Thermal Expansion Properties of Invar Alloy Electrodeposits

Abstract

インバー合金電析膜の熱膨張特性 山本 貴代Thermal expansion properties of Invar (Fe-36 mass%Ni) alloy electrodeposits were investigated. The Fe-36 mass%Ni alloy electrodeposits from sulfate/chloride electrolytes using additives, saccharin sodium, and malonic acid. The electrodeposits, of about 150 μm thickness, had no crack. The thermal expansion curve showed that contraction of the electrodeposits occurred in the 270-420 ℃ range during first heating. During the first cooling and second heating, it showed the same behavior as that of melted Invar alloy. The coefficient of thermal expansion α (CTE) exhibited approximately α＝10×10 -6 /℃ for the as-deposited electrodeposits and approximately α＝1×10 -6 /℃ for electrodeposits annealed above 500℃ . The CTEs of the electrodeposits annealed above 500 ℃ showed excellent agreement with that of the melted Invar alloy. The decrease in the CTE resulted from the increase of the fcc phase in the electrodeposits caused by heat treatment.Invar alloy electrodeposits are anticipated for application to high-definition electroformed products with low CTEs. Keywords

37‐3: Low Thermal Expansion and Fine‐Pitch Metal Masks Fabricated via Invar Fe‐Ni Alloy Electroforming for Large Fine‐Pitch OLED Displays

“…The CTE of the electroformed Fe-Ni alloy metal mask after annealing was approximately 3 ppm/°C and was four times less than that of the conventional electroformed Ni and Ni-Co alloys. We propose that the reduction of the CTE of the electroformed Fe-Ni alloy metal masks after annealing was because of the phase transition from bcc to fcc, as reported in references [4], [5], and [7-9].…”

“…For the temperature range between 300 °C and 400 °C, the Fe-Ni alloy electroformed metal mask had a negative CTE. This phenomenon was considered to be caused by an increase in the atomic packing density (contraction) because of a phase transformation from metastable body-centered cubic (bcc) phases to equilibrium face-centered cubic (fcc) phases [4,5,[7][8][9] and reduction of the defects (contraction) because of the recrystallization of the Fe-Ni alloy electroformed metal mask by heating [4,5,7]. Furthermore, for temperatures above 400 °C, a rapid increase in the length of the specimen was detected.…”

“…A process for producing crack-free invar Fe-36 mass% Ni alloy electrodeposits with lower CTEs than those of conventional Ni and Ni-Co alloys has been reported in previous studies [3][4][5]. Furthermore, coarse (the open area was 80 × 80 μm 2 ) and thick (approximately 80 μm thickness) Fe-Ni alloy masks with low CTEs have been fabricated via electroforming [6]; however, the sizes of the open areas and thickness of such metal masks are unsuitable for fabricating fine-pitch OLED displays.…”

Fabrication of Low CTE Metal Masks by the Invar Fe-Ni Alloy Electroforming Process for Large and Fine Pitch OLED Displays

“…For a temperature range of 573 to 673K, the Fe-Ni alloy electroformed metal mask had negative CTEs. It is considered that this phenomenon originates in increase of the atomic packing density (contraction) by the phase transformation from bcc phases to fcc phases (4,6,7,8) and reduction of defects (contraction) by a recrystallization of the Fe-Ni alloy electroformed metal mask by heating (4,6). Furthermore, for above 673K, rapid increase of the length of the specimen was measured.…”

P‐72: Invar Fe‐Ni Alloy Metallization by Electroless Plating for TFTs

“…In the invar composition range, the CTE of the pyrometallurgically produced Fe-Ni alloys were exhibited lower values for the equilibrium fcc phase [14]. In addition, we have reported that in the electrodeposited Fe-Ni alloy with 36-42 wt% Ni the heat treated deposits were transformed from metastable bcc phases to equilibrium fcc phases and had lower CTEs than the as-deposits [13,[15][16]. While the electroless deposited Fe-36 wt%Ni alloy film have a moderate CTE for ceramics, the CTE was higher than that of a pyrometallurgically produced Fe-36 wt%Ni alloy ; this can probably be attributed to the fact that the alloy phase of the electroless deposited films obtained included a bcc phase.…”