1. Field of the Invention
The present invention relates generally to the packaging of electronic components. More particularly, the present invention relates to a stacked electronic component package and method for fabricating the same.
2. Description of the Related Art
To reduce the size of electronic component packages, electronic components such as semiconductor dies were stacked one upon another within a stacked electronic component package. To space the upper electronic component above the lower bond wires connected to the bond pads of the lower electronic component, a spacer was used.
The spacer was mounted to the upper surface of the lower electronic component inward of the bond pads on the upper surface of the lower electronic component. The lower bond wires were connected to the bond pads on the upper surface of the lower electronic component. The lower surface of the upper electronic component was mounted to the spacer, which spaced the lower surface of the upper electronic component away from the upper surface of the lower electronic component and the lower bond wires.
A spacer made of silicon, i.e., a silicon spacer, was used. As a silicon spacer is nonadhesive, use of the silicon spacer required an upper and lower adhesive. The lower adhesive mounted the lower surface of the silicon spacer to the upper surface of the lower electronic component inward of the bond pads of the lower electronic component. As the upper surface of the silicon spacer did not have adhesive applied thereto during mounting of the silicon spacer to the lower electronic component, the silicon spacer did not adhere to the vacuum head of the pickup tool that placed the silicon spacer on the lower electronic component.
The upper adhesive, e.g., a film adhesive, was applied to the entire lower surface of the upper electronic component. The upper electronic component having the upper adhesive applied to the entire lower surface of the upper electronic component was then mounted to the silicon spacer.
An alternative to the silicon spacer was a double-sided film spacer. A double-sided film spacer had adhesive on both the upper and lower surfaces of the double-sided film spacer. This allowed the double-sided film spacer to be mounted directly to the upper surface of the lower electronic component and the upper electronic component to be directly mounted to the double-sided film spacer with or without the application of additional adhesives. This simplified manufacturing resulting in a lower manufacturing cost of the stacked electronic component package. Further, a double-sided film spacer was less expensive than a silicon spacer again resulting in a lower manufacturing cost of the stacked electronic component package.
One problem associated with the double-sided film spacer was that the adhesive upper surface of the double-sided film spacer adhered to the vacuum head of the pickup tool. Thus, during retraction of the vacuum head, the double-sided film spacer was pulled from the upper surface of the lower electronic component resulting in the formation of interfacial voids between the lower surface of the double-sided film spacer and the upper surface of the lower electronic component. The interfacial voids sometimes caused delamination of the double-sided film spacer from the lower electronic component thus reducing the yield of the stacked electronic component package and in some cases adversely impacting the package reliability.
In accordance with one embodiment, a method of fabricating a stacked electronic component package includes placing a single-sided film spacer on an upper surface of a lower electronic component inward of bond pad with a pickup tool. After being adhered to the upper surface of the lower electronic component, the pickup tool is retracted from the single-sided film spacer.
An upper surface of a film, e.g., an organic film, of the single-sided film spacer is nonadhesive. Accordingly, the single-sided film spacer does not stick to the pickup tool during retraction of the pickup tool from the single-sided film spacer. Thus, voiding between the single-sided film spacer and the lower electronic component and the associated loss of yield of fabrication of the stacked electronic component package is minimized. Further, the single-sided film spacer is relatively inexpensive compared to a silicon spacer and thus the stacked electronic component package is fabricated with a minimal cost.
These and other features of the present invention will be more readily apparent from the detailed description set forth below taken in conjunction with the accompanying drawings.
In the following description, the same or similar elements are labeled with the same or similar reference numbers.
In accordance with one embodiment, referring to
An upper surface 130U of a film 130, e.g., an organic film, of single-sided film spacer 126 is not adhesive. Accordingly, single-sided film spacer 126 does not stick to pickup tool 404 during retraction of pickup tool 404 from single-sided film spacer 126. Thus, voiding between single-sided film spacer 126 and lower electronic component 114 and the associated loss of yield of fabrication of stacked electronic component package 100 is minimized. Further, single-sided film spacer 126 is relatively inexpensive compared to a silicon spacer and thus stacked electronic component package 100 is fabricated with a minimal cost.
