Abstract:
A device ( 1 ) for bonding two components ( 31, 32 ) includes a heating unit ( 11 ) and a lifting device ( 13 ) used to drive the heating unit to move. The heating unit includes a pressing device ( 17 ) including a pressing plate ( 171 ). The pressing plate can conduct heat, and the pressing plate is adapted to press the components. The bonding device can prevent protuberances from forming in a connecting part between the bonding components and can achieve reliable hot pressing result.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a device and a method for bonding two electrical components together, and especially to a device and a method used for bonding two electrical components together under constant temperature conditions.  
         [0003]     2. General Background  
         [0004]     A method of assembling a liquid crystal display (LCD) module generally comprises a step of electrically interconnecting a liquid crystal display panel, a drive integrated circuit (IC), a flexible printed circuit (FPC) and a printed circuit board (PCB).  
         [0005]     A hot press bonding method is generally used in an LCD module assembling process in order to bond two electrical components together. There are two kinds of hot press bonding methods; one is a pulse hot press bonding method, and the other is a constant temperature hot press bonding method. A pulse hot press bonding method comprises the following steps: firstly, pressing two bonding components together; secondly, heating solder between the bonding components to a melted state using electric energy; and finally, cooling the solder between the bonding components in order to firmly connect the bonding components together. This method can prevent protuberances from forming in a connecting part between the bonding components, and can also prevent faulty soldering.  
         [0006]      FIG. 5A  shows a temperature-time relationship of a pulse hot press bonding process, and  FIG. 5B  shows a temperature-time relationship of a constant temperature hot press bonding process. In these graphs, t 1  is a warm-up time of the hot pressing process, t 2  is a working time, t 3  is a cooling time, Tm is a melting temperature of the solder, and curves A and B represent the relation of time-temperature of the solder in the bonding process. In the pulse hot press bonding process shown in  FIG. 5A , the solder is warmed up during t 1  time and begins to melt at the temperature Tm, then the step of hot press bonding proceeds during time t 2 , and then a pressing head of the pulse hot press bonding device is detached from the pressed components at time A 1  after a cooling time t 3  has elapsed. At time A 1 , the solder is solidified, and the bonding components are connected together firmly. In the constant temperature hot press bonding process shown in  FIG. 5B , the solder is warmed up during time t 1  and begin to melt at the temperature Tm, then the step of hot press bonding proceeds during time t 2 , and then a pressing head of the constant temperature hot press bonding device is detached from the bonded components at time B 1 . At time B 1 , the solder is still in a melted state, because the temperature of the solder is higher than its melting temperature. The bonded components may at least partially separate from each other and create gaps therebetween, because the pressing force on the bonded components has been removed. This can leads to incomplete or faulty electrical communication.  
         [0007]     The constant temperature hot press bonding device has a simple structure, low cost, and low power consumption. Therefore, notwithstanding the above-described problems encountered with the constant temperature hot press bonding process, this process is still favored by certain manufacturers.  
         [0008]     What is needed, therefore, is a constant temperature hot press bonding device that can provide improved hot press bonding quality. What is further needed is a constant temperature hot press bonding method that can improve the hot press bonding quality.  
       SUMMARY  
       [0009]     In one preferred embodiment, a device for bonding two components includes a heating unit and a lifting device used to drive the heating unit to move. The heating unit includes a pressing device including a pressing plate. The pressing plate can conduct heat, and the pressing plate is adapted to press the components. The bonding device can prevent protuberances from forming in a connecting part between the bonding components and can achieve reliable hot pressing result.  
         [0010]     In another preferred embodiment, a method for reliably bonding two components together includes: providing a heat conducting component; moving the heat conducting component to a top of an overlapping region of the bonding components; pressing and heating the overlapping region of the bonding components through a heating device on the heating conducting component; and lifting up the heating device, such that the heat conducting component continues to press the overlapping region of the bonding components until the bonding components have cooled down.  
         [0011]     Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic, side cross-sectional view of a constant temperature hot press bonding device in an non-working state according to a preferred embodiment of the present invention, together with two components placed therein;  
         [0013]      FIG. 2  is another schematic, side cross-sectional view of the constant temperature hot press bonding device of  FIG. 1 , such view being perpendicular to that of  FIG. 1 ;  
         [0014]      FIG. 3  is similar to  FIG. 1 , but showing the constant temperature hot press bonding device in a working state;  
         [0015]      FIG. 4  is a schematic, side cross-sectional view of a constant temperature hot press bonding device according to another preferred embodiment of the present invention, together with two components placed therein; and  
         [0016]      FIG. 5A  is a graph showing a temperature-time relationship in a typical pulse hot press bonding process, and  FIG. 5B  is a graph showing a temperature-time relationship in a typical constant temperature hot press bonding process. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]     Reference will now be made to the drawings to describe the preferred embodiments in detail.  
