Abstract:
A tray for storing a semiconductor device such as a BGA device. This tray comprises a storage portion for receiving and storing the BGA device therein. The storage portion has a wall surface which is arranged around the semiconductor device upon storing the semiconductor device. This wall surface has an area which is inclined with an angle so as to support an edge of a package of the semiconductor device but not to come into contact with wiring terminals thereof. With this arrangement, the inclined are comes into contact with only the edge of the package so as to be able to support the package.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a tray for storing a semiconductor integrated circuit device and, more particularly, to a tray for storing a semiconductor integrated circuit device such as a ball grid array type or pin grid array type semiconductor device which has wiring terminals on the lower surface of its package. 
     2. Related Background Art 
     As the package types of semiconductor devices, ball grid array type and pin grid array type are well known. In the former type, as shown in FIGS. 1 and 2, ball terminals  1  serving as wiring terminals are arranged in a matrix on the lower surface of a package  2 . The package  2  shown in FIGS. 1 and 2 is comprised of a substrate  3  and a molded resin  4  covering the upper portion of the substrate  3 . In the latter type, lead pins (not shown) are used in place of ball terminals  1 . Both of these types have features that the number of wiring terminals can be increased and that electric noise is small, compared to a general quad flat package. 
     Generally, a ball grid array type (“BGA”) semiconductor device  5 , or a pin grid array type (“PGA”) semiconductor device is stored in the storage portion of an exclusive tray to be transported or subjected to tests. A storage portion in a conventional tray is a recess having almost the same shape as that of the package of the semiconductor device. The terminals of the semiconductor device should not be brought into contact with the tray. Therefore, through holes or recesses for receiving a ball terminal group or lead pin group are formed in the central portion of the bottom surface of the storage portion. Accordingly, the conventional tray supports the peripheral portion (a portion outside the outermost ball terminals or lead pins and indicated by reference numeral  2  in, e.g., FIG. 2) of the lower surface of the package of the semiconductor device with the peripheral portion of the bottom surface of its storage portion, and restrains horizontal movement of the package with the wall surface of the storage portion. 
     When the width of the peripheral portion of the lower surface of the package is small, the ball terminals or lead pins may come into contact with the inner wall surface of the terminal-accepting hole, or the edge of the package may enter the hole. Particularly, this problem becomes conspicuous in recent years because, as the package becomes more and more compact, the width of the peripheral portion of the lower surface of the package becomes narrow. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a tray for storing a semiconductor device, such as a BGA device or PGA device, having wiring terminals on the lower surface of its package, which can reliably support the semiconductor device regardless of the width of the peripheral portion of the lower surface of the package without causing the wiring terminals to come into contact with the wall surface of the storage portion. 
     In order to achieve the above object, according to the present invention, there is provided a tray for a semiconductor device such as a BGA device, comprising a substantially planar main body and a first storage portion provided on a first surface of the main body for storing the semiconductor device. The first storage portion has a first wall surface adapted to be arranged around the semiconductor device upon storing the semiconductor device. Also, the first wall surface has a first area which is inclined with an angle so as to support an edge of the package of the semiconductor device but not to come into contact with the wiring terminals. 
     With this arrangement, the inclined first area can come into contact with only the edge of the package to support the package. 
     In order to stabilize the semiconductor device stored in the storage portion, the first wall surface is preferably formed with a second area extending upward from an upper edge of the first area. It is effective if this second area is inclined with an angle larger than the angle of the first area. 
     The tray according to the present invention is also characterized by further comprising a second storage portion provided on a second surface of the tray main body opposite to the first storage portion, that can store a semiconductor device with wiring terminals thereof facing upward when the tray is turned over, wherein when a tray of the same type is stacked on this tray, the second storage portion of one tray cooperates with the first storage portion of the other tray to form a space for storing the semiconductor device. 
     With this arrangement, the vertical movement of the semiconductor device stored in the tray can be minimized or suppressed. When the trays are stacked and turned over, the semiconductor device can be easily transported to the second storage portion of the lower tray. 
     The second storage portion may comprise a second wall surface having a third area which is arranged around the semiconductor device upon storing the semiconductor device with the wiring terminals thereof facing upward, and which is inclined with an angle so as to support the edge of the package of the semiconductor device. When the tray has such a inclined area, the semiconductor device can be supported with only the edge of its package. 
     When the package of the semiconductor device has a rectangular or square lower surface, the first storage portion is preferably comprised of four first wall surfaces arranged to form a rectangular or square shape, and the first areas of the first wall surfaces preferably respectively support edges of the lower surface of the package of the semiconductor device. 
