Die package structure and method of manufacturing the same
By aligning and folding the hollow pads of the flexible printed circuit board with the die pads, the problems of large package size, high cost and insufficient signal test points are solved, thus providing signal test points and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- REALTEK SEMICON CORP
- Filing Date
- 2022-01-20
- Publication Date
- 2026-07-03
AI Technical Summary
In existing technologies, multi-die packaging methods suffer from problems such as large package size, high cost, ineffective signal interconnection, and insufficient test points, which are particularly prominent in high-speed signal transmission.
Using a flexible printed circuit board, the hollowed-out pads are aligned and soldered with the die pads. Combined with a folding design, signal test points are provided and the package structure size is reduced, thus lowering costs.
This approach achieves the goal of reducing the size of the package structure while providing signal test points and lowering costs.
Smart Images
Figure CN116525547B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a packaging structure and its manufacturing method, and more particularly to a die packaging structure and its manufacturing method. Background Technology
[0002] Placing multiple dies in the same package is a common packaging method. However, this method has drawbacks, including larger package size, higher cost, and the inability to measure signals on the dies.
[0003] When multiple chips are used in a package structure, and the electrical signals on the chips need to be interconnected, pads are usually provided on top of the chips to facilitate interconnection. There are generally two types of packaging methods:
[0004] The first approach involves placing the two chips horizontally within the package structure, with the pads interconnected via metal lines (e.g., copper wires). However, the different order of the interconnection of the two chips' pads can cause the metal lines to cross, increasing the risk of short circuits.
[0005] To avoid metal trace crossings, a metal layer needs to be placed on one of the dies. Traces are then routed within this metal layer to alter the position and order of the pads on the die, facilitating cross-crossing interconnects. However, this approach results in a larger package size and requires an additional metal layer on the die, increasing costs. Furthermore, when transmitting high-speed signals (rates exceeding 1 Gbps) through the interconnection between the two dies, the limited space within the metal layer and the inability to design branches for high-speed signals limit the number of signal test points.
[0006] Another approach is to stack the two dies. However, this approach is limited by the fact that the metal layer on the die can only provide one trace layer. When multiple pads are needed for interconnection, the area of the metal layer needs to be increased, resulting in the die above the stack being suspended. An additional dummy die layer is then needed to fill the gap. Although this can reduce the size of the package structure, it still cannot effectively solve the disadvantages of the first approach, such as the inability to increase signal test points and the increased cost. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to provide a die packaging structure and its manufacturing method in order to address the shortcomings of the prior art.
[0008] To address the aforementioned technical problems, one of the technical solutions adopted by this invention is to provide a method for fabricating a die-package structure, comprising: fixing a first die on a package base; placing a flexible printed circuit board (PCB) above the first die, aligning a plurality of first perforated pads of the PCB with a plurality of first pads of the first die; fixing the PCB above the first die; soldering the plurality of first perforated pads to the plurality of first pads; fixing a second die on the PCB and overlapping the first die; folding the PCB so that a plurality of second perforated pads of the PCB are aligned with a plurality of second pads of the second die, exposing a plurality of signal test pads of the PCB, wherein the plurality of second perforated pads are electrically connected to the plurality of first perforated pads; fixing the PCB on the second die; soldering the plurality of second perforated pads to the plurality of second pads; soldering a plurality of metal wires to the plurality of signal test pads; and soldering a plurality of package pins to the plurality of metal wires.
[0009] To address the aforementioned technical problems, another technical solution adopted by the present invention is to provide a die-package structure, comprising a package base, a first die, a flexible printed circuit board (PCB), a second die, multiple metal lines, and multiple package pins. The first die is disposed on the package base. The flexible printed circuit board has a first portion and a second portion. The first portion is disposed above the first die, and multiple first perforated pads of the flexible printed circuit board are aligned with and soldered to the multiple first pads of the first die. The second die is disposed on the first portion of the flexible printed circuit board and overlaps with the first die. The flexible printed circuit board is folded so that the second portion is disposed above the second die, and multiple second perforated pads of the flexible printed circuit board are aligned with and soldered to the multiple second pads of the second die, exposing multiple signal test pads of the flexible printed circuit board. The multiple second perforated pads are electrically connected to the multiple first perforated pads. Multiple metal lines are respectively connected to the multiple signal test pads. Multiple package pins are respectively connected to the multiple metal lines.
