The present invention relates generally to semiconductor device packaging, and more particularly to a packaged semiconductor device with down-set leads.
There is a continuous drive to make electrical appliances such as computers, televisions, stereos, cell phones, etc. smaller, which drives the need for more highly integrated semiconductor devices in smaller packages. That is, there is a need for semiconductor devices with smaller foot prints. One type of semiconductor package is known as a Quad Flat Pack (QFP).
It would be advantageous to have more I/O's (inputs and outputs) available to accommodate more complex integrated circuits. It would also be advantageous to have more leads in a smaller device foot print.
The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings. In the drawings, like numerals are used for like elements throughout.
In one embodiment, the present invention provides a semiconductor device including a die, a lead frame and a mold compound. The semiconductor die includes an integrated circuit formed therein and a plurality of wire bonding pads that allow for connectivity to the integrated circuit. The lead frame includes a plurality of leads, each of the plurality of leads having a first end and a second end. Respective ones of the wire bonding pads are electrically connected to corresponding ones of the leads at the first ends of the leads. The mold compound encapsulates the die, the leads, and the electrical connections between the leads and the wire bonding pads.
The second ends of the leads extend beyond the mold compound such that they are exposed. The leads comprise a strip of conductive material having a first downward bend proximate to the first end, a second bend proximate to the second end such that the strip after the second bend is substantially parallel with the strip prior to the first bend. A micro-indentation is made between the second bend and the second end. The micro-indentation causes a bottom surface of the lead to be exposed through a bottom surface of the mold compound.
In another embodiment, the present invention provides a lead frame for a Quad Flat Pack (QFP) type semiconductor device, comprising a plurality of leads, each lead having a first end and a second end. The leads extend outwardly from a generally rectangular central space with the first ends being proximate to the central space and the second ends being distal from the central space. Each lead comprises a strip of conductive material having a first downward bend proximate to the first end, a second bend proximate to the second end such that the strip after the second bend is substantially parallel with the strip prior to the first bend, and a micro-indentation between the second bend and the second end. The micro-indentation defines a downwardly projecting dimple.
The present invention also provides a method of assembling a semiconductor device, including the steps of:
providing a lead frame having a plurality of leads, each lead having a first end and a second end, wherein the leads extend outwardly from a generally rectangular central space, the first ends being proximate to the central space and the second ends being distal from the central space, and
wherein each lead comprises a strip of conductive material having a first downward bend proximate to the first end, a second bend proximate to the second end such that the strip after the second bend is substantially parallel with the strip prior to the first bend, and a micro-indentation between the second bend and the second end, the micro-indentation defining a downwardly projecting dimple;
providing a semiconductor die having an integrated circuit therein;
electrically connecting the leads to the integrated circuit; and
encapsulating the semiconductor die, the electrical connections and the leads with a mold compound, wherein the second ends of the leads protrude from the sides of the mold compound and a bottom surface of the leads at the dimple is exposed at a bottom surface of the mold compound.
Referring now to
The semiconductor device 30 also includes a lead frame including a plurality of leads 34 (two of which are shown in
In the embodiment shown, the lead frame includes a flag 42. The semiconductor die 32 may be attached to the flag 42 with epoxy 44, but other methods of attachment could also be used, such as with tape, as is known in the art. The bottom or non-active surface of the die 32 is attached to the flag 42.
A mold compound 46 encapsulates the die 32, the leads 34, and the electrical connections between the leads 34 and the wire bonding pads. The second ends 38 of the leads extend beyond the mold compound 46 such that the second ends 38 of the leads are exposed. In the embodiment shown, the second ends 38 of the leads have been trimmed so that the leads 34 do not protrude from the mold compound 46. Trimming the leads 34 prevents problems encountered by leads that protrude such as those shown in
The lead frame is formed of a conductive material, such as copper foil and may be bare or plated with another material such as Tin, Nickel, Palladium, or Gold. Typically a plurality of lead frames is formed from a sheet of copper foil by cutting, punching, stamping or combinations of these processes. Such lead frame production is well known by those of skill in the art.
The leads 34 comprise a strip of conductive material (e.g., copper as described above) having a first downward bend 48 proximate to the first end 36. In this case, downward means toward the bottom surface of the die 32 or bottom of the semiconductor device 30. The bend need not be 90°, but instead can range from about 90° to about 130°. The leads 34 have a second bend 50 proximate to the second end 38 such that the strip after the second bend 50 is substantially parallel with the strip prior to the first bend 48. The angle to form the second bend 50 depends on the angle of the first bend 48. In one embodiment, a distance from the first bend 48 to the first end 36 is about 1.0 mm, and a distance from the second bend 50 to the second end 38 is about 3.0 mm.
A dimple, indent or micro-indentation 52 is formed between the second bend 50 and the second end 38. The micro-indentation 52 causes a bottom surface of the lead 34 to be exposed and slightly protrude through a bottom surface of the mold compound 46 for electrical contact. Since the leads 34 do not extend well outside of the mold compound 46 as they do in the conventional device package (
Referring now to
The present invention provides advantages over current QFP devices. Since the leads do not extend well beyond the sides of the mold compound, the leads are not prone to bending and the device will have a smaller foot print. For the same reason, the width of the leads may be decreased, thus allowing for more leads per row or a higher density of leads. Further, by altering the location of the indentations to allow for two rows of contact points, current design pitch rules can be followed; the pitch is shown at 68 in
As previously discussed, the present invention also includes a method of assembling a semiconductor device by providing a lead frame having a plurality of leads, each lead having a first end and a second end, wherein the leads extend outwardly from a generally rectangular central space, the first ends being proximate to the central space and the second ends being distal from the central space. Each lead comprises a strip of conductive material having a first downward bend proximate to the first end, a second bend proximate to the second end such that the strip after the second bend is substantially parallel with the strip prior to the first bend, and a micro-indentation between the second bend and the second end, the micro-indentation defining a downwardly projecting dimple.
Next, a semiconductor die having an integrated circuit therein is attached to a flag of the lead frame, if the lead frame has a flag. If the lead frame does not have a flag, the die is typically attached to a tape to which the leads of the lead frame also are attached. The leads are then electrically connected to wire bonding pads of the die via wire bonding and the semiconductor die, the electrical connections and the leads are encapsulated with a mold compound. However, the second ends of the leads protrude from the sides of the mold compound, and a bottom surface of the leads protrudes from a bottom surface of the mold compound at the dimple. The second ends of the leads that protrudes from the mold compound can be trimmed or grinded off.
Referring now to
While embodiments of the invention have been described and illustrated, it will be understood by those skilled in the technology concerned that many variations or modifications in details of design or construction may be made without departing from the present invention.
Number | Date | Country | Kind |
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PI20093809 | Sep 2009 | MY | national |