Component Misalignment: Circuit Board Issues and Solutions

Component Misalignment: Circuit Board Issues and Solutions

Polarity components require special attention throughout the PCBA processing, as incorrect orientation can lead to mass failures and the complete failure of the PCBA board. Therefore, it is crucial for engineering and production personnel to understand SMT polarity components.

1. Definition of Polarity

Polarity refers to the positive and negative terminals of a component or the first pin aligned with the positive and negative terminals on the PCB (Printed Circuit Board). If the orientation of the component does not match that on the PCB, it is referred to as reverse polarity failure.

2. Methods for Identifying Polarity

1. Chip Resistors (Resistor) – Non-Polarized

Component Misalignment: Circuit Board Issues and Solutions

2. Capacitors (Capacitor)

2.1 Ceramic Capacitors – Non-Polarized

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.2.1 Ceramic Capacitor (Non-Polarized)

2.2 Tantalum Capacitors – Polarized

PCB and component positive terminal markings: 1) Color band; 2) “+” sign; 3) Diagonal marking.

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.2.2 Tantalum Capacitor – Polarized

2.3 Aluminum Electrolytic Capacitors – Polarized

Component marking: Color band represents negative; PCB marking: Color band or “+” sign represents positive terminal.

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.2.3 Aluminum Electrolytic Capacitor – Polarized

3. Inductors (Inductor)

3.1 Chip Coils

Chip inductors and similar two-terminal packages have no polarity requirements.

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.3.1 Chip Inductor – Non-Polarized

3.2 Multi-Pin Inductors

Multi-pin inductors have polarity requirements. Component marking: Dot/“1” represents polarity point; PCB marking: Dot/Circle/“*” represents polarity point.

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.3.2 Multi-Pin Inductor

4. Light Emitting Diodes (LED)

4.1 SMT Surface-Mount LED

Surface-mount LEDs are polarized.

  • Component negative terminal marking: Green indicates negative;
  • PCB negative terminal marking: 1) Vertical bar; 2) Color band; 3) Silkscreen pointed corner; 4) Silkscreen “匚” frame.
Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.4.1 Surface-Mount LED Component

5. Diodes (Diode)

5.1 SMT Surface-Mount Two-Terminal Diodes

Surface-mount two-terminal diodes are polarized.

  • Component negative terminal marking: 1) Color band, 2) Groove, 3) Color marking (glass body);
  • PCB negative terminal marking: 1) Vertical bar marking, 2) Color band marking, 3) Silkscreen pointed corner marking, 4) “匚” frame marking.
Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 251. Surface-Mount Diode with Polarity

6. Integrated Circuits (Integrated Circuit)

6.1 SOIC Package Type

This type of package is polarized. Polarity markings: 1) Color band, 2) Symbol, 3) Dimple/Groove, 4) Slanted edge.

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.6.1 Polarity Marking of Integrated Circuit

6.2 SOP or QFP Package Type

This type of package is polarized. Polarity markings: 1) Dimple/Groove marking, 2) One point differs in size/shape from the other two/three points.

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.6.2 SOP and QFP Package

6.3 QFN Package Type

This type of package is polarized. Polarity markings: 1) One point differs in size/shape from the other two points, 2) Slanted edge marking, 3) Symbol marking (horizontal bar/“+” sign/dot).

Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.6.3 QFN Package with Polarity

7. Ball Grid Array (BGA)

  • Component polarity: Dimple/Groove marking/Circle marking;
  • PCB polarity: Circle/Dot/Letter “1 or A”/Slanted marking.
  • Component polarity point corresponds to the PCB polarity point.
Component Misalignment: Circuit Board Issues and Solutions
▲ Figure 2.7.1 BGA Package Chip

Component Misalignment: Circuit Board Issues and Solutions

Component Misalignment: Circuit Board Issues and Solutions

Some Screenshots from Electronic Books

Component Misalignment: Circuit Board Issues and Solutions

【Complete Set of Hardware Learning Materials Collection】

Component Misalignment: Circuit Board Issues and Solutions

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