18650 protected batteries have an electronic circuit.
The circuit is embedded in the cell packaging (battery casing) that protects the cell from [over charge", heat or [over discharge", over current and short circuit.
A 18650 protected battery is safer than an 18650 unprotected battery (less likely to overheat, burst or start on fire).
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Compared with the conventional level or the formal chip, the conventional chip connected to the substrate by the wire bonding is electrically facing upward, and the electrical face of the flip chip is facing downward, which is equivalent to turning the conventional chip over. In terms of manufacturing difficulty, flip chip is generally between horizontal structure chip and vertical structure chip. Horizontal chip manufacturing is the least difficult, followed by flip chip. The most difficult to manufacture is vertical structure chip. The most direct reflection is chip. The yield, the harder the chip is, the lower the yield.
The traditional ball placement process is actually a kind of flip chip packaging process, which is called BGA solid crystal mode. Philips and Nichia's early flip-chip packaging products use this process, and we often talk about the DA packaging process. In a side-by-side relationship, the DA packaging process is simpler and easier to operate.
The advantages of flip chip
First, there is no need to pass the sapphire heat dissipation, and the heat dissipation performance is good The flip-chip structure shortens the heat flow path from the heat source to the substrate because the active layer is closer to the substrate, and the flip chip has a lower thermal resistance. This characteristic makes the performance of the flip chip from the lighting to the heat stable. small.
Second, the luminous performance, high-power drive, higher light efficiency. Under the condition of small current density, the flip chip brightness is not far from the horizontal chip, which is lower than the vertical structure chip; however, the flip chip has superior current expansion performance due to the design of multiple vias, silver emitters, etc. Ohmic contact performance, flip-chip Voltage drop is generally lower than conventional, vertical structure chips, which makes flip-chips have advantages in high-current driving, showing higher light efficiency. It should be noted that the high reliability and high brightness of the flip chip can only be manifested under the drive of a large current. The small current drive is actually not much different from the horizontal chip.
Third, under high power conditions, flip chip is more secure and reliable than a positive chip. In LED devices, especially in the package form of high-power Lens (except for the traditional anti-lumen structure with protective case), more than half of the dead lights are related to the damage of the gold wire, and the flip chip can be packaged in gold-free package. This is the probability that the device will be greatly reduced from the source.
Fourth, the size can be made smaller, reduce the maintenance cost of the product, the optical is easier to match; at the same time, it lays a foundation for the development of the subsequent packaging process; currently the small and medium-sized flip chip has begun to receive attention and development.
From the perspective of the above product performance, flip-chip products have outstanding advantages in certain performance. For example, anti-vibration, cold and thermal shock resistance, it shows superior reliability, which can improve product life and reduce product maintenance costs.
From a market perspective, flip-chips are currently an important branch of high-reliability products, occupying a certain market in high-power packaged devices. With the development of flip chip, some small-sized flip-chips have appeared on the market. The flip chip has a tendency to penetrate into small and medium power. Under this trend, it is believed that the future use of flip chip will be even greater.
Of course, there are still some difficulties in flip chip, the most prominent of which is that the active layer of the chip faces downward. In the process of chip preparation and packaging, if the process is improperly processed, it is easy to cause large stress damage. Packaging factories are very big challenges, and they need to be optimized from chip splicing, sorting, crystal expansion, solid crystal, eutectic, etc., in order to make a truly satisfying product. This is an important challenge to the power of enterprise technology and innovation.
Therefore, flip chip technology can be regarded as the performance of enterprise competitiveness. Strengthening the development of flip chip and related products is of great significance to strengthen the competitiveness of enterprises. However, the future application of flip chip in the lighting industry is still very optimistic, it improves the reliability of lighting products; small size, high power, which means that the lamps can be made more compact. For the future application of tin paste solid crystal flip chip, it will have certain advantages in cost, and will change the current situation of the horizontal structure chip.
Flip-chip is a chip structure that has existed for a long time. It is juxtaposed with vertical structure and horizontal structure. It is characterized by the active layer facing down and the transparent sapphire layer above the active layer. The light generated by the active layer needs to be Pass through the sapphire substrate to the outside of the chip. This is to be distinguished from the flip chip that flipped the chip to a silicon or other material substrate and then still needed wire bonding.