Professional PCB Multilayer Board Pressing Process Description
19. Sequential Lamination
Sequential lamination refers to the special pressing process of multilayer PCB boards, which is not completed in one step. Instead, it is divided into multiple stages and gradually pressed to increase its level. The blind hole or buried hole method is utilized to achieve the “interconnection” features. This method saves all the through-holes that would otherwise need to be drilled on the surface of the board, allowing for more board space to accommodate additional wiring and mounting SMDs. However, this elongates the manufacturing process.
20. Starvation
In the circuit board industry, the term “starvation” is commonly used to describe the Resin Starvation issue in multilayer board pressing. This occurs when there is poor resin flow or an improper combination of pressing conditions, resulting in a partial lack of glue in the board after the multilayer board is completed.
21. Swimming
Swimming refers to a slight sliding displacement of the inner board surface circuit during the pressing of multilayer boards. This can often happen due to the “Gel Time” of the film used. The industry tends to use films with shorter gel times nowadays, reducing this issue significantly.
22. Telegraphing
To prevent glue overflow during the early lamination of multilayer boards, a heat-resistant film like Tedlar is added to the copper foil or thin substrate that has been stacked with loose materials. This film helps in demoulding or separating after pressing. However, in cases where the film used for the outer layer board is thin and the copper foil is only 0.5 oz, the circuit pattern of the inner layer board may transfer to the release paper under high pressure. If this release paper is reused on a batch of boards, the original pattern may be embossed on the copper surface of the new board, a phenomenon known as Telegraphing.
23. Vacuum Lamination
Vacuum lamination is a term commonly associated with the pressing of multilayer boards and the bonding of dry films in the circuit board industry. It involves vacuum pressing of multilayer boards using either the vacuum frame type or the vacuum chamber type (Autoclave). The former, employing the original hydraulic press and a “pumping method,” is more popular due to its simpler equipment, lower price, and ease of operation. The latter, utilizing high temperature and high-pressure carbon dioxide in an “air pressure method,” is more complex in terms of equipment and operation, making it less widely adopted.
24. Wrinkle
Wrinkle refers to the occurrence of a large amount of glue flow during pressing, leading to a slight reduction in the strength and hardness of the outer layer, resulting in wrinkles or creases. This issue is often observed with 0.5oz copper foil and can also be seen in other fields.
25. Zero Centering
When stacking and registering the bulk materials of a multilayer board, a special tool notch is used. These notches have arc-shaped short sides and long straight sides that match the insertion of aligning pins (Flated Round Pin). These notches are typically placed in the center of the four sides of the bulk material, with one of the long side notches deliberately offset to prevent misalignment. This allows the plates to expand outwards at high temperatures and retract when cooled, ensuring stability in the central plate area and avoiding tensile stress between the fixing hole and the pin, known as center-invariant superimposition. This practice is widely adopted in American Multiline products.
19. Sequential Lamination
Sequential lamination refers to the special pressing process of multilayer PCB boards, which is not completed in one step. Instead, it is divided into multiple stages and gradually pressed to increase its level. The blind hole or buried hole method is utilized to achieve the “interconnection” features. This method saves all the through-holes that would otherwise need to be drilled on the surface of the board, allowing for more board space to accommodate additional wiring and mounting SMDs. However, this elongates the manufacturing process.
20. Starvation
In the circuit board industry, the term “starvation” is commonly used to describe the Resin Starvation issue in multilayer board pressing. This occurs when there is poor resin flow or an improper combination of pressing conditions, resulting in a partial lack of glue in the board after the multilayer board is completed.
21. Swimming
Swimming refers to a slight sliding displacement of the inner board surface circuit during the pressing of multilayer boards. This can often happen due to the “Gel Time” of the film used. The industry tends to use films with shorter gel times nowadays, reducing this issue significantly.
22. Telegraphing
To prevent glue overflow during the early lamination of multilayer boards, a heat-resistant film like Tedlar is added to the copper foil or thin substrate that has been stacked with loose materials. This film helps in demoulding or separating after pressing. However, in cases where the film used for the outer layer board is thin and the copper foil is only 0.5 oz, the circuit pattern of the inner layer board may transfer to the release paper under high pressure. If this release paper is reused on a batch of boards, the original pattern may be embossed on the copper surface of the new board, a phenomenon known as Telegraphing.
23. Vacuum Lamination
Vacuum lamination is a term commonly associated with the pressing of multilayer boards and the bonding of dry films in the circuit board industry. It involves vacuum pressing of multilayer boards using either the vacuum frame type or the vacuum chamber type (Autoclave). The former, employing the original hydraulic press and a “pumping method,” is more popular due to its simpler equipment, lower price, and ease of operation. The latter, utilizing high temperature and high-pressure carbon dioxide in an “air pressure method,” is more complex in terms of equipment and operation, making it less widely adopted.
24. Wrinkle
Wrinkle refers to the occurrence of a large amount of glue flow during pressing, leading to a slight reduction in the strength and hardness of the outer layer, resulting in wrinkles or creases. This issue is often observed with 0.5oz copper foil and can also be seen in other fields.
25. Zero Centering
When stacking and registering the bulk materials of a multilayer board, a special tool notch is used. These notches have arc-shaped short sides and long straight sides that match the insertion of aligning pins (Flated Round Pin). These notches are typically placed in the center of the four sides of the bulk material, with one of the long side notches deliberately offset to prevent misalignment. This allows the plates to expand outwards at high temperatures and retract when cooled, ensuring stability in the central plate area and avoiding tensile stress between the fixing hole and the pin, known as center-invariant superimposition. This practice is widely adopted in American Multiline products.
