Folded stacked package and method of manufacturing the same

A folded stacked package and a method of manufacturing the same are provided. The folded stacked package includes a flexible board or substrate comprising first, second and third device packaging units, and first and second folding unit units. The flexible board has wiring patterns formed thereon; one or more active devices disposed in at least one of the first, second, and third device packaging units; and one or more passive devices disposed on a surface of each of the first and second device packaging units. The passive devices include one or more first passive devices disposed on the surface of the first device packaging unit and one or more second passive devices disposed on the surface of the second device packaging unit. The first and second passive devices do not overlap each other when the flexible board is folded at the folding unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2011-0001103, filed on Jan. 5, 2011 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

Methods and apparatuses consistent with exemplary embodiments generally relate to package technology, and particularly, to a stacked package technology for electronic components.

2. Description of the Related Art

As the performance of information technology (IT) devices is improved, mobile information technology (IT) devices such as mobile phones are becoming increasingly light-weight, thin and small. In accordance with this trend, an increasing number of electronic devices have been mounted on or embedded in boards. A technique of mounting electronic devices on boards is referred to as surface package technology (SMT), and a technique of embedding electronic devices in boards is referred to as embedded package technology.

The integration of various types of modules into a single electronic device, i.e., digital convergence, has become widespread and is expected to grow further. New digital convergence systems are expected to become more compact and perform more functions. For this, various electronic devices are required to be able to be mounted on system boards.

The types of electronic devices that can be mounted together on system boards are not limited to active devices, and include passive devices. Examples of active devices include integrated circuit (IC) chips such as a memory chip, a logic chip, an image sensor and the like. Examples of passive devices include capacitors, resistors such as a pull-up resistor, a pull-down resistor and the like, inductors, antennas, and micro-electro-mechanical systems (MEMS) devices.

Stacked packages are largely classified into a package-on-package, a package-in-package, and a folded stacked package. The package-on-package is a stacked package structure in which one or more upper packages are stacked on top of a lower package and the upper packages and the lower package are electrically connected by solder balls, and the package-in-package is a stacked package structure in which a package is deposited inside another package, and particularly, on the electronic devices on the other package and the two packages are electrically connected through wire bonding. The package-on-package and the package-in-package are desirable in that they can directly adopt existing single package structures. However, the package-on-package and the package-in-package are relatively complicated stacked structures and often have poor electrical connections between packages.

The folded stacked package is a structure in which packaged or unpackaged electronic devices are mounted on or attached onto a multiple-folded flexible board or substrate. The folded stacked package has a relatively simple structure because the flexible board or substrate is folded after disposing or mounting electronic devices thereon. In addition, since electronic devices or packages in the folded stacked package are electrically connected through the flexible board or substrate, the folded stacked package is highly reliable in terms of electrical connections between the electronic devices or the packages.

SUMMARY

According to an aspect of an exemplary embodiment, there is provided a folded stacked package including a flexible board or substrate configured to include a folding unit and first and second device packaging units connected by the folding unit and having wiring patterns formed thereon; one or more first devices configured to be embedded in at least one of the first and second device packaging units; and one or more second devices configured to be mounted on a surface of each of the first and second device packaging units, wherein the second devices mounted on the surface of the first device packaging unit and the second devices mounted on the surface of the second device packaging unit do not overlap each other when the flexible board or substrate is folded at the folding unit.

According to an aspect of another exemplary embodiment, there is provided a folded stacked package including a flexible board or substrate configured to include a first device packaging unit, a first folding unit, a second device packaging unit, a second folding unit, and a third device packaging unit and having wiring patterns formed thereon; one or more active devices configured to be embedded in at least one of the first, second, and third second device packaging units; and one or more passive devices configured to be mounted on a surface of each of the first and second device packaging units, wherein the passive devices include one or more first passive devices mounted on the surface of the first device packaging unit and one or more second passive devices mounted on the surface of the second device packaging unit and the first passive devices and the second passive devices do not overlap each other when the flexible board or substrate is folded at the folding unit.

