Lead frame package structure, lead frame package structure manufacturing method and package module

Abstract

The present disclosure provides a lead frame packaging structure, a lead frame packaging structure manufacturing method and a packaging module, and relates to the technical field of semiconductor packaging. The lead frame packaging structure comprises a chip, a first plastic encapsulation body, a second plastic encapsulation body and a pin. The chip has a first surface and a second surface arranged oppositely. The first plastic encapsulation body encapsulates the chip and is located on the side of the first surface. The second plastic encapsulation body is arranged on the second surface. A heat conduction layer is arranged in the second plastic encapsulation body. The pin is located on the outer periphery of the second plastic encapsulation body, and the pin is electrically connected with the chip. The second plastic encapsulation body replaces the base island structure of the lead frame, which can solve the problem of cavities when the base island is welded with the circuit board, and can improve the heat dissipation performance.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more specifically, to a leadframe packaging structure, a method for manufacturing the leadframe packaging structure, and a packaging module. Background Technology

[0002] With the rapid development of the semiconductor industry, the QFN (Quad Flat No-lead Package) structure is widely used in the semiconductor industry. When using the QFN structure, a base island structure is usually adopted. The base island is used to mount and fix the chip and dissipate heat from the chip. However, when the QFN structure is mounted on the circuit board, the base island has a large area, which makes it difficult for air in the solder layer between the base island and the circuit board to escape during soldering, resulting in voids and affecting product reliability. Summary of the Invention

[0003] The objectives of this invention include, for example, providing a leadframe packaging structure, a method for manufacturing the leadframe packaging structure, and a packaging module, which can improve product reliability and enhance heat dissipation performance.

[0004] The embodiments of the present invention can be implemented as follows:

[0005] In a first aspect, the present invention provides a lead frame packaging structure, comprising:

[0006] A chip having a first surface and a second surface disposed opposite to each other;

[0007] A first molding compound, which encapsulates the chip and is located on one side of the first surface;

[0008] A second molding compound is disposed on the second surface; a thermally conductive layer is provided inside the second molding compound.

[0009] The pin is located on the outer periphery of the second molding compound and is electrically connected to the chip.

[0010] In an optional embodiment, the thermally conductive layer is disposed on the side of the second molding compound closest to the chip.

[0011] In an optional embodiment, an adhesive layer is provided between the thermally conductive layer and the chip.

[0012] In an optional embodiment, the second molding body has through slots, and heat dissipation bumps are formed between adjacent through slots.

[0013] In an optional implementation, the surface of the heat dissipation bump away from the chip is flush with the surface of the pin away from the chip.

[0014] In an optional embodiment, the pin has a step on the side near the second molding compound.

[0015] In an optional implementation, the step includes a first plane and a stop surface connected to the first plane, the stop surface being connected to a surface of the pin on the side away from the chip.

[0016] In an optional embodiment, the surface of the second molding compound is flush with the first plane, and the heat dissipation bump protrudes from the first plane.

[0017] Secondly, the present invention provides a method for manufacturing a lead frame packaging structure, the method comprising:

[0018] Provide base materials;

[0019] A first groove is formed on the third surface of the substrate;

[0020] A heat-conducting layer is formed within the first groove;

[0021] A chip is attached to the thermally conductive layer;

[0022] The substrate and the chip are electrically connected;

[0023] The chip is encapsulated to form a first encapsulation body;

[0024] A second groove is formed on the fourth surface of the substrate to expose the thermally conductive layer and the first encapsulation.

[0025] A second encapsulation is formed within the second groove.

[0026] In an optional implementation, the method further includes:

[0027] Heat dissipation bumps are formed on the second molding compound.

[0028] Thirdly, the present invention provides a packaging module, including a circuit board and a lead frame packaging structure as described in any of the foregoing embodiments, wherein the pins are electrically connected to the circuit board.

[0029] The beneficial effects of the embodiments of the present invention include, for example:

[0030] The lead frame packaging structure provided in this embodiment of the invention has the pins located on the outer periphery of the second molding compound. That is, the second molding compound replaces the traditional base island structure, avoiding the phenomenon of voids when the base island and circuit board are soldered in the traditional structure, which is beneficial to improving the reliability of the product. At the same time, a thermally conductive layer is provided in the second molding compound, which is beneficial to improving heat dissipation performance and heat dissipation effect.

