1. Single-sided printed circuit boards are commonly utilized in consumer electronics like radios, tape recorders, televisions, and electronic game consoles.
2. Their manufacturing cost is among the lowest of all printed boards.
3. Single-sided printed circuit boards can also be used in industrial electronic products.
4. Primarily, based on the complexity and density of the circuit and the assembly requirements of the entire system, single-sided printed circuit boards are suitable when all interconnections can be achieved on one side.
1. When a single-sided printed circuit board cannot achieve complete interconnection, the design of a double-sided printed circuit board should be considered. Most double-sided printed circuit boards use metallized holes to facilitate through-connection of conductors on both sides. In some cases, double-sided printed circuit boards with non-metallized holes may also be employed, relying on insertion holes for component leads to achieve through-connection. Consider designing a multilayer printed circuit board when: 1) A double-sided printed circuit board cannot achieve full interconnection, necessitating additional jumper wires. 2) Light weight and compact size are required. 3) High-speed circuits are involved. The short interconnecting wires of a multilayer printed circuit board reduce attenuation of high-speed pulse signals. The ground layer provides effective shielding for the high-speed signal layer, and the distributed capacitance between the ground and power layers offers excellent decoupling for the power supply. 4) High reliability is needed. Combining several double-sided printed circuit board assemblies into a single multilayer board can enhance the reliability of the entire electronic product. 5) Simplified printed circuit board layout and photographic basemap design are needed. Some double-sided printed circuit board layouts can be very complex due to intricate interconnections. A multilayer printed circuit board allows for separation of power or ground wires from signal wires, with layers arranged to optimize grounding. To meet specific assembly needs, reduce weight, and improve assembly density, flexible printed circuits or flexible-rigid printed circuits may be used. Flexible printed circuits can also function as connecting cables, saving time on soldering and minimizing assembly errors. For moving electronic components, flexible printed circuits are also applicable. When a printed circuit board must handle large currents or significant power consumption that exceeds allowable operating temperatures, a design incorporating a metal core or surface heat sink is necessary. For rotary switches or contact encoder discs, flush printed circuits should be designed.
2. **Coordinate Network System** When designing printed circuit boards, a coordinate network system is typically used. Component leads are inserted into assembly holes located at grid intersections. This grid system facilitates easy compilation or automatic generation of control programs for computer-aided design (CAD) systems, automatic optical drawing machines, numerical control drilling devices, computer-aided testing (CAT) systems, and automatic component insertion devices. For manual layout and photographic basemap production, the coordinate grid system simplifies calculations and operations. According to the national standard “Printed Circuit Grid System” GB1360-1998, the basic grid spacing is 2.5mm. Auxiliary grids with spacings of 1mm, 2mm (1.25mm), or 1/4 (0.625mm) of the basic grid may also be used. For printed circuit boards designed for integrated circuits with a 2.54mm center-to-center lead spacing, a 2.54mm basic grid is appropriate. This system also includes secondary grids with spacings of 1.27mm and 0.635mm.
3. **Design Enlargement Ratio** The dimensional accuracy of the printed circuit board often requires photographic base maps to be made at scales of 1:1, 2:1, or even 4:1. The layout sketch of the printed circuit board should be drawn to the same scale to avoid redrawing and to facilitate checking. The 2:1 magnification ratio is commonly used for layout sketches or photographic basemaps, balancing high accuracy and convenience. The 4:1 magnification ratio is employed for high-precision boards or when using digital instruments for high-precision conductive pattern programming. A 1:1 scale design layout is suitable only for simple double-sided printed circuit boards or multi-layer boards with straightforward power and ground planes.
4. **Production Conditions** Designing printed circuit boards requires awareness of and familiarity with production conditions. This includes methods for creating photographic plates (e.g., photographic reduction, light drawing, 1:1 mapping), the size of the base image allowed by the photographic platesetter, the dimensions of the printed circuit board processed by each machine, the accuracy of drilling machines, blanking requirements, fine wire pattern printing technology, and etching accuracy.
5. **Standardization** Standardization aims to simplify the printed circuit board production process, shorten production cycles, reduce costs, and ensure quality control. Designers must adhere to applicable standards, including National Standards (GB), International Electrotechnical Commission (IEC TC52), US Military Specifications (MIL), British Standards (BS), Japanese Industrial Standards (JIS), and Japan Printed Circuit Association (JPCA), among others.
6. **Design Documents**
1) **Circuit Diagram (Electrical Schematic Diagram)**: In addition to the common methods for expressing circuit connections, the circuit diagram should indicate special components as per design requirements, such as input, output, and connector relationships, key signal line lengths, conductors protected by ground wires, conductors of specific widths, devices generating electromagnetic interference, components producing significant heat, and thermal elements.
2) **Components Table**: This list includes all resistors, capacitors, transistors, diodes, integrated circuits, transformers, inductors, heat sinks, and metal parts. It should specify the corresponding numbers from the circuit diagram (e.g., R1, R2, C1, C2), component specifications, metal part matching requirements, mechanical dimensions, and, if necessary, reference actual component samples.
3) **Component Wiring Table**: Generally used in CAD automatic routing, this table represents the connection relationships between components.
4) **Machining Drawing**: Essential for machining printed circuit boards, this includes:
a. Overall dimensions and deviations of the printed circuit board, including the printed plug portion, mechanical mounting hole dimensions, and deviations from the reference datum.
b. Details of the copper clad laminate used, including name, symbol, thickness, and copper foil thickness. Emphasis may be placed on the thickness of the insulating substrate between copper foils.
c. Technical requirements for surface coating, such as tin-lead coating thickness, tin-lead ratio, nickel or gold coating thickness, etc.
d. Surface coating requirements, such as solderability coatings and solder mask coatings.
e. Assembly drawings and the component table, both crucial for the electrical assembly of the printed circuit boards.
