CN116164781B - A MEMS sensor based on optical fiber F-P cavity and its packaging method - Google Patents

Abstract

The invention discloses a MEMS sensor based on an optical fiber F-P cavity and a packaging method thereof, and belongs to the technical field of optical fiber sensors. The MEMS sensor includes a packaging shell for packaging a sensitive chip. Collimator, the end of the threaded collimator located outside the packaging shell is fixed with an outer limit block of the collimator, and a threaded fixer is provided between the end of the package shell away from the sensitive chip and the outer limit block of the collimator, and the screw is fixed The collimator is sleeved outside the threaded collimator; the inner side wall of the packaging shell is fixed with the inner limit block of the collimator, and the center of the threaded collimator is provided with an optical fiber; the packing shell, the threaded fixer and the outer limit of the collimator The blocks are fixed by an external fixing ring and high-temperature glue, and a plurality of threaded adjustment bolts are threaded on the packaging shell. The invention can improve the stability of the connection of the collimator, reduce the offset of the optical path, and solve the problems of thermal expansion coefficient mismatch and thermal stress caused by high-temperature plastic packaging and fixing the collimator.

Description

A MEMS sensor based on optical fiber F-P cavity and its packaging method

technical field

The invention relates to the technical field of optical fiber sensors, in particular to a MEMS sensor based on an optical fiber F-P cavity and a packaging method thereof.

Background technique

The fiber collimator is mainly composed of optical fiber and collimating lens, which can convert the divergent beam emitted from the end face of ordinary silica fiber into a parallel beam, improve the working distance of the back-end optical components, thereby isolating the back-end optical components from the high temperature area, combined with high temperature resistance The sensitive structure enables measurements in high temperature environments. The packaging of collimators for optical MEMS sensors is mainly divided into two types: fiber in-line type and lens isolation type. Compared with the fiber in-line type, the lens isolation type structure scheme has higher high temperature stability, more stable optical signal transmission, small beam divergence angle, small size and light weight, etc., which is more conducive to continuous measurement work in extreme environments , so the sensor package usually chooses the lens isolation type. The lens isolation type mainly uses a fiber collimator to isolate the back-end optical components from the high-temperature area to achieve high-temperature sensor applications. Therefore, it is becoming more and more important to study the assembly method of the collimator and the sensor body.

At present, the lens-isolated F-P cavity MEMS sensors mostly use glue bonding to connect the collimator and the sensor pillar. In this way, the method of adhesive connection needs to meet: 1. After bonding, ensure that the distance between the collimator and the sensitive chip is the optimal working distance of the collimator; 2. The outgoing light point of the collimator should be located in the center of the inner hole of the ceramic tube as much as possible. This allows the sensitive chip to be centrally located on the end face of the ceramic tube. In order to ensure that the light can still be aimed at the sensitive chip after gluing, it is necessary to apply the high-temperature glue as evenly as possible. However, there are errors in the manual operation that affect the amount of glue applied, so that the collimated parallel light cannot be directed at the sensitive chip. At the same time, due to the different thermal expansion coefficients of the high-temperature glue and the sensor pillar material, a thermal expansion coefficient mismatch is likely to occur at a higher temperature, which makes the collimated optical path shift and the MEMS sensor fails. In addition, due to the residual stress caused by thermal expansion mismatch, stress concentration will also affect the reliability of the package structure.

Contents of the invention

In view of the above existing problems, the present invention aims to provide a MEMS sensor based on an optical fiber F-P cavity and its packaging method. CTE mismatch and thermal stress issues caused by fixed collimators.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A MEMS sensor based on an optical fiber F-P cavity, including a packaging shell for packaging sensitive chips, is characterized in that: the end of the packaging shell away from the sensitive chip is movably connected with a threaded collimator, and the threaded collimator is located at One end outside the packaging shell is fixed with a collimator outer limit block, and a threaded fixer is provided between the end of the package shell away from the sensitive chip and the collimator outer limit block, the A threaded fixer is sheathed outside the threaded collimator; a circle of inner limit blocks of the collimator is fixed on the inner wall of the packaging shell, and an optical fiber is penetrated through the center of the threaded collimator.

Further, the same outer fixing ring is sleeved on the outside of the packaging shell, the threaded fixer and the outer limit block of the collimator, and the outer fixing ring is threadedly connected to the threaded fixer, and the outer The fixing ring is fixed with the packaging shell and the outer limit block of the collimator through high temperature glue.

