It is common to allow zero breaks out of the hole from the internal pad, and on some commercial parts, there is sometimes agreement to allow a 270-degree minimum contact ring. There are also blind vias that connect the outer layer to the adjacent inner layer without going through the circuit. Consider the following points to reduce the risks associated with vias. h = height * Flexible solde-stop may break or peel off after 5-10x bending For dynamic flexible applications, 0.3% of the copper deformation . The most common rigid insulation material is called FR4. |  Created: June 24, 2019 This improves the reliability of the board. This method should be used in cases where the plane functions primarily to control EMI. To learn more about PCB drilling read PCB Drilling Explained: The Dos and the Donts. The printer is one of the most common applications where dynamic flex PCBs are used. The FR4 semi flex PCB can change its shape based on the space limit. Selection Matrix Search All Attributes. Because of these limitations, the bend radius and number of cycles should be carefully monitored. The flexible PCB stackup drawing will give the thickness of each layer including the copper thicknesses of the conductive layers. Static flex ribbon for a medical device, as featured in Electronics Weekly. 9 Chapters - 30 Pages - 40 Minute Read, Basic properties of the dielectric material to be considered, Key considerations for choosing PCB materials, 10 Chapters - 39 Pages - 45 Minute Read. As you place additional features on a flexible design of a printed circuit board, youll need to model your boards mechanical behavior. This is because in these transition areas the board encounters the highest mechanical strain. That is why we have our rigid flex PCB design guidelines to break down the steps of creating a rigid flex PCB and what it all entails. PCB design and layout will also be affected by your planned circuit density and line spacing. PCBs fully assembled in as fast as 5 days. This ensures your design can allow for the necessary number of bends without damaging the copper. With this in mind, we see that the graph says we would use the table for NEC 300.34 after making our determination. Eurocircuits' PCB SEMI-FLEX pool is a service for flex to install printed circuit boards, typically 4 layers and made entirely out of FR4 material. Illustration of Rigid-Flex Circuit Board with Bonded Layers, Illustration of Rigid-Flex Circuit Board with Air Gap Construction. The material should be suitable for the environment and the application in which the flex PCB will operate. It affords them uniqueness as well as a set of advantages over their rigid counterparts. Circuit boards have allowed humanity to step into the modern era. Reduces weight through the elimination of additional wires, cables, and connectors. Rigid AP material was used, allowing for better impedance and reliability. Learn more from our design guide below and start building the best flex and rigid-flex PCBs with Epec today! With the growth in the flex PCB market reaching tens of billions, PCB designers have every incentive to learn as much as they can about both static and dynamic flex PCB design. It must be properly identified early in the design. To successfully design a flexible PCB, it is important for the designers to have a basic understanding of the flex drawing requirements. There are three types of design standards for flexPCBboards: This is also called the stable flex and involves the flex layer to be bent into shape to fit into a design. Get PCB design tips and prototyping advice to build better boards Although copper is ductile, it will work harden when repeatedly placed under stress. Terms & Conditions Phone: (800) 763-7503 Whether you are designing a static or dynamic flex PCB, a thicker overall flexible stackup requires a larger bending radius. Reduced flex thickness is also preferrable to allow for sufficient safety margin and long term reliability. Minimum bend radius: 1-2 layers = 6X 3 plus layers = 12X or greater Dynamic Flex The flex circuit is subjected to constant infinite repetitive bending as part of the operation of the final assembly. Fabricating PCBs. Set the Bend Zone Radius and Bend Angle as required. For a dynamic application, aim for a bend ratio of 20-40:1. . The two predominant reasons for using flex or rigid flex, are to solve a packaging issue or reduce the space and weight of the electronics package. The pads used for your rigid flex PCB should have anchoring spurs, also known as tie-downs. If you want to reduce the overall thickness, there are flexible coverlays available that do not require an adhesive. The use of adhesives with the rigid areas may cause cracks to form in the copper plating within