A method for controlling the consistency of the thickness of the glue layer of a light receiving device

Abstract

The application provides a method for controlling the consistency of the glue layer thickness of a light receiving device, comprising the following steps: S1, arranging a short-focus lens on a PCB circuit board of the light receiving device through a lens substrate, and the short-focus lens is arranged above the photodiode; the distance between the spherical vertex of the short-focus lens and the photosensitive surface of the photodiode is a preset distance; S2, arranging an integrated silicon lens and prism above the short-focus lens through a support frame, and the prism is located above the short-focus lens and the photodiode; S3, arranging the collimator through a passive alignment patch method; S4, after the coupling of the light receiving device is realized, the integrated silicon lens and prism are fixed by point gluing. The application can effectively ensure that the glue thickness of the light receiving device remains consistent, effectively improve the reliability of the product, reduce the production cost, and further simplify the production process and flow.

Description

Technical Field

[0001] This invention relates to the field of optical communication devices, and more particularly to a method for controlling the uniformity of adhesive layer thickness in optical receiving devices. Background Technology

[0002] In the optical communication industry, high-speed optical receivers typically use glass lenses to focus the light beam onto the photosensitive surface of a photodiode (PD). These glass lenses are generally molded, resulting in lenses with surface parameters that closely match the design values. However, molded glass lenses are expensive; for example, a single molded aspherical glass lens can cost around 40 yuan. Currently, the price of optical modules in the optical communication industry is decreasing year by year, so manufacturers are seeking to replace glass lenses with cheaper alternatives. Silicon is currently the most widely used material in the semiconductor industry. It is not only inexpensive but also transparent in the infrared band used in optical communication, with a refractive index reaching 3.4, making it very suitable for manufacturing lenses for the optical communication industry. Therefore, many manufacturers are currently using silicon lenses to replace glass lenses to reasonably reduce costs.

[0003] However, silicon lenses are generally fabricated using wet etching processes. Due to limitations in the manufacturing process, it is difficult to accurately determine the radius of curvature of silicon lenses. Currently, the radius of curvature tolerance of silicon lenses is controlled at around 5%. This deviation in radius of curvature leads to different back intercept lengths for different lenses. For conventional optical paths of receiving devices, to simplify the coupling process, the silicon lens and prism are usually bonded together as a single unit. Therefore, if the curvature of the silicon lens is not accurately determined, the thickness of the adhesive layer for both the silicon lens and prism needs to be adjusted to accommodate the back intercept variation caused by the radius of curvature deviation. For example, for a silicon lens with a radius of curvature of 4mm, a 5% radius of curvature tolerance will result in a back intercept variation of 75μm. This 75μm back intercept variation corresponds to two possible changes in adhesive thickness: first, even if the adhesive thickness under the lens is reduced to its thinnest possible position, it may not achieve optimal coupling; second, the adhesive thickness may be increased by 75μm to meet the coupling requirements, but even if coupling is achieved, this can lead to product reliability failure in actual production.

[0004] To address this issue, the conventional solution for the large curvature tolerance of silicon lenses is to manufacture spacers of various thicknesses to meet coupling requirements. However, this approach requires suppliers to test the curvature radii of a large number of silicon lenses. This leads to an increase in the cost of silicon lenses and also requires users to prepare spacers of various thicknesses simultaneously. Consequently, the risk of material mixing is difficult to avoid in actual production, which is not conducive to material preparation or ensuring product consistency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for controlling the uniformity of adhesive layer thickness in a light receiver device. The aim is to reduce the influence of the radius of curvature of the silicon lens on the adhesive thickness by optimizing the optical path design of the light receiver device. This is beneficial to reducing the production cost of the light receiver device and effectively avoids the drawback of inconsistent adhesive thickness caused by back intercept offset after the introduction of the silicon lens, thereby improving the reliability of the product.

