Fine adjustment method of surface crystal

Abstract

The invention discloses a surface crystal fine tuning method, which comprises the following steps of: taking a roughly-tuned whole-board surface crystal resonance piece, measuring the frequency of each surface crystal in vacuum, uploading the frequency to a server for recording, measuring the frequency of each surface crystal again in an atmospheric environment during fine tuning, and calculating the frequency of each surface crystal based on the difference value between the measured value of each surface crystal in vacuum and the measured value of each surface crystal under atmospheric pressure. Calculating a fine tuning frequency target value of each surface crystal in the atmospheric environment; then amp is carried out by using laser in an atmospheric environment; fine adjustment is conducted on the galvanometer, and high-purity nitrogen is adopted for cooling in the fine adjustment process to avoid cracking of a crystal oscillator; the method is low in cost and high in efficiency, and the frequency consistency of sealed and welded products is good.

Description

Technical Field

[0001] The present invention relates to the field of production technology of quartz crystal oscillators, and specifically to a method for fine-tuning a crystal. Background Art

[0002] The quartz crystal oscillator in a quartz clock is of tuning fork type, and its most commonly used standard frequency is 32.768kHz. The accuracy of the crystal oscillator frequency determines the accuracy of the clock's travel.

[0003] During the processing of quartz crystal oscillators, usually after the chip is fixed to the base, a fine adjustment is required before the final packaging to ensure the accuracy of the frequency of the final product.

[0004] Existing fine-tuning methods mainly include the following two methods:

[0005] Measurement and laser fine-tuning under atmospheric pressure;

[0006] 1.1 Principle: A high-energy laser beam is irradiated onto the silver layer at the end of the crystal, causing it to melt and vaporize, forming a groove of a certain depth, thereby achieving the purpose of etching the material. The laser beam divergence angle can be less than 1 milliarc, the spot diameter can be in the micrometer range, the action time can be as short as nanoseconds and picoseconds, the power can be continuously output, and it is easy to control. It is easy to combine precision machinery, precision measurement technology and electronic computers to achieve high automation and high precision requirements for processing.

[0007] 1.2 The advantages are: a. High frequency modulation efficiency, the reason is: using laser + galvanometer device for frequency adjustment: laser + galvanometer moves fast and has adjustable power. Using high-frequency short-pulse laser for laser etching, the pulse laser can be used to focus the laser beam into a spot of several hundred nanometers to 20 microns through optical fiber focusing. After focusing, the spot reaches the removal energy value of the material, and the high-speed scanning galvanometer system is used for precise and rapid scanning to simplify the etching process, reduce costs and improve accuracy. b. No pollution, add a blowing and absorbing pollution collection device, blow and absorb the laser etching position under atmospheric pressure to avoid the gaseous substances generated by laser etching from being adsorbed on the silver layer of other wafers that have been adjusted.

[0008] 1.3 Disadvantage: poor frequency consistency after sealing. The reason is: the surface crystal frequency under vacuum is different from that under atmospheric pressure, and the frequency difference between vacuum and atmospheric pressure tests of each product is also different. For example, for products with a test value of 0ppm under atmospheric pressure, the frequency dispersion (vacuum state) after sealing can reach 0~±50ppm. The smaller the product, the greater the frequency dispersion after sealing.

[0009] 1.4 Because laser etching causes thermal stress concentration and is prone to cracks, etching in an atmospheric environment allows for cooling while blowing inert gas, with a maximum adjustment of 2000ppm. However, if laser etching is performed under vacuum, the heat cannot be removed by blowing inert gas, so the adjustment can only be limited to 500ppm, otherwise cracks may easily occur.

[0010] 2. Measurement and ion etching under vacuum;

[0011] 2.1 Principle: Ion etching is a purely physical etching method that uses a high-energy ion beam to directly bombard the surface of the material and remove the material by sputtering. The principles are as follows: a. Ion generation: Through the principle of glow discharge, the gas (such as argon) is ionized to form ions. b. Ion acceleration: Under the action of the electric field, the ions are accelerated and form a beam of ion flow. c. Ion bombardment: The high-energy ion beam bombards the surface of the material, causing the kinetic energy of the atoms on the surface of the material to increase and eventually be sputtered out. d. Material removal: The sputtered material atoms or molecules are extracted by a vacuum pump and removed from the reaction chamber.

