The present invention relates generally to semiconductor die packages and, more particularly, to a semiconductor die package having insulated outer leads or support fingers.
Semiconductor die packaging provides for suitable external electrical connections and protection of a semiconductor die against mechanical and environmental stresses. Continued progress in reduction of the size of the semiconductor dies and increased functionality and complexity of the circuits formed in the dies require size reduction of the packaging.
One typical type of semiconductor die package is a Quad Flat Package (QFP), which is formed with a semiconductor die mounted to a lead frame. The lead frame is formed from a sheet of metal that has a die attach pad often called a flag and struts that attach the flag to a frame. The lead frame has lead fingers that surround the flag. Electrodes of the die are electrically connected to the proximal ends of the lead fingers with bond wires to provide a means of easily electrically connecting the die to circuit boards and the like. After the electrodes and pads are connected, the semiconductor die and the bond wires are encapsulated in a mold compound leaving only sections of the lead fingers exposed. These exposed or external leads are cut from the frame of the lead frame (singulated) and bent for ease of connection to a circuit board.
The inherent structure and size of QFP packages results in limiting the number of external leads, and therefore the number of package external electrical connections, that can be used for a specific QFP package size. However, the lead width and lead pitch can be reduced to allow for an increased number of leads. Such a reduction in pitch may cause inter lead shorting and the reduced lead width may result in deformation or bending of the relatively thin leads. Accordingly, it would be advantageous to reduce the lead pitch and at the same time, reduce the risk of inter lead shorting.
The invention, together with objects and advantages thereof, may best be understood by reference to the following description of preferred embodiments together with the accompanying drawings in which:
The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention, and is not intended to represent the only forms in which the present invention may be practised. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the invention. In the drawings, like numerals are used to indicate like elements throughout. Furthermore, terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that module, circuit, device components, structures and method steps that comprises a list of elements or steps does not include only those elements but may include other elements or steps not expressly listed or inherent to such module, circuit, device components or steps. An element or step proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements or steps that comprises the element or step.
In one embodiment, the present invention provides a semiconductor die package comprising a die flag and lead fingers surrounding the die flag. Each of the lead fingers has a bonding end adjacent the die flag and an elongate region extending away from the die flag. A semiconductor die is mounted on the die flag and bond wires electrically connect electrodes of the die to the bonding end of each of the lead fingers. A mold compound forms a housing that covers the die, bond wires, bonding ends of the lead fingers, and the die flag. The elongate region of each of the lead fingers protrudes from the housing to provide external connector leads for the package. The mold compound extends from the housing to provide insulated support fingers molded to the external connector leads.
In another embodiment, the present invention provides a method of assembling a semiconductor die package. The method comprises providing a lead frame having a surrounding frame that surrounds a die flag. The lead frame has tie bars extending inwardly from the surrounding frame and supporting the die flag, and there are lead fingers surrounding the die flag, each lead finger having a bonding end adjacent the die flag and an elongate region extending away from the die flag towards the outer fame. Outer dam bars bridge adjacent free ends of the elongate regions and inner dam bars support the lead fingers from the outer surrounding frame. The inner dam bars define an external periphery package housing outline for a periphery other than regions between adjacent elongate regions. The method also comprises mounting a semiconductor die on the die flag and electrically connecting electrodes of the semiconductor die to the bonding end of each of the lead fingers with bond wires. There is also performed forming each elongate region into external connector leads with mounting feet at free ends thereof. The elongate region of each of the lead fingers protrudes from the housing to provide the external connector leads for the package. During the molding process some of the mold compound flows from the molding chamber between adjacent external connector leads to provide insulated support fingers molded to the external connector leads.
In a further embodiment, the present invention provides a lead frame sheet with an array of lead frames formed therein. Each of the lead frames includes a surrounding frame that surrounds a die flag, and tie bars extending inwardly from the surrounding frame and supporting the die flag. Each of the lead frames also includes lead fingers surrounding the die flag, each lead finger having a bonding end adjacent the die flag and an elongate region extending away from the die flag towards the outer fame. Outer dam bars bridge adjacent free ends of the elongate regions and inner dam bars supporting the lead fingers from the outer surrounding frame. The inner dam bars define a external periphery package housing outline for a periphery other than regions between adjacent elongate regions
Referring now to
Each one of the lead frames 102 also includes lead fingers 108 that surround the die flag 106, each having a bonding end 110 adjacent the die flag 106 and an elongate region 112 extending away from the die flag 106 towards the outer surrounding frame 104. Respective outer dam bars 114 bridge adjacent free ends of the elongate regions 112 and in combination with inner dam bars 116 support the lead fingers 108 from the outer surrounding frame 104. In this embodiment, the inner dam bars 116 do not bridge across the lead fingers 108 and there are also dummy leads 118 that provide additional support as will be apparent to a person skilled in the art.
In this embodiment there are tie bars 120 that extend inwardly from the surrounding frame 104 and support the die flag 106. The tie bars 120 each have an angled section 122 that is angled to form a down-set relationship between the die flag 106 and surrounding frame 104.
In operation a mold compound is deposited into the housing mold cavity 506 to cover the semiconductor die 202, the bond wires 302, each bonding end 110 of the lead fingers 108 and the die flag 106. Furthermore, during molding some the mold compound flows into the housing mold cavity 506 through the housing molding outlets 306 and into the external molding cavities 516.
