In this paper the key property differences between solders and TLPS interconnect technologies are compared in detail for MLCC interconnects. The development of a new range of nickel Base Metal Electrode C0G MLCC stacks rated for 200oC is described and performance compared to traditional Precious Metal Electrode (PME) stacks. Thermal cycling performance to 200oC of BME X7R stacks made with 10Sn/88Pb/2Ag solders are compared to similar stacks made with TLPS interconnects of Cu-Sn and In-Ag. The development of leadless stacks, a new bulk capacitance form factor enabled by TLPS technology, is described and their properties compared to traditional stacks.

1. 1
John Bultitude, Lonnie Jones, John McConnell, Galen
Miller, Jim Magee, Allen Templeton, Abhijit Gurav and
Reggie Phillips
KEMET Electronics Corporation
2835 Kemet Way
Simpsonville, SC 29681
USA
A Comparison Between Solders & Transient
Liquid Phase Sintered Interconnects in High
Temperature Multi-Layer Ceramic Capacitors

2. 2
Outline
• Introduction
– High Temperature Electronics Trends
• High Temperature Capacitor Types
– 200oC ratings
– Compare Class I and II stacks
• Solder Interconnect Materials
– Shear Stress & Temperature Cycling Robustness
• Alternative Interconnect Materials
– Cost effective for MLCC, Pb-free with high temperature capability
• Transient Liquid Phase Sintering (TLPS) Development
– CuSn & InAg systems
• Leadless Packaging
• Summary
• Future Work

3. 3
High Temperature Electronics Trends
Deeper Downhole Wells
• Shell Oil Cheap & Deep [1]
WBG Semiconductors
• Improve Power Conversion Efficiency [3]
Power
Conversion
Si Based
WBG Based on GaN
or SiC
DC to DC 85% 95%
AC to DC 85% 90%
DC to AC 96% 99%
• Higher Junction Temperatures,
Switching Frequencies & Voltages
• Future Power Electronics [4]
• Ultra High Pressure High
Temperature [2]

4. 4
High Temperature Electronics Trends
• WBG for Power Efficiency – Mainstream High Temp Electronics
• Ultra High Pressure High Temperature Wells in Downhole
• WBG for Power Efficiency – Mainstream High Temp Electronics
• Ultra High Pressure High Temperature Wells in Downhole

5. 5
High Temperature Capacitor Types
• 200oC Catalog Offerings [6]
• Voltage Rating @ 200oC
• MLCC for ≥ 100VDC
• MLCC Nameplate Capacitance 1Vac, 1kHz, 25oC
– Class II X-type Vs. Class I C0G Stacked MLCC
• 200oC Catalog Offerings [6]
• Voltage Rating @ 200oC
• MLCC for ≥ 100VDC
• MLCC Nameplate Capacitance 1Vac, 1kHz, 25oC
– Class II X-type Vs. Class I C0G Stacked MLCC
Capacitor Type 10VDC 100VDC 1000VDC
Wet Tantalum 1000µF Not Available Not Available
Solid Tantalum 33µF Not Available Not Available
Silicon Capacitor 3.3µF Not Available Not Available
Stacked MLCC 340µF 120µF 2.8µF
Leaded MLCC 10µF 10µF 2.2µF
Surface Mount MLCC 18µF 12µF 0.22µF

6. 6
High Temperature Capacitor Types
Class II X-Type Vs. Class I Ni BME C0G Stacks
KEMET Class I
Ni BME C0G
0.15µF 500VDC
Competitor Class II
X-Type
0.27µF 500VDC
• At 500VDC capacitance is the same at 25oC
• Class II has 30% Lower capacitance at 200oC
• At 500VDC capacitance is the same at 25oC
• Class II has 30% Lower capacitance at 200oC

