Flexible chip packaging method and flexible chip packaging structure

Abstract

The invention relates to a flexible chip packaging method and a flexible chip packaging structure, and the method comprises the steps: enabling a flexible substrate to be provided with a first surface and a second surface, and enabling the flexible substrate to be provided with a mounting hole which penetrates from the first surface to the second surface; mounting a first heat dissipation film on the first surface, and enabling the first heat dissipation film to shield one end of the mounting hole; mounting the flexible chip to the mounting hole on one side, deviating from the first surface, of the second surface; and mounting a second heat dissipation film on the second surface, and enabling the second heat dissipation film to cover the flexible chip. The flexible substrate is provided with the mounting holes, so that the flexible chip can conduct heat to the first heat dissipation film and the second heat dissipation film, the temperature of the flexible chip is rapidly reduced by means of the large heat dissipation area of the first heat dissipation film and the second heat dissipation film, and the working stability of the flexible chip is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip heat dissipation, and in particular to a flexible chip packaging method and a flexible chip packaging structure. Background Art

[0002] In the 5G communication era, flexible electronic wearable devices are a very important research direction. Among them, flexible chips are a very important component of flexible electronic wearable devices. Flexible chips will be used in conjunction with a large amount of flexible polymers during the packaging process. Generally, the thermal conductivity of flexible polymers is poor, which leads to heat accumulation in the flexible chip and a rapid increase in temperature. In severe cases, the chip will fail. The problem of poor heat dissipation of flexible chips also makes it difficult to further improve their power and integration level, and poses certain challenges to the reliability, safety, durability and continuous stability of flexible electronic wearable devices. Summary of the invention

[0003] Based on this, it is necessary to provide a flexible chip packaging method and a flexible chip packaging structure to address the problem of poor heat dissipation ability of flexible chips.

[0004] A flexible chip packaging method, comprising:

[0005] The flexible substrate has a first surface and a second surface, and a mounting hole is provided on the flexible substrate and passes through from the first surface to the second surface;

[0006] Installing a first heat dissipation film on the first surface, and making the first heat dissipation film cover one end of the installation hole;

[0007] On a side of the second surface facing away from the first surface, mounting the flexible chip to the mounting hole;

[0008] A second heat dissipation film is mounted on the second surface, and the second heat dissipation film covers the flexible chip.

[0009] The process of opening the mounting hole of the present invention comprises: heating the hot melt adhesive film so that the hot melt adhesive film is adhered to the first surface, and then opening the mounting hole on the flexible substrate, and making the mounting hole penetrate the hot melt adhesive film;

[0010] The process of installing the first heat dissipation film to the first surface includes: after the installation hole is opened, heating the hot melt adhesive film again to adhere the first heat dissipation film to the hot melt adhesive film.

[0011] The process of installing the flexible chip to the installation hole of the present invention includes: setting a thermal conductive adhesive in the installation hole, adhering the thermal conductive adhesive to the first heat dissipation film, and then adhering the flexible chip to the thermal conductive adhesive.

[0012] After the flexible chip is mounted on the mounting hole, the flexible chip is firstly electrically connected to the second surface, and then the second heat dissipation film is mounted on the second surface.

[0013] After the flexible chip of the present invention is electrically connected to the second surface, the flexible chip is firstly glued on the second surface, and then the second heat dissipation film is installed on the second surface.

[0014] The process of installing the first heat dissipation film to the first surface of the present invention comprises: after the installation hole is opened, heating the hot melt adhesive film so that the hot melt adhesive film is adhered to the first surface, and adhering the first heat dissipation film to the side of the hot melt adhesive film away from the first surface;

[0015] The process of installing the flexible chip to the installation hole includes: after the hot melt adhesive film is adhered to the first surface, the flexible chip is directly adhered to the hot melt adhesive film.

[0016] The hot melt adhesive film of the present invention is a DAF adhesive film.

[0017] A flexible chip packaging structure, comprising:

[0018] A flexible substrate having a first surface and a second surface, and having a mounting hole extending from the first surface to the second surface;

[0019] A first heat dissipation film is disposed on the first surface and covers one end of the mounting hole;

[0020] a second heat dissipation film, disposed on the second surface and shielding the other end of the mounting hole; and

[0021] The flexible chip is arranged at the mounting hole to be sandwiched between the first heat dissipation film and the second heat dissipation film.