[0006] To address this issue, the present invention provides a method for controlling the uniformity of adhesive layer thickness in a light-receiving device, comprising the following steps: Step S1: A short-focal-length lens is placed on the PCB circuit board of the light receiving device using a lens substrate. The lens substrate is placed at the end of the photodiode of the light receiving device near the collimator, and the short-focal-length lens is placed above the photodiode. The distance between the apex of the spherical surface of the short-focal-length lens and the photosensitive surface of the photodiode is a preset distance, and the back intercept of the short-focal-length lens is a preset back intercept. Step S2: The integrated silicon lens and prism are positioned above the short focal length lens using a support frame. The silicon lens is positioned at the end of the prism near the collimator, and the prism is positioned above the short focal length lens and the photodiode. Step S3: Set the collimator using a passive alignment patch method; Step S4: After coupling the integrated silicon lens and prism to the light receiving device by clamping the coupling fixture of the coupling device, the integrated silicon lens and prism are fixed with adhesive.

[0007] A further improvement of the present invention is that the preset distance is greater than the back focal length variation value of the silicon lens, wherein the back focal length variation value of the silicon lens refers to the lens back focal length variation value caused by the curvature radius tolerance of the silicon lens.

[0008] A further improvement of the present invention is that the preset distance is 10 μm greater than the back cutoff variation value of the silicon lens.

[0009] A further improvement of the present invention is that the preset distance is 85μm.

[0010] A further improvement of the present invention is that the value range of the preset back intercept is 0.08mm to 0.13mm.

[0011] A further improvement of the present invention is that the preset back intercept ranges from 0.1 mm.

[0012] A further improvement of the present invention is that the short focal length lens is mounted on the lens substrate, and the thickness of the lens substrate is the sum of the thickness of the photodiode and the preset distance.

[0013] A further improvement of the present invention is that the support frame is a semi-enclosed hollow support structure, the opening of the support frame is located on the side close to the collimator, and the integrated silicon lens and prism are located at the opening of the support frame.

[0014] A further improvement of the present invention is that the bottom of the opening of the support frame is a receiving cavity, and the inner diameter of the receiving cavity is greater than the top width of the opening.

[0015] A further improvement of the present invention is that the transimpedance amplifier of the light receiving device is disposed in the receiving cavity and on the side of the photodiode away from the lens substrate.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: a short-focal-length lens is disposed on the PCB circuit board of the light receiver device by means of a lens substrate, the lens substrate is disposed at the end of the photodiode of the light receiver device near the collimator, and the short-focal-length lens is disposed above the photodiode, so as to optimize the optical path design of the light receiver device. The combination of long and short-focal-length lenses replaces the traditional single-lens mode, so as to effectively avoid the drawback of inconsistent adhesive thickness of the light device caused by back-cutoff shift after the introduction of silicon lenses, reduce the influence of back-cutoff deviation caused by single-lens curvature radius deviation, ensure the consistency of adhesive thickness of the light receiver device, and effectively improve the reliability of the product.

[0017] Based on this, the present invention eliminates the need for suppliers to conduct extensive testing of the curvature radius distribution of silicon lenses before shipment, simplifying the production process and workflow of silicon lenses, thereby reducing lens costs; it also eliminates the need to match shims of corresponding thicknesses based on the curvature distribution data of silicon lenses, so as to uniformly prepare inventory according to the theoretically designed shim thickness, thus effectively avoiding the risk of material mixing caused by using shims of different thicknesses, and effectively simplifying the product's production process and workflow; the introduction of short-focal-length lenses also increases the tolerance of the entire optical system, and collimators can be attached using passive alignment, avoiding the investment in high-precision coupling equipment and effectively saving equipment costs for the project. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the workflow of one embodiment of the present invention; Figure 2 This is a schematic diagram of the optical path according to an embodiment of the present invention; Figure 3 This is a cross-sectional structural schematic diagram of an optical receiving device according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a silicon lens, prism, and support frame according to an embodiment of the present invention.

