Micro-miniaturization design method for high-precision temperature-compensated crystal oscillator

Abstract

The invention discloses a microminiaturization design method of a high-precision temperature compensation crystal oscillator, which belongs to the technical field of temperature compensation crystal oscillator design and comprises the microminiaturization design of a multilayer surface-mounted ceramic base, the design of a metal cover plate, the microminiaturization design of a quartz oscillator and the microminiaturization design of an integrated circuit temperature compensation chip. The miniaturization design of the multilayer surface-mounted ceramic base comprises SMD3225 type packaging, the design of the metal cover plate comprises integrated packaging with the multilayer surface-mounted ceramic base, and the miniaturization design of the quartz vibrator comprises the selection of AT cut type and high-Q-value small rectangular quartz wafers. According to the design method, the mainstream packaging size of the temperature compensation crystal oscillator is successfully reduced from SMD5032 to SMD3225 by adopting the innovative multilayer surface-mounted ceramic base, the ultra-small-size quartz oscillator and the miniaturized temperature compensation chip, and the urgent requirements of modern electronic equipment for light weight and miniaturization of a core frequency source are met. And meanwhile, the metal cover plate and the ceramic base are welded and sealed in parallel through resistors, so that the leakage rate of the device is remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of temperature-compensated crystal oscillator design technology, and particularly relates to a miniaturized design method for a high-precision temperature-compensated crystal oscillator. Background Technology

[0002] Due to their good frequency stability and high reliability, crystal oscillators have become key components for time and frequency references and frequency control in electronic systems. As the performance of electronic devices gradually improves, higher requirements are being placed on the performance indicators of crystal oscillators.

[0003] Crystal oscillators are broadly classified into several categories, including oven-controlled crystal oscillators (OCCs), temperature-compensated crystal oscillators (TCCs), and conventional crystal oscillators. Among these, TCCs not only possess advantages over oven-controlled crystal oscillators, such as miniaturization, low power consumption, and low cost, but also offer superior accuracy, stability, and low aging rate compared to conventional crystal oscillators. This makes them the preferred choice for high-precision frequency sources in electronic devices, meeting the demands for accurate and stable signal transmission. Research on miniaturization and high reliability of TCCs is a crucial direction for the technological iteration of TCCs.

[0004] Currently, the smallest temperature-compensated crystal oscillator commonly used in systems is the surface-mount SMD5032 package. In order to achieve the goals of lightweighting and miniaturization, the size and weight of the internal frequency source need to be further reduced while maintaining high precision and high reliability.

[0005] This invention designs a surface-mount SMD3225 packaged micro-miniature high-precision surface-mount temperature-compensated crystal oscillator with dimensions of 3.2mm × 2.5mm × 1.1mm, a frequency range of 10MHz to 50MHz, frequency temperature stability of better than ±1ppm at -40℃ to +85℃, and phase noise better than -130dBc / Hz@1kHz.

[0006] It should be noted that the above content falls within the inventor's technical knowledge and does not necessarily constitute prior art. Summary of the Invention

[0007] To address the aforementioned issues, the present invention aims to provide a miniaturized design method for high-precision temperature-compensated crystal oscillators. By employing an innovative multi-layer surface-mount ceramic substrate, an ultra-small quartz oscillator, and a miniaturized temperature-compensated chip, the mainstream package size of temperature-compensated crystal oscillators has been successfully reduced from SMD5032 to SMD3225, significantly reducing volume and meeting the urgent needs of modern electronic devices for lightweight and miniaturized core frequency sources. Simultaneously, the metal cover and ceramic substrate are sealed using parallel resistor soldering, significantly reducing device leakage and enhancing sealing performance and long-term environmental reliability.

[0008] To achieve the above objectives, this invention proposes a miniaturized design method for a high-precision temperature-compensated crystal oscillator. The design method includes: miniaturization design of a multilayer surface-mount ceramic substrate, design of a metal cover plate, miniaturization design of a quartz oscillator, and miniaturization design of an integrated circuit temperature-compensated chip.

[0009] The miniaturized design of the multilayer surface-mount ceramic substrate includes an SMD3225 package.

[0010] The design of the metal cover plate includes an integrated encapsulation between it and the multilayer surface-mount ceramic base.

[0011] The miniaturization design of the quartz oscillator includes the use of a small rectangular quartz wafer with an AT cut and a high Q value.

[0012] The miniaturization design of the integrated circuit temperature compensation chip includes its construction using a CMOS LSI structure.

