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Chinese High Frequency PCB Material Shengyi S7136 Circuit Boards #pcbfac...
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Rogers 4350B Material
Basic information:
Dielectric Constant: 3.48+-0.05,10GHZ
Dissipation factor: 0.0037/0.0031
Some Typical Applications:
• Cellular Base Station Antennas
and Power Amplifi ers
• RF Identifi cation Tags
• Automotive Radar and Sensors
• LNB’s for Direct Broadcast
Satellites
Standard Panel Size
12” X 18” (305 X457 mm)
24” X 18” (610 X 457 mm)
24” X 36” (610 X 915 mm)
48” X 36” (1.224 m X 915 mm)
Standard Copper Cladding
½ oz. (17μm) electrodeposited copper foil (.5ED/.5ED)
1 oz. (35μm) electrodeposited copper foil (1ED/1ED)
2 oz. (70μm) electrodeposited copper foil (2ED/2ED)
Standard thickness:
0.004” (0.101mm),
0.0066” (0.168mm)
0.010” (0.254mm),
0.0133” (0.338mm),
0.0166” (0.422mm),
0.020”(0.508mm),
0.030” (0.762mm),
0.060”(1.524mm)
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Principles of anti-interference design for printed circuit boards
Principles of anti-interference design for printed circuit boards
Layout of power cord:
1. According to the current size, try to widen the wire routing as much as possible.
2. The direction of power and ground wires should be consistent with the direction of data transmission.
3. A decoupling capacitor of 10-100 μ F should be connected to the power input terminal of the printed circuit board.
Layout of secondary ground wire:
1. Separate digital from analog.
2. The grounding wire should be thickened as much as possible, and at least 3 times the allowable current on the printed board should be passed, generally up to 2-3mm.
3. The grounding wire should form a dead loop as much as possible, which can reduce the potential difference of the grounding wire.
Three decoupling capacitor configuration:
1. The input end of the printed circuit board power supply is connected to an electrolytic capacitor with a temperature of 10-100 μ F. It would be even better if it could be greater than 100 μ F.
2. A 0.01~0.1 μ F ceramic capacitor is connected across the VCC and GND of each integrated chip. If space does not allow, a 1-10 μ F tantalum capacitor can be configured for every 4-10 chips.
3. Devices with weak anti noise capabilities and large changes in turn off current, as well as ROM and RAM, should have capacitors indirectly decoupled at VCC and GND.
4. Install a 0.01 μ F decoupling capacitor on the reset terminal "RESET" of the microcontroller.
5. The lead wires of decoupling capacitors should not be too long, especially for high-frequency bypass capacitors that cannot have leads.
Four component configuration:
1. The clock input terminals of the clock generator, crystal oscillator, and CPU should be as close and far away from other low-frequency devices as possible.
2. Try to keep low current circuits and high current circuits as far away from logic circuits as possible.
3. The position and orientation of the printed circuit board in the chassis should ensure that the components with high heat generation are located above.
Separate the wiring of five power lines, AC lines, and signal lines
Power lines and AC lines should be arranged on boards different from signal lines as much as possible, otherwise they should be routed separately from signal lines.
Six other principles:
1. Adding a pull-up resistor of around 10K to the bus is beneficial for anti-interference.
2. When wiring, try to have all address lines of the same length and as short as possible.
3. The lines on both sides of the PCB board should be arranged vertically as much as possible to prevent mutual interference.
4. The size of the decoupling capacitor is generally taken as C=1/F, where F is the data transmission frequency.
5. Unused pins can be connected to VCC through pull-up resistors (around 10K) or connected in parallel with the used pins.
6. Heating components (such as high-power resistors) should avoid devices that are easily affected by temperature (such as electrolytic capacitors).
7. Using full decoding has stronger anti-interference ability than line decoding.
To suppress the interference of high-power devices on the digital element circuits of microcontrollers and the interference of digital circuits on analog circuits, a high-frequency choke loop is used when connecting the digital ground to the common ground point. This is a cylindrical ferrite magnetic material with several holes in the axial direction. A thicker copper wire is passed through the holes and wound one or two times. This device can be regarded as having zero impedance for low-frequency signals and as an inductor for high-frequency signal interference Due to the high DC resistance of inductors, they cannot be used as high-frequency chokes
When signal lines outside the printed circuit board are connected, shielded cables are usually used. For high-frequency and digital signals, both ends of the shielded cable should be grounded. For low-frequency analog signals, it is better to ground one end of the shielded cable.
