BRIEF DESCRIPTION OF THE DRAWINGS
The subject regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 illustrates one example of a substrate, in accordance with an embodiment of the present invention;
FIG. 2 illustrates one example of a mold compound affixed to the substrate shown in FIG. 1;
FIG. 3 illustrates one example of a cavity disposed in the mold compound shown in FIG. 2;
FIG. 4 illustrates one example of a circuit disposed in the cavity shown in FIG. 3;
FIG. 5 illustrates one example of the circuit affixed to the combination of the mold compound and the substrate shown in FIG. 4;
FIG. 6 illustrates one example of an alternative embodiment of the circuit affixed to the combination of the mold compound and the substrate shown in FIG. 5;
FIG. 7 illustrates one example of an alternative embodiment of the mold compound shown in FIG. 3;
FIG. 8 illustrates one example of the circuit disposed on the combination of the mold compound and the substrate shown in FIG. 7;
FIG. 9 illustrates one example of the circuit affixed to the combination of the mold compound and the substrate shown in FIG. 8;
FIG. 10 illustrates one example of an alternative embodiment of the circuit affixed to the combination of the mold compound and the substrate shown in FIG. 9;
FIG. 11 illustrates one example of an alternative joining of the substrate and the mold compound shown in FIG. 2;
FIG. 12 illustrates one example of an alternative mold compound shown in FIG. 11;
FIG. 13 illustrates one example of the circuit being joined to the substrate shown in FIG. 12;
FIG. 14 illustrates one example of the circuit being adhesively joined to the substrate shown in FIG. 13;
FIG. 15 illustrates one example of an alternative embodiment of the circuit and the substrate shown in FIG. 14;
FIG. 16 illustrates one example of an alternative embodiment of the circuit and the substrate shown in FIG. 15;
FIG. 17 illustrates one example of an alternative embodiment of the circuit and the substrate in FIG. 16;
FIG. 18 illustrates one example of an alternative embodiment of the circuit and the substrate of FIG. 17; and
FIG. 19 illustrates one example of an alternative embodiment of the circuit and the substrate of FIG. 18.
The detailed description explains the preferred embodiment of the invention, together with advantages and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The disclosed invention solves the problem of circuit-package interaction by pre-compensating the package substrate thermal expansion before circuit assembly to the substrate. A substrate used to provide interconnect from a device, such as a semiconductor or integrated circuit (IC), etc., is injection molded with a mold compound on one side of the substrate. The type of mold compound, the geometry and the thickness is predetermined so the substrate and mold compound composite will be under a particular stress/strain. The result will be a pre-compensated package that will provide a low-stress interface between the IC device and the substrate. When the IC is attached to the substrate via a solder bump or other electrical connection and subjected to an elevated temperature reflow profile, the difference in the thermal expansion between the different materials (IC, solder bump, substrate) will be minimized. The stress/strain associated with the difference in thermal expansion of the interfaces will also be minimized.
Referring initially to FIGS. 1 and 2, a thermal expansion pre-compensated package system 10 is shown. The system 10 includes a substantially flat substrate 20, which is formed from multi-layered laminations of alternating disposed dielectric and conductive layers. The substrate 20 includes a first planar surface 22 and a second planar surface 24. The first planar surface 22 and the second planar surface 24 are parallel and opposed to each other.
The system 10 further includes a substantially flat mold compound 30 including a third planar surface 32 and a fourth planar surface 34. The fourth planar surface 34 is affixed to the first planar surface 22 of the substrate 20 to provide a low stress/strain interface. The type of mold compound 30, the geometry and the thickness are predetermined so that the substrate 20 and the mold compound 30 are subjected to a particular stress/strain.
Referring to FIG. 3, the mold compound 30 has been further formed to include a cavity 40. The cavity 40 is formed in the third planar surface 32 of the mold compound 30 such that a circuit 50 having a fifth planar surface 52 and a sixth planar surface 54 may be disposed within the cavity 40, as shown in FIG. 4. The circuit 50 is electrically coupled to the supporting substrate 20. The circuit 50 may be a semiconductor, an integrated circuit, etc.
Referring to FIG. 4, the system 10 further includes a plurality of solder bump pads 60. Each solder bump pad 60 includes a top surface 62 and a bottom surface 64. The top surface 62 of each solder bump pad 60 is affixed to the sixth planar surface 54 of the circuit 50. The bottom surface 64 of each solder bump pad 60 is affixed to the first planar surface 22 of the substrate 20 such that the solder bump pads 60 form a mechanical and an electrical connection between the circuit 50 and the substrate 20.
Referring to FIG. 5, the cavity 40 is filled with an adhesive layer 100 to reinforce the mechanical connection between the circuit 50 and the mold compound 30. Optionally, the circuit 50 may be encapsulated by applying an epoxy layer 110 over the combination of the circuit 50 and the mold compound, as shown in FIG. 6. The epoxy layer 110 provides high strength and further bonds the circuit 50 to the substrate 20 to further minimize stress at the solder connections during thermal cycling.
Referring to FIG. 7, an alternative embodiment of the mold compound 30 is shown. As previously explained, the mold compound 30 includes the third planar surface 32 and the fourth planar surface 34. This embodiment of the mold compound 30 further includes a plurality of cavities 126 that are spaced apart and aligned with one another.
The substrate 20 including the first planar surface 22 and the second planar surface 24 is affixed to the mold compound 30. More particularly, the first planar surface 22 of the substrate 20 is affixed to the fourth planar surface 34 of the mold compound 30 to provide a low stress/strain interface. As previously explained, the type of mold compound 30, the geometry and the thickness are predetermined so that the substrate 20 and the mold compound 30 are subjected to a particular stress/strain.
