Application of small angle neutron scattering to analyze precision nickel mesh for electro-magnetic interference shielding formed by continuous electroforming technique

Article abstract of DOI:10.1016/j.physb.2006.05.248

Nickel mesh, as one of the most efficient electromagnetic interference (EMI) shielding materials, has been widely adopted in electronic devices such as plasma display panel (PDP). In this study, the nickel mesh sheet was continuously produced in industrial scale by a unique electrochemical process and which microstructure was analyzed by small-angle neutron scattering and field-emission scanning electron microscopy. The precision nickel mesh sheet was well formed by continuous electro-forming equipment with a rotating patterned cathode, soluble/insoluble anode and multiple stage of rolling wheels. Neutron diffraction analysis and morphology observation showed that the nickel mesh formed by electro-deposition process has less defects for industrial applications.

Full text of DOI:10.1016/j.physb.2006.05.248

ARTICLE IN PRESS
Physica B 385–386 (2006) 914–916
www.elsevier.com/locate/physb
Application of small angle neutron scattering to analyze precision nickel
mesh for electro-magnetic interference shielding formed by continuous
electroforming technique
Ã
Man Kima, , Joo-Yul Leea, Sik-Chol Kwona, Dongsoo Kima, In-Gon Kimb, Yong Choic
aKorea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon, Kyungnam 641 010, Republic of Korea
bDong-eui University, Kaya-Dong, San 24, Busanjin-Ku, Busan 614 714, Republic of Korea
cSunmoon University, Kalsan-Ri, Tangjeoung-Myun, Asan, Chungnam 336 840, Republic of Korea
Abstract
Nickel mesh, as one of the most efficient electromagnetic interference (EMI) shielding materials, has been widely adopted in electronic
devices such as plasma display panel (PDP). In this study, the nickel mesh sheet was continuously produced in industrial scale by a
unique electrochemical process and which microstructure was analyzed by small-angle neutron scattering and field-emission scanning
electron microscopy. The precision nickel mesh sheet was well formed by continuous electro-forming equipment with a rotating
patterned cathode, soluble/insoluble anode and multiple stage of rolling wheels. Neutron diffraction analysis and morphology
observation showed that the nickel mesh formed by electro-deposition process has less defects for industrial applications.
r 2006 Elsevier B.V. All rights reserved.
Keyword: Nickel mesh; Neutron diffraction
1. Introduction
Hence the objectives of this study are to fabricate nickel
mesh sheet in productive scale by continuous electro-
forming equipment and to evaluate hardness and micro-
structure by nano-indentation, small-angle neutron scatter-
ing and field-emission scanning electron microscopy,
respectively.
Fine nickel mesh sheet with the thickness of sub-micron
scale has been widely adopted in electron devices as one of
efficient electromagnetic interference (EMI) shielding
materials [1]. The nickel mesh sheet is usually produced
by batch process in the industry through chemical or
electrochemical process in the nickel ion-containing solu-
tion. Although the batch process has been well applicable
for the production of nickel mesh, a productive method is
required to reduce fabrication cost in industry. In this
study, a unique method using continuous electroforming
process was proposed to produce precision nickel mesh
sheet. Characteristics of the method are based on the
usages of a rotation-patterned cathode, soluble and
insoluble anode, and multiple stage of rolling wheels
during electro-deposition. Since the process method is
novel, it is necessary to verify the final products of nickel
mesh sheet.
2. Experimental method
Fig. 1 is the schematics of the continuous electroforming
process in which a rotating patterned cathode, soluble/
insoluble anode and multiple stage of rolling wheels are
equipped. The electroplating of nickel mesh sheet was
carried out at 100 mA/cm2 in sulfamate solution. Table 1 is
the chemical composition and operating condition of
electroforming. Microstructure of the nickel mesh sheet
was observed by scanning electron microscopy (Jeol JSM-
5400). Small angle neutron scattering was carried out in
HANARO reactor at Korea Atomic Energy Research
Institute. Raw data were analyzed by ILL data treatment
code (Institute Laue-Langevin data code for SANS data
analysis).
Ã
Corresponding author. Tel.: +82 55 280 3543; fax: +82 55 280 3599.
E-mail address: mkim@kmail.kimm.re.kr (M. Kim).
0921-4526/$ - see front matter r 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.physb.2006.05.248

