Method of making flip-chip package with underfill

1. A method for the manufacture of a package to encapsulate at least one integrated circuit device, comprising the steps of:

(a) providing a dielectric substrate having a first side and a second side opposite the first side and having a first plurality of bond pads formed on the first side thereof and having at least one aperture;

(b) electrically interconnecting said integrated circuit device to said plurality of bond pads forming a dielectric substrate/integrated circuit device assembly where the at least one aperture is located centrally with respect to the integrated circuit device;

(c) gravitationally aligning said dielectric substrate/integrated circuit assembly such that said integrated circuit device is beneath said dielectric substrate;

(d) introducing a volume of a low viscosity dielectric, having a pre-cure room temperature viscosity of less than 80 pascal seconds (Pa-s), into said at least one aperture by a dispenser vertically in alignment with the at least one aperture, so that the low viscosity dielectric flows from the at least one aperture downward to a central position of the integrated circuit device and outward therefrom;

(e) subsequently increasing the viscosity of the low viscosity dielectric by curing, said curing including

(1) pre-curing at a temperature between 90° C. and 120° C. and

(2) subsequently curing at a second temperature between 145° C. and 165° C. for a period between 60 minutes and 120 minutes,

wherein said volume is effective to coat a surface of said integrated circuit device, the volume being selected to control a lateral extent of coverage of said surface to within about 0.5 millimeter so that a side clearance between a sidewall of the device and a sidewall of the dielectric substrate is between 0.5 millimeter and 1 millimeter, and fill said at least one aperture to a level not higher than the second side of the dielectric substrate, so that more than half of the volume of the at least one aperture is filled, in accordance with flow of said low viscosity dielectric.

2. The method of claim 1 wherein input/output pads on a face of said integrated circuit device are soldered directly to said first plurality of bond pads.

3. The method of claim 2 wherein a spacing between said integrated circuit device and said first side of said dielectric substrate is from 50 microns to 100 microns.

4. The method of claim 3 wherein said pre-cure room temperature viscosity is from 8 Pa-s to 60 Pa-s.

5. The method of claim 1 further including the step of:

(f) encapsulating said integrated circuit device and said first side of said dielectric substrate with a dielectric polymer.

6. The method of claim 5 including selecting said low viscosity dielectric to be capillary flow type material.

7. The method of claim 6 wherein in step (f), said integrated circuit device and said first side of said dielectric substrate are encapsulated with a plastic molding compound.

8. The method of claim 5 wherein said first plurality of bond pads forms an array of bond pads that is separated following said step (f).

9. The method of claim 1 wherein said at least one aperture has a shape and cross sectional area in accordance with the size and shape of said integrated circuit device.

10. The method of claim 9 wherein said integrated circuit device has a square shape, and said at least one aperture is selected to have a circular cross-sectional area.

11. The method of claim 9 wherein said integrated circuit device has a rectangular shape, and said at least one aperture is selected to have a slot-shaped cross-sectional area.

12. The method of claim 9 wherein said integrated circuit device has a rectangular shape in excess of 15 square millimeters, and said at least one aperture is selected to have a cruciform-shaped cross-sectional area.