Chip packaging structure with cooling fins and packaging method thereof

Abstract

The invention discloses a chip packaging structure with a cooling fin, which enables heat generated in a product to be dissipated into air in an accelerated manner, and the cooling fin can play a role in protecting a chip. The present invention comprises: a substrate; a plurality of chips, wherein each chip is provided with a raised chip bump; a plastic package body; and a heat sink. Each chip is connected to the position of the upper surface of the substrate through chip bump welding, all the chips are flatly laid, the upper surfaces of all the chips are flush with one another, the plastic package body is arranged on the upper surface of the substrate and fills gaps between the chips, the upper surface of the plastic package body is flush with the upper surfaces of the chips, and the upper surface of the plastic package body is arranged on the upper surface of the substrate. The radiating fin covers the upper surface formed by the plastic package body and the chip, and the radiating fin directly or indirectly covers the upper surface of the chip.

Description

Technical Field

[0001] The present invention relates to the technical field of chip packaging, in particular to a chip packaging structure with a heat sink. The present invention also provides a packaging method for the chip packaging structure. Background Art

[0002] Conventional BGA open molding packaging structure, in this type of product, it is necessary to paste more than one chip. The traditional packaging structure usually seals several chips together inside the product or adopts the open molding structure to improve the heat dissipation capacity. This packaging structure technology is simple and mature, and the cost is low. However, as the heat dissipation requirements of the product at the application end are getting higher and higher, this structure has the following shortcomings:

[0003] 1. Although the open molding architecture has enhanced the heat dissipation capacity of the product compared to the cover molding, the effect of only relying on the chip to dissipate the generated heat into the air is still not good enough. First, the heat dissipation area of ​​the chip is not large enough. Second, the chip is exposed to the outside and is relatively fragile. It is not suitable to install a heat sink on the product to assist in heat dissipation.

[0004] 2. When the heat dissipation efficiency cannot meet the demand, the temperature difference between the product overheating and the static temperature will be greater, which is more likely to cause stratification of the product plastic package, substrate, chip, etc. The stratification will make it easier for moisture in the environment to enter the product, thus affecting the product reliability and life;

[0005] 3. The heat generated when the product is working at high load cannot be dissipated in time, which will not only reduce the performance of the chip, but also affect the reliability and life of the product. Summary of the invention

[0006] In view of the above problems, the present invention provides a chip packaging structure with a heat sink, which accelerates the heat generated inside the product to dissipate into the air, and the heat sink can protect the chip.

[0007] A chip packaging structure with a heat sink, characterized in that it comprises:

[0008] substrate;

[0009] A plurality of chips, each chip is provided with a raised chip bump;

[0010] Plastic sealing body;

[0011] and heat sink;

[0012] Each chip is connected to the upper surface of the substrate by chip bump welding, all chips are laid flat, and the upper surfaces of all chips are flush. The plastic package is arranged on the upper surface of the substrate and fills the gaps between chips, and the upper surface of the plastic package is flush with the upper surface of the chip. The heat sink covers the upper surface composed of the plastic package and the chip, and the heat sink directly or indirectly covers the upper surface of the chip.

[0013] It is further characterized by:

[0014] It also includes a heat dissipation adhesive layer, and the upper surface formed by the plastic package body and all the chips is connected to the heat sink through the heat dissipation adhesive layer;

[0015] The outer circumference of the heat sink is slightly smaller than the area corresponding to the plastic package, but the area of ​​the heat sink completely covers the area corresponding to all chips;

[0016] The heat sink is made of copper, aluminum, steel, or aluminum alloy.

[0017] The packaging method of the chip packaging structure with a heat sink is characterized in that after the plastic package body completes the open molding of the chip, an integrated heat sink is mounted on the upper surface of the plastic package body and all the chips.

[0018] It includes the following specific steps:

[0019] S1. Confirm the product size according to the design drawings and prepare the entire heat sink in advance according to the requirements;

[0020] S2, the chip is thinned and sliced ​​to a set thickness in the thinning process, and the FC flip-chip mounting process is to mount the thinned and sliced ​​chip on the substrate and reflow soldering;

[0021] S3, bottom filling process, filling the bottom of the chip to form bottom filling glue to protect the chip bump area;

[0022] S4, plastic encapsulation, after which the upper surface of the chip is exposed, and the plastic encapsulation body and the chip are arranged flush with each other;

[0023] S5, mount the heat sink on the open molding products;

[0024] S6, ball planting, planting solder balls on the pad on the back of the substrate.

[0025] It is further characterized by:

[0026] In step S1, the design thickness of the heat sink is designed according to the substrate thickness, chip bump height, chip thinning thickness, and product required thickness. The thickness of the heat sink is 100um to 800μm; the length and width of the heat sink are shrunk by 200 to 500μm respectively according to the length and width of the product package size;

[0027] The material of the heat sink is preferably copper or aluminum alloy. Heat sinks made of copper or aluminum alloy have their own advantages and disadvantages. Copper has good thermal conductivity but is heavy. Aluminum alloy has lower cost and lighter weight, but its disadvantage is that its thermal conductivity is worse than that of copper.