According to an aspect of another exemplary embodiment, there is provided a method of manufacturing a folded stacked package, the method including preparing a first flexible layer, which is divided into a first device packaging unit, a first folding unit, a second device packaging unit, a second folding unit, and a third device packaging unit and have wiring patterns formed thereon that are aligned side-by-side horizontally; bonding at least one active device onto each of the first, second, and third device packaging units; forming a second flexible layer on the first flexible layer so as not to expose the active devices; forming via holes, through which connection pads of the active devices are exposed, by etching at least one of the first and second flexible layers; forming vias by depositing a conductive material, and forming wiring patterns on at least one of the first and second flexible layers such that the wiring patterns are connected to the vias; and mounting one or more first passive devices on the first device packaging unit and one or more second passive devices on the second device packaging unit so that the first passive devices and the second passive devices are electrically connected to the wiring patterns, wherein the first passive devices and the second devices are arranged so as not to overlap each other when the first and second flexible layers are folded at the first folding unit.

DETAILED DESCRIPTION

Folded stacked packages according to exemplary embodiments can be suitable for use not only in IT devices (particularly, mobile IT devices such as a mobile phone) but also in bio-healthcare electronic devices and wearable electronic devices as a system integration package technology. For example, the folded stacked packages according to exemplary embodiments can be applied to mobile devices (such as mobile phones, including smart phones, personal digital assistants (PDAs), or portable multimedia players (PMPs)), portable computers (such as laptop computers or tablet computers), portable electronic devices (such as digital cameras or digital camcorders), connected health monitoring devices (such as heart disease bandage sensors) which can monitor the health conditions of an individual by being bonded onto the body of the individual, and implant devices which can be implanted into a limited space such as the body of an individual. The folded stacked packages according to exemplary embodiments can also be applied to portable electronic devices into which a variety of functions are integrated and non-portable electronic devices which need to be compact in size.

FIGS. 1A and 1Billustrate examples of a folded stacked package. More specifically,FIG. 1Aillustrates an example of a folded stacked package in an unfolded state, andFIG. 1Billustrates an example of a folded stacked package in a folded state. Referring toFIGS. 1A and 1B, folded stacked package10includes a flexible board or substrate20, first and second active devices32aand32b, first passive devices46aand second passive devices46b. The first and second active devices32aand32bmay be collectively referred to as the active devices32, and the first passive devices46aand the second passive devices46bmay be collectively referred to as the passive devices46. The sizes and thicknesses of the elements of the folded stacked package10may not be to scale and may be exaggerated for clarity and convenience, and the number and locations of wiring patterns42, first vias44aand second vias44bin the flexible board or substrate20are merely exemplary, and are not limited to those illustrated inFIGS. 1A and 1B. The first vias44aand the second vias44bmay be collectively referred to as the vias44.

As an example, the active devices32may be embedded in the flexible board or substrate20, and the passive devices46may be mounted on the flexible board or substrate20. As another example, the passive devices46may be embedded in the flexible board or substrate20, and the active devices32may be mounted on the flexible board or substrate20. As another example, some of the active devices32and some of the passive devices46may be embedded in the flexible board or substrate20, and other active devices32and other passive devices46may be mounted on the flexible board or substrate20.

The flexible board or substrate20includes first and second device packaging units22aand22b. The first and second device packaging units22aand22bmay be collectively referred to as the device packaging units22. For example, the flexible board or substrate20may be divided into the first device packaging unit22a, a folding unit24, and the second device packaging unit22b, and the first device packaging unit22a, the folding unit24, and the second device packaging unit22bmay be aligned side-by-side horizontally. The device packaging units22correspond to parts of the flexible board or substrate20on which the active devices32and/or the passive devices46are disposed. A folding unit24corresponds to a part of the flexible board or substrate20which can be folded so that the device packaging units22can face each other vertically. For example, the flexible board or substrate20may be formed of a flexible material such as a polymer (e.g., polyimide). As another example, at least the folding unit24may be formed of a flexible material, and the device packaging units22may be formed of a rigid material.

The active devices32are embedded in the device packaging units22. That is, the active devices32may be embedded in the flexible board or substrate20instead of being mounted on the flexible board or substrate20. Referring toFIGS. 1A and 1B, one active device32is embedded in each of the device packaging units22, but such arrangement is not restricted to this. For example, one of the device packaging units22may not have an active device32embedded therein. As another example, one of the device packaging units22may have more than one active device32embedded therein, in which case the more than one active device32may be aligned side-by-side or stacked one on top of another.

