Zigzag-stacked package structure

A die-stacked package structure, wherein a plurality of dies are stacked on the substrate with a rotation so that a plurality of metallic ends and the metal pad on each die on the substrate can all be exposed; a plurality of metal wires are provided for electrically connecting the plurality of metal pads on the plurality of dies with the plurality metallic ends on the substrate in one wire bonding process; then an encapsulate is provided for covering the plurality of stacked dies, a plurality of metal wires and the plurality of metallic ends on the substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is a multi-dies stacked package structure, more particularly; it is a zigzag-stacked package structure.

2. Description of the Prior Art

In recent years, the semiconductor package process is using three-dimension (3D) package method to have relative large integrated semiconductor or the volume of the memory in the less measure of area. In order to achieve this object, the die stacked method is used to have 3D package structure.

In the prior art, the stacked structures of the dies are formed by stacking a plurality of dies one another and on a substrate and wire bonding the dies and the substrate for electrical connection.FIG. 1ais a sectional view showing a zigzag-stacked package structure with the dies of a similar size in the prior art. As shown inFIG. 1a, the zigzag-stacked package structure100includes a circuit substrate110, dies120aand120b, a spacer130, a plurality of wires140and an encapsulated material150. The circuit substrate110includes a plurality of pads and the die120aand die120brespectively includes a plurality of pads122aand122b. The pads122aand122bare arranged around the periphery areas of the die120aand120brespectively. The die120ais disposed on the circuit substrate110and the die120bis disposed on top of the die120awith the spacer130placed therebetween. The wires140connect the pads112on the circuit substrate110with the pads122aand122bby wire bonding process and the dies120aand120bare then electrically connected to the circuit substrate110. The encapsulated material150is formed on the circuit substrate110to cover the wires140, the dies120aand120b.

Because the pads122aand122bare arranged on the periphery areas of the dies120aand120b, the die120ais not able to directly support the die120b. So, in the package process, after the die120ais connected to the circuit substrate110, the pads122aon the die120aare connected to the pads112on the circuit substrate110by a wire bonding process. The spacer130is then connected to the die120aand the die120bis connected on the spacer130. The pads122bon the die120bare connected to the pads112on the circuit substrate110by another wire bonding process. Obviously, the spacer130is disposed between the die120aand120bto provide a distance between the die120aand120bfor the wires140. However, the usage of the spacer130causes the difficulty to reduce the thickness of the zigzag-stacked package structure100.

Besides, another zigzag-stacked package structure with different die sizes is provided in prior art, as the sectional view shown inFIG. 1B. The zigzag-stacked package structure10includes a circuit substrate110, die120c, die120d, a plurality of wires140and an encapsulated material150. The circuit substrate110includes a plurality of pads112. The size of the die120cis bigger than the size of the die120d.The dies120cand120drespectively include a plurality of pads122cand122d.The pads122cand122dare arranged on the periphery areas of the dies120cand120d. The die120cis disposed on the circuit substrate110and the die120dis disposed on the die120c. The wires140connect the pads112with the pads122cby wire bonding process and the die120cis then electrically connected to the circuit substrate110. The wires140connect the pads112with the pads122dby wire bonding process and the die120dis then electrically connected to the circuit substrate110. The encapsulated material150is formed on the circuit substrate110to cover the wires140, the dies120cand120d.

Because the die120dis smaller than the die120c, the die120ddoes not completely cover the die120cwhen the die120dis disposed on the die120c. Therefore, the package process is different to the process inFIG. 1A. Both of the dies120cand120dare mounted on the substrate110first and then a one-time wire bonding process is then executed. When the dies with different sizes are stacked together to form a zigzag-stacked package structure in prior art, the sizes of the dies on top should be gradually smaller; therefore, the number of the dies to be stacked is limited.

According to the two stacked structures described above, the design and the usage of the dies are limited. According to the problems above, U.S. Pat. Nos. 6,252,305, 6,359,340 and 6,461,897 provide another zigzag-stacked package structure, as shown inFIG. 1C. Obviously, the package structure uses the dies with the same size but no spacer130to separate the dies. However, during the stacking steps, the dies are stacked to each other by using at least two types of pad arrangement. For example, the pads on the first dies are disposed on one side of the first dies and the pads on the second dies are disposed on two adjacent sides. Besides, the package structure needs the wire bonding process to be executed in two directions. Therefore, as the structure shown inFIG. 1C, it would increase the time of wire bonding process and it would cause asymmetrical molding flow during the molding process. The wire in one direction may be hit by the transversal molding strength causing the contact of the wires and further the malfunction of the dies.

