Thermally enhanced electronic flip-chip packaging with external-connector-side die and method
View Patent ↗A method and apparatus for making a package having improved heat conduction characteristics and high frequency response. A relatively thick package substrate, such as copper, has a wiring layer bonded to one face, leaving the opposite face exposed, for example, to be a surface for connection to a heat sink. One ore more chips are bonded to the wiring layer, and an array of connectors, such as solder balls are provided around the periphery of the chip(s) for connection to a printed circuit board. In some embodiments, the printed circuit board has a hole that the chip(s) extend into to allow smaller external-connection solder balls. In some embodiments, a second heat sink is connected to the back of the chip through the PCB hole.
1. An apparatus comprising:
a core comprising a layer of an alloy that includes nickel and iron, the core having a first major face and a second major face, wherein the second major face of the core is exposed;
a wiring layer having an electrically insulating layer coupled to the first major face, and a plurality of electrically conductive traces separated from the core by the insulating layer, wherein the core is substantially thicker than the wiring layer;
a first electronics chip attached to at least some of the plurality of traces by ball-grid-array solder balls; and
a plurality of external electrical connectors attached to the traces; and
wherein the core has an effective coefficient of thermal expansion (CTE) that matches a CTE of the chip better than substantially pure copper does in a region adjacent to the first chip.
2. The apparatus of claim 1 , wherein the layer of iron-nickel alloy has a layer that includes copper attached on the second face.
3. The apparatus of claim 2 , wherein the layer of iron-nickel alloy also has a layer that includes copper attached on the first face.
4. The apparatus of claim 1 , wherein the layer of iron-nickel alloy has a lateral extent substantially smaller than a lateral extent of the core.
5. The apparatus of claim 1 , wherein the core is electrically connected to the first chip.
6. The apparatus of claim 1 , wherein the core is electrically connected to a power connection of the first chip.
7. The apparatus of claim 1 , further comprising:
a printed circuit board (PCB) having a plurality of conductive traces, wherein the plurality of external electrical connectors on the first face are electrically connected to the plurality of conductive traces of the PCB; and a first heat sink in thermal contact with the exposed second face of the core.
8. The apparatus of claim 7 , wherein the PCB has an opening opposite the first chip, the opening being at least the size of the first chip.
9. The apparatus of claim 8 , further comprising a second heat sink in thermal contact with the first chip through the opening.
10. The apparatus of claim 1 , further comprising a second electronics chip attached to at least some of the plurality of traces by ball-grid-array solder balls.
11. The apparatus of claim 1 , wherein the core is about 800 microns thick and the wiring layer is about 40 microns thick.
12. The apparatus of claim 1 , wherein the external conductors include a plurality of solder balls, and wherein a thickness of the chip is thinned after formation of electronic circuitry thereon such that the thickness of the chip is smaller than a diameter of the external-conductor solder balls.