Ultra high reliable lead free alloy to meet high reliability requirement (90iSC) Henkel Loctite Corporation AE Adhesive Electronics South China Technical Engineer Forrest Lin Cell Phone: + 86 13923738177 Email: [email protected] Agenda • Background • Alloy research • Theory • Element selection • Optimization • Alloy property • Physical property • Reliability • Questions • Summary 2 August 27, 2014 Background • Electronics industry implemented lead free, lead and lead alloy forbidden • Traditional lead free material SAC alloy facing challenges at high reliable field, such as, aerospace, military , medical and automotive etc.. 3 August 27, 2014 Background continued • As professional supplier Henkel Loctite fully recognized these issues • From 2006, partner with customers, material suppliers and academy together developing the new alloy. • Definition new alloy CTQ • Lead free • Can withstand continuous 150 + Celsius • Bear ultra high thermal shock (-55 ~ 150 Celsius) • Reflow peak lower than 230 Celsius • Meet ROHS 4 August 27, 2014 Partners • Initiative • Siemens Berlin (central lab) • Academy • University of Bayreuth • Fraunhofer inst. IZM • Industrial customers • Siemens • Bosch • Motorola 5 August 27, 2014 • Suppliers • Henkel (Multicore) • Stannol • Cookson (Alpha Metals) • Seho • Infineon (Munich) • TI (Munich) • Epcos (Munich) • Ruwel Research 6 August 27, 2014 Theory N f c pl const. (Coffin/Manson) Hypothesis: Reducing plastic strain per cycle pl by increasing creep resistance will increase cycles to failure N f SnPb(Ag) pl = 80°C SnAgCu pl 120°C 7 August 27, 2014 90iSC = pl 150°C equal cycles to failure N f reliability Alloy selection Improving the creep strenth Solid solution hardening Disperse solution hardening Grain refinement Element selection Bi 8 Solid solution hardening, lower the melting point. Sb Solid solution hardening, increase the alloy melting point. Ni Disperse solution hardening August 27, 2014 Elements Rejected In Cs Te Ce Ba Fe Cost, slight toxicity toxic highly toxic, Tm toxic, Eutectic 220 °C Compounds toxic, Tm Tm Optimization • Compression creep test • Cylindrical samples • 6mm diameter • 9mm height • Temperature range: - 40C to 175C • Strain rates: 10-1 to 10-4 s-1 • Creep stress σ (N/mm2 plateau stress) is measured as a function of strain rate • Exponent n is slope in log-log plot 9 August 27, 2014 Optimization Stress TrueSpannung wahre [N/mm²] Different alloy creep property 160 5,5 103 s 1 120 T = 25 °C 80 K: Creep stress 40 SAC SAC+Ni0,2 SAC+Sb5 SAC+Bi8 0 80 40 0 Dehnung [%] wahre True Strain True Stress: w 1 True Strain: w ln(1 ) (SAC=SnAg3.8Cu0.7) 10 August 27, 2014 120 Optimization • Different alloy creep property (SAC=SnAg3.8Cu0.7, 6 part = SAC+Bi3Sb1.5Ni0.2) Ambient 150C 1 1 0,1 [ s 1 ] SnPb n=9 SAC n=10 6-part n=13 0,1 [ s 1 ] 0,01 0,01 0,001 0,001 0,0001 0,0001 10 11 100 [ N / mm] August 27, 2014 300 5 SnPb n=5 SAC n=7 6-part n=7 10 [ N / mm] 100 Optimization Maximum operating temperature [°C] (Creep resistance) • Different alloy with different melting point： 180 SnPb37 SAC SAC +Bi+Sb+Ni 160 SAC+Bi4 SAC+Bi6 SAC+Bi8 Sb-addition 140 120 Bi-addition SAC+Sb2,5 SAC+Sb3,75 SAC+Sb5 SnAg3,8Cu0,7 SAC+Ni0,2 Ni-addition 100 SAC+Bi+Sb+Ni SnPb37 80 180 200 220 240 260 Soldering temperature [°C] (Wetting tests) 12 August 27, 2014 280 Optimization • 90iSC melting point range within 209 – 218℃. DSC-Signal [mW/mg] 0.0 SnAg3,8Cu0,7 Tsol = 217 °C SnAgCu+Bi+Sb+Ni Tsol = 209 °C -0.4 -0.8 Potential for lowered reflow temperature? + Thermal load component /PCB + Interface properties -1.2 Heating rate: 10 K/min -1.6 150 175 200 225 250 Temperature [°C] 90iSC Alloy Composition Solution: SnAg3.8Cu0.7Bi3Sb1.4Ni0.15 