Touch panel and a bonding structure and method thereof

A bonding structure includes a first substrate, a second substrate, a printed circuit board (PCB) disposed between the first substrate and the second substrate, anisotropic conductive adhesive (ACA) and conductive wires. The ACA is disposed between second connecting bonding pads of the first substrate and second bonding pads of the second substrate. First bonding pads of the first substrate are bonded with corresponding first matching bonding pads of the PCB, and second duplicated bonding pads of the first substrate are bonded with second matching bonding pads of the PCB, wherein the first and the second matching bonding pads are disposed on the same surface of the PCB. The second connecting bonding pads and the corresponding second duplicated bonding pads are electrically coupled via the conductive wires.

CROSS-REFERENCE TO RELATED APPLICATIONS

The entire contents of Taiwan Patent Application No. 103120925, filed on Jun. 17, 2014, from which this application claims priority, are incorporated herein by reference.

1.Field Of The Invention

The present invention generally relates to a bonding structure and method, and more particularly to a bonding structure and method of a touch panel.

2. Description Of Related Art

A touch panel is primarily operated by inputting driving signals and outputting sense signals in sequence. The driving signals and the sense signals are commonly transferred between the touch panel and other components (such as a processor) via a flexible printed circuit board (PCB).

FIG. 1shows a side view of a bonding structure100of a conventional touch panel, the bonding structure100mainly including a glass substrate11, a transparent substrate12and a flexible PCB13. First bonding pads111of the glass substrate11are opposite first matching bonding pads131of the flexible PCB13, and second bonding pads121of the transparent substrate12are opposite second matching bonding pads132of the flexible PCB13, where the first matching bonding pads131and the second matching bonding pads132are disposed on opposite surfaces of the flexible PCB13, respectively.

When the bonding structure100is subjected to bonding, the second bonding pads121of the transparent substrate12are first bonded with the corresponding second matching bonding pads132of the flexible PCB13, followed by bonding the first bonding pads111of the glass substrate11with the corresponding first matching bonding pads131of the flexible PCB13. In other words, the two opposite surfaces of the flexible PCB13need be dealt with in sequence to accomplish the bonding structure100in the conventional touch panel. The two-step bonding process is relevant to yield of the bonding structure100.

A need has thus arisen to propose a novel bonding structure and method in order to simplify the bonding process of the touch panel and to effectively enhance yield of the bonding structure.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the embodiment of the present invention to provide a bonding structure and method, which utilize a single-step bonding process performed on a single surface of a printed circuit board in coordination with a use of anisotropic conductive adhesive (ACA), therefore effectively enhancing yield of the bonding structure.

According to one embodiment, a bonding structure includes a first substrate, a second substrate, a printed circuit board, anisotropic conductive adhesive and conductive wires. The printed circuit board is disposed between the first substrate and the second substrate, the anisotropic conductive adhesive is disposed between the first substrate and the second substrate, and the conductive wires are disposed on the first substrate. First bonding pads are disposed on a surface of the first substrate facing the printed circuit board, and first matching bonding pads are disposed on a surface of the printed circuit board facing the first substrate and opposing the first bonding pads. Second bonding pads are disposed on a surface of the second substrate facing the first substrate but not blocked by the printed circuit board, and second connecting bonding pads are disposed on a surface of the first substrate facing the second substrate and opposing the second bonding pads. The anisotropic conductive adhesive is disposed between the second bonding pads and the second connecting bonding pads, such that the second bonding pads are electrically coupled with the corresponding second connecting bonding pads. Second duplicated bonding pads are disposed on the surface of the first substrate facing the printed circuit board, the second connecting bonding pads are electrically coupled with the corresponding second duplicated bonding pads via the conductive wires, and second matching bonding pads are disposed on the surface of the printed circuit board facing the first substrate and opposing the second duplicated bonding pads.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2Ashows a top view of a bonding structure200according to one embodiment of the present invention, andFIG. 2Bshows a side view along a section line2B-2B′ ofFIG. 2A. The bonding structure200of the embodiment is exemplified by, but not limited to, a touch panel.

As shown inFIG. 2B, the bonding structure200primarily includes a first substrate21, a second substrate22, and a printed circuit board (PCB)23disposed between the first substrate21and the second substrate22. A portion of the PCB23is disposed on a periphery of the first substrate21, and the other portion of the PCB23is disposed out of the first substrate21. When the first substrate21, the second substrate22and the PCB23are bonded together, signals of the first substrate21and the second substrate22may be transferred to or from other components via the PCB23.

