Inductive superposition welding structure and corresponding assembly process

Abstract

The application discloses an inductor superposition welding structure, which arranges an inductor and an IC chip and a substrate in a high direction to reduce the area of the substrate and improve the heat dissipation performance of the inductor and the IC chip. The inductor is a long pin inductor, which comprises an inductor body, a lower protruding long pin and a heat dissipation electrode. The shell part of the inductor body is made of a heat conductive material, the periphery of the inductor body is provided with the lower protruding long pin, and the lower surface of the central area of the inductor body is provided with a plurality of heat dissipation electrodes. The main substrate comprises a substrate body, pin contact points at the periphery and chip connection contact points at the central area. The pre-made chip comprises a chip body, a first substrate, a heat conductive layer, a heat dissipation cover and a pre-welding layer.

Description

Technical Field

[0001] This invention relates to the technical field of chip packaging, specifically to an inductor stacking and welding structure. This invention also provides an inductor stacking and welding assembly process. Background Technology

[0002] Existing FCCSP packaging structures such as Figure 1 As shown, this is the basic packaging structure of power module products. Because inductors are used, the space layout of the package's lateral area is increased. However, the bonding force between the magnetic molding compound of the inductor itself and the molding compound of the package is not very good. During the customer's reliability testing phase, delamination was found. At the same time, since the inductor and the chip are packaged in the molding compound, the heat generated when a large current passes through the chip and the inductor during operation cannot be dissipated in time, which will trigger the motherboard's overheat protection mechanism and restart the system. This also leads to a decrease in the electron mobility inside the chip, affecting the computing speed and processing power. Excessive chip temperature will also accelerate the internal chemical reaction of the molding compound, leading to premature product failure. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides an inductor stacking and welding structure, which stacks inductors, IC chips, and substrates in the height direction, reducing the substrate area and improving the heat dissipation performance of the inductors and IC chips.

[0004] An inductor superimposed welding structure, characterized in that it comprises:

[0005] An inductor, which is a long-lead inductor, includes an inductor body, a long protruding lead, and heat dissipation electrodes. The housing part of the inductor body is made of thermally conductive material. The long protruding lead is provided in the peripheral area of ​​the inductor body. Several heat dissipation electrodes are provided on the lower surface of the central area of ​​the inductor body.

[0006] The main substrate includes a substrate body, pin contacts located on the periphery, and chip connection contacts located in the central region.

[0007] The chip includes a chip body, a first substrate, a thermally conductive layer, a heat sink cover, and a pre-welded layer. The upper surface of the chip body is provided with a convex thermally conductive layer, which is distributed in the heat concentration area of ​​the chip body. The upper surface of the thermally conductive layer is fixedly connected to the heat sink cover, and the upper surface of the heat sink cover is pre-welded. The contacts on the lower surface of the chip body are welded to the corresponding contacts of the first substrate, and the lower surface of the first substrate is provided with exposed contacts at positions corresponding to the contacts of the chip body. After the pre-made chip is encapsulated with molding compound, the convex pre-welded layer is exposed, and the lower surface of the first substrate is exposed.

[0008] The outer contour shape of the inductor covers the surface area of ​​the prefabricated chip. The convex long lead of the inductor is soldered to the upper surface lead contact of the main substrate. The corresponding contact on the lower surface of the first substrate of the prefabricated chip is soldered to the chip connection contact of the main substrate. The pre-soldering layer of the prefabricated chip is soldered to the corresponding heat dissipation electrode of the inductor.

[0009] Its further features are:

[0010] The height of the protruding long pin is greater than the height of the prefabricated chip, and the height of the protruding long pin ensures reliable and stable soldering of the prefabricated chip, the main substrate, and the inductor.

[0011] The long, protruding pins of the inductor are soldered to the pin contacts on the upper surface of the main substrate using solder paste. The corresponding contacts on the lower surface of the first substrate of the prefabricated chip are soldered to the chip connection contacts on the main substrate using solder paste. The pre-soldering layer of the prefabricated chip is soldered to the corresponding heat dissipation electrode of the inductor using solder paste.

[0012] Other components are also mounted on the main substrate. The solder paste used to mount the other components and prefabricated chips on the upper surface of the main substrate is high-temperature solder paste, thereby reducing the risk of solder bridging during secondary reflow soldering.

[0013] The thermally conductive layer is specifically a thermally conductive silver paste layer;

[0014] The outer periphery of the upper surface of the prefabricated chip is coated with thermosetting adhesive, thereby coating the outer periphery of the pre-welding layer of the prefabricated chip with a thermosetting adhesive encapsulation layer, ensuring the reliability and stability of the welding area.

