Electronic device back cover lamination processing method

Abstract

The application discloses a kind of electronic equipment back cover bonding processing method, for realizing the bonding of big glass and small glass located around rear camera on the back of electronic equipment, the method comprises: UV glue bonding step: big, small glass is bonded together by UV glue to obtain bonding glass group;Bubble removal step: the bonding glass group is placed into bubble removal machine, and the best pressure value is found by applying stepwise increase / decrease pressure, and vacuum degassing is carried out based on the found best pressure value;Selective UV irradiation step: according to the characteristics of UV glue and the area that big, small glass needs to be bonded and fixed, the bonding glass group is selectively irradiated by UV light;Etching cleaning step: the bonding glass group is placed into etching liquid medicine matched with the characteristics of the UV glue for cleaning, and glue overflow is removed;The yield of the application is greatly improved, production capacity is improved, and the process is simple.

Description

Technical Field

[0001] This invention relates to the field of electronic device component processing, and in particular to a method for bonding back covers of electronic devices. Background Technology

[0002] With the advent of the 5G era, mobile phones have become an essential product in people's lives. The "crater" design and periscope telephoto lens have become the mainstream of mobile phone design today. The bonding of large and small glass panels has become a new favorite in the processing of "crater" designs and periscope telephoto lens back covers due to its high bonding precision, high production efficiency of adhesive bonding molding process, less manual labor, low scrap rate, short production cycle, and ease of professional and automated production. Therefore, the development of large and small glass bonding molding technology is particularly urgent.

[0003] Achieving high-precision, high-quality bonding requires proper debubbling and adhesive removal processes. Traditional debubbling methods include vacuum debubbling, which is inefficient, complex, produces poor results, and generates significant noise. Traditional adhesive removal methods include manual removal, hole plugging combined with manual removal, and film lamination combined with manual removal. Manual removal and hole plugging combined with manual removal are simple and efficient, but suffer from low yield, long lead times, and high costs, making them unsuitable for mass production. Film lamination combined with manual removal is relatively complex but more efficient, though still has lower yields, longer lead times, and higher costs. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for bonding back covers of electronic devices, addressing the numerous defects in debubbling and adhesive removal in the prior art.

[0005] The technical solution adopted by this invention to solve its technical problem is: to construct a method for bonding the back cover of an electronic device, used to achieve bonding between the large glass on the back of the electronic device and the small glass located around the rear camera, the method comprising:

[0006] UV adhesive bonding steps: Bond large and small glass pieces together with UV adhesive to obtain a bonded glass assembly;

[0007] Degassing step: The bonded glass assembly is placed in a degassing machine, and the optimal pressure value is found by applying a stepwise increase / decrease in pressure. Vacuum degassing is then performed based on the found optimal pressure value.

[0008] Selective UV irradiation step: Based on the characteristics of the UV adhesive and the areas where large and small glass pieces need to be bonded and fixed, the bonded glass assembly is selectively irradiated with UV light.

[0009] Etching and cleaning step: The bonded glass assembly is placed in an etching solution that matches the properties of the UV adhesive for cleaning, and excess adhesive is removed.

[0010] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, in the UV adhesive bonding step, before bonding the large and small glass pieces together, one of the large holes in the large and small glass pieces is positioned, and then the small glass piece is rotated so that the center line connecting the two large holes in the large glass piece coincides with the center line connecting the two large holes in the small glass piece.

[0011] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the UV adhesive is photosensitive. In the selective UV irradiation step, the UV adhesive in the area to be bonded and fixed is irradiated with UV light, while the UV adhesive that spills into other areas is shielded.

[0012] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the UV adhesive used is photosensitive; the method further includes performing a point curing step after the UV adhesive bonding step and before the debubbling step.

[0013] Point curing step: Select a pre-fixing point in the area to be bonded and fixed, and use UV light to irradiate and cure the pre-fixing point. The curing time is the first irradiation time to achieve the pre-cured strength of the adhesive, thereby preventing large and small glass misalignment.

[0014] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the UV adhesive used is photosensitive; the selective UV irradiation step includes: covering the holes of the large and small glass and the excess adhesive around the small glass with a mask, and irradiating the bonded glass assembly with UV light to cure it, with the curing time being the second irradiation time to achieve the initial strength of the adhesive bonding.

