Corrosion Concerns and Testing for Electronic...
Transcript of Corrosion Concerns and Testing for Electronic...
University of MarylandCopyright © 2015 CALCE
1Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion Concerns and Testing for Electronic Equipment
Michael [email protected] of MarylandCollege Park, MD 20742
iNEMI Research Webinar SeriesApril 30, 2015
University of MarylandCopyright © 2015 CALCE
2Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
What is CALCE?Center for Advanced Life Cycle Engineering (founded 1987) is dedicated to providing a knowledge and resource base to support the development and sustainment of competitive electronic components, products and systems. Focus areas:
• Physics of Failure • Design of Reliability• Accelerated Qualification• Supply-chain Management• Obsolescence• Prognostics
Center Organization
16 research faculty 5 technical staff 40+ PhD students20+ MS students11 visiting scholars
http://www.calce.umd.edu
CALCECenter for Advanced Life Cycle Engineering
forElectronic Products
and Systems
Research Contracts
• Large scale programs • Medium to long‐term durations• Contractual agreements• Examples:
Software development,testing, training programs
Electronic Products
and SystemsConsortium
•Risk assessment, management, and mitigation for electronics
Prognostics and Health ManagementConsortium
• Techniques based on data trending, physics‐of‐failure, and fusion
Education
• MS and PhD programs• International visitors• Web seminars • Short courses for industry
LabServices
• Small to medium scale• Rapid response• Examples: Failure analysis, measurement,design review, supplier assessment
Standards• Putting CALCE research to work for industry
• Examples:IEEE GEIA IPCJEDECIEC
University of MarylandCopyright © 2015 CALCE
3Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
• High atmospheric concentrations of sulfur can be found in a wide variety of industries that use electronics [1]• Pulp and paper industry (by-product of wood degradation)• Sewage treatment (by-product of organic degradation)• Construction (released during excavation)• Iron smelting (by-product of smelting process)• Mining (found in mineral rock)
Corrosive Sulfur Environments
1. “Hydrogen Sulfide in Industry”. WorkSafeBC website. Workers' Compensation Board of British Columbia. (2007)
University of MarylandCopyright © 2015 CALCE
4Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion on Fielded Electronic Systems
• Corrosion of silver in a fielded resistor array
• Corrosion on a PCB in a clay modeling facility for a month and a half [1]
• ENIG-plated connectors corroded during shipping and handling
[1] Mazurkiewicz, P., “Accelerated corrosion of PCBs due to high levels of reduced sulfur gasses in industrial environments,” Proceedings of the 32nd International Symposium for Testing and Failure Analysis, Austin, TX, 2006
University of MarylandCopyright © 2015 CALCE
5Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion of Electronic Systems• Different chemistries (Sulfides, Chlorides, etc.) can attack
metals used in electronic systems (Cu, Ag, Ni, etc.)• Heat and moisture can increase reactivity• Reactive materials can be a result of improper cleanliness
or a corrosive environment (Shipping, Storage or Use)
Corrosive Environment
Moisture
Reactive Chemicals
HeatPre-Exposure Post-Exposure
Copper coupons are commonly used as witness coupons for measuring corrosive environments
[1] Rice et al. Atmospheric Corrosion of Copper and Silver. Journal of the Electrochemical Society 128.2. (1981)
[1]
University of MarylandCopyright © 2015 CALCE
6Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion vs. Electrochemical MigrationCorrosion Electrochemical
Migration
Copper (+)
Copper (-)
+- e-
Cu2+ H20Dendrite
Coppere- Cu+ Cu2+
H20
• Driven by an electrical potential in the presence of water
• Leads to the formation of metal dendrites
Corrosive Gases(SO2, Cl2, H2S)
• Driven by the oxidation of metal
• Does not require water• Formation of corrosion
products (not pure Metal)
Corrosion Products(Cu2O, CuCl, Cu2S…)
Acids and Ions
University of MarylandCopyright © 2015 CALCE
7Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Classification of Corrosive Environment• Corrosivity of an environment for electronics is often
characterized by copper corrosion film thickness.• There are various methods that can be used to measure film
thickness, each with their advantages and disadvantages.
