Part 2 - Thermal Properties

Database for Solder Properties with Emphasis on New Lead-free Solders Release 4.0

National Institute of Standards & Technology and
Colorado School of Mines

Back to main page File updated on: 2002 February 11 8:30:50 pm

Properties of Lead-Free Solders (Cont.)

2. Thermal Properties

2.1. Solidus, Liquidus, and Melting-point Temperatures

Table 2.1.1. Liquidus and Reflow Temperatures of Candidate Lead-Free Solder Alloys for Replacing Eutectic Tin-Lead Solder

Alloy Composition	Liquidus Temp. (ºC)	Reflow Temp. (ºC)	Melting Range^# (ºC)
Sn-2Ag			221-226
Sn-3.5Ag	221	240 – 250
Sn-0.7Cu	227	245 – 255
Sn-3.0Ag-0.5Cu*	220^**	238 – 248
Sn-3.2Ag-0.5Cu	218	238 – 248	217-218
Sn-3.5Ag-0.75Cu*	218	238 – 248
Sn-3.8Ag-0.7Cu	220^**	238 – 248	217-210
Sn-4.0Ag-0.5Cu			217-219
Sn-4.0Ag-1.0Cu*	220^**	238 – 248	217-220
Sn-4.7Ag-1.7Cu*	244^**	237 – 247

Sn-5Sb			232-240
Sn-0.2Ag-2Cu-0.8Sb*	285^**	246 - 256	226-228^%
Sn-2.5Ag-0.8Cu-0.5Sb*	225	233 – 243

Sn-2Ag-7.5Bi*	216^**	220 – 230
Sn-3Ag-3Bi*	218^**	233 – 243
Sn-3Ag-5Bi*	216^**	230 – 240
Sn-3.4Ag-4.8Bi*	215^**	225 – 235	200-216
Sn-3.5Ag-3Bi*	217^**	230 – 240

Sn-58Bi			138
Sn-3.2Ag-1.1Cu-3Bi*	240^**	230 – 240
Sn-3.5Ag-3In-0.5Bi*	215^**	230 – 240
Sn-3Bi-8Zn			189-199

V. Solberg, "No-Lead Solder for CSP: The Impact of Higher Temperature SMT Assembly Processing," Proc. NEPCON West 2000 Conf. (Feb. 28 - Mar. 2, 2000) Anaheim, CA (Source: Indium Corp.)
^#N.-C. Lee, "Lead-Free Chip-Scale Soldering of Packages," Chip Scale Review, March-April 2000
*Patented compositions; may require licensing or royalty agreements before use.
^**For more information see: Phase Diagrams & Computational Thermodynamics, Metallurgy Division of Materials Science and Engineering Laboratory, NIST.
^%Kester, SAF-ALLOY

Table 2.1.2. Melting Temperatures of Lead-Free Solders

Alloy	Melting Temperature Range (ºC)	Comments^#
Sn-25Ag-10Sb	233 (m.p.)	High strength; patented by Motorola ("Alloy J")
Sn-0.7Cu	227^@
Sn-3.5Ag	221^@	Excellent strength and wetting
Sn-2Ag	221 – 226
Sn-2.8Ag-20In	175 – 186
Sn-5Sb*	232 – 240	Good high-temperature shear strength
Sn-58Bi	138^@	Well established history; inexpensive
Sn-9Zn	199*	Corrosion; high dross

Sn-0.5Ag-4Cu	217 – 350	Very wide and high melting range; Engelhard’s lead-free plumbing solder
Sn-2Ag-0.75Cu	217 – 219
Sn-3.2Ag-0.5Cu	217 – 218
Sn-3.8Ag-0.7Cu	217 – 220
Sn-4Ag-0.5Cu	217 – 225
Sn-4Ag-1Cu	217 – 220
Sn-4.7Ag-1.7Cu	217 – 244
Sn-8Zn-3Bi	192 – 197

Sn-0.2Ag-2Cu-0.8Sb	287 – 218	High melting range; Kester Solder Co.’s Aquabond
Sn-2.5Ag-0.8Cu-0.5Sb (Castin)	217 – 225
Sn-2Ag-7.5Bi	190 – 216
Sn-3.4Ag-4.8Bi	201 – 205	(205 – 210)^%
Sn-3.5Ag-3Bi	208 – 217	(m.p.: 220 ºC)^%
Sn-2Ag-3Bi-0.75Cu^%	205 – 217
Sn-3.5Ag-5Bi-0.7Cu^%	198 – 213

Sn-2Ag-4Bi-0.5Cu-0.1Ge^%	202 – 217
Sn-57Bi-0.1Ag^%	138 – 140
Sn-52In	118*	Lowest melt. pt.: expensive

^{@Eutectic

N.-C. Lee and W. Casey, "Soldering Technology for Area Array Packages,"
Proceedings: NEPCON WEST 2000 (February 27 – March 2, 2000), Anaheim, CA