More particularly,
Formed on upper surface 102U of substrate 102 are a plurality of electrically conductive upper, e.g., first, traces 104, which include a first upper trace 104A and a second upper trace 104B. Formed on lower surface 102L of substrate 102 are a plurality of electrically conductive lower, e.g., second, traces 106, which include a first lower trace 106A and a second lower trace 106B. Extending through substrate 102 from lower surface 102L to upper surface 102U are a plurality of electrically conductive vias 108, which include a first via 108A and a second via 108B. Lower traces 106 are electrically connected to upper traces 104 by vias 108. To illustrate, lower traces 106A, 106B are electrically connected to upper traces 104A, 104B by vias 108A, 108B, respectively. Upper and lower surfaces 102U, 102L of substrate 102 may include an outermost insulative cover coat, e.g., an epoxy based resin, through which electrically conductive bond fingers, e.g., the end portions, of upper traces 104 and pads 110 are exposed.
Formed on lower traces 106 are electrically conductive pads 110, which include a first pad 110A and a second pad 110B. Formed on pads 110 are electrically conductive interconnection balls 112, e.g., solder. To illustrate, pads 110A, 110B are formed on lower traces 106A, 106B, respectively. First and second interconnection balls 112A, 112B of the plurality of interconnection balls 112 are formed on pads 110A, 110B, respectively. Interconnection balls 112 are used to connect stacked electronic component package 100 to a larger substrate such as a printed circuit mother board or another electronic component package.
Although a particular electrically conductive pathway between upper traces 104 and interconnection balls 112 is described above, other electrically conductive pathways can be formed. For example, contact metallizations can be formed between the various electrical conductors. Alternatively, pads 110 are not formed and interconnection balls 112 are formed directly on lower traces 106.
Further, instead of straight though vias 108, in one embodiment, substrate 102 is a multilayer laminate substrate and a plurality of vias and/or internal traces form the electrical interconnection between traces 104 and 106.
In yet another embodiment, interconnection balls 112 are distributed in an array format to form a ball grid array (BGA) type package. Alternatively, interconnection balls 112 are not formed, e.g., to form a metal land grid array (LGA) type package. In yet another alternative, pads 110/interconnection balls 112 are not formed, e.g., to form a leadless chip carrier (LCC) type package. In another embodiment, stacked electronic component package 100 is inserted into a socket that is pre-mounted on the larger substrate, e.g., on the printed circuit mother board. BGA, LGA and LCC type modules are well known to those of skill in the art.
In another embodiment, a flex connector, sometimes called an edge connector or flex strip, is electrically connected to lower traces 106, e.g., for applications where stacked electronic component package 100 is remote from the larger substrate. Other electrically conductive pathway modifications will be obvious to those of skill in the art.
Referring still to
Lower electronic component 114 further includes an upper, e.g., second, surface 114U. Bond pads 120 of lower electronic component 114 are formed on upper surface 114U adjacent sides 114S of lower electronic component 114. In this embodiment, upper surface 102U, lower surface 114L, and upper surface 114U are parallel to one another. Although various structures may be described as being parallel or perpendicular, it is understood that the structures may not be exactly parallel or perpendicular but only substantially parallel or perpendicular to within accepted manufacturing tolerances.
In accordance with this embodiment, lower electronic component 114 is a semiconductor die, sometimes called a lower semiconductor die, integrated circuit chip or an active component. However, in other embodiments, lower electronic component 114 is another type of electronic component such as a passive component, e.g., a resistor, capacitor or inductor.
Upper traces 104 are electrically connected to bond pads 120 by lower bond wires 122. To illustrate, a first bond pad 120A of the plurality of bond pads 120 is electrically connected to upper trace 104A by a first lower bond wire 122A of the plurality of lower bond wires 122.
An upper, e.g., second, electronic component 124 is mounted to lower electronic component 114. More particularly, a lower, e.g., first, surface 124L of upper electronic component 124 is mounted to upper surface 114U of lower electronic component 114 with a single-sided film spacer 126 and an upper electronic component adhesive 128.
In accordance with this embodiment, lower surface 124L of upper electronic component 124 corresponds to upper surface 114U of lower electronic component 114. Stated another way, lower surface 124L of upper electronic component 124 has the same shape, e.g., a rectangular shape having the same length and width, as upper surface 114U of lower electronic component 114 such that the total surface areas of lower surface 124L and upper surface 114U are equal. However, in other embodiments, the total area of lower surface 124L of upper electronic component 124 is greater than or less than, i.e., different than, the total area of upper surface 114U of lower electronic component 114. Such an example is discussed below in reference to
Lower surface 130L of film 130 is directly mounted to upper surface 114U of lower electronic component 114 with lower film adhesive 132. More particularly, a lower, e.g., first, surface 132L of lower film adhesive 132 is mounted to upper surface 114U of lower electronic component 114. Generally, lower film adhesive 132, sometimes called a spacer film adhesive, is adhesive such that lower surface 132L of lower film adhesive 132 directly adheres to upper surface 114U of lower electronic component 114.