[0028] In step S4, the height difference of the four corners of each group of chips is controlled within 10um, so the open molding packaging method is directly adopted without the need to use the cover molding and then the glue grinding method;

[0029] In step S5, the commonly used model 4450 heat dissipation adhesive is selected, the heat dissipation tape is sticky, the main components of the heat dissipation adhesive are silicon dioxide and resin, the coating thickness of the heat dissipation adhesive layer is 20-30um, after the heat dissipation adhesive layer is applied, the heat sink is attached to ensure that each side of the heat sink is retracted to the corresponding side of the plastic package body.

[0030] After adopting the structure of the present invention, an integrated heat sink is mounted on the basis of the open molding structure formed by the plastic package body and all chips, which can not only enhance the heat dissipation capacity of the product itself, but also protect the chips exposed to the outside of the open molding. The product can then be used in conjunction with auxiliary heat dissipation methods such as an external heat sink to enable the product to dissipate heat more quickly, greatly improving the performance and service life of the product under high load. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic cross-sectional view of the structure of the present invention;

[0032] Figure 2 It is a top view of the arrangement of the chip and the substrate of the present invention when it is not packaged;

[0033] Figure 3 is a process flow chart corresponding to the method of the present invention (step S1 is not shown);

[0034] The names corresponding to the serial numbers in the figure are as follows:

[0035] Substrate 1, plastic package 2, chip 3, bottom filling glue 4, chip bump 5, solder ball 6, heat dissipation glue layer 7, heat sink 8. DETAILED DESCRIPTION

[0036] A chip packaging structure with a heat sink, see Figure 1-Figure 2, which comprises a substrate 1, a plurality of chips 3, a plastic package 2, and a heat sink 8; each chip 3 is provided with a raised chip bump 5;

[0037] Each chip 3 is welded to the upper surface of the substrate 1 through a chip bump 5, and a bottom filling glue 4 is provided after welding. All chips 3 are arranged flat, and the upper surfaces of all chips 3 are arranged flush. The plastic package 2 is arranged on the upper surface of the substrate 1 and fills the gaps between the chips 3, and the upper surface of the plastic package 2 is arranged flush with the upper surface of the chip 3. The heat sink 8 covers the upper surface composed of the plastic package 2 and the chip 3, and the heat sink 8 directly or indirectly covers the upper surface of the chip.

[0038] In specific implementation, it also includes a heat dissipation adhesive layer 7 , and the upper surface formed by the combination of the plastic package body 2 and all the chips 3 is connected to the heat sink 8 through the heat dissipation adhesive layer 7 .

[0039] During specific implementation, a plurality of solder balls 6 are further disposed on the back side of the substrate.

[0040] In specific implementation, the outer circumference of the heat sink 8 is slightly smaller than the surface area corresponding to the plastic package body 2, but the surface area of ​​the heat sink 8 completely covers the surface area corresponding to all chips; the heat sink 8 is made of copper, aluminum, steel, or aluminum alloy.

[0041] In a specific embodiment, the number of chips is two.

[0042] The packaging method of the chip packaging structure with a heat sink in a specific embodiment is as follows: after the plastic package 2 completes the open molding packaging of the two chips 3 , an integrated heat sink 8 is mounted on the upper surface of the plastic package 2 and the two chips 3 .

[0043] It includes the following specific steps:

[0044] S1. Confirm the size of the product according to the design drawing and prepare the entire heat sink 8 in advance according to the requirements;

[0045] The design thickness of the heat sink 8 can be designed according to the thickness of the substrate 1, the height of the chip bump 5, the thinning thickness of the chip 2, the required thickness of the product, etc. Considering that the heat sink 8 needs to have a certain strength, the thickness of the heat sink 8 is set to 400um in the present invention, and the length and width of the heat sink 8 are determined according to the length and width of the product packaging size ( Figure 2 L1, L2), the heat sink size in the present invention is designed to be 300um smaller in length and width than the product size;

[0046] There are many materials for the heat sink 8, generally copper, aluminum, steel, and aluminum alloy. Considering the thermal conductivity and price, the heat sink 8 is mostly made of copper or aluminum alloy. Heat sinks made of copper and aluminum alloy have their own advantages and disadvantages. Copper has good thermal conductivity but is heavy. Aluminum alloy has lower cost and lighter weight, but its disadvantage is that its thermal conductivity is worse than copper. The specific product can reasonably select the heat sink material according to the application scenario and heat dissipation requirements. In the present invention, the heat sink 8 is made of copper.

