Packaging structure and forming method thereof

Abstract

The invention provides a packaging structure and a forming method thereof, and the method comprises the steps: patterning a metal plate to form an initial lead frame comprising at least one lead unit, the lead unit comprises an initial base island, initial pins located at the periphery of the initial base island, and a first groove between the initial base island and the initial pins, the initial pin comprises a second end part which is positioned on the same plane with the initial base island and a first end part which is vertically arranged on at least part of the second end part; bonding a chip on the first end surface of the initial base island; connecting the chip and the second end part by adopting a welding wire; filling a plastic package material between the initial base island and the initial pin to form a plastic package body which wraps the chip and the welding wire and is filled in the first groove; and at least removing the metal plate at the bottom of the first groove to form a lead frame and a base island independent of the lead frame. According to the technical scheme, the heat dissipation speed of the packaging structure can be increased, the production process is simplified, and the production cost is saved.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to a packaging structure and a method for forming the same. Background Art

[0002] With the development of electronic technology, miniaturization, high integration of structure and function, and high heat dissipation of packaging have become the development trend of electronic components. Since top-cooling packaging has the advantage of directly dissipating heat through high thermal mass and high thermal conductivity sources, its thermal response will be better. Therefore, the market currently uses top-cooling to improve the thermal effect of product applications.

[0003] However, currently, the packaging structure with downset pins or the addition of heat sinks to achieve top heat dissipation is generally adopted, which has a complex packaging process and high cost. Moreover, there is no better solution for the current leadless packages such as Dual Flat No-lead Package (DFN) or Quad Flat No-lead Package (QFN).

[0004] Therefore, it is a technical problem that needs to be solved urgently to provide a packaging structure with simple process and low cost and a method for forming the same to accelerate the heat dissipation speed of the packaging structure. Summary of the invention

[0005] The technical problem to be solved by the present application is to provide a packaging structure and a method for forming the same, so as to speed up the heat dissipation of the packaging structure, simplify the production process, and save production costs.

[0006] In order to solve the above problems, the present application provides a method for forming a packaging structure, the method comprising: patterning a metal plate to form an initial lead frame, the initial lead frame comprising at least one lead unit, the lead unit comprising an initial base island, an initial pin located at the periphery of the initial base island and a first groove between the initial base island and the initial pin, the initial pin comprising: a second end located in the same plane as the initial base island and a first end vertically arranged on at least a portion of the second end; bonding a chip to the first end surface of the initial base island; connecting the chip and the second end with a welding wire; filling a plastic encapsulation material between the initial base island and the initial pin to form a plastic encapsulation body exposing a surface of the second end away from the first end and a surface of the first end away from the second end, the plastic encapsulation body covering the chip and the welding wire and filling the first groove; removing at least the metal plate at the bottom of the first groove to form the pin and the base island.

[0007] In some specific embodiments, the step of at least removing the metal plate at the bottom of the first groove to form the lead and the base island further includes: etching a part of the second end portion and the initial base island to form a second groove exposing the encapsulant within the first groove, a base island with a second protrusion on the sidewall, and a lead whose surface of the second end portion away from the first end portion is stepped and whose region near the base island of the second end portion has a first protrusion, the thickness of the first protrusion being less than the thickness of the region of the lead away from the base island.

[0008] In some specific embodiments, after the step of at least removing the metal plate at the bottom of the first groove to form the lead and the base island, the method further includes: filling a solder resist material in the second groove to form a protective layer covering the first protrusion, the second protrusion, and the surface of the encapsulant filled between the first protrusion and the second protrusion away from the first end portion.

[0009] In some specific embodiments, after the step of filling a solder resist material in the second groove to form a protective layer covering the first protrusion, the second protrusion, and the surface of the encapsulant filled between the first protrusion and the second protrusion away from the first end portion, the method further includes: forming a contact layer on the second end face of the base island, the end face of the first end portion, and the end face of the second end portion not covered by the protective layer.

[0010] In some specific embodiments, the step of patterning a metal plate to form an initial lead frame further includes: forming a third groove between two adjacent lead units.

