Design and Analysis of a 15-kV Package for Wide Bandgap 

Semiconductor Devices 

by Dimeji Ibitayo and C. Wesley Tipton 

ARL-TR-3225 May 2004 

Approved for public release; distribution unlimited. 
NOTICES 

Disclaimers 

The findings in this report are not to be construed as an official Department of the Army position 

unless so designated by other authorized documents. 

Citation of manufacturer’s or trade names does not constitute an official endorsement or 

approval of the use thereof. 

Destroy this report when it is no longer needed. Do not return it to the originator. 
Army Research Laboratory 

Adelphi, MD 20783-1197 

ARL-TR-3225 May 2004 

Design and Analysis of a 15-kV Package for Wide Bandgap 

Semiconductor Devices 

Dimeji Ibitayo and C. Wesley Tipton 

Sensors and Electron Devices Directorate, ARL 

Approved for public release; distribution unlimited. 
ii 

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data 

needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, 

to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. 

Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid 

OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

May 2004 

2. REPORT TYPE 

Final 

3. DATES COVERED (From - To) 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Design and Analysis of a 15-kV Package for Wide Bandgap Semiconductor 

Devices 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

5e. TASK NUMBER 

6. AUTHOR(S) 

Dimeji Ibitayo and C. Wesley Tipton 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

U.S. Army Research Laboratory 

ATTN: AMSRD-ARL-SE-DP 

2800 Powder Mill Road 

Adelphi, MD 20783-1197

8. PERFORMING ORGANIZATION 

 REPORT NUMBER 

ARL-TR-3225 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

U.S. Army Research Laboratory 

2800 Powder Mill Road 

Adelphi, MD 20783-1197 

11. SPONSOR/MONITOR'S REPORT 

 NUMBER(S) 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

Approved for public release; distribution unlimited. 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

The development of wide bandgap semiconductor materials such as silicon carbide (SiC) has made possible devices that exceed 

the voltage ratings of conventional component packaging schemes. As such, a new class of high voltage packages must be 

developed to realize the full potential of these technologies. We report on the electrostatic analysis and design of a 15-kV 

ceramic package using the ANSYS1

 Multiphysics software. To baseline our work, a standard ceramic package was 

characterized and modeled for high voltage operation. With this information, a new package geometry was designed, and 

additional SiC die requirements were identified via finite element simulations. 

1

Not an acronym. 

15. SUBJECT TERMS

15 kV package, SiC, ANSYS 

16. SECURITY CLASSIFICATION OF:

19a. NAME OF RESPONSIBLE PERSON

Dimeji Ibitayo 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unlcassified 

c. THIS PAGE 

Unclassified 

17. LIMITATION

OF 

ABSTRACT 

UL 

18. NUMBER 

OF PAGES 

18 

19b. TELEPHONE NUMBER (Include area code) 

301-394-5514 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
iii 

Contents 

List of Figures iv

List of Tables iv

1. Introduction 1

2. Modeling/Design 1

3. Experimentation 8

4. Summary 10

Distribution List 11
iv 

List of Figures 

Figure 1. Standard package geometry.............................................................................................2 

Figure 2. Electric field plot at the lead region of the standard package..........................................2 

Figure 3. High-voltage package geometry......................................................................................3

Figure 4. Electric field plot at the lead region of the high-voltage package...................................3 

Figure 5. Electric field plots showing the performance of Fluorinert under an applied voltage 

of 15 kV with surface potential terminated 0.2 mm from the edge of the die..........................4 

Figure 6. Electric field plot showing the performance of Fluorinert under an applied voltage 

of 15 kV with surface potential terminated 0.5 mm from the edge of the die..........................4 

Figure 7. Electric field plot showing the performance of the epoxy under an applied voltage 

of 15 kV with surface potential terminated 0.2 mm away from the edge of the die.................5 

Figure 8. Electric field plot showing the performance of the epoxy under an applied voltage 

of 15 kV with surface potential terminated 0.5 mm away from the edge of the die.................5 

Figure 9. Electric field plot showing the performance of Fluorinert under an applied voltage 

of 10 kV with surface potential terminated 0.2 mm from the edge of the die..........................6 

Figure 10. Electric field plot showing the performance of SF6 under an applied voltage of 

10 kV with surface potential terminated 0.2 mm away from the edge of the die.....................7 

Figure 11. Electric field plot showing the performance of SF6 under an applied voltage of 

10 kV with surface potential terminated 0.5 mm away from the edge of the die.....................7 

Figure 12. Electric field plot of Vendor A package showing failure at 1.8 kV. .............................8 

Figure 13. Photograph of Vendor B package showing where arcing occurred. ............................9 

Figure 14. Electric field plot of the Vendor B package under 8-kV operation...............................9 

List of Tables 

Table 1. Material properties.............................................................................................................1 
1 

1. Introduction 

This analysis was performed in support of the Defense Advanced Research Projects Agency 

Wide Band-gap Initiative High Power Electronics program. One of the goals of this program is 

to demonstrate silicon carbide (SiC) technology for use in high voltage applications. The U.S. 