^#N.-C. Lee, J.A. Slattery, J.R. Sovinsky, I. Artaki, P.T. Vianco, "A
Drop-In Lead-Free Solder Replacement," Proceedings: NEPCON West Conference (February
28 – March 2, 1995), Anaheim, CA

*Ning-Cheng Lee, "Lead-Free Soldering of Chip-Scale Packages," Chip Scale
Review, p. 42 (March/April 2000)

^%Rao Mahidhara, "A Primer on Lead-Free Solder," Chip Scale Review
(March-April 2000)}

2.2. Thermal Properties: Miscellaneous

Table 2.2.1. Thickness (µm) of Intermetallics in Solder Alloys Aged at 150 ºC

Alloy:	Sn-3.5Ag		Sn-4Ag-.5Cu
Inter-metallics:	Cu₃Sn	Cu₆Sn₅	Cu₃Sn	Cu₆Sn₅
Time (h)	Cu₃Sn	Cu₆Sn₅	Cu₃Sn	Cu₆Sn₅
0	0.25	2	0.25	2
48	0.5	3.25	0.5	2.5
96	0.75	2.5	0.75	2.5
264	1.0	2.5	1.0	3
480	1.5	3	1.5	4.5
984	2.5	4	2.5	(nonuniform morphology)

Angela Grusd, "Lead Free Solders in Electronics," SMI97, p. 648

Table 2.2.2. Thermal and Electrical Properties of Castin™ (Sb-2.5Ag-0.8Cu-0.5Sb)

Melting Point	215 – 217 ° C
Thermal Diffusivity	35.82 +/- 0.18 mm^2/s
Specific Heat	218.99 J/(kg.K)

Thermal Conductivity	57.26 W/(m.K)
Electrical Resistivity	1.21 E-7 ohm.m
Electrical Conductivity	8.25 MS/m

Karl Seelig and David Suraski, "The Status of Lead-Free Solder Alloys," Proc. 50^th IEEE 2000 Electronic Components and Technology Conference (May 21-24, 2000), Las Vegas, NV

Table 2.2.3. Physical and Mechanical Properties of Sn-2.8Ag-20.0In and Sn-37Pb Eutectic Solders

Property (measured at 20 ° C, except where otherwise noted)	Alloys
	Sn-2.8Ag-20.0In	Sn-37Pb (eutectic)
Density (g/cm^3)	7.25	8.36
Electrical resistivity (microhm.m)	0.170	0.146
Thermal conductivity (W/(m.K)) (30 ° C)	53.5	50.9
Thermal expansion (10-6.K-1)	28	25
Tensile strength (psi)	6800	3900
Tensile elongation (%)	47	35
Shear strength (psi)	4800	3450
Poisson’s ratio	0.40	0.40
Young’s modulus (kpsi)	5600	4500

N.-C. Lee, J.A. Slattery, J.R. Sovinsky, I. Artaki, P.T. Vianco, "A Drop-In Lead-Free Solder Replacement," Proceedings: NEPCON West Conference (February 28 – March 2, 1995), Anaheim, CA

Table 2.2.4. Some Physical Properties of Materials Used as Electronic Packaging Conductors

Metal	Melting Point (° C)	Electrical Resistivity (µohm.cm)	Thermal Expansion Coeff. (10^-6/° C)	Thermal Conductivity (W/(m.K))	^#Surface Tension, s
Metal	Melting Point (° C)	Electrical Resistivity (µohm.cm)	Thermal Expansion Coeff. (10^-6/° C)	Thermal Conductivity (W/(m.K))	(dyn/ cm)	(° C)
Aluminum	660.1	4.3	23.0	240	520	750
Antimony	630.5		11.0*	24.0*	383	635
Bismuth	271.0		13.4*	8.0*	376	300
Chromium	1900	20	8.2	66
Copper	1083	1.7	16.6	393; 401*
Gold	1063	2.2	14.2	297
Indium	156.4		32.1*	82.0*	340	170
Lead	327.3				431	500
Molybdenum	2625	5.2	5.0	146
Nickel	1455	6.8	12.8	92; 91*
Palladium	1552	10.8	11.8	70
Platinum	1774	10.6	9.0	71
Silver	960.8	1.6	18.9	418; 429*	923	995
Tin	231.9		22.0*	73.0*	550^% 526 510	232^% 300 500
Tungsten	3415	5.5	4.5	200
Zinc	419.5				785 761	510 640

Invar	1500	46	1.5	11
Kovar	1450	50	5.3	17
Silver-palladium	1145	20	14.0	150
Gold-platinum	1350	30	10.0	130

Au-20Sn	280	16	15.9	57
Sn-37Pb	183				470^%	280^%
Pb-5Sn	310	19	29.0	63
Cu-W(20%Cu)	1083	2.5	7.0	248
Cu-Mo(20%Cu)	1083	2.4	7.2	197

