Electronic parts carrier with a chip-supporting top tape
BACKGROUND OF THE INVENTION 
     This invention relates generally to electronic parts carriers used with a parts-mounting machine, and more particularly to such parts carriers or containers for integrated circuits with a so-called quad in-line package where leads are formed in four directions. 
     Conventional methods of carrying large-sized electronic parts with leads and other electronic parts generally utilize a so called paper tape or tray. More particularly, a paper tape is a tape-like carrier made of paper where recesses are formed in line for containing parts therein, and a tray is a carrier made of a synthetic resin so as to provide a plurality of recesses for containg parts therein. These recesses are formed through injection molding or vacuum or low pressure forming methods. 
     In the aforesaid prior art, since the depth of each recess is greater than the height of an IC chip to be placed in the recess, the chip is apt to vibrate during carrying. As a result of such vibration or movement within each recess or casing, the chip leads are apt to be damaged or deformed by receiving undesirable stress or shock. 
     Damaged or deformed comb-like leads sometimes provide undesirable phenomena such as poor contact or short circuiting, lowering the reliability of the product. Therefore, it has hitherto been necessary to add a process of rearranging of the teeth or pins of deformed leads using a rearranger so that the pitch of the teeth is uniform. 
     As described in the above, according to conventional chip carrier technology, the chip leads are apt to suffer from deformation and therefore such deformation is a reason for increasing cost because the deformed leads have to be rearranged by an additional process while such deformation sometimes deteriorates the product quality. 
     In addition, when chips in the carrier are moved when keeping in storage or the like, not only the leads but also the chip proper is apt to be damaged due to vibrations of the chip within the recess or casing of the conventional carrier. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed in order to remove the above-described drawbacks inherent to the conventional electronic parts carrier. 
     It is, therefore, an object of the present invention to provide a new and useful electronic parts carrier with which electronic parts contained in the carrier are prevented from receiving undesirable stresses even if vibrations and/or stresses are applied to the carrier during movement or parts storage. 
     According to a feature of the present invention an electronic parts carrier having a bottom tape and a top tape are provided where the bottom tape has a plurality of recesses for receiving electronic parts therein, and the top tape is arranged to be secured to the bottom tape such that each electronic part is held and sandwiched between the top and bottom tapes. Since the contained electronic part is secured and prevented from moving within the recess, the comb-like pins of the part are prevented from receiving direct stress. As a result, the pins are difficult to deform, contributing to the maintenance of high quality and cost reduction. 
     In accordance with the present invention there is provided an electronic parts chip carrier for use with a chip-mounting machine, comprising: a bottom tape having a plurality of recesses for receiving electronic parts chips respectively, each of the recesses having a bottom and side walls; a top tape securable to the bottom tape so as to close upward facing openings of the recesses, respectively; and means for securing the top tape at a predetermined position so that each electronic parts chip received in each of the recesses is securely held and sandwiched between an upper surface of the bottom of the recess and a lower surface of the top tape. 
     In accordance with the present invention there is also provided an electronic parts chip carrier for use with a chip-mounting machine, comprising: a bottom tape having a plurality of recesses for receiving electronic parts chips respectively, each of the recesses having a bottom and side walls, the depth of each of the recesses being less than the thickness of an electronic parts chip to be received in the recess; a top tape securable to the bottom tape so as to close openings of the recesses; and means for securing the top tape at a predetermined position so that each electronic parts chip received in each of the recesses is securely held and sandwiched between an upper surface of the bottom of the recess and a lower surface of the top tape. 
