Abstract:
Configuration for testing the bonding positions of conductive drops and test method by using the same is disclosed. In the invention, a special configured contact pad for setting a conductive drop and an associated wire pattern are useful for knowing the drop condition of single or several displaying panels. The contact pad comprises at least two conductive members respectively coupled to two wires; and an isolating portion between conductive members for separation. The normal dropping position of a conductive drop on the contact pad includes at least a portion of the conductive members. Accordingly, the contact pad is originally an open-circuit without conductive drop thereon, but the contact pad is conductive when the contact drop sets on its normal dropping position. Whether the conductive drop forms on the normal dropping position of the contact pad is determined by measuring the electrical properties of the contact pad.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Taiwan application Serial No. 092133937, filed Dec. 2, 2003.  
       TECHNICAL FIELD  
       [0002]     The invention relates in general to a configuration for testing the bonding positions of conductive drops and test methods for using the same, and more particularly to a configuration applied in a flat panel display for testing the bonding positions of conductive drops and test methods for using the same.  
       BACKGROUND  
       [0003]     A flat panel display, such as liquid crystal display (LCD), organic electro-luminescent display (OELD) or liquid crystal on silicon (LCOS), plays an important role as a communication interface between people and the information in the modern living. The flat panel display is assembled using a first and a second substrate. Before assembling, one or several contact pads for positioning conductive drops (for example, Au drop or Ag drop) are formed at one of the substrates (for example, substrate having thin film transistors (TFT) or organic electro-luminescent diodes, or silicon substrate). After completing the assembly of the second substrate and the first substrate, the substrates are electrically connected through the contact pads and the conductive drops.  
         [0004]     In general, the flat panel display comprises two substrates. One substrate comprises several electronic components (i.e. switches, transistors, diodes, capacitors, etc.), electrodes and conductive lines, and the other substrate comprises electrodes, conductive lines or a color filter (CF). An example of a flat panel display is a Thin Film Transistor-Liquid Crystal Display (TFT-LCD), which comprises a first substrate, a second substrate and a Liquid Crystal (LC) medium (i.e. numerous LC molecules) therebetween. The first substrate (such as a transparent glass) comprises thin film transistors (TFTs) arranged in an array, pixel electrodes, orthogonal scan (gate) lines and data (signal) lines. The second substrate (such as a transparent glass) comprises the CFs. In the traditional method of fabricating the Liquid Crystal Display (LCD), the second substrate having CFs and sealant is aligned and pressed with the first substrate having TFTs. The sealant is then cured for assembling the second substrate and the first substrate. For small size display, the cell (i.e. space between the substrates) is a vacuum, which is created by capillary attraction after two substrates are assembled. But for large size display, the newly developed method, call “one drop fill” (ODF), is to drop the LC directly on the substrate before the two substrates are aligned and assembled.  
         [0005]     Whether a large size display or a small-sized-display is manufactured, one or several contact pads are formed at one (for example, the lower substrate having TFT) of the substrates for positioning conductive drops (i.e. Au drops or Ag drops) before the substrates are assembled. Referring to  FIG. 1 , a conventional panel having the contact pads is illustrated. Also,  FIG. 1  illustrates a small size (ex: 1.79″) panel. Two contact pads  102 ,  104 , which are made from a conductive material, are positioned at the corners of a panel  100 . The two contact pads  102  and  104  are coincident with the bonding positions of conductive drops.  
         [0006]     However, the conductive drops could miss the positions of the contact pads, due to the misdrop by a machine or other factors. Applying the conductive drops to a position other than the contact pads  102  and  104  results in an electrical-connection flaw on the display, which is typically noticed after assembly of the substrates. The conventional design of the contact pad cannot prevent or test whether the conductive drops miss the positions of the contact pads.  
       SUMMARY  
       [0007]     It is therefore desired to provide a configuration for testing the bonding positions of conductive drops and test methods by using the same. By providing a contact pad with special design and the related testing configuration, it can be quickly observed whether the conductive drops are formed at the dropping positions of a single panel or a plurality of panels.  
         [0008]     One embodiment can be implemented by providing a contact pad. The contact pad, applied to a substrate, and the contact pad is positioned on the substrate relative to a dropping position of a conductor. The contact pad includes a first conductive member, and a second conductive member. The dropping position of the conductor involves at least a portion of the first conductive member and at least a portion of the second conductive portion.  
