CN117353690B - Manufacturing method of low-ESR (equivalent series resistance) low-cost miniaturized tuning fork resonator - Google Patents
Manufacturing method of low-ESR (equivalent series resistance) low-cost miniaturized tuning fork resonator Download PDFInfo
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- CN117353690B CN117353690B CN202311396409.5A CN202311396409A CN117353690B CN 117353690 B CN117353690 B CN 117353690B CN 202311396409 A CN202311396409 A CN 202311396409A CN 117353690 B CN117353690 B CN 117353690B
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 30
- 238000003466 welding Methods 0.000 claims abstract description 114
- 238000007789 sealing Methods 0.000 claims abstract description 40
- 238000010438 heat treatment Methods 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 38
- 230000008569 process Effects 0.000 claims abstract description 28
- 239000011248 coating agent Substances 0.000 claims abstract description 13
- 238000000576 coating method Methods 0.000 claims abstract description 13
- 239000007789 gas Substances 0.000 claims description 56
- 238000007747 plating Methods 0.000 claims description 28
- 239000000853 adhesive Substances 0.000 claims description 24
- 230000001070 adhesive effect Effects 0.000 claims description 24
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 11
- 238000009954 braiding Methods 0.000 claims description 10
- 238000012360 testing method Methods 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 5
- 238000012216 screening Methods 0.000 claims description 4
- 230000002950 deficient Effects 0.000 claims description 3
- 238000009713 electroplating Methods 0.000 claims description 3
- 238000010329 laser etching Methods 0.000 claims description 3
- 238000010330 laser marking Methods 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 3
- 238000004806 packaging method and process Methods 0.000 claims description 3
- 238000000992 sputter etching Methods 0.000 claims description 3
- 229910001873 dinitrogen Inorganic materials 0.000 claims 1
- 230000032683 aging Effects 0.000 abstract description 10
- 238000001556 precipitation Methods 0.000 abstract description 8
- 239000000463 material Substances 0.000 abstract description 7
- 230000035882 stress Effects 0.000 abstract description 6
- 238000005476 soldering Methods 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 18
- 239000000047 product Substances 0.000 description 14
- 239000002274 desiccant Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 229910000679 solder Inorganic materials 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- 229910020630 Co Ni Inorganic materials 0.000 description 1
- 229910002440 Co–Ni Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/21—Crystal tuning forks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H2003/026—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the tuning fork type
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
The invention discloses a manufacturing method of a low ESR and low-cost miniaturized tuning fork resonator, which comprises the following steps: p1, preparing and assembling accessories; p2, heat treatment of an upper cover; p3, pre-welding an upper cover; p4, sealing and welding long edges; p5, vacuum heat treatment; and P6, sealing and welding the short sides. Compared with the prior art, the invention has the following advantages: the thickness of a coating (31) of the upper cover (3) is optimized, the P4 long-side sealing welding power is increased, the P5 vacuum heat treatment process is adjusted, the P6 short-side sealing welding power is reduced, the gas precipitation amount is restrained, the vacuum degree of the inner cavity (11) of the base is improved, and the ESR of the resonator is greatly reduced; the material cost is reduced by about 17%; the manufacturing process is simplified, the manufacturing period is shortened, and the manufacturing cost is further reduced; and after the P4 long-side sealing welding, carrying out P5 vacuum heat treatment to release the stress of the P4 long-side sealing welding, and improving the aging rate of the resonator and the frequency stability.
Description
Technical Field
The invention relates to the technical field of piezoelectric frequency components, in particular to a manufacturing method of a low-ESR (equivalent series resistance) low-cost miniaturized tuning fork resonator.