[0011] To solve the above problems, the present application also provides a packaging structure, including: a base island; a chip disposed on the first end face of the base island; a lead disposed on the outer periphery of the base island, the lead including: a second end portion coplanar with the base island and a first end portion vertically disposed on at least a part of the second end portion; a bonding wire connecting the chip and the second end portion; an encapsulant filled between the base island and the lead and exposing the surface of the second end portion away from the first end portion and the surface of the first end portion away from the second end portion, the encapsulant covering the chip and the bonding wire.

[0012] In some specific embodiments, the surface of the second end portion away from the first end portion is stepped, and the region of the second end portion near the base island has a first protrusion, the thickness of the first protrusion being less than the thickness of the region of the lead away from the base island.

[0013] In some specific embodiments, a second protruding portion is provided on the sidewall of the base island. The surface of the first protruding portion, the second protruding portion, and the encapsulant filled between the first protruding portion and the second protruding portion, which is away from the first end, is substantially flush and covered with a protective layer.

[0014] In some specific embodiments, a contact layer is provided on the second end face of the base island, the end face of the first end, and the end face of the second end that is not covered by the protective layer.

[0015] In some specific embodiments, the sidewall of the lead away from the base island is covered with an encapsulant.

[0016] In the above technical solution, by forming the lead frame having a second end located in the same plane as the base island and a first end vertically provided on at least a part of the second end, and forming an encapsulant that exposes the surface of the second end away from the first end and the surface of the first end away from the second end, without involving equipment modification, the encapsulation process for top heat dissipation is simplified, the production cost is reduced, and the formed encapsulation structure can be applied to leadless packaging, solving the problem of slow heat dissipation speed in leadless packaging.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the authorization specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the following will briefly introduce the drawings required to be used in the embodiments of this application. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 is a schematic diagram of the steps of the method for forming the encapsulation structure in the first embodiment of this application;

[0020] Figures 2 to 8 is a schematic diagram of the device structure formed by the main steps in the first embodiment of this application;

[0021] Figures 9 to 10 is a schematic diagram of the device structure formed by the main steps in the second embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are only a part rather than all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0023] To solve the problems in the prior art that the packaging process for realizing top heat dissipation by using a lead-down or adding a heat sink has a complex process and high cost, and to accelerate the heat dissipation speed of the leadless package, an embodiment of the present application provides a packaging structure and a forming method thereof.

[0024] First, a forming method of a packaging structure provided in an embodiment of the present application will be introduced below.

[0025] Please refer to Figures 1 to 8 , wherein, Figure 1 is a schematic diagram of the steps of the forming method of the packaging structure in the first embodiment of the present application, Figures 2 to 8 is a schematic diagram of the device structure formed by the main steps in the first embodiment of the present application.

[0026] As Figure 1 shown, the forming method of the packaging structure in this embodiment includes: Step S11, patterning a metal plate to form an initial lead frame, the initial lead frame including at least one lead unit, the lead unit including an initial base island, an initial lead located on the outer periphery of the initial base island, and a first groove between the initial base island and the initial lead, the initial lead including: a first end perpendicular to the first end face of the initial base island and a second end in the same plane as the initial base island; Step S12, bonding a chip to the first end face of the initial base island; Step S13, connecting the chip and the initial lead with a welding wire; Step S14, filling a plastic encapsulation material between the initial base island and the initial lead to form a plastic encapsulation body exposing the surface of the second end away from the first end and the surface of the first end away from the second end, the plastic encapsulation body covering the chip and the welding wire and filling in the first groove; Step S15, removing at least the metal plate at the bottom of the first groove to form a base island and a lead.

[0027] Now, please refer to Step S11 and Figure 2, pattern a metal plate to form an initial lead frame, the initial lead frame including at least one lead unit 11, the lead unit 11 including: an initial base island 21, an initial pin 22 located on the outer periphery of the initial base island 21, and a first groove 23 between the initial base island 21 and the initial pin 22, the initial pin 22 including: a second end 222 coplanar with the initial base island 21 and a first end 221 vertically provided on at least part of the second end 222. In this embodiment, by coating a photoresist on the metal plate, performing patterned exposure on the photoresist, developing to remove the exposed photoresist, and etching the metal plate not covered by the photoresist to pattern the metal plate, the metal plate can be a multi-component copper alloy such as copper-iron system, copper-nickel-silicon system, copper-chromium system, copper-nickel-tin system, etc., which has good mechanical strength, stress relaxation resistance characteristics, and low creep properties.