[0010] One of the beneficial effects of the present invention is that the die packaging structure and its manufacturing method provided by the present invention use a flexible printed circuit board with multiple hollowed-out pads with appropriate configuration. After folding, signal test points can be provided on the electrical path of the two dies, and the packaging structure volume can be reduced, and the cost can also be reduced.
[0011] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description
[0012] Figure 1 This is a flowchart illustrating a method for fabricating a die-packaging structure according to an embodiment of the present invention.
[0013] Figure 2 This is a top view of step S10 of an embodiment of the present invention.
[0014] Figure 3A This is a top view of step S11 of an embodiment of the present invention.
[0015] Figure 3B This is a cross-sectional schematic diagram of step S11 according to an embodiment of the present invention.
[0016] Figure 4A This is a top view schematic diagram of a flexible printed circuit board according to an embodiment of the present invention.
[0017] Figure 4B This is a cross-sectional schematic diagram of a flexible printed circuit board according to an embodiment of the present invention.
[0018] Figure 5 This is a top view of step S13 of an embodiment of the present invention.
[0019] Figure 6A This is a top view of step S14 of an embodiment of the present invention.
[0020] Figure 6B This is a cross-sectional schematic diagram of step S14 of an embodiment of the present invention.
[0021] Figure 7 This is a top view of steps S17 and S18 of an embodiment of the present invention.
[0022] Figure 8 This is a cross-sectional schematic diagram of step S19 of an embodiment of the present invention. Detailed Implementation
[0023] The following specific embodiments illustrate the implementation of the "die packaging structure and its fabrication method" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. Furthermore, the accompanying drawings of this invention are for simple illustrative purposes only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention. In addition, the term "or" used herein may, depending on the actual situation, include any combination of any one or more of the associated listed items.
[0024] Figure 1 This is a flowchart illustrating a method for fabricating a die-packaging structure according to an embodiment of the present invention. (See attached document.) Figure 1 As shown, an embodiment of the present invention provides a method for fabricating a die-packaged structure, which includes the following steps:
[0025] Step S10: Secure the first die to the packaging substrate. (See also...) Figure 2 This is a top view schematic diagram of step S10 of an embodiment of the present invention. Figure 2 In this design, the first die 10 can be, for example, a bare die, which is a small, unpackaged integrated circuit body made of semiconductor material. It has multiple first pads, such as first pads 101, 102, and 103, for signal transmission between the first die 10 and external components. The first die 10 is fixed to the package base 12 using a conventional die-attachment process, such as by applying adhesive, heat, pressure, or ultrasound. The package base 12 can be, for example, a square frame structure integrated circuit base, which typically has multiple holes on its edges for mounting electrical pins.
[0026] Step S11: Place the flexible printed circuit board above the first die, align the multiple first hollow pads of the flexible printed circuit board with the multiple first pads of the first die, and fix the flexible printed circuit board.
[0027] You can refer to them together. Figure 3A , Figure 3B , Figure 4A and Figure 4B . Figure 3A This is a top view of step S11 according to an embodiment of the present invention. Figure 3B This is a cross-sectional schematic diagram of step S11 according to an embodiment of the present invention. Figure 4A This is a top view schematic diagram of a flexible printed circuit board according to an embodiment of the present invention. Figure 4B This is a cross-sectional schematic diagram of a flexible printed circuit board according to an embodiment of the present invention.
