1. Laminated structure
2. Production process
Flexible board cutting → drilling → black hole VCP → circuit etching → AOI scanning → pressing cover film → lamination → laser drilling → Immersion copper and pattern plating → Outer layer etching (alkaline etching) → AOI scanning → Solder mask and characters →
Immersion gold → Opening and routing → Mechanical depth control → Electrical test → rigid board routing → flexible board routing → FQC → packaging
3. Manufacturing difficulties
Double lamination, PP filling process of the buried hole, laser blind hole, electroplating hole filling, and laser controlled depth opening.
4. Application areas
The rigid flex boards are used on TWS Bluetooth headsets. It is a combination of the rigid and flexible structure of HDI. Since the current high-end TWS Bluetooth headsets have integrated active noise reduction functions, the traditional through-hole structure cannot meet this function (or the effect is not good), so more and more TWS headset manufacturers choose to use rigid flex boards of HDI structure.