The active devices32, which are embedded in the device packaging units22, may be of the same type or of different types. There is no limit to the types of active devices32that can be embedded in the device packaging units22. Examples of the active devices32include nearly all types of active devices, such as memory chips, logic chips or the like. For example, the active devices32may all be memory chips that can configure a memory module. As another example, some of the active devices32may be memory chips, and other active devices32may be logic chips.

First connection pads34aand second connection pads34bmay be formed on the active devices32for electrical connections to external devices. The first connection pads34aand the second connection pads34bmay be collectively referred to as the connection pads34. As described above, since the active devices32are embedded in the flexible board or substrate20, the active devices32can be electrically connected to external devices via the vias44without the aid of, for example, solder joints, such as solder balls. Accordingly, a thickness t1of the folded stacked package10may be reduced by an amount corresponding to the height of solder joints.

One or more passive devices46may be mounted on each of the device packaging units22. That is, the passive devices46may be mounted on the flexible board or substrate20of the folded stacked package10, and may face the same direction, e.g., a direction from the bottom to the top of the flexible board or substrate20, as illustrated inFIG. 1A. Referring toFIGS. 1A and 1B, two passive devices46are mounted on each of the device packaging units22, but the exemplary embodiments are not restricted to this. That is, only one or three or more passive devices may be mounted on each of the device packaging units22. The number of passive devices46mounted on one of the device packaging units22may be different from the number of passive devices46mounted on the other device packaging units22. For example, the number of passive devices46mounted on the first device packaging unit22amay be greater than the number of passive devices46mounted on the second device packaging unit22b.

The passive devices46may be arranged on the device packaging units22such that the thickness t1of the folded stacked package10can be minimized. As an example, the passive devices46may be arranged on the flexible board or substrate20such that the first passive devices46aand the second passive devices46bcan be prevented from overlapping each other when the flexible board or substrate20is folded at the folding unit24, as illustrated inFIG. 1B. There is no limit to the manner in which the first passive devices46aand the second passive devices46bare arranged on the flexible board or substrate20so as not to overlap each other in a case in which the flexible board or substrate20is folded. For example, the passive devices46may be arranged on the flexible board or substrate20such that the first passive devices46aand the second passive devices46bcan be alternately arranged in a case in which the flexible board or substrate20is folded.

As another example, the passive devices46may be arranged on the flexible board or substrate20such that the second passive devices46bcan be disposed in the empty spaces between the first passive devices46aand/or on parts of the flexible board or substrate20where the first passive devices46aare not mounted, and that the first passive devices46acan be disposed in the empty spaces between the second passive devices46band/or on parts of the flexible board or substrate20where the second passive devices46bare not mounted. For example, the first passive devices46amay be disposed on the flexible board or substrate20at regular intervals, and the second passive devices46bmay be disposed on the flexible board or substrate20at regular intervals. In this example, since the first passive devices46aand the second passive devices46bdo not overlap each other when the flexible board or substrate20is folded, a distance d1between the first and second device packaging units22aand22bmay be minimized, and thus, the thickness t1of the folded stacked package10in the folded state may be reduced.

The passive devices46may be densely distributed over each of the device packaging units22. For example, when the number of first passive devices46ais greater than the number of second passive devices46b, two of the first passive devices46amay be disposed on either end of the first device packaging unit22a, as illustrated inFIG. 2A, so that the second passive devices46bcan be disposed between the two first passive devices46aon either end of the first device packaging unit22awhen the flexible board or substrate20is folded. When the number of first passive devices46ais only one greater than the number of second passive devices46b, the second passive devices46bmay be disposed only between the first passive devices46awhen the flexible board or substrate20is folded. In this case, since the passive devices46are densely distributed over each of the device packaging units22, it is possible to increase the packaging density of the folded stacked package10and minimize a width w1of the folded stacked package10.