Microelectronics Packaging Handbook, R.R. Tummala and E.J. Rymaszewski, eds. (Van Nostrand Reinhold, 1989, NY)
^# N.A. Lange, Handbook of Chemistry, p. 100 (Handbook Publishers, Sandusky, Ohio, 1956)
^%M. Abtew, "Wetting Characteristics of Lead Free Solders for High Volume Surface Mount Application," Proc. NEPCON West 2000 Conf. (Feb. 28 - Mar. 2, 2000) Anaheim, CA
*J.S. Hwang, "Overview of Lead-Free Solders for Electronics & Microelectronics," Proc. SMI Conf. , p. 405

Table 2.2.5. Thermophysical Properties of Metallic Elements Used In Electronic Packaging

Metal	At. Wt.	Density (20° C)	Melt. Point	Lat. Ht. Fusion	Heat capacity (25° C)		Thermal exp. coef. (20° C)	Electrical Resistivity (20° C)	^#Thermal conductivity
Metal	At. Wt.	(g/cm³)	(° C)	(kg-cal/ g.atom)	(g-cal/ g-at.K)	J/ (kg.K)	(10^-6K^-1)	(10^-6 W .cm)	(W/(m.K))
Aluminum	26.98	2.702	*660.46	2.6	5.817	902.1	23.03	2.62; 2.828^#	238.
Antimony	121.7	6.684 (25° C)	*630.75	4.8	6.08	209.0	11.4	39; 39.1^#	24.5; 23.8§
Bismuth	208.98	9.8	*271.44	2.63	6.1	122.1	13.4§	115; 119.0^#	11.2; 9§
Chromium	51.996	7.1	1903 1860§	3.5	5.58	449.0	8.2	2.6 (0° C)	91.3§
Copper	63.54	8.92	*1084.9	3.11	5.85	385.2	16.6	1.69	416; 397§
Gold	196.97	19.3	*1064.4	3.03	6.0	127.5	14.2	2.4; 2.44^#	311;315.5§
Indium	114.82	7.3	*156.63	0.78	6.55	238.7	33; 24.8§	9; 8.37#	80.0§
Lead	207.2	11.34	*327.50	1.22	6.41	129.4	29.1	21.9; 19.8#	35.0
Molybdenum	95.9	10.2	*2623	6.66	5.61	244.8	4.	4.77; 5.14#	138.
Nickel	58.7	8.90; 8.8^#	*1455	4.2	6.21	442.6	12.8	6.9; 7.24#	76.; 88.5§
Palladium	106.4	12.	*1554	4.12	6.3	247.7	11.8	10.8; 10.21#	75.2
Platinum	195.1	21.45	*1769	5.2	6.35	136.2	8.9	10.5; 9.83#	69.9; 73.4§
Silver	107.87	10.5	*961.93	2.70	6.092	236.3	18.9	1.62; 1.47#	417.; 425§
Tin	118.7	7.31	*231.97	1.69	6.30	222.1	20.; 23.5§	11.4; 11.5#	66.6; 73.2§
Tungsten	183.85	19.3	*3387	8.42	5.97	135.9	4.	5.48; 5.51#	169.; 174§
Zinc	65.38	7.14;7.04^#	*419.58	1.595	5.99	383.3	33.	6; 5.75#	125.;119.5§

N.A. Lange, Handbook of Chemistry pp. 100-107 (pp. 854-861) (Handbook Publishers, Sandusky, Ohio, 1956)
*Thermometric fixed point; E.A. Brandes, Smithells Metals Reference Book, 6^th ed., p. 16-2 (Butterworths, London, 1983) ^#D.E. Gray, ed., American Institute of Physics Handbook, pp. 2-17 (density), 4-40 (ht. cap.), 5-204 (resistivity), 4-78 (th. cond.) (McGraw-Hill, New York, 1957)
§E.A. Brandes, Smithells Metals Reference Book, 6^th ed., p. 14-1 (th. cond.: 0-100° C) (Butterworths, London, 1983)

Table 2.2.6. Some Properties of Materials Commonly Used In Electronics - A

Metal	CTE (10^-6/° C)	Thermal Cond. (W/(m.K))	Elastic Mod. (GPa)	Density (g/cm³)	Poisson’s Ratio (?)
Aluminum	22.3	237	69	2.7
Copper	16.5 16.9^# 17.3*	398	124 125^# 117*	8.9	0.31
Molybdenum	5.0	140	324	10.2
Cu/ Invar/Cu	5.2	167^%	--	8.4
Kovar	5.9	17	138	8.3
Silicon Carbide	2.6	--	412	3.17
Solder (95/5)	28	36	23.5	11.
Diamond	1.7	2300	785	3.51
Silicon	2.8 3.2^#	150	190 110^#	2.3	0.27
Alumina	6.7 7.0^#	21	306 375^#	3.9	0.23
Aluminum Nitride	4.5 4.03^#	250	327 320^#	3.2	0.25
Beryllia	8.0	275	345	2.9
Epoxy / Glass (FR4; T<Tg) (FR4; T>Tg)	12 / 70 x,y: 15.8* z: 80-90* x,y: 20* z: 400*	1.7	17.2 x,y: 7.0* z: 7.5* x,y:17.0* z: 0.6*	1.9
Polyimides	45	8	4.2	1.6