[0012] 2.2 Advantages: good frequency consistency after compression sealing, the reason is: etching and sealing welding are measured under vacuum. The test value of etching frequency is 0ppm, and the frequency after compression sealing (vacuum state) is discrete to 0~±5ppm.

[0013] 2.3 Disadvantages: The equipment cost is high, which is 3-4 times that of laser etching equipment under atmospheric pressure, but the working efficiency is only about 50% of the laser etching solution under atmospheric pressure.

[0014] The frequency consistency of high-frequency (MHz) crystal oscillators in a vacuum environment is better than that in an atmospheric environment, but the frequency of a tuning fork crystal is only 32KHz. Tests have shown that the frequency characteristics in a vacuum are not consistent with those in an atmospheric environment, and the discreteness is large. The existing fine-tuning scheme cannot efficiently and accurately fine-tune the tuning fork crystal oscillator. Summary of the invention

[0015] The technical problem to be solved by the present invention is to provide an efficient, low-cost, high-precision tuning method for tuning fork type watch crystal.

[0016] The specific technical solution of the present invention to solve the above technical problems is:

[0017] S1. Take the whole plate crystal resonator after rough adjustment, read the substrate ID of the whole plate crystal resonator, measure it in a vacuum environment, obtain the frequency of each crystal in a vacuum environment, referred to as the vacuum frequency after rough adjustment, represented by F3, and record the substrate ID, the position of the crystal on the whole plate and the respective vacuum frequency F3 after rough adjustment in the server. The whole plate crystal is processed based on the whole plate base, each whole plate base has a unique substrate ID, and the position of each crystal resonator on the whole plate base can be recorded, so the server can accurately record each crystal and its vacuum frequency after rough adjustment;

[0018] S2, placing the whole plate of crystal resonators into the fine-tuning machine, and using the measuring device in the fine-tuning machine to measure the whole plate of crystal resonators again under the atmospheric pressure environment, to obtain the frequency of each crystal under the atmospheric environment, referred to as the standard pressure frequency after coarse adjustment, represented by F2, and uploaded to the server for recording;

[0019] S3, based on the data recorded by the server, the difference between the vacuum frequency F3 after coarse adjustment and the standard voltage frequency F2 after coarse adjustment of each crystal resonator is compared one by one, and the difference between the vacuum frequency F3 after coarse adjustment and the standard voltage frequency F2 after coarse adjustment of each crystal resonator is obtained, which is referred to as the deviation frequency and is represented by ΔF2, that is, ΔF2 = F3-F2; write to the server; because

[0020] S4, calculate the process ID fine-tuning target value F1, the expected precise frequency F0 of each crystal resonator in a vacuum environment after vacuum sealing is 32.768KHz, the target value F1 of the fine-tuning frequency under atmospheric pressure, and the fine-tuning amount ΔF1 under atmospheric pressure environment is F1-F2;

[0021] Then: F1 = F0 - ΔF2

[0022] =F0-F3+F2;

[0023] S5. The target value F1 of the fine-tuning frequency of each watch crystal under atmospheric pressure obtained based on the above calculation is uploaded to the server. The fine-tuning machine fine-tunes the target value F1 of each watch crystal resonator recorded on the server one by one by means of laser and galvanometer under the atmospheric pressure environment.

[0024] Furthermore, the whole-plate surface crystal resonator refers to a semi-finished product in which the chip has been fixed on the base but has not yet been packaged. It can be a semi-finished product obtained by processing a whole piece of undivided base plate, or it can be a single semi-finished product processed one by one, and then several single semi-finished products are fixed on the tooling to obtain a surface crystal resonator with the "tooling" as the "whole plate".

[0025] Furthermore, while fine-tuning with laser and galvanometer under atmospheric pressure, N 2 Blow the laser etching position to prevent heat concentration from causing cracks in the wafer; at the same time,2 An air suction device is added to the air duct to collect the etched material to avoid contaminating the chip and affecting the stability of the frequency test.

[0026] Furthermore, the fine adjustment amount ΔF1=F1-F2 under the atmospheric pressure environment is within 2000ppm, that is, the deviation of the coarse adjustment is controlled within 2000ppm of the target frequency. DETAILED DESCRIPTION

[0027] The following description is given in conjunction with examples, which are only used to explain the present invention and are not used to limit the scope of the present invention.