[0019] Figure labels: 1-Lens substrate; 2-Short focal length lens; 3-PCB circuit board; 4-Photodiode; 5-Collimator; 6-Support frame; 601-Opening; 602-Receiving cavity; 7-Silicon lens; 8-Prism; 9-Transimpedance amplifier. Implementation

[0020] In the description of this invention, if directional descriptions are involved, such as "up," "down," "front," "back," "left," "right," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, it is only for the convenience of describing the invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. If a technical feature is referred to as "set," "fixed," "connected," or "installed" on another technical feature, it can be directly set, fixed, or connected to the other technical feature, or it can be indirectly set, fixed, connected, or installed on the other technical feature.

[0021] In the description of this invention, the term "several" means one or more; the term "multiple" means two or more; the terms "greater than," "less than," and "exceeding" are all understood to exclude the stated number; and the terms "above," "below," and "within" are all understood to include the stated number. The terms "first," "second," etc., are understood to be used only to distinguish identical or similar technical feature names, and should not be construed as implying / indicating the relative importance of the technical features, the number of technical features, or the sequential relationship between the technical features.

[0022] The preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0023] like Figures 1 to 4 As shown, this embodiment provides a method for controlling the uniformity of adhesive layer thickness in a light-receiving device, including the following steps: Step S1: The short-focal-length lens 2 is mounted on the PCB circuit board 3 of the light receiving device via the lens substrate 1. The lens substrate 1 is positioned at the end of the photodiode 4 of the light receiving device near the collimator 5, and the short-focal-length lens 2 is positioned above the photodiode 4. The distance between the spherical vertex of the short-focal-length lens 2 and the photosensitive surface of the photodiode 4 is a preset distance, and the back focal length of the short-focal-length lens 2 is a preset back focal length. The photodiode 4 is also called a PD. The lens substrate 1 is also called a lens submount and is used to support the short-focal-length lens 2. The short-focal-length lens 2 is also called a short-focal-length lens, and the short-focal-length lens 2 is preferably a short-focal-length silicon lens. The preset distance is a preset distance value greater than 0. The preset back focal length refers to the preset back focal length value of the short-focal-length lens 2, which can be adjusted according to actual conditions and requirements. Step S2: The integrated silicon lens 7 and prism 8 are positioned above the short focal length lens 2 by the support frame 6. The silicon lens 7 is positioned at the end of the prism 8 near the collimator 5. The prism 8 is located above the short focal length lens 2 and the photodiode 4. The silicon lens 7 is a converging lens, and the silicon lens 7 and prism 8 preferably adopt an integrated structure. Step S3: The collimator 5 is set by a passive alignment patch method; Step S4: After coupling the integrated silicon lens 7 and prism 8 to the light receiving device by clamping the coupling fixture of the coupling device, the integrated silicon lens 7 and prism 8 are fixed with adhesive.

[0024] This embodiment addresses the problems encountered in applications using silicon lenses 7 to implement optical receivers. A short-focal-length lens is attached at a predetermined distance above the photodiode 4 to reduce the impact of inaccurate curvature radius of the silicon lens 7 on the adhesive thickness. This predetermined distance is a range that can be pre-set and adjusted. The size of this range preferably varies according to the back focal length of the short-focal-length lens 2 used. Specifically: after selecting a lens from existing short-focal-length lenses as the short-focal-length lens 2, the predetermined distance can be determined by ray tracing using optical design software; alternatively, a predetermined distance can be determined first based on the optical module manufacturing process, and then the back focal length of the short-focal-length lens 2 can be designed.

[0025] More preferably, in this embodiment, the preset distance is greater than the back focal length variation of the silicon lens 7. The back focal length variation of the silicon lens 7 refers to the variation in lens back focal length caused by the curvature radius tolerance of the silicon lens 7. The preset distance and the back focal length variation of the silicon lens 7 are not directly related. This application utilizes the principle that the back focal length of the combined lens is insensitive to the back focal length variation of a single lens to reduce the impact of inaccurate curvature radius measurement of the silicon lens 7. The preset distance can be 10 μm larger than the back focal length variation of the silicon lens 7 as one preferred implementation. Therefore, when the curvature radius tolerance of the silicon lens 7 causes a back focal length variation of 75 μm, the preset distance in this embodiment can be 85 μm.

