Flattening method for ensuring that surface of packaged chip heat dissipation support can be completely exposed

Abstract

The invention discloses a flattening method for ensuring that the surface of a heat dissipation bracket of a packaged chip can be completely exposed, which is characterized by comprising the following steps of: arranging a curing mold with a lower mold I, and fixing all heat dissipation brackets corresponding to respective chips on a substrate by utilizing the curing mold before glue sealing, and the heat dissipation surfaces of the heat dissipation panels of all the fixed heat dissipation brackets are positioned on the packaging surface. The packaging mold has the advantages that during glue sealing, the heat dissipation surfaces of the heat dissipation panels of all the heat dissipation supports can be attached to the lower bottom face of the second upper mold body of the packaging mold, it is guaranteed that glue liquid poured into the glue sealing mold cannot flow to the heat dissipation surfaces of the heat dissipation panels, and the heat dissipation surfaces can dissipate heat normally.

Description

Technical Field

[0001] This invention relates to a flattening method to ensure that the surface of the chip heat sink is fully exposed after packaging, and belongs to the field of chip packaging technology. Background Technology

[0002] One type of chip has a heat sink on its upper surface. The heat sink includes a heat sink panel and thermally conductive leads at one end of the heat sink panel. The upper surface of the heat sink panel has a flat heat dissipation surface. In application, the thermally conductive leads are connected to the chip, and the heat generated by the chip is conducted through the thermally conductive leads to the heat dissipation surface of the heat sink panel for heat dissipation.

[0003] The reason why the aforementioned chips need to be equipped with heat sinks is that all chips require protective encapsulation, focusing on protecting the substrate, the wiring between the substrate and the chip, and the chip itself. The encapsulation method involves sealing the chip and its substrate with adhesive, including sealing the top surface of the chip. Without heat dissipation measures, the heat generated by the encapsulated chip cannot be dissipated, leading to its failure.

[0004] like Figure 2 The diagram shows a chip unit that has been encapsulated. The structure consists of: a substrate 5, a chip 6 disposed on the substrate 5, a wire 601 connecting the chip 6 and the substrate 5, a thermally conductive connecting pin 401 bonded to the substrate 5 by thermally conductive adhesive, a heat dissipation panel 402 supported above the chip 6 by the thermally conductive connecting pin 401, and an encapsulating adhesive 7 that encapsulates all the above components, with only the heat dissipation surface of the heat dissipation panel 402 being fully exposed.

[0005] Current packaging processes involve uniform packaging followed by slitting, which is both convenient for operation and improves packaging efficiency. For example... Figures 1-4 As shown, unified packaging involves placing a substrate 5 with multiple chips 6 arranged on it into a mold cavity formed by the upper mold 801 and the lower mold of the packaging mold 8, followed by potting and cooling. Before entering the mold, the heat sink brackets 4 are individually bonded to the corresponding chips 6. During mold entry, the heat sink panel 402 of each heat sink bracket 4 is placed against the bottom surface of the upper mold 801, and then potting is performed. Since the heat sink panel 402 is placed against the bottom surface of the upper mold, this prevents the heat sink surface of the heat sink bracket 4 from being soaked in, thus exposing the heat sink surface for proper heat dissipation.

[0006] As can be seen above, the bottom surface of the upper mold 801 forms the highest top surface of the encapsulation on the chip 6, referred to in this application as the encapsulation surface 701 of the chip 6. The encapsulation process described above requires that the heat dissipation surface of the heat dissipation panel 402 and the encapsulation surface 701 be on the same plane after encapsulation.

[0007] However, this presents a very difficult problem: ensuring that the heat dissipation surfaces of the heat dissipation panels 402 of all the heat dissipation brackets 4 are on the same plane that contacts the bottom surface of the upper mold during encapsulation. Since the heat dissipation panels 402 of the heat dissipation brackets 4 are supported by thermally conductive connecting pins 401 at one end, the main body of the heat dissipation panels 402 is suspended above the chip 6. Existing technology makes it difficult to guarantee that the heat dissipation surfaces of each heat dissipation panel 402 are on the same plane that contacts the bottom surface of the upper mold when bonding the heat dissipation brackets 4 to the chip 6. When the heat dissipation surface of a certain heat dissipation panel 402 is not aligned with the bottom surface of the upper mold due to misalignment, adhesive will seep into the heat dissipation surface of that heat dissipation panel 402 during the potting process. Once cooled and solidified, it is difficult to remove, causing the heat dissipation surface of that heat dissipation panel 402 to fail to dissipate heat properly during application, ultimately rendering the chip 6 containing that heat dissipation panel 402 unusable. Summary of the Invention

[0008] The technical problem to be solved by the present invention is: how to ensure that the heat dissipation surface of the heat dissipation panel of each heat dissipation bracket is in the same plane that is in contact with the bottom surface of the upper mold during the encapsulation process.