Background
The piezoelectric frequency component is an electronic device for generating a high-precision oscillation frequency signal by utilizing a piezoelectric effect, has the characteristics of stability and good anti-interference performance, and is widely applied to various electronic products. With miniaturization of tuning fork resonators, the volume of the inner cavity of the base for encapsulation is reduced, the sensitivity of the vacuum degree of the inner cavity of the base to the influence of equivalent resistance (ESR) is remarkably improved, and even if the vacuum degree is slightly reduced, the ESR is rapidly increased, namely the power consumption of the resonator is rapidly increased; the prior art manufacturing steps include (as shown in figure 2 of the specification): preparing and assembling accessories, heat treating an upper cover, pre-welding the upper cover, long-side sealing and welding, short-side sealing and welding, reflow welding, testing, marking and braiding, and firstly, performing a vacuum resetting test (shown in figure 4 of the specification) after uncovering a finished product of the manufacturing steps, wherein the ESR is reduced to a normal level after resetting, and the ESR is shown to be increased due to low vacuum degree of an inner cavity of a base; the factors that lead to a low vacuum in the preceding processing steps are then: (1) When the long edges are sealed and welded, the upper cover coating is heated and melted to generate gas, and part of the gas is wrapped by the welding layer; (2) When the short sides are sealed and welded, the upper cover coating is heated and melted to generate gas, wherein one part of gas is separated out and sealed in the inner cavity of the base, and the other part of gas is wrapped by the welding layer; (3) During reflow soldering, the gas wrapped by the fusion layer is heated to be further separated out to the inner cavity of the sealed base; (4) During reflow soldering, for example, the resonator contains a large amount of gas or moisture, and the gas can be separated out and the moisture can be vaporized under the action of high temperature of reflow soldering; the reflow process (shown in fig. 5 of the specification) must be performed in the final manufacturing step because: the customer mounts the resonator on the PCB substrate through reflow soldering, firstly, the solder paste between the electrode on the bottom surface of the resonator and the bonding pad of the PCB substrate is melted at high temperature, then the solder paste is cooled, and the resonator is soldered on the PCB substrate; if the resonator contains a large amount of gas or moisture, the vacuum degree of the inner cavity of the base can be reduced due to gas precipitation and moisture vaporization under the action of high temperature, so that ESR is increased, the resonance frequency is reduced, and finally, the use of a customer is influenced due to poor performance of the resonator; the purpose of the reflow process is to: simulating customer mounting conditions before testing, precipitating gas and vaporizing water contained in the resonator at high temperature, so that ESR and resonant frequency of the resonator are deteriorated due to the reduction of vacuum degree in the inner cavity of the base, and screening out the resonator through a testing procedure; the preparation process in the prior art has the following defects: although the resonator of the shipment can be ensured to some extent to be excellent by reflow soldering, the problem of the rise in ESR, that is, the rise in power consumption of the miniaturized tuning-fork resonator cannot be fundamentally solved.
In order to overcome the problems, the prior art adopts a method that a drying agent is coated at the bottom of an inner cavity of a base (as shown in figure 3 of the specification) during the preparation and assembly of a step accessory and the carrying of a tuning fork, and the drying agent absorbs gas and moisture in the inner cavity of the base after sealing welding, so that the vacuum degree is improved; however, the drying agent is a high-tech and high-value consumable material, which results in a significant increase in the material cost of the resonator.
Disclosure of Invention
In order to overcome the disadvantages and shortcomings of the prior art, an object of the present invention is to provide a method for manufacturing a miniaturized tuning fork resonator with low ESR and low cost.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method of manufacturing a low ESR, low cost miniaturized tuning fork resonator comprising the steps of:
P1, fitting preparation and assembly: the tuning fork is fixed in the inner cavity of the base through the conductive adhesive, an electrode of the tuning fork is conducted with an electrode sheet in the inner cavity of the base, and the frequency of the tuning fork is adjusted after the conductive adhesive is solidified;
P2, heat treatment of an upper cover: removing gas and water contained in the upper cover, and electroplating a plating layer on the surface of the upper cover for sealing and welding, wherein the thickness of the plating layer is 2.5+/-1.0 mu m;
p3, pre-welding an upper cover: pre-fixing the upper cover on the base ring through a resistance welding process;
p4, long-side seal welding: sealing and welding the long side of the upper cover and the long side of the base ring through a resistance welding process; the power of the long-side seal welding is increased to 360-380W, and the long-side seal welding is used for removing gas and moisture contained in the base, the tuning fork, the conductive adhesive and the upper cover;
P5, vacuum heat treatment: placing the product in a high-temperature and high-vacuum environment, and separating out the gas wrapped in the welding layer in the step P4 and removing the gas and water contained in the base, the conductive adhesive, the tuning fork and the upper cover;
P6, short edge seal welding: in a high vacuum state, the short side of the upper cover and the short side of the base ring are sealed and welded through a resistance welding process, and a high vacuum environment required by tuning fork vibration is formed in the inner cavity of the base; the power of short-side seal welding is reduced to 280-300W, so as to reduce the gas quantity generated when the coating is melted.