Besides, U.S. Pat. No. 6,900,528, U.S. Pat. No. 20030137042A1, U.S. Pat. No. 20050029645A1and U.S. Pat. No. 20060267173A1disclosed another zigzag-stacked package structure. Obviously, the height between the dies is used to replace the spacer to increase the density of the package structure. However, there are some problems in the manufacture of the package structure. After two dies are connected together, the first wire bonding process shall be proceeded before another dies can be stacked upon. When the number of dies is increased, the package process become more time-consuming and more complicated.

SUMMARY OF THE INVENTION

According to the drawbacks and the problems of prior art described above, a zigzag-stacked package structure is provided in the present invention for stacking of the dies with similar size in a three-dimension package structure.

The main object of the present invention is to provide a zigzag-stacked package structure with higher package density and thinner thickness.

Another object of the present invention is to provide a zigzag-stacked package structure with balanced molding effect during the molding process.

Another object of the present invention is to provide a zigzag-stacked package structure including a bus bar to have better flexibility of circuit design and higher reliability.

According to the objects described above, the present invention provides a zigzag-stacked package structure. The zigzag-stacked package structure includes a lead frame, a zigzag-stacked structure and an encapsulated material. The lead frame includes a plurality of inner leads, a plurality of outer leads and a die paddle, wherein the die paddle is disposed between the inner leads and a height difference formed between the die paddle and the inner leads. The zigzag-stacked structure is connected on the die paddle and the zigzag-stacked structure includes a plurality of first dies and a plurality of second dies, each of the first dies and the second dies having an active surface and a back surface opposite to the active surface, a first periphery region and a second periphery region opposite to the first periphery region defined upon each of the active surfaces, each of the first dies and each of the second dies alternately stacked to each other with the back surface attached to the active surface and forming a stacked area, and the first dies and the second dies are electrically connected to the inner leads. The encapsulated material covers the zigzag-stacked structure and the lead frame, and the outer leads are extended over the encapsulated material. Each of the first dies having a plurality of pads disposed on the first periphery region and each of the second dies having a plurality of pads disposed on the second periphery region, each of the pads is exposed and unshadowed.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The detailed description of the present invention will be discussed in the following embodiments, which are not intended to limit the scope of the present invention, but can be adapted for other applications. While drawings are illustrated in details, it is appreciated that the quantity of the disclosed components may be greater or less than that disclosed, except expressly restricting the amount of the components.

The semiconductor package structure in these years is to package a wafer in front end process to do the thinning execution. The thinning process is to grind the die with the size between 2 ˜20 mils and then do the process of coating or printing a polymer on the back surface of the die. The material of polymer is a resin, such as a B-Stage resin. After a baking or photo-lighting process, the polymer becomes a sticky adhesive. After the baking process, a removable tape is stuck on the polymer. A singulation process is performed to cut the wafer into a plurality of dies. Each of the individual dies can then be vertically stacked together and as a whole connected to the substrate to form a chip stacked package.

First, please refer toFIG. 2AtoFIG. 2D.FIGS. 2A,2C andFIGS. 2B,2D are plan views and sectional views of dies200and20respectively shown in previous description. As shown inFIG. 2AtoFIG. 2D, each of the die200,20includes an active surface210and a back surface220opposite to the active surface210. There is an adhesive layer230formed on the back surface220of the die200.

The adhesive layer230is used to attach the lead frame and the dies200and20. Therefore, any adhesive material which can meet the purpose, such as die attached film, is included in the present invention. Besides, in the embodiment of the present invention, there are a plurality of pads240disposed on a periphery region250of the active surfaces210of the dies200and20When the die200is stacked on the die20, they are arranged to have the pads240of the die20and the pads240of the die200to locate on two opposite sides and to form a stacked area, as shown inFIG. 2E. Therefore, a zigzag-stacked structure30can then be formed by alternately stacking each of the dies200and20Before the zigzag-stacked structure30is formed in the present invention, the stacked areas between the dies are determined based on the number of the dies to be stacked. For example, the two dies20aand200aon the bottom layer are connected to each other by the adhesive layer230, the dimension of the stacked area formed by the die20aand the die200ais larger than a half of the dimension of the dies20aand200a, and the dimension of the stacked area formed by the20band the die200ais larger than that of the stacked area formed by the die200aand the die20a, so that the stacked areas formed by the dies20a,200a,20b,200b,20c,200c,20dand200drespectively are upwardly increasing Therefore, a step-like die stacked structure is formed and each of the pads240disposed on the dies20a,200a,20b,200b,20c,200c,20dand200dare unshadowed by any of the top dies. In an embodiment, the size of the dies20and200is about 10 mm * 13 mm * 75 um and the thickness of the adhesive layer230on the back surface of the die is about 60 um. The thickness of the substrate used to support the zigzag-stacked structure is about 200 um˜250 um. According to the size of the dies20and200, the biggest overhang width of the zigzag-stacked structure is about 1 mm for a six die stacked structure and less than 1.5 mm for an eight die stacked structure. It should be noted that the size of the dies is not limited to the above. As long as the zigzag-stacked structure is formed according to the description above is included in the present invention.