ARTICLE IN PRESS
M. Kim et al. / Physica B 385–386 (2006) 914–916
915
450
400
350
300
250
[NTSA]
0 g/L
1 g/L
2 g/L
3 g/L
200
150
Fig. 1. Schematic diagram of continuous electro-forming process of nickel
mesh sheet.
0
20
40
60
80
100
Current density (mA/cm2)
Table 1
Chemical composition and working condition of nickel electroforming
Fig. 3. Change of hardness of nickel deposit with NTSA concentration
and current densities.
Ni(NH2SO3)2 Á 6H2O
H3BO3
NTSA
445 g/L
36 g/L
0ꢀ3 g/L
1 g/L
Wetting agent
Temperature
pH
55 1C
3.8
Fig. 4. Surface morphology of electroformed nickel prepared in the
electroforming solution in the absence of NTSA (a) and in the presence of
3 g/L NTSA (b).
Fig. 2. Optical (a) and SEM (b) micrographs of electro-formed nickel
mesh by rotating cathode drum at 100 mA/cm2.
Fig. 5 is SANS data and cross-sectional images of nickel
and chromium layers, in which chromium layer was chosen
to compare the microstructure of nickel layer. The
chromium layer was prepared by sulfate bath of trivalent
chromium [3]. As shown in Fig. 5, about 40 nm size defects
were mainly observed in chromium layer that is well
agreement with previous reports, whereas, it is difficult to
observe nano-size defect in the nickel layer [3,4]. Accord-
ingly, SANS clearly says that electroformed nickel sheet
has more defectless structure than electrodeposited chro-
mium. The microstructure of electroformed or electro-
deposited layer is related to nucleation and growth
mechanism on the substrate. Since it is known that current
efficiency of nickel electroforming on cathode is around
95%, whereas, that of chromium is less than 20%, from
electrochemical point of view, the current efficiency
influences hydrogen evolution and makes resultant micro-
structure [5,6]. The nickel mesh sheet with thin and
honeycomb structure like Fig. 2, has homogeneously
distributed residual stress and few defects. This means that
the hardness increase with NTSA is mainly related to grain
size refinement.
3. Results and discussion
Fig. 2 is optical and SEM micrographs of electroformed
nickel mesh on the patterned cathode drum. Fine
honeycomb structure with edge smoothness was well
formed.
Fig. 3 shows the hardness of nickel deposits as a function
of concentration of sodium naphthalene trisulfonic acid
(NTSA) added in the nickel ion-containing solution. The
addition of NTSA enhances the hardness of electrodepos-
ited thin film, particularly when high current density
applied. In case of 3 g/L of NTSA addition, the hardness
becomes about 430 DPH. It is known that the hardness of
electrodeposited layers depends on several parameters such
as residual stress, grain size and microstructure [2].
Fig. 4 is the effect on NTSA on the surface morphology
of electroformed nickel observed by scanning electron
microscopy. As shown in Fig. 4, the grain size decreased
with addition of NTSA. It order to look inside more in
detail, small-angle neutron scattering was applied to
evaluate microstructure of electroformed nickel sheet.

ARTICLE IN PRESS
M. Kim et al. / Physica B 385–386 (2006) 914–916
916
was continuously produced in industrial scale by contin-
uous electroforming process with a rotating patterned
cathode, soluble/insoluble anode and multiple stage of
rolling wheels. Fine honeycomb structure with edge
smoothness was well formed. The hardness of electro-
deposited thin film prepared at high current density applied
of 100 mA/cm2 in the sulfamate nickel solution with 3 g/L
of NTSA addition shows about 430 DPH. Microstructure
analysis of the electroformed nickel sheet by small angle
neutron scattering has that the nickel sheet has less defects
than electrodeposited trivalent chromium layer and proves
that the hardness increase by NTSA addition is related to
grain size refinement.
Acknowledgments
This work was supported by Center for Advanced
Materials Processing (21C Frontier R&D Program) (Grant
no. PS002-5-01-00).
References
[1] T. Kagotani, R. Kobayashi, S. Sugimoto, K. Inomata, K. Okayama,
J. Akedo, J. Magn. Magn. Mater. 290 (2005) 1442.
[2] P. Benaben, Plat. Surf. Fish. 76 (1987) 60.
[3] Y. Choi, J. Mater. Sci. 32 (1997) 1581.
[4] Y. Zhang, G.C. Stangle, J. Mater. Rev. 10 (1995) 962.
[5] Y.B. Song, D.-T. Chin, Electrochim. Acta 48 (2002) 349.
[6] A. Ciszewski, S. Posluszny, G. Milczarek, M. Baraniak, Surf. Coat.
Technol. 183 (2004) 127.
Fig. 5. Small-angle neutron scattering data and cross-sectional SEM
images ( Â 100,000) of nickel (a) and chromium layers (b).
4. Summary
Nickel mesh sheet for electromagnetic interference
(EMI) shielding materials of plasma display panel (PDP)