Preferably, steps P3 to P4 are all performed in a high purity nitrogen atmosphere.
Preferably, the maximum temperature in step P5 is 260-280℃and the maximum temperature holding time is 90-120 minutes.
Preferably, the nitrogen retention time in step P5 is 15 minutes to 30 minutes.
Preferably, in the step P5, the vacuum degree in the vacuum maintaining stage is 1×10 -3 Pa or less.
Preferably, in the step P3, the upper surface of the upper cover is pressed down by a pair of electrode rollers, and when the upper cover is electrified, the upper cover plating layer is melted and fused due to contact resistance, so that the upper cover can be pre-fixed.
Preferably, in the step P4, the upper surface of the upper cover is pressed down by a pair of electrode rollers, and the upper cover is rolled in the longitudinal direction when energized, and the upper cover plating layer is melted by contact resistance against heating, so that the long side of the upper cover and the long side of the base ring can be welded.
Preferably, in the step P6, the pair of electrode rollers are pressed down on the upper surface of the upper cover, roll in the short side direction when energized, and the upper cover plating layer is melted by contact resistance to heating, so that the short side of the upper cover and the short side of the base ring can be welded.
Preferably, the step P1 further includes:
p11, tuning fork break: breaking off and separating a single tuning fork from the wafer;
p12, tuning fork mounting: the tuning fork is fixed in the inner cavity of the base through conductive adhesive, and an electrode of the tuning fork is conducted with an electrode sheet of the inner cavity of the base;
P13, curing the conductive adhesive: placing the product carried by the tuning fork into a baking oven, and fully curing the conductive adhesive through high-temperature baking;
P14, fine tuning of frequency: tuning fork frequency is fine-tuned by laser or ion etching frequency modulator to make resonator frequency reach target.
Preferably, the method further comprises:
P7, test: measuring the frequency and other electrical properties of the resonator, and screening defective products except for the standard;
P8, marking: marking identification information on the surface of the resonator by a laser marking machine;
p9, braiding: and braiding and packaging the resonators by a braiding machine.
The invention has the beneficial effects that:
(1) By optimizing the thickness of the upper cover coating, on one hand, the gas quantity of the coating precipitated due to the heated and melted coating in the step P6 short-side seal welding can be reduced, and on the other hand, the gas quantity wrapped in the welding layer during the P4 long-side seal welding and the P6 short-side seal welding can be reduced, and the gas precipitation in the step reflow welding can be further reduced;
(2) The power of the P4 long-side seal welding is improved, the instant temperature is improved during seal welding, and the gas and the moisture contained in the base, the tuning fork, the conductive adhesive and the upper cover are removed by utilizing high temperature;
(3) Reducing the vacuum heat treatment twice to one time, and adjusting the vacuum heat treatment in the step P5 to the P4 long-side seal welding, so that the gas wrapped in the welding layer can be separated out in advance during the P4 long-side seal welding, and the gas separation quantity of the P6 short-side seal welding and reflow welding is reduced;
(4) The power of P6 short-side seal welding is reduced, namely the temperature of the short-side seal welding is reduced, the melting of the upper cover coating can be reduced, and then the gas precipitation amount during P6 short-side seal welding and reflow soldering is reduced.