[0031] The leadframe packaging structure fabrication method provided in this invention first forms a thermally conductive layer on one side of the third surface of the substrate, and then mounts the chip on the thermally conductive layer, which can provide better heat conduction to the back of the chip. A second groove is formed on the fourth surface of the substrate and filled with a second molding compound. The second molding compound replaces the base island, providing support and heat dissipation for the chip. Simultaneously, during the process of forming the second groove, the thermally conductive layer can protect the chip, preventing damage. This fabrication method is simple and easy to implement, and helps improve packaging efficiency and packaging quality.

[0032] The packaging module provided in this embodiment of the invention includes a circuit board and the lead frame packaging structure described above. Since the lead frame packaging structure uses a second molding compound to replace the traditional base island structure, it avoids the phenomenon of voids occurring when the base island and circuit board are soldered in the traditional structure, which is beneficial to improving the reliability of the product. At the same time, a thermally conductive layer is provided in the second molding compound, which is beneficial to improving heat dissipation performance and heat dissipation effect. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a first structure of the lead frame packaging structure provided in the first embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a second structure of the lead frame packaging structure provided in the first embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the structure of a packaging module including a lead frame packaging structure provided in the first embodiment of the present invention;

[0037] Figure 4 and Figure 5 This is a schematic diagram illustrating the steps of a method for fabricating a lead frame packaging structure according to a second embodiment of the present invention.

[0038] Icons: 100 - Leadframe package structure; 110 - Chip; 111 - Adhesive layer; 120 - First molding compound; 130 - Second molding compound; 131 - Through slot; 133 - Heat dissipation bump; 140 - Pin; 141 - Solder joint; 143 - Wire; 150 - Thermal conductive layer; 160 - Step; 161 - First plane; 163 - Stop surface; 200 - Package module; 210 - Circuit board; 211 - Solder pad; 220 - Solder; 170 - Substrate; 171 - Third surface; 173 - Fourth surface; 175 - First groove; 180 - Second groove. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0041] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0042] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0043] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0044] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0045] When using a square flat no-lead package (QFN) structure, a base island structure is typically employed. The base island is used to mount and fix the chip and to dissipate heat. However, when mounting the QFN structure onto a circuit board, the relatively large area of ​​the base island makes it difficult for air to escape from the solder layer between the base island and the circuit board during soldering, leading to voids and affecting product reliability. Furthermore, the inner side of the leads is usually covered by a plastic encapsulation, making it difficult to wet the sidewall solder, resulting in poor soldering quality.

[0046] To overcome at least one defect in the prior art, this embodiment proposes a lead frame packaging structure 100, which can improve product reliability, enhance heat dissipation performance, and thus improve product quality.

[0047] First Embodiment

[0048] Please refer to Figure 1 This embodiment provides a leadframe package structure 100, including a chip 110, a first molding compound 120, a second molding compound 130, and pins 140. The chip 110 has a first surface and a second surface disposed opposite to each other. The first molding compound 120 molds the chip 110 and is located on one side of the first surface. The second molding compound 130 is disposed on the second surface. A thermally conductive layer 150 is provided inside the second molding compound 130. The pins 140 are located on the outer periphery of the second molding compound 130 and are electrically connected to the chip 110. The second molding compound 130 replaces the base island structure of the leadframe, which can solve the void problem that occurs when the base island is soldered to the circuit board 210, improve product reliability, and improve heat dissipation performance by providing a thermally conductive layer 150 inside the second molding compound 130.

[0049] It should be noted that in traditional leadframe structures, the portion between pins 140 constitutes the base island structure. The base island area is typically large, and during soldering with the circuit board 210, gas is difficult to escape, easily generating bubbles or voids, which can lead to structural delamination and detachment, thus reducing product reliability. In this embodiment, a second molding compound 130 replaces the base island in the traditional structure, resulting in a base island-less design. This eliminates the need for soldering between the base island and the circuit board 210, thus preventing voids generated during soldering and improving product reliability.

[0050] In this embodiment, the first surface of the chip 110 is provided with a pad 211, and the second surface is mounted on the thermally conductive layer 150. The upper surface of the pin 140 is provided with a solder joint 141, which is electrically connected to the chip 110. Optionally, a wire 143 is provided between the solder joint 141 and the chip 110 to achieve electrical connection. The wire 143 includes, but is not limited to, gold wire, silver wire, copper wire, aluminum wire, alloy wire, or other metal wire. The first molding compound 120 is used to protect the chip 110, the pin 140, and the wire bonding structure.

[0051] A thermally conductive layer 150 is disposed on the side of the second molding compound 130 near the chip 110. That is, the chip 110 is mounted on the thermally conductive layer 150, which improves the thermal conductivity and heat dissipation efficiency of the chip 110. Optionally, an adhesive layer 111 is provided between the thermally conductive layer 150 and the chip 110. The adhesive layer 111 is used to bond and fix the chip 110, and also serves a heat transfer function.

