What are the differences between FPC, PCB and SMT?

PCB (Printed Circuie Board) is the abbreviation of printed circuit board. For example, the green board on the computer motherboard we see is PCB

FPC (Flexible Printed Circuit[^1]) is a flexible circuit board, a flexible printed circuit board, a flexible circuit board, abbreviated as soft board. For example, the circuit board with yellow wiring on the mobile phone screen we see is FPC.

SMT (abbreviation of Surface Mounted Technology[^2]) is the most popular technology and process in the current electronic assembly industry.

Simply put, PCB is generally called hard board and FPC is called soft board. PCB FPC can be simply said to be a material, and I personally understand SMT as a production process. The process is generally screen printing (or dispensing)--> mounting--> (curing)--> reflow soldering--> cleaning--> detection--> rework.

The following are some knowledge points about SMT workshops:

Workshop environment control

a. Temperature and humidity standards

1. Temperature: 25±3℃

2. Humidity: 30-60% RH

3. Parts drying box: humidity 30% indicates moisture

b. PCB storage requirements

1. Purpose of vacuum packaging: dust and moisture-proof

c. Environmental sensitivity control

1. After IC unpacking, humidity card > 30% indicates moisture
2. Humidity card should show blue when temperature and humidity sensitive parts are unpacked

Production materials and tools

a. Solder paste printing materials

1. Necessary materials: solder paste, steel plate, scraper, wiping paper, dust-free paper, cleaning agent, stirring knife, gloves

b. Steel plate technology

1. Production method: etching, laser, electroforming

2. Material: stainless steel

3. Thickness: 0.15mm or 0.12mm

4. Opening principle: 4μm smaller than PCB PAD Anti-tin ball

c. Solder paste ingredients

1. Main ingredients: tin powder (Sn/Pb 63/37 or lead-free Sn/Ag/Cu), flux
2. Ratio: volume ratio of tin powder: flux ≈1:1, weight ratio ≈9:1

Solder paste application technology

a. Usage specification

1. Access principle: first in, first out
2. Unsealing process: reheating, stirring (automatic mixer can handle synchronously)

b. Key parameters

1. Eutectic point: Sn63Pb37 melting point 183℃, lead-free Sn/Ag/Cu melting point 217℃
2. Viscosity time: market solder paste is usually only 4 hours

c. Adverse effects

1. Consequences of not reheating: solder beads are easily generated after PCBA reflow

SMT technology foundation

a. Core concepts

1. SMT full name: Surface Mount Technology
2. ESD full name: Electro-static Discharge

b. Equipment program composition

1. Five parts: PCB data, Mark data, Feeder data, Nozzle data, Part data

c. Process positioning method

1. PCB positioning: vacuum, mechanical hole, double-side clamp, board edge positioning

Static electricity protection

a. Generation and hazards of static electricity

1. Generation mode: friction, separation, induction, static electricity conduction
2. Impact: ESD failure, static electricity pollution[^3]

b. Elimination principle

1. Three methods: static electricity neutralization, grounding, shielding

Quality management system

a. Policies and principles

1. Quality policy: comprehensive quality control, zero defect goal
2. Three no policies: do not accept/manufacture/discharge defective products

b. Inspection and techniques

1. Seven QC techniques: fishbone diagram (4M1H: people, machines, materials, methods, environment)
2. Inspection methods: visual, X-ray, AOI, ICT, FT

c. Process control

1. CPK: actual process capability
2. Welding adhesion: dihedral angle > 90° means no adhesion

Conclusion

In summary, mastering these SMT workshop essentials ensures smooth operations, quality products, and compliance with industry standards for efficient electronic assembly.

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[^1]: Discover the benefits of Flexible Printed Circuits and how they are revolutionizing electronic device design and functionality.
[^2]: Explore this link to understand the significance and applications of Surface Mounted Technology in modern electronics manufacturing.
[^3]: Understanding static electricity pollution is crucial for preventing ESD failures in electronic devices. Explore this link for detailed insights.