Arrangement of semiconductor devices and method of and apparatus for mounting semiconductor devices

Abstract: Semiconductor devices are each arranged such that a semiconductor chip (6) is disposed on a film carrier (1), fingers (3) of the film carrier are respectively connected to a multiplicity of electrodes provided on the semiconductor chip, and the fingers are then trimmed, or the fingers are trimmed after the semiconductor chip and parts of the fingers are sealed with a resin (12) or the like. The semiconductor devices thus arranged are respectively mounted on both obverse and reverse surfaces of a substrate at mutually opposing positions thereof, the substrate having electrically conductive patterns (21) formed on the both surfaces thereof. The semiconductor devices are sealed with a resin or the like so as to be formed integrally with the substrate.

Description: Field of the Invention: The present invention relates to an arrangement of semiconductor devices on a substrate, and a method of and an apparatus for mounting semiconductor devices using a film carrier. Description of the Related Art: In general, semiconductor devices are manufactured in the following process: Each semiconductor chip is mounted on die pads provided on a lead frame, external electrodes of the semiconductor chip and the leads (terminals) of the lead frame are respectively connected to each other by means of a bonding wire, and after the assembly is packaged with a thermosetting resin such as epoxy resin, the leads are trimmed. In conjunction with the recent trend toward the creation of increasingly compact and thin electronic apparatuses, with respect to semiconductor devices used in such apparatuses, the emergence of thin and compact semiconductor devices has been hoped for in order to realize the mounting of the semiconductor devices with a high degree of mounting density. To meet this demand, semiconductor devices have come to be used which are of a type in which each semiconductor chip is disposed in a device hole of a film carrier, the electrodes of the semiconductor chip and the fingers of the film carrier are directly connected to each other, and this assembly is packaged with a sealing material constituted by a liquid resin (e.g., epoxy resin) by means of printing or potting. Fig. 7 is a top plan view illustrating semiconductor devices using a film carrier. A film carrier (hereinafter referred to as the film) 1 having a thickness of 25 - 125 µm or thereabouts is provided with device holes 2 (2a, 2b, ...) having areas greater than the surface areas of semiconductor chips 6 (6a, 6b, ...) which will be described later, the device holes 2 being arranged at equal intervals in a longitudinal direction. A multiplicity of fingers 3 are constituted by a metallic foil provided with a thickness of about 10 - 70 µm and a width of about 30 - 300 µm and having a high electric conductivity such as copper. The fingers 3 are disposed on the film 1, each having a free end which projects into the device hole 2. Sprocket holes 5 are used to convey the film 1. Fig. 8 is a schematic diagram illustrating an example of an apparatus for mounting semiconductor chips on the above-described film 1. In operation, the semiconductor chip 6 mounted on a pair of chip bases 8 is positioned in place by a pair of positioning guides 9. Meanwhile, the film 1 is fed by means of a pair of sprockets (not shown) while being guided by a pair of tape rails 10 in a direction in which the semiconductor chips 6 are fed. The film 1 is then stopped at a position where its relevant device hole 2 is positioned immediately above the semiconductor chip 6. Subsequently, a multiplicity of pads provided on the semiconductor chip 6 and the fingers are respectively aligned with each other. Then, a heated bonding tool 11 is lowered to press the fingers 3, so that the fingers 3 are formed into a predetermined angle and are fused to the respective pads 4 and connected thereto. The film 1 is then moved, and the fingers 3 are trimmed, or the fingers 3 are trimmed after the semiconductor chip 6 and parts of the fingers 3 are sealed with a sealing resin by means of squeeze printing, potting, or other similar method, thereby manufacturing a semiconductor device D. As shown in Figs. 9 and 10, for example, the semiconductor D manufactured as described above is mounted on a printed circuit board 20 with its active surface facing the printed circuit board 20, and after the fingers 3 are respectively soldered to a conductive pattern 21 formed on a surface of the printed circuit board 20, peripheral surfaces of the semiconductor chip 6 and the fingers 3 are sealed with a resin or the like 12 by means of squeeze printing, potting, or other similar method. The printed circuit board 20 with the above-described semiconductor device D mounted thereon has characteristics that the printed circuit board 20 can be made thinner than a conventional one, and that the degree of mounting density can be enhanced. However, if the semiconductor device D is sealed with the resin or the like 12, a phenomenon occurs in which the printed circuit board 20 is curved or warped in a concave manner with respect to the side where the semiconductor devices D are mounted, due to shrinkage on curing of the resin or the like 12. Consequently, there are cases where compression cracks occur in the semiconductor chip 6. In addition, in cases where the curved printed circuit board 20 is secured to a frame or the like, the curvature must be corrected. At that time, however, the fingers 3 sealed with the resin or the like 12 can be cut off, and, hence, there have been problems that the yield of production is low and that such products lack reliability. Furthermore, although the technique described above is capable of enhancing the degree of mounting density as compared with the conventional art, there are limitations to it, and it is considered difficult to improve the degree of mounting density to a substantial level in the future. