1. Technical Field
This disclosure generally relates to packaging of integrated circuits and particularly relates to conversion of ball grid array (BGA) packages to pin grid array (PGA) packages.
2. Description of the Related Art
The packaging of integrated circuits (ICs) frequently depends upon the expected method for board mounting the ICs. Two of the IC packaging methods in widespread use are ball grid array (BGA) packaging and pin grid array (PGA) packaging. The semiconductor die within a BGA packaged IC is electrically coupled to “pads” disposed on a surface of the BGA package. Small solder balls are bonded to each of the BGA contact pads. Coupling the BGA package to an underlying circuit board is accomplished by melting the solder to provide the electrical and physical coupling between the BGA package and the underlying circuit board. Since the BGA package is mounted directly on the circuit board, the board space and height of the mounted BGA package is minimized. The relatively low height of the BGA package provides a popular and cost-effective solution for mounting ICs in smaller devices such as handheld computer and cellular telephones.
In contrast, the semiconductor die within a PGA package is electrically coupled to “pins” extending from a surface of the PGA package. Electrically coupling the PGA package to an underlying circuit board is accomplished by inserting the pins into a complimentary socket that is electrically and physically coupled to the underlying circuit board. Since the PGA package is coupled to a socket, PGA packaging is attractive where post-manufacture removal of the IC is necessary, for example, where availability of user replaceable components is envisioned. Currently costly different production lines are needed to manufacture BGA and PGA packages due to their inherently different physical architecture.
FIG. 1 is a prior art example demonstrating an attempt to use an external adapter 105 to permit a ball grid array package to be used in a socket made for a pin grid array package. The semiconductor die 110 is electrically coupled to the adapter 105 using a plurality of solder balls 115 as a standard BGA. The adapter 105 includes an insulating substrate 120 having a plurality of conductive pads 125 disposed thereupon. A plurality of conductors or vias 130 extends through the insulating substrate 120 to link each of the conductive pads 125 with a respective pin 135. The substrate 120 can include a variety of structures and conductive layers that when coupled to the plurality of vias 130 connect one or more of the conductive pads 125 to pins 135. The pins 135 become the pin grid array.
FIG. 2 is another prior art example demonstrating the use of another external pin grid array adapter 205 to permit a ball grid array package to be used in a socket made for a pin grid array package. Similar to the adapter 105 discussed above, the semiconductor die 210 is electrically coupled to the adapter 205 using a plurality of solder balls 215 as a standard BGA package. The adapter 205 includes an insulated substrate 220. Apertures are formed in the substrate 220 and the pins 230 are inserted in the through apertures. The pins 230 have enlarged heads 225 which are exposed on the top side of the adaptor 220. The apertures are formed in the substrate 220 at a location to align with the balls on the BGA package so that the enlarged head 225 of each pin 230 is assured of contacting a ball. Each of at least a portion of the heads 225 align with each of the solder balls 215 disposed on the surface of the ball grid array package 235. The pin grid array adapter 205 is coupled to the ball grid array package 235 by heating the solder balls 215 to provide the physical and electrical coupling between the ball grid array package 235 and the external pin grid array adapter 205.
To create the pin grid array package, the adapters depicted in FIGS. 1 and 2 both depend upon the coupling of an external pin grid array adapter 105, 205 to the ball grid array semiconductor die 110, 210, respectively. Multiple adapters 105, 205 are therefore needed to accommodate the wide variety of ball grid array packages. For every configuration of a ball grid array an entirely new design of an adaptor is needed, which requires additional time and tooling to prepare. Additionally, the need to conserve space within small form factor devices may limit or otherwise restrict the ability to use an “oversize” external pin grid array adapter having a sufficient pin count. Consequently, in certain applications, the external pin grid array adapter 105, 205 must be matched to an individual ball grid array. Any changes, design evolution, or modification to the ball gray array will require comparable time-consuming and expensive changes in the external pin grid array adapter 105, 205. Further, time and effort are required to align the adaptors with the BGA package and slight misalignment results in defective electrical connections. In some cases, the adapter might break apart from the package. A method enabling flexible and cost effective conversion of a ball grid array package to a pin grid array package is therefore desirable.