Signal transmission structure, package structure and bonding method thereof

A signal transmission structure including a first signal pad, a first reference plane surrounding the first signal pad, a second signal pad, a second reference plane surrounding the second signal pad, an electric conductive element, and a conductive wall is provided. The second reference plane is parallel to the first reference plane, and the electrical conductive element is connected between the first signal pad and the second signal pad to transmit a signal. The conductive wall is connected between the first reference plane and the second reference plane and surrounding the electrical conductive element. Furthermore, a package structure applying to the signal transmission structure and a bonding method thereof are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 95110496, filed Mar. 27, 2006. All disclosure of the Taiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a signal transmission structure, more particularly, the present invention relates to a signal transmission structure of preventing an internal signal thereof from Electromagnetic Interference (EMI).

2. Description of Related Art

At present market, an electronic apparatus having a signal transmission structure therein is utilized to transmit signals in the electronic apparatus. In general, there is a high-density electronic device installed in the electronic apparatus, therefore, it is easy to generate Electromagnetic Interference (EMI) between the signal transmission structure and other electronic devices when transmitting the signals and further effect the signal transmission quality.

For example, in the semiconductor industry, the integrated circuit (IC) chip manufacturers usually produce high integration, multifunction and high speed IC chip by improving the clock frequency, the wiring density and the number of the I/O terminals. Generally, such an integrated circuit chip is electrically connected to a circuit board through a chip carrier in order to transmit the electronic signal between the integrated circuit chip and the circuit board. Nevertheless, the electronic signal is effected easily by EMI as the increasing clock frequency of integrated circuit chip.

FIG. 1is a schematic view of a conventional package structure. Referring toFIG. 1, the conventional package structure100includes a carrier110used to carry a chip10, a circuit board120parallel to the carrier110, and a solder ball130that is electrically connected between a contact112of the carrier110and a contact122of the circuit board120. Consequently, the electronic signal can transmit through the solder ball130between the chip10and circuit board120.

It is to be noted that the carrier110is electrically connected to the circuit board120as well as parallel to the circuit board120; thus, the carrier110and the circuit board120will form a resonant cavity. That is, if the clock frequency of the transmitting signal between the chip10and the circuit board120happens to the resonant frequency of the resonant cavity, parts of energy of the signal will transmit to the resonant cavity and the amplitude of the signal will be significantly decreased. It further causes poor signal transmission quality between the chip100and circuit board120.

Moreover, when there is a noise happened in the carrier110and circuit120as well as the frequency of such noise is equivalent to the resonant frequency of the resonant cavity between the carrier110and the circuit board120, the noise will interfere with the signal through the resonant cavity to cause the poor signal transmission quality between the chip10and the circuit board120.

SUMMARY OF THE INVENTION

The present invention is directed to providing a signal transmission structure to resolve the poor signal quality between two reference planes.

The present invention is also directed to providing a package structure, in which good signal transmission quality between two parallel substrates is achieved.

The present invention is further directed to providing a bonding method to fabricate the aforementioned package structure.

In order to achieve the above objectives or the other, a signal transmission structure including a first signal pad, a first reference plane surrounding the first signal pad, a second signal pad, a second reference plane surrounding the second signal pad, an electric conductive element, and a conductive wall is provided in the present invention. The second reference plane is parallel to the first reference plane, and the electrical conductive element is connected between the first signal pad and the second signal pad to transmit a signal. The conductive wall is connected between the first reference plane and the second reference plane as well as surrounding the electrical conductive element.

According to the present invention, a package structure is further provided to include a first substrate, a second substrate, an electrical conductive element and a conductive wall. The first substrate includes a first signal pad, a first reference plane and a first solder mask layer, wherein the first reference plane is surrounding the first signal pad and the first solder mask layer is disposed on the first reference plane and the first signal pad is exposed by the first solder mask layer; and the first solder mask layer is having a first annular opening surrounding the first signal pad to expose a part of the first reference plane. Furthermore, the second substrate includes a second signal pad, a second reference plane and a second solder mask layer, wherein the second reference plane is surrounding the second signal pad and the second solder mask layer is disposed on the second reference plane and the second signal pad is exposed by the second solder mask layer; and the second solder mask layer has a second annular opening surrounding the second signal pad to expose a part of the second reference plane. Moreover, the electrical conductive element is connected between the first signal pad and the second signal pad in order to transmit a signal. The conductive wall is connected between the first reference plane exposed by the first solder mask layer and the second reference plane exposed by the second solder mask layer as well as surrounding the electrical conductive element.

In the aforementioned circuit transmission structure and circuit substrate, the first reference plane and the second reference plane are ground planes, for example.

