Pin-bent QFN package structure and manufacturing method thereof

Abstract

The present invention provides a pin-bending QFN package structure and a manufacturing method thereof, wherein the package structure comprises a lead frame, at least one chip and a plastic encapsulation layer, wherein the lead frame comprises at least one base island and a plurality of pins located on the periphery of the base island, wherein the chip is arranged on the base island and electrically connected to the pins, wherein the plastic encapsulation layer covers the chip, the base island and part of the pins, wherein the pin ends are bent to form a straight outer pin segment, wherein the outer pin segment extends out from the lower surface of the plastic encapsulation layer, and the lower surface of the plastic encapsulation layer is attached to the upper surface of the outer pin segment; wherein the side wall surface of the plastic encapsulation layer is flush with or located outside the side wall surface of the outer pin segment; wherein the plastic encapsulation layer is provided with a metal shielding layer at least on its side wall surface, and the metal shielding layer extends at least to below the plane where the chip is located. The metal shielding layer that completely covers the side surface of the chip has an excellent shielding effect, and the plastic encapsulation layer completely covers the base island and abuts against the upper surface of the outer pin segment, thereby improving the sealing performance of the package structure and enhancing the stability of the package structure with some pins exposed.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging, and in particular to a pin-bent QFN packaging structure and a manufacturing method thereof. Background Art

[0002] The base island and pins of the QFN (Quad Flat No-leads) packaging structure are generally located at the bottom of the package body, and the side walls of the pins are flush with and exposed to the side walls of the plastic layer. Therefore, the metal shielding layer formed by plating on the side walls of the plastic layer needs to avoid the pin area to avoid short circuit. In some existing technologies, in order to avoid short circuit, the position covered by the shielding layer is further reduced. However, since the chip is arranged on the base island, the side area of ​​the chip that can actually be covered by the shielding layer is small, and the shielding effect is not good. Summary of the invention

[0003] The object of the present invention is to provide a pin-bent QFN packaging structure and a manufacturing method thereof.

[0004] The present invention provides a pin-bent QFN packaging structure, comprising a lead frame, at least one chip and a plastic encapsulation layer, wherein the lead frame comprises at least one base island and a plurality of pins located around the base island, the chip is arranged on the base island and electrically connected to the pins, the plastic encapsulation layer covers the chip, the base island and part of the pins, the pin ends are bent to form straight outer pin segments, the outer pin segments extend out from the lower surface of the plastic encapsulation layer, and the lower surface of the plastic encapsulation layer is attached to the upper surface of the outer pin segments;

[0005] The side wall surface of the plastic encapsulation layer is flush with the side wall surface of the outer lead segment or is located outside thereof;

[0006] The plastic packaging layer is provided with a metal shielding layer at least on its side wall surface, and the metal shielding layer at least extends to below the plane where the chip is located.

[0007] As a further improvement of the present invention, the pins are divided into an inner pin segment, a middle pin segment and an outer pin segment in sequence from the side facing the base island to the outside, the chip is electrically connected to the inner pin segment, the outer pin segment is located below the inner pin segment and the base island, and the plastic encapsulation layer covers the base island, the chip, the inner pin segment and the middle pin segment, and exposes the outer pin segment.

[0008] As a further improvement of the present invention, the inner pin segment is straight, and its lower surface is flush with the lower surface of the base island.

[0009] As a further improvement of the present invention, the middle pin segment is a straight segment, and the angle between the middle pin segment and the inner pin segment is a° , 90 ≤a <180.

[0010] As a further improvement of the present invention, it also includes a ground pin, the lower surface of which is higher than the upper surface of the outer pin segment, exposed to the side wall of the plastic packaging layer, and electrically connected to the metal shielding layer.

[0011] As a further improvement of the present invention, the ground pin is flush with the inner pin segment.

[0012] The present invention also provides a method for manufacturing a pin-bent QFN packaging structure, comprising the steps of:

[0013] The lead frame pins are bent to form inner lead segments, middle lead segments and outer lead segments in sequence from the side facing the lead frame base island outward, and the outer lead segments are straight and located below the inner lead segments;

[0014] Placing the lead frame on a pad fitted therewith, placing a chip on the lead frame base island, and bonding wires between the chip and the inner lead segments;

[0015] Plastic encapsulates the lead frame base island, the chip, the inner lead segment and the middle lead segment, and exposes the outer lead segment, wherein the lower surface of the plastic encapsulation layer is flush with the upper surface of the outer lead segment, and the side wall surface of the plastic encapsulation layer is flush with or located outside the side wall surface of the outer lead segment;

[0016] A metal shielding layer is plated at least on the outer side of the plastic sealing layer, and the metal shielding layer is at least extended to below the plane where the bottom surface of the base island is located.