BattelleSeverity
Class1 year
film thicknessI <35 nmII 40 to 70 nmIII 80 to 400 nmIV >500 nm
Classifying environments using copper coupons. [1]
• Pro: Simple method• Con: Bad assumption of products
Weight Gain
• Pro: Does not require pre- exposure data• Con: Underestimates corrosion
Cathodic Reduction
• Pro: Accurate measurement• Cons: Requires ion milling
Profilometry
University of MarylandCopyright © 2015 CALCE
8Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
ASHRAE - 2011 Gaseous and Particulate Contamination Guidelines For Data Centers
• Airborne Particles • Mechanical, Chemical, and Electrical effects• Recommendation that data centers be kept clean to ISO Class 8• Restricting particle size is thought to reduce harmful dust (with
high ionic contamination)• Gaseous contamination
• ISA -71.04 Gaseous Corrosivity level of G1• Reactivity monitoring recommended
• Maximum corrosion rate of copper should be <200 Å/month• Maximum corrosion rate of silver should be <200 Å/month
• Gas filtration can be used to meet these goals
University of MarylandCopyright © 2015 CALCE
9Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion Testing of Electronics
Humidity Thermal Storage Salt Spray
Mixed Flowing Gas
Flowers of Sulfur Clay
University of MarylandCopyright © 2015 CALCE
10Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Mixed Flowing Gas Testing
MFG chamber used at CALCESchematic for a MFG chamber
• Mixed flowing gas testing uses corrosive gases, heaters, and humidifiers to provide an accelerated corrosion test environment
• Different standards provide chamber conditions that can be used to reach target corrosion levels (i.e. ASTM B827 (Practice) and ASTM B845 (Electrical contacts))
University of MarylandCopyright © 2015 CALCE
11Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Standards for MFG Testing
Battelle• Environmental classification from least(Class I) to most(Class IV)• Classes II-IV have accelerated test conditions: 2 days in chamber = 1 year in field
EIA• Environmental classification from least(Class I) to most(Class IV)• Class IIA-IV is an accelerated test conditions: 5 days in chamber = 3 years in field
IEC• Method 1 is for gold coatings• Methods 2-4 are for electronics in moderate(2&4) and severe(3) environments
Telcordia• Test methods for telecommunication equipment in indoor and outdoor settings
IBM• G1(T) is accelerated test for a business office environment
University of MarylandCopyright © 2015 CALCE
12Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Standards for MFG TestingCreator Class Temp (ºC) RH (%) H2S (ppb) Cl2 (ppb) NO2 (ppb) SO2 (ppb)
Battelle II 30±2 70±2 10+0/-4 10+0/-2 200±25 ---
III 30±2 75±2 100±10 20±5 200±25 ---
IV 50±2 75±2 200±10 50±5 200±25 ---
EIA-364-65 II 30±2 70±2 10±5 10±3 200±25 ---
IIA 30±1 70±2 10±5 10±3 200±25 100±20
III 30±2 75±2 100±20 20±5 200±25 ---
IIIA 30±1 70±2 100±20 20±5 200±25 200±50