[0052] Optionally, the size of the thermal conductive layer 150 is larger than the size of the chip 110, that is, the chip 110 is completely attached to the thermal conductive layer 150. This is beneficial for conducting heat to the entire back of the chip 110, resulting in high heat transfer efficiency, large heat dissipation area, high heat exchange efficiency, and good heat dissipation performance.

[0053] Optionally, the second molding compound 130 has a through groove 131, and heat dissipation protrusions 133 are formed between adjacent through grooves 131. The through groove 131 facilitates air circulation, improves airflow at the bottom, increases the contact area with air, and improves heat dissipation. The heat dissipation protrusions 133 can increase the heat dissipation area and achieve high heat exchange efficiency.

[0054] Optionally, the surface of the heat sink 133 away from the chip 110 is flush with the surface of the pin 140 away from the chip 110. That is... Figure 1 In the view shown, the bottom surface of the heat sink bump 133 and the bottom surface of the pin 140 are on the same horizontal plane. This configuration allows for better integration when mounting the leadframe package structure 100 onto the board. Figure 3 When pin 140 is soldered to pad 211 on circuit board 210, heat dissipation bump 133 can contact the surface of circuit board 210, which can play a supporting role, prevent solder 220 from collapsing, and help control the height of solder 220, thereby improving the soldering quality. It can be understood that in this embodiment, the surface of the second molding compound 130 is flush with the bottom surface of pin 140, that is, except for forming heat dissipation bump 133, the surface of the second molding compound 130 is also flush with the bottom surface of pin 140.

[0055] Optionally, a step 160 is provided on the side of pin 140 near the second molding compound 130. That is, the inner wall of pin 140 has a step 160. This configuration can improve the bonding force between the second molding compound 130 and pin 140, while reducing the weight of pin 140 and improving heat dissipation performance. Optionally, step 160 includes a first plane 161 and a stop surface 163 connected to the first plane 161. The stop surface 163 is connected to the surface of pin 140 away from chip 110 (the bottom surface of pin 140). The first plane 161 is approximately parallel to the bottom surface of pin 140. Of course, in some embodiments, the first plane 161 can also be an inclined surface or a curved surface; this is not specifically limited here. Similarly, the stop surface 163 can also be a vertical surface or an inclined surface; this is not specifically limited here.

[0056] Optionally, in some implementations, such as Figure 2 As shown, the surface of the second molding compound 130 is approximately flush with the first plane 161, and the heat dissipation bump 133 protrudes from the first plane 161. In other words, the surface of the second molding compound 130 is flush with the step 160 of the pin 140, and there is a certain space distance between the surface of the second molding compound 130 and the bottom surface of the pin 140, which can improve heat dissipation performance, make the gas flow area larger, and improve heat dissipation efficiency. In this embodiment, the heat dissipation bump 133 protrudes from the first plane 161, that is, from the surface of the second molding compound 130, so as to provide support when mounting on the board and control the height of the solder 220.

[0057] Combination Figure 3 This invention also provides a packaging module 200, including a circuit board 210 and a leadframe packaging structure 100 as described in any of the foregoing embodiments, with pins 140 electrically connected to the circuit board 210. Optionally, the circuit board 210 is provided with pads 211, and pins 140 are soldered to pads 211. When the leadframe packaging structure 100 is mounted on the board, only pins 140 and pads 211 need to be soldered, eliminating the need to solder the second molding compound 130, thus simplifying the mounting process and improving soldering efficiency. Furthermore, when pins 140 are soldered to the circuit board 210, heat dissipation bumps 133 contact the circuit board 210, providing support and helping to control the height of the solder 220 between pins 140 and pads 211, preventing solder 220 from collapsing and improving soldering reliability.

[0058] Second Embodiment

[0059] Combination Figure 4 and Figure 5 This invention provides a method for manufacturing a lead frame package structure 100, which is used to manufacture the aforementioned lead frame package structure 100. The method mainly includes the following steps:

[0060] S1: Provide a substrate 170. The substrate 170 may be, but is not limited to, copper, or other metal materials. The substrate 170 has a third surface 171 and a fourth surface 173 disposed opposite to each other, wherein one side of the third surface 171 is used for mounting the chip 110. The third surface 171 is provided with a mounting section and a wire bonding section. The mounting section is used for mounting the chip 110, and the wire bonding section is used for setting solder joints 141. The solder joints 141 and the pads 211 on the chip 110 are connected by wire bonding. The solder joints 141 may be pre-set or fabricated during the packaging process.

