Principles to be followed in medical PCB board layout design


Medical PCB boards circuit boards are the supporting part of circuit components and devices in electronic products. Even if the circuit schematic is designed correctly, improperly designed printed circuit boards can adversely affect the reliability of electronic products. So it should be designed according to certain principles.

A.Principles to be followed for medical PCB board layout design:

First, consider the size of the medical PCB board. When the PCB size is too large, the printed line will be very long, the impedance will increase, the noise immunity will decrease, and the cost will increase; if the PCB size is too small, the heat dissipation will be poor, and the neighboring lines will be easily disturbed. After determining the size of the printed circuit board, it is also necessary to determine the location of special components. All components of the circuit are then arranged according to the functional units of the circuit.

When determining the location of special components, follow the principles below:

1. Shorten the connections between high-frequency components and minimize their distribution parameters and mutual electromagnetic interference. Components susceptible to interference should not be placed too close to each other, and input and output components should be as far away as possible.

2. There may be large potential differences between certain components or wires, and the distance between them should be increased to avoid accidental short circuits due to discharges. High-voltage components should be arranged as far as possible in places that are difficult to reach during commissioning.

3. Components weighing more than 15 grams should be fixed with brackets and then soldered. Components that are large and heavy and generate a lot of heat should not be mounted on the printed circuit board, but on the chassis base plate of the whole machine, and heat dissipation should be considered. Hot components should be located away from heated components.

4. For the layout of adjustable components such as potentiometers, adjustable inductors, variable capacitors and microswitches, the structural requirements of the entire machine should be considered. If adjustments are made inside the machine, they should be placed on the printed circuit board where they can be easily adjusted; if adjustments are made outside the machine, their positions should match the positions of the adjustment knobs on the chassis panel.

5. The positions occupied by the printed circuit board positioning holes and fixing brackets should be preserved.

B. When laying out the medical PCB board for circuit components, the requirements of anti-interference design must be met:

1. Arrange the location of each functional circuit unit according to the circuit flow so that the layout facilitates signal flow and keeps the signals in the same direction.

2. Take the core component of each functional circuit as the center and arrange around it. Components should be evenly, neatly and compactly arranged on the medical PCB. Minimize and shorten the leads and connections between components.

3. For circuits operating at high frequencies, the distribution parameters between components must be considered. Usually, circuits should be connected in parallel as much as possible. In this way, it is not only aesthetically pleasing, but also easy to install and solder, and easy to mass produce.

C. When the size of the circuit board is larger than 200×150mm, the mechanical strength of the circuit board should be considered.

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