[0013] Preferably, the miniaturized design of the multilayer surface-mount ceramic substrate further includes:

[0014] The multilayer surface-mount ceramic base is designed with 5 layers. The back of the 5th layer has 4 gold-plated leads, which are the functional leads of the high-precision temperature-compensated crystal oscillator.

[0015] The four gold-plated leads are for power, ground, output, and debugging. The third and fourth layers of the multilayer surface-mount ceramic base introduce the gold-plated leads into its chamber through vertical and wired connections. The second layer contains at least two gold-plated platforms for bonding the quartz oscillator.

[0016] The gold-plated platform is connected to the wiring of the third and fourth layers and the gold-plated lead-out of the fifth layer of the multilayer surface-mount ceramic substrate through a vertical connection. The first layer of the multilayer surface-mount ceramic substrate is a sealing ring.

[0017] Preferably, the metal cap design also includes:

[0018] The metal cover is designed to be (0.9mm±0.2mm)×(0.8mm±0.2mm) in size, which matches the size of the sealing ring on the multilayer surface-mount ceramic base. The metal cover and the multilayer surface-mount ceramic base are integrated into a single package through resistance parallel soldering.

[0019] Preferably, the miniaturization design of the quartz oscillator further includes:

[0020] The dimensions of the quartz oscillator are designed as length × width = (2mm ± 0.1mm) × (1.3mm ± 0.1mm), and the chamfer is designed according to the frequency of the quartz crystal.

[0021] The metal electrodes on the quartz oscillator are rectangular electrodes concentric with the quartz crystal, with dimensions of 0.79mm × 0.59mm, line width of 60μm, and pad size of 70μm × 70μm.

[0022] The metal electrode is made of gold, and its substrate material is chromium.

[0023] The two ends of the quartz oscillator extending from the wide edge are respectively bonded to the gold-plated platform of the multilayer surface-mount ceramic base with conductive adhesive.

[0024] Preferably, the miniaturization design of the integrated circuit temperature compensation chip further includes:

[0025] The integrated circuit temperature compensation chip integrates a temperature sensor, a 5th-order voltage function generator, an automatic frequency control circuit, a VCXO circuit, and an erasable and rewritable non-volatile memory.

[0026] Preferably, the quartz oscillator is oscillated by providing the negative impedance of the integrated circuit temperature compensation chip through a voltage control circuit;

[0027] The AFC circuit provides an external voltage to the integrated circuit temperature compensation chip to fine-tune and correct the resonant frequency of the quartz oscillator.

[0028] The inherent temperature deviation of the quartz oscillator is compensated by a temperature compensation circuit.

[0029] The temperature compensation coefficient of the temperature compensation circuit is adjusted by using an erasable and rewritable non-volatile memory to adapt to the discreteness between different quartz oscillators.

[0030] Preferably, the temperature compensation circuit integrates a bandgap reference circuit, an adder, and first-order, third-order, fourth-order, and fifth-order voltage function generators.

[0031] Preferably, the bandgap reference circuit performs vertical shifting and adjustment on the first-order temperature voltage of the fifth-order voltage function generator.

[0032] The adder amplifies and reduces the fourth and fifth order temperature voltages of the fifth-order voltage function generator.

[0033] The integrated circuit temperature compensation chip 4 senses the ambient temperature through a temperature sensor. The 5th-order voltage function generator generates the 1st and 3rd to 5th order temperature voltages from the ambient temperature and applies them to the voltage control terminal of the temperature compensation varactor diode. This causes the integrated circuit temperature compensation chip to generate a compensation frequency curve that is opposite to the frequency change of the quartz oscillator with temperature, thereby compensating for the frequency drift of the AT-cut quartz oscillator.

[0034] The miniaturization design method for a high-precision temperature-compensated crystal oscillator proposed in this invention can bring the following beneficial effects:

[0035] 1. This invention utilizes an innovative multi-layer surface-mount ceramic substrate, an ultra-small quartz oscillator (2mm × 1.3mm), and a miniaturized temperature-compensated (TCC) chip (0.79mm × 0.59mm) to successfully reduce the mainstream package size of TCC crystal oscillators from SMD5032 to SMD3225, significantly reducing volume and meeting the urgent needs of modern electronic devices for lightweight and miniaturized core frequency sources. Simultaneously, the metal cover and ceramic substrate are sealed using parallel resistor soldering, significantly reducing device leakage and enhancing sealing performance and long-term environmental reliability.