[0028] You can refer to this first. Figure 4A and Figure 4B The flexible printed circuit board 14 has a first surface S1 that contacts the first die 10 and a second surface S2 that is opposite to the first surface S1. The flexible printed circuit board 14 may include, for example, a copper foil substrate, a core layer (e.g., polyimide) and a protective film for surface insulation.
[0029] like Figure 4A And along the section line AA Figure 4BAs shown in the cross-sectional view, the flexible printed circuit board 14 has a plurality of first cutout pads (e.g., first cutout pads 141, 142, 143) and a plurality of second cutout pads (e.g., second cutout pads 144, 145, 146), wherein the first cutout pads 141, 142, 143 are disposed in the flexible printed circuit board 14 through the first surface S1 and the second surface S2.
[0030] from Figure 4A From the top view, the first cutout pads 141, 142, and 143 each include a first rectangular loop shape of metal, the inner circle of which is smaller than the size of the corresponding first pad, and the outer circle of which is larger than the size of the corresponding first pad. For example, the first cutout pad 141 is aligned with the first pad 101, and the area of its inner circle, that is, the area of the cutout portion, is smaller than the area of the first pad 101, while the area of its outer circle (the rectangle formed by the outer edge) is larger than the area of the first pad 101.
[0031] On the other hand, the second cutout pads 144, 145, and 146 are electrically connected to the first cutout pads 141, 143, and 142, respectively. Similarly, the second cutout pads 144, 145, and 146 are disposed in the flexible printed circuit board 14 through the first surface S1 and the second surface S2, and are electrically connected to the first cutout pads 141, 143, and 142 through multiple metal traces 147-1, 147-2, 147-3, 147-4, 147-5, and 147-6 in the flexible printed circuit board 14, respectively.
[0032] In some embodiments, although the second cutout pads 144, 145, and 146 correspond sequentially to the first cutout pads 141, 142, and 143 in a specific direction, in order to meet circuit design requirements, the second cutout pads 144, 145, and 146 need to be electrically connected to the first cutout pads 141, 143, and 142 in sequence, so that the first pads 101, 102, and 103 on the first die 10 can be connected to specific pads.
[0033] Furthermore, metal traces 147-1, 147-2, and 147-3 are the top-layer metal traces in the flexible printed circuit board 14, while metal traces 147-4, 147-5, and 147-6 are the bottom-layer metal traces in the flexible printed circuit board 14. Metal trace 147-1 is electrically connected to metal trace 147-4 via via V1, metal trace 147-2 is electrically connected to metal trace 147-6 via via V2, and metal trace 147-3 is electrically connected to metal trace 147-5 via via V3. This method avoids the need for additional metal layers to provide signal paths. When there are many signal lines, the flexible printed circuit board 14 can have four or six or more metal planes for signal connections. In other words, the metal traces 147-1, 147-2, and 147-3 mentioned above are not limited to the top metal traces, and the metal traces 147-4, 147-5, and 147-6 are not limited to the bottom metal traces. That is to say, all metal planes in the flexible printed circuit board 14 can be used for signal connection.
[0034] Furthermore, signal test pads T1, T2, and T3 are located on the electrical paths formed by metal traces 147-4, 147-5, and 147-6, respectively, and on the first surface S1 of the flexible printed circuit board 14. It should be noted that on the first surface S1, a protective layer typically covers the metal traces 147-4, 147-5, and 147-6 for insulation protection, while the protective layer may retain multiple exposed areas for the signal test pads T1, T2, and T3 to be electrically connected to the metal traces 147-4, 147-5, and 147-6, respectively.
[0035] Next, you can refer to Figure 3A The top view and the view drawn along section line BB Figure 3B A cross-sectional view. For example... Figure 3A , Figure 3B As shown, when a portion (first portion) of the flexible printed circuit board 14 is disposed above the first die 10, the first pads 101, 102, and 103 are aligned with the first cutout pads 141, 142, and 143, respectively.
[0036] Step S12: Solder the plurality of first cutout pads to the plurality of first pads.