Circuits that are highly sensitive to noise and interference, or circuits with particularly severe high-frequency noise, should be shielded with a metal cover. The effect of ferromagnetic shielding on high-frequency noise at 500KHz is not significant, while the shielding effect of thin copper skin is better. When fixing the shielding cover with screws, attention should be paid to the corrosion caused by the potential difference when different materials come into contact
Seven good decoupling capacitors
The decoupling capacitor between the power supply and ground of an integrated circuit has two functions: on the one hand, it serves as the energy storage capacitor of the integrated circuit, and on the other hand, it bypasses the high-frequency noise of the device. The typical decoupling capacitance value in digital circuits is 0.1 μ F. The typical value of the distributed inductance of this capacitor is 5 μ H. A 0.1 μ F decoupling capacitor has a distributed inductance of 5 μ H, and its parallel resonance frequency is approximately 7MHz. This means that it has a good decoupling effect on noise below 10MHz and almost no effect on noise above 40MHz.
Capacitors with 1 μ F and 10 μ F have a parallel resonance frequency above 20MHz, which results in better removal of high-frequency noise.
Every 10 or so integrated circuits require the addition of one charging and discharging capacitor, or one energy storage capacitor, with an optional range of around 10 μ F. It is best not to use electrolytic capacitors. Electrolytic capacitors are made by rolling two layers of thin film together, and this rolled up structure appears as inductance at high frequencies. Use tantalum capacitors or polycarbonate capacitors.
The selection of decoupling capacitors is not strict, and can be based on C=1/F, that is, 0.1 μ F for 10MHz and 0.01 μ F for 100MHz.
When welding, the pins of the decoupling capacitor should be as short as possible, as long pins can cause the decoupling capacitor to self resonate. For example, when the pin length of a 1000pF ceramic capacitor is 6.3mm, the self resonant frequency is about 35MHz, and when the pin length is 12.6mm, it is 32MHz.
Eight experiences in reducing noise and electromagnetic interference
Principles of anti-interference design for printed circuit boards
1. The method of connecting resistors in series can be used to reduce the jumping rate of the upper and lower edges of the control circuit.
2. Try to make the potential around the clock signal circuit approach zero, circle the clock area with a ground wire, and keep the clock line as short as possible.
3. The I/O driver circuit should be located as close as possible to the edge of the printed board.
4. Do not hang the output terminal of the unused gate circuit, and the positive input terminal of the unused operational amplifier should be grounded, and the negative input terminal should be connected to the output terminal.
5. Try to use 45 ° polylines instead of 90 ° polylines for wiring to reduce the transmission and coupling of high-frequency signals to the outside world.
6. The clock line perpendicular to the I/O line has less interference than parallel to the I/O line.
6. The pins of the components should be as short as possible.
8. Do not trace wires under the quartz crystal oscillator and under components that are particularly sensitive to noise.
9. Do not form a current loop around the ground wire of weak signal circuits and low-frequency circuits.
10. When necessary, add ferrite high-frequency choke coils to the circuit to separate signals, noise, power, and ground.
A via on the printed circuit board causes a capacitance of approximately 0.6pF; The packaging material of an integrated circuit itself causes a distributed capacitance of 2pF~10pF; A connector on a circuit board with a distributed inductance of 520 μ H; A dual in-line 24 pin integrated circuit socket with a distributed inductance of 4 μ H~18 μ H.
Layout of power cord:
1. According to the current size, try to widen the wire routing as much as possible.
2. The direction of power and ground wires should be consistent with the direction of data transmission.
3. A decoupling capacitor of 10-100 μ F should be connected to the power input terminal of the printed circuit board.
Layout of secondary ground wire:
1. Separate digital from analog.
2. The grounding wire should be thickened as much as possible, and at least 3 times the allowable current on the printed board should be passed, generally up to 2-3mm.
3. The grounding wire should form a dead loop as much as possible, which can reduce the potential difference of the grounding wire.