[0015] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the cleaning step is followed by a complete curing step: the bonded glass assembly is re-irradiated with a UV tunnel oven for a third irradiation time to achieve the full curing strength of the adhesive, and then subjected to low-temperature baking.

[0016] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the method further includes a pre-configuration step for dispensing parameters:

[0017] Before dispensing, calculate the cured volume V1 of the UV adhesive based on the size of the dispensing area and the thickness of the cured adhesive.

[0018] Calculate the volume V0 of the liquid adhesive before curing based on the cured volume V1: V0 = V1 / X, where X represents the content of non-volatile substances;

[0019] Configure the amount of adhesive V based on the volume V0 of the liquid adhesive, so that the amount of adhesive V is slightly larger than the calculated volume V0;

[0020] Calculate the dispensing height H based on the glue volume V, the dispensing width W, and the total glue length L: H = V / (L * W);

[0021] The dispensing speed is controlled based on the calculated dispensing height H.

[0022] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the temperature in the debubbling step is set to an optimal temperature, which is the temperature with the best debubbling effect found in advance through DOE cross-validation.

[0023] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the UV light irradiation method includes:

[0024] Top curing method: UV light is irradiated onto the top of the small glass;

[0025] Curing method: UV light shines on the bottom of the large glass;

[0026] Side curing method: UV light is irradiated on the side of the small glass.

[0027] Furthermore, in the aforementioned method for bonding the back cover of an electronic device, the UV adhesive bonding step specifically includes:

[0028] Plasma cleaning treatment is performed on the bonding surfaces of the large and small glass pieces that need to be bonded.

[0029] Fix the large glass pane onto the adhesive dispensing fixture, and apply adhesive to the edges of the holes on the bonding surface of the large glass pane and around the glass to form a dam of adhesive.

[0030] A second layer of filler adhesive is applied to the bonding surface of the large glass within the area enclosed by the dam adhesive. The amount of filler adhesive is greater than the amount of adhesive required for bonding the large and small glass. Excess filler adhesive overflows from the hole wall and around the glass when the large and small glass are bonded together.

[0031] Attach the bonding surface of the small glass to the corresponding position on the large glass surface, and then apply downward pressing force to complete the bonding.

[0032] The electronic device back cover bonding method of the present invention has the following beneficial effects: The present invention utilizes UV adhesive to bond large and small glass. Based on the characteristics of the UV adhesive and the areas where the large and small glass need to be bonded and fixed, the bonded glass assembly is selectively irradiated with UV light. Afterwards, it is immersed in a cleaning solution that matches the characteristics of the UV adhesive to remove excess adhesive. The operation is simple, efficient, yields high, and cost-effective, making it suitable for mass production. Moreover, the present invention finds the optimal pressure value by applying a stepwise increase / decrease in pressure. Based on the found optimal pressure value, vacuum degassing is performed, which can effectively remove residual air bubbles during the adhesive application process of the large and small glass. Compared with conventional methods, the yield is greatly improved, the production capacity is increased, the process is simple, and the equipment noise is significantly reduced. Furthermore, the positioning of the large and small glass involves first positioning one large hole of each large and small glass, and then rotating the small glass so that the center line connecting the two large holes of the large glass coincides with the center line connecting the two large holes of the small glass, ensuring the bonding accuracy of the large and small glass. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort:

[0034] Figure 1 This is a flowchart of the electronic device back cover bonding process of the present invention;

[0035] Figure 2 This is a schematic diagram of a bonded glass assembly formed by bonding large and small glass pieces together.

[0036] Figure 3 This is a schematic diagram of a single glue dispensing operation;

[0037] Figure 4 This is a schematic diagram of secondary dispensing;

[0038] Figure 5 This is a schematic diagram illustrating the UV curing process achieved by using a negative adhesive in conjunction with a cleaning solution.

[0039] Figure 6 This is a diagram illustrating the excess glue.

