Flex and Rigid Flex PCB Design Principles

The developer is typically under pressure to release the paperwork and obtain the flexible circuit right into production. There is, however, a lot in jeopardy. Setting up for medium-to-high quantity PCB manufacturing needs considerable physical and monetary resources. To avoid prospective warmth from monitoring, the developer needs to demand PCB prototyping the product and a thorough design review before release.

DFM Review Criteria

The key references for examining the Flex PCB are tooling openings and fiducial targets. Non-plated tooling openings are commonly used for preserving the placement of the circuit throughout singulation and, when backed with or part of a rigid area, PCB assembly processing. Fiducial functions ought to be equipped in each circuit section or local termination location to provide a monotonous ‘datum’ referral for a lot more specific element positioning. The maximum fiducial is a solid loaded 0.25 to 0.5 mm (.010″ to.020″) diameter circle. Cover layer material should give enough clearance to ensure that it does not overlap into the fiducial target features during the cover layer-to-base circuit lamination process.

Making use of fiducial functions is an usual method for:
– Solder stencil x, y and theta positioning
– Specific surface place part placement
– Decreasing the results of variable material shrinking problems
– Payment for any random distortions in flex PCB materials

Comprehensive documents is essential. The intent is to offer the fabricator with a breakdown and summary of the materials defined for the flex PCB circuit building, materials stack-up, reinforced/stiffened locations, important thickness areas, and to define a solder-compatible surface area coating for all element land pattern functions. For the extra complex multilayer and Rigid Flex PCBapplications include cross-sectional views. Essential bend or radius areas need to be identified with recommendation measurements and it will certainly be helpful to equip separate views revealing a mounted flex configuration.

PCB Assembly paperwork will consist of a bill of material, approved PCB provider listing, element reference designators and any type of special demands. Create clear, thorough illustrations and PCB Assembly guidelines. This document must consist of element lays out and general places. The CAD documents will certainly provide precise element X-Y coordinates and alignment information required for assembly processing. All SMT devices are lined up and positioned onto their corresponding land patterns utilizing the body facility as a referral factor for positioning collaborates. The fiducial targets explained above will certainly help in establishing these specific X-Y coordinates for solder printing, element placement and alignment. With adaptability comes integral dimensional instability about hardboards or solid metal items. When multiple element installing websites are separated by extreme range it is suggested that numerous fiducial functions be supplied. Making use of several datum functions is a common strategy for reducing or getting rid of the impacts of variable shrinkage or process distortion in flex PCB materials. Several areas will offer a tighter resistance within each datum zone or termination area while kicking back the need to keep a tight tolerance of the Flex PCB interface in between various other discontinuation locations.

Nesting and Palletizing

Flex PCB units can be provided in panelized formats. This format will enhance the PCB manufacturing and assembly process performance and making best use of material use. Automated taking care of for in-line PCB assembly processing for Flex PCB furnished with a provisional rigid backing and multilayer Rigid Flex PCB requires a rather uniform board summary.

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