Intermetallic growth and mechanical behavior of low and high melting temperature solder alloys

Journal Article · Fri Jul 01 04:00:00 EDT 1994 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02665483· OSTI ID:7277880

Frear, D R; Vianco, P T ^[1]

---

1. Sandia National Lab., Albuquerque, NM (United States)

The presence of an intermetallic is often an indication of good wetting in a solder joint. However, excessive intermetallic growth and the brittleness of the intermetallic layer may be detrimental to joint reliability. This study examined the growth and mechanical behavior of interfacial intermetallics between copper and six solder alloys commonly used in electronics assembly. The solder alloys tested were 60Sn-40Pb, 63Sn-37Pb, 95Sn-5Sb, 96.5Sn-3.5Ag, 50Pb-50In, 50Sn-50In, and 40In-40Sn-20Pb. The 50Sn-50In and 40In-40Sn-20Pb exhibited faster solid state growth of the intermetallic layer at 100 C as compared to the near-eutectic Sn-Pb control solder. The 50In-50Pb had a slower growth rate, relative to 63Sn-37Pb, at the aging temperature of 170 C due to slower reaction rate kinetics of indium with copper. The 96.5Sn-3.5Ag and 95Sn-5Sb had similar intermetallic growth rates at 170 C and 205 C, and the aging was comparable to that of the 63Sn-37Pb alloy. The 95Sn-5Sb solder/copper intermetallic had a faster growth rate of the Cu[sub 3]Sn layer than was observed in the Sn-Ag or Sn-Pb alloys. Modified fracture toughness and low load indentation tests were used to characterize the mechanical behavior of the intermetallics. The intermetallics were harder than both the base metal and the solder alloy. The fracture behavior of the joints in tension was dependent upon the strength of the solder alloy. Solders with low strengths failed in the solder by plastic deformation. The failure of solders with higher strengths was dependent upon intermetallic thickness. When the intermetallic was thin, fracture occurred in the solder or at the solder/intermetallic interface. As the interfacial intermetallic thickened, the fracture path moved into the intermetallic layer.

• DOE Contract Number: AC04-94AL85000
• OSTI ID: 7277880
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 25:7; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ANTIMONY ALLOYS
COPPER
CRYSTAL GROWTH
ELECTRONIC EQUIPMENT
ELEMENTS
EQUIPMENT
FABRICATION
FILLER METALS
FRACTURE PROPERTIES
INDIUM ALLOYS
INTERFACES
INTERMETALLIC COMPOUNDS
JOINING
JOINTS
LEAD ALLOYS
MECHANICAL PROPERTIES
METALS
RELIABILITY
SILVER ALLOYS
SOLDERED JOINTS
SOLDERING
TIN ALLOYS
TRANSITION ELEMENTS
WELDING