reality of new, high reliability solders€¦ · craig hillman dfr monthly webinars feb 24, 2016. 1...

9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com

Reality of New, High Reliability Solders

Craig Hillman DfR Monthly Webinars Feb 24, 2016

9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com1

New, High Reliability Solders? How did we get here?

o Let’s go back 7000 years ago…


o First solders introduced in Mesopotamia / Egypt

o Primarily for jewelry and weapon making

Initial Solders (pre-Silicon Valley)

Alloys of choice were

‘hard solders’

(based on gold and

other precious alloys)

Ouch! Too expensive

and too hard to

process


o Soft solders believed to be invented by the Gauls around 2000 BC

o Extensive tin ore deposits in the area

o Technology diffused throughout Europe

o Primarily consisted of three (3) ratios of tin/lead

o 63Sn/37Pb (fine)

o 50Sn/50Pb (common)

o 37Sn/63Pb (plumbing)

o Technology does not really change till 1900’s

Initial Solders (pre-Silicon Valley)(cont.)

Google Books,. (2016). Metallurgy in Antiquity: A Notebook for Archaeologists and

Technologists, By Robert James Forbes. Retrieved 24 February 2016, p. 259


Why SnPb solders? Why Not?

o Relatively cheap (at least the lead side)

o Wets really well (at least on the tin side)

o Tin bonds (forms an intermetallic) to almost every common metal (copper, nickel, zinc, gold, silver, iron, aluminum)

o Really low melt temperature (183°C)

o A true eutectic material (very repeatable, less sensitive to different cooling rates)

Tin/Lead (SnPb) Solders


o SnPb solder and electronics was a natural fit

o SnPb solder was the default joining material for metals

o Most early wire splices were soldered and taped joints

o Vacuum tube based computers used an extensive amount of wiring

o Most common ‘bug’ from the original SEAC was bad solder joints!

o Electronics just borrowed from its ancestors!

Solder and Electronics

History of Computing in the Twentieth Century (1980), edited by Nicholas Metropolis, Memories

of Bureau of Standards’ SEAC (Ralph Slutz), p. 474

D. Dini, “Some History of Residential Wiring Practices in the US,” UL, Aging Wiring Conference, Chicago, IL, 2006


o Over next 50+ yrs, SnPb solder becomes default joining

material in solid state electronics

o 63Sn37Pb: Hand, reflow, wave, rework, die attach

o 90Pb10Sn: High temperature (>125C), ‘no-collapse’ attach

(i.e., solder bumps)

SnPb Solder and Electronics


o Initial catalyst was elimination of Pb-containing plumber

solder (Safe Drinking Water Act, 1986)

o Banning of lead in all solders was considered by the

Clinton (US) administration in the mid-1990’s,

o First commercial product with leadfree solder was Motorola

cell phone in 2000

o Legislation first codified by EU in 2002 (2002/95/EC)

and implemented in 2006

The End of SnPb Solder


o Initial transition to Tin-Silver-Copper solders

o Different solders for different assembly processes

o Migration from SAC405 to SAC387 to SAC305 driven by the 3P’s (performance, patent, and price)

o However, insufficient drop performance and high price of silver has driven the widespread introduction of low or no silver alloys (especially on the packaging side)

o SN100C, SAC0307, SAC105, SAC125Ni, etc.

o Latest generation of leadfree solders is all about ‘high reliability’

Leadfree Solder


o Increasing number of applications

have large number of thermal cycles

o Especially in transportation and

lighting (LEDs)

o Increasing number of applications

have operating temperatures

greater than 125C

o Key area of concern is

between 125C and 150C

Why High Reliability Solders?


o Traffic Lights

o Typical light cycle is 120 seconds

o 30 cycles/hr x 18 hrs/day x 365 days/yr x 10 years =

almost 2 million thermal cycles!

o Automotive Brake Lights

o Designed for 300K to 600K stops (on-off cycles) over

15-year lifetime

o One stop every 250 – 1000 meters? Yuck!

Large Number of Thermal Cycles: LED Applications


o Lifetime between 20 to 25 years

(or more!)

o Warranty is less (6 to 10 years)

o Energy-efficient motion detection

results in >20 on-off cycles/day

o Results in over 200,000 thermal cycles

LED Applications: Residential/Commercial Lighting


o Leadless LED packaging for lowest cost,

highest thermal conduction

o Insulated metal substrates (IMS) for

lowest cost, highest thermal

conduction

o Lack of air flow can result in DT

of 30C to 60C

LED Applications: Residential/Commercial Lighting (cont.)

Cai, M., Yang, D., Tian, K., Chen, W., Chen, X., &

Zhang, P. et al. (2016). A hybrid prediction

method on luminous flux maintenance of high-

power LED lamps. Applied Thermal Engineering,

95, 482-490.

