Micro LED FPCB fitting position structure

Abstract

The utility model discloses a Micro LED FPCB (Flexible Printed Circuit Board) fitting position structure, which comprises a heat dissipation substrate, a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) circuit chip, an LED chip and an FPC (Flexible Printed Circuit) board, the CMOS circuit chip and the LED chip are connected through flip-chip bonding to form a semi-finished product module, and then the semi-finished product module is fixed on the heat dissipation substrate; a groove is formed in the middle of at least one side edge of the heat dissipation substrate; the edge of the FPC circuit board is inserted into the groove; the front surface of the heat dissipation substrate is provided with a slot, and the position of the slot corresponds to the position of a golden finger pad of the FPC circuit board. The area, except the open groove, of the front face of the heat dissipation substrate covers the surface of the FPC circuit board. The FPC circuit board is connected and conducted to the CMOS circuit chip through a gold wire; through the three-dimensional fixing structure of groove positioning and surface supporting, the anti-drawing performance is remarkably improved; the golden finger bonding pad is accurately exposed through the groove, glue is prevented from overflowing to pollute the bonding pad, the flatness of the substrate is stable, the bonding wire breaking risk is reduced, and the production cost is reduced.

Description

Technical Field

[0001] This utility model relates to the technical field of semiconductor FPCB circuit structure, specifically to a Micro LED FPCB bonding position structure. Background Technology

[0002] In Micro LED display technology, FPCB (Flexible Printed Circuit Board) typically consists of a heat dissipation substrate and an FPC circuit board; the traditional bonding method involves directly bonding the FPC circuit board to the surface of the heat dissipation substrate with adhesive, as shown in the attached image. Figure 2 As shown, the following defects exist: 1. Insufficient adhesion: It is fixed only by the bottom glue, without physical support points. When picking up and putting down, the FPC circuit board is easily separated from the heat sink substrate due to the pulling force; 2. Difficulty in glue control: Too much glue is easy to overflow into the soldering area, affecting the flatness of the CMOS circuit chip; too little glue results in insufficient adhesion and poor reliability; 3. High difficulty in rework: After peeling, the heat sink substrate and FPC circuit board have residual glue. Forcibly cleaning it can easily damage the circuit or substrate, resulting in poor wire bonding and increased manufacturing costs.

[0003] Therefore, there is an urgent need for an improved FPCB bonding structure that enhances the fixing effect through physical structure, reduces reliance on adhesives, and improves product reliability. Utility Model Content

[0004] The purpose of this utility model is to provide a Micro LED FPCB bonding position structure. Through the design of the side groove and front slot of the heat dissipation substrate, the physical fixation and electrical connection of the FPC circuit board are realized, solving the problems of insufficient peeling and adhesion and the convenience of wire bonding.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is: a Micro LED FPCB bonding position structure, including a heat dissipation substrate, a CMOS circuit chip, an LED chip, and an FPC circuit board;

[0006] The CMOS circuit chip and LED chip are connected by flip-chip bonding to form a semi-finished module, which is then fixed on the heat dissipation substrate;

[0007] At least one side of the heat dissipation substrate is provided with a groove in the middle portion;

[0008] The edge of the FPC circuit board is inserted into the groove;

[0009] The front side of the heat dissipation substrate is provided with a slot, and the position of the slot corresponds to the position of the gold finger pad of the FPC circuit board.

[0010] The front area of ​​the heat dissipation substrate, excluding the slot, covers the surface of the FPC circuit board.

[0011] The FPC circuit board is connected to the CMOS circuit chip through gold wires.

[0012] Preferably, the groove extends along the length of the side edge of the heat dissipation substrate, and the depth and width of the groove are matched with the thickness and width of the FPC circuit board, so that the FPC circuit board is tightly inserted into the groove.

[0013] Preferably, the slot is a through hole penetrating the front surface of the heat dissipation substrate, and the shape and size of the through hole are matched with the gold finger pad of the FPC circuit board.

[0014] Preferably, the material of the heat dissipation substrate is one of invar steel, aluminum, copper, ceramic or silicon nitride, and the thermal expansion coefficient and heat dissipation coefficient are selected and set according to the application scenario.

[0015] Preferably, after the FPC circuit board is inserted into the groove, the gold finger pad of the FPC circuit board faces upwards and is aligned with the slot, and the area of the heat dissipation substrate covering the surface of the FPC circuit board supports and fixes the FPC circuit board.

[0016] Preferably, the semi-finished product module is fixed on the heat dissipation substrate by a die bonding machine.

[0017] Preferably, the gold wire realizes the conductive connection between the CMOS circuit chip and the gold finger pad of the FPC circuit board through ultrasonic welding.

