IPC-2223-Design-Standard-for-Flex-and-Rigid-Flex-Circuits.pdf - 第11页
Minimum Bend Radius Capabilities A key element to a successful design is ensuring the ex construction meets the bend requirements. The bend capability of a ex section is dependent upon the materials and material thickn…
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DEFINE AIR GAP CONSTRUCTION
REQUIREMENTS IN THE FABRICATION
DRAWING NOTES AND MATERIAL STACKUP
Examples of both air gap and non-air gap constructions.
Minimum Bend Radius Capabilities
A key element to a successful design is ensuring the ex construction
meets the bend requirements. The bend capability of a ex section is
dependent upon the materials and material thicknesses used and cannot
be impacted by the manufacturing process. IPC 2223 provides minimum
bend recommendations for both static “one-time” or “bend to t” as well as
“dynamic” or “innite bend” applications. These dier signicantly in the
allowable layer count, minimum bend capability, and the allowable copper
type - either electrodeposited or rolled annealed. The minimum bend
radius can be calculated or is commonly dened as a multiplier of the ex
thickness. Bend to t applications vary from 6x to 20x or greater depending
upon layer count. Dynamic applications are typically 100x with a maximum
of two layers.
IPC 2223 also allows, with specic guidelines, for a ex to be bent and
creased with a zero bend radius. This is limited to very thin one and two
layer constructions with the added stipulation that once the ex is creased
it cannot be unfolded. A PSA, pressure sensitive adhesive/doubled sided
tape, is often added in the fold area to permanently ax the ex and ensure
that it is not inadvertently unfolded.
Many designs call out for a specic number of bend cycles. For these
applications that fall between IPC’s guidelines, we recommend getting
material and construction input from the ex circuit supplier and cycle
testing the ex circuits as part of the design approval process.
Important Element
#5
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MEETING THE DESIGN BEND REQUIREMENTS
RELIABLY IS A KEY ELEMENT TO A
SUCCESSFUL DESIGN. EVEN IF THE PART IS
BEING BENT ONE TIME ONLY.
Side view cutaway of a bent flex circuit and the impact on specific layers.