[0040] Figure 7 This is a flowchart of a specific embodiment of the electronic device back cover bonding processing method of the present invention. Detailed Implementation

[0041] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete. It should be understood that the embodiments of the present invention and the specific features thereof are detailed descriptions of the technical solutions of this application, and not limitations thereof. Where there is no conflict, the embodiments of the present invention and the technical features thereof can be combined with each other.

[0042] refer to Figure 1 The electronic device back cover bonding processing method of the present invention is applicable to electronic devices such as mobile phones and tablets, and the method includes:

[0043] S101, also known as UV adhesive bonding step: bonding large and small glass pieces together with UV adhesive to obtain a bonded glass assembly;

[0044] The large glass refers to the rectangular glass that forms the back cover of an electronic device, while the small glass is the rectangular glass located around the rear camera. The small glass is attached to the large glass to form a "crater" design.

[0045] Preferably, dispensing parameters can be pre-configured before dispensing, specifically:

[0046] 1) Calculate the cured volume V1 of the UV adhesive based on the size of the dispensing area and the thickness of the cured adhesive. V1 is obtained by multiplying the dispensing area by the thickness of the cured adhesive.

[0047] 2) Calculate the volume V0 of the liquid adhesive before curing based on the volume V1 after curing: V0 = V1 / X, where X represents the content of non-volatile substances, which is a known quantity.

[0048] 3) Configure the amount of adhesive V according to the volume V0 of the liquid adhesive, so that the amount of adhesive V is slightly larger than the calculated volume V0. For example, the purpose of slightly being slightly larger is to ensure that there is no lack of adhesive at the dispensing point, while the excess adhesive is wasted within an acceptable range. For example, the configured amount of adhesive V is less than 1% more than the calculated volume V0, and the excess adhesive overflows from the periphery of the small piece and the holes.

[0049] 4) Calculate the dispensing height H based on the glue volume V, the dispensing width W, and the total glue length L: H = V / (L * W);

[0050] The width W of the glue is determined by the diameter of the dispensing needle, and the total glue length L is obtained by dividing the dispensing area by the width W of the glue.

[0051] 5) Control the dispensing speed based on the calculated dispensing height H. The dispensing height H is determined by the dispensing speed, so once the dispensing height H is calculated, the dispensing speed can be configured.

[0052] Both large and small glass panes have holes, the size, location, and number of which are not limited. Before bonding the large and small glass panes together, they need to be aligned to ensure that all holes in the large glass pane are aligned with all holes in the small glass pane. Based on the characteristics of the holes in the large and small glass panes, this invention employs a combination of large hole positioning and angular rotation (the purpose of rotation is to make the center line connecting the two holes coincide) to ensure the alignment accuracy of all holes. (Reference) Figure 2 In one specific embodiment, both the large and small glass pieces have four holes, namely two large holes and two small holes. During positioning, one of the large holes in the large and small glass pieces is first positioned, and then the small glass piece is rotated so that the center line connecting the two large holes in the large glass piece coincides with the center line connecting the two large holes in the small glass piece.

[0053] The specific process of bonding the large and small glass pieces together using UV adhesive in this step is as follows:

[0054] 1) First, clean the surfaces of the large and small glass pieces to be bonded and keep them dry and free of grease. Then, perform plasma cleaning on the bonding surfaces of the two pieces of glass.

[0055] 2) Fix the large glass pane onto the adhesive applicator, and apply adhesive to the edges of the holes on the bonding surface of the large glass pane and around the glass to form a dam of adhesive, such as... Figure 3 As shown;

[0056] The distance between the dam and the edge is 0.7±0.1mm, the light intensity is 800±50mW / cm2, and the pre-curing time is 12±1s. The purpose of applying the dam is to prevent the glue from overflowing from the product hole wall and around the glass, which would result in insufficient glue.

[0057] 3) Apply a second layer of adhesive to the bonding surface of the large glass panes within the area enclosed by the dammed adhesive to form a filler adhesive, such as... Figure 4 As shown, the amount of filler adhesive is greater than the amount required for bonding the large and small glass panes. The excess filler adhesive overflows from the hole walls and around the glass panes when the large and small glass panes are bonded together.

[0058] 4) Attach the bonding surface of the small glass to the corresponding position on the large glass surface, and then apply downward pressing force to complete the bonding.