(CTE: Coefficient of thermal expansion)
^%In plane
Walter L. Winterbottom, "Converting to Lead-Free Solders: An Automotive Industry Perspective," JOM, 20-24 (July 1993)
*M.A. Korhonen, D.D. Brown and C.-Y. Li, "Mechanical Properties of Plated Copper," Mat. Res. Soc. Symp. Proc. Vol. 323, p. 104 (MRS, 1994) ("plated [thin foil] copper")
^#S.M. Spearing, M.A. Tenhover, D.B. Lukco, L. Viswanathan and D.K. Hollen, "Models for the Thermomechanical Behavior of Metal/Ceramic Laminates," Mat. Res. Soc. Symp. Proc. Vol. 323, p. 128 (MRS, 1994)

Table 2.2.7. Some Properties of Materials Commonly Used In Electronics - B

Material	Melt. Pt. (° C)	Density (g/cm³)	CTE (10^-6/° C)	Young’s Modulus E (GPa)	Tensile Strength (MPa)
Alumina (Al₂O₃)	2050	3.985	5.8	380	620
Beryllia (BeO)	2530	3.01	8.4 – 9.0	311	172 - 275
Silica (SiO₂) (vitreous)	1710	2.19	0.54	69	110
Zirconia (ZrO₂) / (Yttria: Y₂O₃)	2960	5.56	10.	138	>300

AlN	2400	3.25	5.3	350	270
Si₃N₄	>1750	3.19	3.3	304	>400

Al	660	2.70	23.5	69	50 -195
Cu	1083	8.96	17.0	180
Ni	1453	8.9	13.3	199	660
Mo	2617	10.22	5.1	324.8	458-690
W	3410	19.3	4.5	411.	550-620

S.D. Brandi, S. Liu, J.E. Indacochea and R. Xu, "Brazeability and Solderability of Engineering Materials," ASM Handbook, Vol. 6: Welding, Brazing and Soldering (ASM International, 1993)

Table 2.2.8. Electrical Resistivity and Tempera-ture Coefficient (TCR) of Pure Metallic Elements Used in Electronic Packaging

Metal	Temp.	Room-temperature
Metal	(K)	Resistivity (ohm.cm)	TCR (10^–3 K^-1)
Aluminum	293	2.61	4.2
Antimony	293	37.6	5.1
Bismuth	293	115	4.6
Chromium	300	12.9	5.9
Copper	293	1.58	4.3
Gold	293	2.01	4.0
Indium	293	8.0	5.2
Lead	293	19.3	4.2
Molybdenum	300	5.3	4.35
Nickel	293	6.2	6.8
Palladium	300	10.5	4.2
Platinum	300	10.4	3.0
Silver	300	1.47	4.1
Tin	293	10.1	4.6
Tungsten	300	5.3	4.8
Zinc	293	5.45	4.2

E.A. Brandes, Smithells Metals Reference Book, 6^th ed., p. 16-2 (Butterworths, London, 1983)

Table 2.2.9. Wetting Properties of Sn-2.8Ag-20.0In and Sn-37Pb Eutectic Solders

Fluxes	Sn-2.8Ag-20.0In*
	Wetting Time (seconds)		Wetting Force (mN/mm)
	200 ºC	240 ºC	200 ºC	240 ºC
A	10.60	4.60	0.70	0.71
B	1.53	0.42	0.72	0.56
C	5.08	2.40	0.72	0.64
D	5.73	2.09	0.67	0.67
Geometric Mean	4.66	1.76	0.70	0.64
	Sn-37Pb
A	2.87	1.48	0.73	0.72
B	1.03	0.50	0.71	0.61
C	1.65	1.00	0.75	0.72
D	2.50	1.44	0.73	0.73
Geometric Mean	1.87	1.02	0.73	0.69

N.-C. Lee, J.A. Slattery, J.R. Sovinsky, I. Artaki, P.T. Vianco, "A Drop-In Lead-Free Solder Replacement," Proceedings: NEPCON West Conference (February 28 – March 2, 1995), Anaheim, CA
*J.A. Slattery and C.E.T. White, U.S. Patent 5,256,370 (Oct. 26, 1993)

Table 2.2.10. Wetting Times and Forces (at 300 ºC): Lead-Free Solder Alloys, and Eutectic Tin-Lead

Alloy	T₀ Mean + s	T_2/3 Mean + s	Force (2 s) Mean + s	Force_max Mean + s
Alloy	(s)	(s)	(µN/mm)	(µN/mm)
Sn-3.5Ag	0.0 + 0.0	1.23 + 0.01	549 + 42	579 + 47
Sn-5Sb	0.11 + 0.08	0.74 + 0.07	403 + 14	413 + 15
Sn-2.8Ag-20In	0.0 + 0.0	1.28 + 0.04	250 + 24	290 + 31

Sn-37Pb	0.0 + 0.0	1.00 + 0.06	470 + 24	485 + 19

M.A. Kwoka and D.M. Foster, "Lead Finish Comparison of Lead-Free Solders versus Eutectic Solder," Proc. Surface Mount International Conference (1994), p. 433

