Flex and Rigid Flex PCB Design Principles
[headline] Flex and Rigid Flex PCB Design Principles [/headline]
The designer is typically under pressure to release the documentation and also get the flexible circuit right into production. There is, nevertheless, a lot in danger. Establishing for medium-to-high volume PCB manufacturing requires considerable physical as well as cashes. To avoid possible warm from administration, the designer needs to demand PCB prototyping the product and also a extensive style evaluation prior to release.
DFM Review Criteria
Comprehensive documentation is essential. The intent is to provide the maker with a detailed list and also description of the materials specified for the flex PCB circuit construction, products stack-up, reinforced/stiffened areas, essential density areas, and to define a solder-compatible surface finish for all element land pattern attributes. For the much more complicated multilayer and Rigid Flex PCBapplications consist of cross-sectional views. Essential bend or radius places must be identified with reference dimensions as well as it will be useful to furnish different sights revealing an set up flex arrangement.
The key referrals for evaluating the Flex PCB are tooling holes as well as fiducial targets. Non-plated tooling openings are generally used for maintaining the position of the circuit throughout singulation and, when backed with or part of a stiff area, PCB assembly processing. Fiducial features need to be provided in each circuit area or local discontinuation location to offer an plain 'datum' reference for more accurate element positioning. The maximum fiducial is a strong filled 0.25 to 0.5 mm (.010" to .020") diameter circle. Cover layer material have to supply sufficient clearance to make certain that it does not overlap into the fiducial target functions throughout the cover layer-to-base circuit lamination process.
Using fiducial attributes is a typical technique for:
• Solder pattern x, y and theta alignment • Precise surface area mount element placement • Reducing the impacts of variable product shrinking problems • Compensation for any type of arbitrary distortions in flex PCB products
PCB Assembly documentation will certainly include a bill of product, approved supplier checklist, component referral designators and any type of unique requirements. Develop clear, in-depth drawings and PCB Assembly directions. This document needs to consist of part lays out and general places. The CAD documents will provide exact part X-Y collaborates and alignment data required for assembly processing. All SMT devices are straightened and also placed into their corresponding land patterns using the body center as a referral point for positioning collaborates. The fiducial targets described above will help in establishing these precise X-Y collaborates for solder printing, element positioning and alignment. With flexibility comes integral dimensional instability relative to hardboards or strong metal objects. When several element mounting websites are divided by excessive distance it is suggested that several fiducial attributes be given. Using several datum features is a typical strategy for minimizing or eliminating the effects of variable shrinkage or process distortion in flex PCB materials. A number of areas will offer a tighter resistance within each information zone or termination area while loosening up the have to keep a limited tolerance of the Flex PCBinterface between various other termination areas.
Nesting and also Palletizing
Flex PCB units can be provided in panelized formats. This format will certainly boost the PCB manufacturing as well as assembly procedure performance and optimizing material application.