IV 40±2 75±2 200±20 30±5 200±25 ---
IEC 68-2-60 1 25±1 75±3 100±20 --- --- 500±100
2 30±1 75±3 10±5 10±5 200±50 ---
3 30±1 75±3 100±20 20±5 200±50 ---
4 25±1 75±3 10±5 10±5 200±50 200±20
Telcordia GR-63-CORE 5.5
Indoor 30±1 70±2 10±1.5 10±1.5 200±30 100±15
Outdoor 30±1 70±2 100±15 20±3 200±30 200±30
IBM G1 30±.5 70±2 40±5% 3±15% 610±5% 350±5%
University of MarylandCopyright © 2015 CALCE
13Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
* Number in brackets indicates number of samples in test
Copper Coupon Weight Gain of MFG Test Environments
University of MarylandCopyright © 2015 CALCE
14Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Flowers of Sulfur Test• The Flowers of Sulfur (FoS) test is described in ASTM-B809,
and uses a chamber with a sulfur source and a humidity source in an oven to create a corrosive test environment
• Variations of this test include high temperatures and no moisture
Samples
Sensor
Sealed Chamber Sulfur Source
Oven
Salt solutionSamples
Sulfur Source
Salt solution
FoS test chamber used at CALCESchematic for a FoS testing
University of MarylandCopyright © 2015 CALCE
15Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Elevated Temperature and Duration Test PlanA series of tests were carried out in the ASTM test vessel
• Temperatures (°C): 50, 75, 85, 95 and 105• Durations (days): 1, 5, 10, and 15• Specimen: 3 copper coupons
SamplesSulfur source
Salt solution1 5 10 15
50758595105
Test Matrix
Tem
pera
ture
(ºC
)
Duration (Days)
University of MarylandCopyright © 2015 CALCE
16Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
FOS Data – Temperature PlotCopper Corrosion Thickness
University of MarylandCopyright © 2015 CALCE
17Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
P values 50 °C 75 °C 85 °C 95 °C 105 °C1 day 5 day 10 day 15 day 1 day 10 day 1 day 5 day 10 day 15 day 1 day 10 day 1 day 5 day 10 day
50 °C
1 day 3.28E‐01 2.01E‐01 8.28E‐02 1.04E‐01 9.37E‐04 4.17E‐04 6.42E‐03 5.04E‐06 8.49E‐06 3.37E‐03 9.08E‐04 1.05E‐04 5.18E‐06 2.90E‐045 day 3.28E‐01 3.40E‐01 1.36E‐01 2.04E‐01 9.82E‐04 9.21E‐03 7.12E‐03 5.46E‐06 8.54E‐06 5.60E‐03 9.16E‐04 2.17E‐04 5.61E‐06 2.92E‐0410 day 2.01E‐01 3.40E‐01 5.53E‐01 8.90E‐01 1.28E‐03 6.61E‐01 1.06E‐02 9.74E‐06 8.79E‐06 4.87E‐02 9.43E‐04 4.51E‐03 9.92E‐06 2.99E‐0415 day 8.28E‐02 1.36E‐01 5.53E‐01 6.02E‐01 1.41E‐03 6.82E‐01 1.36E‐02 1.12E‐05 8.92E‐06 1.19E‐01 9.62E‐04 9.78E‐03 1.14E‐05 3.04E‐04
75 °C 1 day 1.04E‐01 2.04E‐01 8.90E‐01 6.02E‐01 1.21E‐03 7.45E‐01 1.05E‐02 8.27E‐06 8.76E‐06 4.08E‐02 9.45E‐04 2.78E‐03 8.44E‐06 3.00E‐0410 day 9.37E‐04 9.82E‐04 1.28E‐03 1.41E‐03 1.21E‐03 X 1.07E‐03 1.45E‐02 3.84E‐02 3.24E‐04 1.56E‐03 1.41E‐02 1.78E‐03 3.74E‐02 5.23E‐03
85 °C