7. 7
High Temperature Capacitor Types
Class II X-Type Vs. Class I Ni BME C0G Stacks
Power Dissipation
P = I 2 R
Where P = Power Dissipated (W)
I = Current Applied (ARMS)
R = ESR (Ω)
Dielectric
Stack
Rating
Frequency 10kHz 50kHz 100kHz 200kHz 500kHz
ESR 740 mΩ 190 mΩ 110 mΩ 60 mΩ 30 mΩ
Power
Dissipation
@ 3Arms
6.66 W 1.71 W 0.99 W 0.54 W 0.27 W
ESR <10 mΩ <2 mΩ ~1 mΩ <1 mΩ ~2 mΩ
Power
Dissipation
@ 3Arms
0.09 W 0.018 W 0.009 W 0.009 W 0.018 W
ESR/Power Dissipation vs Frequency
Class II
X-type
0.27µF
500V
Class I
C0G Ni
BME
0.15µF
500V

8. 8
Solder Interconnect Materials
Max Shear Stress & MPt. Capability of Common Solders [7]
• Low Shear of Pb-free solder ≥ 200oC
• HMP Pb-solders used > 200oC
• Low Shear of Pb-free solder ≥ 200oC
• HMP Pb-solders used > 200oC
Solder
Melting Temp,
o
C
80% of Melting
Temp, o
C
10Sn/88Pb/2Ag 290 232
93.5Pb/5Sn/1.5Ag 305 244
91.5Sn/8.5Sb 240 192
SAC 305
95.5Sn/3Cu/0.5Ag
217 174

9. 9
Solder Interconnect Materials
Accelerated Temperature Cycling 10Sn/88Pb/2Ag solder interconnects
• Solder Fatigue causes peripheral lead detachment
reducing shear stress capability
• Solder Fatigue causes peripheral lead detachment
reducing shear stress capability

10. 10
Solder Interconnect Materials
Stack with 10Sn/88Pb/2Ag solder interconnects
MCC Capacitance
Rated
Voltage
Length
(inch)
Width
(inch)
Height
(inch)
Temp.
Cycling
Life Test @
200o
C
1000hrs
1.5µF 100V 0.25 0.25 0.61 0/12 0/29
75nF 1000V 0.25 0.25 0.61 0/12 0/36
1.7µF 200V 0.40 0.40 0.61 0/12 0/35
0.27µF 1000V 0.40 0.40 0.61 0/12 0/24
1.8µF 500V 0.45 1.01 0.61 0/12 0/89
1.2µF 630V 0.45 1.01 0.61 0/12 0/35
0.72uF 1000V 0.45 1.01 0.61 0/12 0/36
0.18uF 2000V 0.45 1.01 0.61 0/12 0/30
5
4
3
• 314,000 life test hours (35.8 years) at 200oC No Failures …..but
• > 85% Pb-Solders face withdrawal from exemption by EU RoHS 2 by 2021 and are
already prohibited from Automotive & Commercial Applications
• 314,000 life test hours (35.8 years) at 200oC No Failures …..but
• > 85% Pb-Solders face withdrawal from exemption by EU RoHS 2 by 2021 and are
already prohibited from Automotive & Commercial Applications

11. 11
Alternative Interconnect Materials
Analysis of Attributes
Material Cost Process Cost
Process
Flexibility
Process
Temperature
Temperature
Limit
Target Low Low High Low High
HMP Pb‐solders Low Low High Low Moderate
Pb‐free solders Low Low High Low Low
Conductive Epoxy Moderate Low Moderate Low Low
Gold solders High Moderate Moderate High High
Nano‐silver High High Moderate Low High
Nano‐copper High High Moderate Low High
Sintered Silver Moderate Moderate Moderate Low High
InAg TLPS Moderate Moderate Moderate Low High
CuSn TLPS Low Low High Low High
Attributes
Interconnect
Materials

12. 12
Alternative Interconnect Materials
Shear Stress CuSn TLPS, Sintered Ag & 10Sn/88Pb/10Ag Solder
• Sintered Silver bond has low shear high elongation like an adhesive
• CuSn TLPS has similar behavior to solder
• Sintered Silver bond has low shear high elongation like an adhesive
• CuSn TLPS has similar behavior to solder