     In accordance with the present invention there is further provided an electronic parts chip carrier for use with a chip-mounting machine, comprising: a bottom tape having a plurality of recesses for receiving electronic parts chips respectively, each of the recesses having a bottom and side walls, a first engaging portion being formed on the side walls of each of the recesses; and a top tape securable to the bottom tape so as to close openings of the recesses, the top tape having a plurality of portions each having a second engaging portion to be engaged with the first engaging portion of the side walls so as to secure the top tape, thereby each electronic parts chip received in each of the recesses is securely held and sandwiched between an upper surface of the bottom of the recess and a lower surface of the top tape. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The object and features of the present invention will become more readily apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of an embodiment of the electronic parts carrier according to the present invention; 
     FIG. 2 is a perspective view of an electronic parts chip to be contained in the carrier of FIG. 1; 
     FIG. 3 is a cross-sectional view of the electronic parts carrier shown in FIG. 1; 
     FIG. 4 is a cross-sectional view showing partially a forming mold used for obtaining the electronic parts carrier of FIGS. 1 and 3; 
     FIG. 5 is a perspective view showing partially a conventional electronic parts carrier of tray type; 
     FIG. 6 is a cross-sectional view of a second embodiment electronic parts carrier according to the present invention; 
     FIG. 7 is a cross-sectional view of a third embodiment electronic parts carrier according to the present invention. 
     The same or corresponding elements and parts are designated at like reference numerals throughout the drawings. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, a schematic perspective view of an embodiment of the electronic parts carrier according to the present invention is shown. In FIG. 1, the reference 1 indicates a bottom tape in which a plurality of recesses 1a are formed in line in the longitudinal direction thereof. The bottom tape 1 is made of a film or sheet of polypropylene, polystyrene, ABS resin, polyvinyl chloride or the like. One of these materials may be used alone or added with an additive so that a conductive film or sheet is provided. The reference 2 indicates a top tape having a film base made of polyester, and a heat-sealable adhesive layer. The electronic parts carrier is formed of the above-mentioned bottom tape 1 and top tape 2. The reference 5 is an electronic parts chip shown to be contained in a recess 1a of the bottom tape 1. FIG. 2 shows an example of such a chip 5 having a body 5a and four sets of comb-like leads 5b. The top tape 2 is adhered to the bottom tape 1 at a flange portion 3 (see a cross-sectional view of FIG. 3) of the latter so that the electronic parts chip 5 is held and sandwiched between the lower surface of the top tape 2 and the inner bottom of the recess 1a of the bottom tape 1. 
     The use of a conductive film or sheet for the bottom tape 1 is advantageous because undesirable influence by static electricity on the contained chips 5 is removed. A plurality of pilot holes 3a are formed at one flange portion 3 such that the pilot holes 3a are equidistantly arranged in line. These pilot holes 3a will be used for driving and moving the carrier by an unshown mounting machine at a given pitch. 
     As best seen in FIG. 3, the recess 1a is formed with side walls 1b, deep bottom portions 1c and a center base 4 peripherally surrounded by the deep bottom portions 1c. The height of the center base 4 is selected such that the distance D between the inner surface of the center base 4 and the upper surface of the flange portion 3 is a slightly smaller than the thickness T of the electronic parts chip 5 to be received in the recess 1a. With this arrangement, when the top tape 2 is adhered to the flange portion 3 of the bottom tape 1 with the chip 5 being received in the recess 1a, the chip 5 is securely held and supported between the center base 4 and the lower surface of the top tape 2. In addition, the deep bottom portions 1c are deeper than the center base 4 to provide sufficient room for the leads 5b of the chip 5. Therefore, the leads 5b are prevented from receiving stresses and vibrations directly because the leads 5b are kept in space defined by the side walls 1b, the deep bottom portions 1c and the top tape 2. 
     FIG. 4 shows a cross-sectional view of a part of a mold used for forming and molding the bottom tape 1. The mold comprises an upper mold 6 and a lower mold 7 which are arranged to be engaged with each other for forming the bottom tape 1 therebetween. Air supply grooves 8 are formed in the upper mold 6. These air supply grooves 8 are used for taking out a molded product, i.e. a formed bottom tape 1, by way of air pressure. Vacuum grooves 9 are formed in the lower mold 7. These vacuum grooves 9 are used for forming a plastic film which has been heated to a temperature at which thermoplastic molding is possible. More particularly, an unshown vacuum pump is coupled with the vacuum grooves 9 to reduce the pressure of air in recesses of the lower mold 7 so as to shape a heated film supplied to obtain a desired shape according to so called vacuum forming. 