Compared with the prior art, the invention has the following advantages:
(1) The thickness of the upper cover plating layer is optimized, the P4 long-side sealing welding power is increased, the P5 vacuum heat treatment working sequence is adjusted, the P6 short-side sealing welding power is reduced, the gas precipitation amount is restrained, the vacuum degree of the inner cavity of the base is improved, and the ESR of the resonator is greatly reduced;
(2) On the premise of not using a drying agent and not increasing a manufacturing process, a low ESR packaging process of the miniaturized tuning fork resonator is realized, and compared with the process of comparative example 2, the ESR average value after P6 short-side sealing welding or reflow welding is at the same level, but the material cost is reduced by about 17% due to the fact that the drying agent is not used;
(3) Under the condition that the first heat treatment is not implemented, the ESR after short-side seal welding and reflow soldering has no obvious change, and the first heat treatment can be omitted; on the premise of ensuring the yield and the quality, the reflow soldering is changed into an unnecessary process, the manufacturing process is simplified, the manufacturing period is shortened, and the manufacturing cost is further reduced;
(4) After the P4 long-side sealing welding, P5 vacuum heat treatment is implemented, so that the stress of the P4 long-side sealing welding is released, the variation of resonant frequency before and after 125 ℃ and 72H aging is reduced, the aging rate of the resonator is improved, and the frequency stability is improved.
Drawings
FIG. 1 is a process flow diagram of an embodiment of the present invention;
FIG. 2 is a process flow diagram of comparative example 1 in the prior art;
FIG. 3 is a process flow diagram of comparative example 2 of the prior art;
FIG. 4 is a comparison of ESR before and after the completion of the vacuum recovery test of the comparative example 1;
FIG. 5 is a graph showing a comparison of the average ESR values before and after reflow soldering for each process;
FIG. 6 is a schematic illustration of resistance welding;
FIG. 7 is a comparison of the average ESR before and after reflow of the long side seal welding power VS before the vacuum heat treatment process is changed;
FIG. 8 is a comparison of the average ESR values of the long side sealing power VS and the short side sealing power before and after the vacuum heat treatment process is changed;
FIG. 9 is a comparison of the average ESR values after reflow soldering of the long side sealing power VS before and after the change of the vacuum heat treatment process;
FIG. 10 shows the average ESR values before and after the long-side sealing and reflow soldering at a power of 280W in each of the present example and comparative example 1;
FIG. 11 is the average ESR before and after reflow of the short side seal power VS;
FIG. 12 shows the variation of the short side sealing power VS solder reflow ESR;
FIG. 13 is a comparison of the aging rate of the present example and that of comparative example 2;
fig. 14 is a cross-sectional view of a product of an embodiment of the present invention.
The figure shows:
1-base, 11-base cavity, 12-base ring;
2-tuning fork;
3-upper cover, 31-coating;
4-conductive adhesive;
5-power supply;
6-electrode roller.
Detailed Description
Embodiments of the present invention will now be described in detail with reference to the drawings, which are intended to be used as references and illustrations only, and are not intended to limit the scope of the invention.
Referring to fig. 1 and 14, in the present embodiment, a method for manufacturing a miniaturized tuning fork 2-type resonator with low ESR and low cost includes the steps of:
P1, fitting preparation and assembly: fixing the tuning fork 2 (namely the vibrating piece) in the inner cavity 11 of the base through the conductive adhesive 4, conducting the electrode of the tuning fork 2 with the electrode sheet of the inner cavity 11 of the base, and adjusting the frequency of the tuning fork 2 after curing the conductive adhesive 4;
p2, heat treatment of an upper cover: removing gas and water contained in the upper cover 3, and electroplating a plating layer 31 on the surface of the upper cover 3 for sealing and welding, wherein the thickness of the plating layer 31 is 2.5+/-1.0 mu m;
p3, pre-welding an upper cover: pre-fixing the upper cover 3 on the base ring 12 through a resistance welding process;
P4, long-side seal welding: the long side of the upper cover 3 and the long side of the base ring 12 are sealed and welded through a resistance welding process; the power of the long-side seal welding is increased to 360-380W, and the long-side seal welding is used for removing gas and moisture contained in the base 1, the tuning fork 2, the upper cover 3 and the conductive adhesive 4;
P5, vacuum heat treatment: the product is placed in a high-temperature and high-vacuum environment and is used for separating out the gas wrapped in the welding layer in the step P4 and removing the gas and the water contained in the base 1, the tuning fork 2, the upper cover 3 and the conductive adhesive 4;
p6, short edge seal welding: in a high vacuum state, the short side of the upper cover 3 and the short side of the base ring 12 are sealed and welded through a resistance welding process, and the inner cavity 11 of the base forms a high vacuum environment required by vibration of the tuning fork 2; the power of the short-side seal welding is reduced to 280-300W for reducing the amount of gas generated when the plating layer 31 melts.