Table 2.2.11. Wetting Times (at 250 ºC) of Lead-free Solder Alloys

Alloy	Pure Rosin		Actiec 5 Flux
Alloy	Tb	T2/3	Tb	T2/3
Sn-40Pb	0.6	1.0	0.4	0.5
Sn-3.6Ag	0.9	1.4	0.6	0.8
Sn-3.6Ag-0.7Cu	0.6	1.0	0.5	0.7
Sn-0.7Cu	1.0	1.4	0.7	1.0

^{%Rao Mahidhara, "A Primer on Lead-Free Solder," Chip Scale Review
(March-April 2000)}

Table 2.2.12. Onset of Melting Temperatures for Five Sn-Ag-Cu Lead-Free Solder Alloys

Alloy	Spec. No.	Temperature, Onset of Melting (ºC)
Alloy	Spec. No.	This Work	Other (Ref.)
Sn-3.6Ag-1.5Cu	1	217.0	225 (1)
Sn-4.7Ag-1.7Cu	2a	216.7
Sn-4.7Ag-1.7Cu	2b	216.8
Sn-4.1Ag-0.9Cu	3	216.5
Ave. onset temp., specimens 1-3		216.8
Reference Samples:
Sn-3.8Ag-2.3Cu	--		217.4 (3)
Sn-3.5Ag-0.0Cu	4	220.8	221 (2)
Sn (pure)	5	231.2	231.97 (2)

Chad M. Miller, Iver E. Anderson and Jack F. Smith, "A Viable Tin-Lead Solder Substitute: Sn-Ag-Cu," J. Electronic Matls. 23(7) 595-601 (1994)
(1) E.Gebhardt and G. Petzow, Z. Metallkde. 50, 597 (1950)
(2) T.B. Massalski, Binary Phase Diagrams, 2^nd ed. (Amer. Soc. Metals, 1990)
(3) Miller, Anderson and Smith, Note added in proof, J. Electronic Matls. 23(7) 601 (1994)

Table 2.2.13. Solidus Temperatures and Wetting Contact Angles of Selected Lead-Free Solder Alloys with Use of RMA (GF-1235) Flux

Alloy	Solidus (ºC)	Contact Angle (degrees)
Sn-4.7Ag-1.7Cu	217 (eutectic)	32
Sn-3.33Ag-4.83Bi	212	n.a.
Sn-5Ag-2Bi	214.5	30
Sn-8Ag-3Sb	224	39
Sn-4.5Ag-6Bi-5.4Sb-4In	214	36
Sn-4.4Ag-6Bi-5.3Sb-6In	217	34
Sn-37Pb (control)	183 (eutectic)	16

Iver E. Anderson, "Tin-Silver-Copper: A Lead-Free Solder for Capacitor Interconnects," p. 16, Proc. 16^th Capacitor and Resistor Technology Symposium (CARTS 96), 11-15 March, 1996;

Table 2.2.14. Solidus and Liquidus Temperatures and Wetting Angles of Some Lead-free Alloys on Copper (Note opposing effects on wetting angle of increasing temperature for alloys with or without zinc)

Alloy	Solidus (ºC)		Liquidus (ºC)		Wetting Angle (deg) (with Kester Flux No. 197)
Alloy	Calc.	Exptl.	Calc.	Exptl.	250 ºC	295 ºC	340 ºC
Sn-1Ag-1Sb	222	222	232	232	38		43
Sn-1Ag-1Sb-1Zn					41	41	42
Sn-4Ag-7Sb	229	230	230	230	35		39
Sn-4Ag-7Sb-1Zn					48	46	36
Sn-2Ag-0.8Cu-6Zn	190	217	195	217	77	67	62
Sn-2Ag-0.8Cu-8Zn	191	215	200	215	86	70	52
Sn-10Bi-0.8Cu	178	185	218	217	32		42
Sn-10Bi-0.8Cu-1Zn					33	38	27
Sn-10Bi-5Sb	186	193	228	232	39		48
Sn-10Bi-5Sb-1Zn					50	42	29
Sn-45Bi-3Sb	147	145	168	178			37
Sn-45Bi-3Sb-1Zn					98	46	27

Sn-37Pb (eutectic)							14

M.E. Loomans, S. Vaynman, G.Ghosh and M.E. Fine, "Investigation of Multi-component Lead-free Solders," J. Elect. Matls. 23(8), 741 (1994)

Table 2.2.15. Melting Properties, Resistivity, Wettability and Hardness of Lead-Free Solders

Alloy	T_ex (ºC)	T_p (ºC)	T_ob (ºC)	Electrical Resistivity* (µO-cm)	Wetta-bility Ratio	Hardness (VHN)
Sn-3.5Ag	221.5	226.5	220.0	7.7	97, 95	17.9
Sn-5Bi	219.4	228.7	196.0	11.0	97, 97	25.6
Sn-10Bi	209.1	221.2	165.0	17.7	98, 97	33.0
Sn-5In	219.7	223.4	211.5	8.3	99, 97	20.8
Sn-5Sb	236.8	244.9	231.6	17.1	96, 96	17.2