     In order to carry electronic parts chips 5, each chip 5 is inserted in each recess 1a of the bottom tape 1. After electronic parts chips 5 are inserted in the recesses 1a, the top tape 2 is adhered to the flange portion 3 of the bottom tape 1 by applying heat of a temperature between 130° C. and 200° C. Each electronic parts chip 5 is sandwiched between the top tape 2 and the center base 4 of the recess 1a such that the chip 5 is prevented from moving within the recess 1a. 
     Experiments have been made to see the advantage of the carrier according to the present invention as follows. As the electronic parts chips to be contained in the carrier are used the chips of flat package type as shown in FIG. 2. Each chip 5 has four sets of leads 5b each extending in four different directions around the periphery of the chip 5. The above-described carrier is used to carry a plurality of the chips 5, and the carrier is subjected to vibration test whose details are: 
     Vibration frequency: 10 to 55 Hz; 
     Method of Sweep: logarithmic sweep 
     Amplitude: 1.5 millimeters; 
     Duration: 6 hours with 1 minute cycle; 
     Directions: Horizontal and vertical with respect to the combs. 
     
                       TABLE 1                                                     
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             PERCENTAGE OF                                                
             OCCURRENCE                                                   
             OF COMB DEFORMATION                                          
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FIRST EMBODIMENT                                                          
               0%                                                         
CONVENTIONAL   3%                                                         
TRAY CARRIER                                                              
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     In the above, &#34;CONVENTIONAL TRAY CARRIER&#34; means the carrier 20 shown in FIG. 5 of tray type, which has hitherto been widely used for carrying electronic parts chips. The experiments have been made using the above-described first embodiment carrier and the conventional tray carrier under the same conditions mentioned in the above to compare the percentage of comb deformation. 
     FIG. 6 shows a second embodiment carrier according to the present invention. This second embodiment differs from the above-described first embodiment in that a through-hole 10 is made in the center base 4 at its substantial center. This through-hole 10 is used for recognizing the sort and the presence of the contained chip and also for pushing up the chip 5. 
     FIG. 7 shows a third embodiment carrier which is different from the above-described first and second embodiments in connection with the way of fixing the top tape 2. More specifically, a groove 11 is made in the side walls 1b of the recess 1a, and the top tape 2 is shaped so that a portion of the top tape 2 is fitted with the groove 11. In detail, projection or convex portion 12 is provided in the top tape 2 so that the convex portion 12 is engaged with the groove 11 or concave portion. The position of the groove 11 is so arranged that the chip 5 is securely sandwiched between the lower surface of the top tape 2 and the center base 4 of the recess 1a. 
     Experiments have been made in connection with the above-described second and third embodiments under the same condition described in connection with the experiments made in connection with the first embodiment carrier. As a result of vibration test, the percentages of the deformation of combs of the carried chips are shown below. 
     
                       TABLE 2                                                     
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              PERCENTAGE OF                                               
              OCCURRENCE                                                  
              OF COMB DEFORMATION                                         
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SECOND EMBODIMENT                                                         
                0%                                                        
THIRD EMBODIMENT                                                          
                0%                                                        
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     The above-described third embodiment has a particular feature that the top tape 2 can be reapeatedly used although the top tape 2 of the first and second embodiments cannot be used repeatedly. This is because no adhesive is used for attaching the top tape 2 to the bottom tape 1 in the third embodiment, and the top tape 2 is detachably secured by way of the concave portion or groove 11 and the convex portion or projection 12 of the molded bodies or members, i.e. the bottom tape 1 and the top tape 2. These convex and concave portions 12 and 11 function as engaging portions to be engaged with each other when the top tape 2 is pressed toward the bottom tape 1. Since the top tape 2 can be attached to the bottom tape 1 repeatedly, the entire carrier can also be used a plurality of times repeatedly. Therefore, substantial cost of the carrier per unit amount of electronic parts chips is remarkably low. Furthermore, since no adhesive is required in the third embodiment, the process of applying an adhesive is unnecessary. Moreover, the top tape 2 can be reattached to the bottom tape 1 when some of the chips carried in the carrier are to be unused after the top tape 2 is detached from the bottom tape 1. 
     The above-described embodiments are just examples of the present invention, and therefore, it will be apparent for those skilled in the art that many modifications and variations may be made without departing from the scope of the present invention.