[0036] 2. The design method of this invention precisely designs the AT chamfer for quartz oscillators of different frequencies (e.g., 20MHz, 50MHz) and combines it with a dedicated CMOS temperature-compensated chip integrating a 5th-order voltage function generator, a high-precision temperature sensor, and memory for fine compensation. This results in frequency temperature stability better than ±0.3ppm over a wide temperature range of -40℃ to +85℃, and phase noise better than -130dBc / Hz at a 1kHz frequency deviation. These performance indicators reach the level of high-end temperature-compensated crystal oscillators and are far superior to conventional temperature-compensated crystal oscillators.

[0037] 3. The quartz oscillator designed in this invention employs a high Q-value design and gold electrodes, ensuring excellent resonance characteristics and chemical stability. The non-volatile memory built into the integrated circuit temperature-compensated chip allows for adjustment of the compensation coefficient for the discreteness of each quartz oscillator, effectively improving the consistency of batch products. The simple internal wiring and functional area isolation design reduce crosstalk, further ensuring the purity and stability of electrical performance.

[0038] 4. The multilayer surface-mount ceramic substrate in this invention features a rationally designed internal structure that satisfies the requirements of short chip bonding lines and reliable connections, while also achieving stable bonding and electrical connection of the quartz oscillator through a gold-plated platform. The entire solution is highly modular, with a clearly defined manufacturing process, laying the foundation for large-scale, highly consistent production. Its small size and superior performance enable it to be widely used in fields with stringent requirements for space and frequency performance, such as 5G communication, satellite navigation, precision instruments, and portable medical devices. Attached Figure Description

[0039] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0040] Figure 1 This is a frontal cross-sectional view of the high-precision temperature-compensated crystal oscillator of the present invention.

[0041] Figure 2 This is a schematic diagram of the installation position of the quartz oscillator of the present invention.

[0042] Figure 3 This is a schematic diagram showing the installation position of the integrated circuit temperature compensation chip of the present invention.

[0043] Figure 4 This is a typical frequency temperature variation curve of the quartz oscillator of the present invention.

[0044] Figure 5 This is a schematic diagram of the port layout of the integrated circuit temperature compensation chip of the present invention. Detailed Implementation

[0045] To more clearly illustrate the overall concept of the present invention, a detailed description will be provided below with reference to the accompanying drawings and examples.

[0046] Embodiments of the present invention propose a miniaturized design method for a high-precision temperature-compensated crystal oscillator, such as... Figure 1 As shown, the high-precision temperature-compensated crystal oscillator includes a multi-layer surface-mount ceramic substrate 1 with an SMD3225 package, a metal cover plate 2, a miniature high-stability quartz oscillator 3, conductive adhesive for bonding, and a miniature integrated circuit temperature compensation chip 4.

[0047] Design methods include:

[0048] I. Miniaturization design of the multilayer surface-mount ceramic substrate 1, specifically:

[0049] The multilayer surface-mount ceramic substrate 1 is designed as a 5-layer surface-mount ceramic substrate. The main material is 92% black alumina ceramic, and the bottom pad is plated with nickel and gold. The internal wiring is simple and the layout is reasonable. The distance between each functional area is large to reduce crosstalk, which meets the requirements of simple chip gold wire bonding and the shortest possible wire bonding.

[0050] The fifth layer (the bottom layer of the multilayer surface-mount ceramic substrate 1) has four gold-plated leads on its back, which are the functional leads of the high-precision temperature-compensated crystal oscillator. The four gold-plated leads are for power, ground, output, and debugging, respectively. The third and fourth layers introduce the gold-plated leads into the cavity of the multilayer surface-mount ceramic substrate 1 through vertical and wiring connections. The second layer contains at least two gold-plated platforms for bonding the quartz oscillator 3. The gold-plated platforms are connected to the wiring of the third and fourth layers and the gold-plated leads of the fifth layer through vertical connections. The first layer is a sealing ring to realize the electrical connection function.

[0051] II. Design of metal cover plate 2;

[0052] The metal cover plate 2 has dimensions of (2.85mm±0.2mm)×(2.15mm±0.2mm), which matches the size of the top sealing ring of the multilayer surface-mount ceramic base 1. The metal cover plate and the multilayer surface-mount ceramic base 1 are integrated and sealed by resistance parallel welding to reduce the leakage rate. The surface of the metal cover plate 2 can be used as a marking surface.

[0053] III. Miniaturization design of quartz oscillator 3;

[0054] The quartz oscillator 3 is a small rectangular quartz wafer with AT cut (a type of quartz wafer cutting angle) and high Q (quality factor) value, and its size is designed as length × width = (2mm ± 0.1mm) × (1.3mm ± 0.1mm).