[0037] For reference Figure 3BSolder can be poured into the cutouts of the first cutout pads 141, 142, and 143, and then soldered to the first pads 101, 102, and 103 respectively using a soldering process. Alternatively, any method can be used to electrically connect the first cutout pads 141, 142, and 143 to the first pads 101, 102, and 103; the invention is not limited thereto. Because the inner ring size of the first ring-shaped metal is smaller than the size of the corresponding first pad, and its outer ring size is larger than the size of the corresponding first pad, good electrical contact between the first cutout pads 141, 142, and 143 and the first pads 101, 102, and 103 can be ensured after soldering, thus reducing the probability of soldering failure.
[0038] Step S13: Fix the second die on the flexible printed circuit board and overlap it with the first die.
[0039] Please refer to Figure 5 This is a top view schematic diagram of step S13 of an embodiment of the present invention. Figure 5 As shown, a fixing material, such as epoxy molding compound, can be applied over the flexible printed circuit board 14 to fix the second die 16 onto the second surface S2 of the flexible printed circuit board 14. Similar to the first die 10, the second die 16 can be, for example, a bare die, which is a small, unpackaged integrated circuit body made of semiconductor material, with multiple second pads, such as second pads 161, 162, and 163, for signal transmission between the second die 16 and the first die 10 or external components. It should be noted that... Figure 5 The positions of the second pads 161, 162, and 163 are for illustrative purposes only and are not limited to being located on the far left of the second die 16. From the top view, the vertical projection areas of the second die 16 and the first die 10 overlap, and because of this overlap, the overall usable area of the package structure can be reduced.
[0040] Step S14: Fold the flexible printed circuit board to form a folded portion, so that the plurality of second cutout pads of the flexible printed circuit board are aligned with the plurality of second pads of the second die, and expose the plurality of signal test pads of the flexible printed circuit board.
[0041] Please refer to this as well. Figure 5 , Figure 6A and Figure 6B , Figure 6A This is a top view of step S14 according to an embodiment of the present invention. Figure 6B This is a cross-sectional schematic diagram of step S14 of an embodiment of the present invention.
[0042] like Figure 5As shown, similar to the first cutout pads 141, 142, and 143, the second cutout pads 144, 145, and 146 each include a second ring-shaped metal element, the inner circle of which is smaller than the size of the corresponding second pad, and the outer circle of which is larger than the size of the corresponding second pad. For example, the second cutout pad 144 will be aligned with the second pad 161, and the area of its inner circle, that is, the area of the cutout portion, is smaller than the area of the second pad 161, while the area of its outer circle (the rectangle formed by the outer edges) is larger than the area of the first pad 161.
[0043] Next, refer to Figure 6A and drawn along the cross section line CC Figure 6B , when along Figure 5 When the fold line FL folds the right side (second part) of the flexible printed circuit board 14 to the left and aligns the second cutout pads 144, 145, 146 with the second pads 161, 162, 163, the signal test pads T1, T2, T3 on the first surface S1 will be exposed at the top. In other words, even if the first pads 101, 102, 103 and the second pads 161, 162, 163 are all covered by design requirements, signals can still be tested through the signal test pads T1, T2, T3 without the need to set up additional test lines for the first pads 101, 102, 103 and the second pads 161, 162, 163.
[0044] It should be noted that the positions of the signal test pads T1, T2, and T3 can be adjusted according to the actual application. For example, when more than two dies are stacked, if the test pads T1, T2, and T3 are directly above one of the dies, they may be blocked by the die above them. Therefore, the signal test pads T1, T2, and T3 can be set at the fold line FL of the flexible printed circuit board 14, that is, on the side of the entire die stack. Figure 6B The positions correspond to the first cutout pads 141 and 142. Its advantage is that even if multiple dies are stacked, the signal test pads T1, T2, and T3 can still be brought out through metal lines on the side of the die stack for testing.
[0045] Step S15: Fix the folded portion of the flexible printed circuit board onto the second die.
