論文の内容の要旨

氏

名

Fakpan Kittichai

Creep, fatigue and their interaction are considered to be the prevalentmechanism leading to the eventual solder joints fatigue. Although fatigue damage
usually consists of crack nucleation and crack growth, crack growth process isdominant in determining the total fatigue life of a solder joint. Therefore, crack
growth behavior of solder materials under interaction of creep and fatigue isnecessary to clearly understand in order to developing the reliability assessmentof SMT electronic packaging. The objective of the present work is to study thecrack growth behavior under creep-fatigue interaction for Pb-containing (Sn-37Pb)
and Pb-free (Sn-3.0Ag-0.5Cu) solders. Elastic-plastic fracture mechanic parameter,
J-integral

range

(J)

was

used

to

discuss

the

crack

growthbehavior

undercycle-dependent condition. While time-dependent fracture mechanic parameter, C wasused to discuss the crack growth behavior under time-dependent (creep) condition.
Chapter 1: Introduction - A brief introduction on Pb-containing and Pb-free solder
materials, their physical and electrical properties as well as their mechanicalbehavior have been outlined. The results of previous studies on crack growth
behavior of Pb-containing and Pb-free solders have been reviewed to identify theimportant unsolved problems. The scope of the present work has been also presented.
Chapter 2: Effect of frequency and temperature on crack growth behavior of
Pb-containing and Pb-free solders – The transition crack growth behavior of theboth solders from cyclic- to time-dependent was investigated by decreasing thecyclic frequency from 10 Hz to 0.1 Hz and increasing the temperature from room
temperature to 70oC. The experimental results showed that the crack growth behaviorof the both solders tested under the higher frequency and lower temperature waspredominantly cycle-dependent, while the crack growth behavior of both solders
tested

under

the

lower

frequency

andhighertemperature

waspredominantly

time-dependent. The transition temperature from cycle-dependent to time-dependent
crack growth behavior was expressed as: T(K)=30ln f(Hz)+301.

Chapter 3: Effect of hold time on crack growth behavior of Pb-containing and
Pb-free solders - Solder joints are subjected to both static loading under normal
operating condition (switch-on condition) and transient loading by power-on/off
action. Therefore, cyclic loading with hold time would be one of the dominantfatigue loading modes for solder joints in electronic packaging. In Chapter 3, fourtypes of loading waveform were adopted to investigate the effect of hold time on
crack growth behavior of Sn-37Pb and Sn-3.0Ag-0.5Cu solders. The experimental
results showed that the crack growth behavior of both solders tested undersinusoidal

andtriangular

waveformwithout

any

hold

time

was

predominantly

cycle-dependent. While the crack growth behavior of both solders tested undertrapezoidal waveform with hold times of 1, 5 and 10 s and triangular waveform witha hold time of 10 s was predominantly time-dependent. Under cycle-dependentcondition the crack growth data were a function of J, while under time-dependentcondition the crack growth data were not a function of J but rather of the C*
parameter.
Chapter 4: Transient crack growth behavior under variable cycle/time dependentconditions for Pb-containing and Pb-free solders – Crack growth behavior of thesolderjointsintheelectronic

time-dependent

as

well

as

from

packages
time-

to

would

be

changedcycle-dependent

from

when

cycle-

theirtoserviceconditions are changed. Therefore, in Chapter 4, fatigue crack growth (FCG) testsof Sn-37Pb and Sn-3.0Ag-0.5Cu solders were carried out by using six types ofvariable

cycle/time

dependent

conditions

underconstant

Jloading.

The

experimental results indicated that acceleration of crack growth rate was induced
when the C* value for the prior loading condition was high regardless of timedependent or cycle dependent crack growth for both Sn-37Pb and Sn-3.0Ag-0.5Cu
solders. The creep damage zone size of both the solders could be estimated by thecreep zone size under assumption of creep zone definite by Riedel-Rice.
Chapter 5: Conclusion - The general conclusion and future prospects have been
discussed and summarized.