Patent Application
20070234539
These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. In the drawings, the thicknesses of layers and regions are exaggerated for clarity.
Hereinafter, a method of manufacturing a capacitor embedded in a PCB according to an embodiment of the present invention will be described in detail with reference to the drawings:
Referring to
Meanwhile, a surface of the CCL substrate 110, that is, a surface of the copper foil 112, has surface defects such as a convex defect and a concave defect, depending on a surface state of the reinforcement member 111 which comes in contact with the surface of the copper foil 112.
These surface defects increase a leakage current of the embedded capacitor, degrading the characteristic and reliability of an embedded capacitor PCB. In addition, the surface defects serve as a factor causing defects in a dielectric layer and a top electrode, which will be described below, resulting in reduction of a manufacturing yield.
As described above, because the surface defects of the CCL substrate 110 greatly influence the characteristic and reliability of the embedded capacitor and reduce the manufacturing yield, they must be removed during a process of manufacturing the capacitor embedded in the PCB.
Referring to
That is, the surface defects of the copper foils 112 are removed by planarizing the surface of the CCL substrate 110. Therefore, the problems caused by the surface defects can be solved.
Referring to
The dielectric layer 120 is formed by depositing a ceramic composition having a high permittivity through various thin film forming methods, e.g., ALD, PLD, CVD, etc. Examples of the ceramic composition include BZN, Al2O3, PZT, PLZT, PT, PMN, PMN-PT, BaTiO3, HfO2, and SrTiO3. The present invention is not limited to them, but can use any materials if they have a high permittivity.
The top electrode 130 can be formed using a low-temperature sputtering process, an evaporation process, or an electroless plating process, and electrode material may be at least one selected from the group consisting of Cu, Ni, Al, Pt, Ta, Ag, and an alloy thereof.
Hereinafter, detailed methods for planarizing the surface of the copper foils in the CCL substrate will be described with reference to
Mechanical Polishing Method
A first cleaning process and a first drying process are sequentially performed on the surface of the CCL substrate having surface defects. It is preferable to use DI water as a cleaning solution.
Thereafter, the CCL substrate is polished until its surface defects are removed by using a polishing tape in which ceramic particles are coated on a polyester film. The ceramic particles preferably have a size of less than 20 μm, more preferably a size of less than 5 μm. This aims to minimize the occurrence of scratches on the surface of the CCL substrate due to the large-sized ceramic particles because the surface of the CCL substrate is roughly polished as the size of the ceramic particles increases. Examples of such fine ceramic particles are SiC and Al2O3.
Then, a second cleaning process and a second drying process are sequentially performed on the planarized surface of the CCL substrate.
According to the present invention, a first polishing process is performed by using a first polishing tape in which first ceramic particles having a size of less than 20 μm are coated on a polyester film, and a second polishing process is performed by using a second polishing tape coated with ceramic particles having a size smaller than that of the first polishing tape. Therefore, scratches of the CCL substrate due to the first polishing tape having the large ceramic particles are mitigated by the second polishing tape having the smaller ceramic particles, thereby minimizing the occurrence of the scratches on the surface of the CCL substrate.
Electrolytic Polishing Method
Like the mechanical polishing method, a first cleaning process and a first drying process are sequentially performed on a surface of a CCL substrate having surface defects.
Then, an electrolytic polishing process is performed for a predetermined time by soaking the CCL substrate in electrolyte composed of a combination of one or more acids selected from the group consisting of phosphorous acid, sulfuric acid, hydrochloric acid, nitric acid, boric acid and the like. The electrolytic polishing time can be varied depending on the characteristic of the copper foils and the processing conditions.
When the electrolyte has pH of greater than 6.0, a polishing rate is so low that the surface defects are not removed completely. Thus, it is preferable that the electrolyte has pH of less than 5.0.
Specifically, it is preferable that the electrolyte further includes an additive containing chromic acid or urea in order to prevent the corrosion of the copper foils of the CCL substrate. When less than 0.5 wt % additive for the entire electrolyte is added, the additive cannot nearly perform the function of preventing the corrosion of the copper foils. When greater than 1 wt % additive is added, it has the same effect as an electrolyte containing 1 wt % additive. Therefore, it is preferable that the additive contained in the electrolyte is in a range from 0.5 wt % to 1 wt %.
In addition, it is preferable that a temperature of the electrolyte is in a range from 0° C. to 75° C. When the temperature is below 0° C., the electrolyte is frozen so that the electrolytic polishing is not performed. When the temperature exceeds 75° C., an electrolytic polishing speed increases so that the copper foils are not uniformly polished.
When a current density of the electrolyte is less than 5 A/dm2, a polishing characteristic of the electrolytic polishing is not almost exhibited. When the current density exceeds 50 A/dm2, the electrolytic polishing speed increase so that the copper foils are not uniformly polished. Thus, it is preferable that the current density of the electrolyte is in a range from 5 A/dm2 to 50 A/dm2.
Next, a second cleaning process and a second drying process are sequentially performed on the planarized CCL substrate.
As described above, the present invention can prevent the leakage current generated by the surface defects of the CCL substrate by sequentially forming the dielectric layer and the top electrode after removing the surface defects of the CCL substrate acting as the bottom electrode. In addition, the present invention can prevent the electrical short between the bottom electrode and the bottom electrode, which is caused by the formation defect of the dielectric layer.
Accordingly, the present invention can improve the characteristic and reliability of the embedded capacitor and can also increase the manufacturing yield.
Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0031099 | Apr 2006 | KR | national |
