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Parylene Technology for Electronics

Rakesh Kumar, Ph. D.Vice President of Technology

CTEA (Central Texas Electronics Association) Electronics Design & Manufacturing Symposium Tuesday, February 5, 2013

CTEA (Central Texas Electronics Association), Electronics Design & Manufacturing Symposium , Tuesday, February 5, 2013

OutlineParylene Technology for Electronics

• Packaging Challenges

• Advancement in Parylene

• Characterization & Qualifications

• Practical Issues

• Conclusion


SCS is the direct descendant of Union Carbide Corporation– Unbroken transfer of technology and Intellectual Properties

– Over 40 years of Parylene applications experience

SCS manufactures its dimer to ensure high quality and formulation

SCS - the global leader in Parylene coating solutions– Parylene variants, coating center locations, process development,

coating technologies, equipment design and manufacture, regulatory support

• 11 worldwide coating centers– Americas: Costa Rica and United States (5)

– Asia: Japan and Singapore

– Europe: Czech Republic, Ireland and United Kingdom

Specialty Coating Systems


ISO & AS 9100 Registration


Challenges in Electronics

• Smaller, 2D-3D forms

• Protection from moisture and other contamination

• Higher operating temperatures

• Higher frequency operations

• Improved processing methods

• Product differentiation (via improved engineering)

• Reliability of components in corrosive/harsh environments

• Controlling degradation due to time, physical and chemical attack

• Industry and government regulatory compliance


• Increasing package performance, functionality and reliability (e.g. smaller pitch is accompanied by smaller solder balls, which can affect structural integrity)

• Miniaturization, e.g. MEMS, NEMS & other devices

• Reducing stress and increasing reliability, such as underfill, in board-level assemblies and stress-absorbing layers and bump structures

• Achieving required mechanical tolerances for aligning chips to small pads

• Assembling or placing single and multi-die stacks

• Addressing the issues of stiction, e.g. MEMS

• Reducing interconnect fatigue

• Making reliable contact to the bond pads

Wafer Level PackagingProtection and Reliability Challenges


• Electromigration/short circuit

• Drift of component parameters

• Transient electrical stresses/ failure/ electronic charge induced damage

• Environmental damage to electronics –atmospheric contamination and moisture

• Excessive heat/high temperature failure

• Electromagnetic interference (EMI)

• Mechanical failures

• Corrosion in electronics

• Packaging stresses

Sensitive & Power Electronics Reliability Issues


• Completely conformal

• Unique, vapor-deposited, high-performance polymer coating

• Unique combination of performance, protection & durability characteristics

• Suited for complex situations where a durable coating solution is required

• “Green” material and application process

Why Parylene Conformal Coating ?

Parylene Coating Liquid Coating

• Able to coat a variety of substrates• Uniform, no pooling/voids• Stress free application• Low dielectric constant

• Optical clarity/transparency• Excellent electrical insulation• Excellent chemical and moisture barrier• High dry-film lubricity

• Environmentally safe• Extremely thin• Pinhole and defect free• Biostable and biocompatible

Advantages of Parylene


Advances in Parylene

F2C CF2____

n

Parylene HT®

High Temperature Fluorinated Parylene

H2C CH2____

n

H2C CH2

Cl

____n

H2C CH2

Cl

Cl

____n

Parylene N

Parylene C

Parylene D


Advances in Parylene


Parylene C; As depositedE.E. Hui, UC Berkeley

Parylene CharacteristicsTruly Conformal

0.001” (1 mil) gold wire with a 1.5m Parylene C coating

Liquid Coating

Parylene Coating

Parylene C on MEMS


Thermal CharacteristicsR

elat

ive

sam

ple

wei

ght [

%]

Atmosphere: Air

Heating rate: 10 C/min

Temperature [°C]

T 5% = 535 °C

0 100 200 300 400 500 600 700 800 90020

30

40

50

60

70

80

90

100

110

Temperature [°C]

Rel

ativ

e sa

mpl

e w

eigh

t [%

]