[0017] As a further improvement of the present invention, “bending the lead frame pins to form inner pin segments, middle pin segments and outer pin segments in sequence from the side facing the base island outward” specifically includes:

[0018] Bend some of the pins downward b° , forming the intermediate lead segment, 0< b ≤90;

[0019] Then bend part of the middle pin upwards b° , forming the outer pin segment.

[0020] As a further improvement of the present invention, “plastic encapsulating the base island, the chip, the inner lead segment and the middle lead segment, and exposing the outer lead segment” specifically includes:

[0021] Placing the lead frame in a plastic encapsulation mold, and embedding the outer lead segment in a groove on the mold that matches the shape of the lead frame;

[0022] The lead frame and the chip are plastic-sealed.

[0023] As a further improvement of the present invention, “plastic encapsulating the base island, the chip, the inner lead segment and the middle lead segment, and exposing the outer lead segment” specifically includes:

[0024] Placing the lead frame in a plastic encapsulation mold and inserting a spacer above the outer lead segment;

[0025] The lead frame and the chip are plastic-sealed above the spacer.

[0026] As a further improvement of the present invention, the steps are also included:

[0027] Retain at least one pin without bending to form a ground pin, or weld at least one ground pin on the lead frame;

[0028] The ground pin is plastic-sealed and exposed at a side of the plastic-sealing layer.

[0029] The beneficial effects of the present invention are: by bending the pins to form inner pin segments, middle pin segments and outer pin segments that are angled with each other in sequence, and completely covering the inner pin segments and the middle pin segments with a plastic encapsulation layer and exposing the outer pin segments, a metal shielding layer that completely covers the periphery of the chip can be formed on the plastic encapsulation layer, and the shielding effect is excellent. Moreover, the plastic encapsulation layer completely covers the base island and abuts against the upper surface of the outer pin segment, which can improve the sealing of the packaging structure and enhance the stability of the packaging structure with some pins exposed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a pin-bent QFN package structure in one embodiment of the present invention.

[0031] Figure 2 It is a schematic diagram of a method flow of a method for manufacturing a pin-bent QFN packaging structure in one embodiment of the present invention.

[0032] Figures 3 to 7 It is a schematic diagram of the steps of a method for manufacturing a pin-bent QFN package structure in one embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in combination with the specific implementation methods of this application and the corresponding drawings. Obviously, the described implementation methods are only part of the implementation methods of this application, not all of the implementation methods. Based on the implementation methods in this application, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0035] For ease of explanation, this document uses terms that represent relative positions in space for description, such as "above", "below", "back", "front", etc., to describe the relationship of one unit or feature shown in the drawings relative to another unit or feature. Terms of relative positions in space can include different orientations of the device in use or operation other than the orientation shown in the figure. For example, if the device in the figure is turned over, the unit described as being "below" or "above" other units or features will be located "below" or "above" the other units or features. Therefore, the exemplary term "below" can encompass both the spatial orientations of below and above.

[0036] like Figure 1 As shown, the present invention provides a pin-bent QFN packaging structure, including a lead frame 1, at least one chip 2 and a plastic packaging layer 3, the lead frame 1 includes at least one base island 11 and a plurality of pins 12 located around the base island 11, the chip 2 is arranged on the base island 11 and electrically connected to the pins 12.

[0037] The plastic encapsulation layer 3 covers the chip 2, the base island 11 and part of the pins 12. The ends of the pins 12 are bent to form straight outer pin segments 123. The outer pin segments 123 extend out from the lower surface of the plastic encapsulation layer 3, and the lower surface of the plastic encapsulation layer 3 is attached to the upper surface of the outer pin segments 123.

[0038] Specifically, the pin 12 is divided into an inner pin segment 121, a middle pin segment 122 and an outer pin segment 123 from the side facing the base island 11 to the outside. The chip 2 is electrically connected to the inner pin segment 121 through a metal lead. The outer pin segment 123 is straight and is located below the inner pin segment 121 and the base island 11, that is, it is bent at least twice so that the outer pin segment 123, which is the electrical output end of the packaging structure, and the inner pin segment 121 are not in the same plane, and are lower than the inner pin segment 121 and the base island 11.