[0028] Please refer to step S12, step S13 and Figure 3 , bond the chip 24 to the first end face 211 of the initial base island 21; use a welding wire 25 to connect the chip 24 and the initial pin 22. In this embodiment, use a conductive adhesive or a non-conductive adhesive to bond the chip 24 to the first end face of the initial base island 21, connect one end of the welding wire 25 to the chip 24, and the other end to the second end 222 of the initial pin 22. The material of the welding wire 25 can be gold, aluminum, or copper metal.

[0029] Please refer to step S14 and Figure 4 , fill a plastic encapsulation material between the initial base island 21 and the initial pin 22 to form a plastic encapsulation body 26 exposing the surface of the second end 222 away from the first end 221 and the surface of the first end 221 away from the second end 222, the plastic encapsulation body 26 covering the chip 24 and the welding wire 25 and filling in the first groove 23. In this embodiment, the top surface of the plastic encapsulation body 26 is flush with the top surface of the first end 221.

[0030] Please refer to step S15 and Figure 5, in this embodiment, the step of at least removing the metal plate at the bottom of the first groove 23 to form the lead 27 and the base island 28 further includes: etching a part of the second end 222 and the initial base island 21 from the surface of the metal plate facing away from the encapsulant, so as to form a second groove 29 exposing the encapsulant 26 located in the first groove 23, a base island 28 with a second protrusion 281 on the side wall, and the lead 27 whose surface of the second end 222 away from the first end 221 is stepped and has a first protrusion 273 in the area where the second end 222 is close to the base island 28. In this step, a semi-etching process is used to etch the second end 222 and the initial base island 21 from the surface of the metal plate facing away from the encapsulant.

[0031] Please refer to the following Figure 6 , in this embodiment, after the step of at least removing the metal plate at the bottom of the first groove 23 to form the lead 27 and the base island 28, the method further includes: filling a solder resist material in the second groove 29 to form a protective layer 31 covering the first protrusion 273, the second protrusion 281 and the surface of the encapsulant 26 filled between the first protrusion 273 and the second protrusion 281 and facing away from the first end 221. In this embodiment, the solder resist material is ink.

[0032] Please refer to the following Figure 7 , in this embodiment, after the step of filling a solder resist material in the second groove 29 to form a protective layer 31 covering the first protrusion 273, the second protrusion 281 and the surface of the encapsulant 26 filled between the first protrusion 273 and the second protrusion 281 and facing away from the first end 221, the method further includes: forming a contact layer 32 on the second end face 212 of the base island 28, the end face of the first end 221 and the end face of the second end 222 not covered by the protective layer 31. The contact layer 32 is used to realize the mounting between multiple packaging structures. The packaging structure of the present invention has the contact layer 32 on both sides, and double-sided mounting can be realized. In this embodiment, the second end face 212 of the base island 28 is parallel to the first end face 211 of the base island 28, and the way of forming a contact layer 32 is electroplating with tin.

[0033] Please refer to the following Figure 8 , in this embodiment, the device formed by the above steps is cut along the dividing line AA' between two adjacent lead units 11 and reversed to form a top-cooling packaging structure.

[0034] Please refer to the following Figures 9 to 10It is a schematic diagram of the device structure formed by the main steps in the second embodiment of the present application. In this embodiment, the step of patterning a metal plate to form an initial lead frame includes: forming a plurality of lead units 11, and forming a third groove 12 between two adjacent lead units 11. The lead unit 11 includes an initial base island 21, an initial lead 22 located on the outer periphery of the initial base island 21, and a first groove 23 between the initial base island 21 and the initial lead 22. The initial lead 22 includes: a second end 222 coplanar with the initial base island 21 and a first end 221 vertically provided on at least part of the second end 222, as Figure 9 shown.

