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(8) why did the PCR refrigerator fail after a long time?

时间:2018-05-02 来源:EASTWIN浏览次数:176

             Problem diagnosis             
 
Dongdong: the new PCR instrument has not been used for a long time. The semiconductor cooler is broken. What's the matter?

Long long: in the PCR instrument, the most vulnerable and the most critical part is probably the semiconductor cooler (Thermo-electricModule). It is very likely to damage the "fragile heart" in the short term, but the probability of this situation is very small.

The semiconductor cooler has a certain life span, and its life span is not related to the time of its production, but it is related to the number of cold and hot cycles, that is, the actual number of customers running. Therefore, for some scientific research users, there is not much consumption. PCR has been used for more than 5 years. And for some industrial and commercial users (such as: PCR service company), three shifts to work, PCR instrument is almost no shutdown, continuous work, maybe 2 years, even shorter time, the life of the semiconductor refrigerator has come. So, we will PCR the life of the instrument, we must know the actual use frequency of customers, can not simply talk about the machine for a few years, that machine used a few years. Dongsheng dragon ETC811PCR instrument has a record of the actual usage time of customers, and can accurately know the customer's use time.

The semiconductor cooler is actually a very fragile semiconductor device. It is welded in series by two pairs of small pairs of fragile bismuth telluride semiconductor particles (P/N section), which are made up of tens of pairs or hundreds of pairs, and between two ceramic substrates with only a few millimeters apart. When a DC power supply is applied to the semiconductor refrigerator, the electrons move from the N type semiconductor to the P type semiconductor, releasing the heat, so that the one side of the semiconductor cooler is cooled, the other side becomes hot, and the heat is pumped from one side to the other side. Change the direction of the current, the phenomenon is still. So this principle can be used to control the hot and cold surfaces by adjusting the direction and size of the current. PCR is precisely using the characteristics of the semiconductor cooler, which makes PCR move from the water bath and compressor to the era of electronic refrigeration. The characteristics of the semiconductor refrigerator are that the refrigeration speed is fast, the control precision is high, it is easy to realize automation, small volume, clean and hygienic.

However, because of its own fragility, strength of different, easy to produce cracks and other weaknesses, coupled with hundreds of solder joints, so that its reliability is greatly reduced.

The worst thing is that its life can't be measured, and it is expected that even semiconductor manufacturers can only predict their lifespan only according to statistical data, and do not guarantee how much each piece of devices can reach. Moreover, the life of the semiconductor cooler has a great relationship with the conditions of use and the way of use.

1. the natural aging of semiconductor material will change its nature, and the Sebek coefficient and the Parr sticking coefficient will change.

2. under the action of cold and heat alternating and pressure, electrical properties of semiconductor materials are reduced or damaged due to physical changes. Such as cracks, welding layer cracking, shedding and so on.
3. under the effect of cold and heat shock, the welding surface has fatigue crack or fracture under the action of heat expansion and cold contraction stress, and even the electrical property is reduced or damaged.

 



 

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