FLEX AND RIGID-FLEX LAYER STACKUP TYPES

There are a number of standard stackups available for flex and rigid-flex circuits, referred to as Types. These are summarized below.

Type 1 – Single Layer

Single-sided flexible wiring containing one conductive layer and one or two polyimide outer cover layers.

One conductive layer, either laminated between two insulating layers or uncovered on one side.
Access holes to conductors can be on either one or both sides.
No plating in component holes.
Components, stiffeners, pins and connectors can be used.
Suitable for static and dynamic flex applications.

A Type 1 flex structure with 2 cover layers, access holes on both sides and no plating in the in the component holes.

Type 2 – Double Layer

Double-sided flexible printed wiring containing two conductive layers with plated through holes, with or without stiffeners.

Two conductive layers with an insulating layer between; outer layers can have covers or exposed pads.
Plated through-holes provide connection between layers.
Access holes or exposed pads without covers can be on either or both sides; vias can be covered on both sides.
Components, stiffeners, pins and connectors can be used.
Suitable for static and dynamic flex applications.

A Type 2 flex structure with access holes on both sides and plated through holes.

Type 3 – Multilayer

Multilayer flexible printed wiring containing three or more conductive layers with plated-through holes, with or without stiffeners.

Three or more flexible conductive layers with flexible insulating layers between each one; outer layers can have covers or exposed pads.
Plated through-holes provide connection between layers.
Access holes or exposed pads without covers can be on either or both sides.
Vias can be blind or buried.
Components, stiffeners, pins and connectors can be used.
Typically used for static flex applications.

A Type 3 flex structure with access holes on both sides and plated through holes.

Type 4 – Multilayer Rigid-Flex

Multilayer rigid and flexible material combinations (Rigid-Flex) containing three or more conductive layers with plated-through holes. Rigid-flex has conductors on the rigid layers, which differentiates it from multilayer circuits with stiffeners.

Two or more conductive layers with either flexible or rigid insulation material as insulators between each one; outer layers can have covers or exposed pads.
Plated through-holes extend through both rigid and flexible layers (apart from blind and buried vias).
Access holes or exposed pads without covers can be on either or both sides.
Vias or interconnects can be fully covered for maximum insulation.
Components, stiffeners, pins, connectors, heat sinks, and mounting brackets can be used.