[0061] S2: A first groove 175 is formed on the third surface 171 of the substrate 170. The groove can be formed by laser grooving, etching, or machining, and the groove depth is less than the thickness of the substrate 170.

[0062] S3: A thermally conductive layer 150 is formed within the first groove 175. Thermally conductive material is filled into the first groove 175 using methods such as printing or electroplating to form the thermally conductive layer 150. The thermally conductive material includes, but is not limited to, epoxy-based resins or silicone-based resins with added high thermal conductivity materials. High thermal conductivity materials include, but are not limited to, alumina thermally conductive powder or nano-alumina.

[0063] Optionally, solder joints 141 can be electroplated on the wire bonding portion of the substrate 170 using a chemical electroplating process. A protective film is used to protect the areas of the substrate 170 that do not require electroplating, exposing the wire bonding portion. A plating layer is then electroplated onto the copper surface to form solder joints 141. The plating material can be a nickel-gold layer or a tin-silver layer, which can improve the bonding strength during wire bonding.

[0064] S4: Attach chip 110 to thermal conductive layer 150. Use adhesive layer 111 to bond chip 110 to thermal conductive layer 150.

[0065] S5: The substrate 170 and the chip 110 are electrically connected. The chip 110 and the solder joint 141 are electrically connected by wire bonding.

[0066] S6: The molded chip 110 forms the first molded body 120. A molding process, such as injection molding or stencil printing, is used to protect the connected wire bonding structure.

[0067] S7: A second groove 180 is formed on the fourth surface 173 of the substrate 170 to expose the thermally conductive layer 150 and the first molding compound 120. After the first molding compound 120 is baked and cured, the substrate 170 is flipped over with the first molding compound 120 facing down. A protective film is taken to protect the pin 140 area on the substrate 170, which is the area on the fourth surface 173 of the substrate 170 corresponding to the wire bonding portion. Using a chemical etching process, an acidic etching liquid such as sulfuric acid / hydrogen peroxide etching solution is used to etch away the middle part of the substrate 170 from the fourth surface 173 until the middle base island copper material is exposed, forming the first etching groove. The base island is etched away again using chemical agents until the thermally conductive layer 150 is exposed, that is, the bottom of the first etching groove is etched to form the second etching groove. The etching of the exposed base island and the etching of the removed base island can be completed in one etching process. It should be noted that the second groove 180 includes the first etching groove and the second etching groove connected to it. The thermal conductive layer 150 is not affected by chemical etching, so the thermal conductive layer 150 can serve as a stop layer for the etching process, preventing the back of the chip 110 from being over-etched, which would cause the adhesive layer 111 on the back of the chip 110 to delaminate from the first molding compound 120.

[0068] It should be noted that in step S7, after the second groove 180 is formed by etching the middle region of the substrate 170, the remaining portion of the substrate 170, i.e., the remaining pin 140 region, serves as the pin 140 in the lead frame package structure 100. Furthermore, during the formation of the second groove 180, if laser grooving is used, the thermally conductive layer 150 can also serve as a stop layer for laser grooving. Because high thermal conductivity particles are added to the thermally conductive layer 150, energy can be prevented from penetrating the back of the chip 110 during laser grooving, preventing cracks or damage to the back of the chip 110. The laser energy can be selected from carbon dioxide lasers, YAG lasers, etc. Since the penetration depth of laser energy varies in different materials, the thermally conductive layer 150 can serve as a stop layer.

[0069] S8: A second molding compound 130 is formed within the second groove 180. Optionally, liquid molding compound is filled into the second groove 180 by printing or injection molding, and then baked and cured to form the second molding compound 130.

[0070] Optionally, the method also includes:

[0071] S9: A heat dissipation bump 133 is formed on the second molding compound 130. Optionally, a through groove 131 is formed on the second molding compound 130 by etching or laser engraving, and a heat dissipation bump 133 is formed between adjacent through grooves 131.

[0072] Optionally, the heat dissipation bump 133 is flush with the surface of the pin 140. Alternatively, in some embodiments, the second molding compound 130 around the heat dissipation bump 133 can be further removed, making the surface of the second molding compound 130 flush with the step 160 of the pin 140, thus improving heat dissipation. Of course, this is not the only option; the height of the second molding compound 130 can be adjusted flexibly according to the actual situation, and no specific limitation is made here.