13 August 27, 2014 Real running DSC 14 August 27, 2014 United States of America Patent 15 August 27, 2014 Alloy Performance 16 August 27, 2014 Physical property • Alloy melting point range from 209 Celsius to 218 Celsius • Other properties close to SAC 387 17 August 27, 2014 Metallergy Structure of 6 component solder (SnAgCu+Bi+Sb+Ni) Structure of Standard leadfree solder (SnAg3,8Cu0,7) Sn-Matrix (Sb,Bi) Sn-Matrix Ag3Sn Ag3Sn (Cu,Ni)6Sn5 Cu6Sn5 18 August 27, 2014 SEM Structure of 6-part alloy (SnAgCu+Bi+Sb+Ni) Ag3Sn Bi 2 µm Ag3Sn Sn-Matrix (Sb,Bi) 10 µm 20 µm Bi (Cu,Ni)6Sn5 19 August 27, 2014 1 µm Ag3Sn Reliability testing 20 August 27, 2014 90iSC, SAC387 and SN63 Thermal cycling Electronical failure with thermal cycle TBG4 21 40 Chip-components from CR0402 CR2512 per Board, no failures on TO263, QFP and SO16 August 27, 2014 90iSC，SAC387 and SN63 thermal cycling comparison micro structure after 1k cycle SnPb Structure after 1000 Cycles SnAgCu Innolot (90iSC) 22 August 27, 2014 90iSC Solder SEM 23 August 27, 2014 90iSC Solder SEM 24 August 27, 2014 90iSC Solder SEM 25 August 27, 2014 90iSC EDX 26 August 27, 2014 90iSC IMC by EDX SEM Element Image 27 August 27, 2014 90iSC IMC EDX 28 August 27, 2014 Alloy Element EDX Quantification 29 August 27, 2014 Alloy micro shape and Angular 30 August 27, 2014 90iSC , SAC387 and SN63 Thermal cycling Shear strength 1206 resistor TBG1 / 31 TCT –40/+125°C August 27, 2014 Solder alloy 90iSC and SAC387 Shear strength Hypothesis Example: 0201 Chip resistor Shows that 90iSC alloy at –40 +150C is equivalent to SAC at –40 to +125C 32 August 27, 2014 Shear Strength Reliability 90iSC solder SAC+Bi3Sb1.5Ni0.2 Vibration testing 33 August 27, 2014 90iSC and SAC387 Vibration testing Failure characteristics in vibration testing with/without thermal cycling (TCT), 0603 resistor 34 SAC alloy, 90iSC alloy, SAC alloy, 90iSC alloy, 0 temperature cycles 0 temperature cycles 500 temperature cycles 500 temperature cycles August 27, 2014 Vibration testing Solder joints in a copper rod clamped into a stainless steel holder Table vibrates vertically. Inertia gives alternating stress in joint Source: N. Barry PhD thesis (Goodrich, Birmingham Univ.) 35 August 27, 2014 Vibration testing Source: N. Barry PhD thesis (Goodrich, Birmingham Univ.) 36 August 27, 2014 Vibration testing 2 FEA 37 August 27, 2014 Vibration test result 90iSC performs similarly to SnPb Clearly outperforms SAC 305 & SnCu (Sn100C) From Nathan Barry PhD Thesis “Lead-free solders for high-reliability applications: high-cycle fatigue studies" (Metallurgy and Materials Dept, University of Birmingham, October 2008). 38 August 27, 2014 Raw data 39 August 27, 2014 40 August 27, 2014 Drop test 41 August 27, 2014 Drop test result 42 August 27, 2014 Drop test result OSP 43 August 27, 2014 NiAu Combined X-ray Analysis Cu OSP / Voiding QFN 44 August 27, 2014 SO20 X-ray Analysis Cu OSP / Voiding CC1206 45 August 27, 2014 CR1206 Issues • 90iSC alloy not compatible with Tin-lead surface finish of PCB and component • SnPbBi easily form low temperature eutectic (98C) • 90iSC ONLY suitable for lead free process • 90iSC slight lower spreading capability, solder wire difficult to manufacture however Henkel developed well the halogen free – 0 halogen 90iSC C400 solder wire 46 August 27, 2014 Summary • Within -40 to 150 Celsius thermal cycling found, 90iSC alloy obviously better than SAC387 • Found after 500 cycling of vibration, 90iSC obviously better than SAC387 • Very close performance at drop testing • 90iSC uncompatible with tin lead surface finish and component metal 47 August 27, 2014 Thank you!
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