[0026] In this embodiment, the back focal length of the short-focal-length lens 2 is smaller than that of the silicon lens 7. The range of the back focal length of the short-focal-length lens 2 can be adjusted according to actual needs. The smaller the back focal length, the better. However, a back focal length that is too small is not conducive to the actual manufacturing of the lens. Therefore, it is necessary to select a range that is relatively balanced between production cost and value. In this embodiment, the preset back focal length range is 0.08mm to 0.13mm; when the preset back focal length range is 0.1mm, the overall effect is most balanced and the cost is reasonable.

[0027] like Figure 3 As shown, in this embodiment, the short-focal-length lens 2 is mounted on the lens substrate 1. The thickness of the lens substrate 1 is the sum of the thickness of the photodiode 4 and the preset distance. Specifically, in this embodiment, a short-focal-length lens 2 with a back focal length of approximately 0.1 mm is preferably mounted above the photodiode 4 (PD). The height between the spherical vertex of the short-focal-length lens 2 and the photosensitive surface of the photodiode 4 is 85 μm, with the error controlled within ±10 μm to avoid yield loss in actual production.

[0028] Since the short focal length lens 2 described in this embodiment is attached to the PCB circuit board 3 via the lens substrate 1, there is no space above the photodiode 4 for the support frame 6 for the integrated silicon lens 7 and prism 8. Therefore, the integrated silicon lens 7 and prism 8 described in this embodiment need to be attached to the PCB circuit board 3 using the support frame 5 located on the other side, in order to ensure the reliability of the optical path design and the avoidance design.

[0029] like Figures 2 to 4As shown, the support frame 6 in this embodiment is a semi-enclosed hollow support structure. The opening 601 of the support frame 6 is located on the side close to the collimator 5. The integrated silicon lens 7 and prism 8 are located at the opening 601 of the support frame 6 to form a reliable optical path design at the receiving end, and to effectively achieve the functions of space avoidance design and support protection. More preferably, the bottom of the opening 601 of the support frame 6 in this embodiment is a receiving cavity 602. The inner diameter of the receiving cavity 602 is larger than the top width of the opening 601, so as to better realize the arrangement of various components on the PCB circuit board 3, and the support frame 6 provides good protection.

[0030] In this embodiment, the transimpedance amplifier 9 of the optical receiver is disposed within the receiving cavity 602 and on the side of the photodiode 4 away from the lens substrate 1. The transimpedance amplifier 9 refers to the optical receiver TIA, so as to make reasonable use of the bottom space of the support frame 6 to arrange and protect various optical devices, resulting in a more reasonable and efficient overall structural design.

[0031] Because the short-focal-length lens 2 is positioned above the photodiode 4, the coupling tolerance of the system containing the light receiving device is improved, and the collimator 5 can be attached using a passive alignment method. Therefore, in step S3, this embodiment preferably first adjusts the CCD magnification to 200x, then loads the product outline diagram converted from the 3D model of the light receiving device onto the CCD. After displaying the product outline diagram on the screen, the collimator 5 is aligned with the outline diagram and attached to the corresponding position, thus completing the setting of the collimator 5 through a passive alignment attachment method. The CCD refers to a camera lens.

[0032] In step S4, after the collimator 5 is attached, the light receiving device is placed on the coupling device. The integrated silicon lens 7 and prism 8 are clamped by the coupling fixture of the coupling device and coupled as a whole. The coupling process is consistent with the existing optical device coupling process, so it will not be described in detail. Then, with the target of maximizing the corresponding current of the photodiode 4, the integrated silicon lens 7 and prism 8 are coupled to the optimal position and then glued to fix them. Thus, the light receiving device is obtained. The coupling device refers to an existing optical device coupling device / platform.