[0059] S102, also known as the degassing step: The bonded glass assembly is placed in a degassing machine, and the optimal pressure value is found by applying a stepwise increase / decrease in pressure. Vacuum degassing is then performed based on the found optimal pressure value.

[0060] For example, you can start with a minimum pressure value and gradually increase the pressure, or start with a maximum pressure value and gradually decrease the pressure. A stepwise increase / decrease means that the pressure increases in stages; the pressure value is divided into phases, with each phase increasing or decreasing by a certain amount compared to the previous phase. At the optimal pressure value, the degassing machine will display an error (stop working), indicating that the equipment has exceeded its capacity. The ultimately found optimal pressure value is a pressure range. We can select any pressure value within this range for vacuum degassing.

[0061] After finding the optimal pressure value, the optimal temperature is then used to remove air bubbles at the bonding location. This optimal temperature is determined beforehand through DOE cross-validation to achieve the best debubbling effect. The debubbling effect can be directly judged by observing the bubbles. The optimal temperature can be a single temperature point or a temperature range consisting of multiple temperature points. When searching for the optimal temperature, one can first compare the debubbling effect at a series of temperature points with a large temperature difference to find a temperature range with good debubbling effect. Then, within this temperature range, one can compare the debubbling effect at multiple temperature points with smaller temperatures, and so on, until the final temperature point or temperature range consisting of temperature points with the best debubbling effect is found.

[0062] This invention uses extreme stepped pressure to find the optimal pressure and then combines it with a specific temperature to remove bonding bubbles. It can generally effectively remove more than 98% of the residual bubbles during the dispensing process of glass of various sizes, improving the yield by nearly 30% and increasing production capacity by nearly 25% compared to conventional methods. The process is simple and the equipment noise is also significantly reduced.

[0063] S103, also known as the selective UV irradiation step: Based on the characteristics of the UV adhesive and the areas where large and small glass pieces need to be bonded and fixed, the bonded glass assembly is selectively irradiated with UV light.

[0064] The UV adhesive possesses two properties: photosensitivity (negative) and etching resistance (positive). In positive adhesive, the exposed portion dissolves in the etching solution, leaving the unexposed adhesive layer. In negative adhesive, the exposed portion does not dissolve in the etching solution, while the unexposed adhesive layer is dissolved. Figure 5 As shown, the UV adhesive used in this invention is a negative adhesive.

[0065] Preferably, after the UV adhesive bonding step S101 and before the degassing step S102, a spot curing step S1023 is performed as follows: a pre-fixing point is selected in the area to be bonded and fixed, and the pre-fixing point is irradiated and cured with UV light for the first irradiation time to achieve the pre-cured strength of the adhesive, thereby preventing the large and small glass from shifting. Specifically, if spot curing is not performed, shifting may occur during the glass handling process during degassing, during the degassing process, during the handling process after degassing and during adhesive removal, and until the next curing. Therefore, spot curing must be performed first to prevent glass shifting.

[0066] The "selective irradiation of the bonded glass assembly" mentioned in this step specifically refers to irradiating the UV adhesive in the areas that need to be bonded and fixed with UV light, while shielding the UV adhesive that has overflowed into other areas. For example, the holes in the large and small glass pieces and the excess adhesive around the small glass piece are masked, and the bonded glass assembly is irradiated and cured with UV light. During irradiation, the light rays are directed parallel to the areas that need to be retained, and the curing time is the second irradiation time to achieve the initial strength of the adhesive bond. Because the time for monomer polymerization and chemical cross-linking of the UV adhesive after the second irradiation is longer than that of pre-curing, the initial strength of the adhesive bond is greater than the pre-cured adhesive bond strength.

[0067] Based on the characteristics of the incoming glass materials, there are cases where both types of glass are translucent, one type of glass is translucent, or both types of glass are opaque. Therefore, UV light irradiation methods include the following three:

[0068] 1) Top curing method: UV light is irradiated onto the top of the small glass;

[0069] 2) Bottom curing method: UV light shines on the bottom of the large glass;

[0070] 3) Side curing method: UV light is irradiated on the side of the small glass.