An embodiment of the present invention for a die200or a die20including a plurality of pads disposed thereon and a redistribution layer (RDL) to rearrange some of the pads of the die to one periphery region on the active surface of the die is described in the following.

FIGS. 3A ˜3Care plan views showing the manufactureing steps of the redistribution layer on the die in the present invention. As shown inFIG. 3A, a die body310is provided and a wire bonding region320is defined in one periphery region on the die body310. The pads312are disposed on the die body310and comprise a plurality of first pads312aand a plurality of second pads312b. The first pads312aare disposed within the wire bonding region320and the second pads312bare disposed outside of the wire bonding region320. Referring toFIG. 3B, there is a first protective layer330formed on the die body310and the first protective layer330includes a plurality of first openings332to expose the first pads312aand the second pads312b. Then, a redistribution layer340is formed on the first protective layer330. The redistribution layer340includes a plurality of traces342and a plurality of third pads344. The third pads344are disposed within the wire bonding region320and the traces342are extended from the second pads312bto the corresponding third pads344. The second pads312bare electrically connected to the third pads344. Besides, the material of the redistribution layer340can be gold, copper, nickel, titanium tungsten, titanium and any other conductive metals. Now referring toFIG. 3C, after forming the redistribution layer340, a second protective layer350is formed on the die body310to cover the redistribution layer340and the second pads312bto form the structure of the die300. The second protective layer350includes a plurality of second openings352to expose the first pads312aand the third pads344.

It should be noted that the first pads312aand the second pads312bare arranged on the active surface of the die body310in periphery. The first pads312aand the second pads312balso can be arranged on the active surface of the die body310in array or any other different types. The second pads312bare electrically connected to the third pads344by traces342. Besides, the arrangement of the third pads344is not limited in the present embodiment. Although the third pads and the first pads312ainFIG. 3Bare arranged in two lines and on one periphery region of the die body310. The third pads344and the first pads312acan also be arranged in single line, multiple lines or any other types within the wire bonding region320.

FIGS. 4A and 4Bare sectional views according to the sectional line A-A′ and B-B′ inFIG. 3C. As described above forFIG. 3C, the die300includes the die body310and the redistribution structure400. The redistribution structure400is composed of the first protective layer330, the redistribution layer340and the second protective layer350. The die body310includes the wire bonding region320and the wire bonding region320is defined in one periphery region of the die body310. Besides, the first pads312aare disposed within the wire bonding regions320and the second pads312bare disposed outside of the wire bonding region320.

The first protective layer330is disposed on the die body310and includes a plurality of first openings332to expose the first pads312aand the second pads312b. The redistribution layer340is disposed on the first protective layer330and extended from the second pads312bto the wire bonding regions320. The redistribution layer340includes a plurality of traces342and a plurality of third pads344disposed within the wire bonding region320. The second protective payer350is formed to cover the redistribution layer340and the second pads312band includes a plurality of second openings352to expose the first pads312aand the third pads344.

FIG. 5is a view showing a zigzag-stacked structure in the present invention. The zigzag-stacked structure50is composed by stacking a plurality of dies500. For example, there are four dies stacked to each other and each of the dies includes a redistribution structure400. Therefore, the pads312and344on the dies500are disposed in the wire bonding region320of the dies500to form the zigzag-stacked structure50. The stacking method of the zigzag-stacked structure50is the same as the zigzag-stacked structure30described above; hence, the detailed description is omitted. Besides, an adhesive layer230, such as polymer, is used to connect the dies500and form the zigzag-stacked structure.

