Let's take a look at its test purpose: By high and low temperature test chamber to simulate environmental temperature change improve the electronic environment adaptability, such as temperature, humidity, temperature cycle, the acceleration of components or may occur in chemical reaction (such as corrosion caused by steam or other ions, surface contamination, and gold - the production of aluminum metal compounds, etc.), to eliminate potential defects in advance.
Many failures of electronic components are caused by various physicochemical changes in the body and surface. When the ambient temperature increases, the chemical reaction rate is greatly accelerated, and the fault process is also accelerated. Defective components are exposed. Jiafeng Core City: http://www.ic-jfsd.com/
High temperature storage test has a good screening effect on surface contamination, poor lead bonding and oxide defect.
Two, the test principle
High temperature storage is to simulate high temperature conditions in the test chamber, to impose high temperature stress on the components (no electrical stress), accelerate the chemical reaction rate of various physical and chemical changes in the body and surface of the components, accelerate the fault process, so that the defective parts are exposed as soon as possible; Eliminate potential defects in advance.
Xiaobian take you to see the characteristics of high temperature storage screening:
(1) For mature equipment with high technology and design level, because the equipment itself is very stable; The biggest advantage is that it is easy to operate. Can be carried out in large quantities of test screening, less investment, screening effect is good, is currently commonly used screening test items.
(2) High temperature storage screening effect, through the same temperature is two storage qD, stable first-class performance of components, reduce parameter drift in use.
Three, test equipment
High and low temperature test chamber, suitable for high temperature, low temperature (alternating) cycle, constant temperature change to check the basic reliability of the performance indicators of the instrument and equipment. Product components and materials may soften at high temperatures, reduce efficiency, change in characteristics, potential damage, oxidation, etc.
4. Exposed defects
Electrical stability, metallization, silicon corrosion and lead bonding defects of components.
Five, matters needing attention
1. Determination of temperature-time stress.
The higher the screening temperature is, the better it is without damaging semiconductor devices, so the storage temperature should be increased as much as possible. The storage temperature should be determined according to the shell structure, material properties, assembly and sealing process, and special attention should be paid to the reasonable determination of temperature and time.
There is a misconception that the higher the temperature, the longer the time, the tougher the screening test, which is wrong. For example, if the storage temperature is too high and the storage time is too long, the degradation of the equipment will be accelerated, the packaging of the equipment will be damaged, and the wire coating may also lead to micro-cracks and wire oxidation, so that the weldability is poor.
The principle for determining the temperature and time correspondence is to keep the stress intensity of the force applied to the component constant, that is, to reduce the storage time if the storage temperature increases.
For dry semiconductor devices, the maximum storage temperature is limited by the temperature of the eutectic point of metal and semiconductor materials, and is not affected by the bonding materials used in device packaging. Shell coating and marking while thermal temperature and lead oxidation temperature limits. Therefore, the maximum storage temperature of the device with gold-aluminum bonding is 150 ℃, the maximum storage temperature of the device with al-Aluminum bonding is 200℃, and the maximum storage temperature of the device with gold-gold bonding is 300℃. For capacitors, the maximum storage temperature is not only limited by the heat resistance temperature of the medium, but also by the heat resistance temperature of the coat, the label and the oxidation temperature of the wire. Some capacitors are also limited by the impregnation material of the casing. Therefore, the maximum storage temperature of the capacitor is generally taken as its positive limit temperature.
2. Most high temperature storage takes place after packaging, and semiconductor devices also take place in the pre-packaging circular stage or after bonding, or before and after packaging.
3. According to the national military standard, after the high temperature storage test, the test and comparison of components must be completed within 96 hours.