This application claims the benefit of Korean Patent Application No. 2005-54035 filed with the Korea Industrial Property Office on Jun. 22, 2005, the disclosure of which is incorporated herein by reference.
1. Technical Field
The present invention relates to a printed circuit board with embedded electronic components and a fabrication method thereof.
2. Description of the Related Art
In response to demands for electronic devices with greater capabilities and smaller sizes, the recent trend is towards more densified and more miniaturized electronic components. The demand is thus increasing for small printed circuit boards which allow high-density mounting of electronic components. Accordingly, the multilayer circuit board is being developed, which provides electrical connection between wiring or between wiring and electrical components formed on different layers through via holes. The multilayer circuit board can not only reduce the wiring that interconnects electronic components, but can also provide high-density wiring. This has the advantages of increasing the surface area of the printed circuit board, as well as providing superior electrical characteristics.
The via holes 13 are created by forming an insulation layer 12, making perforations, and then coating the insides of the perforations with a metal. However, such via holes 13 require a complicated fabrication process, and entail many limitations in designing the wiring layers 11.
Further, while the reliability of the via holes 13 is crucial in providing a stable printed circuit board, stresses occur on the via holes 13 due to heat generated during the fabrication of the printed circuit board and due to the differences in heat expansion with the insulation layers 12 according to the operating environment, and such stresses become a cause of diminished connection reliability of the via holes 13.
The present invention has been devised to resolve the foregoing problems, and an aspect of the invention provides a printed circuit board with embedded electronic components, which does not require via holes.
Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.
To achieve the foregoing objectives, the present invention may be implemented in such embodiments as set forth below.
A printed circuit board with embedded electronic components having outer electrodes, according to one embodiment of the invention, comprises a substrate on which insertion holes are formed for containing the electronic components, a filler for filling the gap between the electronic component and the insertion hole to secure the electronic components, and attachment layers laminated onto the substrate in contact with the electrodes, with circuits formed on the attachment layers.
By virtue of this composition, the printed circuit board with embedded electronic components based on the present invention does not require via holes, since the attachment layers and the electrodes of the electronic components are in direct contact with each other. Thus, not only may the reliability of the electrical connection of the electronic components be increased, but also the fabrication cost and time may be reduced as well.
In another embodiment of the invention, the substrate may have substantially the same thickness as that of the electronic components. A first electrode ma be formed on one surface, and a second electrode may be formed on the other surface of the electronic component. The attachment layer may be formed of a first attachment layer in contact with the first electrode and a second attachment layer in contact with the second electrode. In another embodiment of the invention, two or more electrodes are formed on one surface of the electronic component, and the attachment layers may also include an attachment layer in contact with the electrodes.
The substrate may be formed of a copper clad laminate. The electronic components may be active elements as well as passive elements, where both active elements and passive elements may be mounted together. Also, the printed circuit board may be laminated in two or more layers.
A method of fabricating a printed circuit board with embedded electronic components having outer electrodes, according to an embodiment of the present invention comprises forming insertion holes for containing the electronic components on a substrate, inserting and securing the electronic components in the insertion holes, filling the gaps between the insertion holes and the electronic components, forming an attachment layer in contact with the electrode on at least one surface of the substrate, and forming circuits on the attachment layer.
Securing the electronic components in the insertion holes may be achieved by attaching an adhesion sheet on a surface of the substrate or by using adhesive. The adhesion sheet or adhesive may be formed of a material that loses its adhesion with heat or UV radiation.
It may be preferable to further include a desmearing process of removing smears that occur during the forming of the insertion holes.
Preferably, filling the gaps with the filler may be performed using a vacuum printer to prevent the occurrence of bubbles in the insertion holes. The substrate may be a copper clad laminate forming or including an insulation layer. The electronic components may be passive elements and/or active elements.
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:
a is a schematic diagram illustrating an example of outer electrodes formed on one surface of an electronic component.
b is a schematic diagram illustrating another example of outer electrodes formed on one surface of an electronic component.
a is a cross-sectional view illustrating the operation of securing an electronic component using an adhesion sheet.
b is a cross-sectional view illustrating the operation of securing an electronic component by applying an adhesive.
Embodiments of the invention will now be described in detail with reference to the accompanying drawings, wherein those elements are rendered the same reference numeral that are the same or are in correspondence regardless of the figure number, and redundant explanations are omitted.
The substrate 31 is an insulation layer positioned between the attachment layers 37. The substrate 31 may be formed as a layer in which an inorganic filler is dispersed in a resin compound, including a thermosetting resin. Preferably, the thermosetting resin may include at least one of an epoxy resin, phenol resin, or isocyanate resin. This is because a thermosetting resin is superior in mechanical strength and heat resistance. Also, a variety of additives, such as a coupler, dispersant, or colorant, may be preferably be included in the resin compound to improve the properties of the substrate 31. For example, a coupler may improve the adhesion between the resin compound and the inorganic filler, and a dispersant may improve the dispersion of the inorganic filler and remove stains in the mixture.
The inorganic filler may be any one of Al2O3, MgO, BN, SiO2, SiC, and Si3N4, etc., or a combination thereof. These materials are superior in terms of heat conductivity, and thus may enhance the heat radiation of the substrate 31.
The insertion hole 33 is perforated in a predetermined position on the substrate 31. Since the electronic component 43 is inserted into the insertion hole 33, the insertion hole 33 is formed to have a size somewhat larger than that of the electronic component 43. Various methods are available for forming the insertion hole 33, such as pressing, drilling, and laser processing, etc. It may be preferable to perform an additional desmearing process of removing smears that occur when using drilling or pressing processes to form the insertion hole 33.
The filler 35 is filled between the electronic component 43 and the insertion hole 33, to secure the electronic component 43. In general, epoxy resin may be used for the filler 35. When applying the filler 35, it may be preferable to prevent the occurrence of bubbles in the insertion hole 33 by using a vacuum printer.
The attachment layers 37 are metal layers laminated onto one or both surfaces of the substrate 31, and are in contact with the outer electrodes 431, 433 of the electronic components 43. The attachment layers 37 may be formed by copper cladding. Since the attachment layers 37 are in direct contact with the electrodes 431, 433 of the electronic component 43, the printed circuit board with embedded electronic components based on the present invention does not require via holes. Therefore, a more flexible design is possible, as well as reduced fabrication cost and time, when forming circuits on the attachment layer 37, because it is not necessary to consider via holes as in previous art. Moreover, the direct contact between the attachment layers 37 and the electrodes 431, 433 of the electronic component 43 provides a superior electrical reliability. Various circuits may be formed on the attachment layers 37 by circuit printing processes.
The electronic component 43 has substantially the same thickness as that of the substrate 31. Also, on the upper and lower surfaces are formed the first electrode 431 and the second electrode 433, respectively. The first electrode 431 and the second electrode 433 are in contact with the attachment layers 37. The electronic component 43 may be an active element, such as a transistor, IC, and LSI, etc., or may be a passive element, such as a resistor, condenser, and inductor.
a and
a is a cross-sectional view illustrating an implementation of the operation S20 of securing the electronic components 43 contained in the insertion holes 33. An adhesion sheet 39 is attached to a surface of the substrate 31, and the electronic components 43 are secured within the insertion holes 33 by means of the adhesion sheet 39. Typical double-sided tape may be used for the adhesion sheet 39. The adhesion sheet 39 is exfoliated after applying the filler 35.
b is a cross-sectional view illustrating another implementation of operation S20. First, adhesive 41 is coated on a table (T) in areas somewhat larger than the size of the electronic components 43, and then the substrate 31 and electronic components 43 are positioned in order. Adhesion ink may be used for the adhesive 41. The filler 35 is applied while the electronic components 43 are secured by the adhesive 41, after which portions of the adhesive 41 are removed by means of polishing processes, should the adhesive 41 protrude beyond the surface of the substrate 31 or cover the electrodes of the electronic components 43.
It is preferable that the adhesion sheet 39 or the adhesive 41 lose its adhesion with heat or UV radiation. Thus, the adhesion sheet 39 may readily be detached or the substrate may readily be detached from the table (T) by supplying heat or UV radiation, after applying the filler while the electronic components 43 are secured by the adhesion sheet 39 or the adhesive 41.
According to the present invention, the embodiments of which are comprised as set forth above, the following benefits may be obtained.
Since the electronic components are connected by direct contact between the electrodes of the electronic components and the attachment layers, a printed circuit board with embedded electronic components and fabrication method thereof may be obtained which provide superior electrical reliability.
As the present invention does not require via holes, a printed circuit board with embedded electronic components and fabrication method thereof may be obtained with which the fabrication is made easier, with reductions in fabrication cost and time.
Although a few embodiments of the present invention 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 invention, the scope of which is defined in the appended claims and their equivalents.
Number | Date | Country | Kind |
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10-2005-0054035 | Jun 2005 | KR | national |