Three decoupling capacitor configuration:
1. The input end of the printed circuit board power supply is connected to an electrolytic capacitor with a temperature of 10-100 μ F. It would be even better if it could be greater than 100 μ F.
2. A 0.01~0.1 μ F ceramic capacitor is connected across the VCC and GND of each integrated chip. If space does not allow, a 1-10 μ F tantalum capacitor can be configured for every 4-10 chips.
3. Devices with weak anti noise capabilities and large changes in turn off current, as well as ROM and RAM, should have capacitors indirectly decoupled at VCC and GND.
4. Install a 0.01 μ F decoupling capacitor on the reset terminal "RESET" of the microcontroller.
5. The lead wires of decoupling capacitors should not be too long, especially for high-frequency bypass capacitors that cannot have leads.
Four component configuration:
1. The clock input terminals of the clock generator, crystal oscillator, and CPU should be as close and far away from other low-frequency devices as possible.
2. Try to keep low current circuits and high current circuits as far away from logic circuits as possible.
3. The position and orientation of the printed circuit board in the chassis should ensure that the components with high heat generation are located above.
Separate the wiring of five power lines, AC lines, and signal lines
Power lines and AC lines should be arranged on boards different from signal lines as much as possible, otherwise they should be routed separately from signal lines.
Six other principles:
1. Adding a pull-up resistor of around 10K to the bus is beneficial for anti-interference.
2. When wiring, try to have all address lines of the same length and as short as possible.
3. The lines on both sides of the PCB board should be arranged vertically as much as possible to prevent mutual interference.
4. The size of the decoupling capacitor is generally taken as C=1/F, where F is the data transmission frequency.
5. Unused pins can be connected to VCC through pull-up resistors (around 10K) or connected in parallel with the used pins.
6. Heating components (such as high-power resistors) should avoid devices that are easily affected by temperature (such as electrolytic capacitors).
7. Using full decoding has stronger anti-interference ability than line decoding.
To suppress the interference of high-power devices on the digital element circuits of microcontrollers and the interference of digital circuits on analog circuits, a high-frequency choke loop is used when connecting the digital ground to the common ground point. This is a cylindrical ferrite magnetic material with several holes in the axial direction. A thicker copper wire is passed through the holes and wound one or two times. This device can be regarded as having zero impedance for low-frequency signals and as an inductor for high-frequency signal interference Due to the high DC resistance of inductors, they cannot be used as high-frequency chokes
When signal lines outside the printed circuit board are connected, shielded cables are usually used. For high-frequency and digital signals, both ends of the shielded cable should be grounded. For low-frequency analog signals, it is better to ground one end of the shielded cable.
Circuits that are highly sensitive to noise and interference, or circuits with particularly severe high-frequency noise, should be shielded with a metal cover. The effect of ferromagnetic shielding on high-frequency noise at 500KHz is not significant, while the shielding effect of thin copper skin is better. When fixing the shielding cover with screws, attention should be paid to the corrosion caused by the potential difference when different materials come into contact
Seven good decoupling capacitors
The decoupling capacitor between the power supply and ground of an integrated circuit has two functions: on the one hand, it serves as the energy storage capacitor of the integrated circuit, and on the other hand, it bypasses the high-frequency noise of the device. The typical decoupling capacitance value in digital circuits is 0.1 μ F. The typical value of the distributed inductance of this capacitor is 5 μ H. A decoupling capacitor with 0.1 μ F has a distributed inductance of 5 μ H, and its parallel resonance frequency is approximately 7MHz. This means that it has a good decoupling effect on noise below 10MHz and almost no effect on noise above 40MHz.
Capacitors with 1 μ F and 10 μ F have a parallel resonance frequency above 20MHz, which results in better removal of high-frequency noise.
Every 10 or so integrated circuits require the addition of one charging and discharging capacitor, or one energy storage capacitor, with an optional range of around 10 μ F. It is best not to use electrolytic capacitors. Electrolytic capacitors are made by rolling two layers of thin film together, and this rolled up structure appears as inductance at high frequencies. Use tantalum capacitors or polycarbonate capacitors.
The selection of decoupling capacitors is not strict, and can be based on C=1/F, that is, 0.1 μ F for 10MHz and 0.01 μ F for 100MHz.
