Flip Chip Technology

Flip Chip TechnologyFlip Chip Technology MMDCLDCL EE SNUEE SNU

Flip Chip TechnologyFlip Chip Technology

2005/6/16

Kim Dong Hwan

School of Electrical Engineering and School of Electrical Engineering and Computer ScienceComputer Science

Seoul National University, KoreaSeoul National University, Korea

Microwave Device Term Microwave Device Term ProjectProject


ContentsContents

• Introduction

• Wire Bonding vs. Flip Chip interconnect

• Flip Chip Process (SSB & MSB)

• Conclusion


IntroductionIntroduction• Advancements in the packaging of semiconductor devicesAdvancements in the packaging of semiconductor devices

traditionally use wire bondswire bonds to provide the interconnect from device to substrate or to other devices

• Along with the rapid advances in microwave and millimeter Along with the rapid advances in microwave and millimeter wave subsystem developmentwave subsystem development

a growing interest concerning chip interconnection techniques has developed.

• The importance of quality of these interconnectsThe importance of quality of these interconnects

a large impact on the performance of the entire subsystem, especially at high frequencies.

• Flip chip offers advantages over traditional interconnect Flip chip offers advantages over traditional interconnect schemes.schemes.

A smaller overall footprints, better thermal heat transfer


• Introduction



• Conclusion


Wire BondingWire Bonding

Bond ribbon

Wire Wire length length

lossloss

[Coplanar Waveguide Model]


Flip Chip Flip Chip InterconnectionInterconnection

[Gold(Stud) Bumps attached]

[Flip Chip Interconnection of Coplanar MMIC][EM-Simulation Structure for RF test]

MMIC(2mm 50 CPW line)

Motherboard on 20-cm Si w

afer

Bump

CPW SmallSmall

BigBig

Compared to the Bond Wire

0 20 40 60 80 100-40

-30

-20

-10

0

-15

-10

-5

0

Tra

ns

mis

sio

n L

os

s [

dB

]

Re

turn

Lo

ss

[d

B]

Freq [GHz]

Measured Simulated

Ref.Ref. Songsub Song



Bump Height Bump Height ≥≥ Spacing Spacing

☞ The influence of substrate surface -> negligible

{Bump height ≥ Ground to ground spacing of the transmission lines}



Return lossReturn loss

Insertion loss

Beyond 100GHz → Below 0.5dB

Flip Chip InterconnectionFlip Chip Interconnection Wire BondingWire BondingVersus


Proximity Effect in Flip-Chip Proximity Effect in Flip-Chip StructureStructure

[ E-field distribution for a flip-chip

mounted CPW MMIC ]

D

Motherboard

MMIC or Device

[ E-field distribution for a flip-chip

mounted CPW MMIC ]

D

Motherboard

MMIC or Device

Height of flip-chip bump (air-gap)

[ Change rate of characteristic impedance as a function of air-gap for a flip-chip mounted CPW MMIC ]

Air gap (m)C

han

ge

in

Z0

(

% )

50 CPW (D= 80m)

Alumina substrate

~ 3 % change at 20 m

Ref. Sangsub Song, “The Flip-Chip Mounted MMIC Technology using the Modified MCM-D Substrate for Compact and Low-Cost W-band Transceivers”


Why Flip Chip Why Flip Chip Technology?Technology?

~ 650 m

[ Flip-Chip Bonding Technology ][ Wire-Bonding Technology ]

-strip MMIC

Wire -Bonding

50 ~ 100 m

Via

CPW MMIC

Ground

Flip-Chip Bump

Advantages of Flip Chip Bonging Technology. Short Interconnection Length Better Electrical Performances

High reproducibility High Yield & Less Tuning

Compact size High Packaging density

Passive components are made in dielectric substrate such as alumina

Ceramics, SiO2 and BCB Low Cost


ComparisonComparison

Flip Chip Technology

Wire Bonding

Technology

Advantages

• High density• High performance• Noise control• Thin profile • Area array technology• Small device foot prints• Self alignment

• Mature Technology• Infrastructure exists• Flexible for new devices• Flexible for new bonding patterns

Disadvantages

• Additional Equipment• Additional processes• Rework after encapsulation is difficult• Die shrink

• Additional Equipment• Additional processes• Rework is difficult• I/O limitation


• Introduction



• Conclusion


SStud tud BBump ump BBonding onding TechnologyTechnology

[Process flow of the SBB]

[Cross-sectional SEM photograph of the bonding portion by SBB]


MMicro icro BBump ump BBonding onding TechnologyTechnology

[Process flow of the MBB]

[Cross-sectional SEM photograph of the bonding portion by MBB]

-To cure the resin

☞ Further requirements for miniaturization and higher frequency operation


ConclusionConclusion• The need for smaller packagingThe need for smaller packaging

– Flip chip interconnect process → more compact fashion

• Improved electrical performanceImproved electrical performance– Reduced interconnect length → lower inductance and reduced signal loss

→ lower power requirements

• The demands of high frequency applications– Limitation of the wire interconnect → flip-chip bump connection

[Flip Chip Bump Connection][Wire connection]


References[1] Mark S. Hauhe, “Flip Chip Technology Vendor Overview,”[2] R. Sturdivant, “Reducing the effects of the mounting substrate on the perform

ance of GaAs MMIC flip chips,” in Proc. 1995 Int. Microwave Theory Tech. Symp. Dig., Orlando, FL, May 1995, pp. 1591-1594.

[3] Hideki Kusamitsu, et al., “The Flip-Chip Bump Interconnection for Millimeter Wave GaAs MMIC,” IEEE Transactions on Electronics Packaging Manufact- uring, VOL. 22, NO .1, January 1999.

[4] T. Krems, et al., “Millimeter-Wave Performance of Chip Interconnections Using Wire Bonding and Flip Chip,” IEEE MTT-S Digest. pp. 247-250.

[5] Hiroyuki Sakai., “High Frequency Flip-Chip Bonding Technologies and Their Application to Microwave/Millimeter-wave ICs,” IEICE TRANS. Electron., VOL. E81-C, NO. 6 June 1998.

[6] Kiyomitsu Onodera, et al., “Novel Flip-Chip Bonding Technology for W-Band Interconnections Using Alternate Lead-Free Solder Bumps,” IEEE Microwave and Wireless Components Letters, VOL.12, NO. 10, October 2002.

[7] Sangsub Song, “The Flip-Chip Mounted MMIC Technology using the Modified MCM-D Substrate for Compact and Low-Cost W-band Transceivers” IEEE IMS 2005. Microwave Application Seminars.


Thank you !Thank you !

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Flip Chip Technology