         [0018]     Referring to  FIG. 1  and  FIG. 2 , a constant temperature hot press bonding device  1  includes a base  10 , a heating unit  11 , a lifting device  13  used to drive the heating unit  11  to move, a movable stage  14 , and a horizontal framework  15  connecting with the movable stage  14 . The movable stage  14  and the lifting device  13  are arranged on top of the heating unit  11 . The base  10  is for supporting two bonding components  31  and  32  arranged under the heating unit  11 .  
         [0019]     The base  10  includes an X-Y stage  16 , and an object stage  12  arranged on the X-Y stage  16 . The X-Y stage  16  can move left and right and forward and rearward in a horizontal plane, which movement moves the object stage  12  to a desired position. Two bonding components  31  and  32  are arranged on the object stage  12 , and a plurality of solder balls  33  are arranged in an overlapping region between the bonding components  31  and  32 .  
         [0020]     The heating unit  11  includes a heating head  111 , a main body  112 , two brackets  113 , and a pressing device  17 . The two brackets  113  are arranged on two edges of the main body  112 . Each bracket  113  has a hole  114 . The heating head  111  is arranged below the main body  112 . The pressing device  17  includes two pressing components  172 , and a pressing plate  171  that can conduct heat. Each pressing component  172  is a T-shaped cylinder set, which is fixed in a corresponding one of the holes  114 . A diameter of the pressing component  172  is smaller than a diameter of the hole  114 , so that the pressing component  172  can slide in the hole  114  freely. The pressing plate  171  is arranged between the heating head  111  and the overlapping region of the bonding components  31  and  32 , so that the heating head  111  can heat the bonding components  31  and  32  through the pressing plate  171 .  
         [0021]     Referring to  FIG. 3 , in operation, the heating unit  11  is driven to move down until the heating head  111  contacts the pressing plate  171  and the pressing plate  171  presses on the overlapping region of the two bonding components  31  and  32 . The solder balls  33  in the overlapping region are heated by the heating head  111  and the pressing plate  171 , and the solder balls  33  begin to melt when they reach their melting temperature. After the solder balls  33  are melted, the heating head  111  is driven by the lifting device  13  to move up, so that the heating head  111  leaves the pressing plate  171 . However, the pressing plate  171  remains on the overlapping region because of the gravity of the pressing plate  171  and continues to press and heat the bonding components  31  and  32 . Once the heating head  111  has been moved to a predetermined height, the bonding components  31  and  32  and the solder balls  33  at the overlapping region are cooled. After the above-mentioned process has been completed, the solder balls  33  firmly connect the bonding components  31  and  32  together.  
         [0022]     In the illustrated embodiment, the bonding component  31  is an FPC. The bonding component  32  is a PCB. The solder balls  33  can be made from terne alloy, or alternatively an anisotropic conductive film (ACF) can be used. The such as an plate  171  is a metal plate that can conduct heat and that resists warping, an iron plate.  
         [0023]     Referring to  FIG. 4 , another preferred embodiment of a constant temperature hot press bonding device  2  is similar to the above-described constant temperature bonding device  1 , except that a pressing device  27  is an L-shaped iron plate. The pressing plate  27  includes a horizontal pressing component  271 , and a bent portion  272  extending perpendicularly up from one edge of the pressing plate  27 . The bent portion  272  makes it convenient to take hold of the pressing plate  27 . An object stage  22  of the constant temperature hot press bonding device  2  is magnetic, to attract and attach the pressing plate  27  thereonto, and thereupon to drive the pressing plate  27  to press the bonding components  31  and  32  together.  
         [0024]     In alternative embodiments, the object stage  22  can also be made from non-magnetic material. In such case, a magnetic device can be set below the bonding components  31  and  32  in order to attract the pressing plate  27 . Further or alternatively, a spring can be used to press the bonding components  31  and  32  together.  
         [0025]     A method using the constant temperature hot pressing device  1  or  2  comprises the following steps. Firstly, providing a heat conducting component, like the pressing component  171  or  271 , and moving the heat conducting component  171  or  271  to a top of an overlapping region of the bonding components  31  and  32 . Secondly, pressing and heating the overlapping region of the bonding components  31  and  32  through the heat conducting component. Thirdly, pressing a heating head  111  on the heat conducting component, and heating the overlapping region of the bonding components  31 ,  32  through the heat conducting component. Finally, lifting up the heating head  111 , such that the heat conducting component continues to press the overlapping region with its gravity until the bonding components  31  and  32  and the solder balls  33  have cooled down.  
         [0026]     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.