Take the touch panel as an example, the first substrate21mentioned above may be a glass substrate, the second substrate22may be a transparent substrate (such as an Indium tin oxide (ITO) film), and the PCB23may be a flexible PCB. The transparent substrate may be made of an insulating material, such as Polycarbonate (PC), Polyethylene terephthalate (PET), Polyethylen (PE), Poly vinyl chloride (PVC), Poly propylene (PP), Poly styrene (PS), Polymethyl methacrylate (PMMA) or Cyclic olefin copolymer (COC). The first substrate21, the second substrate22and the PCB23bonded together may result in a glass-film (G1F) touch panel, in which a transparent substrate is laminated on a glass substrate, and two sensing layers (not shown) are formed on a surface of the first substrate21and on an opposing surface of the second substrate22, respectively.

FIG. 3Ashows a partially enlarged side view of an area3A ofFIG. 2B. As shown inFIG. 3A, plural first bonding pads211are disposed on a surface of the first substrate21facing the PCB23. Plural first matching bonding pads231are disposed on a surface of the PCB23facing the first substrate21and opposing the first bonding pads211. Moreover, plural second bonding pads221are disposed on a surface of the second substrate22facing the first substrate21(but not blocked by the PCB23). Plural second connecting bonding pads212are disposed on a surface of the first substrate21facing the second substrate22and opposing the second bonding pads221.

According to one aspect of the embodiment, anisotropic conductive adhesive (ACA)24is disposed between the second bonding pads221of the second substrate22and the second connecting bonding pads212of the first substrate21. The ACA24may be provided in film as an anisotropic conductive film (ACF), or be provided in paste as an anisotropic conductive paste. According to characteristics of the ACA24, electricity is conducted along a direction between the second substrate22and the first substrate21, and electricity is blocked along other directions. Accordingly, the second bonding pads221may electrically coupled with the second conductive bonding pads212correspondingly.

According to another aspect of the embodiment, plural second duplicated bonding pads213are disposed on a surface of the first substrate21facing the PCB23.FIG. 3Bshows a top view of the first substrate21ofFIG. 3A, andFIG. 3Cshows a top view of the second substrate22ofFIG. 3A. As shown inFIG. 3B, the second connecting bonding pads212and the corresponding second duplicated bonding pads213are connected via conductive wires214. Moreover, plural second matching bonding pads232are disposed on a surface of the PCB23facing the first substrate21and opposing the second duplicated bonding pads213.

When the first substrate21, the second substrate22and the PCB23are bonded together, the first bonding pads211of the first substrate21are electrically connected with the corresponding first matching bonding pads231of the PCB23, such that signals of the first substrate21may be transferred to or from other components via the PCB23. The second bonding pads221of the second substrate22are electrically coupled with the corresponding second connecting bonding pads212of the first substrate21via the ACA24, are further electrically coupled with the corresponding second duplicated bonding pads213via the conductive wires214, and are finally electrically connected with the corresponding second matching bonding pads232of the PCB23, such that signals of the second substrate22may be transferred to or from other components via the PCB23.

FIG. 4shows a flow diagram illustrated of a bonding method according to one embodiment of the present invention. In step41, the first substrate21is first bonded with the second substrate22. Specifically, the ACA24may be glued, for example, by thermal compression technique, between the second connecting bonding pads212of the first substrate21and the second bonding pads221of the second substrate22. As a result, the second bonding pads221may be electrically coupled with the corresponding second connecting bonding pads212via the ACA24, and are further electrically coupled with the corresponding second duplicated bonding pads213via the conductive wires214. According to the characteristics of the ACA24, no precise alignment is required in this step, which is thus not relevant to yield of the bonding structure200.

Subsequently, in step42, the first substrate21is bonded with the PCB23. Specifically, the first bonding pads211of the first substrate21are bonded with the corresponding first matching bonding pads231of the PCB23, and the second duplicated bonding pads213of the first substrate21are bonded with the corresponding second matching bonding pads232of the PCB23. As the first matching bonding pads231and the second matching bonding pads232of the PCB23are disposed on the same surface, a single bonding step is required to accomplish the bonding of the first bonding pads211of the first substrate21and the second bonding pads221of the second substrate22. Therefore, the embodiment may enhance bonding yield as compared to the conventional two-step bonding process (as shown inFIG. 1).