When welding, the pins of the decoupling capacitor should be as short as possible, as long pins can cause the decoupling capacitor to self resonate. For example, when the pin length of a 1000pF ceramic capacitor is 6.3mm, the self resonant frequency is about 35MHz, and when the pin length is 12.6mm, it is 32MHz.
Eight experiences in reducing noise and electromagnetic interference
Principles of anti-interference design for printed circuit boards
1. The method of connecting resistors in series can be used to reduce the jumping rate of the upper and lower edges of the control circuit.
2. Try to make the potential around the clock signal circuit approach zero, circle the clock area with a ground wire, and keep the clock line as short as possible.
3. The I/O driver circuit should be located as close as possible to the edge of the printed board.
4. Do not hang the output terminal of the unused gate circuit, and the positive input terminal of the unused operational amplifier should be grounded, and the negative input terminal should be connected to the output terminal.
5. Try to use 45 ° polylines instead of 90 ° polylines for wiring to reduce the transmission and coupling of high-frequency signals to the outside world.
6. The clock line perpendicular to the I/O line has less interference than parallel to the I/O line.
6. The pins of the components should be as short as possible.
8. Do not trace wires under the quartz crystal oscillator and under components that are particularly sensitive to noise.
9. Do not form a current loop around the ground wire of weak signal circuits and low-frequency circuits.
10. When necessary, add ferrite high-frequency choke coils to the circuit to separate signals, noise, power, and ground.
A via on the printed circuit board causes a capacitance of approximately 0.6pF; The packaging material of an integrated circuit itself causes a distributed capacitance of 2pF~10pF; A connector on a circuit board with a distributed inductance of 520 μ H; A dual in-line 24 pin integrated circuit socket with a distributed inductance of 4 μ H~18 μ H.
Anti interference design of digital circuits and microcontrollers
In electronic system design, in order to avoid detours and save time, it is necessary to fully consider and meet the requirements of anti-interference, and avoid errors
After the design is completed, proceed with anti-interference remedial measures. There are three basic elements that form interference:
(1) Interference source refers to the components, equipment or signals that generate interference, described in mathematical language as follows: du/dt, di/dt is large ground
Fang is the source of interference. For example, lightning, relays, thyristors, motors, high-frequency clocks, etc. can all become sources of interference.
(2) The propagation path refers to the pathway or medium through which interference propagates from the interference source to the sensitive device. The typical interference propagation path is through
The conduction of wires and radiation in space.
(3) Sensitive devices refer to objects that are easily disturbed. For example: A/D, D/A converters, microcontrollers, digital ICs, weak signal amplifiers
Equipment, etc.
The basic principle of anti-interference design is to suppress interference sources, cut off interference propagation paths, and improve the anti-interference performance of sensitive devices.
(Similar to the prevention of infectious diseases)
1. Suppress interference sources
Suppressing interference sources means minimizing their du/dt and di/dt as much as possible. This is the top priority and most important principle in anti-interference design, often achieving twice the result with half the effort. Reducing the du/dt of the interference source is mainly achieved by paralleling capacitors at both ends of the interference source. Reducing the di/dt of the interference source is achieved by connecting an inductor or resistor in series with the interference source circuit and adding a freewheeling diode.
The common measures to suppress interference sources are as follows:
(1) Add a freewheeling diode to the relay coil to eliminate the back electromotive force interference generated when the coil is disconnected. Adding only a freewheeling diode will cause a delay in the disconnection time of the relay, while adding a voltage regulator diode will allow the relay to operate more times per unit time.
(2) Connect a spark suppression circuit (usually an RC series circuit, with a resistance of several K to tens of K and a capacitance of 0.01uF) in parallel at both ends of the relay contact to reduce the impact of electric sparks.
(3) Add a filtering circuit to the motor, paying attention to keeping the capacitor and inductor leads as short as possible.
(4) Each IC on the circuit board should be connected in parallel with a high-frequency capacitor of 0.01 μ F to 0.1 μ F to reduce the impact of the IC on the power supply. Pay attention to the wiring of high-frequency capacitors. The connection should be close to the power supply end and as thick and short as possible. Otherwise, it will increase the equivalent series resistance of the capacitor, which will affect the filtering effect.
