Thermal Expansion and Thermal Stress Behavior of Electroless-Plated Fe–Ni–B Alloy Thin Film for High-Density Packaging

Abstract

Fe-Ni-B alloy thin films were prepared by using an electroless plating method, and their thermal-expansion behavior, thermal-stress generation, and crystal structure were evaluated. By heating from 30 • C to 300 • C, the electroless-plated Ni-5 wt%B alloy film showed a marked increase in tensile stress at approximately 270 • C, which is caused by a phase separation from the amorphous Ni-B alloy into a highly crystalline Ni and Ni 3 B compound. The coefficient of thermal expansion (CTE) of electroless-plated Ni-B alloy film from 300 • C to 30 • C, after heating to 300 • C, was 14 ppm/K. In contrast, the electroless-plated Fe-Ni-B alloy film in the Invar composition range had a small CTE (8 ppm/K to 9 ppm/K) and no substantial change in crystal structure during heating to 300 • C. As a result, the Fe-Ni-B alloy film on the silicon substrate (CTE = 3 ppm/K) exhibited a low thermal stress compared with the electroless-plated Ni-B alloy film. Thus, it is suggested that the electroless-plated Invar Fe-Ni-B alloy films are suitable as an under-bump metal layer from the viewpoint of the thermal-expansion behavior.

Regulation of the Concentration Heterogeneity and Thermal Expansion Coefficient in the Metastable Invar FeNi31.1 Alloy

“…In particular, the thermal expansion coefficient (TEC) growth in the Invar FeNi 35 alloy is observed after the high-energy electron and ion irradiation due to the short-range ordering development [ 6 , 14 , 15 ]. The concentration heterogeneity in alloys can be controlled in terms of deformation and thermal-induced structure-phase transformations [ 16 , 17 , 18 , 19 , 20 ]. For instance, metastable Fe–Ni alloys from the Invar range of 30–34 at.% of Ni appeared to have an active Ni redistribution under the heating rate variation in terms of polymorphic α→γ transformation with a further development of austenite with a concentration heterogeneity [ 19 ].…”

Noncontact and Full-Field Measurement of Residual and Thermal Stress in Film/Substrate Structures

“…For example, hard coatings have tensile stress that can lead to cracking and compressive stress can lead to buckling, blistering, and delamination [2]. In addition, stress evolution due to temperature change or thermal cycling is difficult to identify in thin film in electronic packages [3,4] or thermal barrier coatings [5][6][7]. Various research strategies to tailor and control the stress state are currently being devised, which has generated intense research and innovation activity over the last few decades related to the measurement of stress state in thin films.…”

Preparation and Characterization of Electroless Deposited Fe-Ni-B Alloy Films

“…We have prepared Fe-Ni-boron (B) alloy thin films using the electroless plating method, and their thermal stress behavior has been evaluated (3). The results suggest that the thermal stress behavior is related to CTE and the crystal structure.…”

“…In this study, in addition to the previous work (3), in which Ni-B and Fe-Ni-B alloys with Fe contents of 55 and 63 wt% were studied, Fe-Ni-B films with Fe contents from 10 to 40 wt% were prepared. Herein, for the Fe-Ni-B films with a wide alloy composition ratio, their stress generation, thermal-stress, thermal-expansion behavior, and crystal structure were investigated.…”