A. permit the passage of vapor but not of flame B. prevents the passage of flammable vapors C. prevents inert gas from leaving a tank D. permits vapors to exit but not enter a tank
A. 等于1 B. ＞1 C. ＜1 D. 等于0
A. 印刷线路板涂助焊剂→贴放元器件→低温固化→浸焊 B. 印刷线路板涂锡膏→贴放元器件→低温固化→溶焊 C. 印刷线路板涂锡膏→贴放元器件→低温固化→波峰焊 D. 印刷线路板涂锡膏→低温固化→贴放元器件→溶焊
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