The wiring patterns42are formed on the surface of the flexible board or substrate20. For example, the wiring patterns42may be formed of copper foil having a predetermined thickness by using a patterning technique involving an etching process (e.g., photolithography) well known to one of ordinary skill in the art to which the aspects of the exemplary embodiments pertain. The wiring patterns42may not necessarily need to be formed of copper, and may be formed of another conductive material having excellent electrical properties.

The wiring patterns42are merely exemplary. In a case in which the active devices32and the passive devices46are all electrically connected, the wiring patterns42may be formed in different shapes or at different positions as compared toFIG. 1A. For example, the shape of the wiring patterns42may vary according to the electrical properties of the folded stacked package10and how the active devices32and the passive devices46are electrically connected. The wiring patterns42may be formed not only on the device packaging units22but also on the folding unit24. The wiring patterns42are illustrated inFIG. 1Aas being formed only on the top surface of the flexible board or substrate20, but the exemplary embodiments are not limited thereto and the wiring patterns42may also be formed at the bottom of the flexible board or substrate20. Some of the wiring patterns42are electrically connected to external connection ports (not shown) for electrically connecting the folded stacked package10to an external device.

The active devices32, which are embedded in the flexible board or substrate20, may be electrically connected to the wiring patterns42via the vias44. The vias44are formed of a conductive material such as copper. The vias44may be formed of the same material as or a different material from that of the wiring patterns42. The vias44electrically connect the connection pads34of the active devices32and the wiring patterns42and may be formed to extend outwardly from the inside of the flexible board or substrate20.

The vias44electrically connect the inside of the flexible board or substrate20and the devices formed on the flexible board or substrate20. The vias44may be formed by forming via holes in the flexible board or substrate20and filling the via holes with a conductive material. The wiring patterns42or the passive devices46may be disposed on the vias44. For example, the passive devices46may be disposed directly over the active devices32, which are embedded in the flexible board or substrate20. In this example, the length of the electrical connections between the active devices32and the passive devices46may be minimized, and there is no need to penetrate the flexible board or substrate20. Therefore, it is possible to minimize parasitic resistance or parasitic inductance and thus to improve the electrical properties of the folded stacked package10.

The vias44are different from plated through holes (PTHs), which electrically connect devices formed on opposite sides of a substrate. PTHs are formed through a package board as electrical connections. PTHs occupy a relatively large area, and may thus decrease the packaging density of a packaging board. In a folded stacked package having PTHs, long loops are generally formed between devices. Thus, the electrical properties of a folded stacked package having PTHs may deteriorate due to parasitic resistance and parasitic inductance.

Since the vias44occupy a smaller area than PTHs and the active devices32and the passive devices46can be disposed above or below the vias44, the use of the vias44may increase the packaging density of the folded stacked package10. Since the passive devices46can be disposed directly above the active devices32, the electrical connections between the active devices32and the passive devices46may be reduced, and thus, the electrical properties of the folded stacked package10may be improved.

Referring toFIG. 1B, once the flexible board or substrate20is folded at the folding unit24, the first and second device packaging units22aand22bmay be bonded together by a bonding unit52. The bonding unit52may be formed of a dielectric material. As an example, the bonding unit52may be formed of a cured adhesive paste to provide improved adhesion between the passive devices46. As another example, the bonding unit52may be formed of a dielectric material. There is nearly no limit to the type of material that can be used to form the bonding unit52. For example, the bonding unit52may be formed of a prepreg prepared by impregnating a base substrate formed of paper with an uncured material such as an epoxy resin, a polyimide resin, a bismaleimides resin, or a phenol resin and curing the base substrate.

FIGS. 2A and 2Billustrate examples of a folded stacked package. More specifically,FIG. 2Aillustrates another example of a folded stacked package in an unfolded state, andFIG. 2Billustrate another example of a folded stacked package in a folded state. Referring toFIGS. 2A and 2B, folded stacked package110includes a flexible board or substrate120, first, second, and third active devices132a,132b, and132c, and first passive devices146aand second passive devices146b. The first, second, and third active devices132a,132b, and132cmay be collectively referred to as the active devices132, and the first passive devices146aand the second passive devices146bmay be collectively referred to as the passive devices146. The sizes and thicknesses of the elements of the folded stacked package10may be exaggerated for clarity and convenience, and the number and locations of wiring patterns142, first vias144a, second vias144b, and third vias144cin the flexible board or substrate120are merely exemplary, and are not limited to those illustrated inFIGS. 2A and 2B. The first vias144a, the second vias144b, and the third vias144cmay be collectively referred to as the vias144. The folded stacked package110will hereinafter be described in detail, focusing mainly on differences with the folded stacked package10illustrated inFIGS. 1A and 1B.