[0071] For glass panes of varying sizes that allow light to pass through, or only the smaller panes that allow light to pass through, top curing is preferred. For glass panes that allow light to pass through only the larger panes, bottom curing is preferred. For glass panes of both sizes that are completely opaque, side curing is the only option.

[0072] S104, also known as the etching and cleaning step: The bonded glass assembly is placed in an etching solution that matches the properties of the UV adhesive for cleaning, and the excess adhesive is removed.

[0073] Preferably, the cleaning step S104 further includes a complete curing step S105: the bonded glass assembly is re-irradiated with a UV tunnel oven for a third irradiation time to achieve the full curing strength of the adhesive. After completion, it is baked at a low temperature until the free water molecules are less than 5%. Because the monomer polymerization and chemical cross-linking of the UV adhesive after irradiation with 365nm UV light produce small molecule water, and cleaning agent residue remains during the cleaning process, baking is necessary. The baking temperature is 120℃, and the time is 120 minutes. The third irradiation time is longer than the second irradiation time; therefore, the fully cured adhesive strength is greater than the initial adhesive strength. Because the time for monomer polymerization and chemical cross-linking of the UV adhesive after the third irradiation is longer than after the second irradiation, the adhesive strength of the glass after bonding is greater than that after the second irradiation. (Reference) Figure 7 The following is a specific example.

[0074] Step 1: First, clean and dry the surfaces of the two pieces of translucent glass to be bonded, ensuring they are free of grease. Then, perform plasma treatment on the surfaces of the two glass pieces to be bonded. The plasma power is 2.3kW, the delivery rate is 2±1m / min, the gas used for plasma treatment is N2, the N2 flow rate is 200000ml / min, the compressed air (CDA) flow rate is 200ml / min, the N2:CDA ratio is 1000:1, and the cycle time is 3s / pcs. The adhesive must be applied within 30 minutes after plasma treatment. The adhesive used is UV-curable DeloOM 6610.

[0075] Step 2: Fix the large glass pane onto the dispensing fixture, and use a water-based adhesive bonding machine to apply adhesive to the bonding surface of the large glass pane along a pre-defined path. This process is also known as damming. Figure 3 As shown. The nozzle pressure for the dam is 0.4 MPa, the injection speed of the two large holes is 22 mm / s, the injection speed of the medium and small holes is 15 mm / s, the glue dispensing speed is 0.002 mL / s, the dam line width is 1.4 ± 0.1 mm, and the distance between the edge of the dam and the edge of the hole or glass is 0.7 ± 0.1 mm.

[0076] Step 3: Pre-curing of the dam adhesive, time 12 seconds;

[0077] Step 4: Apply a second layer of adhesive, also known as filler adhesive, to the large glass surface using a water-based adhesive bonding machine. Figure 4 The filler nozzle pressure is 0.1 MPa, the syringe injection speed is 25 mm / s, the glue dispensing speed is 0.004 mL / s, and the filler line width is 1.9 ± 0.1 mm. To ensure full glue filling at the bonding location and avoid defects such as missing glue, the amount of filler glue is set greater than the amount required for bonding the large and small pieces. Excess filler glue will overflow from the hole walls and around the glass when bonding the large and small glass pieces. Figure 6 As shown;

[0078] Step 5: Attach the small glass surface with the plasma applied to the corresponding position on the large glass surface, then apply a downward pressing force of 1.2 kgf, ensuring the adhesive is evenly distributed. Pressing time: 3 seconds. The product bonding is now complete. The principle of applying force is to ensure both even distribution of the filler adhesive and that air bubbles can escape from all sides.

