Optical modules are generally used in monitoring equipment, switches, radio and television, and other products. At present, 10G, 40G, and 100G optical modules are very popular. In these fields, it is necessary to ensure the stability and accuracy of the normal operation of the product, so it is necessary to conduct reliability testing before it is officially put into production. What are the reliability testing items for optical modules? Let’s take a look.
Stress Reliability in De-energized Environments (Storage/Transport)
The storage environment of devices varies widely. Some devices may be placed in the northeast, where the temperature is tens of degrees below zero; some devices may be shipped to the Middle East, where the ambient temperature is more than 50 degrees, and the temperature in the car can even reach more than 70 degrees. It is therefore necessary to verify that the device can withstand these extreme temperatures before shipping. Since it is only for transportation and storage, it is not electrified. Generally, there are low-temperature storage and high-temperature storage. After a lot of experiments, it was found that active devices are unlikely to fail at low temperatures, so the low-temperature storage time is only 72 hours, and it is even unnecessary. And high-temperature storage is generally stored at 85 ℃ for 2000h, if the highest working temperature of the device is higher than 85 ℃, then it is stored at the highest working temperature of the device. Compared with active devices, passive devices use more glue. A very important parameter of glue is T**, which is the temperature point at which the mechanical properties of the glue change. Therefore, passive devices are generally stored at a low temperature of -40°C for 1000h.
High and Low-Temperature Cycle
Almost all optical devices have to undergo high and low-temperature cycles before leaving the factory. The thermal expansion coefficient of each material is different. Only under severe temperature changes can we test whether there is a risk of failure of different materials. The heating and cooling rate of the temperature cycle is at least 10°C/min, and at the two temperature points of 85°C and -40°C, it must stay long enough to allow the device to reach the ambient temperature. For optical modules used indoors, 100 thermal cycles are OK, and for outdoor optical modules, 500 thermal cycles are required. For modules with TEC temperature control, the TEC needs to be turned on when the temperature is cycled.
The damp heat is not necessarily 85°C/85%RH, it can also be a combination of other temperatures and humidity (75°C/90%RH), but 85°C/85% is the most commonly used damp heat condition. Damp heat can test the airtight properties of airtight devices and the reliability of non-airtight devices. The GR-468 does not distinguish between indoor and outdoor applications, and the recommended 85°C/85%RH time is 500h, while the GR-1221 recommends that the dual 85 reliability for outdoor applications should be at least 2000h. It should be noted that the time recommended by these standards is only a minimum reference, and the specific time can be selected according to the characteristics of the product, or it can be combined with the later more stringent charged double 85.
Live (Working State) Reliability
Chips/devices/modules run at full power and operate at maximum current or maximum power in order to accelerate failure. The temperature was set at 85°C for outdoor applications and 70°C for indoor applications. For chip-level reliability, the duration is 5000h; for a device or module-level reliability, the duration is 2000h. Especially for PD, the temperature is generally set at 175°C and the time is 2000h.
Cycle Humidity Reliability
Reliability experiments under conditions of simultaneous changes in humidity and temperature may cause condensation or frost. This lab is only for devices and modules for outdoor applications. The temperature and humidity control curve of this experiment is shown in the figure below. 20 cycles are required, and one cycle takes 24 hours; at least half of the cycles, the last step should be lowered to -10 °C, and the stay should be no less than 3 hours.
Damp Heat Reliability
This experiment is for non-hermetically packaged devices, 85°C/85%RH, for 1000 hours or 2000 hours (depending on the specific product and application). It should be noted that the higher the operating current/output power is, the better, because it will generate a lot of heat, which will change the environment around the device. For lasers, it is sufficient to keep the operating current at 1.2 times the threshold current. The above tests basically include most of the reliability certification items. For all the above items, if you need to use modules for experiments, the number is generally 11; if you use devices or chips for verification, the number is generally 22. There is no failure to pass reliability. Otherwise, do it again. But do it again and there is no need to take out so many devices/modules.