased and decreased by 10☌. The increased belt speed lowered the peak temperature and TAL, and slightly decreased the temperature uniformity at the peak. Table 4 shows the peak temperature, TAL and uniformity data for each board. Belt speed was varied from 24 to 32 IPM with the static pressure and zone set points at the baseline settings. in the TAL between the two boards because of weight and board design.īelt speed. There was a difference of about 5☌ at the peak and 8 sec. Table 3 shows the peak temperature and TAL data for the boards. Figures 1 and 2 show the resultant profiles for the 100 and 230 g boards, respectively. The 100 and 230 g boards were run at the baseline operating parameters of 28 IPM, 1.0 IWC and zone 7 set points of 250☌. Data were gathered with a SlimKIC II profiler. High and low ranges were established for each of the variables, as outlined in Table 2. An additional run was performed with all variables at the high and low settings to see the combined effect. The plan was to individually vary each parameter (high and low) and record its effect on the TAL, peak temperature and uniformity of each board. A recipe that produced a Pb-free ramp-to-peak profile with a belt speed of 28 IPM and static pressure of 1.0 IWC was chosen as a baseline ( Table 1). ExperimentalĪ Pyramax 98 N reflow oven with edge rails, fine mesh belt, and closed loop pressure control was used for this experiment. Given the three possible adjustments, a study was undertaken to determine the effects varied belt speeds, static pressures and zone temperatures have on the peak temperature, time above liquidus (TAL) and temperature uniformity of a 100 and 230 g populated surface mount board. Some oven manufacturers have added high, medium and low fan speeds as an additional adjustment, and one manufacturer has a closed-loop pressure control. One is the zone set points and the other is belt speed. Thus, the importance of accurate recipes and precision oven control is amplified.Ĭonventional reflow ovens have two adjustments for profile development. Additional complications exist because the liquidus temperatures of the new solders require peak temperatures close to the point at which components are damaged. Solder paste manufacturers have developed profile parameters, but it remains the responsibility of the assembly engineer to find the correct control settings with a limited number of reflow oven adjustments. The change from eutectic to Pb-free solder has required new recipes for reflow ovens. Belt speed, zone temperatures and static pressure all impact peak temperature.
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