Currently one of the most pressing issues of low-frequency power semiconductor thyristors and diodes is modifying the design of discrete semiconductors to prolong their service life, reduce electrical and heat losses, and increase operating power [3-4]. This is mostly caused by the constantly growing production, transmission, transformation and consumption of energy, as well as the need to keep improving the technical and economic parameters of converting technology [1].

However, the use of traditional (for modern IGBT modules) approaches to increase the parameters of power thyristors and diodes is not always advisable, since these approaches are based on a rather long and expensive rework, including the use of cheaper and more advanced composite materials, reduction in the amount of structural elements, as well as changing individual structural elements to reduce the cost of mass production. Applying these approaches brings the term for releasing the upgraded product to the market to 2-3 years (which is often unacceptable for the customer), and the costs of developing this product increase to the range of 300,000 – 400,000 EUR, nullifying the economic effect of the implemented improvements. In addition, even more risks arise for example in terms of long-term field trials by the end user or difficulties in carrying out product certification [2]. In this regard, it is still important to use the approach of optimizing the parameters and features of power semiconductor elements with a minimum amount of reworking other structural elements, and the use of modern modeling tools makes it possible to reduce the iteration of upgrading, to reduce development costs and the time to bring the upgraded product to the market down to 1 year or less.

 

Reduction of static and thermal parameters in a dual-component module with a baseplate width of 60 mm

A dual-component A2-type power thyristor module with a baseplate width of 60 mm rated for a voltage of 1800 V and an average current of 540 A was upgraded at a customer’s request (appearance of the module is shown in Figure 1). The current product line of A2 modules is shown in Figure 2.

 

Figure 1: Appearance of a А2 module with baseplate width of 60 mm
Figure 1: Appearance of a А2 module with baseplate width of 60 mm

 

In this version of the design, the electrical and thermal contact of the semiconductor elements is provided with a clamping structure providing an increased cycle resistance and resistance to surge currents. 

 

Figure 2: Existing lineup of А2 modules
Figure 2: Existing lineup of А2 modules
 

The process of modeling the main electrical parameters and characteristics resulted in the following solutions to achieve the required thermal and electrical losses of the module:

– Increasing the diameter of the semiconductor element and optimiz ing the topology to increase the active cathode area by 10%;

 

Figure 3: Calculated diffusion profiles of a standard MT*-540-18-A2 and an optimized MT*-700-18-A2 thyristor module in comparison with experimental data
Figure 3: Calculated diffusion profiles of a standard MT*-540-18-A2 and an optimized MT*-700-18-A2 thyristor module in comparison with experimental data

 

– Reducing the specific electrical resistance of the original silicon wafer;

– Reducing the thickness of the diffusion element and optimizing the diffusion profile (Figure 3 shows data on the calculated and experimental values).

After a pilot batch was produced qualification tests confirmed main results of the modeling:

1. Static losses – threshold voltage (VT(TO)) decreased by 5%, dynamic resistance (rT) by 10%. Figure 4 shows data on the calculated and experimental values of static losses in the open state for a standard MT*-540-18-A2 and an optimized MT*-700-18-A2 thyristor module in comparison with the measured values for alternatives from other manufacturers.

2. Heat loss – junction-case thermal resistance (Rthjc) reduced by 10%. Figure 5 shows the experimental values of the thermal resistance of a standard MT*-540-18-A2 and an optimized MT*-700- 18-A2 thyristor module in comparison with the measured values for alternatives from other manufacturers.

3. The surge current in the open state – increased by 20% at the maximum temperature of the pn junction Tjmax = 130°C. Figure 6 shows the experimental values of the surge current in the open state for the standard MT*-540-18-A2 and the optimized MT*-700- 18-A2 thyristor module in comparison with the measured values for alternatives from other manufacturers.

 

Figure 4: Static losses of a standard МТ*-540-18-А2 and optimized МТ*-700-18-А2 thyristor modules
Figure 4: Static losses of a standard МТ*-540-18-А2 and optimized МТ*-700-18-А2 thyristor modules
Figure 4: Static losses of a standard МТ*-540-18-А2 and optimized МТ*-700-18-А2 thyristor modules
 
 
Figure 7: Updated lineup of the А2 modules
Figure 7: Updated lineup of the А2 modules
 

This article originally appeared in Bodo’s Power Systems magazine.

 

About the Author

Dmitry Titushkin works as a Research and Development Engineer at Proton-Electrotex JSC, a Russian company mainly involved in development, manufacturing and sales of bipolar power semiconductor devices — diodes and thyristors, power assemblies and IGBT modules.

Alexey Surma is head of Research and Development Center at Proton-Electrotex, a Russian company, which develops and manufactures power semiconductor diodes, thyristors, modules, heatsinks, IGBTs and power units for various electric energy converters. The company was founded and started production in 1996. As the head of R&D Center, Mr Surma is mainly responsible for the development of new technologies and products.

Sergey Antonov worked at Proton Electrotex.


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