via holes because acrylic adhesives can become soft when heated. The stress data is accurate to more . Best-in-Class PCB Fabrication, Assembly, & Components. Flexible and transparent for advanced creators. Privacy Policy S-parameters Measurement Using a Vector Network Analyzer, Case study: Designing 8 and 14-Layer HDI PCBs with Stacked Vias, IPC Class 2 VS Class 3: The Different Design Rules, UL Certification - Flex & Rigid Flex PCBs. Vias should be tear-dropped. So what are the types of bending forces, and how should you be preparing your flex PCB designs to handle them? The shift in the neutral bending axis will depend on the bending radius. This then puts more compressive shear stress on the traces that lie inside the neutral bending axis. His background in scientific research spans topics in nanoparticle lasers, electronic and optoelectronic semiconductor devices, environmental sensors, and stochastics. Consequently, circuit boards provide the means to use electricity and breathe life into appliances and devices. Get to market faster and spend less time troubleshooting. Its minimum bending radius can be calculated by the following formula: R= (c/2) [ (100-Eb)/Eb]-D where: R=minimum bending radius (unit m), c= copper thickness (unit m) , D = cover film thickness (unit m), EB = allowable deformation of copper skin (measured in percentage) Different types of copper have different deformations of copper skin. Many of the same design considerations for static flex PCBs also apply to dynamic flex PCBs. for flexible printed circuits (FPC) - based on experience This tool helps you to calculate an estimated minimum bending radiuses of flexible printed circuits (FPCs). of Wire (0.902 Inches) x Cable Multiplier of 8X O.D. The conductor pattern should also be analyzed to . The below illustration helps us to understand the concept of the bend radius. In a route part for segments, the software considers the individual minimum bend radius for . Our team of engineers are here to help you with all your product needs. In recent times, they too have undergone quite some change. Flex PCBs are flexible circuits with very thin substrates and high levels of bendability, tensile strength, and physical flexibility. Wider trace widths preferred, if available room allows, as opposed to thicker copper. It also allowed for better impedance and better control around the flex finger area. Stress data for each layer is calculated using predicted cooper elongation. Consequently, when designing for adhesive-based materials, its important to incorporate anchors and teardrops in your design. The allowed bend radius can be calculated in terms of the allowed deformation on the outer edge of the copper conductors in the flex circuit. This allows printed circuit designers to customize their board to odd enclosures, design motion into new devices, and provides unique form factors that are not possible with rigid boards. The tests include quality assurance tests for rigid boards, and a bend test. The material can increase strength, thickness, and rigidity. It is very important to mention the type of plating that your flex PCB requires. When deciding on a shielded material. Topics: Try not to bend at the corners. Click Tools > Options > System Options > Routing and select Create route part for segments if bend radius is less than the minimum. If youre, Advantages of Flexible Circuits for Space Applications. Vias are okay over a stiffener, but vias just off the edge of a stiffener are at risk of cracking. 50 x bend cycles of 0 - 90 - 0 Bend features: 5mm radius / max bending angle 90 Materials: Specialized FR-4 for static flex applications: Copper weights (finished) 35m: Minimum track and gap: 0.075mm / 0.075mm: PCB thickness: 1.00mm - 2.00mm: PCB thickness in flex section: 0.25mm 0.05mm: Maxmimum dimensions: 538mm x 610mm . (Minimum .004" Trace/Space) 2 oz. Sunnyvale, CA 94086, USA. S-parameters Measurement Using a Vector Network Analyzer, Case study: Designing 8 and 14-Layer HDI PCBs with Stacked Vias, IPC Class 2 VS Class 3: The Different Design Rules, UL Certification - Flex & Rigid Flex PCBs. Any flex PCB is related to a rigid-flex PCB in that they use the same materials for the flex layer. The minimum bending radius of a single layer semi flex PCB is 5,0mm. Without the right knowledge to design a rigid flex PCB however, these boards could prove to be a challenge. Designing either type of flex PCB is as much a mechanical exercise as it is an electrical exercise. The flex circuit is bent/creased to the point of a zero bend radius, then installed in the final assembly. Having a radiused corner within and flex bend area reduces / eliminates stress concentrators and improves reliability. Minimum Bend Radius for 500 