FIELD OF THE INVENTION

Devices and methods consistent with what is disclosed herein relate to an electronic device comprising a metal case having a metal pad attached thereto, and more particularly, to an electronic device for preventing a terminal provided on a circuit board from being corroded or damaged due to friction with a metal pad by laser welding a metal pad to a metal terminal part provided in a metal case.

Mobile electronic devices comprising a case formed of a pure metal or an alloy material having a relatively low surface hardness such as aluminum, titanium, zinc, magnesium, etc. increase. Such mobile electronic devices achieve high structural rigidity, less weight, and small thickness compared to the conventional electronic devices comprising a case formed of a plastic material. The mobile electronic devices comprising a metallic case have sophisticated texture of metal which is attractive to a user to purchase.

Such mobile electronic devices use a metal case as an antenna or part of an electronic circuit. In this case, the antenna or the electronic circuit may be electrically connected to a circuit board arranged in the electronic device. A contact terminal such as C-clip electrically connected to the antenna or the electronic circuit may be provided on the circuit board. Such the C-clip may be electrically connected to a metal terminal part formed in the part of the metal case.

However, metals such as aluminum, magnesium, titanium, zinc, iron, and stainless steel used as a material of the metal case have a lower hardness and a less corrosion resistance than metals such as gold, silver, platinum, and palladium, which are key materials of the C-clip. Therefore, a metal terminal part has a fine scratch in the part contacting the C-clip, and this part is easily corroded. Due to such corrosion, a conventional electronic device has malfunctions due to the contact failure.

In order to solve the above problem, a metal pad is bonded to a metal terminal part of a metal case to use. The metal pad may have a conductivity and a corrosion resistance, and be formed of a metal material having a high hardness.

Conventionally, various attachment methods have been suggested to attach the metal pad to the metal case, for example, an ultrasonic welding method.

The ultrasonic welding method uses a very thin metal pad, i.e. a metal sheet. In this case, the metal sheet welded to the metal terminal part is formed of a metal material having little or no electric potential difference compared to the C-clip, and prevents galvanic corrosion or fretting corrosion by using a metal having a high hardness. In addition, it can be easier and quicker to manufacture since a metal sheet is physically bonded to a metal terminal part due to friction heat generated by the vibration of the ultrasonic horn.

However, since the head of the ultrasonic horn is interfered with the injection-molded structure in the narrow part of the electronic device, it is difficult to enter the welding part, which makes welding work impossible.

SUMMARY

One technical task of the present disclosure is to provide an electronic device comprising a metal pad formed of a metal material having a conductivity and a corrosion resistance and a high hardness to be smoothly bonded to a metal terminal part regardless of the internal structure of a metal case.

Another technical task of the present disclosure is to provide an electronic device comprising a metal pad smoothly bonded to a metal terminal part regardless of the internal structure of a metal case.

According to an exemplary embodiment, there is provided an electronic device including a metal case having a metal terminal part formed therein, a metal pad bonded to the metal terminal part by laser welding, and a conductive first coating layer coated on one surface of the metal pad, wherein light reflectivity of the conductive first coating layer is lower than light reflectivity of the metal pad.

The first coating layer may be formed of a material having a corrosion resistance.

The metal pad may have a conductive second coating layer coated on the first coating layer.

The second coating layer may have a greater hardness than the first coating layer.

The second coating layer may be formed of a same material as a contact terminal electrically connected to the second coating layer.

The second coating layer and the contact terminal may be formed of one of gold, silver, platinum and nickel-palladium alloy.

The metal pad may be formed of one of copper, titanium, tin, phosphorus and zinc.

The metal pad may include copper and one of titanium, tin, phosphorus and zinc.

The first coating layer may include one of nickel and cobalt.

The second coating layer may be partly formed on a first coating layer.

The second coating layer may be formed of one of gold, silver, platinum, nickel-palladium and gold-cobalt alloy.

The electronic device may further include at least one melting part formed surrounding the metal pad by the laser welding.

The melting part may be formed of a reactant which is formed by melting a part of the metal pad, a part of the first coating layer, and a part of the metal terminal part.

The reactant may have a conductivity.

The electronic device may further include a double-sided tape for attaching the metal pad to the metal terminal part.

The double-sided tape may be attached only to a center portion of the metal pad.

The electronic device may further include a circuit board including the contact terminal, the circuit board being electrically connected to the metal case through the contact terminal.

The contact terminal may be formed in the form of one of a c-clip, a coil spring, and a pin.

The electronic device may further include an antenna or an electronic circuit formed in a metal case, and a molded material combined with an inside of the metal case to partly expose the metal terminal part.

