Systems and Methods of Improved Heat Dissipation with Variable Pitch Grid Array Packaging
Adequate heat dissipation is essential for semiconductor devices. When a device exceeds a specified junction temperature, the device can be damaged, not perform correctly, or can have a reduced operating life. Semiconductor packages must dissipate heat from the chip to the external environment (i.e. to the PCB, air, etc) to keep the semiconductor device below a certain temperature threshold. For most devices, the most efficient way to dissipate the heat is through the package external I/O connections and into the PCB that it is mounted to. For Ball Grid Array (BGA) packages, the external I/Os are solder balls. Variable pitch packages pose advantages in heat dissipation without introducing significant costs.
1 . A semiconductor package comprising:
a semiconductor die;
a substrate having a top surface and a bottom surface, said substrate comprising vias comprising a conductor;
metal traces on the top surface of the substrate;
metal traces on the bottom surface including interface pads
wherein metal traces on the bottom surface couple the interface pads to the vias; and
wherein the bottom surface comprises a first region and a second region and the interface pads in the first region are spaced at a first pitch and the interface pads in the second region are spaced at a second pitch.
2 . The semiconductor package of claim 1 further comprising:
a solder mask having an opening under each interface pad; wherein the openings in the solder mask are spaced at the first pitch in the first region and the solder mask are spaced at the second pitch in the second region.
3 . The semiconductor package of claim 1 further comprising a solder ball coupled to each interface pad.
4 . The semiconductor package of claim 1 wherein the package is a flip-chip BGA.
5 . The semiconductor package of claim 1 wherein the package is a cavity down BGA.
6 . The semiconductor package of claim 1 wherein the package is a PGA or CGA.
7 . The semiconductor package of claim 1 wherein the package is a LGA.
8 . The semiconductor package of claim 1 wherein the metal traces on the top substrate comprise bond fingers and wire bonds couple the die to the bond fingers.
9 . The semiconductor package of claim 1 wherein the metal traces on the top substrate comprise via pads and the die is flip-chipped to the via pads.
10 . The semiconductor package of claim 1 wherein the vias comprise electrical vias and thermal vias and the interface pads in the first region are coupled to electrical vias and interface pads in the second region are coupled to thermal vias.
11 . The semiconductor package of claim 10 wherein the electrical vias have walls that are coated with a conductor and the thermal vias are filled with a conductor.
12 . A method of packaging a semiconductor die comprising:
creating vias in a substrate having a top surface and a bottom surface and having a first region and a second region;
adding conductor to the vias;
forming metal traces on the top surface;
forming metal traces on the bottom surface, wherein the metal traces comprises interface pads spaced at a first pitch in the first region and interface pads spaced at a second pitch in the second region;
attaching the semiconductor die to the top surface;
electrically connecting the semiconductor die to the metal traces on the top surface; and
encapsulating the package in a mold compound.
13 . The method of claim 12 , wherein the metal traces on the top surface comprises bond fingers and the electrically connecting comprises attaching wire bonds between the die and the bond fingers.
14 . The method of claim 12 , wherein the metal traces on the top surface comprises via pads and the electrically connecting comprises flip-chipping the die onto the via pads.
15 . The method of claim 12 , further comprises forming a solder mask to cover the metal traces on the bottom surface, wherein the solder mask has openings underneath each interface pad.
16 . The method of claim 12 , further comprises affixing a pin beneath each interface pad.
17 . The method of claim 12 , further comprising attaching a solder ball to each interface pad.
The method of claim 12 , wherein the vias have walls and wherein adding conductor to the vias comprises coating the walls of the vias with a conductor.
18 . The method of claim 12 , wherein adding conductor to the vias comprises filling the vias with a conductor.
19 . A semiconductor package comprising:
a semiconductor die;
a substrate having a top surface and a bottom surface, said substrate comprising vias;
means for electrically connecting the die to the vias;
interface pads on the bottom surface;
means for connecting the interface pads to the vias wherein the bottom surface comprises a first region and a second region and the interface pads in the first region are spaced at a first pitch and the interface pads in the second region are spaced at a second pitch.
20 . The semiconductor package of claim 19 further comprising:
a masking means for covering the bottom surface comprising openings beneath each interface pad.