[0018] Compared with the prior art, the beneficial effects of the present application are as follows:

[0019] The Micro LED FPCB bonding position structure of the present application inserts the FPC circuit board into the groove, and the heat dissipation substrate covers the surface to form an upper support fulcrum. Combined with glue adhesion, the simple plane adhesion is converted into a three-dimensional fixed structure of "groove positioning + surface support", which significantly improves the pull-out resistance. The gold finger pad is precisely exposed through the slot, avoiding the pollution of the pad by the overflow of the glue, and the flatness of the substrate is stable, reducing the risk of wire breakage. At the same time, it is suitable for existing SMT, die bonding, ultrasonic wire bonding and other equipment, without the need to add complex processes, reducing production costs. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to make the technical field personnel better understand the application scheme, the technical scheme in the application examples will be described clearly and completely in the following by combining the drawings in the application examples. Obviously, the described examples are only a part of the application examples, not all. Based on the examples in the application, all other examples obtained by the ordinary skilled person in the art without creative labor should be within the scope of protection of the application.

[0021] Figure 2 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement. Figure 1 Figure 1 is a schematic diagram of the Micro LED FPCB bonding position structure of the application.

[0022] Figure 2 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement. Figure 2 Figure 3 is a schematic diagram of the structure before improvement.

[0023] Figure 4 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement. Figure 3 Figure 5 is a schematic diagram of the drawing test of the application.

[0024] Figure 6 is a schematic diagram of the drawing test before improvement. Figure 4 Figure 7 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement.

[0025] Figure 5 Figure 8 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement.

[0026] Figure 9 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement. Figure 6 Figure 10 is a schematic diagram of the water vapor entering path of the Micro LED FPCB before improvement.

[0027] Wherein: 1, heat dissipation substrate; 2, CMOS circuit chip; 3, LED chip; 4, FPC circuit board; 5, groove; 6, slot; 7, gold finger pad. DETAILED DESCRIPTION

[0028] In order to make the technical field personnel better understand the application scheme, the technical scheme in the application examples will be described clearly and completely in the following by combining the drawings in the application examples. Obviously, the described examples are only a part of the application examples, not all. Based on the examples in the application, all other examples obtained by the ordinary skilled person in the art without creative labor should be within the scope of protection of the application.

[0029] ​It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and in the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not intended to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0031] In addition, in addition to indicating the orientation or positional relationship, the above-mentioned part of the terms may also be used to indicate other meanings, for example, the term "upper" may also be used to indicate a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific circumstances.

[0032] In addition, the terms "mounting", "setting", "provided with", "connecting", "connecting", "sleeving" should be broadly understood. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two devices, elements or components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0034] Embodiment one

[0035] Attachment Figure 1 A Micro LED FPCB bonding position structure according to the present application comprises a heat dissipation substrate 1, a CMOS circuit chip 2, an LED chip 3 and an FPC circuit board 4.

[0036] The CMOS circuit chip 2 and the LED chip 3 are connected by flip-chip welding to form a semi-finished product module, and then are fixed on the heat dissipation substrate 1. Specifically, the semi-finished product module is fixed on the heat dissipation substrate 1 by a die bonding machine. The material of the heat dissipation substrate 1 is one of invar steel, aluminum, copper, ceramic or silicon nitride, and the thermal expansion coefficient and the heat dissipation coefficient are selected and set according to the application scenario.

[0037] A groove 5 is arranged at the middle of at least one side edge of the heat dissipation substrate 1. The groove 5 extends along the length direction of the side edge of the heat dissipation substrate 1. The depth and width of the groove 5 are matched with the thickness and width of the FPC circuit board 4, so that the FPC circuit board 4 is tightly inserted into the groove 5.

[0038] The edge of the FPC circuit board 4 is inserted into the groove 5. After the FPC circuit board 4 is inserted into the groove 5, the gold finger pad 7 of the FPC circuit board 4 faces upwards and is aligned with the slot 6. The area of the heat dissipation substrate 1 covering the surface of the FPC circuit board 4 supports and fixes the FPC circuit board 4.

[0039] The front surface of the heat dissipation substrate 1 is provided with a slot 6, and the position of the slot 6 corresponds to the position of the gold finger pad 7 of the FPC circuit board 4. The slot 6 is a through hole penetrating through the front surface of the heat dissipation substrate 1. The shape and size of the through hole are matched with the gold finger pad 7 of the FPC circuit board 4.

[0040] The area of the front surface of the heat dissipation substrate 1 except the slot 6 covers the surface of the FPC circuit board 4.