[0028] A method for fine-tuning a surface crystal comprises the following steps:

[0029] S1. Take the whole plate crystal resonator after rough adjustment, read the substrate ID of the whole plate crystal resonator, measure it in a vacuum environment, obtain the frequency of each crystal in a vacuum environment, referred to as the vacuum frequency after rough adjustment, represented by F3, and record the substrate ID, the position of the crystal on the whole plate and the respective vacuum frequency F3 after rough adjustment in the server. The whole plate crystal is processed based on the whole plate base, each whole plate base has a unique substrate ID, and the position of each crystal resonator on the whole plate base can be recorded, so the server can accurately record each crystal and its vacuum frequency after rough adjustment;

[0030] S2, placing the whole plate of crystal resonators into the fine-tuning machine, and using the measuring device in the fine-tuning machine to measure the whole plate of crystal resonators again under the atmospheric pressure environment, to obtain the frequency of each crystal under the atmospheric environment, referred to as the standard pressure frequency after coarse adjustment, represented by F2, and uploaded to the server for recording;

[0031] S3, based on the data recorded by the server, the difference between the vacuum frequency F3 after coarse adjustment and the standard voltage frequency F2 after coarse adjustment of each crystal resonator is compared one by one, and the difference between the vacuum frequency F3 after coarse adjustment and the standard voltage frequency F2 after coarse adjustment of each crystal resonator is obtained, which is referred to as the deviation frequency and is represented by ΔF2, that is, ΔF2=F3-F2; and written to the server;

[0032] Here, it is assumed that the measuring equipment used in the vacuum environment and the measuring equipment in the fine-tuning machine are both accurate. Because in steps S1 and S2, the entire crystal resonator being measured is the same and no other processing is performed after completing step S1, the difference between F3 measured in S1 and the value F2 measured in the fine-tuning machine is only caused by the difference in the corresponding crystal resonator working in a vacuum environment and an atmospheric environment.

[0033] S4, calculate the fine-tuning target value F1 of each crystal resonator, the expected precise frequency F0 of each crystal resonator in a vacuum environment after vacuum sealing is 32.768KHz, and the target value F1 of the fine-tuning frequency under atmospheric pressure is assumed, then the fine-tuning amount ΔF1 under atmospheric pressure is F1-F2;

[0034] Then: F1 = F0 - ΔF2

[0035] =F0-F3+F2;

[0036] S5. Based on the above calculation, the target value F1 of the fine-tuning frequency of each crystal on the whole plate under atmospheric pressure is obtained and uploaded to the server. The fine-tuning machine, under the atmospheric pressure environment, uses the target value F1 of each crystal resonator recorded on the server to perform fine-tuning one by one by means of laser and galvanometer. After completion, the whole plate of crystal resonators is obtained after fine-tuning.

[0037] Then the final product can be obtained by pressing, sealing, testing, etc.

[0038] Furthermore, the whole-plate surface crystal resonator refers to a chip that has been fixed on a base but has not yet been packaged. It can be a semi-finished product obtained by processing a whole piece of undivided base plate, or it can be a single semi-finished product processed one by one, and then several single semi-finished products are fixed on a tooling to obtain a semi-finished product with the "tooling" as the "whole plate".

[0039] Furthermore, while fine-tuning with laser and galvanometer under atmospheric pressure, N2 is continuously blown to the laser etching position to prevent heat concentration from causing cracks in the chip. At the same time, a negative pressure collection device is added to the N2 air duct to collect the etched material debris to avoid contaminating the chip and affecting the stability of the frequency test.

[0040] This solution is based on the whole-board processing technology of the crystal oscillator and the real-time recording and calculation of the server. It fully considers the large difference in the measurement values ​​of the crystal under atmospheric environment and vacuum environment, and accurately fine-tunes each crystal at a low cost. Ultimately, the operating frequency of the crystal obtained by processing has high consistency and low discreteness, thereby improving product quality.

[0041] For example, a whole board of crystals has a total of 168 individual crystal resonators. In the past, they were fine-tuned in the atmospheric environment to make the values ​​measured by all the crystal resonators in the atmospheric environment consistent, with a discreteness of 0ppm. After being sealed in a vacuum environment, the actual operating frequency was measured again, and the discreteness reached ±50ppm. The smaller the product, the greater the frequency discreteness after sealing.

