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Occasional Rugged cooling rate curve is a sign of poor contact of cup. Test results should be discarded because FC number is way too low. Pour another cup right away.

上: 電路板老化或故障時, 抓取溫度不穩定, 速率曲線歪七扭八,每一次測都一樣,  但共晶溫度(TE)位置正常.  Above: Reoccuring rugged cooling rate curve with normal TE  is a sign of faulty boards. Below: Occasional rugged rate curve and abrupt drop of TE is caused by poor contact of cup to connector. 下: 杯子接觸不良, 速率曲線也是歪七扭八, 但偶爾才發生一次, 發生時整條曲線會"下沉"20~30 C.   Si 突然因而大增. 

Below: Previous cooling curve is normal and gives a result of FC 280, Si% of 1.64.  This abrupt drop of FC is a faulty test result that can be confirmed by rugged  cooling rate curve pointed by  arrow.