[0015] An inductor stacking and welding assembly process, characterized by comprising the following steps:

[0016] S1. Assemble pre-fabricated chips;

[0017] S101. Components and chip bodies are attached to the first substrate;

[0018] S102. Apply a thermally conductive layer to the upper surface of the chip body and attach a heat dissipation cover to the heat concentration area.

[0019] S103. The first substrate and the chip body are packaged, and then the plastic encapsulation material on the heat sink and the upper surface of the chip body is ground out through the grinding process to achieve the required chip thickness.

[0020] S104. Continue to brush tin onto the surface of the heat sink to make a pre-soldering layer, print information, cut into individual chips, test and select good products to obtain pre-made chips.

[0021] S2. Attach components and pre-fabricated chips to the main substrate;

[0022] S3. Weld and assemble the inductor, main substrate, and pre-fabricated chip.

[0023] Its further features are:

[0024] In step S102, thermally conductive silver paste is applied to the upper surface of the chip body using a paste application device to form a thermally conductive layer, and a heat dissipation cover is then attached to the upper surface of the thermally conductive silver paste.

[0025] In step S103, because the grinding process involves water cleaning, baking is required within 2-4 hours after the water cleaning is completed to remove moisture and prevent the ground copper pillar from oxidizing and discoloring.

[0026] In step S2, components and prefabricated chips are attached to the main substrate using high-temperature solder paste. High-temperature solder paste is used to reduce the risk of solder bridging during secondary reflow soldering.

[0027] In step S3, thermosetting adhesive is applied to the surface of the IC. The adhesive layer is formed in one step during reflow soldering. Solder paste is applied to the pre-made chip and soldered to the heat dissipation electrode at the bottom of the inductor. Solder paste is applied to the pads of the substrate to position and attach the inductor. Finally, the chip is cut into individual pieces to obtain the finished product. The thermosetting adhesive is used to fix the inductor and prevent it from shifting or falling off during product use.

[0028] By adopting the above technical solution, the inductor, IC chip, and substrate are stacked in the height direction. Thermal adhesive and metal heat sink are used to transfer the internal temperature of the product to the inductor shell. External heat sinks are used to increase airflow, enabling the product to dissipate heat quickly. During the packaging process, there is no need to consider the distribution of the inductor on the substrate. Plastic encapsulation does not need to consider the poor bonding rate with the inductor, which may cause internal bonding delamination due to thermal shock during product reliability testing. This increases product reliability and improves heat dissipation performance. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the main view structure of the present invention;

[0030] Figure 2 A front view of an inductor applicable to the present invention;

[0031] Figure 3 This is a flowchart of the assembly process of the present invention;

[0032] The names corresponding to the serial numbers in the diagram are as follows:

[0033] Inductor 10, Inductor body 11, Long protruding pin 12, Heat dissipation electrode 13, Main substrate 20, Substrate body 21, Pin contact 22, Chip connection contact 23, Pre-fabricated chip 30, Chip body 31, First substrate 32, Thermal conductive layer 33, Heat dissipation cover 34, Pre-soldering layer 35, Molding compound 36, Solder paste 40, High-temperature solder paste 50, Components 60, Thermosetting adhesive 70. Detailed Implementation

[0034] An inductor superimposed welding structure is characterized in that it includes an inductor 10, a main substrate 20, and a pre-fabricated chip 30.

[0035] Inductor 10 is a long-lead inductor, which includes an inductor body 11, a long, protruding lead 12, and a heat dissipation electrode 13. The shell of the inductor body 11 is made of a thermally conductive material. In a specific implementation, the shell of the inductor body 11 contains a metallic component, namely, iron oxide powder—Fe3O4. The outer periphery of the inductor body 11 is provided with the long, protruding lead 12, and the lower surface of the central region of the inductor body 11 is provided with several heat dissipation electrodes 13.

[0036] The main substrate 20 includes a substrate body 21, pin contacts 22 located on the periphery, and chip connection contacts 23 located in the central region;

[0037] The prefabricated chip 30 includes a chip body 31, a first substrate 32, a thermally conductive layer 33, a heat sink 34, and a pre-welded layer 35. The upper surface of the chip body 31 is provided with an upwardly protruding thermally conductive layer 33, which is distributed in the heat concentration area of ​​the chip body. The upper surface of the thermally conductive layer 33 is fixedly connected to the heat sink 34, and the upper surface of the heat sink 34 is pre-welded with the pre-welded layer 35. The contacts on the lower surface of the chip body 31 are welded to the corresponding contacts of the first substrate 32, and the lower surface of the first substrate 32 is provided with exposed contacts corresponding to the contacts of the chip body 31. After the prefabricated chip 30 is encapsulated by the molding compound 36, the pre-welded layer 35 is exposed upwardly, and the lower surface of the first substrate 32 is exposed.