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an arangement of semiconductor devices on a substrate, a method of, and an apparatus for, mounting semiconductor devices which are capable of preventing the occurrence of curving or warping in a substrate at the time of mounting the semiconductor devices and of substantially improving the degree of mounting density, thereby overcoming the above-described drawbacks of the conventional art. This object is achieved with an arrangement of semiconductor devices as claimed in claim 1, a method of mounting semiconductor devices as claimed in claim 2 and an apparatus for mounting semiconductor devices as claimed in claim 3. In operation, a necessary number of semiconductor devices are first secured to one surface of the substrate, the substrate is rotated 180°, and the other semiconductor devices are secured to the other surface in face-to-face relation with the semiconductor devices already mounted. Then, the semiconductor devices mounted on both surfaces of the substrate are respectively sealed with the resin or the like, and the both sides are simultaneously heated to harden, thereby becoming integrally formed with the substrate. In addition, a semiconductor device is placed on the lower bonding tool, while another semiconductor device is mounted on the upper surface of the substrate. Then, the work table is moved so that the semiconductor device is aligned with the bonding tool. Subsequently, the upper bonding tool is lowered and the lower bonding tool raised to bring the two semiconductor devices to be respectively brought into contact with the obverse and reverse surfaces of the substrate. If the semiconductor devices are then subjected to pressurization and heating, the semiconductor devices can be connected to the substrate. The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically illustrating an embodiment of the present invention; Fig. 2 is a partial enlarged view thereof; Figs. 3A and 3B are diagrams illustrating an example of a method of mounting in accordance with the present invention; Figs. 4 and 5 are top plan views respectively illustrating other embodiments of the present invention; Fig. 6 is a perspective view of an apparatus for mounting semiconductor devices in accordance with an embodiment of the present invention; Figs. 7 and 8 are diagrams illustrating a conventional example of manufacturing a semiconductor device using a film carrier; and Figs. 9 to 11 are diagrams illustrating a conventional example of mounting semiconductor devices. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a cross-sectional view schematically illustrating an embodiment of the present invention, and Fig. 2 is a partial enlarged view thereof. It should be noted that, in these drawings, those parts that are identical with or correspond to those of the conventional art shown in Figs. 7 to 11 are denoted by the same reference numerals. In the present invention, the assembling of relevant components is effected as follows: A substrate 20 is provided with electrically conductive patterns 21 on both sides thereof. A pair of semiconductor devices D are respectively disposed on both obverse and reverse surfaces of the substrate 20 at an equidistance therefrom in such a manner as to be disposed symmetrically with respect to the substrate 20 and oppose each other with their active surfaces facing the substrate 20. Then, after fingers 3 are respectively connected to the conductive patterns 21, the peripheral surfaces of the semiconductor chip 6 and the fingers 3 are sealed with a resin or the like 12. A description will now be given of an example of the procedure of mounting in accordance with the present invention. As shown in Fig. 3A, the semiconductor device D is mounted on one side (e.g., obverse surface) of the substrate 20 using a bonding tool 24 for the semiconductor device D in such a manner that the active surface of the semiconductor device D is opposed to the substrate 20. At this time, the fingers 3 and the conductive pattern 21 to which solder has been applied are aligned with each other. Then, the fingers 3 or the fingers 3 and a film 1 are pressed and heated by the bonding tool 24, thereby allowing the respective fingers 3 to be connected to the conductive pattern 21. In this manner, all the necessary semiconductor devices D are mounted on the obverse surface of the substrate 20. Next, the substrate 20 is rotated 180° and is placed on a holding plate 22 provided with recesses 23 in correspondence with a mounting apparatus for mounting the semiconductor devices D, and the semiconductor devices D are positioned in the recesses 23, respectively. In this state, in the same way as described above, each of the semiconductor devices D is mounted on the other side (reverse surface) of the substrate 20 at a position of symmetry with the semiconductor device mounted on the obverse side and in opposing relation thereto. Upon completion of the mounting of the semiconductor devices D, the peripheral surfaces of each of the semiconductor chips 6 and the fingers 3 (possibly including the film 1) on the side concerned (rear surface) of the substrate 20 are first sealed with the resin or the like 12. Then, the substrate 20 is rotated 180°, and the semiconductor devices D mounted on the opposite side (obverse surface) are sealed with the resin or the like 12 in the same manner as described