IMAPS - 2009 Mohammad Chowdhury

Understanding Micro Via Fabrication Understanding Micro Via Fabrication by Mechanical Punching in Liquid by Mechanical Punching in Liquid

Crystal Polymer (LCP) Substrate for Crystal Polymer (LCP) Substrate for RF-MEMS and Related Electronic RF-MEMS and Related Electronic

Packaging ApplicationsPackaging Applications

Mohammad K. Chowdhury,1 Li Sun,2 Shawn Cunningham,2 and Ajay P. Malshe1*

1University of Arkansas, Fayetteville, AR 727012WiSpry Inc., Irvine, CA 92618

*Contact E-mail: [email protected]

IMAPS 2009November 3rd, 2009

mailto:[email protected]

Outline:

Motivations and Applications

Different Substrate Materials and Fabrication Techniques

μ-via fabrication by Mechanical punching

Results and Discussion

Conclusion and Future works

Tuesday, November 03, 2009 2

IMAPS 2009, San Jose McEnery Convention Center

Need for a cost effective way of micro through via fabrication technique

Need for high speed processing technique for through via fabrication with high yield throughput

Need for through via fabrication technique compatible with the conventional via fabrication tool

Need for elimination of thermo processing of the substrate during through via fabrication

Need for fabrication of vias with uniform through via wall

Motivations:



Driver Applications:

www.morgantechnicalceramics.com

www.smalltimes.com www.ec.europa.eu – ANASTASIA Project

Transreceiver Base Station for

Cell Phone



Outline:








Different Material Candidates for the Substrate:

LCP - ULTRALAM 3850 [1]

LTCC - DuPont 951 Green Tape [2]

Kapton - Dupont HN100 [3]

Peel Strength ( lbs/in) 8.52 12 7.2

Tensile strength ( MPa) 200 320 231

Tensile Modulus(GPa) 2.255 120 2.0

Density ( g/cm3) 1.4 3.1 1.42

CTE ( ppm/°C)17 (X & Y axis)

150 (Z-axis)5.8 20

Melting Temp. (°C) 335 738 360

Thermal Conductivity ( W/m/°K) 0.2 3.3 1.09

Dielectric Constant @ 10 GHz, 23°C 2.9 7.1 3.5

Dissipation Factor/Loss Tangent @ 10 GHz, 23°C

0.0025 0.005 0.002

Volume Resistivity ( Mohm) 1x1012 1x1014 1x1017

Dielectric Breakdown Strength (V/mil)

3500 1000 5200

Chemical Resistance 98.7% - 95%

Water Absorption (23°C, 24 hrs) 0.04% - 2.8%



Different Techniques for µ-Via Fabrication :Via Diameter, Substrate

MaterialVia

PitchVia Shape in Z-axis

Aspect Ratio

Damage to Substrate

Speed Cost/Via

Mechanical Punching

30µm, Mylar [8] - UniformLow - 3:1

[8]

Relatively Smooth Surface of the Via

WallHigh

Very Low [11]

Mechanical Drilling

100µm, PCB [6]50µm

[6]Almost Uniform

LowVery Rough

Surface of the Via Wall

Slow Low [11]

Laser Drilling (CO2, YAG,

YVO4 Excimer)

25 to 75 µm, Polyimide - CO2, [4]

10 to 15 µm, Ceramics, PVA, Polystyrene, & Pyrex

Glass - YAG –[5]25µm, LCP - YVO4, [7]

-Very

Uniform [8, 12]

Very High -

20:1 [13]

Carbon Residue Leftover [12]

Smooth Surface of the Via Wall

[13]

Slow Low [4]

Plasma Etching

50 µm, Kepton [10] -Very

UniformHigh

Very Smooth Surface of the Via

Wall

Very Slow

Expensive

E-beam Machining

65 µm, Green Tape [9]200

µm [9]

Very Uniform

[9]High [9]

Very Smooth Surface of the Via

Wall [9]

Very Slow

Extremely Expensive



Outline:








Via Fabrication – Test Structure:Current Industry (wiSpry) Requirements:

No. of MEMS Switches: 80No. of I/O’s: 56Via Diameter: 90 μmVia Pitch:

300 μm (X-axis)330 μm (Y-axis)

Via Size

Via Pitch (μm)

50 μm 75 100 125 150

75 μm 112.5 137.5 162.5 187.5

100 μm

150 175 200 225

Targeted for Experiments:



How The Punching System Works?