The invention will now be described by way of example with a 3215-sized tuning fork resonator, it being noted that the process of this embodiment eliminates reflow soldering, and the parameters relating to reflow soldering below are used only for comparative illustration;
The upper cover 3 of this embodiment is made of Fe-Co-Ni alloy base material and electrolytic nickel plating layer 31, the nickel plating layer 31 melts to generate gas during P4 long side seal welding and P6 short side seal welding, and the gas is wrapped in the welding layer, and 5 groups of upper covers 3 are compared with different thickness groups of the plating layer 31
Table 1:
As can be seen from table 1, the thickness of the plating layer 31 has a significant effect on the average ESR after P6 short-side seal welding and after reflow welding, and the thicker the thickness of the plating layer 31 is, the larger the average ESR after P6 short-side seal welding and after reflow welding is; according to the embodiment, the ESR of the resonator is reduced by optimizing the thickness of the coating 31, so that on one hand, the gas quantity generated by heating and melting of the coating 31 during P6 short-side seal welding can be effectively restrained, and therefore the vacuum degree of the base cavity 11 after the P6 short-side seal welding is improved, the average value of the ESR after the P6 short-side seal welding is improved, and on the other hand, the gas quantity wrapped in the welding layer during P4 long-side seal welding and P6 short-side seal welding can be effectively reduced, and therefore the gas precipitation quantity during reflow welding is reduced, the vacuum degree of the base cavity 11 after the reflow welding is maintained, and the ESR after the reflow welding is maintained. However, in order to avoid the leakage of air due to insufficient melting due to the excessively thin thickness of the plating layer 31, the thickness of the plating layer 31 of the preferred embodiment is 2.5 μm, which is reduced by about 4.0kΩ in mean ESR after reflow soldering, compared with the thickness of the plating layer 31 before optimization of 4 μm, in consideration of the tolerance of the thickness of the plating layer 31.
Referring to fig. 6, resistance welding is to generate heat by using the principle of joule's law to melt a material. Joule's law: q=i 2 Rt, "Q" is heat, "I" is current, "R" contacts resistance, "t" is time, in a pure resistive circuit, P (power) =i 2 R, i.e., q=pt, so the temperature of the resistance welding is mainly determined by the power of the seal welding, and the higher the power, the higher the temperature; considering that the gas and moisture contained in the base 1, the tuning fork 2, the upper cover 3 and the conductive adhesive 4 are difficult to remove by baking at a limited high temperature (up to 300 ℃) and overlapping the effect of high vacuum (boiling point reduction) in vacuum heat treatment, the sealing power is increased, and the heating temperature of a product during sealing is a means for removing the gas and the moisture; as shown in fig. 7, when the P4 long side sealing power is 280W to 340W, the ESR average value after P6 short side sealing and after reflow soldering tends to decrease as the power increases, but as the power further increases, the ESR average value after P6 short side sealing and after reflow soldering tends to increase, particularly the ESR average value after reflow soldering increases sharply, and although the high temperature can precipitate and volatilize the gas contained in the base 1, tuning fork 2, upper cover 3, conductive paste 4, the higher the sealing temperature, the more the gas generated when the plating layer 31 melts and the gas wrapped in the welding layer, and when the power is proper, the a (removed gas, moisture) > B (generated gas), and the ESR average value decreases; when the power is too high, a (removed gas, moisture) < B (generated gas), ESR average increases; in the embodiment, after the P5 vacuum heat treatment is adjusted to the P4 long-side seal welding, the generated gas can be separated out during the P5 vacuum heat treatment, so that the gas separation amount during the P6 short-side seal welding and reflow welding is reduced, and the ESR average value after the P6 short-side seal welding (shown in fig. 8) and after the reflow welding (shown in fig. 9) can be effectively reduced; as shown in fig. 10, the same effect as that of fig. 8 and 9 cannot be obtained even by performing the P5 vacuum heat treatment after the P4 long side seal welding without increasing the P4 long side seal welding power, so the effect of low ESR can be achieved by having to adjust the working order of the vacuum heat treatment while increasing the long side seal welding power; referring to fig. 8 and 9, when the P4 long side sealing power reaches 400W, the ESR average value after reflow soldering tends to increase, which means that the gas wrapped in the welding layer is too much, and reaches the upper limit of the processing capacity of the P5 vacuum heat treatment, based on the above result, the P4 long side sealing power in this embodiment is optimized from 280W to 370W, and by increasing the P4 long side sealing power and adjusting the working procedure of the P5 vacuum heat treatment, the ESR average value after reflow soldering is reduced by about 8kΩ.