[0039] The inner pin segment 121, the middle pin segment 122 and the outer pin segment 123 mentioned here are just a general term for the three parts of the pin 12. The inner pin segment 121 is the part of the pin 12 used to form an electrical connection with the chip 2, the outer pin segment 123 is the part of the pin 12 that serves as the electrical output port of the QFN packaging structure, and the middle pin segment 122 is the part of the pin 12 that connects the inner pin segment 121 and the outer pin segment 123. It can include more sophisticated structures according to design requirements, or a bending structure can be formed in each part, and the present invention does not make specific restrictions on this.

[0040] Furthermore, the inner lead segment 121 is straight, and its lower surface is flush with the lower surface of the base island 11 . Since the outer lead segment 123 is located below the inner lead segment 121 , a certain space can be formed below the base island 11 .

[0041] Furthermore, in this embodiment, the middle lead segment 122 is a straight segment, and the angle between it and the inner lead segment 121 is a°, 90≤a<180, that is, through two bends, the lead frame 1, which was originally a planar structure, forms a three-dimensional step-type structure, and its structure can be regarded as similar to the L-shaped lead 12 in the traditional QFP (Quad Flat Package, square flat packaging technology) structure to a certain extent, but in the present invention, the step-type lead 12 is formed by bending the planar lead frame 1 in the QFN packaging structure. Controlling the angle between the middle lead segment 122 and the inner lead segment 121 to be greater than 90° is convenient for implementation in the manufacturing process, and is convenient for forming a plastic encapsulation layer 3 structure that exposes part of the lead 12 segment during the plastic encapsulation process.

[0042] It is understandable that, since the outer pin segment 123 and the inner pin segment 121 are both straight, that is, parallel to each other, the angle between the middle pin segment 122 and the inner pin segment 121 is the angle between the middle pin segment 122 and the outer pin segment 123 .

[0043] The plastic encapsulation layer 3 covers the base island 11, the chip 2, the inner pin segment 121 and the middle pin segment 122, and exposes the outer pin segment 123, and the lower surface of the plastic encapsulation layer 3 is flush with the upper surface of the outer pin 12. The plastic encapsulation layer 3 completely covers the inner pin segment 121 and the middle pin segment 122. Since the lower surface of the inner pin 12 is flush with the lower surface of the base island 11, the plastic encapsulation layer 3 fills the space below the base island 11, and the lower surface of the plastic encapsulation layer 3 is lower than the base island 11, which can greatly improve the sealing of the QFN packaging structure. The outer pin 12 is in contact with the plastic encapsulation layer 3, which can improve the stability of the QFN packaging structure in the present invention and avoid the problem of packaging structure collapse that may be caused by exposing the outer pin segment 123.

[0044] The side wall surface of the plastic encapsulation layer 3 is flush with or located outside the side wall surface of the external pin segment 123, so that when the metal shielding layer 4 is plated on the side wall surface of the plastic encapsulation layer 3, even if the metal shielding layer 4 completely covers the side wall surface of the plastic encapsulation layer 3, no short circuit will be formed between the external pin segment 123.

[0045] The main material of the plastic encapsulation layer 3 can be a polymer composite material with fillers such as epoxy resin, polyimide, dry film, etc., which also includes functional components such as curing agent, filler, accelerator, release agent, coupling agent, etc. The plastic encapsulation layer 3 covers the lead frame 1 and chip 2 to play a protective role and provide physical support for the packaging structure.

[0046] The plastic packaging layer 3 is provided with a metal shielding layer 4 at least on its side wall surface, and the metal shielding layer 4 at least extends to below the plane where the bottom surface of the base island 11 is located.

[0047] The metal shielding layer 4 is a continuous thin film coating, which is used to reduce the electromagnetic interference to the chip 2 and other optional electronic components. The electromagnetic shielding layer can be a sputtered sandwich metal film material such as copper, stainless steel, titanium, or a conductive composite material such as a conductive resin containing high-density metal fillers such as silver / copper, or a combination of at least two of the above materials, which can play a role in shielding or absorbing electromagnetic waves.

[0048] Specifically, in the present embodiment, the metal shielding layer 4 completely covers the side walls and the upper surface of the plastic encapsulation layer 3. Since the plastic encapsulation layer 3 completely covers the base island 11, the metal shielding layer 4 can extend to below the base island 11 (i.e., extend to below the chip 2) without the risk of short circuit with the pin 12, thereby forming a full covering structure for the side and top surfaces of the chip 2, having a good electromagnetic shielding effect.

