Patent Publication Number: US-2015069592-A1

Title: Semiconductor device, method of manufacturing same, and application board mounted with same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2013-185616, filed on Sep. 6, 2013, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to a semiconductor device, a method of manufacturing the same, and an application board mounted with the same. 
     BACKGROUND 
     In a semiconductor device, a semiconductor chip is sealed up with a molding resin. If the semiconductor device is stored for a long period in a state that the semiconductor device is exposed to air, the molding resin absorbs moisture in the air. Consequently, semiconductor elements on the semiconductor chip may deteriorate due to this moisture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are drawings of a semiconductor device of a first embodiment; 
         FIG. 2  is a flowchart showing a method of manufacturing the semiconductor device of the first embodiment; 
         FIGS. 3A and 3B  are drawings of an application board mounted with the semiconductor device of the first embodiment; and 
         FIGS. 4A and 4B  are drawings of a semiconductor device of a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will now be explained with reference to the accompanying drawings. The present invention is not limited to these embodiments. Common components are denoted by common reference numerals throughout the drawings, and duplicate descriptions of these components are omitted. The drawings are schematic views used to facilitate the description and understanding of the invention, and may therefore differ from actual devices in shape, dimension, ratio and the like in some places. Design changes can be made to these devices as appropriate by taking into consideration the following description and known technology. In the following embodiments, a vertical direction of a semiconductor chip indicates a relative direction when a surface of the semiconductor chip where semiconductor elements are arranged is faced up, and may therefore differ from a vertical direction based on the gravitational acceleration in some cases. 
     In one embodiment, a semiconductor device includes a lead frame including an island portion and a terminal portion separated from the island portion. The device further includes a semiconductor chip mounted on the island portion and including an electrode. The device further includes an insulating layer disposed on the semiconductor chip and having an opening to expose at least a part of the electrode. The device further includes a connector covering the electrode exposed through the opening and electrically connecting the electrode and the terminal portion. 
     First Embodiment 
       FIGS. 1A and 1B  are drawings of a semiconductor device  10  of a first embodiment. 
       FIG. 1A  illustrates a top view of the semiconductor device  10 , and  FIG. 1B  illustrates a side view of the semiconductor device  10  on a first sheet-like connector  13  side. 
     The semiconductor device  10  includes a lead frame  11 , a semiconductor chip  12 , an insulating layer  15 , a first sheet-like connector  13 , and a second sheet-like connector  14 . 
     The lead frame  11  includes an island portion  28 , and first and second terminal portions  281  and  282  separated from the island portion  28 . The lead frame  11  is made of an electrical conductor and formed of, for example, low-resistance metal. The island portion  28  is a mounting portion on which the semiconductor chip  12  is mounted. The first and second terminal portions  281  and  282  are electrically connected to first and second electrodes  121  and  122  of the semiconductor chip  12 . 
     The semiconductor chip  12  is mounted on the island portion  28 , and includes the first and second electrodes  121  and  122 . The type of the semiconductor chip  12  is optional, and therefore not limited in particular. The insulating layer  15  is formed on the semiconductor chip  12  and includes openings  16 . The insulating layer  15  is formed of, for example, polyimide. In the first embodiment, the openings  16  have shapes and sizes corresponding to shapes and sizes of the first and second electrodes  121  and  122  to expose the first and second electrodes  121  and  122  in whole. 
     The first sheet-like connector  13  is a bent, belt-like metal sheet. Similarly to the openings  16 , the first sheet-like connector  13  has a shape and a size corresponding to the shape and the size of the first electrode  121 . Accordingly, one end of the first sheet-like connector  13  covers almost the entire area of the first electrode  121  exposed through the opening  16 . The other end of the first sheet-like connector  13  is in contact with the first terminal portion  281  of the lead frame  11 . In this manner, the first sheet-like connector  13  electrically connects the first electrode  121  and the first terminal portion  281 . In addition, similarly to the openings  16 , the first sheet-like connector  13  has the shape and the size corresponding to the shape and the size of the first electrode  121 . The connector  13  can therefore cover the first electrode  121  in whole. Consequently, it is possible to widen the area of contact between the first sheet-like connector  13  and the first electrode  121 . It is therefore possible to lower the contact resistance between the first sheet-like connector  13  and the first electrode  121 . 
     Similarly to the first sheet-like connector  13 , the second sheet-like connector  14  is also a bent, belt-like metal sheet. Similarly to the openings  16 , the second sheet-like connector  14  has a shape and a size corresponding to the shape and the size of the second electrode  122 . Accordingly, one end of the second sheet-like connector  14  covers almost the entire area of the second electrode  122  exposed through the opening  16 . The other end of the second sheet-like connector  14  is in contact with the second terminal portion  282  of the lead frame  11 . In this manner, the second sheet-like connector  14  electrically connects the second electrode  122  and the second terminal portion  282 . In addition, similarly to the openings  16 , the second sheet-like connector  14  has the shape and the size corresponding to the shape and the size of the second electrode  122 . The connector  14  can therefore cover the second electrode  122  in whole. Consequently, it is possible to widen the area of contact between the second sheet-like connector  14  and the second electrode  122 . It is therefore possible to lower the contact resistance between the second sheet-like connector  14  and the second electrode  122 . 