Referring to fig. 11 and 12, in the P6 short side sealing of the present embodiment, the reduced power can effectively reduce the mean ESR after short side sealing, and the ESR variation of reflow soldering also has a decreasing trend, which means that after the sealing power is reduced, the sealing temperature is reduced, the melting of the plating layer 31 is reduced, and the amount of gas generated is also reduced, so as to avoid the leakage caused by insufficient melting due to the excessively low sealing power, the sealing power of the present embodiment is optimized from 320W to 290W, and the ESR after reflow soldering is reduced by about 4kΩ.
Preferably, steps P3 to P4 are all performed in a high purity nitrogen atmosphere. In order to avoid water adsorption of the product, steps P3 to P4 are performed in high purity nitrogen with dew point temperature control specification: the lower the dew point temperature is at minus 40 ℃, the lower the moisture content of the nitrogen.
Preferably, the maximum temperature in step P5 is 260-280℃and the maximum temperature holding time is 90-120 minutes.
In this example, the maximum temperature in step P5 was 270℃and the maximum temperature holding time was 100 minutes.
Preferably, the nitrogen retention time in step P5 is 15 minutes to 30 minutes.
In this example, the nitrogen hold time in step P5 was 20 minutes.
Preferably, in the step P5, the vacuum degree in the vacuum maintaining stage is 1×10 -3 Pa or less.
Preferably, in the step P3, the upper surface of the upper cover 3 is pressed down by the pair of electrode rollers 6, and the upper cover 3 is pre-fixed at a position where the plating layer 31 of the upper cover 3 is melted and melted due to contact resistance when the upper cover is energized.
Preferably, in the step P4, the pair of electrode rollers 6 is pressed down to act on the upper surface of the upper cover 3, and the upper cover 3 is rolled in the longitudinal direction when energized, and the plating layer 31 of the upper cover 3 is melted by contact resistance to heating, so that the long side of the upper cover 3 and the long side of the base ring 12 can be welded.
Preferably, in the step P6, the pair of electrode rollers 6 is pressed down on the upper surface of the upper cover 3, rolls in the short side direction when energized, and the plating layer 31 of the upper cover 3 is melted by contact resistance to heating, so that the short side of the upper cover 3 and the short side of the base ring 12 can be welded.
Preferably, the step P1 further includes:
p11, tuning fork break: breaking off and separating a single tuning fork 2 from the wafer;
P12, tuning fork mounting: fixing the tuning fork 2 to the inner cavity 11 of the base through the conductive adhesive 4, and conducting the electrode of the tuning fork 2 with the electrode sheet of the inner cavity 11 of the base;
p13, curing the conductive adhesive: placing the product with the tuning fork carried in a baking oven, and fully curing the conductive adhesive 4 through high-temperature baking;
p14, fine tuning of frequency: tuning fork 2 frequency is fine tuned by laser or ion etching frequency modulator to achieve the resonator frequency target.
Preferably, the method further comprises:
p7, test: measuring the frequency and other electrical properties of the resonator, and screening defective products except for the standard;
P8, marking: marking identification information on the surface of the resonator by a laser marking machine;
p9, braiding: and braiding and packaging the resonators by a braiding machine.
