1. Technical Field
The present disclosure relates to a multi-film structure, a method for making the multi-film structure, and an electronic device having the multi-film structure.
2. Description of Related Art
With the development of individuation of electronic devices, consumers have higher requirements for the appearance of the electronic devices. Therefore, besides the function, shape and color of the electronic devices are also important in attracting consumers. However, housings of the electronic devices are generally made of metal or plastic, the color of which is limited and tedious.
Therefore, it is desirable to provide a multi-film structure and a method for making the multi-film structure, which can overcome the above-mentioned limitations.
Referring to
The substrate 10 may be a shell of a portable electronic device. The substrate 10 may be made of materials such as metal, or plastic. In the present embodiment, the substrate 10 is made of stainless steel. The substrate 10 includes a first bottom surface 101 and a first surface 102.
The chromium nitride film 20 is formed on the first surface 102 of the substrate 10. The chromium nitride film 20 includes a second bottom surface 201 and a second surface 202. The second bottom surface 201 is in contact with the first surface 102 of the substrate 10.
A molecular formula of the chromium nitride is represented by CrNx, and x is larger than 0 and less than 1. The chromium nitride film 20 is for enhancing the adhesion between the color layer 30 and the substrate 10.
The color layer 30 is formed on the second surface 202 of the chromium nitride film 20. The color layer 30 is an aluminum oxide film doped with chromium atoms. The weight percent of the chromium in the color layer 30 is less than that of the aluminum in the color layer 30. The multi-film structure 100 shows different colors depending on the weight percentage of the chromium in the color layer 30 and the thickness of the color layer 30. A molecular formula of the aluminum oxide film mixed with chromium atoms may be Al2O3:Cr.
Referring to
Referring to
In step 110, the substrate 10 is provided. The first surface 102 of the substrate 10 may be roughened, or smoothed.
In step 120, the chromium nitride film 20 is formed on the first surface 102 of the substrate 10 using reactive magnetron sputtering.
The reactive magnetron sputtering is performed in a reactive magnetron sputtering device (not shown). The reactive magnetron sputtering device includes a chamber. Before depositing the chromium nitride film 20, the substrate 10 is placed in the chamber, the chamber is then vacuumized and a working pressure of the chamber is kept at a stable value. In the present embodiment, the working pressure is about 4.1 millitorr.
Additionally, the chamber may be cooled using a condenser (not shown) during the process of vacuumizing to enhance the efficiency of vacuumizing. In this embodiment, a condensing temperature of the condenser is set to be about −135° C. After the chamber is vacuumized, the chamber may be heated to a required temperature.
Then, a chromium target is placed in the chamber, a first magnetic field and a first electrical field are applied between the chromium target (a first cathode) and the substrate (an anode), and a mixed gas of nitrogen and argon is continually introduced into the chamber during the coating of the chromium nitride film 20. The first magnetic field is orthogonal with the first electrical field. The nitrogen serves as reactive air, and the argon serves as working air. In the first electrical field, the argon is ionized to argon ions and electrons, argon ions are accelerated to strike on the chromium target, a number of chromium atoms escape from the chromium target, the chromium atoms react with the nitrogen to form chromium nitride. The chromium nitride is deposited on the first surface 102 of the substrate 10, thus forming the chromium nitride film 20.
In step 130, the color layer 30 is deposited on the second surface 202 of the chromium nitride film 20 using reactive magnetron sputtering.
After the chromium nitride film 20 is done, the chromium target is turned off, the mixed gas of nitrogen and argon is shut off, and the chamber is vacuumized. Before vacuumizing the chamber, the chamber may be cooled using a condenser (not shown). In the present embodiment, the condensing temperature of the condenser is set to be about −135° C. During the process of forming the color layer 30, a working pressure of the chamber is kept at a stable value.
Then, an aluminum target is placed in the chamber, a second magnetic field and a second electrical field are applied to the chromium target (the first cathode) and the substrate 10 (the anode), and a third magnetic field and a third electrical field are applied to the aluminum target (the second cathode) and the substrate 10 (the anode). The second magnetic field is orthogonal with the second electrical field, and the third magnetic field is orthogonal with the third electrical field. Subsequently, a mixed air of oxygen and argon is continually introduced to the chamber in the deposition of the color layer 30. The oxygen serves as reactive air, and the argon functions as working air. In the second and third electrical fields, the argon is again ionized to argon ions (with positive charge) and electrons. The argon ions are accelerated to strike to chromium target and the aluminum target, releasing a lot of chromium atoms and aluminum atoms. The aluminum atoms react with the oxygen to form aluminum oxide, and accordingly, the aluminum oxide film doped with chromium atoms is deposited on the second surface 202 of the chromium nitride film 20, thus forming the color layer 30.
In order to achieve that the weight percentage of aluminum atoms in the color layer 30 is greater than that of chromium in the color layer 30, power supplied to the aluminum target should be larger than that supplied to the chromium target. In one embodiment, the power fed to the aluminum target is about 30 kilowatt (KW), and the power supplied to the chromium target is about 0.4 KW.
The multi-film structure 100 shows different colors depending on the weight percent of the chromium and the thickness of the color layer 30. The weight percent of the chromium is mainly determined by the power supplied to the chromium target and the aluminum target. The thickness of the color layer 30 is mainly decided by the time of coating.
In the present embodiment, during the deposition of the chromium nitride film 20 and the color layer 30, the substrate 10 is driven to rotate around a central axis of the chamber, and simultaneously, to rotate around a central axis thereof so that uniformity of the chromium nitride film 20 and the color layer 30 is improved. A revolution speed (i.e., the speed of the rotation around the central axis of the chamber) of the substrate 10 is about 2 revolution per minute (RPM), and a rotation speed (i.e., the speed of the rotation around the central axis around the substrate 10) of the substrate is about 8 RPM.
Referring to
While various embodiments have been described, it is to be understood that the disclosure is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art), are also intended to be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Number | Date | Country | Kind |
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99111067 | Apr 2010 | TW | national |