         [0009]     Embodiments of the present invention can also be viewed as providing methods for testing bonding position of conductor. The method includes the steps of providing a contact pad on the substrate and applying the conductive material to the substrate. The substrate defines a dropping position for a conductive material, and the contact pad is positioned on the substrate relative to the dropping position. The contact pad includes a first conductive member and a second conductive member. The dropping position of the conductor involves at least a portion of the first conductive member and at least a portion of the second conductive portion.  
         [0010]     Other objects, features, and advantages will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  (prior art) illustrates a conventional panel having two contact pads.  
         [0012]      FIG. 2  illustrates a new exemplary contact pad.  
         [0013]      FIG. 3A  illustrates a panel having the two exemplary new contact pads and a test configuration.  
         [0014]      FIG. 3B  is a circuit drawing of  FIG. 3A .  
         [0015]      FIG. 4A  illustrates another panel having two exemplary new contact pads and a second test configuration.  
         [0016]      FIG. 4B  is a circuit drawing of  FIG. 4A .  
         [0017]      FIG. 5  illustrates a test configuration for a plurality of panels.  
         [0018]      FIG. 6  illustrates a side view of a flat panel display. 
     
    
     DETAILED DESCRIPTION  
       [0019]     In one embodiment, a new contact pad with a special figure and a related test configuration is utilized for testing whether a conductive drop is applied at the contact pad.  FIG. 2  illustrates a non-limiting example of one type of a new contact pad  202 . The contact pad  202  includes two conductive members  202   a  and  202   b,  and an insulating portion  202   c  between the conductive members  202   a,    202   b.  The insulating portion  202   c  interposes the conductive members  202   a  and  202   b  such that the conductive members  202   a  and  202   b  are not directly electrically connected. Therefore the insulating portion  202   c  is a gap or an insulator. The dashed circle  204  represents the “dropping position” for a conductive drop. The dropping position  204  includes at least a portion of the conductive member  202   a,  at least a portion of the conductive member  202   b,  and at least a portion of the insulating portion  202   c.  When a conductive drop is applied to the contact pad  202  at the dropping position of a conductive drop, the conductive drop forms an electrical bridge between the conductive members  202   a  and  202   b  such that there is electrical continuity between the conductive members  202   a  and  202   b.    
         [0020]     Accordingly, the contact pad  202  of the invention possesses the function of “the switch”. If the conductive drop is positioned at the dropping position  204  on the contact pad  202 , “the switch” is on; if not, “the switch” is off. The contact pad  202  could be made of any conductive material, such as indium tin oxide (ITO), aluminum (Al), molybdenum (Mo), chromium (Cr), copper (Cu), alloy (such as aluminum alloy, copper alloy, molybdenum alloy), or combination of metal layers (such as ITO layer and Al layer, ITO layer and Al alloy layer, ITO layer and Mo layer, ITO layer and Al layer and Mo layer, ITO layer and Al alloy layer and Mo alloy layer, Al layer and Mo layer, Al alloy layer and Mo alloy layer). A conductive drop could be a gold (Au) drop or a drop of another electrical conductor.  
         [0021]     It is noted that the contact pad  202  shown in  FIG. 2  is non-limiting. The numbers and shapes of the conductive members and the insulating portions of the contact pad can be optionally varied if the contact pad similarly functions as a switch, which means that the conductive members are electrically connected after applying a conductive drop.  
         [0022]     A contact pad can be applied to a single panel or a plurality of panels. The configurations for testing the bonding positions of conductive drops can be optionally developed, depending on the application. A first embodiment and a second embodiment are provided for illustrating test configurations and methods of single panel and several panels, respectively. Also, the embodiments disclosed herein are for illustrating the invention, but not for limiting the scope of the invention. Additionally, for the sake of clarity, the drawings show the major characteristic parts. Accordingly, the specification and the drawings are to be regard as illustrative and non-limiting.  
       FIRST EMBODIMENT  
     Configuration For Testing a Single Panel and Test Method Using the Same  
       [0023]     In the first embodiment, a single panel having two contact pads (as shown in  FIG. 2 ) and two dropping positions for conductive drops is discussed. The two contact pads are formed on the panel and wires are formed to connect the contact pads. Among other things, the wires are used for testing whether conductive drops are set on the dropping positions of the panel. The wiring pattern of the wires could be modified according to the practical application. For example, the wiring pattern of a panel in which all the contact pads receive conductive drops can be different from the wiring pattern of a panel in which only some contact pads receive conductive drops. The details are described below.  