[0033] In summary, this embodiment uses a lens substrate 1 to mount a short-focal-length lens 2 onto the PCB circuit board 3 of the light receiver device. The lens substrate 1 is positioned at the end of the photodiode 4 of the light receiver device near the collimator 5, and the short-focal-length lens 2 is positioned above the photodiode 4. This optimizes the optical path design of the light receiver device. By combining long and short-focal-length lenses, the traditional single-lens approach is replaced, effectively avoiding the drawback of inconsistent adhesive thickness caused by back-cutoff shift after introducing the silicon lens 7. This reduces the impact of back-cutoff deviation caused by curvature radius deviation of a single lens, ensuring consistent adhesive thickness of the light receiver device and effectively improving product reliability.

[0034] Based on this, this embodiment eliminates the need for suppliers to conduct extensive testing of the curvature radius distribution of the silicon lens 7 before shipment, simplifying the production process and workflow of the silicon lens 7, thereby reducing the cost of the lens; it also eliminates the need to match the corresponding thickness of the shims based on the curvature distribution data of the silicon lens 7, so that the shims can be stocked according to the theoretically designed thickness, thus effectively avoiding the risk of mixing materials caused by using shims of different thicknesses, and effectively simplifying the production process and workflow of the product; the introduction of the short focal length lens 2 also increases the tolerance of the entire optical system, and the collimator 5 can be attached by passive alignment, avoiding the investment in high-precision coupling equipment, effectively saving the equipment cost of the project.

[0035] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the uniformity of adhesive layer thickness in a light-receiving device, characterized in that, Includes the following steps: Step S1: A short-focal-length lens is placed on the PCB circuit board of the light receiving device using a lens substrate. The lens substrate is placed at the end of the photodiode of the light receiving device near the collimator, and the short-focal-length lens is placed above the photodiode. The distance between the apex of the spherical surface of the short-focal-length lens and the photosensitive surface of the photodiode is a preset distance, and the back intercept of the short-focal-length lens is a preset back intercept. Step S2: The integrated silicon lens and prism are positioned above the short focal length lens using a support frame. The silicon lens is positioned at the end of the prism near the collimator, and the prism is positioned above the short focal length lens and the photodiode. Step S3: Set the collimator using a passive alignment patch method; Step S4: After coupling the integrated silicon lens and prism to the light receiving device by clamping the coupling fixture of the coupling device, the integrated silicon lens and prism are fixed with adhesive.

2. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to claim 1, characterized in that, The preset distance is greater than the back intercept variation value of the silicon lens, where the back intercept variation value of the silicon lens refers to the lens back intercept variation value caused by the curvature radius tolerance of the silicon lens.

3. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to claim 2, characterized in that, The preset distance is 10 μm greater than the back cutoff variation of the silicon lens.

4. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to claim 2, characterized in that, The preset distance is 85μm.

5. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to any one of claims 1 to 4, characterized in that, The preset back intercept ranges from 0.08mm to 0.13mm.

6. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to claim 5, characterized in that, The preset back intercept ranges from 0.1 mm.

7. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to any one of claims 1 to 4, characterized in that, The short-focal-length lens is mounted on the lens substrate, and the thickness of the lens substrate is the sum of the thickness of the photodiode and the preset distance.

8. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to any one of claims 1 to 4, characterized in that, The support frame is a semi-enclosed hollow support structure, with the opening of the support frame located on the side near the collimator, and the integrated silicon lens and prism located at the opening of the support frame.

9. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to claim 8, characterized in that, The bottom of the opening of the support frame is a receiving cavity, and the inner diameter of the receiving cavity is larger than the top width of the opening.

10. The method for controlling the uniformity of adhesive layer thickness in a light-receiving device according to claim 9, characterized in that, The transimpedance amplifier of the optical receiving device is disposed within the cavity and on the side of the photodiode away from the lens substrate.

Images