Chip packaging method and chip packaging structure

Abstract

The embodiment of the invention provides a chip packaging method and a chip packaging structure. The method comprises the following steps: providing a chip, a substrate, a heat dissipation cover plate and a heat conduction metal sheet; wherein a gas groove is formed in the surface of the heat-conducting metal sheet; the front face of the chip is fixed to the first surface of the substrate, the heat conduction metal sheet is arranged on the back face of the chip, the heat dissipation cover plate is fixed to the first surface of the substrate and arranged on the surface, away from the chip, of the heat conduction metal sheet, and a to-be-welded unit is obtained; the gas groove is filled with weld-aid gas; and the heat dissipation cover plate is welded and fixed on the back surface of the chip through the heat conduction metal sheet. According to the embodiment of the invention, the surface of the heat-conducting metal sheet and the surface of the gold-plated layer of the heat-dissipating cover plate are provided with the grooves, so that welding-aid gas can enter the grooves to be in full contact with the welding surface, the problem that formic acid gas is not easy to enter the welding surface is solved, cavities in the welding surface are avoided, and the heat-dissipating efficiency of the packaged chip is ensured.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the field of semiconductor packaging technology, and specifically relate to a chip packaging method and a chip packaging structure. Background Art

[0002] In order to increase the heat dissipation performance, FCBGA (Flip Chip Ball Grid Array) or FCLGA (Flip Chip Land Grid Array) products usually use indium sheets or other thermally conductive metals to weld the metal on the chip and the metal on the heat dissipation cover together through solder resist to achieve the heat dissipation function. However, during high-temperature welding, the flux evaporates, and in the vacuum state, the liquid metal is easily taken out with the flux gas, which causes abnormal voids on the thermally conductive metal welding surface.

[0003] Currently, formic acid gas is used to replace flux, but formic acid gas is not easy to enter the welding interface between heat dissipation metal and chip and gold plating, resulting in unsatisfactory welding effect. Summary of the invention

[0004] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a chip packaging method and a chip packaging structure.

[0005] One aspect of the present disclosure provides a chip packaging method, the method comprising:

[0006] A chip, a substrate, a heat dissipation cover plate and a heat-conducting metal sheet are provided; wherein a gas groove is provided on the surface of the heat-conducting metal sheet;

[0007] The front side of the chip is fixed to the first surface of the substrate, the heat-conducting metal sheet is arranged on the back side of the chip, and the heat-dissipating cover plate is fixed to the first surface of the substrate and arranged on the surface of the heat-conducting metal sheet away from the chip to obtain a unit to be welded;

[0008] Filling the gas groove with flux gas;

[0009] The heat dissipation cover plate is fixed to the back side of the chip by welding through the heat conductive metal sheet.

[0010] Furthermore, a gas groove is provided on a surface of the heat-conducting metal sheet opposite to the back side of the chip and on a surface of the heat-dissipating cover plate.

[0011] Furthermore, the heat dissipation cover plate is provided with a first gold-plated layer on a surface opposite to the heat-conducting metal sheet;

[0012] The method of fixing the heat dissipation cover plate to the first surface of the substrate and arranging the heat dissipation cover plate on the surface of the heat conductive metal sheet facing away from the chip comprises:

[0013] The heat dissipation cover plate is fixed to the first surface of the substrate, and the first gold-plated layer is arranged on the surface of the heat-conducting metal sheet away from the chip.

[0014] Furthermore, a gas groove is provided on a surface of the first gold-plated layer relative to the heat-conducting metal sheet.

[0015] Furthermore, the back side of the chip has a second gold-plated layer;

[0016] The step of arranging the heat-conducting metal sheet on the back side of the chip comprises:

[0017] The heat-conducting metal sheet is arranged on the second gold-plated layer on the back side of the chip.

[0018] Optionally, the flux gas is formic acid gas.

[0019] Further, the step of filling the gas groove with flux gas comprises:

[0020] Placing the unit to be welded in a formic acid reflow furnace; wherein the formic acid reflow furnace has formic acid gas;

[0021] The pressure in the formic acid reflow furnace is reduced to below atmospheric pressure, so that the formic acid gas fills the gas recess.

[0022] Further, the step of reducing the pressure in the formic acid reflux furnace to below atmospheric pressure comprises:

[0023] The pressure in the formic acid reflux furnace is pumped down to 3 kPa to 20 kPa.

[0024] Optionally, the thermally conductive metal sheet is an indium sheet.