[0079] Step Six: Point Curing: Select a fixed point (area) within the bonding position. 4mm), then irradiate and cure it with UV light. The UV lamp wavelength range is 365nm, and the energy is 850±50mW / cm2. After absorbing the energy of 365nm UV light (ultraviolet light), the UV adhesive becomes sensitized, producing active free radicals or cations, which initiate monomer polymerization and chemical cross-linking reactions, thus exhibiting corrosion resistance. The curing time is 4±1s, reaching the pre-cured strength of the adhesive, preventing misalignment of large and small pieces during the degassing process. Step 7, Degassing: Place the bonded glass into the degassing machine, set the extreme step pressure (minimum pressure 0kgf, maximum pressure 10kgf, holding pressure for 5min for every 0.5kgf increase in step pressure) -> execute -> check the results. The experimental results of this project found that the error rate suddenly increased when the step pressure rose to 5-7kgf. This stage was recorded as a certain limit value of the server. The concurrency value (the concurrency value refers to the counter pressure applied by atmospheric pressure after reaching vacuum under set conditions) was adjusted to this limit value. Start vacuum degassing at a pressure limit of 7.0 kg / cm² and a temperature of 40°C (this temperature is the specific temperature for removing bonding bubbles found through DOE cross-validation), with an operation time of 30 mins.

[0080] It should be noted that as long as the point curing can ensure that the glass sheets of all sizes do not move during the handling process of degassing, the handling process after degassing and the process of removing adhesive, and the process of removing adhesive, until the second curing, the smaller the point curing area, the better.

[0081] Step 8, Adhesive Removal: Cover the excess adhesive around the holes and glass with a mask, then cure it with UV light. The UV lamp wavelength range is 365nm, and the energy is 850±50mW / cm2. When irradiating, start from the center and work outwards, ensuring that the light penetrates to the bonding area. The curing time is 40s to reach the initial strength of the adhesive bond. After that, perform ultrasonic cleaning. The cleaning solution used is NaOH with a pH value of 13±0.5 and an ultrasonic frequency of 40KHz. The cycle time for each station is 90±5s. After ultrasonic cleaning, the bonded glass needs to be dried at a temperature of 130±5℃ and a cycle time of 120±4s.

[0082] Step 9: Re-cur using a UV tunnel oven, with a UV lamp wavelength range of 365nm, energy of 700±100mW / cm2, and curing time of 5mins; after completion, bake at a low temperature until the free water molecules are less than 5%.

[0083] Because the monomer polymerization and chemical cross-linking of UV adhesive after irradiation with 365nm UV light will produce small molecule water, and cleaning agent will remain during the cleaning process, baking is required. The baking temperature is 120℃ and the time is 120min.

[0084] Step 10: Conduct appearance inspection and precision measurement on the above products. Products that pass the appearance inspection will proceed to the next process.

[0085] In summary, the electronic device back cover bonding method of the present invention has the following beneficial effects: The present invention utilizes UV adhesive to bond large and small glass pieces. Based on the characteristics of the UV adhesive and the areas where the large and small glass pieces need to be bonded and fixed, the bonded glass assembly is selectively irradiated with UV light. Afterwards, it is immersed in a cleaning solution that matches the characteristics of the UV adhesive to remove excess adhesive. The operation is simple, efficient, yields high, and cost-effective, making it suitable for mass production. Moreover, the present invention finds the optimal pressure value by applying a stepwise increase / decrease in pressure. Based on the found optimal pressure value, vacuum degassing is performed, which can effectively remove residual air bubbles during the adhesive application process of the large and small glass pieces. Compared with conventional methods, the yield is greatly improved, production capacity is increased, the process is simple, and equipment noise is significantly reduced. Furthermore, the positioning of the large and small glass pieces involves first positioning one large hole of each large and small glass piece, and then rotating the small glass piece so that the center line connecting the two large holes of the large glass piece coincides with the center line connecting the two large holes of the small glass piece, ensuring the bonding accuracy of the large and small glass pieces.