Sn-3Ag -5Bi	214.4	218.1	191.6	11.6	98, 98	29.9
Sn-3Ag-10Bi	201.5	214.3	164.4	8.8	---	---
Sn-3Ag-3In	210.7	214.7	193.3	7.7	99, 99	21.3
Sn-3Ag-5Sb	225.0	235.9	216.3	10.5	99, 99	25.4
Sn-3Ag-1Zn	215.9	220.9	210.0	10.4	98, 97	18.2
Sn-3Ag-3Zn	217.8	222.5	206.8	4.8	97, 97	21.9

Sn-5Bi-5In	205.5	218.4	177.0	19.1	98, 95	28.0
Sn-5Sb-3In	226.7	240.3	211.7	9.8	98, 97	31.9
Sn-1Cu-5Bi	216.7	226.7	184.8	10.5	96, 95	31.9
Sn-1Cu-5Bi-5In	204.9	211.0	167.5	14.1	96, 95	40.6
Sn-1.5Cu-2Bi-3Sb	224.1	234.5	207.0	8.0	98, 96	32.9
Sn-3Ag-2Cu -2Sb	218.6	230.1	212.8	11.2	98, 98	28.6
Sn-3Ag-3Cu -2Bi	211.1	222.2	195.7	10.6	97, 96	34.5
Sn-3Ag-5Bi-5In	195.7	209.0	158.9	12.1	---	---

Sn (pure)				11.2	---	10.5
Sn-37Pb (eutectic)				17.0	95, 91	12.9

T_ex is the extrapolated onset melting temperature by differential scanning calorimetry (DSC)
T_p is the peak melting temperature by DSC
T_ob is the observed onset melting temperature
*Method of Van der Pauw
S.K. Kang et al., "Pb-Free Solder Alloys for Flip Chip Applications," 49^th Electronic Components Technology Conf. (1999), June 1-4, San Diego CA

Table 2.2.16. Wetting Contact Angles of Sn-Ag, Sn-Bi, and Sn-Zn Alloys on Copper: Eutectic, and With 1% Addition of Ternary Elements

Solder Alloy	SnCl₂, Saturated Solution		Kester Rosin Flux No. 197			20 % Rosin in Isopropyl Alcohol
Solder Alloy	165 ºC	200 ºC	165 ºC	200 ºC	250 ºC	165 ºC	200 ºC	250 ºC
Sn-3.5Ag					38			45
Sn-3.5Ag-1Cu					36			44
Sn-3.5Ag-1In					35			39
Sn-3.5Ag-1Sb					35			35
Sn-3.5Ag-1Bi					28			38
Sn-3.5Ag-5Bi					31			42
Sn-58Bi	10	15	27	28		40	32
Sn-58Bi-1Ag	14	17	35	44		43	39
Sn-58Bi-1Cu	9	12	36	38		40	30
Sn-58Bi-1In	7	12	40	35		56	43
Sn-58Bi-1Sb	20	15	31	35		38	42
Sn-58Bi-1Zn	18	12	58	54		50	--
Sn-8.9Zn					59			58
Sn-8.9Zn-1In					63			53

M.E. Loomans, S. Vaynman, G.Ghosh and M.E. Fine, "Investigation of Multi-component Lead-free Solders," J. Elect. Matls. 23(8), 741 (1994)

Table 2.2.17. Wetting Contact Angles on Copper of Sn-Bi Alloys: Eutectic, and With 1% Addition of Ternary Elements

Solder Alloy	SnCl₂, Saturated Solution		Kester Flux No. 197		20 % Rosin in Isopropyl Alcohol (IPA)		20 % Rosin in IPA + 1% SnCl₂
Solder Alloy	165 ºC	200 ºC	165 ºC	200 ºC	165 ºC	200 ºC	165 ºC	200 ºC
Sn-58Bi	10	15	27	28	40	32	43	35
Sn-58Bi-1Ag	14	17	35	44	43	39	93	45
Sn-58Bi-1Cu	9	12	36	38	40	30	46	31
Sn-58Bi-1In	7	12	40	35	56	43
Sn-58Bi-1Sb	20	15	31	35	38	42
Sn-58Bi-1Zn	18	12	58	54	50	--

M.E. Loomans, S. Vaynman, G.Ghosh and M.E. Fine, "Investigation of Multi-component Lead-free Solders," J. Elect. Matls. 23(8), 741 (1994)

Table 2.2.18. Wetting Properties of Pure Tin, Four Lead-Free Tin Alloys and Three Lead-Tin Alloys

Solder Alloy	Temp. (ºC)	Wetting Time, Mean (std.dev.) (s)	Max. Wetting Force, mean (std.dev.) (mg)	Wetting Rate		Area of Spread (cm²)
Solder Alloy	Temp. (ºC)	Wetting Time, Mean (std.dev.) (s)	Max. Wetting Force, mean (std.dev.) (mg)	mean (std.dev.) (mV/s)	Normalized (Sn = 1)	Fluxite	Power flow Flux
Sn (pure)	282	0.68 (0.10)	607 ( 84)	138 ( 43)	1.00	0.5	0.55

