Semiconductor device of surface-mount type

Abstract: A semiconductor device of surface-mount type comprises a circuit strip 10 tailored to have patterns 12 projected, a semiconductor element 14 fixedly joined to the circuit strip 10, and pads 15 on the semiconductor element 14 electrically connected by wires 17 to the corresponding patterns 12 on the circuit strip 10 and sealed with a resin material. While the surface-mount type semiconductor device is adapted to be simple in structure and capable of high-density mounting, an appliance on which the semiconductor device is mounted and a method of producing the semiconductor device are also provided.

Description: BACKGROUND OF THE INVENTION The present invention relates to a semiconductor device, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device. The demand for minimizing the size or thickness of semiconductor devices including semiconductor integrated circuit chips has sharply been increased, particularly in IC packaging. A chip scale package technique (CSP) is known for producing IC packages, namely semiconductor packaged IC chips for use as memories, which are reduced to a size almost equal to the size of an IC element. One of such CSP techniques is disclosed in Japanese Patent Laid-open Publication No. H8-125066. Fig. 8 is a cross sectional view of a conventional chip scale package, in which a semiconductor element 1 has pads 2 mounted on a center region of the lower side thereof. A connector lead frame 4 is located and bonded by an electrically insulating adhesive 3 to the lower side of the semiconductor element 1. The connector lead frame 4 is connected by wires 5 to the pads 2 of the semiconductor element 1. The connector lead frame 4 has partially projections thereof formed by e.g. etching. The entire assembly is sealed with a resin material 6, except for the projections of the lead frame 4, which must be exposed. The exposed projections of the connector lead frame 4 are coated with doses of solder paste which serve as external electrodes 7. The chip scale package is now completed. However, such a conventional semiconductor device has some disadvantages that the forming of the connector lead frame by etching is an intricate task as hardly implemented by a common pressing technique such as stamping which is intended to be cost-cutting, and that the sealing with resin is difficult since a particular region has to be exposed, hence being deficient in technical quality. From US 5,347,159 a semiconductor device is known comprising a box-shaped member 50 enclosing the semiconductor chip with the exception of a main surface 22 where contact pads 28 are formed, which are connected to leads 48 formed outside the box-shaped member 50. From US 5,583,375 semiconductor device is known having inner leads secured with insulating adhesive films to the principle surface of a semiconductor chip and electrically connected to the respective external terminals of the chip. The semiconductor device that can be about the size of the chip is so configured that an outer lead is continously extended from each inner lead up to the rear surface opposite to the principle surface of the semiconductor chip in order to hold the leads and an external device in conduction. DE 9417734 U1 discloses a semiconductor device wherein semiconductor chips are mounted on an intermediate substrate which comprises leads connected with bonding pads of the semiconductor chips. The intermediate substrate comprises at least one opening through which leads from the bonding pads of the semiconductor chips to the contact surfaces of the lower side of the intermediate substrate are provided. SUMMARY OF THE INVENTION The present invention is directed towards overcoming the above disadvantages attributed to conventional technology and its primary object is to provide a novel, improved semiconductor device of surface-mount type which is simple in structure and capable of high-density mounting, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device. It is another object of the present invention to provide a novel, improved semiconductor device of surface-mount type in which patterns are formed on a circuit strip by a printed circuit board technique thus to have a circuitry arrangement at higher accuracy and elaboration thus contributing to the high-density mounting, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device. It is a further object of the present invention to provide a novel, improved semiconductor device of surface-mount type in which a circuit strip is equipped with ribs which serve as barriers to prevent overflow of a fluid resin material thus permitting the procedure to be minimized and avoiding deflection of the bonding region of the circuit strip to a semiconductor element for giving a higher bonding strength, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device. It is a still further object of the present invention to provide a novel, improved semiconductor device of surface-mount type in which a semiconductor element is wrapped with both side ends of a circuit strip thus increasing the mechanical strength even after mounted on a circuit board and ensuring a higher reliability, and in addition, since the element being wrapped with the circuit strip made of a metallic material, giving the shielding effect and thus improving the electrical characteristics, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device. It is a still further object of the