PCB Technical - The most complete PCB circuit design inspection items

After the electronic engineer has designed the PCB, he needs to conduct a comprehensive check on the rationality of the design. The following checklist includes all aspects related to the design cycle, and some additional items should be added for special applications.

General PCB design drawing inspection items

1) Has the circuit been analyzed? Is the circuit divided into basic units in order to smooth the signal?

2) Does the circuit allow the use of short or isolated key leads?

3) Is the area that must be shielded effectively shielded?

4) Have you made full use of the basic grid graphics?

5) Is the size of the printed circuit board the best size?

6) Do you use the selected wire width and spacing as much as possible?

7) Has the preferred pad size and hole size been used?

8) Are the photographic plates and sketches appropriate?

9) Is the jumper used the least? Do jumper wires pass through components and accessories?

l0) Are the letters visible after assembly? Is its size and model correct?

11) In order to prevent blistering, is there any window in the large area of copper foil?

12) Are there tool positioning holes?

PCB electrical characteristics inspection items

1) Has the influence of wire resistance, inductance and capacitance been analyzed? In particular, is the impact of the critical pressure drop grounded?

2) Do the spacing and shape of the wire accessories meet the insulation requirements?

3) Has the insulation resistance value been controlled and specified in key areas?

4) Is the polarity fully recognized?

5) Is the influence of wire spacing on leakage resistance and voltage measured from a geometrical point of view?

6) Has the medium for changing the surface coating been identified?

PCB physical characteristics inspection items

1) Are all pads and their positions suitable for final assembly?

2) Can the assembled printed circuit board meet the shock and vibration conditions?

3) What is the required spacing of standard components?

4) Are the components that are not firmly installed or the heavier parts fixed?

5) Is the heat dissipation and cooling of the heating element correct? Or is it isolated from the printed circuit board and other thermal components?

6) Are the voltage divider and other multi-lead components positioned correctly?

7) Is the arrangement and orientation of components easy to check?

8) Have all possible interferences on the printed circuit board and the entire printed circuit board assembly been eliminated?

9) Is the size of the positioning hole correct?

10) Are the tolerances complete and reasonable?

11) Have you controlled and signed the physical properties of all coatings?

12) Is the diameter ratio of the hole to the lead wire within the acceptable range?

PCB mechanical design factors

Although the printed circuit board adopts mechanical methods to support the components, it cannot be used as a structural part of the entire device. On the edge of the printing plate, at least every 5 inches for a certain amount of support.

The factors that must be considered when selecting and designing printed circuit boards are as follows;

1) The structure of the printed circuit board-size and shape.

2) Types of mechanical accessories and plugs (seats) required.

3) The adaptability of the circuit to other circuits and environmental conditions.

4) According to some factors, such as heat and dust, consider installing the printed circuit board vertically or horizontally.

5) Some environmental factors that require special attention, such as heat dissipation, ventilation, shock, vibration, and humidity. Dust, salt spray and radiation.

6) The degree of support.

7) Keep and fix.

8) Easy to take off.

PCB printed circuit board installation requirements

It should be supported at least within 1 inch of the three edges of the printed circuit board. According to practical experience, the distance between the supporting points of a printed circuit board with a thickness of 0.031-0.062 inches should be at least 4 inches; for a printed circuit board with a thickness greater than 0.093 inches, the distance between the supporting points should be at least 5 inches. Taking this measure can improve the rigidity of the printed circuit board and destroy the possible resonance of the printed circuit board.

Certain printed circuit boards usually have to consider the following factors before deciding which mounting technology they use.

1) The size and shape of the printed circuit board.

2) Number of input and output terminals.

3) Available equipment space.

4) The desired ease of loading and unloading.

5) Types of attachments.

6) Required heat dissipation.

7) The required shieldability.

8) The type of circuit and its relationship with other circuits.

Call out requirements for printed circuit boards

1) There is no need to install the printed circuit board area of the component.

2) The influence of the plug-in tool on the installation distance between two printed circuit boards.

3) Specially prepare mounting holes and slots in the printed circuit board design.

4) When the plug-in tool is to be used in the equipment, especially its size should be considered.

5) A plug-in device is required, which is usually permanently fixed to the printed circuit board assembly with rivets.

6) In the mounting frame of the printed circuit board, special design such as load bearing flange is required.

7) The adaptability of the plug-in tools used and the size, shape and thickness of the printed circuit board.

8) The cost involved in using plug-in tools includes both the price of the tool and the increased expenditure.

9) In order to fasten and use plug-in tools, it is required to have access to the inside of the equipment to a certain extent.