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First, the importance of heat dissipation is relatively neglected:
We often use too small heat sinks or no heat sinks at all. It is important to know that poor heat dissipation can result in a high operating temperature of the chip resulting in a rise in infrared wavelengths and a decrease in the efficiency of the photoelectric conversion. Wavelength rises higher than 850nm, causing the camera CCD to become less sensitive to light, that is, worse night vision. Low photoelectric conversion efficiency is insufficient brightness. Often a few centimeters of heat sinks will have a great effect on the small soldiers.
Second, the wrong hand touch to test the temperature:
Frequently people were startled by themselves, because man's hands on the shell (or heat sink) that exceeds 44 degrees Celsius, can not stand for less than 2-3 seconds, so feel "too hot", in fact, this temperature is not High, will not harm the normal work of electronic components. Moreover, the higher the temperature of the housing (or heat sink) is, the better the "hot" export is. "Energy is immutable" - Imagine: The outer shell (or heat sink) is not hot, is this "hot" going there? If the heat stays on the chip, it will cause the chip to work under high temperature, the night vision effect will be poor, the light decay will be large, and the service life will be short.
Third, think that larger chips must be "brighter" than smaller chips:
Therefore, it is often blindly specified that LEDs with large chip sizes are required. To know: brightness depends on the current, how much current can be used? Depends on the heat treatment, that is: heat dissipation determines the current and thus determines the brightness, rather than the size of the chip determines the brightness. In theory, the same brand of chips, regardless of size, if the same current and voltage (the same power), the same heat generated, the question is: the same heat is scattered in what area? Scattered in the pinhole-like area and scattered in the palm-sized area, the difficulty of heat treatment is very different. In terms of heat dissipation, each company has different technologies, different equipment, and different heat-dissipating materials. Therefore, the ability to handle the same “heat†in different areas is different.
For example: if the 1.2A current is provided on the 28mil chip and the 42mil chip, the voltage is slightly the same (about 1.7V), so the power is slightly the same (about 2W), and the generated heat is slightly the same. The problem is: Dispersing this 2W of heat over the area of ​​the 42mil chip is easier to handle, and it is harder to disperse it on the 28mil chip. The use of traditional silver glue to "solid crystal" packaging methods, the thermal resistance is generally 20 °C -30 °C / W, using eutectic technology package, the thermal resistance is generally 6 °C -10 °C / W, which It shows that the cooling effect is very different. The drive currents that can be used in the above two are greatly different, and the brightness is also very different.
Of course, the use of advanced heat-dissipation technology and the use of small chip packages, high current drive method is also limited, if the above 2W heat on the area of ​​the 10mil chip, even if the eutectic process package, it is currently difficult to complete the heat Export. Looking forward to the future in the cooling technology, materials, more progress, may be able to achieve the use of smaller chips, the price is lower, but the night vision effect is still more advanced infrared LED.
To sum up, the night vision effect of a large-sized chip is not necessarily stronger than that of a small-sized chip, and the quality of the heat treatment is determined depending on the quality of the heat treatment. Therefore, the eutectic process packaging technology is one of the important means for the current cost performance improvement and should also be the future trend.
Infrared LED Mistakes in Security Surveillance Cameras
At present, there are some misunderstandings about the use of infrared LEDs. The most important ones are: