1. Field of the Invention
The present invention relates to package substrates and a method for fabricating the same, and, more particularly, to a package on package (PoP) and a method for fabricating the same
2. Description of Related Art
Recently, with the increasingly smaller, lightweight and thinner profile in all types of electronic products, package on package (PoP) becomes increasingly popular.
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However, in the method of fabricating the conventional substrate, after electroplating to form the metal layer, in order to obtain the metal pillars with the same height, grinding is used to remove part of the metal layer and a second resist layer 14b with a plurality second resist layer openings 140b is formed. This grinding process may easily cause raw edges on the metal pillar, leading to short circuit of between the fine pitched metal pillars, resulting in yield reduction. Moreover, if etching is used to substitute grinding method to remove part of the metal layer, the inability to control the depth of etching may also lead to unequal heights of the metal pillars; moreover the neck part of the metal pillar may become a weak point in torque.
Accordingly, there is an urgent need to solve the foregoing problems encountered in the prior art.
In view of the foregoing problems, the present invention provides a method of fabricating a package substrate, comprising: providing a substrate having a first surface, a second surface opposing the first surface, and a plurality of first electrical connecting pads disposed on the first surface; mounting a metal board on the first electrical connecting pads; and patterning the metal board to define a plurality of metal pillars corresponding to the first electrical connecting pads.
In an embodiment, patterning the metal board comprises: forming a patterned resist layer on the metal board; removing a portion of the metal board that is not covered by the patterned resist layer; and removing the patterned resist layer.
In an embodiment, when a patterned resist layer is formed on the metal board, a third resist layer is formed on the second surface, and is removed when the patterned resist layer is removed. The metal board is removed by etching, and the metal layer is made of copper.
In an embodiment, a plurality of second electrical connecting pads are formed on the second surface, a surface treatment layer is formed on each of the second electrical connecting pads, and the surface treatment layer is made of nickel/gold.
In an embodiment, the surface treatment layer is formed before the metal board is mounted on the first electrical connecting pads by: forming a first conductive layer on the first surface and the first electrical connecting pads, and forming a second conductive layer on the second surface and the second electrical connecting pads; forming a first resist layer on the first conductive layer, and forming a second resist layer having a plurality of resist layer openings on the second conductive layer, each of the resist layer opening corresponding to each of the second electrical connecting pads; forming a surface treatment layer on the second conductive layer of the resist layer opening; removing the first resist layer and the second resist layer; and removing a portion of the first conductive layer and a portion of the second conductive layer that are not covered by the surface treatment layer.
In an embodiment, the first conductive layer and the second conductive layer are formed by sputtering, and the first conductive layer and the second conductive layer are removed by etching. After the metal pillars are formed, an insulative protection layer having a plurality of insulative protection layer openings are formed on the second surface.
In an embodiment, a first circuit and a second circuit are formed on the first surface and the second surface of the substrate body, respectively. The substrate body further comprises a plurality of conductive vias penetrating the first surface and the second surface, and electrically connecting the first circuit with the second circuit. The metal board is mounted on the first electrical connecting pads by soldering or ultrasonic welding methods.
A package substrate provided by the present invention comprises: a substrate body having a first surface, a second surface opposing the first surface, and a plurality of first electrical connecting pads disposed on the first surface; and a plurality of metal pillars disposed on the first electrical connecting pads, wherein each of the metal pillars is wider than a corresponding one of the first electrical connecting pads.
In an embodiment, the metal pillar is made of copper. In an embodiment, the package substrate further comprises a plurality of second electrical connecting pads disposed on the second surface, and a surface treatment layer formed on each of the second electrical connecting pads.
In an embodiment, the surface treatment layer is made of nickel/gold, and an insulative protection layer having a plurality of insulative protection layer openings is formed on the second surface.
In an embodiment, the first circuit and the second circuit are formed on the first surface and the second surface of the substrate body, respectively. The substrate body further comprises a plurality of conductive vias penetrating the first surface and the second surface and electrically connecting the first circuit with the second circuit.
In summary, the present invention involves mounting a metal board to the first electrical connecting pads, and the metal board is patterned to form a plurality of metal pillars. Thus, without the need of grinding, the problem of short circuit resulted from raw edges due to grinding of the metal pillars can be effectively solved by the present invention.
The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein:
The present invention is described in the following with specific embodiments, so that one skilled in the pertinent art can easily understand other advantages and effects of the present invention from the disclosure of the present invention.
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In comparison with the conventional technology, a metal board is mounted on the first electrical connecting pads, and is patterned to define a plurality of metal pillars. As a result, without the need of grinding, the problem of short circuit resulted from raw edges due to grinding of the metal pillars can be effectively solved by the present invention. In addition, as the top surface of the metal pillar is covered by the resist layer, during the pattering process of the metal board, the drawback of unequal heights of the metal pillars can be obviated.
The present invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the present invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Number | Date | Country | Kind |
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103116793 | May 2014 | TW | national |