ISSN 1063-7397, Russian Microelectronics, 2009, Vol. 38, No. 5, pp. 345–353. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © V.V. Zenin, V.I. Baiko, O.V. Marchenko, V.I. Frolov, O.V. Khishko, 2009, published in Mikroelektronika, 2009, Vol. 38, No. 5, pp. 381–390.
At present, specialists engaged in manufacturing
microelectronics pay detailed attention to lead-free solder-
ing [1–4]. This is due to the European Directive on the
restriction of the use of certain hazardous substances in
electrical and electronic equipment (RoHS), which took
effect on 1 July 2006 [5, 6]. Lead is one of the hazardous
metals, whose applications are regulated by the RoHS.
In developing soldered constructions (assemblies),
including semiconductor products and their manufactur-
ing technologies, designers and technologists take into
account the physical and mechanical properties of materi-
als and material-based solders, the physical and chemical
stability of solders, and their compatibility with coatings
to be soldered. The physical and mechanical properties are
melting point (temperature), tensile strength, yield stress,
elongation (plasticity), Young’s modulus, expansion coef-
ﬁcient, thermal conductivity, resistivity, etc.
When solving the problem concerning the reliability of
soldered joints of speciﬁc semiconductor devices, it is nec-
essary to choose properly the compositions and properties
of solders, the coatings being soldered, as well as the opti-
mal techniques and modes of soldering.
In this section, in terms of foreign scientiﬁc and engi-
neering information, we analyze solders used in manufac-
turing microelectronics. As lead-free solders we consider
alloys on the basis of tin with additions of Ag, Cu, Bi, and
Zn, as well as other metals. Such alloys as Sn–Ag and Sn–
Ag–Cu (Sn 95–96.6/Ag 2.5–4.1 Ag/Cu 0.9) stand out for
reliability. Many researchers recommend (for a start)
studying and introducing into practice these solders .
Their main disadvantage is a comparably high melting
) affecting semiconductor devices
themselves and the substrate. Reducing the melting tem-
perature of these solders can be made by adding Bi, Zn,
and other metals to them. Options for introducing ele-
ments to improve the technological properties of these sol-
ders in Sn–Bi and Sn–Zn compositions are considered.
The Sn 95.5/Ag 4/Cu 0.5 alloy has shown good results.
Its high melting point (
) makes it ideal for soldering
products operating at a temperature lower or equal to
. In some studies, it has shown better strength to
variable temperature than was done by a Sn–Ag alloy
For lead-free soldering, alloys of tin with copper, sil-
ver, bismuth, indium, and zinc can be used. A zinc–bis-
muth alloy with a small content of bismuth is lightly more
expensive than a zinc alloy and has a low melting point
Work  suggests a lead-free alloy, namely, Sn 81–
91/Ag 3–6/Cu 0.1–2, for connecting (bounding) elec-
tronic elements to ensure higher strength to thermal
In the assembly of large dies (chips), a signiﬁcant dif-
ference in the thermal expansion coefﬁcient between Si, a
copper frame, and a laminate (plastic ﬁller) results in large
stress and the distortion of the laminate (plastic). Stress
generated over the contact surface (interface) between a
joint and ﬁlling mass is a result of humidity.
For fatigue tests of component joints in the form of a
rectangular wafer with four-edge forward-bent leads, a
special technique is developed . The Sn 96.5/Ag 3.5
and Sn 91.5/Ag 3.5/Bi 5 alloys are used as solders.
As solders, the following three- or four-component
alloys are used: Ag 55–60 /Cu 25–30/Cu 20–30/Zn 20–26,
Ag 44–48/Cu 32–3/Sn 18–22, Ag 15–20/Cu 28–32/Cd
51–54, Ag 40–45/Cu12–15/Cd29–33/Zn 9–11, and Ag
63–68/Cu 12–16/Sn 11–15/Zn 6–9 . Due to a high
Lead-Free Alloy Soldering of Dies
V. V. Zenin
, V. I. Baiko
, O. V. Marchenko
, V. I. Frolov
, and O. V. Khishko
Voronezh State Technical University, Moskovskii pr. 14, Voronezh, 394026 Russia
JSC Voronezh Semiconductor Plant–Assembly, Voronezh, Russia
Received february 18, 2009
—Information of lead-free solder compositions and melting points, which can be used in the assembly
procedures of microelectronic assemblies (parts), is given. Coatings of dies and package bodies for lead-free
soldering are considered. The features of lead-free soldering of dies are analyzed in terms of documentations
as well as the procedures and modes of soldering of silicon dies to package bodies are considered.