     Here, the semiconductor chip  12 , the first and second sheet-like connectors  13  and  14  and the like of the semiconductor device  10  are not sealed up with a molding resin. In a case where an electrical connection is made between an electrode of the semiconductor chip and a terminal portion of the lead frame with a wire having a thread-like structure, the wire having the thread-like structure becomes easily deformed if a force is applied from outside the semiconductor device. The deformation of the wire may lead to disconnection or short-circuiting with other wires. Accordingly, in the semiconductor device, the wire needs to be immobilized with a molding resin to avoid causing the wire to become deformed. The molding resin also has a function of protecting the semiconductor chip against contamination by covering the surfaces of the semiconductor chip. 
     However, since the molding resin has hygroscopicity as described above, the molding resion absorbs moisture in the air. Accordingly, semiconductor elements on the semiconductor chip may deteriorate due to the moisture. 
     Therefore, the semiconductor device  10  of the first embodiment includes the first and second sheet-like connectors  13  and  14  in place of wires. The first and second sheet-like connectors  13  and  14  are metal sheets having a sheet-like structure and higher in mechanical strength than wires having a thread-like structure. Accordingly, the first and second sheet-like connectors  13  and  14  are unlikely to be deformed by an external force. The first and second sheet-like connectors  13  and  14  therefore need not be immobilized with a molding resin. 
     In the semiconductor device  10 , the first and second electrodes  121  and  122  are covered with the first and second sheet-like connectors  13  and  14 , and surfaces of the semiconductor chip  12  other than those of the first and second electrodes  121  and  122  are covered with the insulating layer  15 . Consequently, the surfaces of the semiconductor chip  12  including the first and second electrodes  121  and  122  are protected by the insulating layer  15  and the first and second sheet-like connectors  13  and  14 . Accordingly, there is no need in the semiconductor device  10  to provide a molding resin for protecting the surfaces of the semiconductor chip  12 . 
     For the above-described reason, the semiconductor device  10  of the first embodiment need not be sealed up with a molding resin. Since the semiconductor device  10  therefore does not include any molding resin having hygroscopicity, it is possible to prevent the deterioration of semiconductor elements due to moisture. 
     In addition, the first and second sheet-like connectors  13  and  14  are wider in cross-sectional area than wires, and therefore superior in electrical conductivity. Accordingly, the first and second electrodes  121  and  122  and the first and second terminal portions  281  and  282  can be electrically connected with low resistance by using the first and second sheet-like connectors  13  and  14 . 
     (1) Method of Manufacturing Semiconductor Device 
       FIG. 2  is a flowchart showing a method of manufacturing the semiconductor device  10  of the first embodiment. 
     In step S 1 , a metal sheet is pressed, etched and cut to form the first and second sheet-like connectors  13  and  14 . At this time, the first and second sheet-like connectors  13  and  14  are formed so as to correspond in shape and size to the first and second electrodes  121  and  122 . Consequently, when the first and second sheet-like connectors  13  and  14  are connected respectively onto the first and second electrodes  121  and  122  of the semiconductor chip  12 , the first and second sheet-like connectors  13  and  14  can cover the entire areas of the first and second electrodes  121  and  122 . 
     In step S 2 , the insulating layer  15  is formed on the semiconductor chip  12 . In addition, the openings  16  to expose the entire areas of the first and second electrodes  121  and  122  on the semiconductor chip  12  are formed in the insulating layer  15 . 
     In step S 3 , the semiconductor chip  12  is mounted on the island portion  28  of the lead frame  11  by using a conductive adhesive agent. 
     In step S 4 , the first sheet-like connector  13  is fixed onto the first electrode  121  exposed through an opening  16  and onto the first terminal portion  281  by using a conductive adhesive agent. Likewise, the second sheet-like connector  14  is fixed onto the second electrode  122  exposed through an opening  16  and onto the second terminal portion  282 . 
     In step S 5 , a plurality of semiconductor devices  10  coupled by the lead frame  11  is uncoupled (divided into individual pieces). 
     Consequently, each semiconductor device  10  is completed. According to this manufacturing method, since the semiconductor device is not sealed up with a molding resin, it is possible to reduce manufacturing process steps and manufacturing costs. 
     (2) Application Board 
       FIGS. 3A and 3B  are drawings of an application board mounted with the semiconductor device  10  of the first embodiment. 
       FIGS. 3A and 3B  respectively illustrate examples of an application board  40  including the semiconductor device  10  of the first embodiment. 