[0047] S2, the chip 3 is thinned and diced to 250um in the thinning process, and the FC flip-chip mounting process is to mount the thinned and diced chip 3 on the substrate 1 and reflow soldering;

[0048] S3, bottom filling process, filling the bottom of the chip with bottom filling glue 4 to protect the chip bump area;

[0049] S4, plastic encapsulation, after which the upper surface of the chip is exposed, and the height difference of the four corners of each group of chips 3 is controlled within 10um, so the plastic encapsulation body 2 is obtained directly by using the open molding packaging method, without using the cover molding and then grinding the glue method;

[0050] S5. Mount the heat sink on the product that has been open molded. The commonly used heat sink adhesive is 4450. The heat sink adhesive tape is sticky. The main components of the heat sink adhesive are silicon dioxide and resin. The thickness of the heat sink adhesive layer is 20-30um. After applying the heat sink adhesive layer 7, attach the heat sink 8 to ensure that each side of the heat sink 8 is indented to the corresponding side of the plastic package body 2.

[0051] S6, ball planting, planting solder ball 6 on the pad on the back side of the substrate.

[0052] After adopting the present invention, an integrated heat sink is mounted on the basis of the open molding structure formed by the plastic package body and all chips, which can not only enhance the heat dissipation capacity of the product itself, but also protect the chips exposed to the outside of the open molding. The product can then be used in conjunction with auxiliary heat dissipation methods such as an external radiator to enable the product to dissipate heat more quickly, greatly improving the performance and service life of the product under high load.

[0053] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0054] In addition, it should be understood that although the present 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 embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A chip packaging structure with a heat sink, characterized in that: It includes: substrate; A plurality of chips, each chip is provided with a raised chip bump; Plastic sealing body; and heat sink; Each chip is connected to the upper surface of the substrate by chip bump welding, all chips are laid flat, and the upper surfaces of all chips are flush. The plastic package is arranged on the upper surface of the substrate and fills the gaps between chips, and the upper surface of the plastic package is flush with the upper surface of the chip. The heat sink covers the upper surface composed of the plastic package and the chip, and the heat sink directly or indirectly covers the upper surface of the chip.

2. The chip packaging structure with a heat sink according to claim 1, characterized in that: It also includes a heat dissipation adhesive layer, and the upper surface formed by the plastic package body and all the chips is connected to the heat sink through the heat dissipation adhesive layer.

3. A chip packaging structure with a heat sink according to claim 1 or 2, characterized in that: The outer circumference size of the heat sink is slightly smaller than the surface area corresponding to the plastic package body, but the surface area of ​​the heat sink completely covers the surface area corresponding to all chips.

4. The chip packaging structure with a heat sink according to claim 1, characterized in that: The heat sink is made of copper, aluminum, steel, or aluminum alloy.

5. A packaging method for a chip packaging structure with a heat sink, which is used to manufacture a chip packaging structure with a heat sink as claimed in any one of claims 1 to 4, characterized in that: After the plastic package completes the Openmolding packaging of the chip, an integrated heat sink is mounted on the upper surface of the plastic package and all the chips.

6. The packaging method of the chip packaging structure with a heat sink according to claim 5, characterized in that: It includes the following specific steps: S1. Confirm the product size according to the design drawings and prepare the entire heat sink in advance according to the requirements; S2, the chip is thinned and sliced ​​to a set thickness in the thinning process, and the FC flip-chip mounting process is to mount the thinned and sliced ​​chip on the substrate and reflow soldering; S3, bottom filling process, filling the bottom of the chip to form bottom filling glue to protect the chip bump area; S4, plastic encapsulation, after which the upper surface of the chip is exposed, and the plastic encapsulation body and the chip are arranged flush with each other; S5, mount the heat sink on the open molding products; S6, ball planting, planting solder balls on the pad on the back of the substrate.

7. The packaging method of the chip packaging structure with a heat sink according to claim 6, characterized in that: In step S1, the design thickness of the heat sink is designed according to the substrate thickness, chip bump height, chip thinning thickness, and product required thickness. The thickness of the heat sink is 100um to 800μm; the length and width of the heat sink are shrunk by 200 to 500μm respectively according to the length and width of the product package size.

8. The packaging method of the chip packaging structure with a heat sink according to claim 6, characterized in that: The heat sink is made of copper or aluminum alloy.

9. The packaging method of the chip packaging structure with a heat sink according to claim 6, characterized in that: In step S4, the height difference of the four corners of each group of chips is controlled within 10 um, so the open molding packaging method is directly adopted.

10. The packaging method of the chip packaging structure with a heat sink according to claim 6, characterized in that: In step S5, the heat dissipation adhesive is selected as model 4450, the heat dissipation tape is sticky, the main components of the heat dissipation adhesive are silicon dioxide and resin, the coating thickness of the heat dissipation adhesive layer is 20-30um, after the heat dissipation adhesive layer is applied, the heat sink is attached to ensure that each side of the heat sink is retracted to the corresponding side of the plastic package body.

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