Army Research Laboratory performed a series of electrostatic analyses to determine the 

appropriate package geometry for 10- to 15-kV devices. In these analyses, the operating ambient 

was assumed to be at 25 °C. These finite element analyses were coupled with high voltage 

experimentation for validation purposes. 

2. Modeling/Design 

The primary tool used in these analyses was ANSYS1. ANSYS is a finite element analysis 

modeling software package used in a variety of engineering applications. An electrostatic field 

analysis was performed to determine the electric field distribution caused by applied voltage. 

The procedure for doing the electrostatic analysis consisted of three main phases using a 

combination of the ANSYS graphical user interface (GUI) and commands: (1) build the model, 

(2) apply loads and obtain solution, and (3) review results. 

To build the model, the preferences were set for an electric analysis: This was done to ensure that 

the elements needed for the analysis were available. Once the electric preference was set, the 

ANSYS preprocessor (PREP7) was used to define the element type, the material properties, and 

the model geometry. These tasks are common to most analyses. The element type used was 

PLANE121, the ANSYS 2-D, eight-node electrostatic element. For an electrostatic analysis, the 

permittivity (PERX) material property must be defined. Table 1 provides the permittivities of 

the materials used in the simulations as well as their corresponding breakdown, electric field 

strengths. 

Table 1. Material properties. 

Material Relative 

permittivity 

Field 

strength 

(MV/m) 

Air 1.0001 3 

Alumina 9.5 16.9 

*Epoxy 4.0 22 

Fluorinert 1.98 15.75 

SiC 10.2 300 

SF6

† 1.0021 9 

*Duralco 4460 

†

Sulfur hexafluoride 

 1

Not an acronym. 
2 

Figure 1 shows a comparison of a “standard” design as modeled in ANSYS. The light blue areas 

represent the ambient environments that were varied among several materials including air, 

epoxy, Fluorinert, and SF6. These materials were evaluated as encapsulants. The white areas are 

alumina, the orange areas are metals (lead, bond wires, and base plate), and the black area is the 

silicon carbide die. The silicon carbide die had a metallized top surface, the extent of which was 

varied. After the areas were created, they were meshed. 

Figure 1. Standard package geometry. 

When the meshing procedure was complete, the second step of the analysis was to apply loads 

and solve. Voltage loads were applied in these analyses. Voltage loads of 10 to 15 kV were 

applied to the metal lead, the wire bonds, and the metallized top surface of the die. The base 

plate was at zero potential with an applied voltage of 0 V. After the loads were applied, the 

solution was obtained. 

The final step of the analysis was to review results. The ANSYS finite element analysis program 

generated electric field plots of the various geometrical and material configurations. Figure 2 

shows the simulations results for the package shown in figure 1. In the simulations, package 

failure occurs if the critical field of the dielectric (air) is exceeded so that a high-field path exists 

between two conductors. Figure 2 shows that a high electric field (>3 MV/m for air) exists 

between the package lead and base plate. 

Figure 2. Electric field plot at the lead region of the standard package. 

Air - 3 MV/m 

Alumina 

Base plate 

0 0.5 1 1.5 2 2.5

Electric field (MV/m)

 3 4 3.5 

Base plate

 Ceramic Body

Lead 

Air 

SiC 

die 

Lead 
3 

In order to eliminate the continuous breakdown region, a new package was designed with the 

ceramic body extended beyond the base plate. Figures 3 and 4 show the geometry of the new 

high-voltage package design and the electric field plot, respectively. The extended body 

simulation of figure 4 shows that the continuous breakdown region has been eliminated. 

Figure 3. High-voltage package geometry. 

Figure 4. Electric field plot at the lead region of the high-voltage package. 

Although it was possible to design the lead region of the package for high-voltage operation in 

air, the same was not the case for inside the package cavity. Extensive finite element analysis 

was conducted, but it was discovered that the high-voltage package required encapsulants with 

significantly higher dielectric strengths than air to successfully operate at voltages of 10 to 

15 kV. The extent of potential termination from the edge of the die was also a crucial factor. 

Simulations were conducted with 0.2- and 0.5-mm termination spacing. Figure 5 shows the 

electric field near the silicon carbide die at an operating voltage of 15 kV. In this simulation, 

Fluorinert was used as an encapsulant and the potential was terminated 0.2 mm from the edge of 

the die. Figure 6 shows the electric field distribution under the same conditions as figure 5 

except that the potential is terminated 0.5 mm from the die edge. With Fluorinert’s electric field 

strength of approximately 15 MV/m, the simulation indicates that the potential on the die should 

be terminated greater than 0.2 mm from the edge to prevent breakdown at 15 kV. 

