PCB Technical - PCB additive process

The addition process for printed circuit boards (PCBs) is an important step in ensuring board performance and quality. The Internet era has broken the traditional marketing model, and a large number of resources have been gathered together to the greatest extent through the Internet, which has also accelerated the development speed of FPC flexible circuit boards, and then as the development speed accelerates, environmental problems will continue to appear in PCB factories. In front of him. However, with the development of the Internet, environmental protection and environmental informatization have also been developed by leaps and bounds. Environmental information data centers and green electronic procurement are gradually being applied to the actual production and operation fields.

The method of selectively depositing conductive metal on the surface of an insulating substrate to form a conductive pattern is called an additive method.

1.Advantages of the additive method

The printed board is manufactured using an additive process,and its advantages are as follows.

(1) Because the additive method avoids a large amount of etching of copper,and the resulting large amount of etching solution processing costs,the production cost of the printed board is greatly reduced.

(2) The additive process is reduced by about 1/3 compared with the subtractive process,which simplifies the production process and improves the production efficiency.In particular,it avoids the vicious circle that the higher the product grade, the more complicated the process.

(3) The additive process can achieve flush wires and flush surfaces,so that SMT and other high-precision printed boards can be manufactured.

(4) In the additive process, due to the simultaneous electroless copper plating of the hole wall and the wire,the thickness of the copper plating layer of the conductive pattern on the hole wall and the board surface is uniform, which improves the reliability of the metallized hole and can also meet the requirements of high thickness Diameter ratio printed boards, copper plating requirements in small holes.

2.Classification of additive methods

The additive manufacturing process of printed boards can be divided into the following three categories.

(1) Full Additive Process (Full Additive Process) is an additive process that only uses electroless copper to form conductive patterns.Take the CC-4 method as an example: drilling, imaging, viscosity-increasing treatment (negative phase), electroless copper plating, and resist removal.The process uses a catalytic laminate as the substrate.

(2) Semi-additive process (Semi-additive Process) On the surface of the insulating substrate,the metal is chemically deposited, combined with electroplating and etching, or the three are combined with an additive process to form conductive patterns. The process flow is: drilling, catalytic treatment and viscosity increasing treatment,electroless copper plating, imaging (electroplating resist),patterned copper electroplating (negative phase), resist removal, and differential etching. The substrate used in the manufacture is a common laminate.

(3) Partial Additive Process (Partial Additive Process) is to use the additive method to manufacture printed boards on the catalytic copper clad laminate. Process flow: imaging (anti-etching), etching copper (normal phase), removing the resist layer, coating the entire plate with electroplating resist, drilling a hole, electroless copper plating in the hole, and removing the electroplating resist. 

Different types of printed circuit boards (PCBs) have their own unique additive process requirements due to their different structures and uses.

1.Single-sided PCB

Single-sided PCB has only one layer of conductive graphics, usually used for simple electrical or electronic products.Its manufacturing process is relatively simple, low cost.

Process requirements.

Component Layout: Components can only be mounted on one side, limiting the flexibility of the layout.

Thickness Requirements: PCB bezels need to be at least 0.15mm (6mil) thick to meet production requirements.

Priority: The design should follow the priority order of Single Side SMT > Double Side SMT > Single Side Insertion.

2.Double-sided PCB

Double-sided PCBs have conductive layers on both sides and are suitable for complex devices that require higher wiring density.

Process Requirements

Finished product certification:Double-sided PCBs must meet domestic and international certification requirements, such as RoHS.

Soldering Requirements:Use high quality solder to ensure the quality of the solder joints, and strictly control the soldering position during the soldering process.

Test steps:After the board is formed,electrical and mechanical performance tests are required to ensure that the PCB functions properly before delivery.

3.Multilayer PCB

Multilayer PCB has more than two conductive layers, suitable for high-density,high-performance applications,such as computers and communications equipment.

Process Requirements

Lamination process: The production of multilayers involves the stacking of layers, ensuring symmetry and uniformity of all layers to avoid warpage due to thermal stress.

Specific Material Requirements: A combination of semi-cured sheet (PP) and thin copper-clad laminate (Core) is used to form the circuit.

Special Manufacturing Steps: Multilayer PCBs typically require about 200 processing steps, including circuit design, lamination, and drilling.

4.High Frequency PCBs

High-frequency PCBs are suitable for high-frequency signal transmission and are commonly used in telecommunications, automotive and aerospace applications.

Process Requirements

Performance Requirements: HF PCB substrates need to have good dielectric constant and dielectric loss characteristics to ensure the quality of high frequency signal transmission.

Microvia Technology: HF PCBs often use microblind and buried vias to meet high density wiring requirements.

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