Patent Publication Number: US-4729165-A

Title: Method of applying an integrated circuit on a substrate having an electrically conductive run

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     From German patent OS No. 32 43 227, it is already known how to attach integrated circuits (ICs) by means of an adhesive on the substrate of a liquid crystal display cell (LC cell). It is further known therefrom how to electrically connect the conductor runs of components carrying IC&#39;s to the conductor runs on the substrate of the LC cell by means of an electroconductive adhesive. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method, suitable in particular for automated manufacture, for the application and contacting of ICs on substrates consisting in particular of glass. 
     In accordance with the method of the invention, an integrated circuit is applied on a substrate which has an electric conductor run by suspending a liquid crystal display cell, in such a way that an electric contact is established between the conductor runs of the substrate and the conductor ribbons of the integrated circuit and using a frame of insulating material and self-supporting conductor ribbons. With the invention conductor ribbons are applied to the frame and the frame is pressed onto a support bearing a conductive adhesive layer in such a way that essentially only the regions of the conductor ribbons of the integrated circuit which are present on the surface of the frame are wetted with conductive adhesive. The frame is transferred with the integrated circuit and with the conductor ribbons wetted with adhesive onto the substrate in position so that the adhesive wetted conductor ribbons are pressed onto correspondingly arranged conductor run parts of the substrate. The adhesive is then permitted to harden or become cured so that a durable electrical connection between the conductor ribbons of the integrated circuit and the conductor runs of the substrate is established. 
     By the use of a frame of insulating material, in the opening of which the IC is freely suspended by its conductor ribbons, it is possible in a simple manner to provide the conductor ribbons at the desired points with conductive adhesive and to bring the IC to the desired point on the substrate and to electrically connect the conductor ribbons with the conductor runs on the substrate. 
     Accordingly, it is an object of the invention to provide an improved method for applying an integrated circuit which is suspended in the opening of a frame of insulating material by means of self-supporting conductor ribbons onto the surface of the substrate. 
     A further object of the invention is to provide a method which is simple to execute and inexpensive to carry out. 
    
    
     In the Drawings: 
     FIG. 1 is a top view of an integrated circuit having six conductor ribbons freely suspended in the opening of a frame 2 of insulating material; 
     FIG. 2 is an enlarged side elevational view indicating the points of the conductor ribbons which are provided with a thin layer of conductive adhesion in accordance with the method of the invention; and 
     FIG. 3 is a side elevational view on a large scale of a finished construction. 
    
    
     GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, in particular, the method of applying an integrated circuit onto the surface of a substrate provided with electrical conductor runs begins by suspending conductor ribbons 3 in the opening of a frame 2, as shown in FIG. 1. 
     In FIG. 1, an IC 1 which by means of six conductor ribbons 3 is freely suspended in the opening 8 of a frame 2 of insulating material. The frame 2 may be a stamped (punched-out) part of an insulating tape on which a plurality of ICs are delivered ready made. As is known, the individual ICs are then singled by stamping. The conductor ribbons 3 are applied e.g. by thin copper strips which are already soldered to or bonded on the contacts of the IC. 
     FIG. 2 shows how the desired points 9 of the conductor ribbons 3 are provided with a thin layer of a conductive adhesive below the insulating frame 2. 
     By means of tool 4, which is preferably a suction tool which holds the frame sucked on by vacuum, the frame 2 is brought to a support 6, on which is present at the desired points an adhesive layer 5 of a thickness as true to dimension as possible, in a still soft state. The IC1 is moved along, as the ribbons 3 are connected by the contact connections 7 with the IC and also with the frame 2, e.g. by gluing or welding. By application of the frame 2 on the moist adhesive layer 5 essentially only the region 9 of the conductor ribbon 3 below frame 2 is wetted with adhesive, as only in this region adequate pressure can be exerted. The ribbons 3, in fact, are relatively thin and flexible, e.g. 25 μm thick. The adhesive layer 5 is preferably thinner than the thickness of the ribbon, e.g 15 μm thick. It can thereby be avoided that with a large-area adhesive layer 5 also the surfaces of frame 2 present between the ribbons 3 are wetted, which would lead to undesired short-circuits. 
     After the wetting of the desired regions 9 of the ribbons with the conductive adhesive 5, frame 2 and hence the IC1 is now transferred by means of the tool 4 onto substrate or glass plate 11 of the LC cell and pressed on at the desired point, whereby at the same time the desired electrical connections with the conductor runs 15 are produced on the substrate 11 of the LC cell. 
     FIG. 3 shows the finished construction after removal of tool 4. The LC cell comprises two glass plates 12 and 11, between which the LC material 13 is located. By lutings 14 the liquid crystal material is enclosed. The conductor runs 15 are located on the substrate 11 and are brought out the interior of the LC cell through the lutings 14. Substrate 11 is larger than substrate 12 and is provided with appropriate conductor runs and contacts for direct application of the driving ICs. The regions 9 of the ribbons 3, wetted with the moist adhesive, are pressed onto the conductor runs 15 of the LC cell and hence glued on in an electrically contacted manner, after the adhesive is set or hardened. If desired, the LC1 may further be fastened on the substrate 11, secured against vibrations, by additional means, s e.g. adhesives. The remaining insulating frame 2 constitutes a permanent protection of the glued contact points. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.