Further, three adjustment bolt positioning grooves are arranged symmetrically along the circumferential direction on the packaging shell, and a threaded adjustment bolt is threaded in each of the adjustment bolt positioning grooves, and an adjustment bolt fixing sleeve is provided on the outside of the threaded adjustment bolts. shell, each of the adjusting bolt fixing sleeves is also fixed to the outer side wall of the packaging shell by high temperature glue.

Further, the inner side wall of the outer fixing ring is provided with three relief grooves matching with the fixing sleeve of the adjusting bolt.

Further, an external thread is provided on the middle section of the outer wall of the threaded collimator, and an internal thread is provided on the inner wall of the package shell away from the end of the sensitive chip, and the threaded collimator and the package shell threaded connection.

Further, the threaded collimator is made of ceramic material.

Further, a method for packaging a MEMS sensor based on an optical fiber F-P cavity is characterized in that it comprises the following steps,

S1: Fix the packaging shell with the sensitive chip and the threaded collimator on a pair of horizontal working adjustment frames respectively, and place the light screen on the same line as the two working adjustment frames;

S2: Connect the light source with the threaded collimator, and adjust the working adjustment frame where the threaded collimator is placed, so that the light emitted by the threaded collimator reaches the center point of the light screen;

S3: Connect the threaded collimator to the optical power meter, use the optical power meter to detect the light intensity of the light emitted by the light source after passing through the sensitive chip, and then reach the optical power meter through the threaded collimator and optical fiber, and then measure the The working adjustment frame corresponding to the threaded collimator is precisely adjusted to determine the maximum return light intensity, that is, the optimal working distance of the threaded collimator;

S4: Connect and fix the threaded collimator with the packaging shell.

Further, the specific operation of step S4 includes the following steps,

S401: Sleeve the threaded collimator on the threaded collimator, adjust the working adjustment frame on which the threaded collimator is placed, and screw the threaded collimator into the packaging shell;

S402: When the threaded collimator reaches the maximum limit position, fit the threaded holder tightly to the outer limit block of the collimator;

S403: Insert the outer fixing ring from the end of the packaging shell away from the threaded collimator, and set it on the threaded holder and the outer limit block of the collimator, and reinforce it with high-temperature glue;

S404: Observe the optical power meter again. If the performance requirements cannot be met, insert a threaded adjustment bolt in the adjustment bolt positioning groove to align the optical path of the threaded collimator. After obtaining the maximum light intensity point, insert the adjustment bolt outside the threaded adjustment bolt. The casing is fixed by bolts and fixed by high-temperature glue to complete the package.

The beneficial effect of the present invention is: compared with prior art, the improvement of the present invention is that,

1. The MEMS sensor based on the optical fiber F-P cavity in the present invention is provided with threads on the outside of the collimator, and is connected with the package shell by threads, which avoids the loss of thermal expansion coefficient caused by uneven application of high-temperature glue in the prior art. The matching problem and the residual stress problem caused by the curing of high-temperature glue also increase the stability of the collimator in the cavity structure, increase the light intensity received by the receiving end, and improve the static and dynamic performance of the sensor.

2. The threaded collimator in the present invention is made of ceramic material, and adopts a threaded matching structure with the package shell, so that the stress between the threaded collimator and the package pillar is reduced, and the ceramic material with low thermal expansion coefficient can make the sensor work in super Maintain stable performance in high temperature environment.

3. In the present invention, threaded connection is used between the threaded collimator and the packaging shell, and the thread to be adapted can be calculated according to the material in advance, which improves the reliability and reduces the system error. At the same time, it needs to wait for the packaging method compared with the traditional high-temperature glue connection. The cumbersome steps of high-temperature glue curing, tempering to eliminate residual stress, and screw connection can simplify the entire packaging process and improve the packaging efficiency of the collimator and the packaging shell within a limited time.

4. The MEMS sensor based on the optical fiber F-P cavity in the present invention is also provided with an adjustment bolt positioning groove and a corresponding threaded adjustment bolt on the packaging shell, which can fine-tune the position of the threaded collimator during the packaging process, thereby improving the accuracy of the sensor. The accuracy in the sensor can improve the accuracy of the sensor.

Description of drawings

Fig. 1 is a front view of the MEMS sensor structure of the present invention.

Fig. 2 is a partially enlarged view of the structure of part A in Fig. 1 of the present invention.

Fig. 3 is a side view of the MEMS sensor structure of the present invention.