above. It should be noted that, in this case, if a through hole 20a is provided in the substrate immediately below each of the semiconductor chips 6, and the upper and lower portions of the resin or the like 12 are connected to each other through this through hole 20a, the sealing strength can be improved further. Finally, the substrate 20 with the semiconductor devices D mounted thereon and sealed is placed in a heating furnace or the like, and the seal portions on both surfaces are heated simultaneously to allow the resin or the like 12 to be cured so as to be formed integrally with the substrate 20. Thus, in accordance with the present invention, since the semiconductor devices D are mounted on both surfaces of the substrate 20 and are sealed with the resin or the like 12, and the resin or the like 12 on both surfaces is cured simultaneously, the substrate 20 is prevented from becoming curved or warped due to shrinkage on curing. It should be noted that, if the semiconductor devices D are mounted on obverse and reverse sides of the substrate at positions which do not correspond to each other, as shown in Fig. 3B, an uneven stress would be applied to the semiconductor device D mounted on the opposite surface, so that a crack may occur in the semiconductor chip 6 or the fingers 3 may be cut, and this arrangement is therefore undesirable. Fig. 4 is a top plan view illustrating another embodiment of the present invention. In this embodiment, the semiconductor devices D are arranged in rows on both surfaces of the substrate 20 in such a manner as to oppose each other in the thicknesswise direction of the substrate 20, the semiconductor devices in one row being offset from those in an adjacent row, i.e., arranged in a zigzag manner. This arrangement not only permits the mounting of the semiconductor devices D at a greater density but further improves the strength of the substrate 20 by preventing the curving or warping of the substrate 20. Furthermore, Fig. 5 illustrates still another embodiment of the present invention in which the semiconductor devices D are arranged in rows on both sides of the substrate 20 in such a manner as to oppose each other in the thicknesswise direction of the substrate 20 such that the longitudinal direction of each of the semiconductor devices D, in which direction the semiconductor devices D are liable to undergo cure shrinkage, is made substantially parallel with the transverse direction of the substrate 20, in which direction the substrate 20 is not liable to curve or warp. This arrangement makes it possible to prevent the curving or warping of the substrate 20 even when a multiplicity of semiconductor devices D are mounted thereon. Fig. 6 is a perspective view of an embodiment of a mounting apparatus for semiconductors in accordance with the present invention. This mounting apparatus comprises the following components or portions: a base 31; a gate-type frame 32 provided on the base 31; work tables 33, 33a mounted on the base 31 and capable of moving on the base 31 in cooperation therewith in the X-Y directions by means of a motor, compressed air, or the like; a support rod 34 fitted vertically slidably in a bore 36 provided in the gate-type frame 32; a support rod 34a which is fitted vertically slidably in a bore (not shown) provided in the base 31 in face-to-face relation with the support rod 34; bonding tools 35, 35a fixed to the distal ends of the support rods 34, 34a, respectively, in face-to-face relation therewith; and support rods 34b, 34c and bonding tools 35b, 35c having arrangements similar to those described above. The support rods 34 - 34c are respectively driven by compressed air, a rack and a pinion, and the like (not shown) so as to move vertically through the bores 36, 36a. A description will now be given of the operation of this apparatus arranged as described above. To facilitate the description, a case will be cited in which two semiconductor devices D, D₁ are respectively mounted on both sides of the substrate 20 in such a manner as to oppose each other by using the bonding tools 35, 35a. (1) The substrate 20 is secured on the work tables 33, 33a by means of screws 37 or the like. At this juncture, the bonding tools 35 to 35C are kept at their uppermost or lowermost positions, respectively. (2) The semiconductor device D is placed on the bonding tool 35a below the substrate 20, while the other semiconductor device D₁ is placed on a conductive pattern (not illustrated) provided on the upper surface of the substrate 20. (3) The work tables 33, 33a, and hence the substrate 20, are moved in the X-Y directions so as to align the semiconductor device D1 with the bonding tool 35. At this time, since the bonding tools 35 and 35a are opposed to each other accurately, the position of the semiconductor device D mounted on the bonding tool 35a and the position of the semiconductor device D1 on the substrate 20 are also aligned with each other accurately. (4) The bonding tool 35a is raised to bring the terminals of the semiconductor device D into contact with the conductive pattern, and the bonding tool 35 is lowered to be brought into contact with the semiconductor device D1. As a result, the semiconductor devices D, D1 are clamped by and held between the bonding tools 35, 35a with the substrate 20 as a center. (5) In this state, if the terminals of the semiconductor devices D, D1 are pressurized and heated by the bonding tools 35, 35a, the terminals are connected to the conductive pattern. (6) When the connection of the semiconductor devices D, D1 is completed, the bonding tool 35 is raised and the bonding tool 35a lowered, and ensuing semiconductor devices are mounted in the manner