[0022] The first heat dissipation film and / or the second heat dissipation film of the present invention includes one or more of a graphene film, a copper foil, a boron nitride film, and a MXene film.

[0023] The present invention further comprises a gel layer, and the gel layer is located on a side of the first heat dissipation film facing away from the second heat dissipation film.

[0024] The beneficial effects of the present invention are:

[0025] The flexible substrate is provided with mounting holes so that the flexible chip can conduct heat to the first heat dissipation film and the second heat dissipation film. The larger heat dissipation area of ​​the first heat dissipation film and the second heat dissipation film can reduce the temperature of the flexible chip more quickly, thereby improving the working stability of the flexible chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a state change diagram of the flexible chip packaging structure in Example 1 of the present invention;

[0027] Figure 2 This is a state change diagram of the flexible chip packaging structure in Example 2 of the present invention.

[0028] Reference numerals:

[0029] 1. Flexible substrate; 11. First surface; 12. Second surface; 13. Mounting hole; 2. Hot melt adhesive film; 3. First heat dissipation film; 4. Flexible chip; 5. Second heat dissipation film; 6. Thermal conductive adhesive; 7. Protective film; 8. Gel layer. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0035] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0036] Embodiment 1:

[0037] This embodiment provides a flexible chip packaging method for preparing a flexible chip packaging structure. The corresponding flexible chip packaging structure state in each step of the flexible chip packaging method is as follows: Figure 1 shown.

[0038] A flexible chip packaging method, specifically comprising:

[0039] Step S1: a polyimide film is selected as a flexible substrate 1 , wherein the flexible substrate 1 has a first surface 11 and a second surface 12 that are opposite to each other.

[0040] Step S2: heating the hot melt adhesive film 2 so that the hot melt adhesive film 2 is adhered to the first surface 11, and the hot melt adhesive film 2 and the first surface 11 remain in a bonding state.

[0041] Step S3 : after the hot melt adhesive film 2 is cooled, laser etching is performed on the flexible substrate 1 to form a mounting hole 13 on the flexible substrate 1 . The mounting hole 13 passes from the first surface 11 to the second surface 12 and also passes through the hot melt adhesive film 2 .

[0042] Step S4: After the installation hole 13 is opened, the hot melt adhesive film 2 is heated again, and then the first heat dissipation film 3 is pasted onto the hot melt adhesive film 2 so that the first heat dissipation film 3 is attached to the side of the hot melt adhesive film 2 facing away from the flexible substrate 1. Accordingly, the first heat dissipation film 3 blocks and blocks the left end of the installation hole 13.

[0043] Step S5: placing a thermal conductive adhesive 6 in the mounting hole 13 and adhering the thermal conductive adhesive 6 to the first heat dissipation film 3. The thermal conductive adhesive 6 may be made of TIMs (thermal interface adhesive).

[0044] Step S6: On the side of the second surface 12 facing away from the first surface 11, that is, on the right side of the mounting hole 13, the flexible chip 4 is adhered to the thermal conductive adhesive 6, so as to mount the flexible chip 4 to the mounting hole 13. In this embodiment, the thermal conductive adhesive 6 pushes a part of the flexible chip 4 out of the mounting hole 13.

[0045] Step S7: The portion of the flexible chip 4 located outside the mounting hole 13 can be electrically connected to the second surface 12 by bonding, and then silicone is dripped onto the flexible chip 4 on the right side of the mounting hole 13 to form a protective film 7 at the right end of the mounting hole 13.

[0046] Step S8: Install the second heat dissipation film 5 to the second surface 12, so that the second heat dissipation film 5 covers the flexible chip 4, and accordingly, the protective film 7 is located between the flexible chip 4 and the second heat dissipation film 5. In some other embodiments, a hot melt adhesive film 2 may also be provided between the flexible substrate 1 and the second heat dissipation film 5, and the hot melt adhesive film 2 between the flexible substrate 1 and the second heat dissipation film 5 is heated to achieve adhesion of the flexible substrate 1 and the second heat dissipation film 5.

[0047] Step S9: pasting a gel layer 8 on the side of the first heat dissipation film 3 facing away from the hot melt adhesive film 2 .