[0009] To address the above problems, the technical solution proposed by this invention is as follows: A method for flattening to ensure that the surface of the chip heat sink bracket is fully exposed after encapsulation is characterized by: setting a curing mold with a lower mold, and using the curing mold to fix all the heat sink brackets and their corresponding chips on the substrate before encapsulation, so that the heat sink surface of the heat sink panel of all the fixed heat sink brackets is on the encapsulation surface.

[0010] Fixing all heat sink brackets to the substrate includes the following steps: S1. Use thermally conductive adhesive to attach the thermally conductive connecting pins of all heat sink brackets to the edges of the corresponding chips on the substrate. S2. Place pads between the heat dissipation panels of the heat sink bracket and the chip to make the heat dissipation surface of each heat sink panel flush with the package surface. S3. Place the substrate curing mold on the surface of the lower mold and make the substrate flat against the surface of the lower mold. S4. Place the curing mold in a temperature chamber and heat it to cure.

[0011] S3 describes making the substrate flat against the surface of the lower mold by setting a cavity inside the lower mold and setting a number of suction holes communicating with the cavity on the surface of the lower mold. After the substrate is placed on the surface of the lower mold, the cavity is evacuated to create a negative pressure, so that the entire substrate is adsorbed and pressed against the surface of the lower mold under the action of negative pressure.

[0012] Furthermore, an air nozzle for evacuating air is provided on one side of the lower mold, which connects to the cavity.

[0013] Furthermore, after the curing mold is placed in the temperature chamber, the cavity of the lower mold is subjected to relay evacuation to maintain the adsorption force that holds the substrate on the lower mold.

[0014] Furthermore, a second air nozzle is installed on the door of the incubator that can connect with the first air nozzle.

[0015] Furthermore, after completing step S3, the heat dissipation surfaces of all heat dissipation panels are forced to be located on the same plane that is flush with the package surface.

[0016] Furthermore, an upper mold with a flat bottom surface is set up for the curing mold. After the upper mold and the lower mold are closed, the bottom surface of the upper mold is flush with the chip's packaging surface. When the mold is closed, the bottom surface of the upper mold is pressed down to force the heat dissipation surfaces of all heat dissipation panels to be pressed against the bottom surface of the upper mold.

[0017] Furthermore, elastic buckles are provided on both sides of the lower mold, so that the upper mold is temporarily fixed by the buckles when the mold is closed.

[0018] Beneficial effects: During encapsulation, the heat dissipation surfaces of all heat dissipation brackets can be in contact with the bottom surface of the upper mold of the encapsulation mold. Compared with the prior art, which makes it difficult to ensure that the heat dissipation surfaces of each heat dissipation panel 402 are in contact with the bottom surface of the upper mold, causing the glue to seep into the heat dissipation surface of the heat dissipation panel 402 during the potting process and thus preventing normal heat dissipation, this application can ensure that the glue poured into the encapsulation mold will not flow onto the heat dissipation surface of the heat dissipation panel, so that the heat dissipation surface can dissipate heat normally, thereby ensuring that the chip has the set normal service life. Attached Figure Description

[0019] Figure 1 This is a three-dimensional schematic diagram of the heat dissipation bracket involved in this application; Figure 2 A cross-sectional view of the chip unit to complete the packaging; Figure 3 This is a cross-sectional view of a chip unit being encapsulated in a packaging mold. The figure shows that the heat dissipation surface of the heat dissipation panel is pressed against the bottom surface of the upper mold, which can prevent the adhesive from seeping into the heat dissipation surface of the heat dissipation panel during encapsulation. Figure 4 This is a cross-sectional view of a chip unit being encapsulated in a packaging mold. The figure shows the heat dissipation surface of the heat dissipation panel being pressed against the bottom surface of the upper mold. After encapsulation, the adhesive does not penetrate into the heat dissipation surface of the heat dissipation panel. Figure 5 This is a three-dimensional schematic diagram of the curing mold and its lower mold as described in Example 1; Figure 6 This is a simplified cross-sectional view of the curing mold and its lower mold as described in Example 1; Figure 7This is a simplified cross-sectional view of the curing mold and its lower mold as described in Embodiment 1, showing the substrate being pressed onto the surface of the lower mold. Figure 8 for Figure 7 A magnified view of a portion of the image; Figure 9 This is a simplified front view diagram of the incubator described in Embodiment 1; Figure 10 This is a three-dimensional schematic diagram of the upper mold 1 as described in Embodiment 2, mainly showing the bottom surface of the upper mold 1; Figure 11 This is a three-dimensional schematic diagram of the cured mold after it is closed, as described in Example 2; Figure 12 This is a cross-sectional view of the solidified mold after mold closing as described in Example 2. The figure shows that the bottom surface of the upper mold is pressed against the heat dissipation surfaces of all heat dissipation panels on the substrate, forcing the heat dissipation surfaces of the heat dissipation panels to be on the same plane. Figure 13 for Figure 12 A magnified view of a portion of the image.

