Patent Application
20100075497
1. Field of the Invention
The present invention generally relates to a plating method, and more particularly, to a non-plating line (NPL) plating method using current transmitted from a ball side.
2. The Prior Arts
Currently, electronic products are more often packaged with environmental friendly materials. In order to satisfy the demand for lead free or even halogen free environmental friendly materials, the reliability of the IC carrier board must be more critically concerned. In this circumstance, if a lead free material is used as a soldering tin, the melting point of the soldering tin will be much higher than the conventional solder tin. And therefore, the reliability and heat resistance of the carrier board are correspondingly required to be much better. Unfortunately, this raises many other problems caused by the high temperature processing environment for the IC manufacturers to overcome.
For the purpose of improving electric properties and reducing noise, currently the carrier boards are mostly modified with an NPL design, while wire bonding areas are still desired to be electroplated with nickel/gold (Ni/Au) for achieving a better bondability. Even though an electroless nickel and immersion gold (ENAG) process may be used for fabricating the wire bonding areas, the wire bonding areas fabricated by such an ENAG process are evaluated with an unsatisfactory reliability. As such, an NPL wire bonding block configured by electroplating Ni/Au is often fabricated by a gold pattern plating (GPP) (e.g., full body gold) process.
However, before performing such a GPP process, an electroplating Ni/Au layer has been formed earlier than the solder mask (SM), and therefore a relatively large area of the electroplating Ni/Au layer is covered by the SM. Since it is well known that the SM is featured of a poor bondability with gold, the GPP method becomes incapable of satisfying the current requirements for a higher reliability and a better heat resistance.
Further, the NPL process is very complicated. The NPL process even requires for a specific machine for plating a thin copper layer. Parameters of etching the thin copper layer after plating the same are very difficult to control, during which micro short often occurs or a reliability test causes micro short so as to bring serious consequence.
The present invention provides a method for forming an insulation layer (e.g., a photoresist layer) first and then forming an electroplating Ni/Au layer. The Ni/Au layer is plated without plating lines, and therefore adapted for avoiding all of the foregoing disadvantages.
A primary objective of the present invention is to provide an NPL plating method using current transmitted from a ball side. The NPL plating method is featured in that at first it forms a circuit layer on a bump side only, and therefore a plating current can be transmitted via a plating metal layer on a ball side to the circuit layer (enclosed by an insulation layer, e.g., a solder resist or a photoresist) on the bump side, and thus forming a protection layer, e.g., plating gold, on the plating metal layer on the circuit layer and the ball side. In such a way, the plating gold is formed after the insulation layer, so that there won't be any plating gold existed beneath the insulation layer of the bump side (connected with dies). Hence, the insulation layer can be prevented from dropping off from the protection layer, i.e., the plating gold, and thus the reliability of the products can be improved.
For achieving the foregoing objective of the present invention, the present invention provides an NPL plating method using current transmitted from a ball side. First, a carrier board is provided. The carrier board has a ball side and a bump side, and at least one pin through hole (PTH). A plating metal layer is formed on the surfaces of the ball side and the bump side, as well as a wall surface of the PTH. The ball side and the bump side are electrically connected via the plating metal layer. Then, only the plating metal layer on the bump side is patterned to form a first circuit layer. Then, an insulation layer is formed at a periphery of the first circuit layer while exposing a part of the first circuit layer. Finally, a plating current is transmitted from the plating metal layer on the ball side to the first circuit layer on the bump side, so as to form a first protection layer on the exposed part of the first circuit layer.
The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which:
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
In accordance with the NPL plating method, a first circuit layer 7a as shown in
In such a way, the plating gold is formed after the insulation layer 14, so that there won't be any plating gold existed beneath the insulation layer 14 of the bump side (connected with dies). Hence, the insulation layer 14 can be prevented from dropping off from the plating metal layer, and thus the reliability of the products can be improved.
As shown in
The foregoing protection layer 16, second protection layer 18 can be plating gold, plating nickel, or a combination thereof, while the insulation layer 14 and the insulation layer 20 can be solder resist or photoresist.
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