(5) Avoid 90 degree creases during wiring to reduce high-frequency noise emissions.
(6) Connect RC suppression circuit at both ends of the thyristor to reduce the noise generated by the thyristor (which may cause breakdown of the thyristor in severe cases).
According to the propagation path of interference, it can be divided into two categories: conducted interference and radiated interference.
The so-called conducted interference refers to the interference that propagates through wires to sensitive devices. The frequency bands of high-frequency interference noise and useful signals are different, which can be cut off by adding filters on the wires to cut off the propagation of high-frequency interference noise. Sometimes, isolation optocouplers can also be added to solve the problem. The harm of power noise is the greatest, and special attention should be paid to handling it. The so-called radiation interference refers to the interference that propagates to sensitive devices through space radiation. The general solution is to increase the distance between the interference source and the sensitive device, isolate them with a ground wire, and add a shield on the sensitive device.
The common measures to cut off the interference propagation path are as follows:
(1) Fully consider the impact of power supply on the microcontroller. If the power supply is done well, the anti-interference of the entire circuit is solved by half. Many microcontrollers are sensitive to power noise, and it is necessary to add filtering circuits or voltage regulators to the microcontroller power supply to reduce the interference of power noise on the microcontroller. For example, a π - shaped filtering circuit can be composed of magnetic beads and capacitors. Of course, when conditions are not high, a 100 Ω resistor can also be used instead of magnetic beads.
(2) If the I/O port of the microcontroller is used to control noisy devices such as motors, isolation should be added between the I/O port and the noise source (by adding a π - shaped filtering circuit). Control noise components such as motors, and isolate them between the I/O port and the noise source by adding a π - shaped filtering circuit.
(3) Pay attention to the crystal oscillator wiring. The crystal oscillator and microcontroller pins should be as close as possible, and the clock area should be isolated with a ground wire. The crystal oscillator housing should be grounded and fixed. This measure can solve many difficult problems.
(4) Reasonable partitioning of circuit boards, such as strong and weak signals, digital and analog signals. Try to keep interference sources (such as motors and relays) as far away as possible from sensitive components (such as microcontrollers).
(5) Isolate the digital area from the analog area with a ground wire, separate the digital ground from the analog ground, and finally connect to the power ground at one point. The wiring of A/D and D/A chips is also based on this principle, and the manufacturer has considered this requirement when allocating the pin arrangement of A/D and D/A chips.
(6) The ground wires of microcontrollers and high-power devices should be separately grounded to reduce mutual interference. High power devices should be placed at the edge of the circuit board as much as possible.
(7) The use of anti-interference components such as magnetic beads, magnetic rings, power filters, and shielding covers in key areas such as microcontroller I/O ports, power lines, and circuit board connection lines can significantly improve the anti-interference performance of the circuit.
3. Improve the anti-interference performance of sensitive devices
Improving the anti-interference performance of sensitive devices refers to minimizing the picking up of interference noise from the perspective of sensitive devices, as well as methods for recovering from abnormal states as soon as possible.
The common measures to improve the anti-interference performance of sensitive devices are as follows:
(1) When wiring, try to minimize the area of the loop to reduce induced noise.
(2) When wiring, the power and ground wires should be as thick as possible. In addition to reducing pressure drop, it is more important to reduce coupling noise.
(3) For idle I/O ports of microcontrollers, do not hang them in the air. They should be grounded or powered on. The idle terminals of other ICs can be grounded or powered on without changing the system logic.
(4) The use of power monitoring and watchdog circuits for microcontrollers, such as IMP809, IMP706, IMP813, X25043, X25045, etc., can significantly improve the anti-interference performance of the entire circuit.
(5) On the premise that the speed can meet the requirements, try to reduce the crystal oscillator of the microcontroller and choose low-speed digital circuits as much as possible.
(6) IC devices should be soldered directly onto the circuit board as much as possible, with less use of IC sockets.