Sn-1Cu	300	0.60 (0.11)	565 ( 82)	120 ( 43)	0.87	0.5	0.5
Sn-3Cu	365	0.19 (0.08)	648 ( 61)	365 (122)	2.64	0.7	0.8
Sn-3.5Ag	260	0.60 (0.12)	533 (109)	124 ( 30)	0.90	0.5	0.6
Sn-5Sb	280	0.83 (0.12)	393 (117)	97 ( 24)	0.70	0.5	0.55
Sn-40Pb	234	0.45 (0.14)	602 (114)	146 ( 43)	1.06	2.2	--
Sn-50Pb	265	0.37 (0.09)	523 (115)	191 (119)	1.38	2.5	2.6
Sn-60Pb	285	0.55 (0.09)	623 ( 68)	100 ( 17)	0.72	1.7	1.9

M.E. Warwick, "The Wetting and Mechanical Properties of Lead-Free Capillary Plumbing Solders," ATB Metallurgie XXV, No. 1, 43-50 (1985)

Table 2.2.19. Lead-Free Solder Alloys: Solidus and Liquidus Temperatures, Coefficient of Thermal Expansion, Surface Tension, and Electrical Resistivity

Alloy	T_sol* (ºC)	T_liq (ºC)	CTE (20 ºC) (x 10⁺⁵/ºC)	Surface Tension (at T_liq + 50 ºC) (mN/mm)		Intermetallic Phases	Electrical Resistivity (µO-cm)
Alloy	T_sol* (ºC)	T_liq (ºC)	CTE (20 ºC) (x 10⁺⁵/ºC)	Air	Nitrogen	Intermetallic Phases	Electrical Resistivity (µO-cm)
Sn (pure)	232		2.6				11.5
Sn-37Pb	183		2.5	417	464		14.5
Sn-3.5Ag	221			431	493	Ag₃Sn	10 – 15
Sn-4Cu-0.5Ag	216	222				Ag₃Sn, Cu₆Sn₅	10 – 15
Sn-0.7Cu	227			491	461	Cu₆Sn₅	10 – 15
Sn-58Bi	138		1.5	319	349		30 – 35
Sn-52In ^§	120		2.0				10 – 15
Sn-9Zn	199			518	487		10 – 15

*Where no liquidus temperature is given, the alloy is eutectic and has a single, definite fusion temperature. (For pure tin the melting point is given.)
^§ (Eutectic: Sn-50.9In)
Judith Glazer, "Microstructure and Mechanical Properties of Pb-free Solder Alloys for Low-Cost Electronic Assembly: A Review," J. Electronic Materials 23(8), 693 (1994)

Table 2.2.20. Fluid Properties of Some Molten Lead-Free Solders

Solder Alloy	Liquidus temperature	Contact angle	Wetting rate	Surface tension
Solder Alloy	(ºC)	(deg)	(dyne/ sec)	(dyne/ cm)
Sn-58Bi	138	43	350	300
Sn-2.8Ag-20In	114 (low-temp. peak); 178 (primary peak)	44	650	390
Sn-3.5Ag-4.8Bi	212	31	2420	420
Sn-2.5Ag-0.8Cu-0.5Sb	217	44	4280	510
Sn-37Pb (eutectic)	183	17	2030	380

I. Artaki, D.W. Finley, A.M. Jackson, U. Ray and P.T. Vianco, "Wave Soldering with Pb-Free Solders," Proc. Surface Mount International (San Jose, CA, August 27-31, 1995), p. 495.

Table 2.2.21. Densities and Costs of Popular Solder Metals and Alloys – A

Metal	Price per kg (2^nd Q. 1999)		Density (g/cm³)	Price per cm³ (2^nd Q. 1999)
Metal	($)	Normalized (Pb = 1)	Density (g/cm³)	($)	Normalized (Pb = 1)
Pb	0.55	1.00	11.36	0.00625	1.00
Sb	2.00*	2.5*	6.684	0.0134	2.14
Cu	1.50	2.73	8.92	0.0134	2.14
Bi	6.60*	8.25*	9.8	0.0647	10.35
Sn	5.70	10.36	7.31	0.0416	6.57
Ag	170.	309.1	10.5	1.78	285.
In	242.50*	303.1*	7.3	1.77	283.

