General inspection items for PCB design drawings:
1) Has the circuit been analyzed? Is it divided into basic units to ensure smooth signal flow?
2) Does the circuit allow for the use of short or isolated signal paths?
3) Is the area requiring shielding effectively shielded?
4) Have basic grid graphics been fully utilized?
5) Is the size of the printed circuit board optimal?
6) Have the selected trace widths and spacing been maximized?
7) Have preferred pad sizes and hole sizes been used?
8) Are the PCB artwork and silkscreen appropriately prepared?
9) Are jumpers minimized? Do jumper wires avoid passing through components and accessories?
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10) Are the letters visible after assembly? Is its size and model correct?
11) Is there any copper foil blistering prevention window in the large area?
12) Are there tool positioning holes?
**PCB Electrical Characteristics Inspection Items**
1) Have wire resistance, inductance, and capacitance influences been analyzed? Specifically, has the impact of critical voltage drop been grounded?
2) Do wire accessory spacing and shapes meet insulation requirements?
3) Has insulation resistance been controlled and specified in key areas?
4) Is polarity fully identified?
5) Has the influence of wire spacing on leakage resistance and voltage been geometrically measured?
6) Has the change in surface coating medium been identified?
**PCB Physical Characteristics Inspection Items**
1) Are all pads and their positions suitable for final assembly?
2) Can the assembled PCB meet shock and vibration conditions?
3) What is the required spacing for standard components?
4) Are loosely installed or heavy components securely fixed?
5) Is the heat dissipation and cooling of heating elements correct? Are they isolated from other thermal components on the PCB?
6) Are voltage dividers and other multi-lead components correctly positioned?
7) Is component arrangement and orientation easy to verify?
8) Have all potential interferences within the PCB and assembly been eliminated?
9) Are positioning hole sizes correct?
10) Are tolerances comprehensive and reasonable?
11) Have physical properties of all coatings been controlled and documented?
12) Are hole-to-lead wire diameter ratios within acceptable limits?
**PCB Mechanical Design Factors**
While PCBs support components mechanically, they cannot serve as structural parts of the entire device. At least every 5 inches on the PCB edge requires a certain amount of support.
Factors to consider in PCB selection and design include:
1) PCB structure – size and shape.
2) Types of mechanical fixtures and connectors required.
3) Circuit compatibility with other circuits and environmental conditions.
4) Consider mounting PCBs vertically or horizontally based on factors like heat and dust.
5) Environmental factors such as heat dissipation, ventilation, shock, vibration, humidity, dust, salt spray, and radiation.
6) Degree of support.
7) Retention and fixation.
8) Ease of removal.
**PCB Installation Requirements**
Support should extend at least 1 inch from all three edges of the PCB. For PCBs with thicknesses of 0.031-0.062 inches, support points should be at least 4 inches apart; for thicknesses over 0.093 inches, support points should be at least 5 inches apart to improve rigidity and prevent resonance.
Consider the following factors before selecting mounting technologies:
1) PCB size and shape.
2) Number of input and output terminals.
3) Available equipment space.
4) Ease of loading and unloading.
5) Types of attachments.
6) Required heat dissipation.
7) Desired shieldability.
8) Circuit type and its interaction with other circuits.
**Requirements for PCBs with Mounting Frames**
1) No components should obstruct the PCB installation area.
2) Consider the installation distance between two PCBs affected by plug-in tooling.
3) Design PCBs with specially prepared mounting holes and slots.
4) Consider the size of plug-in tools, especially when used in equipment.
5) Attach plug-in devices securely to the PCB assembly using rivets.
6) Design mounting frames with load-bearing flanges for PCBs.
7) Ensure compatibility between plug-in tools and PCB size, shape, and thickness.
8) Consider costs associated with plug-in tool usage, including tool price and additional expenses.
9) Ensure sufficient equipment access for plug-in tool fastening and use.
