Automotive Power Inverters

The most compact electric drive in the world

The Insulated Gate Bipolar Transistor (IGBT) is the most important semiconductor power device for applications in the medium power range for voltages > 400 V. To improve its efficiency in terms of switching and on-state performance, ISIT is focusing on the development of ultra-thin field-stop IGBTs. Another aspect is the adaptation to advanced assembly techniques.


Our lighthouse project on this topic is ATEM InMOVE - a collaborative project of the various partners from academia and industry. As part of the project, the participating companies researched technologies for a drive concept for modular distributed electric drives of high speed and thus high power density on the part of the e-machine.


 

Lighthouse project InMOVE

ATEM InMOVE is a joint project of the various partners from science and industry. As part of the project, the participating companies researched technologies for a drive concept for modular distributed electric drives of high speed and thus high power density on the part of the e-machine.


The project partners faced the challenge of making the electric drive as compact as possible. The ISIT scientists worked primarily on optimizing the IGBTs and the power modules for the inverter.

Project partners

Volkswagen AG, Danfoss Silicon Power, Vishay Siliconix Itzehoe GmbH, FTCAP GmbH, Reese + Thies Industrieelektronik GmbH, Fraunhofer ISIT, Kiel University of Applied Sciences: Institutes for Mechatronics & Electrical Power Engineering.

Goals & Challenges

Project InMOVE

  •  Distribution of electric vehicle drive power to several compact electric drive modules
  • Scalable electric drive power
  •  Variable drive architecture using the same components
  • Electric drive modules consisting of a lean, high-speed electric machine with integrated inverter
  • Reduction of the development costs of the electric drive components
  • Very compact design of the power electronics components
  • Pursuit of power electronics technologies in an overall mechatronic approach

»Integrated electric drive systems should be as small, cost-effective and reliable as a screw.«

The solution

System model of the drive inverter

  • Implementation of the thermal behavior of the half-bridge module using a Foster network.
  • Permissible component temperature at maximum load: TJ,max = 175°C
  • Lifetime: driving cycle 8875 s
  • Temperature strokes: min 2°C, max 60°C
  • Service life estimation (number of cycles until defect): Driving distance of 450,000 km
  • With Danfoss Bond Buffers 10-15 times longer service life
  • Improved overall efficiency and performance thanks to IGBTs from ISIT/Vishay

Chip layout, mask set and special processes

  • Metallization of the chip front side with an electroless Ni/Au layer
  • Application of carrier processes for backside processing of thin silicon (50 µm to 150µm).
  • Backside processing by implantation and laser annealing (l =515 nm)
  • Metallization of the chip backside with Ti/Ni/Ag

IGBT-Manufacturing

  • Development and production of three IGBT variants in three learning cycles
  • Modification of the existing standard IGBT architecture (STD-IGBT) to realize injection enhancement devices with 5 µm (IEP5) and 4 µm (IEP4) cell pitch.
  • Iterative device performance tuning by special laser assisted matching of the p/n-doped backside p+ emitter and field stop layer.

Fraunhofer ISIT & VISHAY

IGBT chip development

Based on the system simulations for the modular converter to be developed, the requirements for 1200 V / 200 A trench field stop IGBTs were defined. The IGBTs should be able to operate at 13.5 kHz with the lowest possible switching losses up to Tj,max = 175°C. Figure 3 shows the IGBT developed by Vishay and Fraunhofer ISIT with Ni/Au as gate and emitter connection surface.

Specification of the IGBT

Parameter Target value Layout
Temperature     25°C 125°C 150°C 175°C  
Voltage
[V] 1200          
Rated currentInom [A] 200          
Frequency f [kHz] 13,5 Module coarse specification  
VCEsat (Trade-Off Rg = 1 Ω) dependet [V]   1,95 2,2 2,24 x IE-IGBT
Series resistorRG Ω 1          
Mechanical dimensions:
Chip dimensions [mm2] 15,92 x 12,01    
Gate-Pad Position   Rim center
         
Chip-surface (without Gate) (PAD) [mm2] 153          
Chip thickness [µm] 120-140          
1) Power dissipation: from data sheet reference module, internal Rg = 4,7, RGoff = 0,91 Ω, 30 nH, 25°C)
Eon (1200 V, 200 A) [mJ]   10,5 1)
       
Eof (1200 V, 200 A) [mJ]   11 1)        
Etot = Eon + Eoff [mJ]   21,5 1)        
Short circuit time, tsc     with IE: 7,5 µs (150°C, 800V) without IE: max 7 µs (25°, 900 v)        
Metallization structure              
Front [µm] tbd. Sinterable: Ni-Au or Ni-Pd-Au elektroless        
Back [µm]   Ti 50 / Ni 100 / Ag 1000        
Technical details of the module superstructures

Technology STD IEP5 IEP5 IEP4
Module design

Lead-Frame

5 µm Pitch open module

Lead-Frame

5 µm Pitch open module

"Mold modules"

5 µm  

"Mold modules"

4 µm

1. Modul series (Mod1) 2. Modul series (Mod2)
3. Modul series (Mod3)
4. Modul series (Mod4)
Superstructure technology, front   Aluminum wire bond on N/Au or Al Aluminum wire bond on Ni/Au or Al DBB on Ni/Au Cu Wire bond on DBB DBB on Ni/Au Cu Wire bond on DBB
Superstructure technology, back Ti/Ni/Ag +Sintering on DCB Ti/Ni/Ag +Sintering on DCB Ti/Ni/ag + Sintering on DCB Ti/Ni/Ag + Sintering on DCB
IGBT STD 1. Generation IEPS 2. Generation IEPS 3. Generation
IEP4 5. Generation
Rg, IGBT_intern 0,7 Ω 0,7 Ω 0,7 Ω 0,7 Ω
Metal: Emitter
Ni/Au Ni/Au Ni/Au Ni/Au
Metal: Collector Ti/Ni/Ag
Ti/Ni/Ag Ti/Ni/Ag Ti/Ni/Ag
Diode: Metal: Anode SMIKORN, SKCD_81_C_120_I4F
Al Al Ni/Au Ni/Au
Metal: Cathode solderable, Ni/Ag solderable, Ni/Ag solderable, Ni/Ag solderable, Ni/Ag

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