Transcript Document
Transient Liquid Phase Bonding as a Potential Substitute for Soldering with High-Lead Alloys A.A. Kodentsov
Laboratory of Materials and Interface Chemistry, Eindhoven University of Technology, The Netherlands
•
There is still no obvious (cost-effective) replacement for high-lead , high melting ( 260 320
C) solder alloys • It is not possible to adjust (to increase above 260
C) liquidus temperature of any existing Sn based solder alloys by simple alloying with environmentally friendly and inexpensive elements • Therefore, in the quest for (cost-effective) replacements of the high-lead solders , attention has to be turned towards different base metals as well as the exploration of alternative joining techniques !
Liquidus projection of the Zn-Al-Mg system Ternary eutectic at ~ 343
C
The binary Bi – Ag phase diagram
solid Transient Liquid Phase (TLP) Bonding solid interlayer(s) solid • The interlayers are designed to form a thin or partial layer of a transient liquid phase (TLP) to facilitate bonding via a brazing-like process in which the liquid disappears isothermally • In contrast to conventional brazing, the liquid disappears, and a higher melting point phase is formed at the bonding temperature
solid Transient Liquid Phase (TLP) Bonding solid T = const liquid solid solid solid T = const Diffusion, Reaction solid solid product solid Any system wherein a liquid phase disappears by diffusion, reaction (amalgamation), volatilization, or other processes is a candidate for TLP bonding !
The effect of Ni additives in the Cu-substrate on the interfacial reaction with Sn
The binary Cu – Sn phase diagram
The binary Cu – Sn phase diagram 215
C
Diffusion zone morphology developed between Cu after reaction at 215
C in vacuum for 225 hrs and Sn
In the
-Cu
6
Sn
5
:
J Sn J Cu
D Sn D Cu
V Cu V Sn
1.6
Reaction zone developed between Sn and Cu 1at.% Ni alloy after annealing at 215
C for 400 hrs
pores !!!
Reaction zone developed between Sn and Cu 5at.% Ni alloy after annealing at 215
C for 400 hrs No pores !!!
No
-Cu 3 Sn was detected!
Isothermal sections through the Sn-Cu-Ni phase diagram P. Oberndorff, 2001 C.H. Lin, 2001 235
C 240
C
215
C; 1600 hrs; vacuum
The binary Cu – Sn phase diagram
Part of the Cu-Sn phase diagram in the vicinity of the
/ transition Simple Superlattice Long-Period Superlattice
Cu5Ni Sn Cu5Ni Sn Ag Sn Cu5Ni 250
C 250
C Cu5Ni Cu5Ni (Cu,Ni) 6 Sn 5 Kirkendall plane (s) Cu5Ni (Cu,Ni) 6 Sn 5 (Cu,Ni) 6 Sn 5 Cu5Ni
Binary phase diagram Ni-Bi 250
C
250
C; 200 hrs; vacuum
250
C; 200 hrs; vacuum
Ni Bi Ni Bi Ag Bi Ni 280
C 280
C Ni Ni NiBi 3 Kirkendall plane (s) NiBi 3 Ni NiBi 3
Concluding Remarks
• It is not possible to adjust and inexpensive elements (to increase above 260
C) liquidus temperature of any existing Sn-based solder alloys by simple alloying with environmentally friendly • Therefore, in the quest for (cost-effective) substitutes high-lead solders , attention has to be turned towards different base metals as well as the exploration of alternative joining techniques !
for • Through the judicious selection of Sn- or Bi-based interlayer between under bump metallization and substrate pad, (cost-effective) Transient Liquid Phase (TLP) Bonding can be achieved at ~ 250-280
C, and the resulting joints are capable of service at elevated temperatures !
• The TLP Bonding should be taken into further consideration as substitute for the high-lead soldering !
Diffusion zone morphology developed between Cu after reaction at 215
C in vacuum for 225 hrs and Sn
Parabolic growth of the Cu-Sn intermetallic layers in the binary diffusion couples at 215
C 1.58 x 10 -16 m 2 /s 7.55 x 10 -17 m 2 /s
Diffusion zone morphology developed between Cu after reaction at 215
C in vacuum for 225 hrs and Sn
N B
Determination of the ratio of intrinsic diffusivities species in line-compounds
of S
N i
N B
P R
N i
N B J B J A
x
x K
D B V A D A V B
N B
N
A
P V m
P V m
R V m
R V m
N B
N
A
S V m
S V m
Diffusion zone morphology developed between Cu after reaction at 215
C in vacuum for 225 hrs and Sn
In the
-Cu
6
Sn
5
:
J Sn J Cu
D Sn D Cu
V Cu V Sn
1 .
6
The Cu 3 Ti – type lattice ( oP 8 ), the basic structure of the long-period superstucture of the
-Cu 3 Sn The hexagonal analog of L1 2 -structure of Cu 3 Au !
Ti Cu View down [010] Cu Ti
The basic structure ( oP 8 ) The hexagonal analog of the Cu 3 Au!
• Sn has 12 Cu NN c 0 b 0 • Cu has 4 Sn and 8 Cu NN a 0 • There are no Sn - Sn NN • In the Long-Period Superstructure of
-Cu 3 Sn ( ( a=2a 0 ; b=10b 0 ; c=c 0 ) oC80 ) antiphase shifts occur at every fifth period along the b 0 -axis Projection onto (001) plane
“The ordered Cu 3 Au rule”
L1
2 - type structure ( A 3 B ) • The nearest neighbour (NN) arrangement of A -atoms • The nearest neighbour arrangement of B -atoms
Reaction zone developed between Sn and annealing at 215
C for 400 hrs Cu after
markers !!!
