Professional PCB Multilayer Board Pressing Process Description
Sequential Lamination
Sequential lamination is a specialized pressing process for multilayer PCB boards that involves multiple stages of pressing to increase the board’s level gradually. This method utilizes blind hole or buried hole techniques to achieve interconnection features, saving surface through-holes and allowing for more board space for wiring and SMD mounting.
Starvation
In the circuit board industry, “starvation” refers to the Resin Starvation issue in multilayer board pressing. This occurs when there is poor resin flow or incorrect pressing conditions, resulting in a partial lack of glue in the completed board.
Swimming
Swimming is the slight sliding displacement of the inner board surface circuit during multilayer board pressing, often caused by the Gel Time of the film used. Using films with shorter gel times has helped reduce this issue significantly in the industry.
Telegraphing
To prevent glue overflow during early lamination, a heat-resistant film like Tedlar is added to the copper foil or thin substrate stacked with loose materials. However, if the film used for the outer layer board is thin and the copper foil is only 0.5 oz, the inner layer board’s circuit pattern may transfer to the release paper under high pressure, resulting in telegraphing.
Vacuum Lamination
Vacuum lamination is commonly used in the pressing and bonding of dry films in the circuit board industry. It involves vacuum pressing multilayer boards using either the vacuum frame type or the vacuum chamber type (Autoclave). The vacuum frame type, utilizing a pumping method, is more popular due to its simplicity and lower cost.
Wrinkle
Wrinkle occurs when there is excessive 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.
Zero Centering
Zero centering involves stacking and registering the bulk materials of a multilayer board using special tool notches with aligning pins. These notches are strategically placed to ensure stability in the central plate area and prevent misalignment, a practice widely adopted in American Multiline products.