This embodiment has the following advantages over comparative examples 1 to 2:
the thickness of the coating 31 of the upper cover 3 is optimized, the P5 vacuum heat treatment process is adjusted, the power of P6 short side seal welding is reduced, the gas precipitation amount is restrained, and the vacuum degree of the inner cavity 11 of the base is improved;
table 2 below is a table of the ESR alignment before and after each process reflow:
Compared with comparative example 1, the average value of ESR after P6 short-side seal welding is reduced by about 7KΩ, the variation of the average value of ESR after reflow welding is reduced by about 9KΩ, the total variation of the average value of ESR after reflow welding is reduced by about 16KΩ, the gas precipitation amount in the related process is inhibited, and the vacuum degree of the inner cavity 11 of the base is improved;
in this example, compared with comparative example 2, the ESR average value after P6 short side sealing or after reflow soldering is at the same level, but the material cost is reduced by about 17% because no drying agent is used;
in this embodiment, the amount of change in ESR during reflow is reduced, and no defect occurs during customer mounting even if no reflow is performed, so that reflow is canceled in the process of this embodiment.
Comparative example 1 and comparative example 2 differ only in the use of a desiccant, and the number of steps and the process sequence are the same, and the comparative data of comparative example 1 and comparative example 2 are described below;
table 3 below shows the mean ESR value comparison of this example with comparative example 1 without the first vacuum heat treatment:
in the embodiment, after short-side seal welding and reflow welding, the ESR is not obviously changed, so that the change amount of the ESR is controlled, the first heat treatment is canceled in the process of the embodiment, the manufacturing process is simplified, the manufacturing period is shortened, and the manufacturing cost is further reduced;
In comparative example 1, after the first heat treatment is canceled, the ESR after short-side seal welding and reflow welding is increased, and in particular, the ESR after reflow welding is increased by about 7kΩ compared with that before cancellation; the first heat treatment must be performed without taking other measures to remove the gas and moisture contained in the product.
The frequency of the resonator shifts with time, a necessary phenomenon, called aging, the main cause of which is: mass migration and stress relaxation; the aging rate is an index for evaluating the degree of frequency offset, and represents the frequency offset of the resonator in years at normal temperature, and the smaller the aging rate is, the higher the stability and reliability of the resonator are, and the aging rate can be verified by an acceleration test at 125 ℃ x 72 hours (equivalent to 1 year at normal temperature), please refer to fig. 13 and table 4 below:
| No. | This embodiment | Comparative example 2 |
| 1 | 1.0 | 4.2 |
| 2 | 1.7 | 3.2 |
| 3 | 1.4 | 4.0 |
| 4 | 0.7 | 5.6 |
| 5 | 1.2 | 3.8 |
| 6 | 1.2 | 3.6 |
| 7 | 1.3 | 2.9 |
| 8 | 0.5 | 2.2 |
| 9 | 1.1 | 2.9 |
| 10 | 1.1 | 1.7 |
| 11 | 1.3 | 3.3 |
| 12 | 1.4 | 2.2 |
| 13 | 1.0 | 2.4 |
| 14 | 1.6 | 2.7 |
| 15 | 0.2 | 4.8 |
| 16 | 1.1 | 1.4 |
| 17 | 1.9 | 3.5 |
| 18 | 1.1 | 1.5 |
| 19 | 1.7 | 2.0 |
| 20 | 0.9 | 2.7 |
| Maximum value | 1.9 | 5.6 |
| Minimum value | 0.2 | 1.4 |
| Average value of | 1.2 | 3.0 |
After the P4 long-side seal welding, the P5 vacuum heat treatment is carried out, so that the stress of the P4 long-side seal welding is released, the total stress level after the seal welding in the embodiment is lower than that of the comparison example 2, the stress release of the product is reduced when the product is subjected to an ageing test for 72 hours at 125 ℃, the variation of the resonant frequency is reduced, namely the ageing rate of the resonator is improved, and the frequency stability is improved.