[0042] When fine-tuning the whole plate crystal processed by this scheme in the atmospheric environment, the difference ΔF2 between the frequencies measured in the vacuum environment and in the atmospheric environment is considered one by one. After fine-tuning, the discreteness of the frequency measured in the atmospheric environment is ±50ppm, but after vacuum sealing, the discreteness of the actual working frequency is compressed to ±5ppm. The actual working frequency consistency we ultimately pursue is higher, so the products processed by this scheme have better frequency consistency during actual work.

[0043] The maximum fine-tuning amount ΔF1 in atmospheric pressure environment can reach 2000ppm. The maximum fine-tuning amount ΔF1 in atmospheric pressure environment can reach 2000ppm. However, according to actual experience, F0=62768HZ (deviation ±10ppm), F1=32757HZ (deviation about 15ppm), F2=32738HZ (deviation within about 300ppm), the difference ΔF2 between the frequencies measured in vacuum environment and atmospheric environment is around 300ppm.

[0044] For the same fine-tuning amount, if the ion etching method is used, the one-time fine-tuning amount can only reach within 500ppm, and multiple etchings are required or the coarse adjustment amount is controlled within 500ppm in advance. The processing efficiency is only about 50% of the laser and galvanometer methods, and the equipment cost is 3-4 times that of the laser and galvanometer equipment, so the processing cost is very high.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for fine-tuning a surface crystal, characterized in that: The following steps are involved: S1. Take the whole plate crystal resonator after rough adjustment, read the substrate ID of the whole plate crystal resonator, measure it in a vacuum environment, obtain the frequency of each crystal in a vacuum environment, referred to as the vacuum frequency after rough adjustment, represented by F3, and record the substrate ID, the position of the crystal on the whole plate and the respective vacuum frequency F3 after rough adjustment in the server. The whole plate crystal is processed based on the whole plate base, each whole plate base has a unique substrate ID, and the position of each crystal resonator on the whole plate base can be recorded, so the server can accurately record each crystal and its vacuum frequency after rough adjustment; S2, placing the whole plate of crystal resonators into the fine-tuning machine, and using the measuring device in the fine-tuning machine to measure the whole plate of crystal resonators again under the atmospheric pressure environment, to obtain the frequency of each crystal under the atmospheric environment, referred to as the standard pressure frequency after coarse adjustment, represented by F2, and uploaded to the server for recording; S3, based on the data recorded by the server, the difference between the vacuum frequency F3 after coarse adjustment and the standard voltage frequency F2 after coarse adjustment of each crystal resonator is compared one by one, and the difference between the vacuum frequency F3 after coarse adjustment and the standard voltage frequency F2 after coarse adjustment of each crystal resonator is obtained, which is referred to as the deviation frequency and is represented by ΔF2, that is, ΔF2=F3-F2; and written to the server; because S4, calculate the process ID fine-tuning target value F1, the expected precise frequency F0 of each crystal resonator in a vacuum environment after vacuum sealing is 32.768KHz, and the target value F1 of the fine-tuning frequency under atmospheric pressure, then: F1=F0-ΔF2 =F0-F3+F2; S5. The target value F1 of the fine-tuning frequency of each watch crystal under atmospheric pressure obtained based on the above calculation is uploaded to the server. The fine-tuning machine fine-tunes the target value F1 of each watch crystal resonator recorded on the server one by one by means of laser and galvanometer under the atmospheric pressure environment.

2. The method for fine-tuning a surface crystal according to claim 1, characterized in that: The whole-plate surface crystal resonator refers to a semi-finished crystal oscillator obtained by processing a whole, complete, undivided base plate.

3. The method for fine-tuning a surface crystal according to claim 1, characterized in that: The whole plate surface crystal resonator refers to the single surface crystal resonator that is processed one by one, and a number of single crystal oscillator semi-finished products are fixed on a tooling to obtain a crystal oscillator semi-finished product with the "tooling" as the "whole plate".

4. The method for fine-tuning a surface crystal according to any one of claims 1 to 3, characterized in that: While fine-tuning is performed with lasers and galvanometers under atmospheric pressure, N2 is blown to the laser etching position to prevent heat concentration from causing cracks in the chip.

5. The method for fine-tuning a surface crystal according to claim 4, characterized in that: An air suction device is provided on the N2 air duct, and the air suction device is used to recover the etched material.

6. The method for fine-tuning a surface crystal according to any one of claims 1 to 3, characterized in that: The coarse adjustment deviation is controlled within 2000ppm of the target frequency.