23P001-O
Development of Multi Wire Stripper with Line-shaped Magnetron Plasmas
同軸マグネトロンプラズマを用いたマルチワイヤストリッパー装置の開発
Y. Kobayashi1, N. Matsuo1, K Miyazaki2, S. Nishiyama3, M. Shinohara and H. Fujiyama2
小林祐介 1，松尾直志 1，宮崎清志 2，西山新一郎 3，篠原正典 2，藤山 寛 2Graduate School of Science and Technology1, Graduate School of Engineering2, Nagasaki University.,
Japan Fine Steel CO., Ltd.3
長崎大院生産 1，長崎大院工 2，ジャパンファインスチール 3
To remove brass plating on saw wire used for cutting down a silicon wafer, the new type of multipleline-shaped magnetron plasma developed. This new-type plasma was characterized. The plasma has atypical characteristic to magnetron plasma; the character of discharge current density was proposed to B 2,
V3/2 and P2.

1. Introduction
Silicon wafer used as a substrate of crystal
silicon solar cells is carved out from the siliconingot by fine wire. Figure 1 showed cross section offine wire. The fine wire is covered with brass (Cu:65%, Zn: 35%) plating to need in wire drawing
process. The copper diffused in the silicon wafer
during cutting process is caused to becontamination. So the electric conductivity changes,and there is a possibility of cause to decrease solar
cell efficiency. Therefore Cu-free fine wire isstrongly required.
Now, the wet electrochemical process byammonia and hydrochloric acid has been used forremoving
thebrass
plating.
Thewetelectrochemical process requires large currents. The
processes also have high environmental loads, andhigh cost for waste liquid treatment. On the other
hand, the dry processes have been low
environmental loads and low cost.
The aim of this study is to remove brass plating
on fine wires by the newly developed multiple
line-shaped magnetron plasmas with the multiple
electrode system.

shows the multiple unit system for magnetronplasmas. Wire setting time could be made short by
the simplification of electrode system.

BFig.2 Multiple Electrode System
The electrode system of multiple plasma sources
is shown in Fig.3. Plasma could be generated byapplying negative DC voltage to the 6 wires against
the grounded inner electrode and the outer electrodewith axially applied magnetic field.
Six wires with 0.25mm in diameter were set,
evenly-spaced apart from each other. The gap
length from both electrodes was set to 11 mm. The
surface of wire after plasma treatment wasdetermined the mass percentage of residual copperby using EDS (Energy Dispersive X-raySpectroscopy).
Table.1 Experimental Condition

BrassFe

Fig.1 Cross Section of Fine Saw Wire

2. Experimental
At first, figure 2 shows the single unit forremoving brass plating on wire. Many wires could
be removed it with multiple unit systems. Figure 2

SUS Tube Diameter [mm]Wire Diameter [mm]Gap Length [mm]GasGas Pressure [Pa]Gas Flow Rate [sccm]
Discharge Voltage [V]150.25
11Argon0.325-600 ~ -800

InnerElectrodeCeramic

Wire
Wire
Negative DCVoltage

Fig.3 Electrode Systems

3. Experimental Results
Figures 4-6 show the dependences of magnetic
flux density, discharge voltage and gas pressure ondischarge current, respectively. The experimental
conditions shown in Table 1. In magnetizeddischarge plasmas, the discharge current density canbe applied to the following empirical formulas. [1]J a  A(aP2  bB2 )(Vd V0 )3/ 2[1]

Here, P, B, and Vd-V0, indicate gas pressure,magnetic flux density, and discharge voltage,respectively. This formula showed the discharge
23/ 22current density increases, with B , V , P . The
newly-developed multiple line-shaped plasma has
the same characteristics. Then, the plasma can be acharacteristic to magnetron plasmas.

10189Gauss
252Gauss
315Gauss
378Gauss
441Gauss
504Gauss
567Gauss
630Gauss

31500

600

700

800

Negative DC Voltage [V]Fig. 5 Dependence of Discharge Voltage
on Discharge Current Density

Discharge Current Density [mA/cm2]

SpringDischarge Current Density [mA/cm2]

OuterElectrode10310.3
0.1

0.3

1

Discharge Current Density [mA/cm2]

Pressure [Pa]10Fig. 6 Dependence of Gas Pressure
on Discharge Current Density

3600V
650V
700V
750V
800V

1200300 400

Magnetic Flux Density [Gauss]
Fig. 4 Dependence of Magnetic Flux Density
on Discharge Current Density

4. Conclusion
Line-shaped multiple magnetron plasmas could
be generated by new type of electrode system. The
discharge current is proportional to magnetic flux
density B2, discharge voltage V3/2 and gas pressure
P2, respectively. Stripping results of brass plating
wire by the present plasma stripper will be reported.
Acknowledgments
This work has been supported in part by theregional innovation creation research anddevelopment business in MEXT.
Reference[1] K. Kuwahara and H. Fujiyama: IEEE Trans. onPlasma Science, Vol.22, No.4, pp.442-448 (1994).