Let me first share my experience in this area:
In terms of software:
1. I am used to clearing all unused code space to "0" because it is equivalent to NOP and can be reset when the program runs away;
2. Add a few NOPs before the jump instruction, with the same purpose of 1;
3. When there is no hardware WatchDog, software simulation of WatchDog can be used to monitor the operation of the program;
4. When dealing with the adjustment or setting of external device parameters, in order to prevent errors caused by interference, the parameters can be resent at regular intervals, which can help the external devices recover as soon as possible;
5. Anti interference in communication can be achieved by adding data check bits and adopting a 3-to-2 or 5-to-3 strategy;
6. When there are communication lines, such as I ^ 2C and three wire systems, we have found that setting the Data line, CLK line, and INH line to high normally results in better anti-interference performance than setting them to low.
In terms of hardware:
1. The grounding and power lines are definitely important!
2. The disconnection of the route;
3. Separation of numbers and models;
4. Each digital component requires a 104 capacitor between ground and power supply;
5. In applications with relays, especially at high currents, to prevent interference from relay contact sparks on the circuit, a 104 and diode can be connected between the relay coils, and a 472 capacitor can be indirectly connected between the contacts and the starting point. The effect is good!
6. To prevent crosstalk between I/O ports, I/O ports can be isolated using methods such as diode isolation, gate circuit isolation, optocoupler isolation, electromagnetic isolation, etc;
7. Of course, the anti-interference ability of multi-layer panels is definitely better than that of single panels, but the cost is several times higher.
8. Choosing a device with strong anti-interference ability is more effective than any other method, and I think this should be the most important point. Because the inherent shortcomings of devices are difficult to compensate for through external methods, but often those with strong anti-interference ability are more expensive, while those with poor anti-interference ability are cheaper, just like Taiwan's Dongdong is cheap but its performance is greatly reduced! It mainly depends on your application scenarios
Printed circuit board (PC8) is a supporting component for circuit components and devices in electronic products. It provides electrical connections between circuit components and devices. With the rapid development of electrical technology, the density of PGB is getting higher and higher. The quality of PCB design has a significant impact on its anti-interference ability. Therefore, when designing PCBs, it is necessary to follow the general principles of PCB design and meet the requirements of anti-interference design.
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Rogers4350B PCB Manufacturer
1、 Overview of the Characteristics of Rogers RO4350B High Frequency Plate:
This board has precise dielectric constant control (Dk: 3.48+/-0.05), effectively reduces losses (Df: 0.0037 10GHz), is suitable for large-scale production, and has excellent CAF impedance. Meanwhile, its processing technology is compatible with the standard epoxy resin/glass cloth process.
Rogers RO4350B high-frequency board is fully compatible with traditional PCB manufacturing processes, without the need for special treatments such as through-hole copper plating pre-treatment or plasma treatment, and supports grinding operations for solder mask processes. Compared to traditional microwave material laminates, it has a more advantageous price and is widely used to meet the UL 94V-0 fire rating requirements for active devices and high-power RF designs.
This board adopts a unique textile glass cloth reinforced ceramic filling material and hydrocarbon composite technology, combining the electrical properties of PTFE/glass cloth materials with the processability of epoxy resin/glass cloth.
2、 In depth analysis of the key characteristics of Rogers RO4350B board:
1. It has extremely low RF loss characteristics, with a loss factor (Df) of only 0.0037 at 10GHz.
2. The dielectric constant (Dk) is stable and accurate, maintained within the range of 3.48+/-0.05, and has low temperature fluctuations.
3. Demonstrate excellent Z-axis thermal expansion control performance, with a thermal expansion coefficient of 32 ppm/℃.
4. Low internal expansion coefficient ensures the stability of the board structure.
5. The dielectric constant tolerance is extremely small, ensuring consistency in electrical performance.
6. Excellent dimensional stability, suitable for high-precision applications.
At different frequencies, the electrical characteristics are stable and suitable for various application scenarios.
8. The processing technology is similar to FR-4, making it easy to achieve large-scale production and multi-layer mixed pressing, thus having a significant competitive advantage in terms of price.
In the regular inventory of ONESEINE, Rogers RO4350B high-frequency sheet has various thickness specifications, including 4mil, 6.6mil, 10mil, 13.3mil, 16.6mil, 20mil, 30mil, and 60mil, to meet different design requirements.
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FR408HR HDI PCB (High-Density Interconnect Printed Circuit Board)
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China High frequency PCB Arlon AD350 Material Circuit Boards Manufacturer
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