Die-cast PIM technology provides higher energy efficiency and power density in a smaller package. Get it now!

Author: Zhou Jinchang

Application Engineer at ON Semiconductor

One of the most common devices used for this purpose is the Converter-Inverter-Brake (CIB) module. Figure 1 shows the basic outline of a CIB module. The module circuit consists of three parts: converter, inverter, and brake. The CIB gets its name from the initials of these components - C, I, and B. During normal operation, the input of the converter stage (R/S/T in Figure 1) draws three-phase power from the grid and regulates the AC power to DC power.

There are two commonly used three-phase voltages: 240V level and 400V level; depending on the voltage size, a 650 V CIB module or a 1200 V CIB module is recommended. Immediately after the converter stage, capacitors are connected to the DC bus to eliminate voltage ripple from the inverter caused by the use of dynamic power. The inverter stage then chops the DC input into an AC output to power the motor. This is achieved by turning on and off the 6-IGBT in this part of the module. The output voltage/current is controlled by pulse width modulation; the signal is constructed to produce the required power to drive the motor at the desired speed and direction.

When ON Semiconductor defines the ampere rating of a TMPIM power module, the current refers to the IGBT rating in the inverter section. For reference, a 1200 V 25 A TMPIM CIB module will provide 5 kW of motor power. A 35 A TMPIM will output 7.5 kW; a 50 A can provide 10 kW, 15 kW, and 20 kW. It is important to note that kilowatt output power ratings are usually provided. This power rating can vary significantly if the application uses different control and cooling settings.

The maximum output power is therefore defined by the design of the power module and how the module is controlled and cooled. ON Semiconductor's motion control online simulation tools can help you select the most appropriate module. When the motor stops and decelerates, its operation switches to regeneration mode. The power generated by the motor is transferred back to the DC bus capacitor. When the power generated is too large, it overcharges and damages the capacitor. In this case, the brake IGBT turns on, directing the excess current to the external brake resistor connected in series with the IGBT. This arrangement dissipates the excess regenerative power and keeps the capacitor voltage at a safe level.

In applications with fans, pumps and heater drives, the regenerative power is not significant and the brake can be removed. In this case, the module is called a CI module, which stands for Converter Inverter Module.

Figure 1: Basic architecture of a converter-inverter-brake (CIB) module

Common CIB/CI modules use a gel-filled package to encapsulate the power components within the housing. This approach involves a multi-stage manufacturing process, but perhaps more importantly, it inherently incorporates additional layers of non-uniform materials and interfaces, which weaken the module and reduce its robustness. ON Semiconductor has developed the Die-Molded Power Integrated Module (TMPIM) to challenge this norm. As the name suggests, the developed process is a single-stage packaging technology that creates both the package and the dielectric surrounding the components from the same material.

The die-cast process eliminates the need for multiple materials, including the plastic boxes typically used to house components, glues, and encapsulants that surround power devices. In addition to an overall more efficient manufacturing process, die-casting also provides ten times the temperature cycle, which directly improves energy efficiency. This provides greater flexibility in the size and shape of the final product, and provides higher reliability and power density.

To date, ON Semiconductor has developed and released a number of modules using its TMPIM process for applications with power requirements between 3.75 kW and 10 kW, including six 1200 V CIB modules with current ratings of 25 A, 35 A and 50 A. These devices are available in a DIP-26 package and include CBI and CI variants. Now, ON Semiconductor will expand its product range to offer 1200 V CBI modules with current outputs of 75 A and 100 A, and launch a series of 650 V modules with current ratings between 35 A and 150 A. These devices will be able to address applications with power requirements up to 20 kW and will be available in a QLP package configuration. The DIP-26 package has terminals on both sides, while the QLP is a quadrilateral leadframe package with terminals on all four sides.

To accommodate higher output power levels, ON Semiconductor has further developed its TMPIM process, launching standard and enhanced versions. The enhanced version uses an advanced substrate with a thicker copper layer, eliminating the need for a base plate, keeping the dimensions of the two packages the same. This makes it easier for manufacturers to migrate between the two based on their power requirements. Removing the base plate reduces the volume by about 57% compared to a comparable module, while increasing thermal conductivity by 30% over the standard TMPIM package.

Figure 2: ON Semiconductor’s standard and enhanced TMPIM packages

By increasing the thickness of the copper used, the package has lower thermal resistance and higher thermal mass, while an advanced substrate further improves the module’s reliability.

As mentioned earlier, the entire assembly, including the chip, lead frame, and wire bonds, is encapsulated in the same epoxy that forms the package. Both the CBI and CI modules have the same pinout in the DIP-26 package. In the CI module, the brake terminals have no internal connection.

ON Semiconductor’s own competitor analysis shows that modules manufactured using its die-cast mold process can provide ten times higher temperature cycling, three times higher power cycling, while having better thermal conductivity and overall energy efficiency.

In motor drive, servo and HVAC applications, VSD usually adopts power modules of CIB or CI circuit. Through the innovative TMPIM technology, ON Semiconductor develops power integrated modules, which can now provide higher energy efficiency and power density in a smaller package.

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