Similarly, an upper, e.g., second, surface 132U of lower film adhesive 132 is mounted to lower surface 130L of film 130. Again, lower film adhesive 132 is adhesive such that upper surface 132U of lower film adhesive 132 directly adheres to lower surface 130L of film 130.
In accordance with this embodiment, lower film adhesive 132 is an adhesive film, sometimes called a film adhesive. Generally, lower film adhesive 132 is a preformed film of adhesive, e.g., a layer or sheet of adhesive. As such, lower film adhesive 132 has sides 132S which are substantially vertical and coincident with sides 130S of film 130. In one embodiment, lower film adhesive 132 is a preformed layer of epoxy. In contrast, a conventional paste adhesive would be applied as a viscous paste and thus would have curved protruding sides instead of substantially vertical sides 132S of lower film adhesive 132. However, in one embodiment, lower film adhesive 132 is a film adhesive that flows during the curing process, and thus has curved protruding sides.
Upper film adhesive 128, sometimes called a second electronic component film adhesive, is mounted to and covers the entire lower surface 124L of upper electronic component 124. Generally, upper film adhesive 128 is adhesive, i.e., sticky, such that an upper, e.g., first, surface 128U of upper film adhesive 128 directly adheres to lower surface 124L of upper electronic component 124.
In accordance with this embodiment, upper film adhesive 128 is an adhesive film, sometimes called a film adhesive. Generally, upper film adhesive 128 is a preformed film of adhesive, e.g., a layer or sheet of adhesive. As such, upper film adhesive 128 has sides 128S which are substantially vertical and coincident with sides 124S of upper electronic component 124. In one embodiment, upper film adhesive 128 is a preformed layer of epoxy.
In accordance with this embodiment, upper film adhesive 128 is nonconductive, i.e., a dielectric. Upper film adhesive 128 is located vertically above bond pads 120. More particularly, upper film adhesive 128 is located vertically between bond pads 120 and lower surface 124L of upper electronic component 124.
Accordingly, upper film adhesive 128 protects lower surface 124L of upper electronic component 124 from lower bond wires 122 and vice versa. More particularly, upper film adhesive 128 prevents lower bond wires 122 from directly contacting and shorting to lower surface 124L.
In accordance with one embodiment, single-sided film spacer 126 spaces upper film adhesive 128 a distance above bond pads 120 sufficient to prevent lower bond wires 122 from contacting upper film adhesive 128. However, as indicated by the phantom bond wire 122-1 in
In accordance with another embodiment, lower bond wires 122 are bonded to bond pads 120 using a reverse bonding technique, sometimes called stand-off stitch bonding (SSB) to minimize the loop height of lower bond wires 122. By minimizing the loop height of lower bond wires 122, the thickness of single-sided film spacer 126 required to avoid contact between lower bond wires 122 and upper film adhesive 128 is also minimized.
As is well known to those of skill in the art, in reverse bonding, a ball 134 (indicated as a dashed line in
Referring again to
Upper traces 104 are electrically connected to bond pads 136 by upper bond wires 138. To illustrate, a first bond pad 136A of the plurality of bond pads 136 is electrically connected to upper trace 104B by a first upper bond wire 138A of the plurality of upper bond wires 138.
A package body 140, e.g., a cured liquid encapsulant or mold compound, encloses lower electronic component 114, single-sided film spacer 126, upper film adhesive 128, upper electronic component 124, lower bond wires 122, upper bond wires 138, and all or part of the exposed upper surface 102U of substrate 102. In one embodiment, package body 140 is vertically between and fills the space between bond pads 120 and upper film adhesive 128. In accordance with this embodiment, package body 140 extends inward to single-sided film spacer 126 and between upper film adhesive 128 and upper surface 114U of lower electronic component 114.