[0046] In detail, this step fixes the portion of the flexible printed circuit board 14 above the second die 16 onto the second die 16, for example, by applying adhesive, heat, pressure or ultrasound to fix the flexible printed circuit board 14 onto the second die 16.
[0047] Step S16: Solder the plurality of second cutout pads to the plurality of second pads.
[0048] For reference Figure 6B Solder can be poured into the cutouts of the second cutout pads 144, 145, and 146, and then soldered to the second pads 161, 162, and 163 respectively using a soldering process. Alternatively, any method can be used to electrically connect the second cutout pads 144, 145, and 146 to the second pads 161, 162, and 163; the invention is not limited thereto. Because the inner ring size of the second ring-shaped metal is smaller than the size of the corresponding second pad, and its outer ring size is larger than the size of the corresponding second pad, good electrical contact between the second cutout pads 144, 145, and 146 and the second pads 161, 162, and 163 can be ensured after soldering, thus reducing the probability of soldering failure.
[0049] Step S17: Solder multiple metal wires to the multiple signal test pads.
[0050] Step S18: Solder the multiple package pins to the multiple metal wires.
[0051] Please refer to Figure 7 This is a top view schematic diagram of steps S17 and S18 of an embodiment of the present invention. For example, metal lines M1, M2, and M3 can be respectively arranged outward from the signal test pads T1, T2, and T3 by wire bonding, and the package pins P1, P2, and P3 can be soldered to the metal lines M1, M2, and M3 respectively. The metal lines M1, M2, and M3 can be, for example, copper wires, but the present invention is not limited thereto. In specific test applications, the metal lines M1, M2, and M3 can also be soldered to the package pins P1, P2, and P3, or the metal lines M1, M2, and M3 can be directly extended outside the package for signal testing.
[0052] Therefore, the present invention also provides a die packaging structure 1, which has been developed by... Figure 1 The process is formed and illustrated in Figure 7 The package includes a packaging base 12, a first die 10, a second die 16, and a flexible printed circuit board 14. The arrangement of the packaging base 12, the first die 10, the second die 16, and the flexible printed circuit board 14 has been described above and will not be repeated here. It should be noted that the die packaging structure and its manufacturing method of the present invention are not limited to two dies, but can also be applied to multi-die stacking.
[0053] Please return to the reference. Figure 1 Users can continue to stack similar architectures upwards as needed, or refer to [the existing architecture]. Figure 8 This is a cross-sectional schematic diagram of step S19 of an embodiment of the present invention. The method for fabricating the die-package structure proceeds to step S19: covering the package base, the first die, the second die, and the flexible printed circuit board with a package cover. For example... Figure 8As shown, the encapsulation cover 2 has an accommodating space that can enclose the die encapsulation structure 1 and is combined with the encapsulation base 12.
[0054] Beneficial effects of the embodiments:
[0055] One of the beneficial effects of the present invention is that the die packaging structure and its manufacturing method provided by the present invention use a flexible printed circuit board with multiple hollowed-out pads with appropriate configuration. After folding, signal test points can be provided on the electrical path of the two dies, and the packaging structure volume can be reduced, and the cost can also be reduced.
[0056] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included in the scope of the patent application of the present invention.