1 day 4.17E‐04 9.21E‐03 6.61E‐01 6.82E‐01 7.45E‐01 1.07E‐03 1.01E‐02 5.74E‐06 8.70E‐06 1.85E‐02 9.48E‐04 2.90E‐04 5.90E‐06 3.00E‐045 day 6.42E‐03 7.12E‐03 1.06E‐02 1.36E‐02 1.05E‐02 1.45E‐02 1.01E‐02 3.49E‐04 1.23E‐05 2.50E‐02 1.37E‐03 5.45E‐02 3.46E‐04 4.13E‐0410 day 5.04E‐06 5.46E‐06 9.74E‐06 1.12E‐05 8.27E‐06 3.84E‐02 5.74E‐06 3.49E‐04 1.96E‐05 1.06E‐05 3.86E‐03 1.04E‐05 9.43E‐01 9.28E‐0415 day 8.49E‐06 8.54E‐06 8.79E‐06 8.92E‐06 8.76E‐06 3.24E‐04 8.70E‐06 1.23E‐05 1.96E‐05 9.15E‐06 3.96E‐03 9.41E‐06 1.96E‐05 1.16E‐02
95 °C 1 day 3.37E‐03 5.60E‐03 4.87E‐02 1.19E‐01 4.08E‐02 1.56E‐03 1.85E‐02 2.50E‐02 1.06E‐05 9.15E‐06 1.02E‐03 4.14E‐02 1.08E‐05 3.18E‐0410 day 9.08E‐04 9.16E‐04 9.43E‐04 9.62E‐04 9.45E‐04 1.41E‐02 9.48E‐04 1.37E‐03 3.86E‐03 3.96E‐03 1.02E‐03 1.08E‐03 3.88E‐03 2.01E‐01
105 °C1 day 1.05E‐04 2.17E‐04 4.51E‐03 9.78E‐03 2.78E‐03 1.78E‐03 2.90E‐04 5.45E‐02 1.04E‐05 9.41E‐06 4.14E‐02 1.08E‐03 1.07E‐05 3.34E‐045 day 5.18E‐06 5.61E‐06 9.92E‐06 1.14E‐05 8.44E‐06 3.74E‐02 5.90E‐06 3.46E‐04 9.43E‐01 1.96E‐05 1.08E‐05 3.88E‐03 1.07E‐05 9.33E‐0410 day 2.90E‐04 2.92E‐04 2.99E‐04 3.04E‐04 3.00E‐04 5.23E‐03 3.00E‐04 4.13E‐04 9.28E‐04 1.16E‐02 3.18E‐04 2.01E‐01 3.34E‐04 9.33E‐04
• ANOVAs were performed to compare pairs of sample• F‐test used to compare variance between/within test groups• 90% probability was used (p‐value < 0.1 highlighted below)
• Assumed independent samples (different locations) and normal distribution of corrosion weight gain [1]
1. ASTM International. “Corrosion Tests and Standards”, ASTM, Baltimore, MD (2005)
P-values for F-testing between FOS test pairs
Analysis of Variance
University of MarylandCopyright © 2015 CALCE
18Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Model Fitting to Averages
Θ = Corrosion Film Thickness (nm)X = Constant (nm) Y = Constant (1/ºC)Z = Constant (1/hoursX = 2.304 Y = 0.07057 Z = 0.01324 R2 = 0.9829
Θ Xe
Thi
ckne
ss (n
m)
University of MarylandCopyright © 2015 CALCE
19Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Clay Testing• The Clay Test uses high sulfur modeling clay (30-50% elemental
sulfur) to create a sulfur-rich test environment• Heating wetted clay (45 - 55⁰C) releases sulfur• Samples placed in the test chamber may be cooled to increase
condensation onto the samples
Clay test using bulk clayClay test using shredded clay
University of MarylandCopyright © 2015 CALCE
20Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Clay Test Weight Gain
• Ultra-Conductive Copper (Alloy 101)• Size of the Sample :-14mm*14mm• Thickness – 0.49mm• Number of Samples – 10• Hole Size: 2.55mm(Diameter)• Area =176.375mm2
University of MarylandCopyright © 2015 CALCE
21Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Comparison of TestsCopper Weight Gain
This plot is based on copper weight gain. Coupons used for these measurements were ultra-pure copper with base weights between .65 to 0.9 grams
University of MarylandCopyright © 2015 CALCE
22Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Comparison of 10-Day Test Environments
Test ConditionsWeight Gain(mg/g)
Thickness(nm/day)
Yrs in Class 4 Batelle Env.