present invention to provide a novel, improved semiconductor device of surface-mount type which is matched to reflow conditions required for mounting on a circuit board and allows patterns on a circuit strip to be used for inspecting the electrical conduction after completion or mounting, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device. It is a still further object of the present invention to provide a novel, improved semiconductor device of surface-mount type which is tailored for a towering arrangement in which two or more devices are mounted one over the other thus permitting their processing capability to be optimized without increasing the mounting area on a circuit board, an appliance on which the semiconductor devices are mounted, and a method of producing the semiconductor device. For achievement of the object, a semiconductor device as defined in claim 1 is provided. BRIEF DESCRIPTION OF THE DRAWINGS The above and other features of the invention and the concomitant advantages will be better understood and appreciated by persons skilled in the field to which the invention pertains in view of the following description given in conjunction with the accompanying drawings which illustrate preferred embodiments. In the drawings: Fig. 1 illustrates a first part of a procedure of producing a semiconductor device of a first embodiment according to the present invention; Fig. 2 illustrates a second part of the procedure of producing the semiconductor device of the first embodiment; Fig. 3 shows a procedure of producing a semiconductor device of a second embodiment according to the present invention; Fig. 4 illustrates a first part of a procedure of producing a semiconductor device of a third embodiment according to the present invention; Fig. 5 illustrates a second part of the procedure of producing the semiconductor device of the third embodiment; Fig. 6 shows a procedure of mounting on a circuit board a semiconductor device of a fourth embodiment according to the present invention; Fig. 7 illustrates a procedure of producing a semiconductor device of a fifth embodiment according to the present invention; and Fig. 8 is a cross sectional view of a conventional chip scale package. PREFERRED EMBODIMENTS OF THE INVENTION Preferred embodiments of the present invention will be described in more detail in the form of a semiconductor device, an apparatus for mounting the semiconductor on a circuit board, and a method of producing the semiconductor device, referring to the accompanying drawings. First Embodiment A procedure of producing the semiconductor device of a first embodiment of the present invention will be described referring to Figs. 1 and 2. (1) The procedure starts with preparing a circuit strip 10 made of e.g. a metal which has an insulating layer 11 and an array of patterns 12 formed on one side thereof as best shown in a plan view of Fig. 1(a) and a side view of Fig. 1(a)'. The circuit strip 10 has a through opening 13 provided in a center region thereof. (2) The circuit strip 10 is tailored by pressing or other means to have the patterns 12 arcuately projected as shown in a plan view of Fig. 1(b) and a side view of Fig. 1(b)'. (3) A semiconductor element 14 is prepared before being mounted to the circuit strip 10 as shown in a plan view of Fig. 1(c) and a side view of Fig. 1(c)'. The semiconductor element 14 has a row of pads 15 provided on a center region thereof for bonding. (4) An amount of adhesive or more specifically, a frame-shaped film of adhesive 16 for applying about the pads 15 on the semiconductor element 14 in this embodiment is provided as shown in a plan view of Fig. 1(d) and a side view of Fig. 1(d)'. (5) The circuit strip 10 and the semiconductor element 14 are fixedly joined to each other by the adhesive 16 as shown in a plan view of Fig. 2(a) and a side view of Fig. 2(a)', where the pads 15 on the semiconductor element 14 are exposed across the through opening 13. (6) The pads 15 are electrically connected by wires 17 to the corresponding patterns 12 on the circuit strip 10 respectively as shown in a plan view of Fig. 2(b) and a side view of Fig. 2(b)'. (7) A limited region about the through opening 13 of the circuit strip 10 is coated with a resin material 18 to complete a semiconductor device as shown in a plan view of Fig. 2(c) and a side view of Fig. 2(c)'. As the result, the wires 17 connecting between the pads 15 and the patterns 12 on the circuit strip 10 are completely sealed in the resin material 18. (8) The finished semiconductor device is then mounted to a circuit board 19 as in a plan view of Fig. 2(d) and a side view of Fig. 2(d)'. More specifically, the patterns 12 on the circuit strip 10 are bonded by e.g. soldering to corresponding patterns (not shown) provided on the upper side of the circuit board 19 so that the semiconductor device is securely mounted. As understood, the conventional steps of securing to the surface of a semiconductor element a lead frame which has been elaborated to a particular shape by a high-cost method such as etching and after connecting with wires, covering the assembly with a resin material entirely except specific regions being exposed, and forming external electrodes on the exposed regions of the lead frame are replaced by the procedure of the first embodiment for bending a circuit strip made of a metal, bonding a semiconductor element to the circuit strip, and after connection with wires, covering a limited