Process for assembling an integrated circuit package having a substrate vent hole

Abstract

The present invention involves a method of providing an integrated circuit package having a substrate with a vent opening. The integrated circuit package includes a substrate having an opening and an integrated circuit mounted to the substrate. An underfill material is dispensed between the substrate and the integrated circuit.

Description

mm micrometers in diameter, although in alternate embodiments, the size of the substrate vent opening 15 may be determined according to need and other design specifications.

The package 10 may include an underfill material 24 that is located between the integrated circuit 18 and the substrate 12. The underfill material 24 may form a circumferential fillet that surrounds and seals the edges of the IC 18. The uniform sealing function of the underfill material 24 may inhibit moisture migration, and cracking of the IC 18. The seal process may also reduce delamination. The underfill material 24 also reduces stresses on the solder bumps 20. In one embodiment, the underfill material 24 is an epoxy. The integrated circuit 18 may be encapsulated by an encapsulant (not shown). The encapsulant may be an injection molded material. Additionally, the package 10 may incorporate a thermal element (not shown) such as a heat slug or a heat sink to remove heat generated by the integrated circuit 18.

FIGS. 4A-D illustrates a process for assembling the package 10. In one embodiment, the process is a single pass four-sided dispensing process. In particular, the use of a vent hole 15 in implementing the IC package 10 facilitates the use of a single pass four-sided dispensing process.

A substrate vent opening 15 is first drilled or lazed lased into the substrate 12 at a predetermined location during the substrate manufacturing process. The substrate 12 may then be baked in an oven 28 to remove moisture from the substrate material, as shown in FIG. 4A. The substrate 12 is preferably baked at a temperature greater than the process temperatures of the underfill process steps to insure that moisture is not released from the substrate 12 in the subsequent steps. By way of example, the substrate 12 may be baked at 163 degrees Centigrade (C).

The integrated circuit 18 may then be mounted onto the substrate 12, as shown in FIG. 4B. The integrated circuit 18 is typically mounted by reflowing the solder bumps 20.

The underfill material 24 may be dispensed onto the substrate 12 along all four sides 26a-d of the IC 18 at a dispensing station 30, as shown in FIGS. 4C and 4D. FIG. 4C illustrates the flow of a typical underfill material 24 when the underfill material 24 is dispensed along all four sides 26a-d of the IC 18. FIG. 4D illustrates a top view of the underfilled IC package 10 having a substrate vent hole 15.

The underfill material 24 may be dispersed in a manner which creates a fillet that encloses and seals the IC 18. One advantage of using the four-sided dispense pattern is that it is able to form a uniform fillet at all four sides of the IC 18. A non-uniform fillet can result to cracking of the IC 18. In addition, the use of a four sided dispense process typically results in a fillet that provides a tight seal, so that delamination between the IC 18 and the underfill material 24 and/or between the underfill material 24 and the substrate 12 does not occur. This in turn results in strong adhesion between the IC 18 and the underfill material 24 and/or between the underfill material 24 and the substrate 12. The process control for forming this uniform fillet is simple and the process yield is high. By way of example, the underfill material 24 may be dispensed at a temperature of approximately 80°-120° C.

The use of a single pass dispense pattern reduces the underfill material interaction effects of multiple passes. During multiple passes, the underfill material is subjected to heating and gelling before subsequent passes. The use of a single pass dispense process results in a more robust process, reduced processing time and eliminates the need for tight material gelling control.

The underfill material 24 may be cured into a hardened state. The underfill material 24 may be cured at a temperature of approximately 150° C. After the underfill material 24 is cured, solder balls 22 can then be attached to the substrate 12, typically with a reflow process, to complete the package 10.

The implementation of the present invention reduces void formation by allowing out-gassing of trapped air from the center of the substrate 12 to vent when the underfill material 24 is dispensed at four sides of the IC 18. In addition, the vent hole 15 allows the underfill material 24 to flow under capillary effect before and during the curing process. As a result, the time control of the underfill material 24 is not as critical as compared to existing processes in which multiple passes are required. This provides the opportunity for eliminating infra red (IR) and/or convective heating, which are typically required in processes utilizing multiple passes, so as to enhance the underfill material 24 flow for subsequent dispense passes.