[0048] Finally, the flexible chip packaging structure prepared by the flexible chip packaging method in this embodiment includes a flexible substrate 1, a first heat dissipation film 3, a second heat dissipation film 5, a gel layer 8, a protective film 7, a thermally conductive adhesive 6, a hot melt adhesive film 2, and a flexible chip 4. The mounting hole 13 on the flexible substrate 1 penetrates the flexible substrate 1 and the hot melt adhesive film 2 at the same time. The first heat dissipation film 3 is adhered to the first surface 11 through the hot melt adhesive film 2 and blocks the left end of the mounting hole 13. The second heat dissipation film 5 is adhered to the second surface 12 and blocks the right end of the mounting hole 13. The flexible chip 4 is connected to the first heat dissipation film 3 through the thermally conductive adhesive 6 at the mounting hole 13, and is connected to the second heat dissipation film 5 through the protective film 7.

[0049] The flexible substrate 1 itself has poor thermal conductivity and cannot effectively and directly conduct the heat generated by the flexible chip 4. The structure in which the mounting holes 13 are connected allows the first heat dissipation film 3 and the second heat dissipation film 5 to sandwich the flexible chip 4. The flexible chip 4 can conduct the generated heat to the first heat dissipation film 3 and the second heat dissipation film 5. The first heat dissipation film 3 and the second heat dissipation film 5 with larger areas disperse the heat, thereby improving the heat dissipation rate of the flexible chip 4, thereby reducing the failure probability of the flexible chip 4, improving the operating stability of the flexible chip 4, and helping to further improve the operating power of the flexible chip 4.

[0050] The thermal conductivity of the hot melt adhesive film 2 may not be excellent depending on the specific material of the hot melt adhesive film 2. Therefore, in this embodiment, the mounting hole 13 passes through the hot melt adhesive film 2, so that the flexible chip 4 transfers heat to the first heat dissipation film 3 through the thermal conductive adhesive 6 instead of the hot melt adhesive film 2, which not only ensures the connection strength between the flexible chip 4 and the first heat dissipation film 3, but also ensures the thermal conductivity efficiency of the flexible chip 4 to the first heat dissipation film 3.

[0051] Since the thermal conductive adhesive 6 needs to be attached to the first heat dissipation film 3, the mounting hole 13 cannot penetrate the first heat dissipation film 3. Therefore, in this embodiment, when the hot melt adhesive film 2 is adhered to the flexible substrate 1, the first heat dissipation film 3 cannot be adhered to the hot melt adhesive film 2 at the same time, otherwise the first heat dissipation film 3 will be damaged while etching to form the mounting hole 13.

[0052] Due to the obstruction of the first heat dissipation film 3 and the thermally conductive adhesive 6, the flexible chip 4 cannot achieve electrical connection with the first surface 11, so before the second heat dissipation film 5 is pasted on the second surface 12, the flexible chip 4 and the second surface 12 are electrically connected first. By reasonably setting the thickness of the thermally conductive adhesive 6, the thermally conductive adhesive 6 can push a part of the flexible chip 4 out to the outside of the mounting hole 13, making it easier to wire the connection between the flexible chip 4 and the second surface 12. The protective film 7 protects the flexible chip 4 and its electrically connected parts. Although the part of the flexible chip 4 outside the mounting hole 13 and the protective film 7 destroy the flatness of the second surface 12, its material is elastic, and the flexible characteristics of the second heat dissipation film 5 enable the second heat dissipation film 5 to maintain a good fit with the protective film 7, thereby helping the flexible chip 4 to conduct heat to the second heat dissipation film 5, and using the larger heat dissipation area of ​​the second heat dissipation film 5 for auxiliary heat dissipation.

[0053] Embodiment 2:

[0054] This embodiment provides a flexible chip packaging method for preparing a flexible chip packaging structure. The corresponding flexible chip packaging structure state in each step of the flexible chip packaging method is as follows: Figure 2 shown.

[0055] A flexible chip packaging method, specifically comprising:

[0056] Step A1: A polyimide film is selected as the flexible substrate 1 , and the flexible substrate 1 has a first surface 11 and a second surface 12 that are oppositely disposed.

[0057] Step A2: etching a mounting hole 13 on the flexible substrate 1 , wherein the mounting hole 13 passes through from the first surface 11 to the second surface 12 .