[0086] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0087] The terms "first," "second," and other ordinal numbers used in this specification are used to describe various constituent elements, but these constituent elements are not limited by these terms. The purpose of using these terms is solely to distinguish one constituent element from others. For example, a first constituent element may be named a second constituent element without departing from the scope of the invention, and similarly, a second constituent element may be named a first constituent element. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0088] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for bonding a back cover of an electronic device, used to bond a large glass panel on the back of the electronic device to a small glass panel located around a rear camera, characterized in that, The method includes: UV adhesive bonding step: Large and small glass pieces are bonded together using UV adhesive to obtain a bonded glass assembly; in this UV adhesive bonding step, before bonding the large and small glass pieces together, one large hole on each of the large and small glass pieces is positioned. Then, the large glass piece is fixed in place, and the small glass piece is rotated so that the center line connecting the two large holes of the large glass piece coincides with the center line connecting the two large holes of the small glass piece; the UV adhesive bonding step specifically includes: Plasma cleaning treatment is performed on the bonding surfaces of the large and small glass pieces that need to be bonded. Fix the large glass pane onto the adhesive dispensing fixture, and apply adhesive to the edges of the holes on the bonding surface of the large glass pane and around the glass to form a dam of adhesive. A second layer of adhesive is applied to the bonding surface of the large glass in the area enclosed by the dam adhesive to form a filler adhesive. The amount of filler adhesive is greater than the amount of adhesive required for bonding the large and small glass. When bonding the large and small glass, the excess filler adhesive overflows from the hole wall and the surrounding glass. Attach the bonding surface of the small glass to the corresponding position on the large glass surface, and then apply downward pressing force to complete the bonding; Debubbling step: The bonded glass assembly is placed in a debubbling machine. The optimal pressure value is found by applying a stepwise increase / decrease in pressure. Vacuum debubbling is performed based on the found optimal pressure value, and then the optimal temperature is used to remove bubbles at the bonding position. The optimal pressure value is a pressure range, and the optimal temperature can be a single temperature point or a temperature range consisting of multiple temperature points. Selective UV irradiation step: Based on the characteristics of the UV adhesive and the areas where large and small glass pieces need to be bonded and fixed, the bonded glass assembly is selectively irradiated with UV light. Etching and cleaning step: The bonded glass assembly is placed in an etching solution that matches the properties of the UV adhesive for cleaning to remove excess adhesive; The method further includes a spot curing step performed after the UV adhesive bonding step and before the debubbling step, and a full curing step after the etching and cleaning step.

2. The electronic device back cover bonding processing method according to claim 1, characterized in that, The UV adhesive is photosensitive. In the selective UV irradiation step, the UV adhesive in the area to be bonded and fixed is irradiated with UV light, and the UV adhesive that has spilled into other areas is shielded.

3. The method for bonding back covers of electronic devices according to claim 1, characterized in that, The selected UV adhesive is photosensitive; the point curing step includes selecting a pre-fixing point in the area to be bonded and fixed, irradiating the pre-fixing point with UV light for curing, and the curing time is the first irradiation time to achieve the pre-cured strength of the adhesive to prevent the large and small glass from shifting.

4. The electronic device back cover bonding processing method according to claim 1, characterized in that, The selected UV adhesive is photosensitive; The selective UV irradiation step includes: covering the holes of the large and small glass and the excess adhesive around the small glass with a mask, and irradiating the bonded glass assembly with UV light to cure it. The curing time is the second irradiation time to achieve the initial strength of the adhesive bond.

5. The method for bonding back covers of electronic devices according to claim 4, characterized in that, The complete curing step includes re-irradiating the bonded glass assembly with a UV tunnel oven for a third irradiation time to achieve the full curing strength of the adhesive, followed by low-temperature baking.

6. The method for bonding back covers of electronic devices according to claim 1, characterized in that, The method also includes a dispensing parameter pre-configuration step: Before dispensing, calculate the cured volume V1 of the UV adhesive based on the size of the dispensing area and the thickness of the cured adhesive. Calculate the volume V0 of the liquid adhesive before curing based on the volume V1 after curing: V0 = V1 / X, where X represents the content of non-volatile substances; Configure the amount of adhesive V based on the volume V0 of the liquid adhesive, so that the amount of adhesive V is slightly larger than the calculated volume V0; Calculate the dispensing height H based on the glue volume V, the dispensing width W, and the total glue length L: H = V / ( L*W); The dispensing speed is controlled based on the calculated dispensing height H.

7. The method for bonding back covers of electronic devices according to claim 1, characterized in that, The degassing step is set to an optimal temperature, which is the temperature with the best degassing effect found in advance through DOE cross-validation.

8. The method for bonding back covers of electronic devices according to claim 1, characterized in that, UV light illumination methods include: Top curing method: UV light is irradiated onto the top of the small glass; Curing method: UV light shines on the bottom of the large glass; Side curing method: UV light is irradiated on the side of the small glass.

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