PCBMASTER takes you through the principles and processes of PCB pressing
I. Principles of PCB Lamination
PCB lamination adheres and solidifies multiple layers of boards through high temperature and high pressure to form an integrated multi - layer board. The key material is the prepreg (PP film), which is composed of epoxy resin and glass fiber. Under high temperature and high pressure, the resin softens and flows, filling the gaps to form a uniform bonding layer. And through the diffusion and penetration of macromolecular chains, firm chemical bonding is achieved.
Structural characteristics of the PP film：
structure type | content | explain |
molecular structure
|
Isotactic polypropylene (lsotactic PP) | Methyl groups are aligned consistently along the direction of the polymer's main chain, creating a highly crystalline structure that endows it with high mechanical strength and thermal stability. |
|
syndiotactic polypropylene (Syndiotactic PP) | Methyl groups are arranged alternately, resulting in a lower degree of crystallinity and properties between those of isotactic and atactic polymers. |
|
Atactic Polypropylene (APP) | The methyl groups are arranged randomly, forming an amorphous structure. This kind of structure typically shows rubber - like characteristics, featuring good flexibility but relatively low strength. |
physical structure |
crystalline region & amorphous region | The PP film is composed of crystalline areas and non - crystalline areas. The crystalline areas offer mechanical strength and thermal stability, whereas the non - crystalline areas confer flexibility. |
microstructure |
Spherulites | Spherulites are common microstructures in PP film. Their size and distribution affect the film's transparency and physical properties. |
Processing structure (e.g. BOPP) |
Biaxially Oriented Polypropylene | After biaxial stretching treatment, the PP film is stretched simultaneously in the machine direction and the transverse direction, and the molecular chains are oriented along the stretching direction, thereby improving the strength and transparency. |
II. Process of PCB Lamination
The process of PCB lamination mainly consists of the following key steps:
1. Material Preparation
- Core Board: It provides mechanical support and serves as the foundation of multi - layer PCBs.
- PP Material: It plays an adhesive role and is a crucial material for connecting various layers.
- Copper Foil: It is used to form the outer - layer circuit and needs to have good electrical conductivity and stability.
2. Stacking and Positioning
- Stack the inner - layer core boards, PP materials, and outer - layer copper foils in sequence according to the design requirements.
- Use hot - melting or riveting methods for precise positioning to ensure alignment among all layers.
3. Lamination and Heating
- Place the stacked boards into the laminator.
- Under the conditions of high temperature and high pressure, the resin in the PP starts to soften and flow, filling the gaps between the core boards and achieving a tight bond between all layers.
Illustration of the Internal Structure of the Laminator
name of parts | functional description |
Hot Plate | The upper and lower heating plates are used to provide uniform heat, causing the prepreg to melt and bond tightly with the copper foil. |
pressure unit | It includes a hydraulic cylinder, a hydraulic pump and a pressure sensor, which are used to apply precise pressure to the upper die plate. |
vacuum system | A vacuum pump is used to evacuate the air between the materials, ensuring that there are no air bubbles during the pressing process. |
control system | It includes a PLC controller, a human - machine interface and sensors, which are used to precisely control the temperature, pressure and time.
|
workbench | It is used to fix the materials to be pressed, ensuring their stability during the pressing process.
|
cooling system | It is used to rapidly cool the materials after the pressing is completed to ensure the molding effect. |
4.Cooling and Curing
- After the pressing is completed, cool the board to room temperature to allow the resin to cure and form a stable multi - layer structure.
- During the cooling process, the temperature and pressure need to be strictly controlled to avoid warping or delamination caused by uneven cooling.
5. Post - processing
- Inspection: Conduct dimensional inspection, circuit connection testing, and appearance inspection.
- Trimming: Trim and polish the board to ensure that its dimensions meet the design requirements.
III. Importance of the Pressing Process
1. Enhancing Structural Strength and Stability
- The pressing process tightly bonds each layer together under high temperature and high pressure, enhancing the mechanical strength and stability of the multi - layer board.
- It prevents warping and deformation, ensuring the reliability of the circuit board during subsequent assembly and use.
2. Affecting Electrical Performance and Impedance Characteristics
- The lamination process directly affects the geometric structure and characteristic impedance of the signal transmission lines.
- A reasonable pressing process can ensure signal integrity and transmission quality, avoiding signal attenuation and distortion.
3. Related to Thermal Management and Heat Dissipation Performance
- The materials selected in the lamination process and the compactness after lamination affect the thermal conductivity of the PCB.
- A high - quality lamination process can provide better thermal conductivity, ensuring that heat is effectively transferred from the heat - generating components to the PCB surface.
In the field of PCB production, PCBMASTER has always been steadfast in its pursuit of quality. We continuously innovate process technologies and strictly control every production stage.
PCBMASTER boast strong production capabilities. We can produce high - layer FR4 PCBs with the number of layers ranging from 1 to 64. The HDI level can reach from 1 to 7 levels or even any level. With such capabilities, we are committed to providing our customers with high - quality and high - performance PCB products to meet the diverse needs of different industries and fields.