84N is recommended for etched areas in copper layers and clearance holes, and the high resin flow is designed to flow readily into the holes. The actual pressed thickness of the glass plus resin that will be left after flow-out into the holes may vary depending on the density of holes to be filled. It is recommended that to ensure maximum effectiveness of the hole-filling process, at least two plies of 84N be used on each side of the material to be filled (more may be needed for thicker systems), backed up by a single ply of standard 85N1080 or 106 to
serve as a hydraulic medium to drive the filled resin into clear via holes. When using the 84N as prepreg with etched inner layers the pressed thickness depends on the amount and thickness of copper on inner layers. The Ho value is the theoretical thickness if there were no flow or fill of inner layer copper.

NOTE: The 84N0675HF grade has reduced resin content to provide a lower pressed thickness. Customer should use the 84N0680HF grade for most applications as the lower resin grade may be marginal in hole fill for many applications.

Lamination Cycle:

1. Pre-vacuum for 30 - 45 minutes
2. Control the heat rise to 4.5°C - 6.5°C (8°F - 12°F) per minute between 100°C and 150°C (210°F and 300°F). Vacuum lamination is preferred. Start point vacuum lamination pressures are shown in the table below.
3. Set cure temperature at 218˚C (425˚F). Start cure time when product temperature > 213˚ C (415˚F)
4. Cure time at temperature = 120 minutes
5. Cool down under pressure at ≤ 5°C/min (10°F/min)

• Drill at 350 SFM. Undercut bits are recommended for vias 0.0 18” (0.45mm) and smaller
• De-smear using alkaline permanganate or plasma with settings appropriate for polyimide; plasma is preferred for positive etchback.
• Conventional plating processes are compatible with 84N
• Standard profiling parameters may be used; chip breaker style router bits are not recommended
• Bake for 1 - 2 hours at 250°F (121°C) prior to solder to reflow of HASL