H2S - 1800 ppb, 20% RH 0.08 113.7 2.3H2S - 250 ppb,75% RH 0.09 125.7 2.5H2S - 1800ppb, 75% RH 0.12 163.2 3.3FoS - 50C 0.40 542.3 10.84 gas - 200ppb/40C/75%RH 0.46 636.8 12.74 gas - 200ppb/40C/75%RH 0.49 677.1 13.54 gas - 200ppb/50C/50%RH 0.69 946.0 18.9FoS - 75C 0.76 1042.4 20.8FoS - 85C 1.47 2017.6 40.44 gas - 1700ppb/40C/75%RH 2.80 3838.5 76.8FoS - 105C 39.44 54094.2 1081.9
• Note: These calculations are based on composition assumptions for MFG testing. FOS product composition must be better understood.
University of MarylandCopyright © 2015 CALCE
23Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Comparison of Corrosion Tests
Test Benefits WeaknessesMixed Flowing Gas
• Multiple Contaminants• Adjustable Concentrations• In-line Monitoring
• Limited Temperature Range
• Gases are expensive• Chamber has significant
maintenanceFlowersof Sulfur
• Salt Solution controls RH• Easily reusable chamber• Requires only a vessel, an
oven, and consumables
• Only sulfur contamination• Oven must be on for
entirety of test duration
Clay Test
• Only one consumable• Does not require an oven
• Only sulfur contamination• Periodic heating of clay
University of MarylandCopyright © 2015 CALCE
24Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
ENEPIG Test Vehicle (2011 Study)
Pads
Resistors
Resistors
UnpoweredComb Fingers
•ENEPIG Version #BNi: 4.53±0.15m Pd: 0.05±0.004mAu: 0.05±0.002m
•ENEPIG Version #CNi: 4.17±0.16m Pd: 0.154±0.006m Au: 0.04±0.003m
•ImAgAg: 0.33±0.06m
• Two Solders: SAC305 and SnPb• Observed Features – Optical Inspection
Six 2512 Resistors Three different pad sizes Eight comb finger structures
4 powered, 4 unpowered (5V bias with a11 kΩ resistor) 4 covered by BGA, 4 not covered by BGA(2 of each powered)
Forty pads (Four per resistor and four per chip)
PoweredComb Fingers
University of MarylandCopyright © 2015 CALCE
25Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
ENEPIG Test Matrix
ENEPIG ‐ B ENEPIG ‐ C ImAg
SnPb 1 1 1
SAC305 1 1 1
Solder TypeSurface Finish
Test ConditionsTemperature: 50oC Hydrogen Sulfide (H2S): 200 ppb Sulfur Dioxide (SO2): 200 ppbRelative Humidity: 75% Chlorine (Cl2): 50 ppb Nitrogen Dioxide (NO2): 200 ppb
These conditions represent a GX class exposure as there was more than 2000 nm/day of corrosion products.
Copper
Ag - Pure
Ag - Sterling
Average weight gain of 12 coupons
University of MarylandCopyright © 2015 CALCE
26Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Optical Inspection – Pads• The exposure resulted in pad discoloration
Immersion Silver (2.5×)
ENEPIG B (2.5×)
ENEPIG C (2.5×)
Unexposed 5 day 10 day
University of MarylandCopyright © 2015 CALCE
27Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Day 10 - Optical Inspection
Dendrite observed growing onENEPIG-C SnPb S2-Fingers 5-6 (Biased)
100x5x
20x
University of MarylandCopyright © 2015 CALCE
28Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Inspection of Comb Fingers
Covered Comb Structure Exposed Comb Structure
Fingers completely covered with copper and sulfur
Corrosion spots composed of copper and sulfur detected
University of MarylandCopyright © 2015 CALCE
29Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
ENEPIG TestSurface Insulation Resistance measurement
• Resistance measurements of the comb structures were conducted prior to MFG exposure using a high resistance meter.
• They all showed a nominal resistance value of ~ 2 × 1010 Ω.• The failure criteria was a two order of magnitude drop in
resistance.• A 5 day exposure resulted in the failure of two structures that
were uncovered and under bias in ENEPIG Version B – SAC305. • A 10 day exposure resulted in additional failures.
