Method of Manufacturing Double-Sided Printed Circuit Board
The present invention provides a method of manufacturing a double-sided printed circuit board. An insulation substrate is first formed by creating a plurality of through holes on a Copper Clad Laminate (CCL) whose copper foil surface has been removed. Next, an electro-less copper layer is plated on the substrate for forming a plurality of plated through holes. After a wire pattern is formed on the substrate, a solder preventive layer is formed on top of the wire pattern. Next, a plurality of openings is created in between the solder preventive layer for exposing the contact pads. Finally, a protective layer is plated on top of the contact pads.
1. Field of the Invention
The present invention relates to a method of fabricating a double-sided printed circuit board, and more particularly, to a method of fabricating a double-sided circuit board with superfine circuits and high density circuits.
2. Description of the Prior Art
In recent history, printed circuit boards (PCBs) have been widely used for carrying various electronic components and devices. As there is demand for electronic products to be lighter, smaller, and portable, research and development of printed circuit boards is unavoidably moving toward a direction of miniaturization, higher integration, lower thickness, and the use of multiple layers.
In general, printed circuit boards having circuit layouts on both sides of the circuit boards have been widely used in numerous electrical apparatuses such as air-conditioners, telephones, and fax machines. Nevertheless, it is essential to have a “bridge”, or otherwise referred to as through holes, for communicating between the circuits and electrical wires on both sides of the board. The useable area of a typical double-sided printed circuit board is often twice that of a typical single-sided printed circuit board, and in contrast to a single-sided printed circuit board, the double-sided printed circuit board is more suitable to be used for products with complex circuits.
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It is therefore an objective of the present invention to provide a method of fabricating a double-sided printed circuit board for obtaining a printed circuit board with superfine circuits and increased circuit density.
According to the preferred embodiment of the present invention, a method of fabricating a double-sided printed circuit board comprises: providing a copper clad laminate (CCL) with copper clad removed or an insulating substrate; performing a drilling process for forming a plurality of through holes in the insulating substrate; disposing a copper layer on the insulating substrate and the sidewall of the through holes for forming a plurality of plated through holes; forming a wire pattern on the surface of the insulating substrate, wherein the wire pattern includes at least one contact pad; forming a solder resistant layer on the surface of the insulating substrate and forming at least one opening in the solder resistant layer for exposing the contact pad; and coating a protective layer on the surface of the contact pad.
By performing a drilling process on a CCL with the removed copper clad, the present invention is able to reduce the amount of time and effort required for a typical drilling and etching process, and decrease the diameter of the through holes, thereby producing printed circuit board with superfine wires and increasing the overall wire integration.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
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In addition to the fabrication stated above, the present invention can also be utilized in multilayer printed circuit board fabrication by removing the copper clad from the upper-most layer and the lower-most layer, and stacking the boards on top of one another.
In contrast to the prior art, the present invention provides a method of fabricating a double-sided printed circuit board by performing a drilling process on a CCL with the removed copper clad or an insulating substrate. By using substrates that are much thinner than the traditional CCL, the present invention is able to reduce the amount of time and effort required for a typical drilling and etching process, decrease the diameter of the through holes, and eventually produce printed circuit boards with superfine wires and increase the overall wire integration.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Claims
1. A method of fabricating a double-sided printed circuit board, the method comprising:
- providing a copper clad laminate (CCL), wherein the CCL comprises an insulating substrate and at least one copper clad disposed on the surface of the insulating substrate;
- performing an etching process for removing the copper clad on the surface of the insulating substrate;
- performing a drilling process for forming a plurality of through holes in the insulating substrate;
- disposing a chemical copper layer on the insulating substrate and the sidewall of the through holes for forming a plurality of plated through holes;
- forming a wire pattern on the surface of the insulating substrate, wherein the wire pattern includes at least one contact pad;
- forming a solder resistant layer on the surface of the insulating substrate and forming at least one opening in the solder resistant layer for exposing the contact pad; and
- coating a protective layer on the surface of the contact pad.
2. The method of claim 1, wherein the drilling process is a laser drilling process.
3. The method of claim 1, wherein a surface treatment is performed on the insulating substrate for increasing the adhesiveness of the insulating substrate and the chemical copper layer before the chemical copper layer is disposed.
4. The method of claim 3, wherein the surface treatment is a surface coarsening process.
5. The method of claim 1, wherein the formation of wire pattern further comprises:
- transferring a photoresist pattern to the surface of the insulating substrate;
- forming an electroplating copper layer on the surface of the insulating substrate and the sidewall of the through holes;
- performing a photoresist removing process; and
- performing an etching process on the insulating substrate for removing the exposed chemical copper layer.
6. The method of claim 5, wherein the photo removing process is a photo stripping process.
7. The method of claim 1, wherein the protective layer is comprised of nickel (Ni).
8. The method of claim 1, wherein the protective layer is comprised of gold (Au).
9. A method of fabricating a printed circuit board, the method comprising:
- providing an insulating substrate;
- performing a drilling process of forming a plurality of through holes in the insulating substrate;
- disposing a chemical copper layer on the insulating substrate and the sidewall of the through holes for forming a plurality of plated through holes; and
- forming a wire pattern on the surface of the insulating substrate, wherein the wire pattern includes at least one contact pad.
10. The method of claim 9, wherein the drilling process is a laser drilling process.
11. The method of claim 9, wherein a surface treatment is performed on the insulating substrate for increasing the adhesiveness of the insulating substrate and the chemical copper layer before the chemical copper layer is disposed.
12. The method of claim 11, wherein the surface treatment is a surface coarsening process.
13. The method of claim 9, wherein the formation of wire pattern further comprises:
- transferring a photoresist pattern to the surface of the insulating substrate;
- forming an electroplating copper layer on the surface of the insulating substrate and the sidewall of the through holes;
- performing a photo removing process; and
- performing an etching process on the insulating substrate for removing the exposed chemical copper layer.
14. The method of claim 13, wherein the photo removing process is a photo stripping process.
15. The method of claim 9 further comprising the following steps after the wire pattern on the surface of the insulating substrate is formed:
- forming a solder resistant layer on the surface of the insulating substrate and forming at least one opening in the solder resistant layer for exposing the contact pad; and
- coating a protective layer on the surface of the contact pad.
16. The method of claim 15, wherein the protective layer is comprised of nickel (Ni).
17. The method of claim 15, wherein the protective layer is comprised of gold (Au).
18. The method of claim 9, wherein the insulating substrate is a copper clad laminate (CCL) with copper clad removed.
Type: Application
Filed: Jun 7, 2005
Publication Date: Mar 16, 2006
Inventors: Hung-En Hsu (Taipei City), Binwei Wang (Taipei City), Shing-Fun Ho (Taipei City)
Application Number: 11/160,067
International Classification: H01B 13/00 (20060101); C23F 1/00 (20060101); H05K 3/02 (20060101);