Referring to
The semiconductor die package 600 includes the mold compound that forms a housing 602 that covers the semiconductor die 202, the bond wires 302, each bonding end 110 of the lead fingers 108 and the die flag 106. In addition, the elongate region 112 of each of the lead fingers 108 protrudes from the housing 602 to provide external connector leads 604 for the package 600. The mold compound that flowed into the external molding cavities 516 extends from the housing 602 to provide insulated support fingers 606 molded to the external connector leads 604.
The co-acting lead finger forming (reshaping) surfaces 512, 514 have bent free ends of the external connector leads 604 to form mounting feet 608. Furthermore, in this embodiment as illustrated the insulated support fingers 606 are coplanar with respective adjacent regions of the external connector leads 604.
In this embodiment, the insulated support fingers 606 extend along a total length of the external connector leads 604. However, in some embodiments the insulated support fingers 606 need not extend total length of the external connector leads 604 and for instance my terminate before the mounting feet 608.
The semiconductor die package 900 includes the mold compound that forms a housing 902 that covers the semiconductor die 202, the bond wires 302, each bonding end 110 of the lead fingers 108 and the die flag 106. In addition, the elongate region 112 of each of the lead fingers 108 protrudes from the housing 902 to provide external connector leads 904 for the package 900. The mold compound that flowed into the external molding cavities 516 extends from the housing 602 to provide insulated support fingers 906 molded to the external connector leads 904. Also, the mold compound that flowed into the bridging cavities 802 forms a respective insulated cross member 908 associated with and molded to a group of the external connector leads 604. Furthermore, each respective cross member 908 is normal to longitudinal axes of the group of external connector leads 604 and each cross member 908 is integral with a group of the insulated support fingers 906.
In this embodiment, the insulated support fingers 906 extend along a total length of the external connector leads 904. However, in some embodiments the insulated support fingers 906 need not extend total length of the external connector leads 904 and for instance my terminate before reaching mounting feet 918 of the external connector leads 904.
Referring to
In operation, after bending and the elongate regions 112 of the lead fingers 108, a mold compound is deposited into the housing mold cavity 506 to cover the semiconductor die 202, the bond wires 302, each bonding end 110 of the lead fingers 108 and the die flag 106. During molding some the mold compound flows into the housing mold cavity 506 through the housing molding outlets 306 and into both the external molding cavities 516 and bridging cavities 1102.
Referring to
The semiconductor die package 1200 includes the mold compound that forms a housing 1202 that covers the semiconductor die 202, the bond wires 302, each bonding end 110 of the lead fingers 108 and the die flag 106. In addition, the elongate region 112 of each of the lead fingers 108 protrudes from the housing 1202 to provide external connector leads 1204 for the package 1200. The mold compound that flowed into the external molding cavities 516 extends from the housing 602 to provide insulated support fingers 1206 molded to the external connector leads 904. The insulated support fingers 1206 are thicker than the external connector leads 1204 and cover regions of both a top and opposite lower surface of the external connector leads 1204.
Also, the mold compound that flowed into the bridging cavities 1102 forms a respective insulated cross member 1208 associated with and molded to a group of the external connector leads 604. Furthermore, each respective cross member 1208 is normal to longitudinal axes of the group of external connector leads 604 and each cross member 1208 is integral with a group of the insulated support fingers 1206.
In this embodiment, the insulated support fingers 1206 extend along a total length of the external connector leads 1204. However, in some embodiments the insulated support fingers 1206 need not extend total length of the external connector leads 1204 and for instance my terminate before reaching mounting feet 1218 of the external connector leads 1204.
Referring to
Referring to
The method 1600 at a block 1650 includes performing a molding process to form a housing from a mold compound deposit. The molding process injects or presses a mold compound into the housing mold cavity 506 so that the mold compound covers the semiconductor die 202, the bond wires 302, each bonding end 110 and the die flag 106. During the molding process the inner dam bars 116 form a partial external periphery of molding chamber for the housing (e.g., housing 602, 902, 1202). In addition, the elongate region of each of the lead fingers 108 protrudes from the housing to provide the external connector leads for the package, and during the molding process some of the mold compound flows from the molding chamber 506 between adjacent external connector leads to provide insulated support fingers molded to the external connector leads. Furthermore, during the molding process the flow of the mold compound between adjacent external connector leads is retained by the outer dam bars 114. Finally the method 1600 is complete after a block 1660 performs a cutting (singulating) process to sever the outer and inner dam bars 114, 116 and tie bars 120 which results in a completed package such as semiconductor die package 600, 900 or 1200.
Advantageously, the present invention provides for strengthening the external leads of a semiconductor die package by use of the insulated support fingers, which can be further strengthened by the insulated cross members. As a result, the present invention at least alleviates inter lead shorting caused by a reduction in external lead pitch and the reduced lead width. The insulated support fingers and insulated cross members may also alleviate deformation or undesirable bending of the external leads. In addition, because the base of the mounting feet has a width narrower than the width of corresponding opposite upper surface, this feature can also reduce the possibility of solder shorts when the semiconductor package is mounted onto a circuit board.
The description of the preferred embodiments of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the invention to the forms disclosed. It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but covers modifications within the spirit and scope of the present invention as defined by the appended claims.
Number | Date | Country | Kind |
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201410145465.6 | Apr 2014 | CN | national |