Method of manufacturing a printed circuit board

A printed circuit board and a method of manufacturing the printed circuit board are disclosed. The method of manufacturing the printed circuit board can include forming a first protective layer over one surface of a core substrate, forming a first circuit pattern over the other surface of the core substrate by a first process, removing the first protective layer, forming a second protective layer over the other surface of the core substrate, and forming a second circuit pattern over the one surface of the core substrate by a second process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2008-0000799 filed with the Korean Intellectual Property Office on Jan. 3, 2008, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a printed circuit board and to a method of manufacturing the printed circuit board.

2. Description of the Related Art

Electronic equipment are being produced with higher performance and smaller sizes; leading to cost increases in such electronic equipment. As such, there are efforts to lower the cost of components used in electronic equipment.

Methods of manufacturing a printed circuit board according to the related art include tenting processes and additive processes.

Whereas tenting processes allow low manufacture costs, they are limited in forming fine-line circuit patterns. Additive processes have been developed to overcome this limitation, but these have the disadvantage of incurring higher costs.

In the related art, when a copper clad laminate (CCL) is used as the material for manufacturing a printed circuit board, the method used may involve applying a tenting process on both surfaces or applying an additive process on both surfaces. One reason for this may be that both surfaces would be exposed to the etchant or the plating bath simultaneously. Thus, even in cases where a fine-line circuit pattern is required on one surface only, the same process may have to be employed for both surfaces at the same time.

In the manufacture of a printed circuit board according to the related art, there may also be problems of curling or bending, etc., as the thickness of the printed circuit board is decreased.

SUMMARY

An aspect of the invention provides a method of forming circuit patterns sequentially on both surfaces of a printed circuit board.

Another aspect of the invention provides a method of manufacturing a printed circuit board that includes forming a first protective layer over one surface of a core substrate, forming a first circuit pattern over the other surface of the core substrate by a first process, removing the first protective layer, forming a second protective layer over the other surface of the core substrate, and forming a second circuit pattern over the one surface of the core substrate by a second process.

Still another aspect of the invention provides a method of manufacturing a printed circuit board that includes attaching one surface of each of a pair of core substrates onto either surface of a first protective layer, forming a first circuit pattern over the other surface of each of the pair of core substrates by a first process, separating the pair of core substrates from the first protective layer, attaching the other surface of each of the pair of core substrates onto either surface of a second protective layer, and forming a second circuit pattern over the one surface of each of the pair of core substrates by a second process.

Certain embodiments of the invention may include one or more of the following features.

In certain embodiments, the core substrate can be a copper clad laminate (CCL).

The first process can be any one selected from a group consisting of a tenting process, a semi-additive process, and an additive process.

The second process can be any one selected from a group consisting of a tenting process, a semi-additive process, and an additive process.

The first and second protective layers can be foam tapes.

A side of the second circuit pattern may be less slanted than a side of the first circuit pattern.

An interface can be formed within the first circuit pattern.

Yet another aspect of the invention provides a printed circuit board, which includes an insulation layer, a first circuit pattern having a side slanted with respect to the insulation layer that is formed over one surface of the insulation layer, and a second circuit pattern having a side slanted with respect to the insulation layer that is formed over the other surface of the insulation layer. The side of the second circuit pattern may be less slanted than the side of the first circuit pattern.

In certain embodiments of the printed circuit board, an interface can be formed within the first circuit pattern.

DETAILED DESCRIPTION

FIG. 1is a flowchart illustrating the manufacture of a printed circuit board according to an embodiment of the invention, andFIG. 2throughFIG. 7are cross sectional views representing a flow diagram illustrating the manufacture of a printed circuit board according to an embodiment of the invention. InFIGS. 2 to 7, there are illustrated a core substrate11, an insulation layer111, copper foils112, a first protective layer12, via holes13, a first circuit pattern14, vias15, a second protective layer16, and a second circuit pattern17.

Operation S11may include forming a first protective layer12over one surface of a core substrate11, whereFIG. 2represents a corresponding procedure.

The core substrate11can be made from just the insulation layer. This particular embodiment, however, illustrates the use of a copper clad laminate (CCL). The copper clad laminate (CCL) can include a copper foil on just one surface of the insulation layer, or as illustrated in this particular embodiment, include copper foils112stacked over both surfaces of the insulation layer111.

The thickness of a copper foil112can be such that allows the application of a tenting process. Also, the copper foil can be such that is thin enough to allow the application of a semi-additive process.

A tape, such as a foam tape, can be used for the first protective layer12, whereby the surface of the core substrate11can be protected in a simple manner from a plating liquid or etchant, etc., making it possible to form each of the first circuit pattern14and second circuit pattern17in order.

Operation S12may include forming a first circuit pattern14over the other surface of the core substrate11using a first process, whereFIG. 3andFIG. 4represent corresponding procedures.

Before forming the first circuit pattern14, via holes13can be perforated, as illustrated inFIG. 3, in order to form vias15that connect the circuit patterns14,17on either surface. A laser can be used for perforating the via holes13. Afterwards, the insides of the via holes13can be plated to form the vias15.

The first process can be any of a semi-additive process, tenting process, and additive process. In this particular embodiment, the first circuit pattern14may be formed by a tenting process. In cases where the core substrate11is made only of an insulation layer, an additive process may be used. An additive process may include selectively forming a circuit pattern over the insulation layer by electroless plating or electroplating. A semi-additive process may include selectively forming a circuit pattern over a thin film of copper, and then removing the exposed copper by etching.

Operation S13may include removing the first protective layer12. The first protective layer12can be physically separated or can be removed using a chemical solution. If a foam tape is used for the first protective layer12, increasing the temperature can create bubbles in the tape, so that the adhesion may be lowered and the tape may easily be separated from the core substrate11.

Operation S14may include forming a second protective layer16over the other surface of the core substrate11, whereFIG. 5represents a corresponding procedure.

The other surface of the core substrate11may already have the first circuit pattern14formed by the first process. Therefore, the second protective layer16can be attached to the other surface of the core substrate11, in order that the first circuit pattern14may not be damaged. The second protective layer16can be made from the same material as that of the first protective layer12.

Operation S15may include forming a second circuit pattern17over the one surface of the core substrate11using a second process, whereFIG. 6represents a corresponding procedure.

The one surface of the core substrate11may be exposed, after the removal of the first protective layer12. In this particular embodiment, the core substrate11may be a copper clad laminate, and thus a copper foil112may be exposed as illustrated inFIG. 5.

The second process can be a tenting process of removing portions of the copper foil112. If the copper foil is thin, it is possible to form the second circuit pattern17by a semi-additive process and then remove the exposed portions of the copper foil. If the one surface of the core substrate11is the insulation layer, an additive process can be used for forming the second circuit pattern17.

In this particular embodiment, the first circuit pattern14can be formed using an additive or a semi-additive process, and the second circuit pattern17can be formed using a tenting process, so that the sides of the second circuit pattern17can form lower inclinations, with respect to the insulation layer111, than the sides of the first circuit pattern14.

One reason for this may be that, because of the tenting process, the upper portions on the sides of the second circuit pattern17may be exposed more to the etchant than are the lower portions and may thus be removed more.

The first circuit pattern14, on the other hand, can have an interface formed within, because of the additional plating procedure included for forming the vias15.

Afterwards, the second protective layer16can be removed, and solder resists can be applied, to complete the printed circuit board10as illustrated inFIG. 7.

FIG. 8is a flowchart illustrating the manufacture of a printed circuit board according to another embodiment of the invention, andFIG. 9throughFIG. 14are cross sectional views representing a flow diagram illustrating the manufacture of a printed circuit board according to another embodiment of the invention. InFIGS. 9 to 14, there are illustrated core substrates21, insulation layers211, copper foils212, a first protective layer22, via holes23, first circuit patterns24, vias25, a second protective layer26, and second circuit patterns27.

Operation S21may include attaching one surface of each of a pair of core substrates21to either surface of a first protective layer22.FIG. 9represents a corresponding procedure.

In this particular embodiment, the pair of core substrates21can be attached to both surfaces of the first protective layer22in a symmetrical arrangement.

The core substrates21can be made from just the insulation layers. This particular embodiment illustrates the use of copper clad laminates (CCL). A copper clad laminate (CCL) can include a copper foil on just one surface of the insulation layer, or as illustrated in this particular embodiment, include copper foils212stacked over both surfaces of the insulation layer211.

The thickness of a copper foil212can be such that allows the application of a tenting process. Also, the copper foil can be such that is thin enough to allow the application of a semi-additive process.

A tape, such as a foam tape, can be used for the first protective layer22, whereby the surfaces of the core substrates21can be protected in a simple manner from a plating liquid or etchant, etc., making it possible to form each of the first circuit patterns24and second circuit patterns27sequentially.

Operation S22may include forming a first circuit pattern24over the other surface of each of the pair of core substrates21, whereFIG. 10andFIG. 11represent corresponding procedures.

Before forming the second circuit patterns27, via holes23can be perforated, as illustrated inFIG. 10, to form vias25for connecting the circuit patterns24,27. A laser can be used for perforating the via holes23. Afterwards, the insides of the via holes23can be plated to form the vias25.

The first process can be any of a semi-additive process, tenting process, and additive process. In this particular embodiment, the first circuit patterns24may be formed by a tenting process. In cases where the core substrates21are made only of insulation layers, an additive process may be used. An additive process may include selectively forming a circuit pattern over the insulation layer by electroless plating or electroplating. A semi-additive process may include selectively forming a circuit pattern over a thin film of copper, and then removing the exposed copper by etching.

Operation S23may include separating the pair of core substrates21from the first protective layer22. The first protective layer22can be physically separated or can be removed using a chemical solution. If a foam tape is used for the first protective layer22, increasing the temperature can create bubbles in the tape, so that the adhesion may be lowered and the tape may easily be separated from the core substrates21.

Operation S24may include attaching the other surface of each of the pair of core substrates21to either surface of a second protective layer26, whereFIG. 12represents a corresponding procedure.

The other surface of each core substrate21may already have the first circuit pattern24formed by the first process. Therefore, the second protective layer26can be attached to the other surface of each core substrate21, in order that the first circuit pattern24may not be damaged. The second protective layer26can be made from the same material as that of the first protective layer22. In this embodiment, the pair of core substrates21can be attached to the second protective layer26symmetrically.

Operation S25may include forming a second circuit pattern27over the one surface of each of the pair of core substrates21using a second process, whereFIG. 13represents a corresponding procedure.

One surface of each of the pair of core substrates21may be exposed, after the removal of the first protective layer22. In this particular embodiment, the core substrates21may be copper clad laminates, and thus the copper foils212may be exposed, as illustrated inFIG. 12.

The second process can be a tenting process of removing portions of the copper foils212. If the copper foils are thin, it is possible to form the second circuit patterns17by a semi-additive process and then remove the exposed portions of the copper foils. If the one surface of each of the core substrates21is an insulation layer, an additive process can be used for forming the second circuit patterns27.

Since the first circuit patterns24can be formed using an additive or a semi-additive process, and the second circuit patterns27can be formed using a tenting process, the sides of the second circuit patterns27can form lower inclinations with respect to the insulation layer211, compared to the sides of the second circuit patterns27.

One reason for this may be that, because of the tenting process, the upper portions on the sides of the second circuit patterns27may be exposed more to the etchant than are the lower portions and may thus be removed more.

The first circuit patterns24, on the other hand, can each have an interface formed within, because of the additional plating procedure included for forming the vias25.

Afterwards, the second protective layer26can be removed, and solder resists can be applied, to complete a pair of printed circuit boards20as illustrated inFIG. 14. Each printed circuit board20can be a complete product in itself.

FIG. 15is a cross sectional view of a printed circuit board according to yet another embodiment of the invention. InFIG. 15, there are illustrated a printed circuit board30, an insulation layer31, a first circuit pattern33, a second circuit pattern32, and vias34.

The printed circuit board30according to this embodiment may have a first circuit pattern33and a second circuit pattern32formed respectively on either surface. The second circuit pattern32can be formed by a tenting process, so that the sides321of the second circuit pattern32can be slanted with respect to the insulation layer31.

The sides331of the first circuit pattern33, however, may be slanted by a greater inclination from the insulation layer31compared to the sides321of the second circuit pattern32, as the first circuit pattern33can be formed by an additive or a semi-additive process.

A tenting process can involve removing unnecessary portions with an etchant and having the remaining portions form the circuit pattern. Here, the upper portions of the circuit pattern can be exposed more to the etchant and thus can be removed more. Therefore, the sides321of the second circuit pattern32can form a smaller inclination with the insulation layer31compared to those of the first circuit pattern33, as is illustrated inFIG. 15.

The first circuit pattern33can have an interface36formed within, because of the extra plating procedure involved in forming the vias34.

According to certain aspects of the invention as set forth above, circuit patterns can be formed sequentially on either surface of a printed circuit board, making it possible to apply a different process for forming the circuit pattern on each surface of the printed circuit board.

While the spirit of the invention has been described in detail with reference to particular embodiments, the embodiments are for illustrative purposes only and do not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention. As such, many embodiments other than those set forth above can be found in the appended claims.