Sn-37Pb	3.80	6.91	8.4	0.0319	5.10
Sn-Pb (solder paste)	90.00	163.6	8.4	0.756	121.
Sn-0.7Cu	5.66	10.29	7.30	0.0413	6.61
Sn-4Ag-0.5Cu	12.25	22.27	7.39	0.0905	14.5

Adapted from Alan Rae and Ronald C. Lasky, "Economics and Implications of Moving to Lead-Free Assembly," Proc. NEPCON WEST 2000 (February 27 – March 2, 2000), Anaheim, CA
*(1992 prices; Pb: $0.80/kg) Paul T. Vianco, "General Soldering," ASM Handbook, Vol. 6, Welding, Brazing, and Soldering (ASM International, 9639 Kinsman Road, Materials Park, Ohio 44073 USA, 1993)

Table 2.2.22. Densities and Costs of Popular Solder Metals and Alloys – B

Element		Cost/(unit mass) [2/3/99]		Density (25 ºC)		Cost/(unit volume)		Comment
Element		$/lb	$/kg	lb/in³	g/cm³	$/in³	$/cm³	Availability
Lead		0.45	0.99	0.41	11.35	0.18	0.011
Zinc		0.50	1.10	0.258	7.14	0.13	0.008
Copper		0.65	1.43	0.324	8.97	0.21	0.013
Antimony		0.80	1.76	0.239	6.61	0.19	0.012
Bismuth		3.40	7.48	0.354	9.80	1.20	0.073	limited
Tin		3.50	7.70	0.264	7.31	0.92	0.056
Silver		84.20	185.24	0.379	10.50	31.91	1.947	limited
Indium		125.00	275.00	0.264	7.31	33.00	2.014	scarce
Alloy	Melt. Range (ºC)							Patented
Sn-37Pb	183	2.37	5.21	0.318	8.80	0.75	0.046
Sn-3.5Ag	221	6.32	13.90	0.268	7.42	2.33	0.142
Sn-0.7Cu	227	3.48	7.66	0.264	7.31	0.92	0.056
Sn-58Bi	139	3.44	7.57	0.316	8.75	1.09	0.067
Sn-5Sb	232-240	3.37	7.41	0.263	7.28	0.88	0.054
Sn-9Zn	199	3.23	7.11	0.263	7.28	0.85	0.052
Sn-4Ag-0.5Cu	217-218	6.55	14.41	0.269	7.44	1.76	0.107
Sn-3.4Ag-4.8Bi	208-215	6.24	13.73	0.272	7.53	1.70	0.104	Y
Sn-3.5Ag-3Bi	216-220	5.92	13.02	0.269	7.44	1.59	0.097
Sn-2.8Ag-20In	179-189	30.06	66.13	0.267	7.39	8.02	0.489	Y
Sn-3.5Ag-1.5In	218	8.15	17.93	0.268	7.42	2.18	0.133
Sn-2Ag-0.5Cu-7.5Bi	186-212	5.09	11.20	0.273	7.56	1.39	0.085
Sn-2.5Ag-0.8Cu-0.5Sb	213-219	5.48	12.06	0.267	7.39	1.46	0.089	Y (Castin™)

Authors not listed; "Lead-Free Alloy Trends for the Assembly of Mixed Technology PWBs", Proc. NEPCON-West 2000 (Feb. 27-Mar. 2) Anaheim, CA

Table 2.2.23. Cost of Lead-Free Solder Alloys Relative to That of Sn-37Pb Eutectic

Alloy	Relative Cost
Alloy	Bar	Paste
Sn-37Pb	1.000	1.000
Sn-3.5Ag	2.29	1.07
Sn-3Ag-2Bi	2.17	1.06
Sn-3.4Ag-4.8Bi	2.26	1.06
Sn-3.2Ag-0.7Cu	2.21	1.06
Sn-3.5Ag-1.3Cu	2.28	1.06
Sn-4.7Ag-1.7Cu	2.56	1.08
Sn-2.6Ag-0.8Cu-0.5Sb	2.06	1.05
Sn-3.5Ag-0.5Cu-1Zn	2.27	1.06
Costs of pure metals (relative to Pb=1): Zn: 1.7; Cu: 3.0; Sb: 3.9; Bi: 8.6; Sn: 11; Ag: 260; Au: 15000

Ning-Cheng Lee, "Lead-Free Soldering of Chip-Scale Packages," Chip Scale Review, p. 42 (March/April 2000)

A. Solder Alloy for Plated Through Holes

Aseries of investigations to reduce the solidus temperature and strength of lead-free solders (by adding indium, which is very ductile) was carried out by NCMS. Beginning with three alloys: (1) Sn-3.5Ag (T_melt=221 ºC), (2) Sn-3Ag-2Bi (T_onset= 216 ºC), and (3) Sn-3.33Ag-4.83Bi (T_onset= 212 ºC). A solder alloy with composition Sn-3.5Ag-5.0In, with addition of either 1 % or 2 % (by mass) Cu was found to reduce the alloy's melting temperature by 5 ºC and also desirably decreased the alloy's strength, reducing the probability of its cracking due to buildup of residual stress during thermal cycling (cooling after a soldering operation).

Source: Technical Reports for the Lead Free Solder Project: Properties Reports: "Solder Alloy Development for Plated Through-Hole Applications: DSC Analyses and Ring-in-Plug Mechanical Tests;" Lead Free Solder Project CD-ROM, National Center for Manufacturing Sciences (NCMS), 1998

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