[0058] Step A3: heating the hot melt adhesive film 2 to make it sticky. In this embodiment, the hot melt adhesive film 2 is a 5 μm DAF adhesive film (adhesive film for die bonding), so that the hot melt adhesive film 2 has good thermal conductivity;

[0059] The first heat dissipation film 3 is a graphene film of 2mm*5mm*0.02mm. In other embodiments, the first heat dissipation film 3 may also adopt other sizes;

[0060] In this embodiment, since there is no need to make the mounting hole 13 pass through the hot-melt adhesive film 2, after the hot-melt adhesive film 2 is heated to generate viscosity, the first heat dissipation film 3 and the first surface 11 can be directly adhered to the two sides of the hot-melt adhesive film 2, thereby realizing the connection between the flexible substrate 1 and the first heat dissipation film 3, and the left end of the mounting hole 13 is shielded by the first heat dissipation film 3.

[0061] Step A4: After the connection between the flexible substrate 1 and the first heat dissipation film 3 is completed, the flexible chip 4 (a 50 μm PWM power chip in this embodiment) is placed into the mounting hole 13 from the side of the second surface 12 away from the first surface 11 while the hot melt adhesive film 2 is kept heated and sticky, so that the flexible chip 4 is directly attached to the hot melt adhesive film 2, and the connection between the flexible chip 4 and the first heat dissipation film 3 is achieved without the need for additional thermal conductive adhesive. In this embodiment, the flexible substrate 1 is also not easy to conduct heat and cannot effectively dissipate the heat generated by the flexible chip 4. However, since the DAF adhesive film with good thermal conductivity is used as the hot melt adhesive film 2 in this embodiment, the hot melt adhesive film 2 can conduct the heat generated by the flexible chip 4 to the first heat dissipation film 3 even after cooling, and the first heat dissipation film 3 with a larger heat dissipation area dissipates the heat, thereby reducing the temperature of the flexible chip 4.

[0062] Step A5: the flexible chip 4 is electrically connected to the second surface 12 by wire bonding, and then silicone is dripped onto the flexible chip 4 on the right side of the mounting hole 13 , thereby forming a protective film 7 at the right end of the mounting hole 13 .

[0063] Step A6: Install the second heat dissipation film 5 to the second surface 12, so that the second heat dissipation film 5 covers the flexible chip 4. Correspondingly, the protective film 7 is located between the flexible chip 4 and the second heat dissipation film 5. In this embodiment, the second heat dissipation film 5 is also a graphene film. In some other embodiments, a hot melt adhesive film 2 can also be provided between the flexible substrate 1 and the second heat dissipation film 5. By heating the hot melt adhesive film 2 between the flexible substrate 1 and the second heat dissipation film 5, the flexible substrate 1 and the second heat dissipation film 5 are adhered.

[0064] Step A7: A gel layer 8 with a thickness of 2 mm is pasted on the side of the first heat dissipation film 3 facing away from the hot melt adhesive film 2 . The gel layer 8 is made of a biomass gel material, such as polylipoic acid-based gel.

[0065] In order to verify the cooling effect of the first heat dissipation film 3 and the second heat dissipation film 5 on the flexible chip 4, the present embodiment performs the following temperature measurements on the flexible chip packaging structure in different states:

[0066] For the flexible chip 4 having only the flexible substrate 1 but without the first heat dissipation film 3, the second heat dissipation film 5 and the gel layer 8, the temperature is 75°C at a power of 0.4W, and the temperature is 144.5°C at a power of 1.5W, and the flexible chip 4 is burned;

[0067] For the flexible chip 4 with the flexible substrate 1 and the first heat dissipation film 3 but without the second heat dissipation film 5 and the gel layer 8, the temperature is 37°C at a power of 0.4W and 75.5°C at a power of 1.5W;

[0068] For the flexible chip 4 having the flexible substrate 1, the first heat dissipation film 3 and the second heat dissipation film 5, but without the gel layer 8, the temperature is 32°C at a power of 0.4W and 63.8°C at a power of 1.5W;

[0069] For the flexible chip 4 having the flexible substrate 1, the first heat dissipation film 3, the second heat dissipation film 5 and the gel layer 8, the temperature is 30.8°C at a power of 0.4W, and the temperature is 59.8°C at a power of 1.5W. The maximum temperature of the gel layer 8 is 33.7°C, which will not cause discomfort when in contact with human skin.

[0070] The above temperature measurement processes are all observed by infrared thermal imager.

[0071] Embodiment 3:

[0072] In this embodiment, several flexible chip packaging structures are prepared by the same flexible chip packaging method as in Embodiment 2. The difference between this embodiment and Embodiment 2 is that the first heat dissipation film and the second heat dissipation film are 2mm*5mm*0.01mm copper foils. In other embodiments, the first heat dissipation film and the second heat dissipation film may also be of other sizes.