[0025] Optionally, fixing the heat dissipation cover plate to the first surface of the substrate includes:

[0026] Attaching the heat dissipation cover plate to the first surface of the substrate by adhesive;

[0027] The adhesive is pre-baked to solidify the adhesive; the pre-baking temperature is lower than the melting point of the heat-conducting metal sheet.

[0028] Optionally, the depth of the gas groove is 1 μm to 10 μm.

[0029] Another aspect of the present disclosure provides a chip packaging structure, which is manufactured using the chip packaging method described above.

[0030] A chip packaging method and a chip packaging structure of the disclosed embodiments make grooves on the surface of a heat-conducting metal sheet so that the flux gas can enter the grooves and fully contact the welding surface, thereby solving the problem that the flux gas is difficult to enter the welding surface. The flux gas can effectively remove oxidation, avoid the appearance of voids on the welding surface, and ensure the heat dissipation efficiency of the packaged chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a chip packaging method according to an embodiment of the present disclosure;

[0032] Figure 2 FIG. 4 is a process diagram of a chip packaging method according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0034] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0035] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0036] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another component. Therefore, the first component discussed below can be referred to as the second component without departing from the teachings of the concepts of the present disclosure. As used in this disclosure, the term "and / or" includes any one of the associated listed items and all combinations of one or more.

[0037] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present disclosure, and therefore cannot be used to limit the protection scope of the present disclosure.

[0038] like Figure 1 As shown, an embodiment of the present disclosure provides a chip packaging method, the method comprising:

[0039] Step S1, providing a chip, a substrate, a heat dissipation cover plate and a heat-conducting metal sheet; wherein a gas groove is provided on the surface of the heat-conducting metal sheet.

[0040] Specifically, the chip is a chip to be packaged. The first surface of the substrate is used for bonding with the chip, and the second surface thereof can be provided with solder balls. A first gold-plated layer can be provided on the inner surface of the heat dissipation cover. The heat-conducting metal sheet can be an indium sheet, and a serrated gas groove is excavated on its surface. Preferably, both the upper and lower surfaces are excavated, and a serrated gas groove is also excavated on the surface of the first gold-plated layer away from the heat dissipation cover. The depth of the gas groove can be 1μm to 10μm, and can also be set to other depths according to process requirements.

[0041] Step S2, fix the front side of the chip to the first surface of the substrate, set the thermally conductive metal sheet on the back side of the chip, fix the heat dissipation cover plate to the first surface of the substrate and set it on the surface of the thermally conductive metal sheet away from the chip to obtain a unit to be welded.

[0042] Specifically, refer to Figure 2 After the capacitor and other components are mounted on the substrate, the front side of the chip (1) to be packaged is mounted on the substrate (2), and reflow soldering is performed to fix the chip (1) and the capacitor and other components on the substrate (2). An underfill glue may also be filled between the chip (1) and the substrate (2) for reinforcement. In order to weld the back side of the chip (1) to the heat-conducting metal sheet (3), it is necessary to form a second gold-plated layer (11) on the back side of the chip (1). The heat-conducting metal sheet (3) is then attached to the second gold-plated layer (11) on the back side of the chip (1), and the heat-dissipating cover plate (4) is then attached to the substrate (2) through an adhesive (5), so that the first gold-plated layer (41) on the inner surface of the heat-dissipating cover plate (4) is exactly in contact with the heat-conducting metal sheet (3), and the first gold-plated layer (41) and the heat-conducting metal sheet (3) are arranged correspondingly. Then, the adhesive (5) is pre-baked, and the pre-baking temperature is controlled at 125°C to 135°C (lower than the melting point of the indium sheet, 156.61°C), so that the adhesive (5) is solidified while ensuring that the shape of the gas groove on the heat-conducting metal sheet (3) remains intact. Finally, the following is formed: Figure 2 The structure shown is temporarily referred to as a unit to be welded in this embodiment.

[0043] Step S3, filling the gas groove with flux gas.

[0044] Specifically, the fluxing gas can be formic acid gas, which can replace conventional flux to play a role in fluxing. The unit to be soldered formed in the previous step S2 is placed in a formic acid reflow furnace, and the formic acid reflow furnace contains formic acid gas for fluxing. The pressure in the formic acid reflow furnace is evacuated to a pressure lower than the atmospheric pressure, such as 3kpa to 20kpa, by a vacuum method. Under the action of atmospheric pressure, the formic acid gas will smoothly enter and fill the gas grooves between the thermally conductive metal sheet and the chip back gold, and between the thermally conductive metal sheet and the gold-plated layer of the heat dissipation cover, thereby effectively removing oxidation.