In the aforementioned circuit transmission structure and circuit substrate, the first reference plane and the second reference plane are power planes, for example.

In the aforementioned circuit transmission structure and circuit substrate, the electrical conductive element is a metal ball, for example.

In the aforementioned circuit transmission structure and circuit substrate, the signal frequency is more than 1 GHz, for example.

In the aforementioned circuit transmission structure and circuit substrate, the conductive wall can form a sealed space.

In a preferred embodiment of the present invention, the first substrate is a circuit substrate or a printed circuit board (PCB).

In a preferred embodiment of the present invention, the second substrate is the circuit substrate or a printed circuit board (PCB).

According to the present invention, a bonding method is further provided to bonding the first substrate and the second substrate of the aforementioned package structure and the bonding method includes the following steps. Firstly, a first conductive material is disposed on the first signal pad and/or a second signal pad. Meanwhile, a second conductive material is disposed on the first reference plane and/or the second reference plane of the periphery of the first conductive material. Then, the first conductive material is connected between the first signal pad and the second signal pad by bonding the first substrate and the second substrate. Meanwhile, the second conductive material is connected between the first reference plane and the second reference plane to form the conductive wall that is surrounding the first conductive material.

In a preferred embodiment of the present invention, the step of bonding the first substrate and the second substrate further comprises reflowing the first conductive material and the second conductive material.

In a preferred embodiment of the present invention, the step of disposing the first conductive material comprises disposing a first metal ball on the first signal pad and/or the second signal pad.

In a preferred embodiment of the present invention, the step of disposing the second conductive material comprises disposing a plurality of the second metal balls on the first reference plane and/or the second reference plane.

In a preferred embodiment of the present invention, the step of disposing the second conductive material comprises spraying a solder paste on the first reference plane and/or the second reference plane.

The signal transmission structure of the present invention is to dispose a conductive wall in the periphery of the electrical conductive element connected between the first signal pad and the second signal pad. A good quality of the signal transmitting between the first reference plane and the second reference plane can be obtained by means of the conductive wall that is surrounding the electric conductive element.

In order to the make aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below.

DESCRIPTION OF EMBODIMENTS

FIG. 2Ais a lateral view showing a signal transmission structure according to a preferred embodiment of the present invention.FIG. 2Bis a top view showing a signal transmission structure according to a preferred embodiment of the present invention. Referring toFIGS. 2A and 2Bsimultaneously, the signal transmission structure200of the present invention includes a first signal pad210, a first reference plane220that is surrounding the first signal pad210, a second signal pad230, a second reference plane240that is surrounding the second signal pad230, an electrical conductive element250and a conductive wall260. In the present embodiment, the second reference plane240is parallel to the second reference plane240, wherein the first reference plane220and the second reference plane240are, for example, ground plane or power plane. In addition, the electrical conductive element250is connected between the first signal pad210and the second signal pad220in order to transmit a signal. The conductive wall260is connected between the first reference220and the second reference240as well as surrounding the electrical conductive element250. The above mentioned electrical conductive element250is, for example, a metal ball and the signal frequency is more than 1 GHz, for example.

In the present embodiment, the conductive wall260is connected between the first reference plane220and the second reference240as well as surrounding the electrical conductive element250. In a preferred embodiment, the conductive wall260can form a sealed space therein, for example. Consequently, the conductive wall260can lower the total inductance value (Lloop) effectively so as to have lower synchronous switching noise (SSN) when signals are transmitting between the two reference planes220/240and to further improve the signal transmission quality.

Based upon the above, the signal transmission structure recited in the aforementioned embodiment of the present invention can be applied to the semiconductor package technology.FIG. 3is a schematic view of a package structure according to a preferred embodiment of the present invention. Referring toFIG. 3, the package structure300in the present embodiment includes a first substrate310, a second substrate320, an electrical conductive element330and a conductive wall340. In the present embodiment, the first substrate310includes a first signal pad312, a first reference plane314and a first solder mask layer316, wherein the first reference plane314is surrounding the first signal pad312and the first solder mask layer316is disposed on the first reference plane314and the first signal pad312is exposed by the first solder mask layer316. The first solder mask layer316has a first annular opening316asurrounding the first signal pad312to expose a part of the first reference plane314.

