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What is the difference between PCB and PCBA?

As an SMT processing employee, have you ever wondered what the difference is between PCB and PCBA, two abbreviations that look similar? The difference between PCB and PCBA is that in the electronic manufacturing industry, PCB and PCBA are two commonly mentioned terms.

Although they are all related to circuit boards, there are significant differences in functionality, manufacturing process, and final product form.

Below, we will explore in detail the differences between PCB and PCBA.

1. PCB - Printed Circuit Board

Definition: The acronym for Printed Circuit Board in English. It is mainly a carrier for electronic components, connecting various electronic components in the circuit through conductive copper foil and insulating materials (such as epoxy resin) to establish a complete electrical connection. PCB is the "installation carrier" for electronic components (such as green/black circuit boards in mobile phones and computers).

Core function: Connect various components to achieve stable transmission of current signals.

PCB is the cornerstone of all electronic products. Its manufacturing process does not involve the installation of components, and the main steps include:

Design: Design a circuit layout diagram based on the circuit schematic.

Plate making: Transfer the designed drawings onto the copper-clad board.

Etching: Using chemical solution to corrode unwanted copper foil, leaving only the designed circuit.

Drilling: Drilling through holes or blind holes in areas where components or interlayer conductivity need to be installed.

Electroplating: Metallizing the wall of the hole to make different layers of circuits conductive.

Compression: For multi-layer boards, multiple core boards are pressed together to form a whole.

Solder mask: Apply green (or other colored) solder mask paint to protect the circuit and prevent short circuits during welding.

Screen printing: Printing white text such as component part numbers and parameters to facilitate subsequent assembly and maintenance.

So far, a bare PCB board has been produced. It cannot do any electronic work yet.

2. PCBA - Printed Circuit Board Assembly

Definition: The abbreviation for Printed Circuit Board Assembly, which stands for Printed Circuit Board Assembly in Chinese, refers to the installation of electronic components (such as resistors, capacitors, chips, etc.) on a PCB (Printed Circuit Board) and the formation of a complete circuit board assembly with specific functions through soldering or connection processes.

Core difference: PCB is an "empty board" and PCBA is a "finished board with parts installed".

PCBA is a complex assembly process based on PCB, which precisely installs the required electronic components into their corresponding positions on the PCB and forms reliable electrical connections. The main processes include:

SMT (Surface Mount Technology) SMT:

Solder paste printing: solder paste is leaked onto the solder pads of the PCB through a steel mesh.

Component mounting: Use a surface mount machine to accurately mount small surface mount components (such as chips, small resistors, and capacitors) onto solder paste.

Reflow soldering: The PCB with the components attached is passed through a reflow soldering furnace, where the solder paste is melted and cooled at high temperature, and the components are firmly soldered onto the board.

LDIP (Dual Inline Package) plugin: For large volume components (such as capacitors and connectors) that are not suitable for surface mount, they need to be manually or machine inserted into the through holes of the PCB.

Wave soldering: Use melted tin waves to solder the pins of the plug-in onto the board at the bottom of the board.

Testing and Inspection:

LAOI (Automatic Optical Inspection): Check for welding defects such as short circuits, missing parts, offsets, etc.

LICT (online testing): Test whether the electrical connections of the circuit board are correct.

LFCT (functional testing): Simulate the working environment of the whole machine to test whether the overall function of the PCBA is normal.

Only after all the assembly and testing steps mentioned above, can a fully functional PCBA be obtained, which can be installed into the casing and become electronic products such as smartphones, computers, televisions, etc. that we use in our daily lives.

summary

PCB is the foundation, PCBA is the result.

PCB comes before PCBA.

PCB manufacturing belongs to the "printing" industry, while PCBA assembly belongs to the "electronic manufacturing" industry.