     As illustrated in  FIG. 3A , the application board  40  includes a substrate  41 , the semiconductor device  10 , and a plurality of electronic components  42 . The substrate  41  may be, for example, a printed circuit board. The electronic components  42  are electrically connected to the semiconductor device  10  via wiring patterns on the printed circuit board  41 . In addition, the printed circuit board  41 , the semiconductor device  10 , and the plurality of electronic components  42  may be integrally sealed up with a molding resin  47  to obtain such an application board  50  as illustrated in  FIG. 3B . 
     According to the first embodiment, since the semiconductor device  10  uses the first and second sheet-like connectors  13  and  14  which are high in mechanical strength, the semiconductor device  10  can avoid suffering short-circuit and disconnection faults without having to be sealed up with a molding resin. In addition, according to the first embodiment, the first and second electrodes  121  and  122  are covered with the first and second sheet-like connectors  13  and  14 , and the surfaces of the semiconductor chip  12  other than those of the first and second sheet-like connectors  13  and  14  are covered with the insulating layer  15 . Accordingly, it is possible to protect the surfaces of the semiconductor chip  12  including the first and second electrodes  121  and  122  without having to seal up the surfaces with a molding resin. 
     For the above-described reason, according to the first embodiment, there is no need to seal up the semiconductor device  10  with a molding resin. Since the semiconductor device  10  therefore does not include any molding resin having hygroscopicity, it is possible to prevent the deterioration of semiconductor elements due to moisture. 
     According to the first embodiment, since the semiconductor device is not sealed up with a molding resin, it is possible to reduce manufacturing process steps and manufacturing costs. 
     According to the first embodiment, the first and second electrodes  121  and  122  and the first and second terminal portions  281  and  282  can be electrically connected with low resistance by using the first and second sheet-like connectors  13  and  14  superior in electrical conductivity to wires 
     Second Embodiment 
       FIGS. 4A and 4B  are drawings of a semiconductor device  20  of a second embodiment. 
       FIG. 4A  illustrates a top view of the semiconductor device  20  of the second embodiment, and  FIG. 4B  illustrates a side view of the semiconductor device  20  of the second embodiment on a first sheet-like connector  23  side. 
     The second embodiment differs from the first embodiment in the shape of the first sheet-like connector  23 . The rest of the configuration of the second embodiment may be the same as the corresponding configuration of the first embodiment. The connecting portion of the first sheet-like connector  23  connected to the first electrode  121  is formed so as to correspond in shape and size to an opening  16  of the insulating layer  15  rather than to the first electrode  121 . Accordingly, the first sheet-like connector  23  covers the first electrode  121  not in whole but in part in a case where the first electrode  121  is partially exposed through the opening  16 . That is, the first electrode  121  is covered in whole with both the first sheet-like connector  23  and the insulating layer  15 . In  FIG. 4A , the area of the first electrode  121  covered with the insulating layer  15  is shown by a dashed line. 
     Conversely, the opening  16  of the insulating layer  15  is formed so as to correspond in shape and size to the first sheet-like connector  23  rather than to the first electrode  121 . 
     The first electrode  121  may vary in shape and size for each product. Accordingly, in order to make the first sheet-like connector  13  correspond in shape and size to the first electrode  121  of each product to cover the entire area of the first electrode  121 , the first sheet-like connector  13  needs to be manufactured as a dedicated connector on a product-by-product basis. 
     In contrast, according to the second embodiment, the first electrode  121  is covered in whole with both the first sheet-like connector  23  and the insulating layer  15 . That is, the first sheet-like connector  23  covers a part of the first electrode  121 , and the insulating layer  15  covers the rest of the first electrode  121 . Accordingly, the first sheet-like connector  23  need not be made to correspond in shape and size to the first electrode  121 , while the first sheet-like connector  23  need be made to correspond in shape and size to the opening  16 . It is therefore possible to apply the same shape and size of the first sheet-like connector  23  to different products. Consequently, the first sheet-like connector  23  can be mass-produced not as a dedicated connector but as a general-purpose connector usable for a wide range of products. This enables a reduction in the manufacturing costs of the connector. Similarly to the first sheet-like connector, the second sheet-like connector  14  can also be manufactured as a general-purpose connector for partially covering the second electrode  122 . 
     According to the second embodiment, there is no need for sealing with a molding resin as similar to the first embodiment. Consequently, it is possible to obtain the same effects as those of the first embodiment. In the second embodiment, the entire surfaces of the semiconductor chip  12  including the first and second electrodes  121  and  122  are covered with the insulating layer  15  and the first and second sheet-like connectors  23  and  14 . Accordingly, the surfaces of the semiconductor chip  12  including the first and second electrodes  121  and  122  can be protected without having to seal up the semiconductor chip with a molding resin. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel devices, methods and boards described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the devices, methods and boards described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.