The above disclosure is illustrative of the preferred embodiments of the present invention and should not be construed as limiting the scope of the invention, which is defined by the appended claims.
Claims (10)
1. A method for manufacturing a miniaturized tuning fork resonator having a low ESR and a low cost, comprising the steps of:
P1, fitting preparation and assembly: the tuning fork is fixed in the inner cavity of the base through the conductive adhesive, an electrode of the tuning fork is conducted with an electrode sheet in the inner cavity of the base, and the frequency of the tuning fork is adjusted after the conductive adhesive is solidified;
P2, heat treatment of an upper cover: removing gas and water contained in the upper cover, and electroplating a plating layer on the surface of the upper cover for sealing and welding, wherein the thickness of the plating layer is 2.5+/-1.0 mu m;
p3, pre-welding an upper cover: pre-fixing the upper cover on the base ring through a resistance welding process;
p4, long-side seal welding: sealing and welding the long side of the upper cover and the long side of the base ring through a resistance welding process; the power of the long-side seal welding is increased to 360-380W, and the long-side seal welding is used for removing gas and moisture contained in the base, the tuning fork, the conductive adhesive and the upper cover;
P5, vacuum heat treatment: placing the product in a high-temperature and high-vacuum environment, and separating out the gas wrapped in the welding layer in the step P4 and removing the gas and water contained in the base, the conductive adhesive, the tuning fork and the upper cover;
P6, short edge seal welding: in a high vacuum state, the short side of the upper cover and the short side of the base ring are sealed and welded through a resistance welding process, and a high vacuum environment required by tuning fork vibration is formed in the inner cavity of the base; the power of short-side seal welding is reduced to 280-300W, so as to reduce the gas quantity generated when the coating is melted.
2. The method for manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 1, wherein steps P3 to P4 are performed in a high purity nitrogen atmosphere.
3. The method of manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 2, wherein the nitrogen gas holding time in step P5 is 15 minutes to 30 minutes.
4. The method of manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 1, wherein the maximum temperature in step P5 is 260 ℃ to 280 ℃ and the maximum temperature holding time is 90 minutes to 120 minutes.
5. The method of manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 4, wherein the vacuum degree in the vacuum maintaining step in step P5 is 1 x 10 -3 Pa or less.
6. The method of manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 2, wherein in the step P3, the upper surface of the upper cover is pressed down by a pair of electrode rollers, and the upper cover plating is melted and melted by contact resistance during energization, so that the upper cover can be pre-fixed.
7. The method of manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 2, wherein in the step P4, the upper surface of the upper cover is pressed down by a pair of electrode rollers, and the upper cover is rolled in the long side direction when energized, and the upper cover plating layer is melted by contact resistance to be heated, and the long side of the upper cover and the long side of the base ring can be welded.
8. The method of manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 2, wherein in the step P6, the pair of electrode rollers are pressed down on the upper surface of the upper cover, roll in the short side direction when energized, and the upper cover plating layer is melted by contact resistance to be heated, and the melting point can weld the short side of the upper cover and the short side of the base ring.
9. The method for manufacturing a miniaturized tuning fork resonator with low ESR and low cost according to claim 1, wherein said step P1 further comprises:
p11, tuning fork break: breaking off and separating a single tuning fork from the wafer;
p12, tuning fork mounting: the tuning fork is fixed in the inner cavity of the base through conductive adhesive, and an electrode of the tuning fork is conducted with an electrode sheet of the inner cavity of the base;
P13, curing the conductive adhesive: placing the product carried by the tuning fork into a baking oven, and fully curing the conductive adhesive through high-temperature baking;
P14, fine tuning of frequency: tuning fork frequency is fine-tuned by laser or ion etching frequency modulator to make resonator frequency reach target.
10. The method for manufacturing a low ESR, low cost miniaturized tuning fork resonator of claim 1, further comprising:
P7, test: measuring the frequency and other electrical properties of the resonator, and screening defective products except for the standard;
P8, marking: marking identification information on the surface of the resonator by a laser marking machine;
p9, braiding: and braiding and packaging the resonators by a braiding machine.
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