Bonding warping suppression method for filling Micro-LED device with epoxy resin

Abstract

The invention discloses a bonding warping suppression method for filling a Micro-LED device with epoxy resin, and relates to the technical field of micro-display packaging. The preparation method comprises the following steps: firstly, ultrasonically cleaning a Micro-LED chip and a substrate by using an acetone solution, then filling epoxy resin glue in gaps of the Micro-LED chip by adopting a multi-step spin coating mode, then heating and pre-curing, and finally etching and exposing In salient points and Au electrodes. And bonding the In salient point and the Au electrode by using a flip-chip bonding machine, and setting the applied temperature to be 100-200 DEG C, the pressure to be 1-100 kg and the bonding time to be 1-60 minutes in the bonding process, thereby obtaining the final Micro-LED device. According to the invention, the single side of the Micro-LED device is filled with the epoxy resin glue, so that warping can be inhibited, and the bonding strength can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of micro-display packaging technology, and in particular to a method for suppressing bonding warpage of a Micro-LED device filled with epoxy resin. Background Art

[0002] In recent years, Micro-LEDs have been considered by many experts and scholars as the next generation of new display technology due to their superior characteristics, such as high resolution, high brightness, and low power consumption. As the integrated circuit industry evolves towards smaller sizes and higher-density integration, higher requirements are being placed on Micro-LED display technology. This trend has led to the rapid development of packaging technologies such as flip-chip bonding, micropipe bonding, and mass transfer. However, micropipe bonding and mass transfer are currently difficult and immature. Flip-chip bonding, on the other hand, places the chip with its active surface facing downward, connecting it to the substrate via bumps. This creates short interconnects, effectively improving device heat dissipation, reducing optical loss, and enhancing electrical connection stability, making it the most mainstream bonding method for Micro-LEDs.

[0003] However, during the flip-chip bonding process, the mismatch in thermal expansion coefficients between the sapphire substrate and the Si substrate often leads to uneven stress distribution, which in turn causes device warping. This uneven stress not only reduces the bonding yield but also threatens the long-term reliability of the device.

[0004] Currently, traditional flip-chip bonding methods for Micro-LEDs address warpage by using low-melting-point metal bump materials to reduce bonding temperature, laser-assisted rapid heating to reduce thermal stress, laser-assisted / ultrasonic bonding that combines high-frequency vibration with thermal energy to increase bonding strength and reduce oxidation, and finite element simulation software to study stress and strain during the bonding process. However, these methods still have certain limitations. Summary of the Invention

[0005] The object of the present invention is to provide a method for suppressing bonding warpage of Micro-LED devices by filling them with epoxy resin, aiming to solve or improve at least one of the above-mentioned technical problems.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for suppressing bond warpage of a Micro-LED device by filling it with epoxy resin, comprising:

[0008] The Micro-LED chip is first ultrasonically cleaned with an acetone solution, and then epoxy resin glue is filled in the gaps of the Micro-LED chip by a multi-step spin coating method, and then heated for pre-curing. Finally, an etching technique is used to expose the In bumps and Au electrodes; the etching technique includes plasma etching, reactive plasma etching, and high-density plasma etching;

[0009] The In bump and the Au electrode are bonded using a flip-chip bonding machine, and the temperature applied during bonding is set to 100-200° C., the pressure is set to 1-100 kg, and the bonding time is set to 1-60 min to obtain the final Micro-LED device.

[0010] Optionally, the heating pre-curing is performed at 80-100° C. for 5-20 minutes.

[0011] Optionally, the etching time of the etching technology is 10-75 minutes.

[0012] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0013] The present invention discloses a method for suppressing bond warpage in micro-LED devices by filling them with epoxy resin. The preparation method comprises ultrasonically cleaning the micro-LED chip with an acetone solution, then filling the gaps of the micro-LED chip with epoxy resin glue using a multi-step spin coating method, then heating and pre-curing, and finally etching using a low-pressure plasma cleaner to expose the In bumps and Au electrodes. The In bumps and Au electrodes are then bonded using a flip-chip bonder, with the temperature applied during the bonding set at 100-200°C, the pressure at 1-100 kg, and the bonding time at 1-60 minutes, to obtain the final micro-LED device. The present invention can improve the bond strength by filling the micro-LED device with epoxy resin glue on one side. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 Schematic diagram of the epoxy resin filling process in this embodiment;

[0016] Figure 2 Schematic diagram of the cross section of the device after flip-chip bonding in this embodiment. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] The object of the present invention is to provide a method for suppressing bonding warpage of Micro-LED devices by filling them with epoxy resin, aiming to solve or improve at least one of the above-mentioned technical problems.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1-Figure 2 As shown, the present invention provides a method for suppressing bonding warpage of a Micro-LED device by filling it with epoxy resin, comprising the following parts:

[0021] (1) Filling with epoxy resin

[0022] (2) Flip-chip bonding

[0023] As a specific embodiment, the preparation process is described in detail:

[0024] (1) Filling with epoxy resin

[0025] like Figure 1 As shown, the epoxy resin filling process: Figure 1 (a) is multi-step spin coating; Figure 1 (b) is heating to evaporate the solvent (80-100°C, 5-20 min); Figure 1 (c) is plasma etching; Figure 1 (d) is the bonding between the chip and the substrate, and the bonding conditions are 100-200°C and 5-20kg.

[0026] After preparing the Micro-LED chip, it needs to be filled with epoxy resin glue, such as Figure 1 As shown in (a) above, the chip is first ultrasonically cleaned with an acetone solution to improve the adhesion of the epoxy adhesive. Next, epoxy adhesive is applied to the Micro-LED chip and the gaps using a multi-step spin coating process. The epoxy adhesive is then heated and cured (80-100°C for 5-20 minutes) to evaporate excess solvent. Plasma etching is then performed for 10-75 minutes. This exposes the In bumps and Au electrodes, facilitating subsequent bonding.

[0027] (2) Bonding

[0028] The flip-chip bonding step is performed using a flip-chip bonding machine. During the bonding process, the applied temperature is 100-200°C, the pressure is 1-100kg, and the bonding time is 1-60min. Among them, when the temperature is higher than 200°C, it may cause the resin polymer chain to break and irreversibly degenerate, reducing the bonding strength that could be achieved; below 100°C, the pressure required to be applied will be very large (>100kg), increasing the risk of chip breakage. The cross-section of the device after flip-chip bonding is as follows: Figure 2 shown.

[0029] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0030] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for suppressing bond warpage of a Micro-LED device by filling it with epoxy resin, characterized in that: include: The Micro-LED chip is first ultrasonically cleaned with an acetone solution, and then epoxy resin glue is filled in the gaps of the Micro-LED chip by a multi-step spin coating method, and then heated for pre-curing. Finally, an etching technique is used to expose the In bumps and Au electrodes; the etching technique includes plasma etching, reactive plasma etching, and high-density plasma etching; The In bump and the Au electrode are bonded using a flip-chip bonding machine, and the temperature applied during bonding is set to 100-200° C., the pressure is set to 1-100 kg, and the bonding time is set to 1-60 min to obtain the final Micro-LED device.

2. The method for suppressing bonding warpage of a Micro-LED device by filling the device with epoxy resin according to claim 1, wherein: The heating pre-curing is performed at 80-100° C. for 5-20 minutes.

3. The method for suppressing bonding warpage of a Micro-LED device by filling the device with epoxy resin according to claim 1, wherein: The etching time of the etching technology is 10-75 minutes.

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