13. 13
What is TLPS?
– Low temperature reaction of
low melting point metal or alloy
with a high melting point metal
or alloy to form a reacted metal
matrix or alloy
– Forms a metallurgical bond
between 2 surfaces
Transient Liquid Phase Sintering (TLPS)
Basic Technology & Types [6]
CuSn TLPS
Heat
InAg TLPS

14. 14
Single Metal Paste Diffusion (SMPD) Process
In-Ag [6]
Ag Lead
Ag MLCC
Indium
Paste
Initial Bond Formation
• Low Pressure
• 250-350oC/30seconds
• N2 atmosphere
Ag Lead
Ag MLCC
In
Ag
Ag
InAg
Diffusion
• 200-300oC
• N2 atmosphere
Low Ag 500X
High Ag 1000X
Low Ag
500X
48hrs
200oC
High Ag
1000X
120hrs
200oC

15. 15
Transient Liquid Phase Sintering (TLPS)
Shear Energy Vs. Temperature [11]
• TLPS has higher shear energy at 200oC that is retained ≥ 250oC• TLPS has higher shear energy at 200oC that is retained ≥ 250oC

16. 16
Transient Liquid Phase Sintering (TLPS)
Temperature Cycling of Leaded Stacks
In-Ag TLPS Bonded Case Size
2220 Ni BME C0G on J-Lead [11]
250 500 750 1000
Ag over Cu plate 0/30 0/30 0/30 0/30
Ag over Ni plate 0/30 0/30 0/30 0/30
MLCC Termination
# Temperature Cycles ‐40 to +200o
C
TLPS Bonded Case Size 1812 (12)
Ni BME X7R 40µF 25V 175oC stack
Lead Frame Chip Finish CuSn InAg Chip Finish 10/88/2
Tin 3/6
Copper 4/4
Gold
Silver 4/4 4/4
Tin 0/4
Copper 0/4
Gold 0/4
Silver 0/4 0/6
Interconnect TLPS Solder
Phosphor
Bronze
Alloy 42
high‐Pb hot
solder dip
0/6
Temperature Cycling -55 to 200oC
CTE = 17.8 PPM/oC
CTE = 4.5 PPM/oC

17. Leadless Stacks
3640 0.22µF 500V MLCC [13]
CuSn
TLPS
Termination
Circuit Board/ Package
Solder
Ni/Thin Au

18. Leadless Stacks
Board Flexure
10987654321
90
80
70
60
50
40
30
20
10
Board Flexure, mm
Percent
3
MLCC
2 Chip
4 Chip
Variable
Board Flexure
3640 MLCC and 2 and 4 Chip Leadless Stacks
Weibull
Tested
Pieces to
10mm DID
NOT FAIL
• Leadless Board Flexure similar to MLCC• Leadless Board Flexure similar to MLCC

19. 1000 hrs storage @ 200C1000 Temp. Cycles -55 to 150CInitial
60
50
40
30
20
10
0
Sample (n=10)
ShearStress(MPa)
38.939.8
35.8
Shear Stress @ 25C of 3640 2 Chip 3640 Leadless Stacks
Leadless Stacks
Shear Stress @ 25oC
• 19.1MPa failure at 27.9kg > 15 x Higher than 1.8kg minimum AEC Q200• 19.1MPa failure at 27.9kg > 15 x Higher than 1.8kg minimum AEC Q200

20. Summary
• Deeper Wells need higher temperature electronics
• WBG semiconductors (SiC) need high temperature capacitors
• Leaded and stacked MLCC have the highest capacitance values
available rated with 200oC ≥ 100VDC.
• Class I Ni BME C0G at 500VDC can have higher capacitance at
200oC and low power dissipation over a broad frequency range
• HMP Pb-solders interconnects currently used are reliable but are
disallowed in some applications with future withdrawal of EU
RoHS 2 exemptions under consideration
• TLPS materials of CuSn and InAg are viable alternatives to HMP
Pb-solders
• Leadless Stacks, a new form factor, have been developed using
TLPS materials

21. Future Work
• TLPS technology scale-up to
– Replace Pb-solders in MLCC interconnects
– Leadless Stacks form factors
• Capacitor solutions for mainstream high temperature
electronics ≥ 150oC

22. Thank You!