BTU Pmax 125N 设备介绍 中文-0511 - 第34页
Pe a k T e m pe ra ture v e rs us Sta tic Pre ss ure C o n v e y o r Sp e e d = 4 5 I PM - T e m p e ra ture Co n s tan t 180 190 200 210 220 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 Ti m e i n S e c onds Te m pe r a tu…
Static Pressure – 数字静压
What is Static Pressure?
Ø Static pressure is developed within the blower plenum to produce true forced
convection
• 什么是静压?
– 静压是通过风扇加压在加热器内部产生一个大于整个炉堂的压力. 通过压力差将加热后的气体均匀吹到产
品上，因此产生真正的 均匀热风对流。
Why is Static Pressure important?
Ø Static pressure directly relates to the amount of heat transfer an oven can
deliver
Ø Greater the static pressure, greater the heat transferred to the product
Ø Static pressure ensures uniform convection from the plenum to the product
为什么静压重要?
– 静压关系到炉子的加热性能
– 较高的静压使更多的热量传递到产品
– 静压能确保比较一致的对流气体从孔板传递到产品
Peak Temperature versus Static Pressure
Conveyor Speed = 45 IPM - Temperature Constant
180
190
200
210
220
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57
Time in Seconds
Temperature Deg. C
S. P. = 1.5 IWC
S. P. = 1.1 IWC
S.P. = 0.8 IWC
LOW <0.8 IWC
数字静压对峰温与熔锡时间的影响
不同静压下对器件的影响
0.5 IWC 0.8 IWC 1.2 IWC 1.5 IWC
Tantalum Cap 209.1 212.1 213.6 215.7
Large QFP 199.2 203.5 206.7 209
Chip Resistor 209.9 213.6 215.2 216.8
SOIC 209.7 212.6 214.8 216.2
TC Mean 207 210.5 212.6 214.4
TC SD 5.2 4.7 4 3.6
Delta T 10.7 10.1 8.4 7.8
Convection Rate Measured in In/H2O
Low High
Effects of Low Convection Rate
qLower Peak Temp
qLarger Peak Delta T
qThermal Uniformity Deteriorates
Effects of Increasing Convection Rate
qGreater Peak Temp
qSmaller Peak Delta T
qThermal Uniformity Improves
40 HZ 50 HZ 60HZ 70HZ
Peak Temp