Far beyond most traditional ‘high

reliability’ applications


Who Are the “High Reliability” Solders?

o Focus on ‘drop-in’ replacements for SAC305 and improved thermal cycle performance

o Does not include alloys ‘optimized’ for drop and thermal cycling (SACmand M770) or much higher melt temperatures (BiAgX or nanosilver)

o Innolot*

o Heraeus: InnoRel (Innolot and HT1)

o Henkel: 90iSC

o Alpha/Alent: MaxRel

o Senju M794

o Koki SB6NX58-M500SI


o Developed by a European consortium in early 2000’s

o Patent application in 2003

o Siemens AG (initiative), Cookson, Epcos, Fraunhofer-IZM,

Inboard, Infineon, Loctite multicore, Microtech, Motorola,

Robert Bosch, Ruwel, Seho, Stannol, Texas Instruments,

University of Bayreuth

o Focus was on increasing creep resistance (reducing the

amount of strain range or energy being dissipated with

each thermal cycle)

Innolot (and other names)


o Creep is the movement of dislocations (specifically climb or out of plane movement)

o Dislocations can be ‘pinned’ or blocked by the presence of ‘impurities’

o Changes stress states

o Increase distance required to move

o Increases energy required to move vacancies, break atomic bonds

Innolot / 90SiC / MaxRel: Secret of Success


o Added antimony (Sb) and bismuth (Bi) for solid solution

hardening

o Balances change in melt

temperature (Sb increases,

Bi decreases)

o Added nickel (Ni) for dispersion hardening (intermetallic

formation)

Innolot / 90SiC / MaxRel: Secret of Success (cont.)


o End Result is a Six (6) Part Alloy:

Sn3.8Ag0.7Cu3.0Bi1.4Sb0.15Ni

Innolot / 90SiC / MaxRel Formulation


o Creep performance improved over range of temperatures

Innolot et. al. (Creep Performance)

0.0001

0.001

0.01

0.1

1

10 100 1000

e[s

-1]

s [N/mm²]

SnPb n=6

SAC n=9

6-Stoff n=8

0.0001

0.001

0.01

0.1

1

10 100 1000

e[s

-1]

s [N/mm²]

SnPb n=5

SAC n=7

6-Stoff n=9

100C 125C


o Maybe?

o After 12 years, there has been limited market penetration

o Most markets don’t have these needs

o The multi-component solder is more expensive

o The multi-component solder is harder to control

o Even after 12 years, understanding of performance can

be limited and contradictory

Does Innolot et. al. work?


Innolot References (pre 2014)

Company Year Title Data

Fraunhofer 2006 FE-Analysen zur Thermoermüdung Test- und Feldzyklen Acceleration Factors (based on shear)

Siemens 2006Material-Dependent Reliability Characteristics of Lead-Free Solder

JointsTemp cycle (not based on shear?)

Fraunhofer 2007Low-cycle Fatigue of Ag-Based Solders Dependent on Alloying

Composition and Thermal Cycle ConditionsCreep strain rate, shear test vs. temp cycle

Henkel 2008 New Lead-Free Alloy that Takes Under-the-Hood Heat in Stride Thermal shock, 1206 resistor (shear)

Cookson 2008 Fatigue Resistant Lead-Free Alloy For Under Hood Applications

Fraunhofer 2008FEA Based Reliability Prediction for Different Sn-Based Solders

Subjected to Fast Shear and Fatigue LoadingsCreep behavior

Henkel 2008Development of a Novel Lead-Free Solder for High Reliability

ApplicationsCreep, temp cycle, vibe, drop

U. of

Birmingham2008

Lead-free Solders for High-Reliability Applications: High-Cycle

Fatigue StudiesHigh cycle fatigue (mechanical samples)

Tech U. of Berlin 2009Mechanical Behaviour of SAC-Lead Free Solder Alloys with Regard to

the Size Effect and the Crystal Orientation

Heraeus 2010New Developments in High-Temperature, High-Performance Lead-Free

Solder AlloysShear Force vs. Temp Cycles (same as Five)

Philips 2010Study on the Reliability of High Power Device Assemblies Using High-

Pb Solder Alternatives: An OverviewCreep behavior

Volkswagen 2010Solder joint reliability in automotive applications: New assessment

criteria through the use of EBSD

Heraeus 2011 Microbond Assembly Materials, InnoRel Series – for a higher reliability Shear Force vs. Temp Cycles


Company Year Title Data

Goodrich 2011 High Reliability Pb-Free Printed Circuit Board Assembly

Bari Polytechnic

(Italy)2012

Wideband Measurement Method for Prognosis of Soldering

Failure on Electronic Boards

NREL 2012 Thermal Performance and Reliability of Bonded Interfaces

Heraeus 2012Novel Interconnect Materials for High Reliability Power Converters

with Operation Temperatures above 150°C

Auburn 2013EFFECT OF ISOTHERMAL AGING AND HIGH STRAIN RATE ON

MATERIAL PROPERTIES OF INNOLOTStress-Strain/Modulus (Room Temp); Ramberg-Osgood

Alpha 2013 Increasing Solder Reliability at Elevated Temperatures Creep behavior, Thermal cycling, RC components, -40/150C

NREL 2014 Stress Intensity of Delamination in a Sintered-Silver Interconnection

Henkel N/A Lead-free for High-reliability, High-temperature Applications Creep behavior

Henkel N/ADevelopment of a Lead-Free Alloy for High-Reliability, High-

Temperature ApplicationsCreep behavior

Henkel N/A DEVELOPING A Pb-FREE SOLDER THROUGH MICRO-ALLOYING Creep behavior (same as two and three)

Siemens N/A Pb-FREE ALLOY ALTERNATIVES: RELIABILITY INVESTIGATION Acceleration Factors (based on shear?)