[0035] In this embodiment, the steps of bonding the chip 24 to the first end face 211 of the initial base island 21 and connecting the chip 24 and the initial lead 22 with a bonding wire 25 are the same as the steps S12 and S13 described in the first embodiment of the present application, and will not be elaborated here. Different from the first embodiment of the present application, in this embodiment, a molding compound is filled between the initial base island 21 and the initial lead 22 to form a molded body 26 that exposes the surface of the second end 222 away from the first end 221 and the surface of the first end 221 away from the second end 222. The molded body 26 covers the chip 24 and the bonding wire 25, and during the process of filling the first groove 23, the molded body 26 also fills the third groove 12. After forming the molded body 26, the device formed by the above steps is cut along the dividing line AA' between two adjacent lead units 11 and inverted to form a top-cooling package structure, as Figure 10 shown. In this embodiment, by forming a third groove 12 between two adjacent lead units 11, without increasing the volume of the package structure, the side surface of the lead 27 does not expose metal, avoiding the influence of cutting burrs on the formed package structure and improving the reliability of the formed package structure.

[0036] Through the above technical solution, by forming the lead 27 having a second end 222 coplanar with the base island 28 and a first end 221 vertically provided on at least part of the second end 222, and forming a molded body 26 that exposes the surface of the second end 222 away from the first end 221 and the surface of the first end 221 away from the second end 222, without involving equipment modification, the top-cooling packaging process is simplified, the production cost is reduced, and the formed package structure can be applied to leadless packaging, solving the problem of slow heat dissipation speed of leadless packaging.

[0037] Based on the same inventive concept, the present application also provides a package structure. As Figure 8As shown, the encapsulation structure includes: a base island 28, a chip 24, pins 27, bonding wires 25, and a plastic package 26. The chip 24 is disposed on a first end face of the base island 28; the pins 27 are disposed on the outer periphery of the base island 28, and the pins 27 include: a second end portion 222 located in the same plane as the base island 28 and a first end portion 221 vertically provided on at least a part of the second end portion 222; the bonding wires 25 connect the chip 24 and the second end portion 222; the plastic package 26 is filled between the base island 28 and the pins 27, and exposes a surface of the second end portion 222 away from the first end portion 221 and a surface of the first end portion 221 away from the second end portion 222, and the plastic package 26 covers the chip 24 and the bonding wires 25.

[0038] In this embodiment, the materials of the base island 28 and the pins 27 may be multi-component copper alloys such as copper-iron series, copper-nickel-silicon series, copper-chromium series, copper-nickel-tin series, etc., which have good mechanical strength, stress relaxation resistance characteristics, and low creep properties. The material of the bonding wires 25 may be gold, aluminum, or copper metal.

[0039] Please continue to refer to Figure 8 , in this embodiment, the surface of the second end portion 222 away from the first end portion 221 is stepped, and a first protrusion 273 is provided in a region of the second end portion 222 close to the base island 28, and the thickness of the first protrusion 273 is less than the thickness of the region of the pins 27 away from the base island 28.

[0040] Please continue to refer to Figure 8 , in this embodiment, a second protrusion 281 is provided on a side wall of the base island 28. The first protrusion 273, the second protrusion 281, and a surface of the plastic package 26 filled between the first protrusion 273 and the second protrusion 281 away from the first end portion 221 are substantially flush and covered with a protective layer 31. The material of the protective layer 31 is ink.

[0041] Please continue to refer to Figure 8 , in this embodiment, a contact layer 32 is provided on a second end face 212 of the base island 28, an end face of the first end portion 221, and an end face of the second end portion 222 not covered by the protective layer 31. The second end face 212 of the base island 28 is parallel to a first end face 211 of the base island 28. The contact layer 32 is a tin layer. The encapsulation structure of the present invention has the contact layer 32 on both sides, and double-sided mounting can be achieved.

[0042] Please continue to refer to Figure 10, in this embodiment, the side wall of the pin 27 away from the base island 28 is covered with a plastic package 26. The side surface of the pin 27 does not expose metal, avoiding the influence of cutting burrs on the formed package structure and improving the reliability of the formed package structure.