Besides the zigzag-stacked structures30and50in the present invention described above, the dies500with the redistribution structure400can be stacked on the dies20without the redistribution structure alternately to form another kind of the zigzag-stacked structure70. As shown inFIG. 6, there are six dies stacked together. Because the stacking method of the zigzag-stacked structure70is the same as the stacked method of the zigzag-stacked structures30and50, the detailed description is omitted. Also, it should be noted that the number of dies to form the zigzag-stacked structure is not limited in the present invention. For example, there are four dies stacked together as shown inFIG. 5and there are six dies stacked together as shown inFIG. 6. It can be other kinds of compositions to form the zigzag-stacked structure by satisfying the description above in the present invention.

FIG. 7is a plan view showing the zigzag-stacked package structure in the present invention. As shown inFIG. 7, the zigzag-stacked package structure includes a lead frame600and a zigzag-stacked structure50A. The lead frame600includes a plurality of inner leads610, a plurality of outer leads (not shown) and a die paddle620. The die paddle620is disposed between the corresponding inner leads610. There is a height difference formed between the inner leads610and the die paddle620. In this embodiment, the zigzag-stacked structure50A is disposed and connected on the die paddle620by an adhesive layer230. The adhesive layer230in the present invention is a sticky adhesive as described above but not limited to. The adhesive layer230is used to connect the zigzag-stacked structure50A and the die paddle620. Therefore, any adhesive material which can meet the purpose, such as die attached film, is included in the present invention. It should be noted that, in the real package process, there are two ways to form the zigzag-stacked package structure. One is to form the stacked structure of a plurality of dies first and then connect the stacked structure to the lead frame. The other is to connect a die to the lead frame and then sequentially stack the other dies one after another. No matter what kind of the package method to form the zigzag-stacked structure50A, the wires640are used to electrically connect the zigzag-stacked structure50A to the inner leads610of the lead frame600after stacking the dies. Obviously, the zigzag-stacked package structure in the present invention is to connect the dies and the lead frame first and then do the wire bonding process to simplify the package procedure. It should be noted that the pads disposed on the dies are unshadowed by the top die in each of the zigzag-stacked structures in the present invention. Therefore, the dies are able to connect to the lead frame and then do the wire bonding process. Because the wire bonding procedure is well known by a person of ordinary skill in this art, the detailed description is omitted.

FIG. 8is a sectional view showing a zigzag-stacked package structure in the present invention (according to the sectional line AA inFIG. 7). As shown inFIG. 8, the lead frame600is connected with six dies500to form the zigzag-stacked package structure and is connected by a plurality of wires640. The lead frame600includes a plurality of corresponding inner leads610, a plurality of outer leads (not shown) and a die paddle620. The die paddle620is disposed between the corresponding inner leads610and a height difference is formed between the die paddle620and the inner leads610. One end of the wire640ais connected to the pad of the die500a. And the other end of the wire640ais connected to the pad of the die500b. Then, the wire640bconnects the pad of the die500bwith the pad of the die500c. The wire640cto then electrically connects the pad of the die500awith the corresponding inner lead610of the lead frame600. The steps described above are repeated to connect the dies500d,500eand500fby the wires640dand640e. Finally, the die500dis electrically connected to the corresponding inner leads610of the lead frame by the wire640f. Therefore, the dies500a,500b,500c,500d,500eand500fare connected to the lead frame600by the wires640a,640b,640c,640d,640eand640f. The material of the wires640is gold but not limited to. Obviously, the method to form the zigzag-stacked package structure in the present invention is to connect the dies and the lead frame first and then do the wire bonding process to simplify the package procedures.

The molding process is used to form the encapsulated material90to cover the zigzag-stacked structure50A, the inner leads610and the die paddle620of the lead frame600. The molding process is done by a mold, so the molding flow is able to flow into from the two sides of the inner leads. Since the zigzag-stacked structures30,50,50A and70are stacked in a zigzag manner, it is able to form a symmetrical structure, even though the number of dies is different, such as the zigzag-stacked structure30formed by eight dies200and20, the zigzag-stacked structure50formed by four dies500and the zigzag-stacked structure70formed by six dies. Therefore, when the molding flows into the mold, it balances the molding flow in the two sides of the inner leads. The zigzag-stacked package structure is able to have a very good reliability. Besides, by configuring the inner leads610and the die paddle620of the lead frame600in the present invention, the vertical distance (dl) between the top edge surface910of the encapsulated material90and the die500fand the vertical distance (d2) between the bottom edge of the die paddle620and the bottom edge of the encapsulated material90can be similar. When the molding process is in proceeding, the molding flow on the die500fand the bottom of the die paddle620are the same to form the balanced package structure in this embodiment.

