Method of bonding lens attached substrate

Abstract

To bond substrates with lenses with high bonding strength.SOLUTION: A method of bonding two lens-attached substrates, the method comprising: a surface treatment step of treating surfaces of substrate portions of the two lens-attached substrates with any one of water plasma, oxygen plasma, and ultraviolet rays; a coating treatment step of applying a silane coupling agent to the surface of the substrate portion of at least one of the two lens-attached substrates; and a heat press treatment step of bringing the two lens-attached substrates into contact with each other on the surfaces of the respective substrate portions by aligning optical axes of lens portions thereof, and heating and pressurizing the two lens-attached substrates.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for bonding a lens-equipped substrate that constitutes a camera module mounted on a smartphone or the like. [Background technology]

[0002] Camera modules generally consist of multiple lenses, which are produced by stacking multiple lens-equipped substrates and bonding the substrate parts (substrate parts) together. Resins such as polycarbonate (PC), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene (PE), polyester (PEs), polystyrene (PS), polypropylene (PP), polyetherimide (PEI), and polydimethylsiloxane (PDMS) are sometimes used as materials for the substrate parts of lens-equipped substrates.

[0003] Of these resins, PC and PET have ester bonds in their main chains, while PMMA has ester bonds in their side chains. Such resins having ester bonds in their main chains or side chains are referred to herein as ester-based resins. Furthermore, in this specification, an object (plate, shaped object, etc.) made of resin is referred to as a resin body, and an object made of an ester-based resin is particularly referred to as an ester-based resin body. Note that, in this specification, the term "ester bond" refers not only to an ester bond in the narrow sense formed by a condensation reaction between a carboxylic acid and an alcohol, but also to an ester bond in the broad sense formed by a condensation reaction between an organic or inorganic oxo acid and a compound having a hydroxy (OH) group.

[0004] When manufacturing a camera module, various methods have been devised to reliably bond the substrate portions of multiple lens-equipped substrates together, including treating the substrate portions with various plasmas.

[0005] For example, Patent Document 1 describes treating the substrate portions of two lens-equipped substrates with plasma of oxygen (O2), nitrogen (N2), helium (He), argon (Ar), hydrogen (H2), etc., and then bonding the substrates together and performing an annealing process. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-045651 [Patent Document 2] International Publication No. 2016 / 147828 Summary of the Invention [Problem to be solved by the invention]

[0007] Camera modules used in smartphones and the like need to have high impact resistance when dropped to the ground, and the substrate portions of the lens-equipped substrate need to be bonded together with high bonding strength. However, the method described in Patent Document 1 has limitations on the bonding strength that can be obtained.

[0008] The problem to be solved by the present invention is to bond a lens-fitted substrate with high bonding strength. [Means for solving the problem]

[0009] The bonding method according to the present invention, which has been made to solve the above problems, is a method for bonding two lens-fitted substrates, which comprises the steps of: a surface treatment step of treating the surface of each of the substrate portions of the two lens-equipped substrates with water plasma, oxygen plasma, or ultraviolet light; a coating treatment step of applying a silane coupling agent to the surface of at least one of the substrate portions of the two lens-equipped substrates; a heat pressing process in which the two lens-equipped substrates are brought into contact with each other at the surfaces of the substrate portions while aligning the optical axes of the lens portions, and then heated and pressed; Includes.

[0010] Here, the lens-equipped substrate comprises a lens portion made of lens resin (e.g., PC, PET, PMMA, COP, COC, PEs, PS, PP, PEI, PDMS, etc.) or optical glass, and a substrate portion that supports the lens portion at its periphery. The substrate portion is typically made of resin (e.g., PC, PET, PMMA, COP, COC, PE, PEs, PS, PP, PEI, PDMS, silicon (Si), etc.). The lens portion and substrate portion may be integrally molded using the same material, or they may be made of different materials and then bonded together. [Effects of the Invention]

[0011] In the present invention, when bonding two lens-fitted substrates, the surfaces of the substrate parts of both lens-fitted substrates are treated with water plasma, oxygen plasma, or ultraviolet light, and then a silane coupling agent is applied to the surface of the substrate part of at least one of the two lens-fitted substrates, thereby increasing the bonding strength between the substrate parts. Note that even when there are three or more lens-fitted substrates, the present invention can be applied to each of two adjacent lens-fitted substrates.