Fig. 4 is a cross-sectional view of the structure at the position corresponding to the packaging shell and the threaded adjustment bolt of the present invention.

Fig. 5 is a schematic diagram of the structure of the outer fixing ring of the present invention.

Fig. 6 is a schematic diagram of the connection relationship in the packaging process of the MEMS sensor of the present invention.

Among them: 1-sensitive chip, 2-packaging shell, 3-inner limit block of collimator, 4-thread collimator, 5-thread fixer, 6-outer fixing ring, 601-give way groove, 7-collimator Straightener outer limit block, 8-optical fiber, 9-adjusting bolt fixing sleeve, 10-threaded adjusting bolt, 11-high temperature glue, 12-adjusting bolt positioning slot, 13-working adjustment frame, 14-light source, 15-light Power meter, 16-light screen.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

A kind of MEMS sensor based on the optical fiber F-P cavity shown in accompanying drawing 1-5, comprises the packaging case 2 that is used to package sensitive chip 1, and described sensitive chip 1 is encapsulated in one end portion of described packaging case 2, and described The end of the packaging shell 2 away from the sensitive chip 1 is threadedly connected with a threaded collimator 4, and the middle section of the outer wall of the threaded collimator 4 is provided with external threads, and the packaging shell 2 is far away from the end of the sensitive chip 1. An internal thread is provided on the inner wall of one end, and the threaded collimator 4 is threadedly connected with the packaging shell 2 .

One end of the threaded collimator 4 located outside the packaging shell 2 is fixed with a collimator outer limit block 7, the threaded collimator 4 and the outer limit block 7 are integral structures, and the A threaded fixture 5 is provided between the end of the packaging shell 2 away from the sensitive chip 1 and the outer limit block 7 of the collimator. The outer wall of the threaded fixture 5 is provided with external threads, and the inner wall is smooth. design, can be sleeved on the outside of the threaded collimator 4, and can slide along the long axis direction of the threaded collimator 4; diameters are the same; the inside wall of the packaging shell 2 is fixed with a circle of collimator inner limit block 3 for limiting the front end position of the threaded collimator 4, and the inner limit block 3 of the collimator The function is to prevent the threaded collimator 4 from pushing inwardly against the sensitive chip 1 too much; the center of the threaded collimator 4 is provided with an optical fiber 8 .

The same outer fixing ring 6 is sleeved outside the package shell 2, the threaded holder 5 and the outer limit block 7 of the collimator, and the inner side wall of the outer fixing ring 6 is provided with the outer side wall of the threaded holder 5. The external thread on the top is matched with the internal thread, so that the threaded connection between the outer fixing ring 6 and the threaded holder 5 is achieved, and the outer fixing ring 6 is also aligned with the packaging shell 2 and the collimation through the high temperature glue 11 The outer limit block 7 of the collimator is fixed; in order to reduce the impact between the outer limit block 7 of the collimator and the threaded holder 5, a side of the outer limit block 7 of the collimator near the threaded collimator 4 is provided with The rubber pad, the rubber pad can also be used as a substrate to play a sealing role.

The packaging shell 2 is symmetrically provided with three adjusting bolt positioning grooves 12 along the circumferential direction. The circular surface where the three adjusting bolt positioning grooves 12 are located is located in front of the threaded collimator 4 provided with the external thread part. Each of the adjusting bolts The positioning grooves 12 are threadedly connected with threaded adjustment bolts 10, and outside the threaded adjustment bolts 10 are provided with adjusting bolt fixing casings 9, and each of the adjusting bolt fixing casings 9 is also connected to the packaging casing through a high-temperature glue 11. 2 is fixed on the outside wall.

In order to prevent the adjusting bolt fixing sleeve 9 from blocking the outer fixing ring 6, three relief grooves 601 matching the adjusting bolt fixing sleeve 9 are provided on the inner side wall of the outer fixing ring 6, so as to facilitate the outer fixing The ring 6 is sheathed from the front end of the threaded collimator 4 to the rear end of the threaded collimator 4 .

Preferably, the threaded collimator 4 is made of ceramic material, which has a small coefficient of thermal expansion and can be self-lubricated to increase the reliability and strength of the connection.