[0073] In order to verify the cooling effect of the first heat dissipation film and the second heat dissipation film on the flexible chip, this embodiment also performs the following temperature measurements on the flexible chip packaging structure in different states:

[0074] For a flexible chip having only a flexible substrate but no first heat dissipation film, second heat dissipation film and gel layer, the temperature is 75°C at 0.4W power and 144.5°C at 1.5W power, and the flexible chip is burned;

[0075] For the flexible chip with a flexible substrate and a first heat dissipation film but without a second heat dissipation film and a gel layer, the temperature is 41.9°C at a power of 0.4W and 83.5°C at a power of 1.5W.

[0076] For a flexible chip having a flexible substrate, a first heat dissipation film, and a second heat dissipation film without a gel layer, the temperature is 34°C at a power of 0.4W and 68.5°C at a power of 1.5W.

[0077] For the flexible chip having a flexible substrate, a first heat dissipation film, a second heat dissipation film and a gel layer, the temperature is 32.8°C at a power of 0.4W, and is 64.3°C at a power of 1.5W. The maximum temperature of the gel layer 8 is 33.2°C, which will not cause discomfort when in contact with human skin.

[0078] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A flexible chip packaging method, characterized in that: include: The flexible substrate has a first surface and a second surface, and a mounting hole is provided on the flexible substrate and passes through from the first surface to the second surface; Installing a first heat dissipation film on the first surface, and making the first heat dissipation film cover one end of the installation hole; On a side of the second surface facing away from the first surface, mounting the flexible chip to the mounting hole; A second heat dissipation film is mounted on the second surface, and the second heat dissipation film covers the flexible chip.

2. The flexible chip packaging method according to claim 1, characterized in that: The process of opening the mounting hole includes: heating the hot melt adhesive film so that the hot melt adhesive film is adhered to the first surface, and then opening the mounting hole on the flexible substrate, and making the mounting hole penetrate the hot melt adhesive film; The process of installing the first heat dissipation film to the first surface includes: after the installation hole is opened, heating the hot melt adhesive film again to adhere the first heat dissipation film to the hot melt adhesive film.

3. The flexible chip packaging method according to claim 1, characterized in that: The process of installing the flexible chip to the installation hole includes: setting a thermal conductive adhesive in the installation hole, adhering the thermal conductive adhesive to the first heat dissipation film, and then adhering the flexible chip to the thermal conductive adhesive.

4. The flexible chip packaging method according to claim 3, characterized in that: After the flexible chip is mounted on the mounting hole, the flexible chip is first electrically connected to the second surface, and then the second heat dissipation film is mounted on the second surface.

5. The flexible chip packaging method according to claim 4, characterized in that: After the flexible chip is electrically connected to the second surface, the flexible chip is firstly glued on the second surface, and then the second heat dissipation film is installed on the second surface.

6. The flexible chip packaging method according to claim 1, characterized in that: The process of installing the first heat dissipation film to the first surface includes: after the installation hole is opened, heating the hot melt adhesive film so that the hot melt adhesive film is adhered to the first surface, and adhering the first heat dissipation film to the side of the hot melt adhesive film away from the first surface; The process of installing the flexible chip to the installation hole includes: after the hot melt adhesive film is adhered to the first surface, the flexible chip is directly adhered to the hot melt adhesive film.

7. The flexible chip packaging method according to claim 6, characterized in that: The hot melt adhesive film is a DAF adhesive film.

8. A flexible chip packaging structure, characterized in that: include: A flexible substrate having a first surface and a second surface, and having a mounting hole extending from the first surface to the second surface; A first heat dissipation film is disposed on the first surface and covers one end of the mounting hole; A second heat dissipation film is disposed on the second surface and shields the other end of the mounting hole; and The flexible chip is arranged at the mounting hole to be sandwiched between the first heat dissipation film and the second heat dissipation film.

9. The flexible chip packaging structure according to claim 8, characterized in that: The first heat dissipation film and / or the second heat dissipation film includes one or more of a graphene film, a copper foil, a boron nitride film, and a MXene film.

10. The flexible chip packaging structure according to claim 8, characterized in that: It also includes a gel layer, and the gel layer is located on a side of the first heat dissipation film that is away from the second heat dissipation film.

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