[0057] Explanation of reference numerals in the attached figures:
[0058] 1: Die-to-die packaging structure
[0059] 2: Encapsulation cover
[0060] 10: First grain
[0061] 12: Packaging base
[0062] 14: Flexible Printed Circuit Board
[0063] 16: Second grain
[0064] 101, 102, 103: First pad
[0065] 141, 142, 143: First cutout pad
[0066] 144, 145, 146: Second hollow pads
[0067] 147-1, 147-2, 147-3, 147-4, 147-5, 147-6: Metallic traces
[0068] 161, 162, 163: Second pad
[0069] AA, BB, CC: Cross-section lines
[0070] FL: Broken line
[0071] M1, M2, M3: Metal wire
[0072] P1, P2, P3: Package pins
[0073] S1: First Page
[0074] S2: Second side
[0075] T1, T2, T3: Signal test pads
[0076] V1, V2, V3: Through holes
Claims
1. A method for fabricating a die-packaged structure, comprising: The first die is fixed on the packaging base; A flexible printed circuit board is placed above the first die, so that the multiple first hollow pads of the flexible printed circuit board are aligned with the multiple first pads of the first die, and the flexible printed circuit board is fixed. Solder the plurality of first hollow pads to the plurality of first pads; The second die is fixed on the flexible printed circuit board and overlaps with the first die; The flexible printed circuit board is folded to form a folded portion, so that a plurality of second cutout pads of the flexible printed circuit board are aligned with a plurality of second pads of the second die, and a plurality of signal test pads of the flexible printed circuit board are exposed, wherein the plurality of second cutout pads are electrically connected to the plurality of first cutout pads respectively. The folded portion of the flexible printed circuit board is fixed to the second die; Solder the plurality of second cutout pads to the plurality of second pads; Solder multiple metal wires to the multiple signal test pads; and Multiple package pins are soldered to these multiple metal lines.
2. The method for fabricating the die-packaging structure as described in claim 1, wherein, The flexible printed circuit board has a first side that contacts the first die and a second side that is opposite to the first side, and a plurality of first hollow pads are disposed in the flexible printed circuit board through the first side and the second side.
3. The method for fabricating the die-packaging structure as described in claim 2, wherein, The step of fixing the second die on the flexible printed circuit board further includes fixing the second die on the second surface of the flexible printed circuit board, and overlapping the vertical projection area of the first die on the flexible printed circuit board.
4. The method for fabricating the die-packaging structure as described in claim 2, wherein, The step of folding the flexible printed circuit board further includes folding the flexible printed circuit board to expose the plurality of signal test pads located on the first surface.
5. The method for fabricating the die-packaging structure as described in claim 2, wherein, The plurality of second hollow pads penetrate the first surface and the second surface and are disposed in the flexible printed circuit board. They are electrically connected to the plurality of first hollow pads through the plurality of metal traces in the flexible printed circuit board, and the plurality of signal test pads are respectively located on the plurality of electrical paths formed by the plurality of metal traces.
6. The method for fabricating the die-packaging structure as described in claim 1, wherein, The step of fixing the flexible printed circuit board onto the second die further includes fixing the portion of the flexible printed circuit board located above the second die onto the second die.
7. The method for fabricating the die-packaging structure as described in claim 2, wherein, Each of the plurality of first hollow pads includes a first ring-shaped metal, the inner circle of which is smaller than the size of the corresponding first pad, and the outer circle of which is larger than the size of the corresponding first pad.
8. The method for fabricating the die-packaging structure as described in claim 2, wherein, Each of the plurality of second hollow pads includes a second ring-shaped metal, the inner circle of which is smaller than the size of the corresponding second pad, and the outer circle of which is larger than the size of the corresponding second pad.
9. A die-package structure, comprising: Packaging base; The first die is disposed on the packaging base; A flexible printed circuit board has a first part and a second part. The first part is disposed above the first die, and a plurality of first hollow pads of the flexible printed circuit board are aligned with and soldered to a plurality of first pads of the first die. The second die is disposed on the first portion of the flexible printed circuit board and overlaps with the first die. The flexible printed circuit board is folded so that the second portion is disposed above the second die. The multiple second cutout pads of the flexible printed circuit board are aligned with and soldered to the multiple second pads of the second die, and the multiple signal test pads of the flexible printed circuit board are exposed. The multiple second cutout pads are electrically connected to the multiple first cutout pads respectively. Multiple metal wires are connected to the multiple signal test pads, respectively; and Multiple package pins are connected to the multiple metal lines respectively.
10. The die packaging structure as described in claim 9, wherein, The flexible printed circuit board has a first side that contacts the first die and a second side that is opposite to the first side, and a plurality of first hollow pads are disposed in the flexible printed circuit board through the first side and the second side.