[0038] In a specific implementation, the outer contour shape of the inductor 10 covers the surface area of ​​the prefabricated chip 30. The protruding long pin 12 of the inductor 10 is soldered to the upper surface pin contact 22 of the main substrate 20 through solder paste 40. The corresponding contact on the lower surface of the first substrate 32 of the prefabricated chip 30 is soldered to the chip connection contact 23 of the main substrate 20 through high temperature solder paste 50. The pre-soldering layer 35 of the prefabricated chip 30 is soldered to the corresponding heat dissipation electrode 13 of the inductor 10 through solder paste 40.

[0039] In practice, the height of the protruding long pin 12 is greater than the height of the prefabricated chip 30. The height of the protruding long pin 12 ensures reliable and stable soldering of the prefabricated chip 30, the main substrate 20, and the inductor 10.

[0040] Other components 60 are also mounted on the main substrate 20. The material used for mounting the other components 60 and the pre-fabricated chip 30 on the upper surface of the main substrate 20 is high-temperature solder paste 50, thereby reducing the risk of solder bridging during secondary reflow soldering.

[0041] The thermally conductive layer 33 is specifically a thermally conductive silver paste layer;

[0042] The outer periphery of the upper surface of the prefabricated chip 30 is coated with thermosetting adhesive 70. In addition to bonding, the thermosetting adhesive also forms a thermosetting adhesive encapsulation layer on the outer periphery of the pre-welding layer of the prefabricated chip 30, ensuring the reliability and stability of the welding area.

[0043] An inductor stacking welding assembly process, see Figure 2 It includes the following steps:

[0044] S1. Assemble pre-fabricated chips;

[0045] S101, Attach the components and chip body 31 onto the first substrate 32;

[0046] S102. A thermally conductive layer 33 is applied to the upper surface of the chip body 31, and a heat sink 34 is attached to the heat concentration area. Thermally conductive silver paste is applied to the upper surface of the chip body 31 using a glue application device to form a thermally conductive layer 33, and a heat sink 34 is attached to the upper surface of the thermally conductive silver paste.

[0047] S103. The first substrate 32 and the chip body 31 are packaged. Then, the plastic encapsulation material on the heat sink 34 and the upper surface of the chip body 31 is ground out through the grinding process to achieve the required chip thickness. Because the grinding process involves water cleaning, it needs to be baked within 2-4 hours after the water cleaning is completed to remove moisture and prevent the ground copper pillars from oxidizing and discoloring.

[0048] S104. Continue to brush tin onto the surface of the heat sink 34 to make a pre-soldering layer 35. After printing information, cut it into a single chip, test and select good products to obtain pre-made chip 30.

[0049] S2. Components 60 and prefabricated chips 30 are attached to the main substrate 20. Components 60 and prefabricated chips 30 are attached to the main substrate 20 using high-temperature solder paste 50. High-temperature solder paste 50 reduces the risk of solder bridging during secondary reflow soldering.

[0050] S3. Weld and assemble the inductor 10, main substrate 20, and prefabricated chip 30. Apply thermosetting adhesive 70 to the outer periphery of the upper surface of the prefabricated chip 30. The adhesive layer is formed in one step during reflow soldering. Apply solder paste 40 to the prefabricated chip 30 and solder it to the heat dissipation electrode 13 at the bottom of the inductor. Apply solder paste to the pin contacts 22 of the substrate and position and attach the inductor 10. Finally, cut the individual chips to obtain the finished product. The thermosetting adhesive 70 is used to fix the inductor and prevent the inductor from shifting or falling off during product use.

[0051] By stacking inductors, IC chips, and substrates along their height, and using thermal adhesive and metal heat sinks, the internal temperature of the product is transferred to the inductor casing. External heat sinks are used to increase airflow, enabling the product to dissipate heat quickly. During the packaging process, there is no need to consider the distribution of the inductor on the substrate. Plastic encapsulation does not require consideration of poor bonding with the inductor, which could lead to internal delamination due to thermal shock during product reliability testing. This increases product reliability and improves heat dissipation performance.

