1. What determines the accuracy of a PCB copy?
The accuracy of a PCB copy depends on two factors: the precision of the software and the quality of the original image. Different PCB copy companies have varying technical capabilities when it comes to copying accuracy. Some PCB manufacturers have limited circuit board copying technology, resulting in lower accuracy, while others possess advanced technology, allowing them to achieve copy accuracy below 1 mil.
In terms of PCB software, the use of 32-bit floating point representation generally imposes no accuracy limits. Therefore, the most critical factor is the image quality of the original scan. For instance, taking a 1-megapixel photo might suffice for printing a 5-inch image, but it would not provide enough detail for a 20-inch print. The same principle applies to PCB copying—if you need a highly accurate PCB reproduction, choosing a higher DPI for scanning is essential.
1. **DPI and Its Impact on Accuracy**
DPI stands for “dots per inch,” which refers to the resolution of a scanned image. Specifically, it defines the distance between two points on the image. The formula for this distance is 1000/DPI, where the unit is mil.
For example, if the DPI is 400, the distance between two points is 1000/400 = 2.5 mil. This means the accuracy at this setting is 2.5 mil.
This is the fundamental principle, and some people claim that accuracy can be below 1 mil, but this is under specific conditions. In practice, the accuracy of PCB copying largely depends on the scanning resolution of the original image.
In summary, when scanning a PCB, the DPI setting should align with the required accuracy for the specific board. For instance, if the circuit lines of a mobile phone board need to be below 1 mil in accuracy, the DPI should be set above 1000. Many scanners available today can meet this requirement.
Higher DPI results in a clearer image and greater accuracy, but the downside is that the file size becomes larger, which demands higher hardware performance. Therefore, the DPI should be set according to the specific needs of the task. For general PCB accuracy, 400 DPI is typically sufficient, while for mobile phone PCBs, settings above 1000 DPI are recommended.
2. **PCB Energy Storage Capacitors**
PCB energy storage capacitors help maintain stable power supply voltage even when the load changes rapidly. These capacitors can be categorized into system-level, board-level, and device-level capacitors.
**1: System-Level Energy Storage Capacitors**
System-level energy storage capacitors collect charge through rectifiers and transfer the stored energy to the power supply output via the converter leads. Commonly used components include aluminum electrolytic capacitors, such as the B43504 or B43505 models from EP-COS, with voltage ratings between 40V and 450V (DC) and capacitances ranging from 220 μF to 150,000 μF. Depending on power requirements, these capacitors are often arranged in series, parallel, or combined forms. For power supplies over 10 kW, larger, tank-shaped screw-terminal capacitors are typically used.
**2: Board-Level Energy Storage Capacitors**
Board-level capacitors ensure that the voltage on the PCB remains stable during rapid load changes. To achieve this, large-capacity tantalum capacitors (e.g., 22 μF, 33 μF) are placed on high-frequency, high-speed PCBs to maintain consistent voltage levels across the board.
**3: Device-Level Energy Storage Capacitors**
Device-level capacitors stabilize the voltage around a specific device, preventing drops when the load fluctuates quickly. For devices with high operating frequencies and power consumption, placing 1 to 4 large-capacity tantalum capacitors around the device is recommended to maintain voltage stability.
**Guidelines for Placing Energy Storage Capacitors**
– Near the input of the power supply connector
– Close to the power terminals connecting daughter boards, peripherals, and auxiliary circuits
– Near high-power digital components
– Farthest from the power input terminal
– In component-dense areas far from the power supply’s digital terminals
– Close to the clock generation circuit
The accuracy of a PCB copy depends on two factors: the precision of the software and the quality of the original image. Different PCB copy companies have varying technical capabilities when it comes to copying accuracy. Some PCB manufacturers have limited circuit board copying technology, resulting in lower accuracy, while others possess advanced technology, allowing them to achieve copy accuracy below 1 mil.
In terms of PCB software, the use of 32-bit floating point representation generally imposes no accuracy limits. Therefore, the most critical factor is the image quality of the original scan. For instance, taking a 1-megapixel photo might suffice for printing a 5-inch image, but it would not provide enough detail for a 20-inch print. The same principle applies to PCB copying—if you need a highly accurate PCB reproduction, choosing a higher DPI for scanning is essential.
1. **DPI and Its Impact on Accuracy**
DPI stands for “dots per inch,” which refers to the resolution of a scanned image. Specifically, it defines the distance between two points on the image. The formula for this distance is 1000/DPI, where the unit is mil.
For example, if the DPI is 400, the distance between two points is 1000/400 = 2.5 mil. This means the accuracy at this setting is 2.5 mil.
This is the fundamental principle, and some people claim that accuracy can be below 1 mil, but this is under specific conditions. In practice, the accuracy of PCB copying largely depends on the scanning resolution of the original image.
In summary, when scanning a PCB, the DPI setting should align with the required accuracy for the specific board. For instance, if the circuit lines of a mobile phone board need to be below 1 mil in accuracy, the DPI should be set above 1000. Many scanners available today can meet this requirement.
Higher DPI results in a clearer image and greater accuracy, but the downside is that the file size becomes larger, which demands higher hardware performance. Therefore, the DPI should be set according to the specific needs of the task. For general PCB accuracy, 400 DPI is typically sufficient, while for mobile phone PCBs, settings above 1000 DPI are recommended.
2. **PCB Energy Storage Capacitors**
PCB energy storage capacitors help maintain stable power supply voltage even when the load changes rapidly. These capacitors can be categorized into system-level, board-level, and device-level capacitors.
**1: System-Level Energy Storage Capacitors**
System-level energy storage capacitors collect charge through rectifiers and transfer the stored energy to the power supply output via the converter leads. Commonly used components include aluminum electrolytic capacitors, such as the B43504 or B43505 models from EP-COS, with voltage ratings between 40V and 450V (DC) and capacitances ranging from 220 μF to 150,000 μF. Depending on power requirements, these capacitors are often arranged in series, parallel, or combined forms. For power supplies over 10 kW, larger, tank-shaped screw-terminal capacitors are typically used.
**2: Board-Level Energy Storage Capacitors**
Board-level capacitors ensure that the voltage on the PCB remains stable during rapid load changes. To achieve this, large-capacity tantalum capacitors (e.g., 22 μF, 33 μF) are placed on high-frequency, high-speed PCBs to maintain consistent voltage levels across the board.
**3: Device-Level Energy Storage Capacitors**
Device-level capacitors stabilize the voltage around a specific device, preventing drops when the load fluctuates quickly. For devices with high operating frequencies and power consumption, placing 1 to 4 large-capacity tantalum capacitors around the device is recommended to maintain voltage stability.
**Guidelines for Placing Energy Storage Capacitors**
– Near the input of the power supply connector
– Close to the power terminals connecting daughter boards, peripherals, and auxiliary circuits
– Near high-power digital components
– Farthest from the power input terminal
– In component-dense areas far from the power supply’s digital terminals
– Close to the clock generation circuit