E-B-SnPb E-B-SAC305 E-C-SnPb E-C-SAC305 ISA-SnPb ISA-SAC305Biased‐Uncovered 0 4 3 4 0 0Biased-Covered 0 1 1 0 0 0Unbiased–Covered 0 1 0 0 0 0Unbiased-Uncovered 0 2 0 0 0 0
# of failed samples on day 10 (four comb structures in each test group)
University of MarylandCopyright © 2015 CALCE
30Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion Testing: Leadframes
Telcordia Outdoor – 10 Days Batelle III – 240 hours
• Several MFG test environments were used to generate corrosion on noble metal leadframes
• Only Telcordia Indoor conditions failed to generate corrosion
University of MarylandCopyright © 2015 CALCE
31Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Examination of Coating On Creep CorrosionPart
• CY37128P100-125axi• Pitch 0.28• Plating Ni/Pd/Au• Lead wire: Copper Alloy
Coatings• Acrylic (AR): Type 1 (machine spray)
and Type 2 (hand spray)• Silicone (SR) by machine spray• Polyurethane (UR) by machine spray• Parylene (XY) by vacuum deposition• ALD-Cap O5TA200* by vacuum
deposition
University of MarylandCopyright © 2015 CALCE
32Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Test Condition• Coated and non-coated test specimens were separated into two
groups to be subjected to environmental loading sequences.– TC: Temperature cycling for 100 cycles with 30 min dwells
Cycle A (-55°C/20°C) / Cycle B (-15°C/60°C) / Cycle C (20°C/95°C)– TH: Temperature Humidity with 50°C/50% RH for 200 hrs– Mixed Flowing Gases (MFG) for 48 hrs (EIA-364-TP65A class IV)
• Accumulated Loading Cycles
• Inspections of all components for tin whisker growth are conducted after each accumulated loading cycle with TC, TH, and MFG by optical and scanning electron microscopes.
TC-A TC-B TC-C MFG TH
Class Temp (°C) RH (%) H2S (ppb) Cl2 (ppb) NO2 (ppb) SO2 (ppb)
IV 50 ± 2 75 ± 2 200 ± 20 30 ± 5 200 ± 50 200 ± 50
University of MarylandCopyright © 2015 CALCE
33Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Creep Corrosion on TQFPs
Non-coated AR1 XY
• With the exception of Parylene C, corrosion products were observed on the surfaces of all Ni/Pd/Au finished TQFP leads which were subject to MFG exposure.
WithoutMFG
With MFG
After 3rd Load Cycle
University of MarylandCopyright © 2015 CALCE
34Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Acrylic Coatings
AR2
For the acrylic coatings, corrosion products were restricted to the edge of the terminals where coating coverage was thin or non-existent. Here, AR1 performed better than AR2. This result may be due to the differences in coverage. An examination of coverage is under way.
AR1
University of MarylandCopyright © 2015 CALCE
35Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Silicone and Urethane Results
SR URSilicone showed substantial damage while UR was restricted to edges that had little to no coverage.
University of MarylandCopyright © 2015 CALCE
36Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Parylene and ALD Results
ALD
Other than areas that had damage prior test, the Parylene coated specimens show no corrosion damage. The ALD coating showed corrosion on all terminals.
XY
University of MarylandCopyright © 2015 CALCE
37Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Creep Corrosion on TQFPs• Cu whiskers and dendrites were observed on the corroded surface of
TQFPs with MFG exposure on non-coated and AR1, AR2, SR, UR and ALD coating.
• The sulfur (S) and chlorine (Cl) were detected via EDX on the corroded surfaces.
• Only Parylene C coated specimens were free from corrosion and no whiskers or dendrites were observed.