       EXAMPLE 1  
       [0024]      FIG. 3A  illustrates a panel  300  having contact pads and a test configuration according to the first embodiment. In  FIG. 3A , contact pads  302  and  304  are formed at the corners of the panel  300  for the positioning of conductive drops. The contact pads  302 ,  304  could be made of any conductive material, such as ITO, Al, Mo, Cr, Cu, alloy (such as Al alloy, Cu alloy, Mo alloy), or combination of metal layers (such as ITO layer and Al layer, ITO layer and Al alloy layer, ITO layer and Mo layer, ITO layer and Al layer and Mo layer, ITO layer and Al alloy layer and Mo alloy layer, Al layer and Mo layer, Al alloy layer and Mo alloy layer). Each contact pad comprises two conductive members and an insulating portion. As shown in  FIG. 3 , the contact pad  302  (at the right corner of the panel  300 ) comprises the conductive members  302   a  and  302   b,  and an insulating portion  302   c  between the conductive members  302   a  and  302   b.  The insulating portion  302   c  prevents direct electrical connection between the conductive members  302   a  and  302   b.  The contact pad  304  (at the left corner of the panel  300 ) comprises conductive members  304   a  and  304   b,  and an insulating portion  304   c  between the conductive members  304   a  and  304   b.  The insulating portion  304   c  prevents direct electrical connection between the conductive members  304   a  and  304   b.  Also, a first wire  310  connects the conductive members  302   a  and  304   a;  a second wire  312  connects the conductive members  302   b  and  304   b.  The conductive members  302   a  and  304   b  are connected to test pads  306  and  308  through a wire  314  and a wire  316 , respectively. The test pads  306  and  308  could be made of any conductive material, such as ITO, Al, Mo, Cr, Cu, alloy (such as Al alloy, Cu alloy, Mo alloy), or combination of metal layers (such as ITO layer and Al layer, ITO layer and Al alloy layer, ITO layer and Mo layer, ITO layer and Al layer and Mo layer, ITO layer and Al alloy layer and Mo alloy layer, Al layer and Mo layer, Al alloy layer and Mo alloy layer).  
         [0025]      FIG. 3B  is a circuit drawing of  FIG. 3A  with a conductive drop  318  applied to the contact pad  302 . When a conductive drop is correctly applied to one of the contact pads, the conductive drop electrically bridges the insulating portion of that conductive pad so that the conductive members of that contact pad are electrically connected. For example, the conductive drop  318 , which can be an Au drop, has been correctly applied to the contact pad  302  such that the conductive members  302   a  and  302   b  are electrically connected. Consequently, the circuit (illustrated in  FIG. 3B ) comprising, the wire  314 , the contact pad  302 , the wire  312 , the conductive member  304   b,  and the wire  308  has electrical continuity and is conductive. The electrical properties including, but not limited to, resistance, conductance, inductance, and capacitance of the circuit illustrated in  FIG. 3B  are function of the materials that make up the circuit and the elements of the circuit. One or more of these electrical properties can be measured to determine whether or not the circuit is completed, i.e., there is electrical continuity between the test pads  306  and  308 . For example, if the resistance between the test pads  306  and  308  were finite, then there is electrical connectivity, i.e., the contact pad  302  having the conductive drop  318  correctly applied is a “closed switch”. Similarly, if a conductive drop is correctly applied on the contact pad  304 , then there is also electrical continuity between the test pads  306  and  308 .  
         [0026]     Therefore, the wire pattern as shown in  FIG. 3A  and  FIG. 3B  is applicable for testing whether at least one contact pad of the panel is correctly bonded with a conductive drop.  
       EXAMPLE 2  
       [0027]      FIG. 4A  illustrates another panel  400  having a pair of contact pads  402  and  404 , and  FIG. 4A  also illustrates another test configuration according to the first embodiment. In  FIG. 4A , the contact pads  402  and  404  are formed at the corners of the panel  400  for the positioning of conductive drops. The contact pad  402  (at the right corner of the panel  400 ) comprises conductive members  402   a  and  402   b,  and an insulating portion  402   c  between the conductive members  402   a  and  402   b.  The insulating portion  404   c  prevents direct electrical connection between the conductive members  404   a  and  404   b.  The contact pad  404  (at the left corner of the panel  400 ) comprises the conductive members  404   a  and  404   b,  and an insulating portion  404   c  between the conductive members  404   a  and  404   b.  The insulating portion  404   c  prevents direct electrical connection between the conductive members  404   a  and  404   b.  The conductive members  402   a  and  404   b  are connected to test pads  406  and  408  through a wire  410  and a wire  412 , respectively. The contact pads  402 ,  404  and the test pads  406 ,  408  could be made of any conductive material, such as ITO, Al, Mo, Cr, Cu, alloy (such as Al alloy, Cu alloy, Mo alloy), or combination of metal layers (such as ITO layer and Al layer, ITO layer and Al alloy layer, ITO layer and Mo layer, ITO layer and Al layer and Mo layer, ITO layer and Al alloy layer and Mo alloy layer, Al layer and Mo layer, Al alloy layer and Mo alloy layer).  