[0041] The FPC circuit board 4 is connected to the CMOS circuit chip 2 by gold wire. Specifically, the gold wire realizes the conduction connection between the CMOS circuit chip 2 and the gold finger pad 7 of the FPC circuit board 4 by ultrasonic welding.

[0042] Embodiment two

[0043] A Micro LED FPCB lamination position structure, and the specific preparation process and steps are as follows:

[0044] 1. Heat dissipation substrate 1 preparation;

[0045] Material selection: invar steel (thermal expansion coefficient 1.2-1.5×10 -6 / ℃, strong dimensional stability, suitable for high-precision scenarios).

[0046] Structure processing:

[0047] Side groove 5: A rectangular groove 5 is processed in the middle of any side of the heat dissipation substrate 1, which extends along the length direction of the substrate, with a depth of 0.3 mm (matching the thickness of 0.3 mm of the FPC circuit board 4) and a width of 1.5 mm (slightly larger than the edge width of 1.4 mm of the FPC circuit board 4, facilitating insertion).

[0048] Front slot 6: A circular through hole is opened at the position corresponding to the gold finger pad 7 of the FPC circuit board 4, with a diameter of 1.0 mm (matching the diameter of 0.9 mm of the gold finger pad 7, with a 0.1 mm edge reserved for positioning).

[0049] 2. FPC circuit board 4 design and preparation;

[0050] Circuit layout: The gold finger pad 7 adopts a gold plating process, with a size of 0.9 mm x 0.5 mm and a pitch of 0.3 mm, meeting the precision requirements of ultrasonic welding.

[0051] Edge structure: The edge width is 1.4 mm, and the thickness is 0.3 mm, matching the size of the groove 5 of the heat dissipation substrate 1, and forming a tight fit after insertion.

[0052] 3. Preparation of semi-finished module;

[0053] LED chip 3 and CMOS circuit chip 2 flip chip bonding:

[0054] The LED chip 3 (size 20 μm x 20 μm) is flip chip bonded with the CMOS circuit chip 2 (driving backplate) through Cu-Cu micro-welding points, realizing circuit conduction.

[0055] Surface deposition of SiO2 passivation layer (thickness 1 μm), to protect the chip from water vapor and impurities.

[0056] Module fixation: The semi-finished module is pasted in the central area of the heat dissipation substrate 1 by a die bonding machine, using UV glue (viscosity 5000 mPa·s) as the adhesive, and the curing conditions are: ultraviolet irradiation (365 nm, 1000 mJ / cm 2 ) for 30 seconds.

[0057] 4. Plug-in bonding and welding;

[0058] FPC circuit board 4 insertion groove 5: The edge of the FPC circuit board 4 is precisely inserted into the groove 5 of the heat dissipation substrate 1 by an SMT chip mounter, with the gold finger pad 7 facing up and completely aligned with the front slot 6, ensuring that the exposed area of the pad is ≥ 95%.

[0059] Ultrasonic wire bonding: Using a KS wire bonding machine, gold wire (25μm in diameter, 99.99% purity) is used to connect the pads of the CMOS circuit chip 2 to the gold finger pads 7 of the FPC circuit board 4. Welding parameters: pressure 50g, power 80mW, welding time 50ms, forming a strong ball bond connection.

[0060] 5. Testing and performance verification;

[0061] Pull-out test: A pull-out force of 5N was applied perpendicular to the surface of the heat sink substrate 1 for 10 seconds. The FPC circuit board 4 did not peel off from the heat sink substrate 1, while traditional structures peeled off under a force of 2N. (See attached...) Figure 3 and 4 , attached Figure 3 This is a schematic diagram of the pull-out test of this utility model. The FPC circuit board 4 is supported and held in place by a heat dissipation substrate 1 directly above it during manual pull-out, increasing pull-out resistance and airtightness. (See attached diagram.) Figure 4 The diagram shows the pull-out test before improvement. The FPC circuit board 4 was pulled out by hand without any support on top. It was only bonded by a small amount of glue at the bottom, resulting in poor pull-out resistance. The FPC circuit board 4 and the heat sink substrate 1 were easily separated.

[0062] Wire bonding yield: The yield of ultrasonic wire bonding has been increased from 85% to 98% compared to the traditional structure, and the wire breakage rate has been reduced from 15% to 2%.

[0063] Moisture intrusion test: After being stored for 24 hours in an environment with 85% humidity and 85℃, the moisture intrusion area on the back of the FPC circuit board with this structure is <5%, while the intrusion area of ​​the traditional structure is >30%; see attached. Figure 5 and 6 , attached Figure 5 This is a schematic diagram of the water vapor entry path of this utility model. Water vapor can only enter from one side, while the other three sides are covered and wrapped by the heat dissipation substrate 1, resulting in good airtightness; (See attached diagram) Figure 6 The diagram shows the water vapor entry path before improvement. Water vapor can enter from four sides, resulting in poor airtightness.