[0073] Finally, the product is cut and separated into individual units, completing the manufacturing process. It can be understood that, due to the presence of the second molding compound 130 and the through-slot 131 forming the heat dissipation bump 133, this structure provides a certain buffering effect during the cutting process, preventing burrs on the cutting edges caused by the pulling of the leadframe package structure 100 when cutting the leads 140. Furthermore, the second molding compound 130 can adjust or counteract the warpage of the first molding compound 120, thereby balancing the stress on both sides of the molding compound and improving warpage deformation during the molding process.

[0074] In this embodiment, the first molding compound 120 and the second molding compound 130 are respectively made of high thermal conductivity molding materials, such as epoxy-based resin or silicone-based resin.

[0075] Other parts not mentioned in this embodiment are similar to those in the first embodiment and are not specifically limited here.

[0076] In summary, the lead frame packaging structure 100, the method for manufacturing the lead frame packaging structure 100, and the packaging module 200 provided in the embodiments of the present invention have the following beneficial effects:

[0077] The leadframe package structure 100 provided in this embodiment of the invention has pins 140 located on the outer periphery of the second molding compound 130. This means the second molding compound 130 replaces the traditional base island structure, reducing copper heat dissipation and resulting in a lighter weight. It also avoids the voids that occur when soldering the base island and circuit board 210 in traditional structures, thus improving product reliability. Furthermore, the second molding compound 130 contains a thermally conductive layer 150, which enhances heat dissipation performance and improves heat dissipation efficiency.

[0078] The leadframe package structure 100 fabrication method provided in this embodiment of the invention first forms a thermally conductive layer 150 on one side of the third surface 171 of the substrate 170, and then mounts a chip 110 on the thermally conductive layer 150, which can provide better heat conduction to the back side of the chip 110. A second groove 180 is formed on the fourth surface 173 of the substrate 170 and filled with a second molding compound 130. The second molding compound 130 replaces the base island, providing support and heat dissipation for the chip 110. Simultaneously, during the process of forming the second groove 180, the thermally conductive layer 150 can protect the chip 110, preventing damage. This fabrication method is simple and easy to implement, and is beneficial for improving packaging efficiency and packaging quality.

[0079] The packaging module 200 provided in this embodiment of the invention includes a circuit board 210 and the lead frame packaging structure 100 described above. Since the lead frame packaging structure 100 uses a second molding compound 130 to replace the traditional base island structure, it avoids the phenomenon of voids occurring when the base island and circuit board 210 are soldered in the traditional structure, which is beneficial to improving the reliability of the product. At the same time, the second molding compound 130 is provided with a thermal conductive layer 150, which is beneficial to improving heat dissipation performance and heat dissipation effect.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lead frame packaging structure, characterized in that, include: A chip having a first surface and a second surface disposed opposite to each other; A first molding compound, which encapsulates the chip and is located on one side of the first surface; A second molding compound is disposed on the second surface; a thermally conductive layer is provided inside the second molding compound; the chip is attached to the thermally conductive layer; a through-slot is formed on the second molding compound, and a heat dissipation bump is formed between adjacent through-slots; The pin is located on the outer periphery of the second molding compound and is electrically connected to the chip.

2. The lead frame packaging structure according to claim 1, characterized in that, The thermally conductive layer is disposed on the side of the second molding compound closest to the chip.

3. The lead frame packaging structure according to claim 1, characterized in that, An adhesive layer is provided between the thermal conductive layer and the chip.

4. The lead frame packaging structure according to claim 1, characterized in that, The surface of the heat dissipation bump away from the chip is flush with the surface of the pin away from the chip.

5. The lead frame packaging structure according to claim 1, characterized in that, The pin has a step on the side near the second molding compound.

6. The lead frame packaging structure according to claim 5, characterized in that, The step includes a first plane and a stop surface connected to the first plane, the stop surface being connected to the surface of the pin on the side away from the chip.

7. The lead frame packaging structure according to claim 6, characterized in that, The surface of the second molding compound is flush with the first plane, and the heat dissipation bump protrudes from the first plane.

8. A method for fabricating a lead frame encapsulation structure, characterized in that, The method includes: Provide base materials; A first groove is formed on the third surface of the substrate; A heat-conducting layer is formed within the first groove; A chip is attached to the thermally conductive layer; The substrate and the chip are electrically connected; The chip is encapsulated to form a first encapsulation body; A second groove is formed on the fourth surface of the substrate to expose the thermally conductive layer and the first encapsulation. A second encapsulation is formed within the second groove.

9. The method for fabricating the lead frame encapsulation structure according to claim 8, characterized in that, The method further includes: Heat dissipation bumps are formed on the second molding compound.

10. A packaging module, characterized in that, The device includes a circuit board and a lead frame package structure as described in any one of claims 1 to 7, wherein the pins are electrically connected to the circuit board.

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