[0020] In the diagram: 1. Curing mold; 101. Upper mold one; 102. Lower mold one; 1021. Cavity; 1022. Suction hole; 1023. Air nozzle one; 103. Elastic buckle; 2. Temperature chamber; 201. Air nozzle two; 3. Pad; 4. Heat dissipation bracket; 401. Thermally conductive connecting foot; 402. Heat dissipation panel; 5. Substrate; 6. Chip; 601. Wire; 7. Encapsulating adhesive; 701. Encapsulation surface; 8. Encapsulation mold; 801. Upper mold two. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: As Figures 5-7 As shown, a flattening method to ensure that the surface of the chip heat sink bracket is fully exposed after encapsulation includes setting up a curing mold 1 with a lower mold 102, and using the curing mold 1 to fix all heat sink brackets 4 corresponding to their respective chips 6 on a substrate 5 before encapsulation, so that the heat dissipation surfaces of the heat dissipation panels 402 of all fixed heat sink brackets 4 are on the encapsulation surface 701. In this way, during encapsulation, the heat dissipation surfaces of the heat dissipation panels 402 of all heat sink brackets 4 can be in contact with the bottom surface of the upper mold 801 of the encapsulation mold 8, ensuring that the adhesive poured into the encapsulation mold does not flow onto the heat dissipation surfaces of the heat dissipation panels 402, so that the heat dissipation surfaces can dissipate heat normally.

[0022] like Figures 7-9 As shown, fixing all the heat sink brackets 4 onto the substrate 5 includes the following steps: S1. Use thermally conductive adhesive to attach all the thermally conductive connecting pins 401 of the heat sink bracket 4 to the edge of the corresponding chip 6 on the substrate 5. S2. Place a pad 3 between the heat dissipation panel 402 of the heat dissipation bracket 4 and the chip 6 so that the heat dissipation surface of each heat dissipation panel 402 is flush with the package surface 701. S3. Place the substrate 5 curing mold 1 on the surface of the lower mold 102 and make the substrate 5 flat against the surface of the lower mold 102. S4. Place the curing mold 1 in the temperature chamber 2 and heat it to cure.

[0023] In step S3, the step of making the substrate 5 flat against the surface of the lower mold 102 is to ensure that the substrate 5 is flat and not warped. If the substrate 5 is warped, the heat dissipation surface of the heat dissipation panel 402 will be tilted, and it will be impossible for the heat dissipation surface of each heat dissipation panel 402 to be on the packaging surface 701 at the same time.

[0024] Furthermore, in step S3, the substrate 5 is flatly attached to the surface of the lower mold 102 by setting a cavity 1021 inside the lower mold 102 and setting a plurality of suction holes 1022 communicating with the cavity 1021 on the surface of the lower mold 102. After the substrate 5 is placed on the surface of the lower mold 102, air is drawn from the cavity 1021 to form a negative pressure in the cavity 1021, so that the entire substrate 5 is adsorbed and pressed onto the surface of the lower mold 102 under the action of negative pressure.

[0025] like Figure 5 As shown, an air nozzle 1023 for evacuating air is provided on one side of the lower mold 102, which connects to the cavity 1021, so as to facilitate connection with the air extraction pipe.

[0026] like Figure 9 As shown, after the curing mold 1 is placed into the temperature chamber 2, the cavity 1021 of the lower mold 102 is subjected to relay evacuation to maintain the adsorption force that holds the substrate 5 on the lower mold 102. For this purpose, an air nozzle 201 that can be connected to the air nozzle 1023 is provided on the door of the temperature chamber 2.

[0027] Example 2: After step S3 is completed, it is still difficult to ensure that the heat dissipation surfaces of all heat dissipation panels 402 are on the same plane that is flush with the encapsulation surface 701. This is because adhesive is used for bonding the thermally conductive connecting pins 401 and placing the pads 3. Whether the thickness of the adhesive is uniform will also affect whether the heat dissipation panels 402 are tilted to a certain extent.