Atmosphere: Nitrogen

Heating rate: 10 C/min

T 5% = 539 °C

Parylene HT

0 100 200 300 400 500 600 700 800 900

0

20

40

60

80

100

Parylene HT


Thermal AgingParylene HT

Dielectric and Tensile Strength

1000

3500

6000

8500

control 250C-24h

250C-168h

250C-500h

250C-1000h

350C-24h

350C-168h

350C-500h

350C-1000h

400C-24h

Temperature and Time

Diel

ectri

c St

reng

th

(vol

ts/m

il)

1000

4000

7000

10000

13000

Tens

ile S

treng

th (p

si)

Dielectric StrengthTensile Strength

1000

3500

6000

8500

control 450C-30m 450C-60m 450C-180m 500C-0m 532C-0m


Diel

ectri

c St

reng

th

(vol

ts/m

il)

1000

4000

7000

10000

13000

Tens

ile S

treng

th (p

si)

Dielectric StrengthTensile Strength

Long-term

Short-term


Thermal AgingParylene HT

Water Vapor Transmission Rate (WVTR) and Modulus

0

0.2

0.4

0.6

0.8

Control 250C-24h

250C-168h

250C-500h

250C-1000h

350C-24h

350C-168h

350C-500h

350C-1000h

400C-24h


WVT

R cc

/(100

in2-

day)

100000

200000

300000

400000

500000

Mod

ulus

(psi

)

WVTR Modulus

0

0.2

0.4

0.6

0.8

Control 450C-30m 450C-60m 450C-180m 500C-0m 532C-0m


WVT

R in

cc/

(100

in2-

day)

100000

200000

300000

400000

500000

Mod

ulus

(psi

)

WVTRModulus

Long-term

Short-term


Thermal Shock

• Tested in accordance with Mil-STD 202, Method 107, test condition B. • After completion of the temperature cycling, the specimens were conditioned

at 25oC and 50%RH for 24 hours before appearance and dielectric withstanding voltage.

Thermal Shock Test Condition B (5 cycles )

Step Exposure condition Exposure time1 - 65 oC, +0, -5 30 min dwell

2 25 oC, +10, -5 5 min max

3 125 oC, +3, -0 30 min dwell

4 25 oC, +10, -5 5 min max

Results 1. Appearance compared to control sample at 10X: Passed

The coating was free from bubbles, pinholes, whitish spots, blistering, wrinkling, cracking and peeling.

2. Dielectric Withstanding Voltage: PassedApplied voltage : 1500 VAC rms for 60 seconds, leakage current : 1.02 to 1.04 µA

Parylene Types Tested

Parylene N

Parylene C

Parylene HT


Moisture Resistance -Insulation Resistance

Insulation ResistanceParylene HT Mil Requirement

Insulation Resistance 1.7 x 1013 > 2.5 x 1012 (Ohms )Test Method

Tested in accordance with Mil-STD 202, Method 302, test condition B (Temp: 230C, RH: 45%). Insulation resistance measured were taken using a megohms bridge at 500 volts DC, with an electrification time of one minute.

Tested in accordance with Mil-STD 202, Method 302, test condition B (Temp: 650C, RH: 90-96%)


UV Stability

Parylene films were exposed to radiation from a bank of fluorescent lamps using the following parameters:

- Device used : QUV - Type of test: Accelerated Weathering- Test method: ASTM 154 - Irradiance: 0.77 Watts per square meter - Source: UVA 340 lamp

0

2

4

6

8

10

12

0 100 250 500 1000 1250 1500 2000

Visual color, cha

lk, crack ra

ting

[Scale: 0

‐‐Ve

ry poo

r , 10 Excellent]

UV exposure time (hrs)

