Because the LED light strip is in series parallel structure, when a short circuit occurs in a group of circuits, it will cause the voltage of other LEDs in the same group to rise, the brightness of the LED will increase, and the corresponding heating capacity will also rise. The most obvious thing is that in the 5050 lamp belt, when there is a short circuit in any chip circuit of the 5050 lamp belt, the current of the lamp bead that causes the short circuit will double, that is, 20mA becomes 40mA, and the brightness of the lamp bead will become very bright, but at the same time, the heat will also increase sharply, and the circuit board will be burned in a few minutes. However, because this problem is relatively obscure, we generally don't pay much attention to it, because the short circuit does not affect the normal light emission of the light band. If the staff in charge of the test only pay attention to whether the LED lights up, and don't check the abnormal brightness, or don't do the appearance inspection, but only do the electrical test, this problem will often be ignored, This is also why many LED lamp belt manufacturers always encounter customers' complaints that their products are hot, but they can't find the reason.
Solution:
1. Circuit design: the circuit should be wide enough for wiring as far as possible, and the spacing between lines should be 0.5mm, and the rest of the space should be full. The thickness of copper foil should be thickened as far as possible without violating the customer's requirements for the total thickness of the circuit board. The general thickness is 1~1.5 oz.
2. Production process:
A. when printing solder paste, try not to allow tin connection between pads, so as to avoid welding short circuit caused by poor printing;
B. Avoid short circuit when mounting;
C. Check the position of the patch before reflow;
D. After reflux, conduct appearance inspection first to ensure that there is no short circuit in the light band, and then conduct electrical test and recheck. During recheck, pay attention to whether the LED is abnormally bright or dark after it is lit.