The use of a substrate vent hole 15 also shortens the flow travel distance to half, since a four sided dispense process may be used, as described above. This in turn reduces the time needed for providing a full underfill and thus provides the opportunity for eliminating a flow enhancement heating process, such as the IR and BTU heating processes, after underfill dispensing. The use of a vent hole 15 reduces the characterization work needed for underfill process development, which in turn reduces the intense handling and timing interaction associated with the equipment and process. As a result, operational costs are reduced, while manufacturing yields are increased.

While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, which are apparent to persons skilled in the art to which the invention pertains are deemed to lie within the spirit and scope of the invention.

Claims

1. A process for assembling an integrated circuit, comprising:

providing an a single opening through a substrate having a first surface having a portion upon which the integrated circuit is mounted and a second surface, said single opening being non-occluded at the second surface and having a diameter ranging from about 20 micrometers to about 62 micrometers;

attaching an integrated circuit to said substrate, said integrated circuit having four sides;

out-gassing through the said opening while dispensing an underfill material at at least one side of the along said four sides of said integrated circuit, the said underfill material completely filling a space between said integrated circuit and said substrate, said dispensing comprising a single pass dispensing pattern.

2. The process of claim 1, wherein the act of providing comprises:

drilling said opening through said substrate, a first end of said opening having a diameter substantially equal to a diameter of a second end of said opening.

3. The process of claim 1, wherein the act of providing comprises lazing lasing said opening through said substrate, a first end of said opening having a diameter substantially equal to a diameter of a second end of said opening.

4. The process of claim 1, wherein the act of providing comprises providing said opening of at a predetermined location of said substrate.

5. The process of claim 1, wherein in the act of providing comprises providing said opening at a low-stress location of said substrate.

6. The process of claim 1, wherein the act of providing comprises providing said opening at a center of said substrate.

7. The process of claim 1, further comprising attaching a solder ball to said substrate.

8. A process for underfilling an integrated circuit, comprising:

providing a substrate having a single vent opening, said single vent opening having a diameter ranging from about 20 mm micrometers to about 62 mm micrometers with a first end of said single vent opening at a top surface of said substrate being substantially equal in diameter to a second end of said single vent opening at a bottom surface of said substrate and said second end of said single vent opening being non-occluded;

mounting said integrated circuit to said top surface of the substrate, said integrated circuit having four sides; and

out-gassing through said single vent opening while dispensing an underfill material along said four sides of said integrated circuit, said underfill material being attached to said integrated circuit and said substrate, said underfill material completely filling a space between said integrated circuit and said substrate;, and said dispensing comprising a single pass dispensing pattern.

9. The process of claim 8, further comprising:

curing said underfill material.

10. A process comprising:

providing a single vent opening through a substrate, said single vent opening having a diameter ranging from about 20 mm micrometers to 62 mm micrometers with a top of the single vent opening being substantially uniform in diameter to a bottom of the single vent opening and said single vent opening being non-occluded at the bottom of the single vent opening;

attaching and an integrated circuit to said substrate above the top of the single vent opening, said integrated circuit having four sides; and

out-gassing through said single vent opening while dispensing an underfill material along said four sides of said integrated circuit, said underfill material completely filling a space between said integrated circuit and said substrate, and said dispensing comprising a single pass dispensing pattern.

11. The process of claim 10, wherein the act of providing comprises drilling said opening through said substrate, the bottom of the single vent opening is non-occluded.

12. The process of claim 10, wherein the act of providing comprises lazing lasing said opening through said substrate.

13. The process of claim 10, wherein the act of providing comprises providing said opening at a low-stress location of said substrate.

14. The process of claim 10, wherein the act of providing comprises providing said opening at a center of said substrate.

15. The process of claim 10, further comprising attaching a solder ball to said substrate.

16. The process of claim 10, wherein said substrate has a first surface and a second opposite surface, said opening extending from the first surface to the second opposite surface.