         [0028]     In this embodiment, only one wire, wire  414 , connects the contact pads  402  and  404 . As shown in  FIG. 4A , the conductive member  404   b  is connected to the conductive member  402   b  through the wire  414 .  
         [0029]     Referring to  FIG. 4B ,  FIG. 4B  is a circuit drawing of  FIG. 4A  with conductive drops  420  and  422  applied to contact pads  402  and  404 , respectively. In  FIG. 4B , the dashed circles illustrate the dropping positions  416  and  418 , which are coincident with the contact pads  402  and  404 , respectively. In  FIG. 4A , both contact pads  402  and  404  are “open switches” because their respective conductive members are not electrically connected. Consequently, the test pads  406  and  408 , as shown in  FIG. 4A , are not electrically connected through the circuit comprising wiring  410 ,  412 , and  414 , and the contact pads  402  and  404 .  
         [0030]      FIG. 4B  illustrates the circuit of panel  400  after the conductive drops  420  and  422  have been applied to the contact pads  402  and  404 , respectively. The conductive drop  420 , which was applied at the dropping position  416 , is disposed over portions of the conductive members  402   a  and  402   b  and a portion of the insulation portion  402   c.  The conductive drop  422 , which was applied at the dropping position  418 , is disposed over portions of the conductive members  404   a  and  404   b  and a portion of the insulation portion  404   c.  Consequently, contact pads  402  and  404  are functionally “closed switches”, and the test pads  406  and  408  are electrically connected through the wiring  410 ,  412 , and  414  and through the contact pads  402  and  404 .  
         [0031]     After finishing the dropping of the conductive drops, the resistance between the test pads  406  and  408  is measured. If a finite resistance between the test pads  406  and  408  is obtained, that means all of the contact pads are correctly bonded with the conductive drops; if not, that means at least one contact pad failed to bond with the conductive drop (i.e. the conductive drop fell outside of the bonding position, or the dropping position of the conductive drop didn&#39;t connect the conductive members).  
         [0032]     Therefore, the wire pattern as shown in  FIGS. 4A, 4B  is applicable for testing whether all of the contact pads of the panel are correctly bonded with the conductive drops.  
       SECOND EMBODIMENT  
     Configuration For Testing a Mother Substrate With Several Panels and Test Method Using the Same  
       [0033]      FIG. 5  illustrates a test configuration for a plurality of panels according to the second embodiment of the invention. In  FIG. 5 , an assembly element  500  includes a plurality of the panels  300  are formed, and each panel  300  included in  FIG. 5  has a test configuration corresponding to the panel  300  of  FIG. 3A . It is, of course, understood that the test configuration on the panel  400  ( FIG. 4A ) or other test configuration comprising more than two contact pads on the panel could be used in the practical application. The contact pad  300  (an insulating means between conductive members) and the wire pattern on a single panel have been described in the description of  FIG. 3  and is not repeated.  
         [0034]     As shown in  FIG. 5 , the panels  300  are arranged as an array which has X direction and Y direction on an assembly element  500 . So the panels  300  are arranged from X 1  column (X 1 ,Y 1 )˜(X 1 ,Ym) to Xn column (Xn,Ym) or from Y 1  row (X 1 ,Y 1 )˜(Xn,Y 1 ) to Ym row(X 1 ,Ym)˜(Xn,Ym). An array is comprised of the n columns X 1 -Xn of panels  300 , and m rows Y 1 -Ym of panels  300 . Each panel  300  in the Y direction of panels is connected to its adjacent panels by a pair of coupling wires  507  and  509 . Wire  507  extends from one of the conductive members of the contact pad  302  in a first panel  300  to the test pad  306  of a second panel  300 , where the second panel is above and adjacent to the first test panel. Similarly, wire  509  extends from one of the conductive members of the contact pad  304  in the first panel  300  to the test pad  308  of the second panel  300 . A pair of test wires  510  and  512  extend from the panel that is at the edge of the Y direction to chief test pads  506  and  508 . Wire  510  extend from the test pad  306  of the edge of the Y direction panel to the chief test pad  506 , and wire  512  extends from the test pad  308  to the chief test pad  508 .  