2. Their manufacturing cost is among the lowest of all printed boards.
3. Single-sided printed circuit boards can also be used in industrial electronic products.
4. Primarily, based on the complexity and density of the circuit and the assembly requirements of the entire system, single-sided printed circuit boards are suitable when all interconnections can be achieved on one side.
1. When a single-sided printed circuit board cannot achieve complete interconnection, the design of a double-sided printed circuit board should be considered. Most double-sided printed circuit boards use metallized holes to facilitate through-connection of conductors on both sides. In some cases, double-sided printed circuit boards with non-metallized holes may also be employed, relying on insertion holes for component leads to achieve through-connection. Consider designing a multilayer printed circuit board when: 1) A double-sided printed circuit board cannot achieve full interconnection, necessitating additional jumper wires. 2) Light weight and compact size are required. 3) High-speed circuits are involved. The short interconnecting wires of a multilayer printed circuit board reduce attenuation of high-speed pulse signals. The ground layer provides effective shielding for the high-speed signal layer, and the distributed capacitance between the ground and power layers offers excellent decoupling for the power supply. 4) High reliability is needed. Combining several double-sided printed circuit board assemblies into a single multilayer board can enhance the reliability of the entire electronic product. 5) Simplified printed circuit board layout and photographic basemap design are needed. Some double-sided printed circuit board layouts can be very complex due to intricate interconnections. A multilayer printed circuit board allows for separation of power or ground wires from signal wires, with layers arranged to optimize grounding. To meet specific assembly needs, reduce weight, and improve assembly density, flexible printed circuits or flexible-rigid printed circuits may be used. Flexible printed circuits can also function as connecting cables, saving time on soldering and minimizing assembly errors. For moving electronic components, flexible printed circuits are also applicable. When a printed circuit board must handle large currents or significant power consumption that exceeds allowable operating temperatures, a design incorporating a metal core or surface heat sink is necessary. For rotary switches or contact encoder discs, flush printed circuits should be designed.
2. **Coordinate Network System** When designing printed circuit boards, a coordinate network system is typically used. Component leads are inserted into assembly holes located at grid intersections. This grid system facilitates easy compilation or automatic generation of control programs for computer-aided design (CAD) systems, automatic optical drawing machines, numerical control drilling devices, computer-aided testing (CAT) systems, and automatic component insertion devices. For manual layout and photographic basemap production, the coordinate grid system simplifies calculations and operations. According to the national standard “Printed Circuit Grid System” GB1360-1998, the basic grid spacing is 2.5mm. Auxiliary grids with spacings of 1mm, 2mm (1.25mm), or 1/4 (0.625mm) of the basic grid may also be used. For printed circuit boards designed for integrated circuits with a 2.54mm center-to-center lead spacing, a 2.54mm basic grid is appropriate. This system also includes secondary grids with spacings of 1.27mm and 0.635mm.
3. **Design Enlargement Ratio** The dimensional accuracy of the printed circuit board often requires photographic base maps to be made at scales of 1:1, 2:1, or even 4:1. The layout sketch of the printed circuit board should be drawn to the same scale to avoid redrawing and to facilitate checking. The 2:1 magnification ratio is commonly used for layout sketches or photographic basemaps, balancing high accuracy and convenience. The 4:1 magnification ratio is employed for high-precision boards or when using digital instruments for high-precision conductive pattern programming. A 1:1 scale design layout is suitable only for simple double-sided printed circuit boards or multi-layer boards with straightforward power and ground planes.
4. **Production Conditions** Designing printed circuit boards requires awareness of and familiarity with production conditions. This includes methods for creating photographic plates (e.g., photographic reduction, light drawing, 1:1 mapping), the size of the base image allowed by the photographic platesetter, the dimensions of the printed circuit board processed by each machine, the accuracy of drilling machines, blanking requirements, fine wire pattern printing technology, and etching accuracy.
5. **Standardization** Standardization aims to simplify the printed circuit board production process, shorten production cycles, reduce costs, and ensure quality control. Designers must adhere to applicable standards, including National Standards (GB), International Electrotechnical Commission (IEC TC52), US Military Specifications (MIL), British Standards (BS), Japanese Industrial Standards (JIS), and Japan Printed Circuit Association (JPCA), among others.
6. **Design Documents**
1) **Circuit Diagram (Electrical Schematic Diagram)**: In addition to the common methods for expressing circuit connections, the circuit diagram should indicate special components as per design requirements, such as input, output, and connector relationships, key signal line lengths, conductors protected by ground wires, conductors of specific widths, devices generating electromagnetic interference, components producing significant heat, and thermal elements.
2) **Components Table**: This list includes all resistors, capacitors, transistors, diodes, integrated circuits, transformers, inductors, heat sinks, and metal parts. It should specify the corresponding numbers from the circuit diagram (e.g., R1, R2, C1, C2), component specifications, metal part matching requirements, mechanical dimensions, and, if necessary, reference actual component samples.
3) **Component Wiring Table**: Generally used in CAD automatic routing, this table represents the connection relationships between components.
4) **Machining Drawing**: Essential for machining printed circuit boards, this includes:
a. Overall dimensions and deviations of the printed circuit board, including the printed plug portion, mechanical mounting hole dimensions, and deviations from the reference datum.
b. Details of the copper clad laminate used, including name, symbol, thickness, and copper foil thickness. Emphasis may be placed on the thickness of the insulating substrate between copper foils.
c. Technical requirements for surface coating, such as tin-lead coating thickness, tin-lead ratio, nickel or gold coating thickness, etc.
d. Surface coating requirements, such as solderability coatings and solder mask coatings.
e. Assembly drawings and the component table, both crucial for the electrical assembly of the printed circuit boards.
