Flex Circuits Overview

APPLICATIONS

Static v. Flex to Fit:

• Static; the flex circuit is installed flat between two or more stationary parts.

• Flex to fit; the flex circuit is bent or molded into position then installed between two or more stationary part.

Dynamic:

• The flex circuit is installed between one or more moving parts.

Bend radius:

• Single-sided flex 6X circuit thickness.
• Double-sided flex 10X circuit thickness.
• Multilayer flex 10-15X circuit thickness.
• Dynamic Application 20X circuit thickness.

FLEXIBLE CIRCUIT MATERIALS

Pyralux LF Military/Commercial Adhesive Based.

IPC CERTIFIED CLASS 3

FC 241/1 CLADS

FC 232/1 CS/BP

FC 232/18 ADHESIVE

Pyralux FR Commercial Adhesive Based.

IPC CERTIFIED CLASS 2

UL VTMO

FC 241/1 CLADS

FC 232/1 CS/BP

FC 232/18 ADHESIVE

Pyralux AP Military/Commercial Adhesiveless.

IPC CERTIFIED CLASS 3

FC 241/11 CLADS

FLEX CONSTRUCTIONS

Single sided

Dual access

Double sided

Multilayer

Rigid-Flex

BUILDS

Adhesive:
Adhesive systems are easy to use, but have limitations. The major drawback is hole wall cracks due to excessive Z-axis expansion. Drill size is the driving factor in whether adhesive is used or not.

No-flow prepregs:
No-flow or sometimes called low-flow pre-pregs are harder to process, but work best in flex-rigid applications. Z-axis expansion is close to that of kapton.

Bookbinding:
Bookbinding is used when a flex-rigid or multilayer flex has a section that needs to bend at a tight radius.

PLATING FINISHES

Copper plate, pattern: Used for static and flex to fit applications.
Copper plate, pads (button plate): Used for dynamic applications.
Electroless Ni-Au (ENIG): Used in coverlay openings.
Hot air level (HAL): Used in coverlay openings
Tin Immersion: Used in coverlay openings.
Silver Immersion: Used in coverlay openings.
Both Tin and Silver immersion oxidize easy, and can cause problems.

FINAL ROUT

Ziff connectors: With a tolerance of +-.002 will need laser rout at that location.
Array: If the part is going to be arrayed we need to know at the quote stage.
Edge to feature: With a tolerance of +-.005 will need laser rout.