[0064] Example 3

[0065] Based on Embodiment 2, the material selection for the heat dissipation substrate 1 in lightweight application scenarios is as follows:

[0066] Material replacement: Heat sink 1 is made of aluminum alloy (6061-T6, coefficient of thermal expansion 23.6×10). -6 / ℃, heat dissipation coefficient 205W / (m·K)), suitable for lightweight display devices (such as AR glasses).

[0067] Structural adjustments: The depth of groove 5 is adjusted to 0.25mm (to match the thickness of FPC circuit board 4, which is 0.25mm), and the front slot 6 adopts a long strip shape (1.2mm × 0.6mm) to accommodate the densely arranged gold finger pads 7.

[0068] Process optimization: the adhesive material is selected as a heat-conducting silica gel (thermal conductivity 1.5 W / (m·K)), which improves the heat dissipation efficiency and meets the flexible connection requirement.

[0069] Example Four

[0070] Based on Example Two, the material selection of the heat dissipation substrate 1 in the high insulation scenario is as follows:

[0071] Material selection: alumina ceramic (Al2O3, thermal expansion coefficient 7x10 -6 / ℃, insulation resistance > 10 14 Ω), suitable for high-voltage driven Micro LED array.

[0072] Processing technology: the groove 5 and the slot 6 are cut by laser (precision ±5μm), which avoids the substrate cracking caused by mechanical processing.

[0073] Reliability improvement: the surface of the FPC circuit board 4 is covered with a polyimide protective layer (thickness 5μm), which forms a double insulation protection with the ceramic substrate.

[0074] A Micro LED FPCB bonding position structure of the application, by inserting the FPC circuit board 4 into the groove 5, the heat dissipation substrate 1 covers the surface to form an upper support fulcrum, combined with glue bonding, converts the simple plane bonding into a three-dimensional fixed structure of "groove 5 positioning + surface support", significantly improves the pull-out resistance; the gold finger pad 7 is accurately exposed through the slot 6, avoiding the glue overflow pollution of the pad, and the substrate flatness is stable, reducing the risk of wire breakage; at the same time, it is suitable for existing SMT, die bonding, ultrasonic wire bonding and other equipment, without adding complex process, reducing production cost.

[0075] Finally, it should be pointed out that the above is only the preferred embodiment of the application and is not intended to limit the application, although the application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A Micro LED FPCB bonding position structure, characterized in that: The heat dissipation substrate, the CMOS circuit chip, the LED chip and the FPC circuit board are included. The CMOS circuit chip and the LED chip are connected by flip-chip soldering to form a semi-finished module, and then fixed on the heat dissipation substrate. The middle part of at least one side edge of the heat dissipation substrate is provided with a groove. The edge of the FPC circuit board is inserted into the groove. The front surface of the heat dissipation substrate is provided with a slot, and the position of the slot corresponds to the position of the gold finger pad of the FPC circuit board. The area of the front surface of the heat dissipation substrate except the slot covers the surface of the FPC circuit board. The FPC circuit board is connected to the CMOS circuit chip by gold wire. 2.The Micro LED FPCB bonding position structure of claim 1, wherein: The groove extends along the length direction of the side edge of the heat dissipation substrate, and the depth and width of the groove are matched with the thickness and width of the FPC circuit board, so that the FPC circuit board is tightly inserted into the groove. 3.The Micro LED FPCB bonding position structure of claim 1, wherein: The slot is a through hole penetrating the front surface of the heat dissipation substrate, and the shape and size of the through hole are matched with the gold finger pad of the FPC circuit board. 4.The Micro LED FPCB bonding position structure of claim 1, wherein: The material of the heat dissipation substrate is one of invar steel, aluminum, copper, ceramic or silicon nitride, and the thermal expansion coefficient and heat dissipation coefficient are selected and set according to the application scenario. 5.The Micro LED FPCB bonding position structure of claim 1, wherein: After the FPC circuit board is inserted into the groove, the gold finger pad of the FPC circuit board faces upward and is aligned with the slot, and the area of the heat dissipation substrate covering the surface of the FPC circuit board forms support and fixation for the FPC circuit board. 6.The Micro LED FPCB bonding position structure of claim 1, wherein: The semi-finished module is fixed on the heat dissipation substrate by a die bonding machine. 7.The Micro LED FPCB bonding position structure of claim 1, wherein: The gold wire realizes the conduction connection between the CMOS circuit chip and the gold finger pad of the FPC circuit board by ultrasonic welding.

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