         [0035]     After finishing the dropping of the conductive drops, if the resistance between the chief test pads  506  and  508  is finite, then there is electrical connectivity between the chief test pads  506  and  508 . The resistance between the chief test pads  506  and  508  is measured for checking the bonding condition for each column of panels. Since each column of panels are wired in series, every panel required the conductive drop(s) dropping at the appropriate position(s) (i.e. dropping at one or all contact pads, depending on the wire patterns as described in the first embodiment). The columns of panels in the array are tested one by one. For a column, the resistance between the chief test pads  506  and  508  is measured, and if the measured resistance equals (within a margin of error) a predetermined value, then the conductive drops have been correctly applied to the contact pads within that column. In which case, each panel in the column has been tested and each contact pad is determined to be a closed circuit. On the other hand, if the measured resistance is not equal to (within a margin of error) the predetermined value, then at least one contact pad is an open circuit. In that case, the panels within that column are electrically separated and tested one by one to find the contact pads or contact pads that are open circuits.  
         [0036]     In the practical fabrication, an assembly element  500  could be a first substrate having several TFT panels, and assembled with the other second substrate having several CF panels. After cutting the assembled substrates according to the standard method, several displays are produced.  
         [0037]     Accordingly, the large-sized substrate having several panels and the test configuration of the invention has the advantage of testing the bonding positions of conductive drops so as to increase the yield of the production. It reduces the amount of time testing by testing groups of panels together, and if a problem is detected with a group of panels, then the panels within the group can be individually tested or a sub-group of the group can be tested, individually or together. For a massive production, the configuration and the test method according to the invention do improve the yield and save the production time.  
         [0038]     Although the panels  300  on the substrate are illustrated as grouped into several columns that was done only as an illustration of one embodiment. In another embodiment, the panels on a substrate could be divided into several rows, and the panels of each row are serially wired for quick check. Also, the panels on the substrate could be regularly wire-connected in a slanted direction or in a Z-shaped direction, or could be irregularly wire-connected for quick check.  
         [0039]     Also,  FIG. 5  shows the test pads ( 306 ,  308 ) of a panel are wired connected to the contact pads of adjacent panel, however, the invention is not limited in this configuration. The test pads of each panel could directly touch the contact pads of adjoining panel.  
         [0040]     Moreover, it is not necessary to form the chief test pads  506 ,  508  for each group of the panels at the outside of the panels. The test pads on the last panel could be used as the chief test pads. Accordingly, the positions of the chief test pads depend on the situation of applications (i.e. facilitation of testing steps).  
         [0000]     Fabrication of the Test Configuration  
         [0041]     The test configuration (comprises the contact pads and the wire pattern) as described as previously described in conjunction with  FIGS. 3A and 4A  could be formed using one step after the manufacture of the electronic components and devices of the panel are completed, or could be formed between the manufacturing steps of the electronic components and devices of the panel.  
         [0042]     In one embodiment, a panel having TFTs is produced in five processes. The first, the third and the fifth processes are related to the formation of conductive components. The second and the fourth processes are related to the formation of nonconductive components. The test configuration could be formed by an additional process (i.e. the sixth process) after the five processes are completed. Also, the conductive parts (i.e. the conductive members of contact pads, the connecting wires, the test wires, the test pads and the chief test pads) of the test configuration could be formed in the first, the third and the fifth processes. Similarly, the non-conductive parts (i.e. the insulating portions of contact pads) of the test configuration could be formed in the second and the fourth processes.  
         [0043]      FIG. 6  illustrates a side view of a flat panel display  600 . The flat panel display  600  includes a contact pad  602 , a first substrate  601 , a second substrate  603 , and a conductive drop  608 . The contact pad  602  is disposed on the substrate  601 . Typically, the contact pad  602  is formed on the first substrate, but in some embodiments, the contact pad  602  is applied to the substrate  603 . The contact pad  602  is configured to have a first conductive member  602   a,  a second conductive member  602   b,  and an insulating portion  602   c  interposing the conductive members. The contact pad is approximately coincident with a dropping position for a conductor for the first substrate  601 . The conductive drop  608  has been provided to the contact pad  602 . A conductive layer  606  and a functional layer  607  are formed on the second substrate  603 . The functional layer  607  includes CF layers or Black Matrix layers or insulating layer. Another functional layer  605  includes TFT layers or EL layers or conductive layer on the first substrate. The first and second substrates are in electrical continuity through the conductive drop  608 .  
         [0044]     While the invention has been described by way of examples and in terms of the preferred embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.