Reaction zone developed between Sn and annealing at 215
C for 400 hrs Cu after
Reaction zone developed between Sn and Cu 1at.% Ni alloy after annealing at 215
C for 400 hrs
pores !!!
Reaction zone developed between Sn and Cu 5at.% Ni alloy after annealing at 215
C for 400 hrs No
-Cu 3 Sn was detected!
Isothermal sections through the Sn-Cu-Ni phase diagram P. Oberndorff, 2001 C.H. Lin, 2001 235
C 240
C
Reaction zone developed between Sn and Cu 1at.% Ni alloy after annealing at 215
C for 400 hrs
Isothermal section through the Sn-Cu-Ni phase diagram at 235
C.
(P. Oberndorff, Ph. D. Thesis, Eindhoven University of Technology, The Netherlands, 2001) Cu 1at.% Ni
Isothermal section through the Sn-Cu-Ni phase diagram at 240
C.
(C.H. Lin, Master Thesis, National Tsing-Hua University, Republic of China, 2001) Cu 1at.% Ni
Reaction zone developed between Sn and Cu 5at.% Ni alloy after annealing at 215
C for 400 hrs
Isothermal section through the Sn-Cu-Ni phase diagram at 235
C.
(P. Oberndorff, Ph. D. Thesis, Eindhoven University of Technology, The Netherlands, 2001) Cu 5at.% Ni
Isothermal section through the Sn-Cu-Ni phase diagram at 240
C.
(C.H. Lin, Master Thesis, National Tsing-Hua University, Republic of China, 2001) Cu 5at.% Ni
Diffusion zone morphology developed between Cu after reaction at 215
C in vacuum for 225 hrs and Sn
In the
-Cu
6
Sn
5
:
J Sn J Cu
D Sn D Cu
V Cu V Sn
1 .
6
215
C; 1600 hrs; vacuum
The binary Cu – Sn phase diagram
The NiAs- type lattice the basic structure of the
-Cu 6 Sn 5 hP 4 tetrahedral hole octahedral hole trigonal hole
Ni As Pictorial view of the NiAs ( hP4 ) structure
A C A B A C A B A Pictorial view of the NiAs ( hP4 ) structure • Ni has 6 As NN • As is surrounded by 6 Ni • The As octahedra share faces normal to the c-axis • The Ni-atoms are direct neighbours along [001] direction
• The composition “Cu 6 Sn 5 ” is achieved by adding additional Cu-atoms in one tenth of the tetrahedral interstices in the hexagonal Sn-sublattice Cu Sn
1. Ordering of the excess Cu interstices results in the -atoms in the tetrahedral
/ - Long-Period Superlattice Cu Sn
Cu 2. The excess Cu-atoms occupy the tetrahedral interstices at random a 1 c a 2 Sn Type
A
c/
2 Type
B
• An arrangement of the unit cells along the three principle axes in the sequence
ABABAABABA
supercell of the
/ -phase … results in the
215
C
/ - Cu 6 Sn 5
Binary phase diagram Ni-Bi 250
C
250
C; 400 hrs; vacuum
250
C; 400 hrs; vacuum
0.9
Liquidus surface 1 Ag 0.7
0.8
0.5
x( A g) 0.3
0.4
0.6
LIQUID 0.2
0.2
Ni x(Bi) x(Bi) FCC_A1 LIQUID BINI BI3NI Bi
0.9
250 C 1 Ag 0.7
0.8
0.5
x( A g) R 0.3
O M B 0.2
O _ A 7 + B I3 N I+ FC C _ A 1 0.2
0.4
0.6
Bi BI3NI+BINI+FCC_A1 x(Ni) x(Ni) FCC_A1+BINI+FCC_A1 Ni
0.9
268 C 0.7
0.5
x( A g) B I3 N I+ F C C _ A 1 + LI Q U ID 0.6
0.8
0.3
0.4
1 Ag 0.2
LIQUID+BI3NI 0.2
BI3NI+BINI+FCC_A1 Bi LIQUID+BI3NI+RHOMBO_A7 x(Ni) x(Ni) FCC_A1+FCC_A1+BINI Ni
268 C LIQUID+FCC_A1+BI3NI LIQUID LIQUID+BI3NI LIQUID +RHOMBO_A7 LIQUID+BI3NI+RHOMBO_A7 Bi x(Ni) x(Ni)
Reaction zone developed between Sn and Cu 5at.% Ni alloy after annealing at 215
C for 400 hrs
The reaction zone developed in the incremental based on Cu and
Cu 6 Sn 5 (215
C; 225 hrs) couple “Unstable” Kirkendall plane ?
The Cu 3 Ti – type lattice ( oP 8 ), the basic structure of the long-period superstucture of the
-Cu 3 Sn The hexagonal analog of L1 2 -structure of Cu 3 Au !
Ti Cu View down [010] Cu Ti
The basic structure ( oP 8 ) The hexagonal analog of the Cu 3 Au!
• Sn has 12 Cu NN c 0 b 0 • Cu has 4 Sn and 8 Cu NN a 0 • There are no Sn - Sn NN • In the Long-Period Superstructure of
-Cu 3 Sn ( ( a=2a 0 ; b=10b 0 ; c=c 0 ) oC80 ) antiphase shifts occur at every fifth period along the b 0 -axis Projection onto (001) plane