Example 2

Embodiment 2 provides a method for packaging the MEMS sensor based on the optical fiber F-P cavity described in Embodiment 1, specifically comprising the following steps,

S1: Fix the packaging shell 2 and the threaded collimator 4 packaged with the sensitive chip 1 on a pair of horizontally placed working adjustment frames 13 respectively. The starting distance between the packaged shell 2 and the threaded collimator 4 should be the designed working distance As the standard, align the light by adjusting the positions of the two work adjustment frames 13; place the light screen 16 on the same straight line as the two work adjustment frames 13, as described in Figure 6;

S2: Connect the light source 14 to the threaded collimator 4, adjust the working adjustment frame 13 on which the threaded collimator 4 is placed, so that the light emitted by the threaded collimator 4 reaches the center point of the light screen 16;

Connect the light source 14 of visible light to the threaded collimator 4 to determine the return light position of the sensitive chip 1, and mainly use the reflection law of light when facing the light. First, ensure that the light spot emitted by the threaded collimator 4 hits the middle of the sensitive chip 1. At this time, the sensitivity of the sensor is the highest, and then follow-up adjustments are made according to the position of the light returned by the sensitive chip 1.

Then, looking at the sensitive chip 1 from the threaded collimator 4, when the position of the light spot is on the left (right) of the light screen 16, it means that the incident light angle of the threaded collimator 4 is too large on the XOY plane. The working adjustment frame 13 corresponding to the device 4 feeds outward (inside) along the Z axis, and at the same time adjusts the working adjustment frame 13 to feed inward (outside) along the Y axis direction, so that the deviated light spot can be adjusted to the center.

S3: Connect the threaded collimator 4 to the optical power meter 15, the light emitted by the light source 14 through the optical power meter 15 passes through the return light after the sensitive chip 1, and then passes through the threaded collimator 4 and the optical fiber 8 to reach the optical power meter 15 The light intensity is detected, and then the working adjustment frame 13 corresponding to the threaded collimator 4 is accurately adjusted to determine the maximum return light intensity, that is, the optimal working distance of the threaded collimator 4;

In step S2, after initially determining the relative positions of the threaded collimator 4 and the packaging shell 2 using visible light, the threaded collimator 4 is connected to the optical power meter 15, and the light emitted by the light source 14 through the optical power meter 15 passes through the sensitive chip 1 The returned light is then detected by the light intensity reaching the optical power meter 15 through the threaded collimator 4 and the optical fiber 8, and the signal is the best when the returned light power is maximum.

After the adjustment at a certain distance, adjust the position of the working adjustment frame 13, change the relative distance between the sensitive chip 1 and the thread collimator 4, and continue fine-tuning to obtain the return optical power values at different distances. The distance corresponding to the maximum value is the thread collimator. Straightener 4 optimal working distance.

If it does not reach the maximum or the optical power does not change, it is necessary to repeat the visible light alignment or check whether the detection system is working effectively.

S4: Connect and fix the threaded collimator 4 with the packaging shell 2;

Specifically, S401: Set the threaded fixer 5 on the threaded collimator 4, adjust the working adjustment frame 13 on which the threaded collimator 4 is placed, and screw the threaded collimator 4 into the packaging shell 2; here It should be noted that the working adjustment frame 13 is provided with a knob, which can adjust the position of the threaded collimator 4 on the X-axis, Y-axis and Z-axis. This working adjustment frame 13 is a prior art, and its specific structure is Do not repeat in the application.

When connecting the threaded collimator 4 to the packaging shell 2, the threaded collimator 4 is connected to red light for observing the position of the light-emitting point. When the sensor is packaged, pay attention to using red light to observe and adjust the position of the light spot, and try to ensure that the light spot is located in the center of the sensitive chip 1 to ensure the performance of the sensor. Adjust its relative position to ensure that the threaded collimator 4 and the inner hole of the package shell 2 are on the same axis, that is, the light passes through the threaded collimator 4 and the package shell 2, and a clear and bright red light spot can be seen on the light screen 16 (When the light passes through the package shell and reaches the top of the sensitive chip, light interference occurs), and the light spot can be emitted from the center of the inner hole of the package shell 2 .

S402: When the threaded collimator 4 reaches the maximum limit position, the threaded holder 5 is closely attached to the outer limit block 7 of the collimator;

S403: Insert the outer fixing ring 6 from the end of the packaging shell 2 away from the threaded collimator 4, and set it on the threaded holder 5 and the outer limit block 7 of the collimator, and reinforce it with high-temperature glue 11;

S404: Observe the optical power meter 15 again. If the performance requirements cannot be met, insert the threaded adjustment bolt 10 in the adjustment bolt positioning groove 12 to align the optical path of the threaded collimator 4. After obtaining the maximum light intensity point, adjust the The bolt 10 is inserted into the adjusting bolt fixing sleeve 9 and fixed by high temperature glue 11 to complete the package.