[0028] Therefore, the difference between this embodiment and Embodiment 1 is that, after completing step S3, it is also necessary to force the heat dissipation surfaces of all heat dissipation panels 402 to be located on the same plane that is flush with the encapsulation surface 701.

[0029] Preferably, the upper mold 101 with a flat bottom surface is provided for the curing mold 1. After the upper mold 101 and the lower mold 102 are closed, the bottom surface of the upper mold 101 is flush with the packaging surface 701 of the chip 6. When the mold is closed, the bottom surface of the upper mold 101 is pressed down to force the heat dissipation surfaces of all heat dissipation panels 402 to be pressed against the bottom surface of the upper mold 101.

[0030] Elastic buckles 103 are provided on both sides of the lower mold 102. When the mold is closed, the buckles temporarily fix the upper mold 101.

[0031] The above embodiments are only used to describe the present invention more clearly, and should not be regarded as limiting the scope of protection covered by the present invention. Any equivalent modifications should be regarded as falling within the scope of protection covered by the present invention.

Claims

1. A method for flattening to ensure that the surface of the chip heat sink is fully exposed after packaging, characterized in that: The method includes setting up a curing mold (1) with a lower mold (102), and using the curing mold (1) to fix all heat sink brackets (4) to their respective chips (6) on the substrate (5) before encapsulation, so that the heat dissipation surfaces of the heat dissipation panels (402) of all the fixed heat sink brackets (4) are on the encapsulation surface (701); fixing all the heat sink brackets (4) on the substrate (5) includes the following steps: S1. Use thermally conductive adhesive to attach the thermally conductive connecting pins (401) of all heat sink brackets (4) to the edge of the corresponding chip (6) on the substrate (5); S2. Place a pad (3) between the heat dissipation panel (402) of the heat dissipation bracket (4) and the chip (6) so that the heat dissipation surface of each heat dissipation panel (402) is flush with the package surface (701). S3. Place the substrate (5) curing mold (1) on the surface of the lower mold (102) and make the substrate (5) flat against the surface of the lower mold (102); S4. Place the curing mold (1) in the temperature box (2) and heat it to cure; S3 describes making the substrate (5) flat against the surface of the lower mold (102). A cavity (1021) is set inside the mold of the lower mold (102), and several suction holes (1022) connecting the cavity (1021) are set on the surface of the lower mold (102). After the substrate (5) is placed on the surface of the lower mold (102), air is drawn from the cavity (1021) to form a negative pressure in the cavity (1021), so that the entire substrate (5) is adsorbed and pressed onto the surface of the lower mold (102) under the action of negative pressure.

2. The flattening method according to claim 1 for ensuring that the surface of the chip heat sink bracket is fully exposed after packaging, characterized in that: An air nozzle (1023) for evacuating air is provided on one side of the lower mold (102) and connected to the cavity (1021).

3. The flattening method according to claim 2 for ensuring that the surface of the chip heat sink is fully exposed after packaging, characterized in that: After the curing mold (1) is placed in the temperature chamber (2), the cavity (1021) of the lower mold (102) is subjected to relay evacuation to maintain the adsorption force that adsorbs the substrate (5) onto the lower mold (102).

4. The flattening method according to claim 3 for ensuring that the surface of the chip heat sink is fully exposed after packaging, characterized in that: A second air nozzle (201) that can be connected to the first air nozzle (1023) is installed on the door of the incubator (2).

5. The flattening method according to claim 1 for ensuring that the surface of the chip heat sink is fully exposed after packaging, characterized in that: After completing step S3, the heat dissipation surfaces of all heat dissipation panels (402) are forced to be on the same plane that is flush with the package surface (701).

6. The flattening method according to claim 5 for ensuring that the surface of the chip heat sink is fully exposed after packaging, characterized in that: To solidify the mold (1), an upper mold (101) with a flat bottom surface is set. After the upper mold (101) and the lower mold (102) are closed, the bottom surface of the upper mold (101) is flush with the packaging surface (701) of the chip (6). When the mold is closed, the bottom surface of the upper mold (101) is pressed down to force the heat dissipation surfaces of all heat dissipation panels (402) to be pressed against the bottom surface of the upper mold (101).

7. The flattening method according to claim 6 for ensuring that the surface of the chip heat sink bracket is fully exposed after packaging, characterized in that: Elastic buckles (103) are provided on both sides of the lower mold (102) so that the upper mold (101) is temporarily fixed by the buckles when the mold is closed.

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