[0012] In the method for bonding lens-equipped substrates according to the present invention, it is most preferable that the surface treatment step be performed using water plasma in order to obtain higher bonding strength. Treatment using water plasma is particularly suitable when at least one of the substrate portions of the two lens-equipped substrates is made of an ester-based resin.

[0013] As described in Patent Document 2, when joining two resin bodies, at least one of which is made of a resin such as PMMA, if the time spent treating the resin bodies made of a resin such as PMMA with ultraviolet light or plasma using N2, Ar, O2, etc. as a raw material is prolonged, the bonding strength between the resin bodies may actually decrease. According to the inventor's research, this problem is caused by the fact that when the surface of an ester resin body such as PMMA is treated with ultraviolet light, etc., ester bonds near the surface are cleaved and OH groups are introduced at the cleaved sites (a layer in this state will be referred to as a brittle layer), and if a brittle layer is formed near the joining surface of the ester resin body, the brittle layer of the ester resin body will peel off when the resin bodies are pulled together, even if a silane coupling agent is applied and then joined.

[0014] In contrast, if the surface of the ester resin body is treated with water plasma, a brittle layer will not be formed near the surface of the ester resin body even if the plasma treatment time is long, and the bonding strength will not decrease.

[0015] Therefore, according to the present invention, the lens-fitted substrate can be bonded with high bonding strength, and a camera module that is resistant to impacts and the like can be manufactured. [Brief explanation of the drawings]

[0016] [Figure 1] 10 is a diagram showing the processing procedures of a joining method according to Experiment 1 and a joining method according to Experiment 2. FIG. [Figure 2] FIG. 1 is a diagram illustrating the water plasma treatment in this test. [Figure 3] This is a photograph of two test pieces joined together. [Figure 4] This is a photograph showing the state in which the bonded test piece was set in the tensile testing machine. [Figure 5] 1A and 1B are diagrams showing the structure of a side surface of a camera module formed by stacking a plurality of lens-equipped substrates. [Figure 6] 1 is a diagram showing a processing procedure of a bonding method according to an embodiment of the present invention. [Figure 7] 10A and 10B are diagrams illustrating ultraviolet light treatment according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] First, the method and results of the experiment conducted to confirm the effects of the present invention will be described with reference to the drawings.

[0018] <Test piece and its joining method> [Test piece] In this experiment, a plurality of PC flat plates (PCSMPS610 manufactured by Takiron C.I. Co., Ltd.) measuring 9 mm x 15 mm x 0.5 mm were prepared as test pieces 1.

[0019] 1A and 1B are diagrams showing the processing procedures of a joining method according to Experiment 1 (FIG. 1A) and a joining method according to Experiment 2 (FIG. 1B). Each step shown in FIG. 1 will be explained below.

[0020] [Water plasma treatment] This is the plasma treatment related to Experiment 1. For this treatment, an Aqua Plasma (registered trademark) cleaner AQ-500 manufactured by Samco Inc. was used. Figure 2 is a diagram illustrating the water plasma treatment in this test. As shown in Figure 2, the test piece 1 was placed, with the bonding surface facing up, on the lower electrode (ground electrode) 22 of the parallel plate type electrodes in the treatment chamber 21 of the same device. The plasma treatment conditions are as follows. Note that the water plasma treatment may also be performed in an atmospheric pressure atmosphere. Process gas: water vapor (H2O) Flow rate: 12sccm Pressure: approx. 7 Pa High frequency power: 50W Processing time: 40 seconds

[0021] [Oxygen plasma treatment] This is a plasma treatment according to Experiment 2. The treatment conditions are the same as those of the water plasma treatment described above, except that the treatment gas is oxygen (O2).