[0049] Furthermore, the pin 12 also includes a ground pin 13 connected to the metal shielding layer 4, the lower surface of the ground pin 13 is higher than the upper surface of the outer pin segment 123, exposed to the side wall of the plastic layer 3, and electrically connected to the metal shielding layer 4. Specifically, in this embodiment, the ground pin 13 is flush with the inner pin segment 121. Since the outer pin segment 123 extends downward, it is simpler and more efficient to set the ground pin 13 connected to the metal shielding layer 4 in the pin 12.

[0050] In addition, in the present invention, the lead frame 1 structure formed by sequential bending in the manufacturing process is easier to fit with the pad 5 arranged thereunder during the wire bonding process, compared with the traditional half-etched QFN lead frame 1, thereby improving the supporting effect of the pad 5 on the lead frame 1 and solving the problem of unstable wire bonding caused by the excessive length of the pins 12 of the QFN package lead frame 1.

[0051] like Figure 2 As shown, the present invention also provides a method for manufacturing a pin-bent QFN package structure, comprising the steps of:

[0052] S1: Figure 3 As shown, the lead 12 of the lead frame 1 is bent to form an inner lead segment 121, a middle lead segment 122 and an outer lead segment 123 from the side facing the base island 11 outward in sequence, and the outer lead segment 123 is straight and located below the inner lead segment 121.

[0053] Specifically, part of the pins 12 are bent downward by b° to form a middle pin segment 122 , 0<b≤90; then part of the middle pin segment 122 is bent upward by b° to form an outer pin segment 123 .

[0054] Furthermore, step S1 also includes the steps of: leaving at least one pin 12 unbent to form a ground pin 13 , or welding an additional pin 12 to the lead frame 1 to form a ground pin 13 after bending the pin 12 .

[0055] S2: Figure 4 As shown, the lead frame 1 is placed on the pad 5 that is bonded thereto, the chip 2 is placed on the base island 11 of the lead frame 1, and wire bonding is performed between the chip 2 and the inner lead segment 121 .

[0056] The shape of the upper surface of the pad 5 matches the shape of the bent lead 12 , and the lead frame 1 fits thereon when placed thereon, thereby obtaining good support and avoiding the problem of unstable wire bonding.

[0057] S3: The base island 11, chip 2, inner pin segment 121 and middle pin segment 122 are molded, and the outer pin segment 123 is exposed, and the lower surface of the plastic layer 3 is flush with the upper surface of the outer pin segment 123, and the side wall of the plastic layer 3 is flush with the side wall of the outer pin segment 123 or located outside it.

[0058] Specifically, Figure 5 As shown, in one embodiment of the present invention, step S3 includes:

[0059] The lead frame 1 is placed in a plastic encapsulation mold, and the outer lead segment 123 is buried in a groove on the mold that matches its shape, thereby shielding the outer lead segment 123 and preventing the formation of a plastic encapsulation layer 3 covering the outer lead segment 123;

[0060] The lead frame 1 and the chip 2 are plastic-sealed.

[0061] like Figure 6 As shown, in one embodiment of the present invention, step S3 includes:

[0062] The lead frame 1 is placed in a plastic encapsulation mold, and a spacer 7 is inserted above the outer lead segment 123 to form a barrier layer through the spacer 7, thereby preventing the formation of a plastic encapsulation layer 3 covering the outer lead segment 123;

[0063] The lead frame 1 and the chip 2 are plastic-sealed above the spacer 7 .

[0064] Furthermore, step S3 further includes the step of: plastic-sealing the ground pin 13 and exposing the ground pin 13 to the side of the plastic-sealing layer 3 .

[0065] S4: Figure 7 As shown, a metal shielding layer 4 is plated at least on the outer side of the plastic packaging layer 3, and the metal shielding layer 4 is at least extended to below the plane where the bottom surface of the base island 11 is located.

[0066] Specifically, in this embodiment, the metal shielding layer 4 is sputtered on the plastic packaging layer 3 to completely cover the four sidewall surfaces and the upper surface thereof.

[0067] To sum up, the present invention bends the pins to form inner pin segments, middle pin segments and outer pin segments that are angled with each other in sequence, and completely covers the inner pin segments and the middle pin segments with a plastic encapsulation layer to expose the outer pin segments, thereby forming a metal shielding layer on the plastic encapsulation layer that completely covers the periphery of the chip, and has excellent shielding effect. Moreover, the plastic encapsulation layer completely covers the base island and abuts against the upper surface of the outer pin segment, which can improve the sealing of the packaging structure and enhance the stability of the packaging structure with some pins exposed.