After the packaging is completed, the pressure performance and temperature resistance performance of the sensor need to be analyzed. If the performance requirements cannot be met, the above packaging process needs to be completed again to ensure that the sensor can work efficiently.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (2)

1. A packaging method for a MEMS sensor based on an optical fiber F-P cavity, the MEMS sensor based on an optical fiber F-P cavity includes a packaging shell (2) for packaging a sensitive chip (1), and the packaging shell (2) is far away from the One end of the sensitive chip (1) is movably connected to a threaded collimator (4), and one end of the threaded collimator (4) located outside the packaging shell (2) is fixed with a collimator outer limit block (7 ), and the end of the packaging shell (2) away from the sensitive chip (1) and the outer limit block of the collimator (7) is provided with a threaded holder (5), the threaded holder ( 5) Set outside the threaded collimator (4); a ring of inner limit blocks (3) of the collimator is fixed on the inner wall of the packaging shell (2), and the threaded collimator (4) ) is provided with an optical fiber (8) through the center; The same outer fixing ring (6) is sleeved on the outside of the packaging shell (2), the threaded fixer (5) and the outer limit block (7) of the collimator, and the outer fixing ring (6) and the The threaded fixers (5) are threadedly connected, and the outer fixing ring (6) is fixed with the packaging shell (2) and the collimator outer limit block (7) by high temperature glue (11); The packaging shell (2) is provided with three adjusting bolt positioning grooves (12) symmetrically along the circumferential direction, each of the adjusting bolt positioning grooves (12) is threadedly connected with a threaded adjusting bolt (10), and the threaded adjusting bolt The bolts (10) are provided with adjusting bolt fixing casings (9), and each adjusting bolt fixing casing (9) is also fixed to the outer side wall of the packaging casing (2) by high temperature glue (11); Three relief slots (601) matching the adjusting bolt fixing sleeve (9) are opened on the inner side wall of the outer fixing ring (6); An external thread is provided on the middle section of the outer wall of the threaded collimator (4), and an internal thread is provided on the inner wall of the package shell (2) far away from the end of the sensitive chip (1), and the thread collimation The device (4) is threadedly connected with the packaging shell (2); It is characterized in that the packaging method includes the following steps, S1: Fix the packaging case (2) with the sensitive chip (1) and the threaded collimator (4) respectively on a pair of horizontally placed working adjustment frames (13), place the light screen (16) and the two working The adjusting frame (13) is on the same straight line; S2: Connect the light source (14) to the threaded collimator (4), adjust the working adjustment frame (13) where the threaded collimator (4) is placed, so that the light emitted by the threaded collimator (4) reaches the light screen (16) center point; S3: Connect the threaded collimator (4) to the optical power meter (15), and the light emitted by the light source (14) through the optical power meter (15) passes through the sensitive chip (1) to return light, and then passes through the threaded collimation Detect the light intensity reaching the optical power meter (15) by the optical fiber (4) and the optical fiber (8), and then accurately adjust the working adjustment frame (13) corresponding to the threaded collimator (4) to determine the maximum returning light intensity. That is, the optimal working distance of the threaded collimator (4); S4: Connect and fix the threaded collimator (4) with the packaging shell (2); The concrete operation of step S4 comprises the following steps, S401: Put the threaded fixer (5) on the threaded collimator (4), adjust the working adjustment frame (13) where the threaded collimator (4) is placed, screw the threaded collimator (4) into Inside the encapsulation shell (2); S402: When the threaded collimator (4) reaches the maximum limit, fit the threaded holder (5) closely to the outer limit block (7) of the collimator; S403: Insert the outer fixing ring (6) from the end of the packaging shell (2) away from the threaded collimator (4), and set it on the threaded holder (5) and the outer limit block of the collimator (7) , reinforced by high temperature glue (11); S404: Observe the optical power meter (15) again. If the performance requirements cannot be met, insert the threaded adjustment bolt (10) into the adjustment bolt positioning groove (12) to align the optical path of the threaded collimator (4), and obtain After the maximum light intensity point, insert the adjusting bolt fixing sleeve (9) outside the threaded adjusting bolt (10), and fix it with high temperature glue (11) to complete the packaging. 2. The packaging method of a MEMS sensor based on an optical fiber F-P cavity according to claim 1, characterized in that: the threaded collimator (4) is made of ceramic material.

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