[0022] [Coating treatment] Test piece 1 was immersed in a solution of aminopropyltrimethoxysilane (APS), a silane coupling agent, for 5 seconds. After immersion, the bonding surface was washed with pure water (alcohol washing was also possible) and dried by spraying nitrogen gas (air could be used instead of nitrogen gas) to minimize the amount of silane coupling agent remaining on the surface of test piece 1. This resulted in an APS coating on the bonding surface of test piece 1. An aqueous solution of polyethyleneimine (PEI) may also be used as the silane coupling agent. Furthermore, to minimize the amount of silane coupling agent remaining on the bonding surface of test piece 1, the solution is preferably diluted to 10% (preferably 1%) or less with water or alcohol.

[0023] [Press processing] At room temperature (25°C) and atmospheric pressure (approximately 0.1 MPa), the bonding surfaces of the two test pieces 1,1 were brought into contact with each other, and then held for 3 minutes while applying pressure (1 MPa or less) using a hand roller. It is preferable to perform this pressing process in a reduced-pressure (100 Pa) environment, as this allows for the removal of air that had entered the bonding surfaces when the test pieces 1,1 were brought into contact with each other. Alternatively, the stacked test pieces 1,1 may be pressurized at a pressure of 1 MPa or more and 10 MPa or less. The test pieces were then heated to 80°C for 30 minutes (heating process). While heating between 50°C and 160°C is sufficient for the heating process, heating to 70°C to 90°C is more preferable, and heating to 80°C is even more preferable. The pressing process may be performed with heating, rather than at room temperature, in which case a separate heating process is not necessary.

[0024] <Experimental Method> Figure 3 is a photograph of the joined test pieces 1,1. Figure 4 is a photograph of the joined test pieces 1,1 set in a tensile tester. After joining the test pieces 1,1 as shown in Figures 3 and 4, the joint strength and location of fracture were confirmed using the tensile tester. Specifically, the top and bottom of the joined body were fixed to bolts, and one of the test pieces 1 was pulled vertically to confirm the joint strength. The tensile strength test was conducted in accordance with JIS K 6849, and the joint strength was measured using a force gauge ZTA-500N manufactured by Imada Co., Ltd.

[0025] <Experimental Results> In experiment 1, the bond strength of specimen 1,1 was 385 N / cm 2 In Experiment 2, the bond strength of test piece 1 was 187 N / cm 2 It was.

[0026] The results of Experiments 1 and 2 show that the test pieces 1, 1 can be bonded with high bonding strength by performing water plasma treatment or oxygen plasma treatment followed by coating and pressing. It is also clear that the strength is higher when treated with water plasma than when treated with oxygen plasma.

[0027] Next, a method for manufacturing a camera module by bonding multiple lens-fitted substrates will be described as an exemplary embodiment of the method for bonding lens-fitted substrates according to the present invention. Fig. 5 is a diagram showing the side structure of a camera module formed by stacking seven lens-fitted substrates (L1 to L7). The lens-fitted substrate is composed of a lens portion and a substrate portion that supports the lens portion at its outer periphery. As shown in Fig. 5, the camera module is manufactured by stacking multiple lens-fitted substrates with their optical axes aligned and bonding the substrate portions together.

[0028] In this embodiment, the lens portion of the lens-equipped substrate can be molded from a resin such as PC, PET, PMMA, COP, COC, PEs, PS, PP, PEI, or PDMS, and the substrate portion can be molded from a resin such as PC, PET, PMMA, COP, COC, PEs, PS, PP, PEI, or PDMS, or a silicon plate. The lens portion and substrate portion can be integrally molded simultaneously using the same resin by injection molding to form a lens-equipped substrate. In Figure 5, lens-equipped substrates L2, L6, and L7 are integrally molded. Alternatively, the lens portion and substrate portion can be molded from different resins and then bonded together, or the lens portion can be bonded to a silicon substrate portion to form a lens-equipped substrate. In Figure 5, lens-equipped substrates L1, L3, L4, and L5 are lens-equipped substrates obtained by bonding a lens portion to a substrate portion. The bonding surface of the substrate portion is the portion that will bond to the substrate portion of another lens-equipped substrate when stacked, so it is preferable that it has high flatness.