Alumina 

Air - 3 MV/m 

Base plate 

0 0.5 1 1.5 2 2.5 3 3.5 4

Electric field (MV/m)

Lead 

Lead 

Base plate 

Ceramic Body 

Air 

SiC 

die 
4 

Figure 5. Electric field plots showing the performance of Fluorinert under an applied voltage of 15 kV with 

surface potential terminated 0.2 mm from the edge of the die. 

Figure 6. Electric field plot showing the performance of Fluorinert under an applied voltage of 15 kV with 

surface potential terminated 0.5 mm from the edge of the die. 

Figure 7 shows the electric field near the silicon carbide at an applied voltage of 15 kV and with 

the epoxy encapsulant. The potential was terminated 0.2 mm from the edge of the die. Figure 8 

shows the electric field distribution under the same conditions as figure 7 except that the 

potential was terminated 0.5 mm from the die edge. With an electric field strength of 

approximately 22 MV/m, the result indicates that the epoxy provides for a reasonable dielectric 

breakdown margin at a termination spacing of 0.2 mm. 

0 2 4 6 8 10 12 14 16

0 2 4 6 8 10 12 14 16

Electric field (MV/m) 

Electric field (MV/m) 

Alumina 

Base plate 

Fluorinert 

SiC die 

Alumina Fluorinert 

Base plate 

SiC die 
5 

 

Figure 7. Electric field plot showing the performance of the epoxy under an applied voltage of 15 kV with 

surface potential terminated 0.2 mm away from the edge of the die. 

 

 

Figure 8. Electric field plot showing the performance of the epoxy under an applied voltage of 15 kV with 

surface potential terminated 0.5 mm away from the edge of the die. 

Figures 5 through 8 show that when the surface is terminated approximately 0.2 mm from the 

edge of the die at 15 kV, the epoxy alone can be successfully used as the encapsulant. Fluorinert 

will also be effective at this voltage if the termination is 0.5 mm or farther from the edge of the 

die. However, it was discovered from further analyses that materials that have considerably 

lower dielectric strengths than Fluorinert (e.g., SF6 at 9 MV/m) cannot be considered as 

encapsulants for this package at 15 kV. 

0 3 6 9 12 15 18 21 24

Electric field (MV/m) 

0 3 6 9 12 15 18 21 24

Electric field (MV/m) 

Alumina Epoxy 

Base plate 

SiC die 

Alumina Epoxy 

Base plate 

SiC die 
6 

The package was also simulated at 10 kV. Figure 9 shows the electric field near the silicon 

carbide die at an applied voltage of 10 kV. In this simulation, Fluorinert was used as an 

encapsulant and the potential was terminated 0.2 mm from the edge of the die. With Fluorinert’s 

electric field strength of approximately 15 MV/m, it provides for a reasonable dielectric 

breakdown margin at a termination spacing of 0.2 mm. 

 

Figure 9. Electric field plot showing the performance of Fluorinert under an applied voltage of 10 kV with 

surface potential terminated 0.2 mm from the edge of the die.

The performance of SF6 was also investigated at 10 kV. SF6 is one of the most popular 

insulating gases with a breakdown strength of about 3 times that of air. It is important to note 

that this gas is fairly inert at normal temperatures, but it presents hazards at elevated 

temperatures because it can decompose to form fluorine, which is highly reactive. Figure 10 

shows that at a termination spacing of 0.2 mm, SF6 is not able to protect against breakdown at 

10 kV. However, as seen in figure 11, it does provide a reasonable breakdown margin with a 

0.5-mm termination spacing. 

0 2 4 6 8 10 12 14 16 

Electric field (MV/m) 

Alumina Fluorinert 

SiC die 

Base plate 
7 

 

Figure 10. Electric field plot showing the performance of SF6 under an applied voltage of 10 kV with 

surface potential terminated 0.2 mm away from the edge of the die. 

 

Figure 11. Electric field plot showing the performance of SF6 under an applied voltage of 10 kV with 

surface potential terminated 0.5 mm away from the edge of the die. 

0 2 4 6 8 10

Electric field (MV/m) 

0 2 4 6 8 10

Electric field (MV/m) 

Alumina 

SF6

SiC die 

Base plate 

Alumina SF6

Base plate 

SiC die 
8 

3. Experimentation 

In order to validate the electrostatic finite element analysis, several standard ceramic packages 

were characterized for high voltage operation. The first ceramic package from Vendor A was 

rated at 2 kV. When the package was characterized under a curve tracer in the operating 

ambient, it failed at 1.5 kV. For this same package, ANSYS results indicate that breakdown will 

occur at approximately 1.8 kV. Figure 12 shows the ANSYS simulation for this particular 

package at 1.8 kV. The lead and cavity regions are shown on the same plot. 