     The present invention will be more fully understood from the detailed description given hereinbelow and the attached drawings, which are given by way of illustration only and are not to be considered as limiting the present invention. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the course of the following detailed description, reference will be made to the attached drawings in which: 
     FIG. 1 is a side view showing a BGA semiconductor device that can be stored in a tray according to the present invention; 
     FIG. 2 is a bottom view of the BGA device as shown in FIG. 1; 
     FIG. 3 is a plan view showing a tray that is constructed in accordance with the present invention for storing the BGA devices; 
     FIG. 4 is an enlarged plan view showing a portion IV of FIG. 3; 
     FIG. 5 is a bottom view of the same portion as that shown in FIG. 4; 
     FIG. 6 is a sectional view taken along the line VI—VI of FIG. 4; 
     FIG. 7 is a sectional view taken along the line VII—VII of FIG. 4; 
     FIG. 8 is a sectional view taken along the same sectional position as in FIG. 6, showing a state wherein two trays each shown in FIG. 3 are stacked; 
     FIG. 9 is a sectional view taken along the same sectional position as in FIG. 6, showing a state wherein a BGA device is arranged in the storage portion on the lower side of the tray shown in FIG. 3; 
     FIG. 10 is a sectional view taken along the same sectional position as in FIG. 6, showing a modification of a tray according to the present invention; and 
     FIG. 11 is a sectional view taken along the same sectional position as in FIG. 6, showing another modification of a tray according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and particularly, to FIG. 3, there is shown a tray  10  for storing BGA devices, having an improved construction in accordance with the present invention. The BGA device for use in the tray  10  is one shown in FIG. 1 or  2 , being designated by reference numeral  5 . The BGA device has a package whose lower surface is substantially square in shape. In this specification, it is to be understood that such terms as “upper”, “lower”, and the like are used with reference to the ordinary use state of the tray  10 , i.e., a state wherein the tray  10  is set horizontally, unless otherwise specified. In the state of FIG. 3, note that the surface which can be seen will be referred to as the upper surface of the tray  10 , and that the surface which cannot be seen will be referred to as the lower surface of the tray  10 . 
     The tray  10  of the present invention can be made from various types of materials in accordance with various types of methods. Especially, the tray  10  molded of a heat-resistant and electro-conductive synthetic resin, e.g., a polyphenylene ether-based resin mixed with a conductive filler such as carbon particles or fiber, or metal particles or fiber, a polyether sulfone-based resin, a polyether imide-based resin, a polyacryl sulfone-based resin, or a polyester-based resin is preferable, because it facilitates the manufacture, is lightweight and is easy to handle. The reason why the conductive synthetic resin is preferable is that charging in the semiconductor device to be stored must be prevented, since the semiconductor device can be damaged by static electricity. 
     The tray  10  shown in FIG. 3 comprises a substantially rectangular and planar main body  11 . The tray  10  has a plurality of linear ridges  12  formed on the upper surface of the tray main body  11 , which include those extending parallel to the longitudinal direction (long sides) of the tray  10  and those extending parallel to the widthwise direction (short sides) of the tray  10 . Longitudinal ridges  12   a  are arranged with constant intervals, and widthwise ridges  12   b  are arranged at the same constant intervals. In this manner, the ridges  12  are arranged to form a matrix, and each hollow portion of the matrix, i.e., a portion surrounded by a pair of adjacent longitudinal ridges  12   a  and a pair of adjacent widthwise ridges  12   b  serve as a first storage portion  14  for storing one BGA device  5 . 
     When a plurality of trays  10  are used as they are stacked on each other, ridges  12   e  arranged at the outermost peripheral portion of the tray  10  fit with the inner sides of outer frames  16  projecting downward from the peripheral edge of the upper tray  10 , to serve as a positioning means for positioning the tray  10  and for preventing lateral misalignment of the tray  10  (see FIG.  8 ). 
     FIG. 4 is an enlarged plan view showing a portion IV of FIG. 3, and FIG. 5 is a bottom view of the same portion as that shown in FIG.  4 . FIG. 6 is a sectional view taken along the line VI—VI of FIG. 4, and FIG. 7 is a sectional view taken along the line VII—VII of FIG.  4 . As is understood from FIGS. 4 to  7 , each storage portion  14  can store the BGA device  5  having a package  2  with a substantially square lower surface. Hence, first wall surfaces  18  of the four ridges  12  surrounding each storage portion  14  have the same shape and same size. As shown in FIGS. 6 and 7, the storage portion  14  is partitioned into a lower region  20  and an upper region  22  in the vertical direction. 