Parylene N

Parylene CParylene HT


Chemical Resistance

Chemical Tested Parylene N Parylene C Parylene HT

10% Nitric Acid, RT 0.1 0.1 0.0

10% Nitric Acid at 75oC 0.2 0.1 0.0

70% Nitric Acid, RT 0.2 0.2 0.0

70% Nitric Acid at 75oC Brittle 1.8 1.2

10% Sulfuric Acid, RT 0.1 0.3 0.0

10% Sulfuric Acid at 75oC 0.2 4.1 0.0

95-98% Sulfuric Acid, RT 0.2 0.4 0.0

95-98% Sulfuric Acid at 75oC 5.3 5.1 2.8

% Swelling


Parylene Barrier Properties

Water Vapor Transmission Polymer N2 O2 CO2 H2

Parylene N 3 15.4 84.3 212.6

Parylene C 0.4 2.8 3 43.3

Parylene HT 4.8 23.5 95.4 –

Epoxy (ER) 1.6 4 3.1 43.3

Polyurethane (UR) 31.5 78.7 1,181 –

Silicone (SR) – 19,685 118,110 17,717

Gas Permeability at 25°C, (cc•mm)/(m2•day•atm)a


Corrosion ControlParylene HT

Uncoated (left side) and Parylene HT coated (right side) PCB boards after 144 hours salt fog test in accordance with ASTM B117-(03)


CTE & Microorganism Resistance

0.0

20.0

40.0

60.0

80.0

100.0

CT

E (

pp

m)

Temperature ( °C )

36 ppm at Room Temperature

0

1

2

3

4

Effe

ctiv

enes

s Ra

ting

Parylene N Parylene C Parylene HT Filter Cotton Duck

Test Samples

7 days14 days21 days28 days

Rating: 0 = None

1= Traces of growth (less than 10%)

2= Light growth (10-30%)

3= Medium growth (30-60%)

4= Heavy growth (60% to complete coverage)

Test Method: ASTM G-21

Coefficient of Thermal Expansion Microorganism Resistance


Flexibility & Flame Resistance

• Flexibility: Tested in accordance with method 6221 of FED-STD-141 (bent 180 degrees on a 1/8” mandrel)

– There was no evidence of cracking or crazing of the coating on any of the Parylene N, C and Parylene HT specimens tested.

• Flame Resistance: Tested in accordance with method 2021 of FED-STD-406.

– All Parylene N, C and Parylene HT specimens were determined “self extinguishing”.

Parylene Type(Four Specimens of

Each Type)

Time of 1st

Application(Seconds)

Time of 2nd

Application (Seconds)

Results

Parylene N 30 30 Self Extinguishing

Parylene C 30 30 Self Extinguishing

Parylene HT 30 30 Self Extinguishing


Improvement in Wire Lead & Bond Strength

• A bare 1-mil aluminum wirehas a typical bond strength of 3to 5.5 grams.

• A 1-mil coating of Parylene Cover the wire and bondincreases that strength tobetween 60 and 70.

Wire-bond strength vs. Parylene C coating thickness on a hybrid-to-chip lead

Parylene HT is expected to improve wire lead and bond strength similarly.


Salt Fog Testing of LED Board

Front side

Back side

Method: ASTM B117-9 for 168 hours

Parylene coated LEDs showed no corrosion, while corrosion was seen on acrylic coated boards.


Prediction of End of Useful Life

Parylene Types

150oC 135oC 80oC

Parylene HT ~ 40 yrs. ~ 100 yrs. >100 yrs.

Parylene C ~ 24 hours ~ 70 hours ~ 10 yrs.

1

10

100

1000

10000

100000

1000000

10000000

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Log Time to Failure (h

rs)

103/T Ko

Arrhenius Plot: Parylene HT vs. Parylene CLog Time to Failure vs. Reciprocal Absolute Temperature

(Failure: reduced elongation and tensile strength)

150oC

80oC

49

6o C

44

1o C

39

4o C

35

2o C

31

5o C

28

2o C

25

3o C

22

7o C

20

3o C

18

1o C

16

2o C

14

4o C

12

7o C

11

1o C

97

o C

84

o C

72

o C

60

o C


Practical IssuesParylene as a Barrier

• Quality and type of substrate• Substrate preparation• Masking and adhesion promotion• Fixturing• Handling

Failed assembly with spots of poor adhesion

Good assembly withgood adhesion (no spots)


Adhesion Challenges

Corrosion of a PCBDelamination, chipping

Blister

Delamination with corrosion


Coating adhesion failure leading to delamination and/or corrosion

No clean flux residue and corrosion on a PCB

Adhesion Challenges


Developments in Adhesion Promotion Technologies

AdPro Plus & AdPro Poly are trademarks and service marks of Specialty Coating Systems, Inc.

Chemical compounds applied to a variety of polymeric substrates (e.g., polyimide, epoxy, acrylic, EPDM, etc.) as a tie layer prior to the

application of Parylene coating.