Furthermore, the second substrate320includes a second signal pad322, a second reference plane324and a second solder mask layer326, wherein the second reference plane324is surrounding the second signal pad322and the second solder mask layer326is disposed on the second reference plane324and the second signal pad322is exposed by the second solder mask layer326. The second solder mask layer326has a second annular opening326asurrounding the second signal pad322to expose a part of the second reference plane324. Furthermore, the electrical conductive element330is connected between the first signal pad312and the second signal pad322in order to transmit a signal, wherein the electrical conductive element is, for example, a metal ball and the signal frequency is more than 1 GHz, for example. The conductive wall340of the present embodiment is connected between the first reference plane314exposed by the first solder mask layer316and the second reference plane324exposed by the second solder mask layer326as well as surrounding the electrical conductive element330, namely, the conductive wall340forms a seal space therein.

Based upon the above, the first/second reference planes314/324and the first/second signal pads312/322recited in the present embodiment are located in the same circuit layer (as shown inFIG. 3); nevertheless, the present invention is not limited to the relative positions of the reference plane and the signal pad, namely, the first/second reference planes314′/324′, and the first/second signal pads312/322can be located in different circuit layer respectively. On the other hand, the first/second annular openings316a/326aof the present embodiment penetrate the first/second solder mask layer316/326respectively. In another embodiment, the first/second annular openings316a/326a, for example, can further penetrate the first/second dielectric layers318/328in order to be electrically connected with the first/second reference planes314′/324′. Furthermore, the aforementioned first substrate310or the second substrate320, for example, is the circuit substrate or printed circuit board (PCB); meanwhile, the first reference plane314and the second reference plane324are, for example, ground planes or power planes.

The bonding method of the first substrate310and the second substrate320in the aforementioned package structure300is described in detail in the followings.

FIG. 4Ais a three-dimensional top view of the first substrate and the second substrate according to a preferred embodiment of the present invention.FIG. 4Bis a three-dimensional bottom view of the first substrate and the second substrate according to a preferred embodiment of the present invention. Referring toFIGS. 4A to 4Bsimultaneously, the present embodiment relates to dispose a first conductive material302on the first signal pad312and to dispose second conductive materials304on the first reference plane314surrounding the first conductive material302. Meanwhile, the present embodiment also relates to dispose second conductive materials304on the second reference plane324exposed by the second annular opening326a. In the present embodiment, the method of disposing the first conductive material302is, for example, to dispose a first metal ball on the first signal pad312. Then, the method of disposing the second conductive materials304is, for example, to dispose a plurality of the second metal balls on the first/second reference planes314/324. Specifically, the second conductive materials304are disposed on the first/second reference planes314/324exposed by the aforementioned first and second annular openings316a/326a.

After that, as shown inFIG. 5, the first substrate310is bonding with the second substrate320in order for the first conductive material302(the first metal ball) to be connected between the first signal pad312(referring toFIG. 4B) and the second signal pad322so as to form the electrical conductive element330shown inFIG. 3and for the second conductive materials304to be connected between the first reference plane314and the second reference plane324so as to form the conductive wall340(as shown inFIG. 6) surrounding the first conductive material302. In the present embodiment, when bonding the first substrate310and the second substrate320, it is possible by means of reflowing the first conductive material302so as to make the first conductive material302to be in melting state and to be connected between the first signal pad312and the second signal pad322. Similarly, the present embodiment also relates to the second conductive materials304(the second metal balls) can be melted by means of reflowing and connected mutually thereafter to form the conductive wall340in the package structure300as shown inFIG. 6, wherein the first substrate310is not shown inFIG. 6in order to have a clear view. It should be noted that the conductive wall340shown in the present embodiment is a sealed conductive wall340which is formed after the second metal balls are reflowed. Certainly, in other embodiments, it is not limited that every metal ball should be connected to each other, but the metal balls can respectively form the mutually independent conductive wall which can reduce the noise interference.

Furthermore, it is possible to dispose the first conductive material302on the second signal pad322so as that the first conductive material302on the first signal pad312and the first conductive material302on the second signal pad322form the electrical conductive element330(as shown inFIG. 3) connected to the first signal pad312and the second signal pad322after reflowing. In one preferred embodiment, it is also possible to print solder paste on the first reference plane314and the second reference plane324respectively in order to form the aforementioned conductive wall. Naturally, the material of conductive wall can also be other type of solder material or conductive material.

Accordingly, the present invention applies to a conductive wall that is surrounding an electrical conductive element connected between the first signal pad and the second signal pad; therefore, the magnitude of the signal transmitting between the first reference plane and the second reference plane will not be effected by the resonant cavity formed between the first reference plane and the second reference plane; namely, such signal has better quality and will not be interfered by the noise of the signal from others. In other words, the signal transmission structure in the present invention provides a good signal transmission quality.

Although the present invention has been disclosed above by the preferred embodiments, they are not intended to limit the present invention. Anybody skilled in the art can make some modifications and alterations within the spirit and scope of the present invention. Therefore, the protecting range of the present invention falls in the appended claims.