region with resin to seal the wires. This allows the semiconductor device to be simple in construction. Also, the patterns can be formed on the circuit strip by a known printed circuit board technology and their dimensional accuracy will thus be improved hence contributing to the realization of higher density mounting. Second Embodiment A procedure of producing the semiconductor device of a second embodiment of the present invention will be described referring to Fig. 3. (1) The procedure starts with preparing a circuit strip 20 made of e.g. a metal which has an insulating layer 21 and an array of patterns 22 formed on one side thereof as best shown in a plan view of Fig. 3(a) and a side view of Fig. 3(a)'. The circuit strip 20 has a through opening 23 provided in a center region thereof, similar to that of the first embodiment. In addition, the circuit strip 20 of the second embodiment has ribs 24 provided on both lengthwise ends thereof. (2) The circuit strip 20 like the first embodiment is tailored by pressing or other means to have the patterns 22 arcuately projected as shown in a plan view of Fig. 3(b) and a side view of Fig. 3(b)'. Simultaneously, the ribs 24 of the second embodiment are bent in the same direction. (3) Like the first embodiment, a semiconductor element 25 is bonded by a film of adhesive 26 to the circuit strip 20 as shown in a plan view of Fig. 3(c) and a side view of Fig. 3(c)'. Then, patterns 22 on the circuit strip 20 are electrically connected by wires 28 to bonding pads 27 provided on the semiconductor element 25 and exposed across the through opening 23. (4) When the circuit strip 20 is partially sealed with a fluid of resin material 29, the semiconductor device is completed as shown in a plan view of Fig. 3(d) and a side view of Fig. 3(d)'. The ribs 24 in the second embodiment serve as barriers (or dams) to prevent overflow of the resin material 29 during the sealing. The second embodiment where the ribs are provided for preventing the resin material from overflowing to the circuit strip is more advantageous than the first embodiment in facilitating the procedure with the use of a fluid resin material. Also, the bonded region is reinforced by the ribs to prevent deflection and will thus be enhanced in the physical strength. Third Embodiment A procedure of producing the semiconductor device of a third embodiment of the present invention will be described referring to Figs. 4 and 5. (1) The procedure starts with preparing a circuit strip 30 made of e.g. a metal which has an insulating layer 31 and an array of patterns 32 formed on one side thereof and a through opening 33 therein as best shown in a plan view of Fig. 4(a) and a side view of Fig. 4(a)'. (2) The circuit strip 30 like the first embodiment is bent to an arcuate shape (J bend) by pressing or other means and then, bonded by adhesive 35 to a semiconductor element 34 as shown in a plan view of Fig. 4(b) and a side view of Fig. 4(b)'. (3) Like the first embodiment, bonding pads 36 provided on the semiconductor element 34 and exposed across the through opening 33 are electrically connected by wires 37 to corresponding patterns 32 of the circuit strip 30 as shown in a plan view of Fig. 5(a) and a side view of Fig. 5(a)'. (4) A limited region about the through opening 33 of the circuit strip 30 is coated with a resin material 38 to seal the wires 37, like the first embodiment, and both side ends of the circuit strip 30 are bent by pressing or other means so that they wrap the semiconductor element 34 as shown in a plan view of Fig. 5(b) and a side view of Fig. 5(b)'. (5) As the result, the semiconductor device having a J-bend configuration is completed as shown in a plan view of Fig. 5(c) and a side view of Fig. 5(c)'. As the semiconductor element 34 is wrapped in the circuit strip 30, the semiconductor device of the third embodiment is increased in the mechanical strength while mounted on an unshown circuit board. The semiconductor device of the third embodiment in which the semiconductor element is wrapped in the circuit strip made of a metal is also enhanced in the shielding effect for improving the electrical characteristics as well as increased in the mechanical strength for providing a higher level of reliability while being mounted on the circuit board. Fourth Embodiment A procedure of producing the semiconductor device of a fourth embodiment of the present invention will be described referring to Fig. 6. (1) The procedure starts with producing a semiconductor device 40 in the same manner as that of the third embodiment, as best shown in a plan view of Fig. 6(a) and a side view of Fig. 6(a)'. Its patterns are denoted by 40A. (2) The semiconductor device 40 is securely mounted to a circuit board 41 by bonding means such as solder paste 42 as shown in Fig. 6(b). Another semiconductor device 40 produced in the same manner is mounted on the semiconductor device 40 by bonding means such as solder paste 42. If necessary, one or more identical semiconductor devices may be mounted one over the other to have a tower of the semiconductor devices. The semiconductor devices 40 of the fourth embodiment are joined to each other by soldering the patterns 40A provided on the circuit strip 30 coupled to the semiconductor element 34 as mounted on the circuit board 41. The fourth embodiment allows the semiconductor devices to be increased in number or in the processing capability on a limited space of the circuit board. This