As an example, the active devices132may be embedded in the flexible board or substrate120, and the passive devices146may be mounted on the flexible board or substrate120. As another example, the passive devices146may be embedded in the flexible board or substrate120, and the active devices132may be mounted on the flexible board or substrate120. As another example, some of the active devices132and some of the passive devices146may be embedded in the flexible board or substrate120, and other active devices132and other passive devices146may be mounted on the flexible board or substrate120.

The flexible board or substrate120may include the first, second, and third device packaging units122a,122b, and122c, which are connected to one another by first and second folding units124aand124b. The first and second folding units124aand124bmay be collectively referred to as the folding units124. For example, the flexible board or substrate120may be divided into the first device packaging unit122a, the first folding unit124a, the second device packaging unit122b, the second folding unit124b, and the third device packaging unit122c, and the first device packaging unit122a, the first folding unit124a, the second device packaging unit122b, the second folding unit124b, and the third device packaging unit122cmay be aligned side-by-side horizontally. The device packaging units122correspond to parts of the flexible board or substrate120on which the active devices132and/or the passive devices146are disposed. The folding units124correspond to parts of the flexible board or substrate120which can be actually folded such that the device packaging units122can be disposed vertically with respect to one another.

The active devices132are embedded in the device packaging units122. That is, the active devices132may be embedded in the flexible board or substrate120instead of being mounted on the flexible board or substrate120. Referring toFIGS. 2A and 2B, one active device132is embedded in each of the device packaging units122, but the exemplary embodiments are not restricted to this. First connection pads134a, second connection pads134b, and third connection pads134cmay be disposed on the active devices132for electrical connections to external devices. The first connection pads134a, the second connection pads134b, and the third connection pads134cmay be collectively referred to as the connection pads134. Due to the connection pads134, the folded stacked package110, like the folded stacked package10illustrated inFIGS. 1A and 1B, the connection pads134, do not need solder joints, such as solder balls.

One or more passive devices146may be mounted on each of the device packaging units122. As an example, the passive devices146may be mounted on the first and second device packaging units122aand122b, but not on the third device packaging unit122c. In this example, since no passive devices are disposed in the space between the second and third device packaging units122band122cwhen the flexible board or substrate120is folded, as illustrated inFIG. 2B, a thickness t2of the folded stacked package110may be reduced. As another example, the passive devices146may also be mounted on the third device packaging unit122c, according to another aspect of the exemplary embodiments.

The passive devices146may be mounted on the flexible board or substrate120, and may face the same direction, e.g., a direction from the bottom to the top of the flexible board or substrate120, as illustrated inFIG. 2A. Referring toFIGS. 2A and 2B, three passive devices146and two passive devices146are mounted on the first and second device packaging units122aand122b, respectively, but the exemplary embodiments are not restricted to this. As an example, the number of passive devices146mounted on the first device packaging unit122amay be the same as the number of passive devices146mounted on the second device packaging unit122b. As another example, the number of passive devices146mounted on the first device packaging unit122amay be different from, for example, less than, the number of passive devices146mounted on the second device packaging unit122b.

The passive devices146may be arranged on the device packaging units122such that the thickness t2of the folded stacked package110can be minimized, as illustrated inFIG. 2B.

As an example, the passive devices146may be arranged on the flexible board or substrate120such that the first passive devices146aand the second passive devices146bcan be prevented from overlapping each other when the flexible board or substrate120is folded at the first folding unit124a, as illustrated inFIG. 2B. There is no limit to the manner in which the first passive devices146aand the second passive devices146bare arranged on the flexible board or substrate120so as not to overlap each other in a case in which the flexible board or substrate120is folded.

