SEMICONDUCTOR DEVICE PACKAGE WITH INTEGRATED STAND-OFF
A semiconductor device includes a substrate having first and second major surfaces and conductive traces, and solder balls attached to the second major surface of the substrate. A semiconductor die including an integrated circuit (IC) is attached to one of the major surfaces of the substrate. The IC is electrically connected to the solder balls by the conductive traces. The substrate includes an integrally molded stand-off feature that prevents the solder balls near the corners and the sides of the substrate from being knocked off during handling. The stand-off feature also maintains a predetermined distance between the substrate and a printed circuit board (PCB) when the substrate is attached to the PCB, and then a reflow process is performed. The stand-off feature also prevents open connections between the solder balls and the PCB that may be caused by warping of the PCB or the weight of the semiconductor die. The semiconductor device may include a stiffener ring attached to the second major surface of the substrate and surrounding the conductive balls.
1 . A semiconductor device, comprising:
a substrate having a first major surface and a second major surface, wherein the substrate has a plurality of conductive traces located therein;
a semiconductor die attached to one of the major surfaces of the substrate, wherein the semiconductor die includes an integrated circuit formed therein; and
a plurality of conductive balls attached to the second major surface of the substrate, wherein the conductive traces of the substrate electrically connect the integrated circuit with the conductive balls, and
wherein the substrate includes an integral stand-off that projects perpendicularly downward from the second major surface of the substrate and wherein the stand-off has a length that is less than a diameter of the conductive balls.
2 . The semiconductor device of claim 1 , wherein the stand-off is formed by molding of the substrate.
3 . The semiconductor device of claim 2 , wherein the substrate is generally rectangular and the stand-off is formed at least at the four corners of the substrate.
4 . The semiconductor device of claim 2 , wherein the substrate is generally rectangular and the stand-off is formed along at least two sides of the substrate.
5 . The semiconductor device of claim 4 , wherein the stand-off is formed along four sides of the substrate.
6 . The semiconductor device of claim 4 , wherein the second major surface of the substrate is attached to a printed circuit board by way of the conductive balls and wherein after a reflow process, the stand-off prevents open connections between the conductive balls and the printed circuit board.
7 . The semiconductor device of claim 6 , wherein the stand-off maintains a predetermined distance between the second major surface of the substrate and the printed circuit board.
8 . The semiconductor device of claim 2 , wherein the die is attached to the first major surface of the substrate.
9 . The semiconductor device of claim 2 , wherein the die is attached to a central area of the second major surface of the substrate and is surrounded by the conductive balls, and wherein the die is encapsulated with a protective material.
10 . The semiconductor die of claim 2 , further comprising a ring formed of a generally stiff material, wherein the ring is attached to the second major surface of the substrate and is disposed between the conductive balls and the stand-off.
11 . The semiconductor device of claim 10 , wherein the ring comprises copper.
12 . The semiconductor device of claim 10 , wherein the ring is tacked to the substrate.
13 . The semiconductor device of claim 10 , wherein the ring is plated to the substrate.
14 . The semiconductor device of claim 2 , wherein the substrate comprises green materials.
15 . The semiconductor device of claim 2 , wherein the stand-off has a length of between 0.35 mm and 0.50 mm and the conductive balls have a diameter of between 0.40 mm and 0.55 mm.
16 . The semiconductor device of claim 1 , wherein the stand-off prevents conductive balls near to a periphery of the substrate from being dislodged.
17 . A method of assembling a semiconductor device, comprising:
fabricating a substrate including a plurality of conductive traces, wherein the substrate has a first major surface and a second major surface;
molding the substrate to form a stand-off that projects perpendicularly downward from the second major surface of the substrate;
attaching a semiconductor die including an integrated circuit to one of the major surfaces of the substrate; and
attaching a plurality of conductive balls to the second major surface of the substrate, wherein the integrated circuit is electrically connected to the conductive balls by the conductive traces.
18 . The method of assembling a semiconductor device of claim 17 , further comprising attaching a ring formed of a stiff material to the second major surface of the substrate, wherein the ring surrounds the plurality of conductive balls.
19 . The method of assembling a semiconductor device of claim 17 , further comprising attaching the die to the second major surface of the substrate and encapsulating the die with a protective material.
20 . The method of assembling a semiconductor device of claim 19 , further comprising:
attaching the second major surface of the substrate to a printed circuit board by way of the conductive balls; and
performing a reflow process to facilitate electrical connection of the conductive balls to the printed circuit board, wherein the stand-off prevents open connections between the conductive balls and the printed circuit board.