Figure 12. Electric field plot of Vendor A package showing failure at 1.8 kV. 

A ceramic package from Vendor B was also characterized for high voltage operation. This 

package is a slightly different design from the Vendor B package, and the ceramic body is 5 

times thicker. The characterization of this package was conducted with a 10-kV power supply in 

a nitrogen atmosphere. The package failed at 7.8 kV because of arcing between the metal lead 

and the metallized backside surface of the ceramic ring as shown in figure 13. 

0 0.5 1 1.5 2 2.5 3 3.5 

Electric field (MV/m)

Base-plate

Alumina 

Air – 3 MV/m 

Air – 3 MV/m
9 

Figure 13. Photograph of Vendor B package showing 

where arcing occurred. 

ANSYS results show that dielectric breakdown will take place at around 8 kV, based on 

figure 14. Analysis error for this package is calculated to be 2.56 %. 

Figure 14. Electric field plot of the Vendor B package under 8-kV operation. 

0 0.5 1 1.5 2 2.5

Electric field (MV/m)

 34 3.5 

N2 – 3.45 MV/m 

N2 – 3.45 MV/m 

Alumina 

Base-plate 
10 

4. Summary 

In summary, we have used finite element, electrostatic modeling to design a ceramic package for 

the next generation of high voltage semiconductor components. This new package is designed to 

operate at 15 kV, which is more than 5 times higher than conventional ceramic package designs. 

Our results show that this package will perform successfully without arcing at the lead region 

and with proper encapsulation and potential termination at the edge of the die, critical electric 

fields are not exceeded within the die cavity. 
11 

Distribution List

Admnstr 

Defns Techl Info Ctr 

ATTN DTIC-OCP (Electrionic copy) 

8725 John J Kingman Rd Ste 0944 

FT Belvoir VA 22060-6218 

DARPA 

ATTN IXO S Welby 

3701 N Fairfax Dr 

Arlington VA 22203-1714 

Ofc of the Secy of Defns 

ATTN ODDRE (R&AT) 

The Pentagon 

Washington DC 20301-3080 

US Army TRADOC 

Battle Lab Integration & Techl Dirctrt 

ATTN ATCD-B 

10 Whistler Lane 

FT Monroe VA 23651-5850 

Dir for MANPRINT Ofc of the 

Deputy Chief of Staff for Prsnnl 

ATTN J Hiller 

The Pentagon Rm 2C733 

Washington DC 20301-0300 

US Military Acdmy 

Mathematical Sci Ctr of Excellence 

ATTN LTC T Rugenstein 

Thayer Hall Rm 226C 

West Point NY 10996-1786 

SMC/GPA 

2420 Vela Way Ste 1866 

El Segundo CA 90245-4659 

US Army ARDEC 

ATTN AMSTA-AR-TD 

Bldg 1 

Picatinny Arsenal NJ 07806-5000 

US Army Avn & Mis Cmnd 

ATTN AMSMI-RD W C McCorkle 

Redstone Arsenal AL 35898-5240 

US Army Info Sys Engrg Cmnd 

ATTN AMSEL-IE-TD F Jenia 

FT Huachuca AZ 85613-5300 

US Army Natick RDEC 

Acting Techl Dir 

ATTN SBCN-TP P Brandler 

Kansas Street Bldg78 

Natick MA 01760-5056 

US Army Simulation Train & 

Instrmntn Cmnd 

ATTN AMSTI-CG M Macedonia 

12350 Research Parkway 

Orlando FL 32826-3726 

US Army Tank-Automtv Cmnd RDEC 

ATTN AMSTA-TR J Chapin 

Warren MI 48397-5000 

Hicks & Assoc Inc 

ATTN G Singley III 

1710 Goodrich Dr Ste 1300 

McLean VA 22102 

Palisades Inst for Rsrch Svc Inc 

ATTN E Carr 

1745 Jefferson Davis Hwy Ste 500 

Arlington VA 22202-3402 
12 

Director 

US Army Rsrch Lab 

ATTN AMSRD-ARL-RO-D JCI Chang 

PO Box 12211 

Research Triangle Park NC 27709 

US Army Rsrch Lab 

ATTN AMSRD-ARL-D J M Miller 

ATTN AMSRD-ARL-CI-IS Mail & Records Mgmt 

ATTN AMSRD-ARL-CI-OK-T Techl Pub (2 copies) 

ATTN AMSRD-ARL-CI-OK-TL Techl Lib (2 copies) 

ATTN AMSRD-ARL-SE-DP D Ibitayo 

ATTN AMSRD-ARL-SE-DP W Tipton 

Adelphi MD 20783-1197