As another example, the passive devices146may be arranged on the flexible board or substrate120such that the second passive devices146bcan be disposed in the empty spaces between the first passive devices146aand/or on parts of the flexible board or substrate120where the first passive devices146aare not mounted, and that the first passive devices146acan be disposed in the empty spaces between the second passive devices146band/or on parts of the flexible board or substrate120where the second passive devices146bare not mounted. In this example, since the first passive devices146aand the second passive devices146bdo not overlap each other when the flexible board or substrate120is folded, a distance d2between the first and second device packaging units122aand122bmay be minimized, and thus, the thickness t2of the folded stacked package110in the folded state may be reduced.

The passive devices146may be densely distributed over each of the first and second device packaging units122aand122b. For example, when the number of first passive devices146ais greater than the number of second passive devices146b, two of the first passive devices146amay be disposed on either end of the first device packaging unit122aso that the second passive devices146bcan be disposed between the two first passive devices146aon either end of the first device packaging unit122awhen the flexible board or substrate120is folded. When the number of first passive devices146ais only one greater than the number of second passive devices146b, the second passive devices146bmay be disposed only between the first passive devices146awhen the flexible board or substrate120is folded.

The wiring patterns142are formed on the surface of the flexible board or substrate120. The wiring patterns142are merely exemplary. For example, the shape of the wiring patterns142may vary according to the electrical properties of the folded stacked package110and how the active devices132and the passive devices146are electrically connected. The wiring patterns142may be formed not only on the first and second device packaging units122aand122bbut also on the folding units124and the third device packaging unit122c.

The active devices132, which are embedded in the flexible board or substrate120, may be electrically connected to the wiring patterns142via the vias144. The vias144are formed of a conductive material such as copper. The vias144may be formed of the same material as or a different material from that of the wiring patterns142. The vias144electrically connect the connection pads134of the active devices132and the wiring patterns142and may be formed to extend outwardly from the inside of the flexible board or substrate20.

The vias144, as compared to PTHs, may increase the packaging density of the folded stacked package110and may improve the electrical properties of the folded stacked package110by reducing the electrical connections between the active devices132and the passive devices146.

Referring toFIG. 2B, once the flexible board or substrate120is folded twice at the first and second folding units124aand124b, the first and second device packaging units122aand122bmay be bonded together by a first bonding unit152a, and the second and third device packaging units122band122cmay be bonded together by a second bonding unit152b. As an example, the first bonding unit152amay be formed of a cured adhesive paste to provide improved adhesion between the passive devices146, and the second bonding unit152bmay be formed of a bonding sheet. As another example, the first and second bonding units152aand152bmay both be formed of a dielectric material.

The folded stacked packages10and110are merely exemplary. For example, referring toFIG. 2B, a plurality of passive devices may also be disposed in the space between the second and third device packaging units122band122c, i.e., in a part of the folded stacked package110where the second bonding unit152bis disposed, without overlapping one another. In this example, the width of the second folding unit124bmay be increased. Thus, the distance between the second and third device packaging units122band122cmay be increased, and the width w2of the folded stacked package110may be further reduced. As another example, the folded stacked package110may also include a third folding unit (not shown) and a fourth device packaging unit (not shown), and one or more passive devices may be disposed not only on the first, second, and third device packaging units122a,122b, and122cbut also on the fourth device packaging unit.

An example of a method of manufacturing a folded stacked package, and more particularly, the folded stacked package110illustrated inFIGS. 2A and 2B, will hereinafter be described in detail with reference toFIGS. 3A through 3E. Further, the following example of a method of manufacturing a folded stacked package can be equally applied to the folded stacked package10illustrated inFIGS. 1A and 1B.

FIGS. 3A through 3Eillustrate an example of a method of manufacturing a folded stacked package, and more particularly, the folded stacked package110illustrated inFIGS. 2A and 2B. By folding the flexible board or substrate120of the folded stacked package110twice at the first and second folding units124aand124b, the folded stacked package110illustrated inFIG. 2Bmay be obtained.