     The lower region  20  of the storage portion  14  supports the BGA device  5  when the BGA device  5  is stored horizontally and appropriately, and serves as the main region of the storage portion  14 . The lower, first wall surface areas (to be referred to as “lower wall surfaces” hereinafter)  24  of the respective ridges  12  of the lower region  20  are more inclined toward the center of the storage portion  14 . In other words, the distance, indicated by L 1  in FIG. 6, between the upper ends of the lower wall surfaces  24  that oppose each other is slightly larger than a length L 0  of one side of the package  2  shown in FIGS. 1 and 2, and the distance, indicated by L 2  in FIG. 6, between the lower ends of the lower wall surfaces  24  is smaller than L 0 . 
     Therefore, when the BGA device  5  is moved downward in the horizontal state from above to the lower region  20  of the storage portion  14 , the respective lower edges of the lower surface of the package  2  come into contact with the corresponding inclined lower wall surfaces  24  and are supported by them, as indicated by a phantom line in FIGS. 4,  6 , and  7 . As described above, since the four lower wall surfaces  24  surrounding one storage portion  14  have the same size and the same shape, the BGA device  5  is supported horizontally at the same height of the four lower wall surfaces  24 . 
     In this manner, since the BGA device  5  is supported at only the lower edges of the package  2 , it can be supported even if the width, indicated by W in FIG. 2, of the peripheral portion  6  of the lower surface of the package  2  is smaller than the reference size. 
     Note that when the BGA device  5  is supported, the ball terminals  1  should not come into contact with the lower wall surfaces  24  of the storage portion  14 . Hence, the angle of the lower wall surfaces  24  with respect to the horizontal plane, indicated by α in FIG. 6, must be necessarily larger than the angle formed by the lower edges of the package  2  and the outermost ball terminals  1 , indicated by β in FIG.  1 . Even when this condition is satisfied, if the angle α of the lower wall surfaces  24  becomes less than 40°, the BGA device  5  may be moved in the storage portion  14  when a very small vibration is applied to the tray  10 . Therefore, the angle α is preferably 40° or more. Also, when the angle α of the lower wall surfaces  24  exceeds 70°, the package  2  bites into the lower wall surfaces  24  and becomes difficult to remove. Therefore, the angle α is preferably 70° or less. 
     Further, while the BGA device  5  is supported, the ball terminals  1  should not come into contact with a bottom surface  26  of the storage portion  14 . For this reason, the height, indicated by H 1  in FIG. 6, from the bottom surface  26  of the storage portion  14  to a package support point S is set larger than the length, indicated by h in FIG. 1, from the lower surface of the package  2  to the lower ends of the ball terminals  1 . 
     When the BGA device  5  supported by the lower wall surfaces  24  is displaced, second wall surface areas (to be referred to as “upper wall surfaces” hereinafter)  28  of the respective ridges  12  in the upper region  22  of the storage portion  14  restrain this displacement. The angle, indicated by γ in FIG. 6, of the upper wall surfaces  28  with respect to the horizontal plane is set larger than the angle α of the lower wall surfaces  24  and is preferably 85° to 90°. In this manner, with the upper wall surfaces  28  sharply rising from the upper edges of the lower wall surfaces  24 , even if the BGA device  5  is displaced in the horizontal direction, when the lower edges of the package  2  reach boundaries  30  between the lower and upper wall surfaces  24  and  28 , further horizontal movement of the BGA device  5  is prohibited by the upper wall surfaces  28 . 
     The height, indicated by H 2  in FIG. 6, from the package support point S to the upper edges of the upper wall surfaces  28  is preferably larger than the thickness of the package  2 . Then, for example, when a flat plate (not shown) is placed on the tray  10 , the BGA device  5  is completely stored in the space surrounded by the lower surface of the flat plate and the storage portion  14 , and can be avoided from being interfered with the flat plate. In order to allow the BGA device  5  to be stored in the storage portion  14  easily, the upper edges of the upper wall surfaces  28  are preferably chamfered as indicated by numerals  32 . 
     The lower and upper wall surfaces  24  and  28  described above need not extend over the entire lengths of the ridges  12  surrounding the storage portion  14 . In the shown embodiment, the ridges  12  at the corners of the storage portion  14  may be formed thin. In this case, the corners of the package  2  float. 
     With BGA device storage trays, for example, when the ball terminals  1  are to be inspected, sometimes the empty second tray is stacked on the first tray storing the BGA devices  5 , and these trays are turned over in the stacked state, so that the ball terminals  1  of the BGA devices  5  face upward. Generally, storage portions are formed on the lower side of the second tray as well so that the second tray can also store the BGA devices when the trays are turned over. 