described above. Although in the foregoing embodiment a description has been given of a case in which the semiconductor devices D, D1 are mounted by means of the pair of bonding tools 35, 35a, bonding may be effected by using the other pair of bonding tools 35b, 35c separately or simultaneously, or three or more pairs of bonding tools may be provided. Thus, in accordance with the present apparatus, it is possible to effect the bonding of the semiconductor devices D simultaneously on both the obverse and reverse sides of the substrate 20 with a simple structure, so that the time required for bonding can be reduced substantially. In the foregoing embodiment, a description has been given of a case in which in the state in which the semiconductor chip 6 is secured to the film 1, the fingers 3 are trimmed and are connected to the conductive pattern 21 of the substrate 20, and the assembly is then provided with sealing with the resin or the like 12. However, an arrangement may be alternatively provided such that after the semiconductor chip 6 is secured to the film 1 and is sealed with the resin or the like, and the fingers are trimmed, the semiconductor devices in this state are respectively provided on both the obverse and reverse sides of the substrate 20 and are further sealed with the sealing or the like 12. In addition, although a description has been given of a case in which the semiconductor devices D are mounted with their active surfaces facing the substrate 20, the semiconductor devices D may be mounted with their active surfaces oriented in directions away from the substrate 20, respectively. As is apparent from the foregoing description, in accordance with the present invention, the semiconductor devices are respectively secured to the opposite sides of the substrate at symmetrical positions thereof, and after the assembly is sealed with a resin or the like, the both sides are heated to be cured, thereby becoming integral with the substrate. Accordingly, the cure shrinkage of the resin and the like is offset, so that the substrate is prevented from becoming curved or warped toward one side. In consequence, it is possible to prevent the semiconductor chips from becoming cracked and the fingers from becoming cut off, thereby making it possible to obtain a high-quality, highly-reliable product at a high rate of yield. Furthermore, since the semiconductor devices are mounted on both sides of the substrate, it is possible to substantially improve the mounting density. In addition, since the semiconductor devices are arranged on the substrate in face-to-face relation with their active surfaces facing the substrate, the transmission of light to the active surfaces which are vulnerable to light is practically nil, so that there is no occurrence of a malfunctioning due to light. Furthermore, since unnecessary noise can be suppressed, it is possible to control the emission of noise to the outside. Since the semiconductor devices are arranged with their active surfaces facing the substrate in such a manner as to oppose each other, it is possible to control the entrance of moisture through the substrate, so that reliability of the semiconductor devices can be improved. Additionally, since the semiconductor devices can be simultaneously connected to the opposite sides of the substrate using at least a pair of upper and lower bonding tools, the present invention offers a large advantage in that the time required for bonding can be reduced substantially.

Claims: An arrangement of semiconductor devices (D) on a substrate (20), in which each semiconductor device (D) is composed of a semiconductor chip (6) disposed on a film carrier having electrically conductive fingers (3) respectively connected to electrodes on the semiconductor chip, pairs of said semiconductor devices (D) being mounted on the substrate (20), each pair consisting of first and second semiconductor devices (D) mounted at mutually opposing positions on opposite surfaces of the substrate (20), the substrate having electrically conductive patterns formed on both said surfaces, and in which each semiconductor device (D) on the substrate is covered with a sealing resin (12). A method of mounting semiconductor devices, comprising the steps of: preparing a multiplicity of semiconductor devices (D) which are each arranged such that a semiconductor chip (6) is disposed on a film carrier (1), fingers (3) of said film carrier are respectively connected to a multiplicity of electrodes provided on said semiconductor chip, and said fingers are then trimmed, or said fingers are trimmed after said semiconductor chip and parts of said fingers are sealed with a resin (12), and preparing a substrate (20) having electrically conductive patterns formed on both surfaces thereof; mounting said semiconductor devices (D) respectively on both obverse and reverse surfaces of said substrate at mutually opposing positions thereof; and sealing said semiconductor devices with a resin (12) so as to form said semiconductor devices integrally with said substrate. An apparatus for mounting semiconductor devices comprising: a base (31), a frame (32) secured to said base; a work table (33,33a) which is mounted on said base in such a manner as to be movable in the X-Y directions and to which a substrate is secured; and at least a pair of bonding tools (35,35a) disposed on said base and the frame in such a manner as to oppose each other on both sides of said substrate and to be vertically movable.

Inventors: SATO EIICHI C O SEIKO EPSON CO, SATO, EIICHI, C/O SEIKO EPSON CORPORATION
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1990
Main classification: H05K13
IPC codes: H05K1, H01L21, H05K3, H01L23