[0055] To meet the requirement of better than ±30ppm temperature compensation for frequency temperature stability within the operating temperature range of -40℃ to +85℃, the chamfer angle needs to be precisely designed according to the frequency of the quartz crystal. For example, the chamfer angles of 20MHz and 50MHz quartz crystals are designed to be 35°11.5ˊ±1ˊ and 35°16ˊ±1ˊ, respectively.

[0056] The metal electrode is a rectangular electrode concentric with the quartz crystal, with dimensions designed to be (0.9mm ± 0.2mm) × (0.8mm ± 0.2mm). Gold, a chemically stable material, is chosen for the metal electrode, and chromium is used as the substrate material. The resulting high-stability quartz resonator exhibits a cubic temperature-frequency curve within its operating temperature range. A typical curve is shown below. Figure 4 As shown, the frequency temperature stability is within ±30ppm, the frequency jump point is within ±1ppm and the resistance is stable, and the temperature symmetry point is around 28℃.

[0057] The two endpoints of the quartz oscillator 3 extending from the wide edge are respectively bonded to the gold-plated platform of the multilayer surface-mount ceramic base 2 with conductive adhesive, thereby realizing the electrical connection between the quartz oscillator 3 and the multilayer surface-mount ceramic base 1.

[0058] IV. Miniaturization design of integrated circuit temperature compensation chip 4;

[0059] The integrated circuit temperature compensation chip 4 is designed to be 0.79mm × 0.59mm in size, with a linewidth of 60μm and a pad size of 70μm × 70μm, meeting the size requirements for miniaturized temperature compensation chips. Port details are as follows... Figure 3 .

[0060] The integrated circuit temperature compensation chip 4 is constructed using a CMOS LSI (a single-chip physical structure that integrates large-scale logic function units manufactured using CMOS technology) structure, integrating a temperature sensor, a 5th-order voltage function generator, an automatic frequency control circuit, a VCXO (voltage-controlled crystal oscillator) circuit, and an erasable and rewritable non-volatile memory.

[0061] The quartz oscillator 3 is made to oscillate by providing negative impedance to the integrated circuit temperature compensation chip 4 through the voltage control circuit.

[0062] like Figure 5 As shown, the AFC circuit provides an external voltage to the integrated circuit temperature compensation chip 4 to fine-tune and correct the resonant frequency of the quartz oscillator 3;

[0063] The inherent temperature deviation of the quartz oscillator 3 is compensated by a temperature compensation circuit.

[0064] The temperature compensation coefficient of the temperature compensation circuit is adjusted by using an erasable non-volatile memory to adapt to the discreteness of different quartz oscillators.

[0065] The integrated circuit temperature compensation chip 4 provides negative impedance through the voltage control circuit to enable the quartz oscillator 3 to oscillate; the AFC (Automatic Frequency Control) circuit fine-tunes and corrects the resonant frequency of the quartz oscillator 3 through the applied voltage; the temperature compensation circuit compensates for the inherent temperature deviation of the quartz oscillator 3; and the memory adjusts the temperature compensation coefficient to adapt to the discreteness between different quartz oscillators 3.

[0066] The temperature compensation circuit integrates a bandgap reference circuit, an adder, and first-order, third-order, fourth-order, and fifth-order voltage function generators. The bandgap reference circuit adjusts the first-order temperature voltage of the pentavalent voltage function generator by shifting it up and down, while the adder amplifies and reduces the fourth-order and fifth-order temperature voltages of the pentavalent voltage function generator.

[0067] The integrated circuit temperature compensation chip 4 senses the ambient temperature through a temperature sensor. The fifth-order voltage function generator generates first-order and third to fifth-order temperature voltages from the ambient temperature and applies them to the voltage-controlled terminal of the temperature compensation varactor diode. This causes the integrated circuit temperature compensation chip 4 to generate a compensation frequency curve that is opposite to the frequency change of the quartz oscillator 3 with temperature, thereby compensating for the frequency drift of the AT-cut quartz oscillator 3 and achieving high frequency stability over the entire temperature range.

[0068] The typical frequency temperature stability test results of the high-precision temperature-compensated crystal oscillator designed in this invention are shown in Table 1, and the phase noise test results are shown in Table 2.