[0052] It will be apparent to those skilled in the art that the present 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 its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0053] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An inductor superimposed welding structure, characterized in that, It includes: An inductor, which is a long-lead inductor, includes an inductor body, a long protruding lead, and heat dissipation electrodes. The housing part of the inductor body is made of thermally conductive material. The long protruding lead is provided in the peripheral area of ​​the inductor body. Several heat dissipation electrodes are provided on the lower surface of the central area of ​​the inductor body. The main substrate includes a substrate body, pin contacts located on the periphery, and chip connection contacts located in the central region. The chip includes a chip body, a first substrate, a thermally conductive layer, a heat sink cover, and a pre-welded layer. The upper surface of the chip body is provided with a convex thermally conductive layer, which is distributed in the heat concentration area of ​​the chip body. The upper surface of the thermally conductive layer is fixedly connected to the heat sink cover, and the upper surface of the heat sink cover is pre-welded. The contacts on the lower surface of the chip body are welded to the corresponding contacts of the first substrate, and the lower surface of the first substrate is provided with exposed contacts at positions corresponding to the contacts of the chip body. After the pre-made chip is encapsulated with molding compound, the convex pre-welded layer is exposed, and the lower surface of the first substrate is exposed. The outer contour shape of the inductor covers the surface area of ​​the prefabricated chip. The convex long lead of the inductor is soldered to the upper surface lead contact of the main substrate. The corresponding contact on the lower surface of the first substrate of the prefabricated chip is soldered to the chip connection contact of the main substrate. The pre-soldering layer of the prefabricated chip is soldered to the corresponding heat dissipation electrode of the inductor.

2. The inductor superimposed welding structure according to claim 1, characterized in that: The height of the protruding long pin is greater than the height of the prefabricated chip.

3. The inductor superimposed welding structure according to claim 1, characterized in that: The long, protruding pins of the inductor are soldered to the upper surface pin contacts of the main substrate using solder paste. The corresponding contacts on the lower surface of the first substrate of the prefabricated chip are soldered to the chip connection contacts of the main substrate using solder paste. The pre-soldering layer of the prefabricated chip is soldered to the corresponding heat dissipation electrode of the inductor using solder paste.

4. The inductor superimposed welding structure according to claim 1, characterized in that: Other components are also mounted on the main substrate. The solder paste used to mount the other components and prefabricated chips on the upper surface of the main substrate is high-temperature solder paste, thereby reducing the risk of solder bridging during secondary reflow soldering.

5. The inductor superimposed welding structure according to claim 1, characterized in that: The outer periphery of the upper surface of the prefabricated chip is coated with thermosetting adhesive.

6. An inductor superimposed welding assembly process corresponding to an inductor superimposed welding structure as described in any one of claims 1-5, characterized in that, It includes the following steps: S1. Assemble pre-fabricated chips; S101. Components and chip bodies are attached to the first substrate; S102. Apply a thermally conductive layer to the upper surface of the chip body and attach a heat dissipation cover to the heat concentration area. S103. The first substrate and the chip body are packaged, and then the plastic encapsulation material on the heat sink and the upper surface of the chip body is ground out through the grinding process to achieve the required chip thickness. S104. Continue to brush tin onto the surface of the heat sink to make a pre-soldering layer, print information, cut into individual chips, test and select good products to obtain pre-made chips. S2. Attach components and pre-fabricated chips to the main substrate; S3. Weld and assemble the inductor, main substrate, and pre-fabricated chip.

7. The inductor superposition welding assembly process according to claim 6, characterized in that: In step S102, thermally conductive silver paste is applied to the upper surface of the chip body using a paste application device to form a thermally conductive layer, and a heat sink is then attached to the upper surface of the thermally conductive silver paste.

8. The inductor superposition welding assembly process according to claim 6, characterized in that: In step S103, because the grinding process involves water cleaning, baking is required within 2-4 hours after the water cleaning is completed to remove moisture and prevent the ground copper pillar from oxidizing and discoloring.

9. The inductor superposition welding assembly process according to claim 6, characterized in that: In step S2, components and prefabricated chips are attached to the main substrate using high-temperature solder paste. The high-temperature solder paste is used to reduce the risk of solder bridging during the secondary reflow soldering.

10. The inductor superposition welding assembly process according to claim 6, characterized in that: In step S3, thermosetting adhesive is applied to the surface of the IC. The adhesive layer is formed in one step during reflow soldering. Solder paste is applied to the pre-made chip and soldered to the heat dissipation electrode at the bottom of the inductor. Solder paste is applied to the pads of the substrate to position and attach the inductor. Finally, the chip is cut into individual pieces to obtain the finished product. The thermosetting adhesive is used to fix the inductor and prevent it from shifting or falling off during product use.

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