What Are the Different Types of PCB Assembly Jobs?

The design of the printed circuit board is based on the circuit schematic diagram to achieve the functions required by the circuit designer. The design of the printed circuit board mainly refers to the layout design, and the layout of external connections needs to be considered. Optimized layout of internal electronic components. Optimized layout of metal connections and vias. Electromagnetic protection. Various factors such as heat dissipation. Excellent layout design can save production costs and achieve good circuit performance and heat dissipation performance. Simple layout design can be realized by hand, and complex layout design needs to be realized by computer aided design (CAD).

PCB design

Controllable in high-speed designs

First, the domestic use is more

High speed ADCs are usually

The design of the circuit schematic is the entire

In PCB design, in fact, it takes a long time before the formal wiring. The following is the main process of PCB design:

The traditional PCB design process is no longer applicable in the field of high-speed PCB design, even at higher signal rates. High-speed PCB design must be perfectly combined with simulation and verification. And simulation is not a simple verification of the design in the traditional sense, but the pre-simulation embedded in the entire design process to get the rules, rule-driven design, and the final post-simulation verification.

(1) Avoid arranging important signal lines, such as clocks and reset signals, on the edge of the PCB.

(2) The space between the chassis ground and the signal line should be at least 4 mm; keep the aspect ratio of the chassis ground to less than 5: 1 to reduce the inductance effect.

(3) Positioned devices and lines are locked with the LOCK function so that they will not be accidentally moved in the future.

(4) The minimum width of the wire should not be less than 0.2mm (8mil). In high-density and high-precision printed circuits, the wire width and spacing can generally be 12mil.

(5) For the routing between IC pins in DIP packages, the principles of 10-10 and 12-12 can be applied, that is, when two wires pass between the two pins, the pad diameter can be set to 50mil, and the line width and line pitch are 10mil, when only one wire passes between the two feet, the pad diameter can be set to 64mil, and the line width and line spacing are both 12mil.

(6) When the diameter of the pad is 1.5mm, in order to increase the peel resistance of the pad, a length of not less than 1.5mm, a width of 1.5mm and an oblong pad can be used.

(7) When the design encounters a thin trace connected to the pad, the connection between the pad and the trace should be designed in a water droplet shape, so that the pad is not easy to peel, and the trace and the pad are not easily disconnected.

(8) When designing large-area copper-clad copper, there should be an open window on the copper-plated copper, add heat dissipation holes, and design the open window into a mesh shape.

(9) Shorten the connection between high-frequency components as much as possible, reduce their distribution parameters and electromagnetic interference between them. Vulnerable components should not be placed too close to each other, and input and output components should be kept as far away as possible.

1. High-frequency components: The shorter the connection between high-frequency components, the better. Try to reduce the distribution parameters of the connection and the electromagnetic interference between them. Components that are susceptible to interference cannot be too close. The distance between the components attached to the input and the output should be as large as possible.

2. Components with high potential difference: The distance between the components with high potential difference and the wiring should be increased to avoid damaging the components in the event of an accidental short circuit. In order to avoid the occurrence of creepage phenomenon, it is generally required that the copper film line distance between 2000V potential differences should be greater than 2mm. For higher potential differences, the distance should also be increased. Devices with high voltage should be placed as hard as possible during the debugging process.

3. Components that are too heavy: such components should be fixed by brackets, and for large, heavy and heat-generating components, they should not be installed on circuit boards.

4. Fever and heat-sensitive element: Note that the heat-generating element should be far away from the heat-sensitive element.

In the design, from the perspective of the PCB assembly, the following parameters should be considered:
1) The diameter of the hole is determined according to the maximum material condition (MMC) and minimum material condition (LMC). The diameter of the hole of an unsupported component should be selected such that the MMC of the pin is subtracted from the MMC of the hole, and the resulting difference is between 0.15-0.5mm. And for ribbon pins, the difference between the nominal diagonal of the pin and the unsupported hole will not exceed 0.5mm and not less than 0.15mm.
2) Place the smaller components reasonably so that they are not covered by the larger components.
3) The thickness of solder mask should not be greater than 0.05mm.
4) The screen-printed logo must not intersect with any pad.
5) The upper half of the circuit board should be the same as the lower half to achieve structural symmetry. Because asymmetric circuit boards can become warped.