[0069] Table 1. Typical Frequency Temperature Stability Test Results

[0070]

[0071] Table 2 Phase noise test results

[0072]

[0073] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for miniaturizing a high-precision temperature-compensated crystal oscillator, characterized in that, The design methods include miniaturization design of multilayer surface-mount ceramic substrate (1), design of metal cover plate (2), miniaturization design of quartz oscillator (3) and miniaturization design of integrated circuit temperature compensation chip (4); The miniaturization design of the multilayer surface-mount ceramic substrate (1) includes the use of SMD3225 packaging; The design of the metal cover plate (2) includes an integrated encapsulation with the multilayer surface-mount ceramic base (1); The miniaturization design of the quartz oscillator (3) includes the use of a small rectangular quartz wafer with AT cut and high Q value; The miniaturization design of the integrated circuit temperature compensation chip (4) includes its construction using a CMOS LSI structure.

2. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 1, characterized in that, The miniaturization design of the multilayer surface-mount ceramic substrate (1) also includes: The multilayer surface-mount ceramic base (1) is designed with 5 layers. The back of the 5th layer has 4 gold-plated leads, which are the functional leads of the high-precision temperature-compensated crystal oscillator. The four gold-plated leads are for power, ground, output and debugging. The third and fourth layers of the multilayer surface-mount ceramic base (1) introduce the gold-plated leads into its chamber through vertical and wired connections. The second layer contains at least two gold-plated platforms for bonding the quartz oscillator (3). The gold-plated platform is connected to the third and fourth layers of wiring and the fifth gold-plated lead-out end of the multilayer surface-mount ceramic base (1) through a vertical connection. The first layer of the multilayer surface-mount ceramic base (1) is a sealing ring.

3. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 2, characterized in that, The design of the metal cap (2) also includes: The metal cover (2) is designed to be (2.85mm±0.2mm)×(2.15mm±0.2mm) in size, which matches the size of the sealing ring on the multilayer surface-mount ceramic base (1). The metal cover (2) and the multilayer surface-mount ceramic base (1) are integrated by resistance parallel soldering.

4. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 3, characterized in that, The miniaturization design of the quartz oscillator (3) also includes: The dimensions of the quartz oscillator (3) are designed as length × width = (2mm ± 0.1mm) × (1.3mm ± 0.1mm), and the chamfer is designed according to the frequency of the quartz crystal. The metal electrode on the quartz oscillator (3) is a rectangular electrode concentric with the quartz crystal, with a size of 0.79mm×0.59mm, a line width of 60μm, and a pad size of 70μm×70μm; The metal electrode is made of gold, and its substrate material is chromium. The two ends of the quartz oscillator (3) extending from the wide edge are respectively bonded to the gold-plated platform of the multilayer surface-mount ceramic base (2) by conductive adhesive.

5. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 4, characterized in that, The miniaturization design of the integrated circuit temperature compensation chip (4) also includes: The integrated circuit temperature compensation chip (4) integrates a temperature sensor, a 5th-order voltage function generator, an automatic frequency control circuit, a VCXO circuit, and an erasable non-volatile memory.

6. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 5, characterized in that, The miniaturization design of the integrated circuit temperature compensation chip (4) also includes: The quartz oscillator (3) is made to oscillate by providing negative impedance to the integrated circuit temperature compensation chip (4) through a voltage control circuit; The external voltage of the integrated circuit temperature compensation chip (4) is provided by the AFC circuit to fine-tune and correct the resonant frequency of the quartz oscillator (3); The inherent temperature deviation of the quartz oscillator (3) is compensated by a temperature compensation circuit; The temperature compensation coefficient of the temperature compensation circuit is adjusted by using an erasable non-volatile memory to adapt to the discreteness of different quartz oscillators (3).

7. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 6, characterized in that, The temperature compensation circuit integrates a bandgap reference circuit, an adder, and first-order, third-order, fourth-order, and fifth-order voltage function generators.

8. The miniaturized design method for a high-precision temperature-compensated crystal oscillator according to claim 7, characterized in that, The bandgap reference circuit adjusts the first-order temperature voltage of the fifth-order voltage function generator by shifting it up and down. The adder amplifies and reduces the fourth and fifth order temperature voltages of the fifth-order voltage function generator. The integrated circuit temperature compensation chip 4 senses the ambient temperature through a temperature sensor. The 5th-order voltage function generator generates the 1st and 3rd to 5th order temperature voltages from the ambient temperature and applies them to the voltage control terminal of the temperature compensation varactor diode. This causes the integrated circuit temperature compensation chip (4) to generate a compensation frequency curve that is opposite to the frequency of the quartz oscillator (3) as it changes with temperature, thereby compensating for the frequency drift of the AT-cut quartz oscillator (3).

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