With the development of LEDs today, SMD beads have become popular because of their relative ease of automated mass production. SMD lamp beads have a processing process called SMT (or reflow soldering chip processing), which is very suitable for the LED lamp industry that is gradually forming scale. The specific processing technology of the patch lamp bead is as follows:
There are often holes in the tin layer of the LED patch. This is caused by the expansion of compounds such as air or flux trapped in the solder during heating in the heating furnace during the LED chip process. Solder joint reliability depends not only on the solder alloy, but also on the metal coating of the LED device and PCB. In addition, the time and temperature profile of the reflow process has a significant impact on the performance of the lead-free solder joint because it affects the wettability and microstructure of the solder joint. If the void ratio is too high, the thermal resistance of the solder increases, the thermal conductivity decreases, and in the environment of the thermal shock test, the bubble is heated and contracted, and the solder is cracked, so that the reliability of the lamp is lowered. Reflow soldering defect detection is still a new thing in the LED lighting industry. Many lighting factories do not understand. We have found that the solder joints of these LED lamps are much higher than the industry's 5-8% standard, which reminds us! ! LED lighting manufacturers must pay attention to the reflow void ratio if they want to increase the price and performance of their products.
PCB and LED device failure solder joints after thermal shock test. Damaged solder joints can lead to open circuit failure conditions, which can result in complete failure of the electrical performance of the luminaire.
Case 1: A customer has no confidence in his product. He commissioned the gold test to test the void ratio and required to observe the soldering effect of the solder paste after reflow soldering. Jinjian used real-time X-ray imaging to inspect the LED package and found a large number of solder voids. The cavity ratio of the thermal pad was more than 30%, far exceeding the industry standard.
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