[0068] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0069] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pin-bent QFN package structure, comprising a lead frame, at least one chip and a plastic encapsulation layer, wherein the lead frame comprises at least one base island and a plurality of pins located around the base island, the chip is arranged on the base island and electrically connected to the pins, characterized in that: The plastic encapsulation layer covers the chip, the base island and part of the pins, the ends of the pins are bent to form straight outer pin segments, the outer pin segments extend out from the lower surface of the plastic encapsulation layer, and the lower surface of the plastic encapsulation layer is attached to the upper surface of the outer pin segments; The pins are formed by a bending process, and the pins are divided into an inner pin segment, a middle pin segment and an outer pin segment from the side facing the base island outward in sequence, the chip is electrically connected to the inner pin segment, and the outer pin segment is located below the inner pin segment and the base island, the plastic encapsulation layer covers the base island, the chip, the inner pin segment and the middle pin segment, and exposes the outer pin segment; the side wall surface of the plastic encapsulation layer is flush with the side wall surface of the outer pin segment or is located outside thereof; The plastic packaging layer is provided with a metal shielding layer at least on its side wall surface, and the metal shielding layer at least extends to below the plane where the chip is located.

2. The pin-bent QFN package structure according to claim 1, characterized in that: The inner lead segment is straight, and a lower surface thereof is flush with a lower surface of the base island.

3. The pin-bent QFN package structure according to claim 2, characterized in that: The middle pin segment is a straight segment, and the angle between it and the inner pin segment is a° , 90 ≤ a <180.

4. The pin-bent QFN package structure according to claim 2, characterized in that: It also includes a ground pin, the lower surface of which is higher than the upper surface of the outer pin segment, exposed to the side wall of the plastic packaging layer, and electrically connected to the metal shielding layer.

5. The pin-bent QFN package structure according to claim 4, characterized in that: The ground pin is flush with the inner pin segment.

6. A method for manufacturing a pin-bent QFN package structure, characterized in that: Includes steps: The lead frame pins are bent to form inner lead segments, middle lead segments and outer lead segments in sequence from the side facing the lead frame base island outward, and the outer lead segments are straight and located below the inner lead segments; Placing the lead frame on a pad fitted therewith, placing a chip on the lead frame base island, and bonding wires between the chip and the inner lead segments; Plastic encapsulates the lead frame base island, the chip, the inner lead segment and the middle lead segment, and exposes the outer lead segment, wherein the lower surface of the plastic encapsulation layer is flush with the upper surface of the outer lead segment, and the side wall surface of the plastic encapsulation layer is flush with or located outside the side wall surface of the outer lead segment; A metal shielding layer is plated at least on the outer side of the plastic sealing layer, and the metal shielding layer is at least extended to below the plane where the bottom surface of the base island is located.

7. The method for manufacturing a pin-bent QFN package structure according to claim 6, characterized in that: “Bending the lead frame pins to form inner pin segments, middle pin segments and outer pin segments in sequence from the side facing the base island outward” specifically includes: Bend some of the pins downward b° , forming the intermediate lead segment, 0< b ≤90; Then bend part of the middle pin upwards b° , forming the outer pin segment.

8. The method for manufacturing a pin-bent QFN package structure according to claim 6, characterized in that: “Plastic encapsulating the base island, the chip, the inner lead segment and the middle lead segment, and exposing the outer lead segment” specifically includes: Placing the lead frame in a plastic encapsulation mold, and embedding the outer lead segment in a groove on the mold that matches the shape of the lead frame; The lead frame and the chip are plastic-sealed.

9. The method for manufacturing a pin-bent QFN package structure according to claim 6, characterized in that: “Plastic encapsulating the base island, the chip, the inner lead segment and the middle lead segment, and exposing the outer lead segment” specifically includes: Placing the lead frame in a plastic encapsulation mold and inserting a spacer above the outer lead segment; The lead frame and the chip are plastic-sealed above the spacer.

10. The method for manufacturing a pin-bent QFN package structure according to claim 6, characterized in that: Also includes the steps: Retain at least one pin without bending to form a ground pin, or weld at least one ground pin on the lead frame; The ground pin is plastic-sealed and exposed at a side of the plastic-sealing layer.

Images