Referring to FIG. 8, the circuit 50 is disposed on top of the mold compound 30. Particularly, the sixth planar surface 54 of the circuit 50 is disposed on the third planar surface 32 of the mold compound 30. The circuit 50 is electrically coupled to the supporting substrate 20.
Referring to FIG. 9, the plurality of solder bump pads 60 are shown. The solder bump pads 60 are disposed in the cavities 126. The top surface 62 of each solder bump pad 60 is affixed to the sixth planar surface 54 of the circuit 50, such that the solder bump pads 60 form a mechanical and an electrical connection between the circuit 50 and the substrate 20.
The adhesive layer 100 is applied to the circuit 50 to affix the circuit 50 to the third planar surface 32 of the mold compound 30 to reinforce the mechanical connection between the circuit 50, the substrate 20 and the mold compound 30. Optionally, the circuit 50 may be encapsulated by applying the epoxy layer 110 over the combination of the circuit 50 and the mold compound 30, as shown in FIG. 10. The epoxy layer 110 provides high strength and further bonds the circuit 50 to the substrate 20 to further minimize stress at the solder connections during thermal cycling.
Referring to FIG. 11 an alternative embodiment of the disclosed invention is shown. In this embodiment, the substrate 20 is disposed upon the mold compound 30 as compared to the previous embodiment wherein the mold compound 30 has been disposed upon the substrate 20. More particularly, the second planar surface 24 of the substrate 20 is affixed to the third planar surface 32 of the mold compound 30.
Referring to FIG. 12, the plurality of cavities 126 are formed in the fourth planar surface 34 of the mold compound 30 such that the bottom side electrical pads of the substrate 20 are exposed.
Referring to FIG. 13, the sixth planar surface 54 of the circuit 50 is disposed upon the top surface 62 of the solder bump pads 60 and the bottom surface 64 of the solder bump pads 60 is disposed upon the first planar surface 22 of the substrate 20.
Referring to FIG. 14, the circuit 50 is adhesively joined via the adhesive layer 100 to the first planar surface 22 of the substrate 20. Optionally, as shown in FIG. 15, the circuit 50 may be encapsulated by adding the epoxy layer 110 over the combination of the circuit 50 and the substrate 20. Furthermore, a low modus conductive material 140 may optionally be used to fill the cavities 126 in the mold compound 30 as shown in FIG. 16.
Referring to FIG. 17, an alternative embodiment of the disclosed invention is shown. In this embodiment solder bump pads 60 are not utilized. The circuit 50 is joined via the adhesive layer 100 and via a wirebond 150 to the substrate 20. This embodiment may be encapsulated as previously explained via the epoxy layer 110 being applied over the combination of the circuit 50 and the substrate 20 as shown in FIG. 18. Optionally, the low modus conductive material 140 may be used to fill the cavities 126 in the mold compound 30 as shown in FIG. 19.
Referring to the Figures, a method for manufacturing a thermal expansion pre-compensated package system is shown. A substrate 20 is produced and then a mold compound 30 is affixed to the substrate 20 to provide a low stress/strain interface. Subsequently, a cavity 40 is formed in the mold compound 30.
Then, a circuit 50 is disposed in the cavity 40. Afterwards, a mechanical and an electrical connection between the circuit 50 and the substrate 20 formed. Then the cavity 40 is filled with an adhesive layer 100 to reinforce the mechanical connection between the circuit 50 and the substrate 20. Optionally, the combination of the circuit 50 and the substrate 20 may be encapsulated.
In accordance with an alternative method for manufacturing the thermal expansion pre-compensated package system 10, the combination of the substrate 20 and the mold compound 30 may be formed differently. More particularly, a plurality of cavities 126 may be formed in the mold compound 30. Then the circuit 50 disposed on top of the mold compound 30. Then a mechanical and an electrical connection formed between the circuit 50 and the substrate 20. Then the circuit 50 is adhesively affixed to the substrate 20 and the mold compound 30. Finally and optionally, the combination of the circuit 50 and the substrate 20 may be encapsulated by way of the encapsulation layer 110.
In accordance with an alternative method for manufacturing the thermal expansion pre-compensated package system 10, the combination of the substrate 20 and the mold compound 30 is formed differently. More particularly, the substrate 20 is disposed upon the mold compound 30. Then the plurality of cavities 126, are formed in the fourth planar surface 34 of the mold compound 30 such that the bottom side electrical pads of the substrate 20 are exposed. Then the circuit is disposed upon the top surface 62 of the solder bump pads 60 and the bottom surface 64 is disposed upon the first planar surface of the substrate 20. Then the circuit 50 may be adhesively joined via the adhesive layer 100 to the first planar surface of the substrate 20. Then, optionally, the circuit 50 may be encapsulated by adding the epoxy layer 110 over the combination of the circuit 50 and the substrate 20. Then, optionally also, a low modus conductive material 140 may be used to fill the cavities 126 in the mold compound 30.
In accordance with an alternative method for manufacturing the thermal expansion pre-compensated package system 10, the combination of the substrate 20 and the mold compound 30 is formed differently. In this embodiment the circuit 50 is joined via the adhesive layer 100 and via a wirebond 150 to the substrate 20. This embodiment may optionally be encapsulated by applying the epoxy layer 110 over the combination of the circuit 50 and the substrate 20. Optionally, the low modus conductive material 140 may be used to fill the cavities 126 in the mold compound 30.
While the preferred embodiment to the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.
Patent Application
20080061448