FIG. 9is a plan view showing a zigzag-stacked package structure according to another embodiment of the present invention. As shown inFIG. 9, the zigzag-stacked package structure includes lead frame600and a zigzag-stacked structure50A. The lead frame600includes a plurality of inner leads610, a plurality of outer leads (not shown), at least one bus bar630and a die paddle620. Compared to the zigzag-stacked package structure shown inFIG. 7, the difference is that the lead frame600of the zigzag-stacked package structure in this embodiment further includes the bus bar630.

The bus bar630disposed between the die paddle620and the corresponding inner leads610. The bus bar630of the lead frame600can be at the same height as the die paddle620or the inner leads610or at a height between the die paddle620and the inner leads610. The bus bar630is formed in a bar-like arrangement or ring-like arrangement. The bus bar630is also included in prior art, and the detailed description is omitted.

FIG. 10is a sectional view of a zigzag-stacked package structure with a bus bar according to the present invention (according to the section line BB inFIG. 9). As shown inFIG. 10, the lead frame600is connected with six dies500to form the zigzag-stacked package structure and is electrically connected by a plurality of wires640. The lead frame600includes a plurality of inner leads610, a plurality of outer leads (not shown) and a die paddle620. The die paddle620is disposed between the inner leads610and a height difference is formed between the die paddle620and the inner leads610. The bus bar630is disposed between the inner lead610and the die paddle620. The dies500a,500b,500c,500d,500eand500fare connected to the lead frame600by the wires640a,640b,640c,640d,640eand640fas described inFIG. 8. The material of the wires640is gold but not limited to. Besides, the lead frame600in the embodiment includes a bus bar630and the bus bar630is at the same height as the inner lead610. Therefore, during the connection steps of the wires640, for some electrical requirements, some of the wires640are optionally connected to the bus bar630. Therefore, the bus bar630of the lead frame600can serve as a power connection, a ground or a shared signal connection. The bus bar630is useful in circuit design to provide flexibility. The bus bar630is disclosed in prior art, and the detailed description is omitted.

At last, the encapsulated material90is formed by the molding process described inFIG. 8. The vertical distance (d1) between the top edge surface910of the encapsulated material90and the die500f and the vertical distance (d2) between the bottom edge of the die paddle620and the bottom edge of the encapsulated material90are the same. During the molding process, the molding flow on the die500f and the bottom edge of the die paddle620are almost the same to form the balanced package structure in this embodiment.

FIG. 11is a plan view showing another embodiment showing a zigzag-stacked package structure of the present invention. As shown inFIG. 11, the zigzag-stacked package structure includes a substrate800and the zigzag-stacked structure70. The substrate800is used to support the zigzag-stacked structure (30,50,50A or70). The wires640are used to electrically connect the zigzag-stacked structure70to the metal ends810on the substrate800for further external connection. The adhesive material230described above is also used to attach the zigzag-stacked structure70and the substrate800. The substrate800is a printed circuit board (PCB), ceramic substrate or a substrate with a core layer made by BT resin or FR-4 resin. Besides, in order to connect to the external components, the reverse surface of the substrate800opposite to the surface with the zigzag-stacked structure70mounted on also includes the metal ends810disposed thereon and electrically connected to the metal ends810on the surface with the zigzag-stacked structure70mounted on by redistribution layer (RDL) or through-hole process. The solder balls can be attached to metal ends810on the reverse surface as the external connections of the package structure, such as a ball grid array (BGA) package structure. Obviously, the pads on the dies unshadowed by any of the dies on top in the zigzag-stacked package structure of the present invention. After all the dies are mounted on the substrate800, the wire bonding process is then executed so as to simplify the package procedures.

FIG. 12is a section view showing a zigzag-stacked package structure of the present invention (according to the sectional line CC inFIG. 11). As shown inFIG. 12, a plurality of the wires640are used to connect the substrate800and the zigzag-stacked structure70. The wires640are used to electrically connect the dies500and20of the zigzag-stacked structure70to the metal ends810on the substrate800. The material of the wires640is gold but not limited to. The encapsulated material90is formed to cover the zigzag-stacked structure70, the wires640and the substrate800.