     Hence, the tray  10  of the shown embodiment also has a plurality of second storage portions  34  in its lower side. These lower side storage portions  34  correspond in number to the upper side storage portions  14  described above, and are formed immediately under the upper side storage portions  14 . Accordingly, as shown in FIG. 8, when a tray  10 B of the same type as a tray  10 A is stacked on the tray  10 A and outermost ridges  12   e  of the lower tray  10 A and an outer frame  16  of the upper tray  10 B are engaged with each other, each lower side storage portion  34  of the upper tray  10 B is located to cover a corresponding upper side storage portion  14  of the lower tray  10 A, so that a space for storing one BGA device  5  is formed between these storage portions  14  and  34 . 
     This will be described in more detail. As is understood from FIG. 5, each storage portion  34  on the lower side of the tray  10  is made up of four projecting pieces  36  projecting downward from the lower surface of the tray main body  11 . The projecting pieces  36  are arranged at the corners of the storage portion  34 , i.e., positions corresponding to the intersections of the ridges  12  on the upper surface of the tray  10 . The projecting pieces  36  each forming an L shape when seen in a horizontal section and are positioned such that their inner wall surfaces or second wall surfaces  38  restrain the corners of the package  2 . When the two trays  10 A and  10 B are stacked, the four projecting pieces  36  defining one lower side storage portion  34  are fitted with the corner portions of the corresponding upper side storage portion  14 , and outer wall surfaces  40  of the respective projecting pieces  36  face the inner surfaces of the thin portions of the ridges  12 . In this state, a bottom surface  26  of the upper side storage portion  14  of the lower tray  10 A, a bottom surface  42  of the lower side storage portion  34  of the upper tray  10 B, the linear ridges  12 , and the projecting pieces  36  form a closed space. The BGA device  5  is stored in this space such that its movement is prevented or minimized in the vertical direction as well. 
     The minimum distance between the opposing wall surfaces  38  is larger than the maximum length of the BGA package  2 . Hence, when the tray  10  is turned over and the BGA devices  5  are stored in its lower storage portions  34 , the upper surfaces of the packages  2  are in contact with the bottom surfaces  42  of the storage portions  34 , as shown in FIGS. 5 and 9. 
     In the above embodiment, the sizes, positions, and shapes of the respective parts of the storage portions  14  and  34 , the inclination angles of the wall surfaces  18  and  38 , and the like may be changed in various manners in accordance with the size of the BGA device to be handled, the material of the package, and the like, and may be adjusted through experiments and simulations. For example, the possible movement of the BGA device  5  occurred when a vibration is applied to the tray  10  includes various types. The lower edges of the package may slide on the lower wall surfaces  24  in the longitudinal or widthwise direction of the tray  10 . Alternatively, the BGA package  2  may vertically move to come into contact with the lower surface of the upper tray  10 B, may rotate about the central point of the BGA  5  as the center, or may swing about opposing corners as fulcrums. Therefore, conditions with which the ball terminals  1  do not always come into contact with the surfaces of the tray  10  must be determined while considering the fact that these movements can occur in the BGA device  5 . When satisfying these conditions, the wall surfaces  24 ,  28 , and  38  need not always be flat surfaces, but may be modified to be curved to form projections or recesses. 
     Although the preferred embodiment of the present invention has been described in detail so far, the present invention is not limited by it. For example, in the above embodiment, the projecting pieces  36  on the lower side of the tray do not support the BGA device  5 . However, as shown in FIG. 10, the inner wall surfaces of the projecting pieces  36  may form as inclined surfaces or third wall surface areas  44 , and the upper edges of the package  2  may be supported by the wall surfaces  44 . Alternatively, as shown in FIG. 11, step portions  46  may be formed on the inner wall surfaces of the projecting pieces  36 , and the peripheral portion of the upper surface of the package  2  may be supported by the step portions  46 . 
     In the above embodiment, the present invention is applied to the BGA device tray  10 . The present invention may also be applied to a tray for storing PGA devices or other semiconductor devices each having wiring terminals on the lower surface of the package. 
     Although, the above embodiment can store a semiconductor device with a substantially square package, the present invention may be applied to a semiconductor device having a package of another shape. In such a case, inclined wall surface areas for supporting the edges of the package may be formed on the wall surfaces of the storage portion that surround the semiconductor device continuously or discontinuously. 
     As has been described above, with the tray according to the present invention, even if the wiring terminal portions are disposed at positions near the peripheral edge of the lower surface of the package of a semiconductor device, the tray can support the semiconductor device. Since this support is achieved at only the edges of the package, ball terminals can be prevented from coming into contact with the wall surfaces or bottom surface of the storage portion. Therefore, with the tray of the present invention, when a semiconductor device is stored and transported, damage, deformation, and contamination of the ball terminals caused by contact with the wall surface of the storage portion can be prevented. 
     From the invention thus described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.