Rohm focuses on the automotive market and releases Schottky diodes with a 90% drop in drain current

Recently, Rohm released a 200V Schottky barrier diode (SBD for short). In fact, the diode is a very common electronic component, which is widely used in rectifier circuits, detection circuits, voltage regulator circuits, and various modulation circuits. However, it is also very unusual to be able to make the diode to the extreme. Mizuhara Tokuken, director of the Technology Center of ROHM Semiconductor (Beijing) Co., Ltd., said, "Rohm's diode products account for about 10% of the global market share, and 20% of the global automotive market, ranking first. Schottky diode sales account for about 8% of the total sales."

According to the classification of current and voltage, diodes are divided into TVS (Zener diode), Schottky diode, rectifier diode, and SiC Schottky diode. Among them, TVS is generally used for small voltage and small current, Schottky diode is used for small voltage and large current, rectifier diode and fast recovery diode are used for large voltage and large current, and SiC Schottky diode is used for higher voltage.

Mr. Tokuken Mizuhara, Director of the Technology Center of ROHM Semiconductor (Beijing) Co., Ltd.

Especially with the development of electric vehicles, the degree of automobile electrification is getting higher and higher. In the entire car, in addition to the battery motor, from the camera to the host inverter, all Schottky diodes are needed. So, how many Schottky diodes are used in a car? Mizuhara Dejian introduced, "One ECU will use 3-4, and there are about 100 ECUs in a car. It can be seen that a car alone requires 300-400 Schottky diodes for ECU applications."

In recent years, in drive systems such as 48V mild hybrids, "mechatronics" that integrates motors and peripheral components into one module has become a trend technology, and the demand for high-voltage, high-efficiency, ultra-low IR Schottky barrier diodes that can operate in high-temperature environments is increasing. On the other hand, in systems that previously used 150V products, high performance and high reliability requirements are becoming increasingly stringent, so SBDs are required to have higher voltage resistance performance. For automotive systems such as powertrains including xEVs, ROHM has developed 200V voltage-resistant SBDs " RBxx8BM200 " and " RBxx8NS200 ".

Both high efficiency and miniaturization are required

Rohm's Schottky diodes include four series: ultra-low VF series (RBS), ultra-low IR series (RBxx8 series), low VF medium IR series (RBR series), medium VF low IR series (RBQ series). Among them, the RBS series is mainly used in ultra-low loss rectification, reverse protection and external LCD backlight and other LED driver circuits; the RBR series and RBQ series are mainly used for secondary rectification, freewheeling diodes and reverse protection in AC-DC/DC-DC circuits; the RBxx8 series focuses on ultra-low IR.

Mizuhara Dejian introduced, "At present, 200V products still mainly use fast recovery diodes or rectifier diodes, but the package is large, and the chip size is also large. If Schottky diodes are used, the package will become smaller and the chip size will also become smaller. For example, DPAK and D2PAK surface-mount products can save more space. In addition, all Rohm products support AEC-Q101 and are suitable for automotive applications. They can operate at high temperatures in vehicles, are more energy-efficient, and are more compact."

Compared to Rohm's general products, the IR of the RBxx8 series products is reduced by about 90%, and a withstand voltage of up to 200V can be achieved, so that the FRD used in the automotive system that requires a withstand voltage of 200V can be replaced with SBD. Compared with FRD products, the VF characteristics of the RBxx8BM/NS200 can be reduced by about 11%, which helps to reduce the power consumption of applications. In addition, the lower VF can suppress heat generation, so compared with previous products, a small package design of the same size can be achieved.

Mizuhara Tokuken also said, "Currently, medium-power packages are also under development. In the future, the previously used 5.9×6.9mm FRD products will be replaced with 2.5×4.7mm small packages, reducing the mounting area by 71%."

The secret to reducing IR by 90% lies in metal materials

I was very surprised when I heard that the IR of the RBxx8 series was 90% lower than that of Rohm's ordinary series products. At the press conference, reporters asked this question many times: What is the reason for the 90% reduction in IR of the RBxx8 series?

Mizuhara Dejian explained, "The demand for high-efficiency Schottky in automotive and power equipment is getting higher and higher, but compared with ordinary FRD, Schottky's IR is higher and it is difficult to operate stably, so we have to find a way to reduce Schottky's IR. How can we reduce Schottky's IR? We mainly improved a dedicated barrier metal in SBD. FRD is 'semiconductor + semiconductor', but Schottky is 'semiconductor + metal'. We changed the characteristics of the metal in Schottky, and the IR was reduced. After the IR is reduced, the SBD can operate stably in a high temperature environment without thermal runaway. The so-called thermal runaway is that as the leakage current increases, the temperature increases. The higher the temperature, the greater the leakage current, and the temperature continues to rise, which will form a vicious cycle. After the IR is improved, there will be no thermal runaway. Although the temperature in the car rises, it will not continue to rise."

The author asked again whether there were any changes in the production process. Mizuhara Dejian said, "The production process has not changed, but the metal material in the Schottky diode has been changed from ordinary material to platinum material."

Finally, Mizuhara Tokujian emphasized, "Currently, 200V product packages are mainly DPAK and D2PAK. Next, DPAK and D2PAK will be made smaller and TO-277 will be used. Existing PMDS, SMC, and SMA products will use PMDE, a more miniaturized and modeled package. We will strive to make the package smaller and smaller and expand the product line while maintaining the same characteristics."