Thin type thermal fuse is specially developed for lithium ion battery over temperature protection.

Working Principle:

The thin type thermal fuse is connected to the circuit with a low melting point alloy, which is surrounded by a fluxing resin, and the low melting point alloy is connected to the metal guide plate and sealed by the plastic material. When the temperature inside the battery rises to a certain level as a result of a short circuit or other causes, either inside or outside the battery, the thermal fuse immediately adjacent to the battery cell will rapidly fuse, thereby cutting off the external circuit of the battery and preventing the battery from exploding and producing a life-threatening injury event. As handheld electronic devices need to be more and more portable, the size of the thermal fuse needs to be as small and thin as possible. Currently the thinnest thermal fuse can be done 0.65mm thick, width can be done 2.7mm. thermal fuse internal resistance is also very small, only 8mΩ or so, standby power consumption is very small, can greatly increase the standby time of lithium-ion batteries.

Disadvantages:

First of all, the thin thermal fuse is non-recoverable, not as good as the PTC, even if there is an accidental malfunction that causes the PTC to actuate, once the malfunction is removed, the battery can still continue to work. Once the thermal fuse operates, the whole battery can no longer work. Of course, as the quality of lithium-ion batteries is getting better and better, the probability of such accidental failure is getting smaller and smaller, once the abnormality does not allow the battery can continue to use, but rather become the advantages of the thermal fuse. After all, the cost of a battery is minimal compared to the cost of a personal injury. As the saying goes, it’s better to err than to let go. As long as the cell phone battery has had one high temperature failure, who would dare to keep this potential bomb around?

Second, it can not be welded and processed in an ordinary way, such as PPTC, can withstand a short period of high temperature, so it can be welded through the reflow oven, can be directly injected into the battery, but the thermal fuse can only be spot welding, laser welding and other local welding methods, in order to prevent the thermal fuse fuse meltdown.

The current use of more 98 ℃ and 92 ℃ of thin thermal fuse, in 1 ℃ / min of the heating rate, 98 ℃ thin thermal fuse of the melting temperature of 94 ± 3, 92 ℃ thin thermal fuse of the melting temperature of 89 + 3 / -4, that is, 85 ℃ ~ 92 ℃. Currently, there are manufacturers in the development of higher melting temperature of the thin-type thermal fuse.