AdPro Poly®

Chemical compounds applied to a variety of metallic and plastic substrates (e.g., Stainless Steel, Cobalt-Chromium, Copper, Gold,

Iridium, Nitinol, Platinum, Solder, Tin, Titanium, Tungsten, Aluminum, Nickel, Chromium, Brass, Polycarbonate, etc.) as a tie

layer prior to the application of Parylene coating.

AdPro Plus®

AdPro Plus and AdPro Poly are registered trademarks of Specialty Coating Systems, Inc.


Adhesion Systems

Silane A-174 commonly used adhesion

promotion system

AdPro Plus®

AdPro Poly®

Substrates

Metallic substrates•Stainless Steel, Cobalt Chromium,

Copper, Gold, Iridium, Nitinol, Platinum, Silver, Solder, Tin, Titanium, Tungsten, Aluminum, Nickel, Chromium and Brass.

Plastic Substrates•Polycarbonate, COP, COC, Polyester,

Acrylic, Epoxy, Silicone Rubber, PEEK, Santoprene, Styrene Butadiene, Bakelite, Polyamide and Polyimide.

Evaluation of Adhesion Systems


• Biocompatibility Testing– Parylene C coating using AdPro Plus and AdPro Poly– Per ISO-10993

• Thermal Humidity Aging Resistance– Parylene C & Parylene HT using AdPro Plus– FED STD 141, Method 4061 (Referenced in MIL-I-46058C)

• Insulation Resistance– Parylene C & Parylene HT using AdPro Plus – In accordance with MIL STD 202, Method 302

• Adhesion Testing - ASTM D 3359

– Test conditions:• 50% RH, after 24 & 48 hrs• Autoclave 125oC for 1 hr

Evaluation of Adhesion Technology


Adhesion Test Results


Adhesion Promotion Technologies

DuPont™ and Kapton® are trademarks or registered trademarks of E.I. du Pont de Nemours and Company.


Qualified Product List - Mil Spec


Advanced Parylene Applications

Image courtesy of Dr. Y. C. Tai, Caltech.

Parylene check valveParylene platinum retinal implant electrodes


Advanced Parylene Applications

Check valve

Electrolysis pumpIn-channel check valve

Parylene channelMicro pump

Reaction chamber or reservoir

100 mMicro Active Valve

Thermal Flow

Sensor

Images courtesy of Dr. Y. C. Tai, Caltech.


10 and 30 micron silicon vias

Parylene Etching


Parylene Etching

Anisotropic profile of 55 µ Parylene

Anisotropic profile of 10 µ Parylene

ICP etch recipes for low temperature (5ºC) Parylene etching

Reference: A HIGH ASPECT RATIO, FLEXIBLE, TRANSPARENT AND LOW-COST PARYLENE-C SHADOW MASK TECHNOLOGY FOR MICROPATTERNING APPLICATIONSBy: S. Selvarasah1, S. H. Chao, C.-L. Chen, D. Mao, J. Hopwood, S. Ryley, S. Sridhar, A. Khademhosseini, A. Busnaina, and M. R. Dokmeci, Shadow Mask Transducers 2007

Etching Method ParylenePlasma (200 mT, 400W) 0.19 µm/min

RIE (100 sccm, 200mT, 400W) 0.56µm/min

DRIE (60 sccm, 23mT, 800W) 0.77µm/min


ConclusionParylene Technology for Electronics

Parylene N, C and Parylene HT® are suitable and capable of meeting the growing reliability & protection requirements of electronics packaging.

Parylene HT has additional advantages:

• Exceptional thermal stability in air and inert atmosphere

• Improved electrical properties

• Excellent crevice penetration

• Low coefficient of friction

• UV stability

• Resistance to solvents, corrosive chemicals and gases


Parylene Technology for Electronics

John SterrettTerritory ManagerE [email protected] 214.383.3600F 214.292.9722

Rakesh Kumar, Ph. D.VP of TechnologyE [email protected] 317.244.1200 x 266F 317.472.1215

Contact InformationAlan HardyAutomotive, Electronics &Military Market ManagerE [email protected] 317.244.1200 x 261F 317.472.1215

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