[0045] Step S4: Fix the heat dissipation cover plate to the back side of the chip by welding the heat conductive metal sheet.

[0046] Specifically, the temperature in the formic acid reflow furnace is raised to the welding temperature, that is, the melting point of the heat-conducting metal sheet (the melting point of the indium sheet is 156.61°C), and the unit to be welded is reflowed. The heat-conducting metal sheet is melted and fills the gas groove, so that under the action of the flux gas, the molten heat-conducting metal is fully in contact with the back gold of the chip and the gold-plated layer of the heat dissipation cover plate. After cooling, the chip and the heat dissipation cover plate are fully welded to ensure the thermal conductivity between them.

[0047] A chip packaging method according to an embodiment of the present disclosure makes grooves on the surface of a heat-conducting metal sheet and a gold-plated layer of a heat dissipation cover plate, so that the flux gas can enter the grooves and fully contact the welding surface, thereby solving the problem that formic acid gas is difficult to enter the welding surface, enabling the flux gas to effectively remove oxidation, avoiding the occurrence of voids on the welding surface, and ensuring the heat dissipation efficiency of the packaged chip.

[0048] Another embodiment of the present disclosure provides a chip packaging structure, which is manufactured using the chip packaging method described in the previous embodiment. The specific manufacturing process has been described in detail in the previous embodiment, and will not be repeated herein.

[0049] A chip packaging structure of an embodiment of the present disclosure adopts a chip packaging method described above, and grooves are designed on the surface of the heat-conducting metal sheet and the gold-plated layer of the heat dissipation cover plate, so that the flux gas can enter the groove and fully contact the welding surface, thereby solving the problem that formic acid gas is not easy to enter the welding surface, allowing the flux gas to effectively remove oxidation, avoiding the occurrence of voids on the welding surface, and ensuring the heat dissipation efficiency of the packaged chip.

[0050] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A chip packaging method, It is characterized in that The method comprises: A chip, a substrate, a heat dissipation cover plate and a heat-conducting metal sheet are provided; wherein a gas groove is provided on the surface of the heat-conducting metal sheet; The front side of the chip is fixed to the first surface of the substrate, the heat-conducting metal sheet is arranged on the back side of the chip, and the heat-dissipating cover plate is fixed to the first surface of the substrate and arranged on the surface of the heat-conducting metal sheet away from the chip to obtain a unit to be welded; Filling the gas groove with flux gas; The heat dissipation cover plate is fixed to the back side of the chip by welding through the heat conductive metal sheet.

2. The method according to claim 1, It is characterized in that The surface of the heat-conducting metal sheet opposite to the back side of the chip and the surface opposite to the heat dissipation cover plate are both provided with gas grooves.

3. The method according to claim 1, It is characterized in that The heat dissipation cover plate is provided with a first gold-plated layer on a surface opposite to the heat-conducting metal sheet; The method of fixing the heat dissipation cover plate to the first surface of the substrate and arranging the heat dissipation cover plate on the surface of the heat conductive metal sheet facing away from the chip comprises: The heat dissipation cover plate is fixed to the first surface of the substrate, and the first gold-plated layer is arranged on the surface of the heat-conducting metal sheet away from the chip.

4. The method according to claim 3, It is characterized in that A gas groove is provided on a surface of the first gold-plated layer opposite to the heat-conducting metal sheet.

5. The method according to claim 1, It is characterized in that The back side of the chip has a second gold-plated layer; The step of arranging the heat-conducting metal sheet on the back side of the chip comprises: The heat-conducting metal sheet is arranged on the second gold-plated layer on the back side of the chip.

6. The method according to claim 1, It is characterized in that The flux gas is formic acid gas.

7. The method according to claim 6, It is characterized in that The step of filling the gas groove with flux gas comprises: Placing the unit to be welded in a formic acid reflow furnace; wherein the formic acid reflow furnace has formic acid gas; The pressure in the formic acid reflow furnace is reduced to below atmospheric pressure, so that the formic acid gas fills the gas recess.

8. The method according to any one of claims 1 to 7, It is characterized in that The heat-conducting metal sheet is an indium sheet.

9. The method according to any one of claims 1 to 7, It is characterized in that The depth of the gas groove is 1 μm to 10 μm.

10. A chip packaging structure, It is characterized in that The chip packaging structure is manufactured by the chip packaging method according to any one of claims 1 to 9.

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