[0029] These lens-equipped substrates are bonded together using the method shown in Fig. 6. Fig. 6 is a diagram showing the processing procedures of several bonding methods according to this embodiment. An example of the conditions for each process in these procedures will be described below.

[0030] [Water plasma treatment] As explained above, this treatment can be performed using the Aqua Plasma® Cleaner AQ-500 manufactured by Samco, Inc. As shown in Figure 2, the lens-equipped substrate can be placed with the bonding surface facing up on the lower electrode (ground electrode) 22 of the parallel plate electrodes in the treatment chamber 21 of the apparatus. When bonding three or more lens-equipped substrates and treating both the front and back surfaces of the lens-equipped substrates, one surface can be treated first, then the substrate can be turned over and the other surface can be treated. Alternatively, the lens-equipped substrate can be placed vertically and both surfaces can be treated simultaneously. Simultaneous treatment of both surfaces improves bonding strength and shortens treatment time. The plasma treatment conditions for the water plasma treatment are as follows. The water plasma treatment can also be performed under atmospheric pressure. Process gas: water vapor (H2O) Flow rate: 1sccm~50sccm Pressure: 1Pa~30Pa High frequency power: 50W~250W Processing time: 1s to 600s

[0031] [Oxygen plasma treatment] As explained above, the processing conditions are the same as those of the water plasma processing, except that the processing gas is oxygen (O2).

[0032] [UV treatment] This treatment can be performed using a UV ozone cleaner UV-1 manufactured by Samco Inc. Figure 7 illustrates the ultraviolet treatment process of this embodiment. As shown in Figure 7, the lens-fitted substrate L can be placed in the treatment chamber 71 of the device with the bonding surface facing up. The pressure inside the treatment chamber 71 is then adjusted to a predetermined level by introducing nitrogen (N2) gas, and the substrate portion of the lens-fitted substrate is treated with ultraviolet light from a low-pressure mercury lamp 72 with a predetermined wavelength. When bonding three or more lens-fitted substrates and treating both the front and back surfaces of the lens-fitted substrates, one surface can be treated first, then the substrate can be turned over and the other surface can be treated. Alternatively, the lens-fitted substrate can be placed vertically and both surfaces can be treated simultaneously. Simultaneous treatment of both surfaces improves bonding strength and shortens treatment time. The ultraviolet treatment conditions can be as follows: Pressure: 0.1 MPa Ultraviolet wavelength: 253.7nm or 184.9nm Illuminance: 20mW / cm 2 Processing time: 3 minutes

[0033] Water plasma, oxygen plasma, and ultraviolet light all have in common the ability to hydrophilize the surface of the substrate portion of the lens-equipped substrate to be treated, but in order to obtain higher bonding strength, it is most preferable to treat the substrate portion with water plasma.

[0034] [Coating treatment] After treating the surface of the substrate with water plasma, oxygen plasma, or ultraviolet light, at least one of the two lens-equipped substrates is immersed in a solution of APS, a silane coupling agent, for approximately 5 seconds. After immersion, the bonding surface is washed with pure water or alcohol to minimize the amount of silane coupling agent remaining on the surface of the lens-equipped substrate, and then dried by spraying nitrogen gas or air. In this way, an APS coating is applied to the bonding surface of the lens-equipped substrate. An aqueous solution of polyethyleneimine (PEI) may also be used as the silane coupling agent. Furthermore, to minimize the amount of silane coupling agent remaining on the surface of the lens-equipped substrate, the solution is preferably diluted to 10% (preferably 1%) or less with water or alcohol.