Referring toFIG. 3A, a first flexible layer120ais prepared. As an example, the first flexible layer120amay be formed of a cured or half-cured polymer, e.g., polyimide. In this example, the first flexible layer120amay be bonded later in subsequent processes to a second flexible layer120bthrough thermal lamination, thereby completing the formation of the flexible board or substrate120. As another example, the first flexible layer120amay be formed of a rigid material on a carrier, in which case, the carrier may be detached later in subsequent processes from the flexible board or substrate120. The first flexible layer120amay be divided into the first device packaging unit122a, the first folding unit124a, the second device packaging unit122b, the second folding unit124b, and the third device packaging unit122c. According to an exemplary embodiment no physical boundaries between the first device packaging unit122a, the first folding unit124a, the second device packaging unit122b, the second folding unit124b, and the third device packaging unit122care necessary.

Referring toFIG. 3B, the first, second, and third active devices132a,132b, and132care mounted on the first flexible layer120a, and more particularly, on the first, second, and third device packaging units122a,122b, and122c, respectively. The active devices132may be attached onto the first flexible layer120ausing a predetermined bonding unit (not shown). The connection pads134may be formed on the active devices132such that they can face the wiring patterns142or the passive devices146later in subsequent processes. There is nearly no limit to the type of bonding unit used to attach the active devices132onto the first flexible layer120a.

Referring toFIG. 3C, the second flexible layer120bis formed on the first flexible layer120aillustrated inFIG. 3B, i.e., the first flexible layer120aon which the active devices132are attached. The second flexible layer120bmay be formed of the same material as that of the first flexible layer120a. For example, the second flexible layer120b, like the first flexible layer120a, may be formed of a half-cured polymer. In this example, the first and second flexible layer120aand120bmay be cured by being heated and then cooled. As a result, the first and second flexible layers120aand120bmay be incorporated into a single flexible layer, thereby completing the formation of the flexible board or substrate120.

Referring toFIG. 3D, via holes h, which expose the connection pads134of the active devices132, are formed in the flexible board or substrate120. There are no restrictions on how to form the vial holes h. For example, the via holes h may be formed by partially etching the flexible board or substrate120using photolithography or by drilling holes into the flexible board or substrate120using plasma or laser.

Referring toFIG. 3E, a conductive material may be formed in the flexible board or substrate120illustrated inFIG. 3D. For example, the vias144, which fill the via holes h, may be formed by depositing a conductive material on the flexible board or substrate120. The wiring patterns142may be formed by depositing a conductive material on the flexible board or substrate120. Some of the wiring patterns142may be connected to the vias144. There are no restrictions on how to form the vias144and the wiring patterns142. For example, the vias144and the wiring patterns142may be formed by forming a seed layer through sputtering or electroless plating and continuously performing electrolytic plating on the seed layer.

The passive devices146may be mounted on the flexible board or substrate120illustrated inFIG. 3E, as illustrated inFIGS. 2A and 2B. As an example, the passive devices146may be mounted on the flexible board or substrate120such that they can be electrically connected to the wiring patterns142. One or more passive devices146may be mounted on each of the first and second device packaging units122aand122b. The passive devices146may be mounted on the flexible board or substrate120in such a manner that the first passive devices146amounted on the first device packaging unit122aand the second passive devices146bmounted on the second device packaging unit122bdo not overlap each other when the flexible board or substrate120is folded.

In response to the passive devices146all being mounted on the flexible board or substrate120, the first and second bonding units152aand152bmay be disposed on the flexible board or substrate120, and the flexible board or substrate120may be folded twice at the first and second folding units124aand124b, thereby completing the manufacture of the folded stacked package110. Referring toFIG. 2B, the first bonding unit152amay be placed in the space between the first and second device packaging units122aand122b, and the second bonding unit152bmay be placed in the space between the second and third device packaging units122band122c.

As described above, since, in a folded stacked package, passive devices are directly disposed above wiring patterns formed at the time of embedding active devices, no PTHs are necessary for electrically connecting the passive devices and the active devices. Therefore, it is possible to improve the packaging density of a folded stacked package and prevent the electrical properties of a folded stacked package from deteriorating due to parasitic inductance or parasitic resistance. In addition, since the active devices are all embedded, it is possible to manufacture a thin folded stacked package.