AR1 ALDSR
University of MarylandCopyright © 2015 CALCE
38Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Creep Corrosion on TQFPsNon-Coated
SR
AR1
ALDAR2
UR
University of MarylandCopyright © 2015 CALCE
39Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
EDX Mapping ResultS Cl
Cu
Creep Corrosionon Non-coated TQFPs
University of MarylandCopyright © 2015 CALCE
40Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Background on Thin Film Chip Resistors• Surface mount thick film chip resistors are inexpensive parts used in a
variety of electronic systems• The silver layer of chip resistors corrodes in sulfur-containing
environments, forming silver sulfide
Overcoat
Ceramic Substrate
Inner Ag
Resistor Element
OvercoatSolder Termination
Protective Barrier
Solder Termination
Ceramic Substrate
University of MarylandCopyright © 2015 CALCE
41Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Comparison of Overlap Between Overcoat and Metallization
Type 1 2 3
4 5 6
Coat
Inner Electrode
Termination
Substrate
University of MarylandCopyright © 2015 CALCE
42Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Corrosion Testing: Chip Resistors• Flowers of Sulfur Testing carried at 85°C (30 days)
– Formation of silver sulfide [failure in damaged resistors]
Ag2S
Before(As-received)
After(As-received)
Ag2S
ExposedAg
Before(Damaged)
After(Damaged)
University of MarylandCopyright © 2015 CALCE
43Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Maximum Stress SnPb v/s SAC
Solder Max., Stress
SnPb 62 MPa
SAC305 83 MPa
Board 1.57 mmCopper 70 µm
Nickel 20 µm
Standoff 63.5 µm
Silver 10 µm
Alumina 550 µm
Element 20 µm
Coat 10 µm
University of MarylandCopyright © 2015 CALCE
44Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Torsional Loads on Sample DIMM Cards• Torsional loading imposes cyclic out-of-plane deformation to a populated PCBA.• A portion of this deformation is transferred to the interface between interface of
overcoat and metallization in proportion to stiffness of board, rigidity of electronic components, compliance of leads and the solder interconnects.
Ang
le o
f tw
ist
Time
184 Pin DDR DIMM CardDDR – Double data rateDIMM – Dual in-line memory module
R-Net
University of MarylandCopyright © 2015 CALCE
45Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Test MethodologyDDR 256MB DIMM 184-pin
Torsion Test ±18° 2000 cyc.
R-Net Visual Inspection
Control Set
105°C/24Hr FoS Exposure
R-Net Visual Inspection
• Torque 15 in-lb• Velocity 40°/sec• Hold time: 1 sec at +/- extremes
University of MarylandCopyright © 2015 CALCE
46Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Photo Documentation
Post FoS test
Post torsion and FoS
Con
trol
Gro
upTo
rsio
nSt
ress
Gro
upResistor #4 T7
Resistor #4 T7
University of MarylandCopyright © 2015 CALCE
47Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Details of R-Net #4 T7 after 105°C 24hr FoS
• Examination at 200x shows that the growth consists of a gray material with a metallic luster.
• Heavier growth is seen at the termination to metal interface.
University of MarylandCopyright © 2015 CALCE
48Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Chip Resistor Findings• The FoS test method at 105C can induce silver sulfide
formation in silver conductor chip resistors.• Construction factors, such a coating overlap and
coating thickness, play a role in mitigation silver sulfide formation failure of silver conductor chip resistors.
• Process stresses, such as reflow and handling, must be considered in any part evaluation program. For example, SAC assembly induces higher stress on overcoat seam which may result in a higher potential for separation and silver sulfide failures.
University of MarylandCopyright © 2015 CALCE
49Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
Conclusions• The test methods discussed (Mixed Flowing Gas, Flowers of
Sulfur, and Clay Testing) all have strengths and weaknesses• Some conformal coat materials offer protection but other may
increase corrosion and poor coverage may also aggravated the situation
• Cover areas have been found to exhibit lower corrosion than exposed regions.
• Flower of Sulfur (FoS) test which was originated for porosity appears to be gaining favor for board and assembly tests.
• Product cleanliness and workmanship contribute to corrosion/electrochemical induced failures.
• Chip resistors with silver inner terminations are susceptible to sulfur based corrosion. Construction and assembly stresses are factors in dictating their susceptibility to corrosion.