[0035] [Press processing] At room temperature (25°C) and atmospheric pressure (approximately 0.1 MPa), two lens-equipped substrates are brought into contact with each other with the optical axes of their lens portions aligned, and then held for 3 minutes while applying pressure (1 MPa or less) using, for example, a hand roller. This pressing process is preferably carried out in a reduced-pressure (100 Pa or less) environment, since this allows for the removal of air that enters the bonding surface when the two lens-equipped substrates are stacked and brought into contact. Alternatively, the stacked lens-equipped substrates may be pressurized at 1 MPa or more and 10 MPa or less. The substrates are then heated to 80°C for 30 minutes (heating process). While heating to a temperature between 50°C and 160°C is sufficient for the heating process, heating to 70°C to 90°C is more preferable, and heating to 80°C is even more preferable. The pressing process may be carried out with heating, rather than at room temperature, in which case a separate heating process is not necessary.

[0036] In this embodiment, when performing water plasma treatment, oxygen plasma treatment, ultraviolet treatment, and coating treatment, it is preferable to mask the lens portion so as not to affect the optical properties of the lens portion.

[0037] In the method for bonding lens-equipped substrates according to the present invention, when at least one of the substrate portions of the two lens-equipped substrates is made of an ester-based resin, it is preferable to treat with water plasma. In other words, it is preferable to perform ultraviolet treatment on the substrate portions of the two lens-equipped substrates that are made of a resin other than an ester-based resin (for example, COP, COC, PE, PEs, PS, PP, PEI, PDMS, Si, etc.).

[0038] As described in Patent Document 2, when an ester resin such as PMMA is treated with ultraviolet light or plasma using N2, Ar, O2, etc. for a long time, the bonding strength between the resin bodies may actually decrease. According to the inventor's research, this problem is caused by the fact that treating the surface of the ester resin body with ultraviolet light, etc., breaks the ester bonds near the surface and introduces OH groups at the break sites (a layer in this state will be referred to as a brittle layer), and when a brittle layer is formed near the bonding surface of the ester resin body, the brittle layer of the ester resin body will peel off even if the ester resin body is bonded after being coated with a silane coupling agent.

[0039] In contrast, when the surface of the ester-based resin body is treated with water plasma, no brittle layer is formed near the surface of the ester-based resin body even if the plasma treatment time is long, and the bonding strength does not decrease. [Explanation of symbols]

[0040] 1...Test piece 21, 71...Processing chamber 22...Lower electrode 72...Low-pressure mercury lamp L1~L7...Lens-equipped board

Claims

1. A method for bonding two lensed substrates, comprising the steps of: a surface treatment step of treating the surfaces of the substrate portions of the two lens-equipped substrates with water plasma, oxygen plasma, or ultraviolet light; a coating treatment step of applying a silane coupling agent to the surface of at least one of the substrate portions of the two lens-equipped substrates; a heat pressing process in which the two lens-equipped substrates are brought into contact with each other at the surfaces of the substrate portions while aligning the optical axes of the lens portions, and then heated and pressed; A joining method comprising:

2. 2. The bonding method according to claim 1, wherein the surface of the substrate portion of the lens-equipped substrate is treated with water plasma in the surface treatment step.

3. 3. The bonding method according to claim 2, wherein at least one of the two lens-equipped substrates has a substrate portion made of an ester-based resin.

4. 2. The bonding method according to claim 1, wherein the surface of the substrate portion of the lens-equipped substrate is treated with oxygen plasma in the surface treatment step.

5. 2. The bonding method according to claim 1, wherein the substrate portions of the two lensed substrates are made of a resin material other than an ester-based resin material, and the surfaces of the substrate portions are treated with ultraviolet light in the surface treatment step.

6. The bonding method according to any one of claims 1 to 5, wherein the heat pressing step is carried out under a reduced pressure atmosphere of 100 Pa or less.

7. The bonding method according to any one of claims 1 to 5, wherein the heat pressing step is carried out at a temperature of 50°C to 160°C.

8. The bonding method according to claim 7, wherein the heat pressing step is carried out at a temperature of 70°C to 90°C.

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