Referring now to
By using two lower film adhesives 202, 204, the thickness T1 of multilayer lower film adhesive 132B is greater than, e.g., double, the thickness of either lower film adhesive 202 or lower film adhesive 204. Although multilayer lower film adhesive 132B is illustrated and discussed as including two film adhesives, i.e., lower film adhesives 202, 204, it is understood that multilayer lower film adhesive 132B can be fabricated with more than two lower film adhesives depending upon the desired distance D between lower surface 128L of upper film adhesive 128 and upper surface 114U of lower electronic component 114. Additionally, the thickness of each individual film adhesive may be varied to adjust the overall thickness between lower surface 128L of upper film adhesive 128 and upper surface 114U of lower electronic component 114.
To illustrate, in one embodiment, multilayer lower film adhesive 132B is fabricated to include a third lower film adhesive in addition to lower film adhesives 202, 204 to increase distance D between lower surface 128L of upper film adhesive 128 and upper surface 114U of lower electronic component 114 compared to forming multilayer lower film adhesive 132B from only lower film adhesives 202, 204. In this manner, distance D is readily selected by using more or less lower film adhesives to form multilayer lower film adhesive 132B.
Referring now to
Single-sided film spacer sheet 326A includes a lower film adhesive sheet 332 and a film sheet 330. Single-sided film spacer sheet 326A is singulated, e.g., with a saw 350, thus forming a plurality of single-sided film spacers 126. Each single-sided film spacer 126 includes the respective singulated portion of lower film adhesive sheet 332 and film sheet 330.
A vacuum head 402 of a pickup tool 404, sometimes called a pick-and-place tool, grabs upper surface 130U of film 130 of single-sided film spacer 126 in a pick-and-place operation, sometimes called a spacer attach process. As is well-known to those of skill in the art, vacuum is applied to vacuum head 402 suctioning upper surface 130U of film 130 of single-sided film spacer 126 thus causing vacuum head 402 to grab single-sided film spacer 126.
Illustratively, single-sided film spacer 126 is removed from single-sided film spacer singulation tape 304 (
Single-sided film spacer 126 is placed on upper surface 114U of lower electronic component 114 inward of bond pads 120 by vacuum head 402. In one embodiment, single-sided film spacer 126 is pressed downward on to upper surface 114U of lower electronic component 114 by vacuum head 402 to ensure good adhesion between lower film adhesive 132 of single-sided film spacer 126 and upper surface 114U of lower electronic component 114.
After being adhered to upper surface 114U of lower electronic component 114, single-sided film spacer 126 is released from vacuum head 402, i.e., vacuum head 402 of pickup tool 404 is retracted from single-sided film spacer 126. Illustratively, vacuum to vacuum head 402 is discontinued thus discontinuing the suction on single-sided film spacer 126 by vacuum head 402.
As discussed above, upper surface 130U of film 130 of single-sided film spacer 126 is not adhesive. Accordingly, single-sided film spacer 126 does not stick to vacuum head 402 during retraction of vacuum head 402 from single-sided film spacer 126. Thus, voiding between single-sided film spacer 126 and lower electronic component 114 and the associated loss of yield of fabrication of stacked electronic component package 100 is minimized. Further, single-sided film spacer 126 is relatively inexpensive compared to a silicon spacer and thus stacked electronic component package 100 is fabricated with a minimal cost.
Referring again to
Bond pads 136 are electrically connected to respective lower traces 104 by upper bond wires 138. Lower electronic component 114, single-sided film spacer 126, upper film adhesive 128, upper electronic component 124, lower bond wires 122, upper bond wires 138, and all or part of the exposed upper surface 102U of substrate 102 are enclosed in liquid encapsulant or mold compound using any one of the number of encapsulation/molding techniques to form package body 140. Interconnection balls 112, e.g., solder balls, are formed on pads 110 thus completing fabrication of stacked electronic component package 100 although interconnection balls 112 are formed at earlier stages during the manufacturing process in other embodiments.
Referring now to
The drawings and the forgoing description gave examples of the present invention. The scope of the present invention, however, is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of the invention is at least as broad as given by the following claims.
This application is related to St. Amand et al., commonly assigned and co-filed U.S. patent application Ser. No. [ATTORNEY DOCKET NUMBER G0090], entitled “STACKED ELECTRONIC COMPONENT PACKAGE HAVING FILM-ON-WIRE SPACER”, which is herein incorporated by reference in its entirety.