MCM THHN is the O.D. As the openings in the ground plane, the size will be determined by the requirements for shielding or to control the impedance level. Assembling your boards. Dynamic board: A dynamic board is a flex PCB that is regularly flexed and twisted. At cold temperatures, the material becomes hard and can break. Each manufacturer has his own set of design rules and recommendations. Start with the base copper weight or reduce the dielectric thickness. Get Altium Designer for free for 2 weeks. This should also show which layers are rigid material and which layers are flexible material including copper weights. However, the flexibl area is hollow inside (not laminated). Before selection begins, we need to make sure material characteristics fit your specific board requirements and end application. Flexible and transparent for advanced creators. But if chemicals flew into the hollow part underneath during production, the complete rigid-flexible board is scrap. By doing that every day, and by always making the customer our top priority, we plan on being here for another 70 years and then some. To learn more, call us now at 717-558-5975 or contact us online anytime. Sierra Circuits is a minority-owned business, certified by the The minimum bending radius is usually between 1mm and 5mm. Epec is at the forefront of innovation, with the expertise and agility to move at the speed of todays businesses. The thickness of the flex PCB materials varies between 0.5 and 5mils. For this reason this estimation is given, entirely based on experience. Printers use dynamic flex PCBs as the circuit flexes throughout the operation of the printer. The dynamic bending stress can only be reliably ensured with single- and double-layer flexible printed circuit boards. Layer Stackup Design Implement any kind of layer stack for both rigid and rigid-flex PCBs. This results in an overall reduction in weight which is an important factor in the modern world where lightweight products are preferred over heavier ones. This design involves repetitive bending of the design; therefore, limiting it to two layers is recommended. Since there is no requirement for wiring harnesses the assembly cost is cut down. The flex PCBs offer many advantages for both the physical designer and the manufacturer. Flexible and Rigid-Flex Printed Circuit Boards. The anchoring spurs help to ensure there is no separation between the base material and copper during the assembly. It is generally advised that dynamic flex PCBs not exceed a 90 bend angle. Overview; Product Images; Features and Benefits; . The area of focus is the thickness where flexing or bending will occur; which should be only in a location with conductors and not plated through-holes. In this webinar, we discuss flex PCB design guidelines for manufacturing. Simply put, the thicker the circuit, the less it can flex without damage. Gradually change the width of the traces. The pads should also be filleted as to reduce the stress points, as well as the chance of breakage during flexing. A Bending Line is placed over the flexible region and configured so the board can fold 180 degrees. Kapton and FR4 materials are commonly used for stiffeners and can be attached with thermally-cured acrylic or pressure-sensitive adhesive. Plating the through-holes or vias is a requirement for multilayer PCBs. You must dry your rigid flex PCB (roughly four hours at 120 degrees Celsius) to dry out any moisture absorbed by the polyimide. *Distinguish between dynamic (regular-to-bend) and stable flexion (bend-to-install). The flexibility of a flex PCB is determined by the bend radius of the flex material used. The stiffener is an additional mechanical piece that provides mechanical support to the PCB during the assembly. From the formula above: 10 x 200 microns = 2000m = 2mm. An essential element of a flex or rigid-flex printed circuit board (PCB) design is verification that the construction will meet your mechanical bend requirements. Designing a flex-circuit is only one step away from designing a hardboard. The ground planes must be rastered in the flexible bending area. They offer the best circuit boards to customers at affordable rates because you deserve the best solutions for your electrical designs! Your flex PCB circuits and rigid-flex PCB circuit boards will still have sections built up from common rigid PCB laminates. Hence it is suitable to use this type of material in a system that is exposed to the outside environment. Flex and Rigid-Flex PCB Design Guidelines and Assembly in Altium Designer, Many electronic devices dont live on a single printed circuit board. The amount of flexibility gained will be directly proportional to the percentage of copper removed from the plane.