Method for assembling tape ball grid arrays

1. Field of the Invention

This invention relates generally to semiconductor integrated circuit packages, and more particularly to methods and apparatus pertaining to the manufacture of flex tape ball grid array packages.

2. Description of the Related Art

Tape ball grid array packages (TBGA's) are an increasingly common form of packaging for integrated circuits. TBGA's comprise a flexible plastic tape comprising a dielectric material, such as Kapton, and a metal pattern (traces) formed on the dielectric material. The metal pattern is connected to bond pads on an integrated circuit. Each of the traces is connected to a solder ball, which serves as the electrical interface between the package and a printed circuit board. In this manner, integrated circuit bond pads in TBGA's are electrically coupled to an appropriate solder ball.

The flexible tape material is relatively thin and therefore allows the entire package to be correspondingly thin and lightweight. These characteristics are beneficial for systems that are portable, such as cellular phones and other handheld electronic devices.

During the assembly of TBG's, due to the thin nature of the flexible tape, the tape must be supported while a die is attached to it. One conventional support structure for a flexable tape comprises, as shown in FIG. 1 a , a metal sheet 10 with openings 12 therein, including opening 12 a . The metal sheet 10 has sprocket holes such as hole 8 that allow it to moved along during the assembly process. For ease of description, the packaging of die will be described will be appreciated that the same process is applied to assembly a plurality of packages, one for each of the openings 12 .

As shown in FIG. 1 b , a flexible tape substrate 14 with a top side 13 (see FIG. 1 c ), to which a die will be attached, and a bottom side 15 , to which solder balls will be attached, is attached to the metal sheet 10 . Specifically, an adhesive is applied to the metal around the periphery of the opening 12 a and the periphery of the top side 13 is attached to the adhesive. The flexible tape substrate 14 is larger than the opening 12 a such that, as shown by dotted line in FIG. 1 c , the periphery of the top side 13 is covered by the metal sheet 10 when viewed from the top side 13 .

As shown in FIG. 1 d , a die 17 is attached to the top side 13 and wire bonds connect bond pads on the die 17 to traces on the top side 13 . After connecting the die to the top side 13 of the tape, and the flexible tape substrate 14 . Solder balls are then attached to the bottom side 15 , of the flexible tape, which also involves heating the metal sheet 10 and the flexible tape substrate 14 . Finally, the flexible tape substrate 14 is removed from the support by scribing around the molding to create an individual package.

The metal sheet 10 has different thermal expansion characteristics in comparison with the flexible tape substrate 14 . This mismatch causes the flexible tape substrate 14 to warp or stretch when the flexible tape substrate 14 and metal sheet 10 are heated together, which occurs during molding and solder ball attach, as described above. Warping and/or stretching of the flexible tape substrate 14 can damage the fine metal traces on the flexible tape substrate 14 and can cause the resulting package to be warped.

It would be desirable to decrease the warping or stretching of a flexible tape substrate.

The present invention decreases the warping or stretching of a flexible tape substrate. According to the present invention, a method for creating a package for a semiconductor die, the package comprising a flexible tape, comprises the following steps. A support with an opening has a plurality of arms extending through at a portion of the opening. For example, for a square opening, there may be eight arms, two extending from each side of the opening. The arms preferably form a “z” shape or some other shape with a transverse component.

The flexible tape is then attached to the ends of the arms within the opening such that the flexible tape is supported by the arms. A die is attached to the flexible tape, the die is preferably covered with a molding compound, and the die/flexible tape assembly is scribed from the support, thereby creating an individual package.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings in which:

FIGS. 1 a through 1 d show a conventional method for assembling a tape ball grid array package.

FIG. 2 shows an embodiment of a flexible tape substrate support according to the present invention.

FIGS. 3 a and 3 b show a top side and a bottom side, respectively, of a flexible tape substrate with tabs according to the present invention.

FIG. 4 shows the flexible tape substrate shown in FIG. 3 attached to the support shown in FIG. 2 .

FIG. 5 shows an alternate embodiment of a flexible tape substrate support according to the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

FIG. 2 shows a first embodiment of a flexible tape substrate support according to the present invention. As shown, a support 20 which is preferably a metal such as copper, has a plurality of openings 22 . Each of the openings 22 , such as opening 22 a which preferably comprises a rectangular opening has a plurality of arms 24 extending therefrom, the openings 22 and arms 24 are preferably created by stamping a metal sheet with an appropriate shape. In the embodiment shown in FIG. 2, the plurality of arms 24 comprises 8 arms, with two arms extending from each of the sides of the opening 22 a . As shown in FIG. 3 a, a flexible tape 30 with a top side 32 and a bottom side 33 (see FIG. 3 b ) has a plurality of tabs 36 around the periphery of the flexible tape 30 . The top side 32 of the tape 30 includes bond pads 37 for coupling to a die and traces 35 that connect to holes 34 for receiving solder balls 42 , as is shown in FIG. 3 b.

As shown in FIG. 4, the flexible tape 30 is attached with an adhesive to a corresponding one of the arms 24 a such that the arms are attached to the top side of the flexible tape 30 . (Note that in FIG. 4, the tabs 36 are obscured by the arms 24 a ). The opening's area is greater than the area of the flexible tape such that the flexible tape 30 is supported solely by the arms 24 a. (For purposes of illustration, only one piece of flexible tape is shown; it will be appreciated that a piece of flexible tape is attached to each of the openings 22 .)

As shown in FIG. 4, each of the arms 24 a preferably extends from an edge 54 of the support 22 defined by opening 22 a to a corresponding one of the tabs 36 such that a beginning 46 and end 48 of each of the arms 24 a are aligned on a first axis, shown as dotted line 50 , that is perpendicular to the edge 54 . Preferably, a portion of the arms 24 a extends away from the first axis 50 such that portions 52 of the arms 24 a are transverse to the first axis 50 . In the embodiment shown in FIG. 4, the arms 24 a are “n” shaped.

FIG. 5 shows an alternate embodiment of an arm 60 that may be used as one of the plurality of arms 24 a support wherein a plurality of arms are “z” shaped.

After the flexible tape has been attached to the support, the die attach step, the solder ball attach step,the molding step and the scribing steps as described with reference to the related art may be performed. Preferably, a molded layer is disposed such that it does not cover the tabs and the scribing step is performed such that the tabs 36 are not present in the resulting package.

Conclusion

Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.