Fraunhofer N/AThermal test- and field cycling induced degradation and its

Febased prediction for different SAC soldersCreep behavior, shear force vs. Temp cycles

Alpha ALPHA® OM-350 with InnoLot® Performance Data Thermal cycling, RC components, -40/150C; Vibe (0603)

Innolot References (pre 2014)(cont.)


o Initial publications tended to rely on shear stress testing to

demonstrate fatigue performance

o Shear Strength ≠ Thermal Fatigue Life

Thermal Cycle Performance of Innolot et. al.


o Shear Strength (cont.)

Thermal Cycle Performance of Innolot et. al. (cont.)

Shear strength at 125°C test temperature, 1206 Chip resistor

TCT –40/+125°C


o An early thermal fatigue study suggested up to a 2.5X

improvement in lifetime. Impressive!

Innolot and Thermal Cycling


o However, the data does not correlate with other studies

o 1206 / SAC305 is behaving like 2512 / SAC305

o 1206 / Innolot is behaving like 1206 / SAC305

Innolot and Thermal Cycling (cont.)

SAC305

Innolot


o Ceramic Substrate LEDs on FR4 orInsulated Metal Substrates

o -40/140C, 15 min dwells, thermal shock

o -40/125C, 30 min dwells, thermal shock

o Absolute time to failure not provided

o Wha??

o If time to failure < 100 cycles, data may not be very relevant to larger cycles

o Relative time to failure varies across the DoE

o Large ceramic / IMS / -40 to 140C: +30%

o Small ceramic / IMS / -40 to 125C: -7%

o Small ceramic / FR4 / -40 to 125C: +125%

Innolot and Thermal Cycling (Elger et. al.)


o Additional testing using periodic thermal transient

measurements to define

failure

o Ceramic LED (small?)

on IMS

o -40/125C, 30 min dwells,

thermal shock

o This time provides

absolute time to failure

o +85% improvement

Innolot and Thermal Cycling (Elger et. al.)(cont.)


o Chip components and a variety of BGAs

o Primarily SAC305 balls, but two with Innolot solder balls (CABGA36 and

CABGA208); -40/125C, thermal cycle, 2 hr cycle

Innolot and Thermal Cycling (Sanders et. al., CAVE)

• Innolot is superior to

SAC305 (~2.5X)• Superior performance

also observed with just

Innolot paste

• SnPb performs similar

to SAC305• Suggests a need for

more benign conditions

to understand field

improvement Not aged


o Innolot paste improvement goes away with other package

styles (no data on Innolot ball and Innolot paste)

Innolot and Thermal Cycling (Sanders et. al., CAVE)(cont.)


DfR’s Experiences: LED Attach

Test

Condition

Cycles to Failure

(SAC405)

Cycles to Failure

(Innolot)Improvement

-50C/140C

IMS 1 440 520 18%

IMS 2 580 660 14%

IMS 3 3600 7500 108%

IMS 4 4300 4500 5%

-40/125C

IMS 2 770 2100 173%

IMS 3 2900 6900 138%

IMS 4 5200 6600* 27%

-30/110C

IMS 2 820 2900 254%

IMS 3 3300 7100* 115%

IMS 4 5700 12000* 111%


o Three automotive organizations have expressed interest in high reliability solder alloys

o One initially observed significant improvement in lifetime under testing (especially with chip components)

o However, subsequent challenges (performance and pricing) have resulted in pushing the alloy into niche applications

o One is encouraging suppliers to switch, but has not performed their own testing

o One is still in evaluation stage

DfR’s Experiences: Automotive Applications


o DfR is in the business of predicting solder joint fatigue

o Over 150 companies have purchased and are using

Sherlock Automated Design Analysis software

o We perform over 75-100 solder joint predictions every

year

o Based on our visibility, increasing interest in high reliability

alloys, but not in widespread use

DfR Experiences: Globally


o There are some indications that Innolot’s higher modulus could result in a divergence in crack behavior relative to SAC305

o Creep damage and void coalescence maybe less likely

o Brittle crack initiation and crack propagation may be more likely (Dudek, 2014)

o This divergence speaks to the two different approaches in predicting solder joint fatigue behavior

o Energy-Based or Fracture Mechanics

o May also explain some of the discrepancies in test results

o Similar observation with SAC solders when first tested under thermal cycling

Are High Reliability Solders Reliable?


o High Reliability Solders can have very impressive test

results

o Does not mean they are necessarily a good fit for the

application (or that they will even provide an

improvement in lifetime)

o Solder fatigue predictions require more than just testing

o A comprehensive understanding of material behaviors can

result in robust predictions and confident integration of High

Reliability Solders

Conclusion

reality of new, high reliability solders€¦ · craig hillman dfr monthly webinars feb 24, 2016. 1...

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