University of MarylandCopyright © 2015 CALCE
50Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
For More Information on CALCE Research
http://www.calce.umd.edu/
University of MarylandCopyright © 2015 CALCE
51Center for Advanced Life Cycle Engineeringwww.calce.umd.edu Innovation Award Winner
A special thanks to our research sponsors!• Alcatel‐Lucent• Advanced Bionics• Aero Control Systems• Agilent Technologies• American Competitiveness Inst.• Amkor• Arbitron• Arcelik• ASC Capacitors• ASE• Astronautics• Atlantic Inertial Systems• AVIC• AVI‐Inc• Axsys Engineering• BAE Systems• Benchmark Electronics• Boeing• Bosch• Branson Ultrasonics• Brooks Instruments• Buehler• Capricorn Pharma• Cascade Engineering • CAPE – China• Celestical International• Channel One International• Cisco Systems, Inc.• Crane Aerospace & Electronics• Curtiss‐Wright Corp• CDI• De Brauw Blackstone Westbroek• Dell Computer Corp.• DMEA• Dow Solar• DRS EW Network Systems, Inc.• EIT, Inc.• Embedded Computing & Power• EMCORE Corporation• EADS IW France
• EMC• Emerson Advanced Design Ctr• Emerson Appliance Controls• Emerson Appliance Solutions• Emerson Network Power• Emerson Process Management• Engent, Inc.• Ericsson AB• Essex Corporation• Ethicon Endo‐Surgery, Inc.• Exponent, Inc.• Fairchild Controls Corp.• Filtronic Comtek• GE, GE Healthcare• General Dynamics, AIS & Land Sys.• General Motors• Guideline• Hamlin Electronics Europe• Hamilton Sundstrand• Harris Corp• Henkel Technologies• Honda• Honeywell• Howrey, LLP• IBM• Intel• Instituto Nokia de Technologia• Juniper Networks• Johnson and Johnson• Johns Hopkins University• Kimball Electronics• L‐3 Communication Systems• LaBarge, Inc• Lansmont Corporation • Laird Technologies • LG, Korea• Liebert Power and Cooling• Lockheed Martin Aerospace• Lutron Electronics
• Microsoft• MIT Lincoln Laboratory• Motorola• Mobile Digital Systems, Inc.• NASA• National Oilwell Varco• NetApp• nCode International• Nokia Siemens• Nortel Networks• NOK AG• Northrop Grumman• NTSB• NXP Semiconductors• Ortho‐Clinical Diagnostics• Park Advanced Product Dev. • Penn State University• PEO Integrated Warfare• Petra Solar • Philips• Philips Lighting• Pole Zero Corporation• Pressure Biosciences• Oracle• Qualmark• Quanterion Solutions Inc• Quinby & Rundle Law• Raytheon Company• Rendell Sales Company• Research in Motion• Resin Designs LLC• RNT, Inc.• Roadtrack• Rolls Royce• Rockwell Automation• Rockwell Collins• Saab Avitronics• Samsung Mechtronics• Samsung Memory
• S.C. Johnson Wax• Sandia National Labs• SanDisk• Schlumberger• Schweitzer Engineering Labs • Selex-SAS• Sensors for Medicine and Science• SiliconExpert• Silicon Power• Space Systems Loral• SolarEdge Technologies• Starkey Laboratories, Inc• Symbol Technologies, Inc• SymCom• Team Corp• Tech Film• Tekelec• Teradyne• Textron Systems• The Bergquist Company• The M&T Company• The University of Michigan• Tin Technology Inc.• TÜBİTAK Space Technologies• U.K. Ministry of Defence• U.S. Air Force Research Lab• U.S. AMSAA• U.S. ARL• U.S. NSWC, NAVAIR• U.S. Army Picatinney/UTRS• U.S. Army RDECOM/ARDEC• Vectron International, LLC• Vestas Wind System AS• Virginia Tech• Weil, Gotshal & Manges LLP• WesternGeco AS• Whirlpool Corporation• WiSpry, Inc.• Woodward Governor