In the PCB manufacturing process, the most commonly focused aspects are typically "key process steps" such as etching accuracy, lamination stability, conductivity quality, and AOI inspection. However, a "minor player"—the release film—often goes overlooked. In fact, although the release film does not directly participate in circuit conduction, it plays an indispensable role in multiple stages, including dry film lamination, pattern transfer, lamination alignment, and finished product protection. If this film is not chosen properly, it may lead to issues such as film blistering, pattern misalignment, lamination delamination, surface scratches, and ultimately result in batch rework and yield reduction. So, how exactly does a "good" roll of release film help improve PCB manufacturing yield?

In the manufacturing process of multilayer PCBs (especially 6-layer, 8-layer, and HDI boards), the lamination process is crucial. To prevent adhesion and contamination, manufacturers typically incorporate isolation release films between layers. At this stage, the temperature resistance, dimensional stability, and peel performance of the release film directly determine the lamination outcome.

Key capabilities of high-quality release film:  

Strong high-temperature resistance (≥180°C): No warping, shrinkage, or adhesive overflow during thermal pressing.  

High dimensional stability: Prevents layer misalignment and uneven board thickness.  

Clean release: Smooth detachment after lamination and cooling, with no residual adhesive or transfer marks.  

High surface flatness: No layer marks or trapped air after lamination.

Defective release film can lead to: bonding air bubbles, delamination, edge lifting, resin overflow contaminating copper surfaces, compromising interlayer adhesion and final thickness uniformity, severely reducing the yield rate of multi-layer boards.

Part of the PCB process (such as FPC, Coverlay bonding, EMI conductive film die-cutting) requires the use of release film as a temporary carrier. The accuracy of die-cutting, the smoothness of waste discharge, and the residual situation of adhesive materials are closely related to the performance of the release film.

The function of high-quality die-cutting release film: moderate stiffness, strong tear resistance: supports die-cutting without deformation or breakage; Uniform peeling force to prevent wire drawing: improve the cleanliness of graphic edges; Consistent film thickness (error ≤± 2 μ m): ensures consistent die-cutting depth and avoids tool pressure loss; High cleanliness supports precise bonding: avoiding particle contamination of the adhesive layer or circuit surface.

Common issues with low-quality release films include material dropping, misalignment, and excessive residue during die-cutting; Curling of film, misalignment of adhesion; Difficulty in waste disposal affects efficiency. The result is a batch of products with unqualified structure, rough edges, or unstable functional layers, leading to a significant decrease in yield.

PCB finished products are often affected by mechanical impact, surface friction, and environmental pollution during subsequent processes such as testing, cutting, labeling, packaging, and transportation. The high-quality release film acts as a "temporary protective film" at this time, effectively maintaining key areas such as copper surfaces, solder pads, and solder mask layers.

Good protective release film performance: light peeling, no residual adhesive: after tearing off the film, it does not affect the pad mounting or subsequent recognition; Anti static treatment (surface static<100V): Avoid adsorbing dust; Good friction and chemical resistance: prevents surface damage, oxidation, and discoloration during transportation; Customizable printing or positioning function: helps with SMT/SMT visual recognition. If the inferior film cannot be peeled clean and the residue is obvious, it will directly affect the quality of customer installation, increase manual cleaning costs, and even lead to customer returns.