Die Bushing

LCP

Copper

Copper

Pin

LCP

Copper

Copper

Before Punching

Copper

Copper

LCP

After Punching

Copper

Copper

LCP

APS 8718 Automatic Punching SystemPacific Trinetics Corporation

6” x 6” Sample Holder

Punch Pin Holder & Die

Bushing



Outline:





Conclusion and Future work



Mechanical Punching of μ-Via50 µm Via, 75 µm Pitch, 10 x 10 Array

50 µm

20 μm

20 μm

LCP Burr

Consistency of the Via Array Uniformity of Via Size and Shape

Top Cu

Film



Punching Directions:



Challenges in Mechanical Punching

50 µm Via, 75 µm Pitch, 10 x 10

Array

Expansion

Warpage1. Z-axis Expansion of

the LCP Film2. Warpage of the LCP

sample3. LCP Burr4. Copper Burr

LCP Burr

Copper Burr

Bottom Cu Film

Bottom Cu Film



a)

Via Pitch

Via Diameter

b)

Via Diameter

Via Pitch

d) c)

Mechanism of LCP film Z-axis Expansion :



Pitch Dependency of the Z-axis Expansion of LCP

Z-axis expansion of the LCP film increases with lower pitch



Via Size

Via Pitch (μm)

50 μm

75 100 125 150

75 μm

112.5

137.5

162.5

187.5

100 μm

150 175 200 225

Areal Density Dependency of the Z-axis Expansion of LCP

Z-axis expansion of the LCP film increase with higher via arrayTuesday, November 03, 2009 17


Via Size

Via Pitch (μm)

50 μm

75 100 125 150

75 μm

112.5

137.5

162.5

187.5

100 μm

150 175 200 225

Pitch Dependency of the Radius of Curvature

Radius of curvature of the LCP film decrease with lower pitch, i.e., high warpage with lower pitch



Via Size

Via Pitch (μm)

50 μm

75 100 125 150

75 μm

112.5

137.5

162.5

187.5

100 μm

150 175 200 225

Areal Density Dependency of the Radius of Curvature

Radius of curvature of the LCP film decreases with smaller via array, i.e., high warpage with smaller via array



Does μ-Mechanical Punching Has Any Prospect?Current Industry (wiSpry) Requirements:

No. of MEMS Switches: 80No. of I/O’s: 56Via Diameter: 90 μmVia Pitch:

300 μm (X-axis)330 μm (Y-axis)

Via Size

Via Pitch (μm)

50 μm 75 100 125 150

75 μm 112.5 137.5 162.5 187.5

100 μm

150 175 200 225

Targeted for Experiments:



Outline:








Conclusion: μ-vias with 50 µm diameter and 75 µm pitch has been demonstrated Mechanical punching for μ-via fabrication results Z- axis expansion of the LCP film and substrate warpage Lower pitch will results higher Z-axis expansion of the LCP film, which reduced along with higher pitch Higher areal density will results more Z-axis

expansion of the LCP film Smaller pitch will have higher substrate warpage, which reduced with higher pitch Lower areal density will have higher substrate warpage, which reduced with higher via arrayTuesday, November 03,

2009 22IMAPS 2009, San Jose McEnery Convention

Center

Future Direction:

Cleaning of LCP burr and Copper burr

Electroplating of the vias

Electrical characterization of the vias

Lamination of multilayered structure

Electrical Characterization of the laminated structure

Reliability analysis of the laminated structure



Acknowledgements: Advisor & Dissertation Committee

Members at the University of Arkansas

The National Science Foundation

wiSpry Inc., Irvine, CA

High Density Electronics Center (HiDEC) Staff and Facility

MMR Lab Colleagues

Rogers Corporation

IMAPS 2009

[1] MSDS, ULTRALAM® 3000 - Liquid Crystalline Polymer Circuit Material, Rogers Corporation, Arizona, USA[2] Low Temperature Cofire Dielectric Tape Technical information, 951 Green TapeTM, DuPont Microcircuit Materials[3] Summary of Properties for Kapton® Polyimide Film, DuPont Microcircuit Materials[4] Jim Morrison, Ted Tessier, and Bo Gu, “A Large Format Modified TEA CO2 Laser Based Process for Cost Effective Small via Generation,” MCM Proceedings, pp 369-377, 94[5] Vijay V. Kancharla, Kira K. Hendricks, and Shaochen Chen, “Micromachining of packaging materials for MEMS using laser” Micromachining and Microfabrication Process Technology VII, Proceeding of SPIE, Vol. 4557, pp 220-224, 2001[6] Brian J. McDermott, and Sid Ttyzbiak, “Practical application of photo-defined micro-via technology,” 3rd International Symposium on Advanced Packaging Material, pp 24-28, 1997[7] Mingwei Li, Hix Ken, Dosser Larry, Hartke Kevin, and Blackshire Jim, “Micromachining of Liquid Crystal Polymer film with Frequency converted diode-pumped Nd: YVO4 Laser” Photon Processing in Microelectronics and Photonics II, Proceeding of SPIE, Vol. 4977, 2003[8] Gunter Hagen, and Lars Rebenklau, “Fabrication of smallest vias in LTCC tape,” Electronics Systemintegrations Technology Conference, Dresden, Germany, pp 642-647, 2006[9] M.A. Sarfaraz, C. Long, and You-Wen Yau, “Enhanced MCM-C Packaged Performance by Formation of improved 3-D interconnections,” Electronic Components and Technology Conference, Proceedings, pp 1067-1071, 1993[10] James Keating, and Robert Larmouth, “Microvias and Flex – An enabling MCM-L Technology,” International Conference on Multichip Modules and High Density Packaging, pp 342 -384, 1998[11] T. G. Tessier, and Bill Adams, “Mechanical Punching of Through-Holes in Thin Laminates for Higher Density MCM-L Fabrication” MCM Proceedings, pp 173-181, 1994[12] Dane Thompson, “Characterization and Design of Liquid Crystal Polymer (LCP) Based Multilayer RF Components and Packages” PhD dissertation 2006, Georgia Tech. [13] T. M. Yue, and K.C. Chan, “Laser Drilling of Liquid Crystal Polymer Composites” Polymer Composites, Vol.19, No.1, 1998

References:



Thank You !

Questions, Comments & Suggestions

Chemical Etching of LCP & Cu Burr

LCP Burr

Copper Burr

Before LCP Burr

Before

Copper Burr

After After

Process Recipe

Micro Pits

Successful etching of loosely bonded LCP and copper burr using the recipe

A

B

C

Mechanically Punched Micro Vias

DI Water Sonication



Plasma Cleaning of LCP Residual Removal Before O2 Plasma

Cleaning LCP Burr

Copper Etched Out After O2 Plasma

Cleaning

Before O2 Plasma Cleaning

After O2 Plasma Cleaning



30 Minute O2 Plasma Cleaning After Chemical Etching

LCP and copper burr can be removed very efficiently by chemical etching and oxygen plasma cleaning afterwordTuesday, November 03, 2009 29


Via Metallization: DC Vs Reverse Pulse Plating (RPP)

DC Plating

Reverse Pulse Plating

Via metallization can be done very efficiently by DC plating as compared to reverse pulse plating in 4.5 Hrs



IMAPS - 2009 Mohammad Chowdhury

Technology

Transcript of IMAPS - 2009 Mohammad Chowdhury