[0043] Through the above technical solution, by forming the pin 27 having a second end 222 in the same plane as the base island 28 and a first end 221 vertically provided on at least a part of the second end 222, and forming a plastic package 26 exposing the surface of the second end 222 away from the first end 221 and the surface of the first end 221 away from the second end 222, without involving equipment modification, the packaging process of top heat dissipation is simplified, the production cost is reduced, and the formed package structure can be applied to leadless packaging, solving the problem of slow heat dissipation speed of leadless packaging.

[0044] It should be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "further includes a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0045] Each embodiment in this specification is described in a related manner. The same or similar parts among the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized. In particular, for the second embodiment, since it is basically similar to the first embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the first embodiment.

[0046] The above is only the preferred embodiment of the present application and is not used to limit the protection scope of the present application. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present application, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A method for forming a packaging structure, characterized in that, The method includes: Pattern a metal plate to form an initial lead frame, the initial lead frame including at least one lead unit, the lead unit including an initial base island, an initial pin located on the outer periphery of the initial base island, and a first groove between the initial base island and the initial pin, the initial pin including: a second end portion in the same plane as the initial base island and a first end portion vertically provided on at least part of the second end portion; Bond a chip to the first end face of the initial base island; Connect the chip and the second end portion with a bonding wire; Fill a molding compound between the initial base island and the initial pin to form a molded body exposing the surface of the second end portion away from the first end portion and the surface of the first end portion away from the second end portion, the molded body covering the chip and the bonding wire and filling in the first groove; Remove at least the metal plate at the bottom of the first groove to form pins and a base island.

2. The method for forming the encapsulation structure according to claim 1, wherein The step of removing at least the metal plate at the bottom of the first groove to form pins and a base island further includes: Etch part of the second end portion and the initial base island to form a second groove exposing the molded body in the first groove, a base island with a second protrusion on the side wall, and the pin whose surface of the second end portion away from the first end portion is stepped and whose area near the base island of the second end portion has a first protrusion, the thickness of the first protrusion being less than the thickness of the area of the pin away from the base island.

3. The method for forming the encapsulation structure according to claim 2, wherein After the step of removing at least the metal plate at the bottom of the first groove to form pins and a base island, the method further includes: Fill a solder resist material in the second groove to form a protective layer covering the first protrusion, the second protrusion, and the surface of the molded body filled between the first protrusion and the second protrusion away from the first end portion.

4. The method for forming the encapsulation structure according to claim 3, wherein After the step of filling a solder resist material in the second groove to form a protective layer covering the first protrusion, the second protrusion, and the surface of the molded body filled between the first protrusion and the second protrusion away from the first end portion, the method further includes: Form a contact layer on the second end face of the base island, the end face of the first end portion, and the end face of the second end portion not covered by the protective layer.

5. The method for forming an encapsulation structure according to claim 1, wherein The step of patterning a metal plate to form an initial lead frame further includes: forming a third groove between two adjacent lead units.

6. An encapsulation structure, characterized in that, Including: A base island; A chip disposed on the first end face of the base island; Pins disposed on the outer periphery of the base island, the pins including: a second end portion in the same plane as the base island and a first end portion vertically provided on at least part of the second end portion; A bonding wire connecting the chip and the second end portion; A molded body filled between the base island and the pins and exposing the surface of the second end portion away from the first end portion and the surface of the first end portion away from the second end portion, the molded body covering the chip and the bonding wire.

7. The encapsulation structure according to claim 6, wherein The surface of the second end portion away from the first end portion is stepped, and a first convex portion is provided in a region of the second end portion close to the base island, and the thickness of the first convex portion is less than the thickness of the region of the pin away from the base island.

8. The encapsulation structure according to claim 7, wherein A second convex portion is provided on a side wall of the base island, and the surfaces of the first convex portion, the second convex portion, and the encapsulant filled between the first convex portion and the second convex portion away from the first end portion are substantially flush and covered with a protective layer.

9. The encapsulation structure according to claim 8, wherein, A contact layer is provided on the second end face of the base island, the end face of the first end portion, and the end face of the second end portion not covered by the protective layer.

10. The encapsulation structure according to claim 6, wherein, The side wall of the pin away from the base island is covered with an encapsulant.

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