will provide the same effect as the stack mounting of conventional dual inline packaged semiconductor devices. The structure of the semiconductor device of this embodiment is thus more advantageous than the CSP structure of conventional semiconductor devices described above. Fifth Embodiment Fig. 7 illustrates a procedure of producing the semiconductor device of a fifth embodiment of the present invention. (1) The procedure starts with preparing a circuit strip 50 made of e.g. a metal which has an insulating layer 51 and an array of patterns 52 formed on one side thereof and a through opening 53 therein, and coupled by adhesive 55 to a semiconductor element 54 as shown in a plan view of Fig. 7(a) and a side view of Fig. 7(a)'. The patterns 52 of the circuit strip 50 are electrically connected by wires 57 to corresponding bonding pads 56 provided on the semiconductor element 54 and exposed across the through opening 53. (2) Like the first embodiment, a limited region about the through opening 53 of the circuit strip 50 is coated with a resin material 58 to seal the wires 57. Then, both side ends of the circuit strip 50 are bent (to L shapes) by pressing or other means, like the third embodiment, so that they wrap the semiconductor element 54 as shown in a plan view of Fig. 7(b) and a side view of Fig. 7(b)'. (3) After electrodes 59 of e.g. solder paste balls are formed on the patterns 52, the semiconductor device is completed as shown in a plan view of Fig. 7(c) and a side view of Fig. 7(c)'. The electrodes (of solder paste balls) 59 of the fifth embodiment are used for mounting the device on an unshown circuit board, hence allowing the semiconductor device to be compatible with reflow conditions required for mounting known ball grid array semiconductor devices which have been widely employed as multi-pin logic devices. The semiconductor device of the fifth embodiment is thus matched to the reflow conditions required for mounting to a circuit board and permits the patterns of its circuit strip to be used for examining the electric characteristics after completion (i.e. the solder paste balls have been joined) hence preventing the solder paste balls from being damaged (e.g. deformed by pressing a probe). Also, the patterns are used for inspecting the bonding condition or conduction of the lower side (the solder paste balls) of the semiconductor device to the circuit board which may hardly be viewed, whereby a higher level of the mounting will be ensured. As a result, the semiconductor devices of surface-mount type according to the first, second, third, and fifth embodiments of the present invention can be mounted on any circuit board (not shown) with much ease. Although the present invention is described in relation to the preferred embodiments of a semiconductor and a method of producing the same, it is not limited to the embodiments. As set forth above, the present invention provides a novel, improved semiconductor device of surface-mount type which is simple in structure and intended for high-density mounting, an appliance on which the semiconductor device is mounted, and a method of producing the semiconductor device.

Claims: A semiconductor device having a semiconductor chip (14, 25, 34 and 54) having a plurality of contact pads (15, 27, 36 and 56) on a main surface of said semiconductor chip, the contact pads (15, 27, 36 and 56) being aligned in a line located along the centre of said semiconductor chip (14, 25, 34 and 54), a plurality of conductive patterns (12, 22,32, 40A and 52), and a plurality of wires (17, 28, 38 and 58) each of which connects one of the contact pads (15, 27, 36 and 56) with an end portion of a respective one of said leads (12, 22, 32, 40A and 52), characterized in that said semiconductor device further comprises a circuit strip including a board (10,20,30 and 50) having a through opening (13, 23, 33 and 53) in a centre region thereof, an insulating layer (11,21,31 and 51) formed on a first surface of the board (10,20, 30 and 50), whereby the contact pads of the semiconductor chip are exposed through the opening, said plurality of conductive patterns (12, 22, 32, 40A and 52) being formed on the insulating layer (11, 21, 31 and 51) and being aligned in two groups located on both sides of the opening in the board (10, 20, 30 and 50), wherein regions of said board adjacent to the through opening (13, 23, 33 and 53) are fixed to the main surface of said semiconductor chip (14, 25, 34 and 54) while all remaing portions of said board are spaced from the main surface of said semiconductor chip (14, 25, 34 and 54), and wherein only the contact pads (15, 27, 36 end 56), said wires (17, 28, 38 and 58) and the end portions of said leads (12, 22, 32, 40A and 52) are sealed with a resin material (18, 29, 38 and 58). A semiconductor device according to claim 1, wherein the circuit strip is bent around to a back surface of said semiconductor chip(14, 25, 34 and 54). A semiconductor device according to claim 2, wherein the circuit strip is spaced from the back surface of said semiconductor chip(14, 25, 34 and 54). A semiconductor device according to claim 2, further comprising a plurality of electrodes (59) each of which is formed on the other end of one of the conductive patterns (52).

Inventors: YAMAGUCHI TADASHI, YAMAGUCHI, TADASHI
Applicants: OKI ELECTRIC IND CO LTD, OKI ELECTRIC INDUSTRY CO., LTD.
Application year: 1997
Main classification: H01L23
IPC codes: H01L23, H01L21